Hobart 6911-1, 6911A-1, 6911-2, 6911A-2, 6911-3 Operation And Maintenance Manual

OM-2031

080187
Revised 080589
Revised 032293

Revised 100195
Revised 043096

OPERATION AND MAINTENANCE

MANUAL

with

ILLUSTRATED PARTS LIST

for

ENGINE-DRIVEN GENERATOR SET

Series Numbers 6911 and 6911A

MODEL 90 C 20

90-KVA, 400-HZ, 115/200-V AC, 3-PHASE

SPECIFICATION
NUMBER

6911-1, 6911A-1 Trailer or Truck
6911-2, 6911A-2 Trailer or Truck
6911-3, 6911A-3 Tractor
6911A-4

6911A-5*

MOUNTING

Fixed Unit With Fuel
Tank and Batteries

Trailer or Truck 489812A

VOLTAGE REGULATOR
USED

430391C
489812A
489812A

430391C

Hobart Brothers Company

Ground Power Division

Troy, Ohio 45373

U.S.A.

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SAFETY INSTRUCTIONS AND WARNINGS FOR ELECTRICAL POWER EQUIPMENT

WARNING

ELECTRIC SHOCK can KILL. Do not touch live electrical parts.

ELECTRIC ARC FLASH can injure eyes, burn skin, cause equipment damage, and ignite combustible

material. DO NOT use power cables tobreak load and prevent tools from causing short circuits.

IMPROPER PHASE CONNECTION, PARALLELING, OR USE can damage this and attached

equipment.

Important:- Protect all operating personnel. Read, understand, and follow all instructions in

the Operating/Instruction Manual before installing, operating, or servicing the equipment. Keep
the manual available for future use by all operators.

A. GENERAL

Equipment that supplies electrical power can cause serious injury or death, or damage to other equipment
or property. The operator must strictly observe all safety rules and take precautionary actions. Safe practices
have been developed from past experience in the use of power source equipment. While certain practices be­low apply only to electrically-powered equipment, other practices apply to engine-driven equipment, and some
practices to both.

B. SHOCK PREVENTION

Bare conductors, or terminals in the output circuit, or ungrounded, electrically-live equipment can fatally
shock a person. Have a certified electrician verify that the equipment is adequately grounded and learn what
terminals and parts are electrically HOT. Avoid hot spots on machine. Use proper safety clothing, procedures,
and test equipment.

The electrical resistance of the body is decreased when wet, permitting dangerous currents to flow
through it. When inspecting or servicing equipment, do not work in damp areas. Stand on a dry rubber mat
or dry wood, use insulating gloves when dampness or sweat cannot be avoided. Keep clothing dry, and
never work alone

1. Installation and Grounding of Electrically Powered Equipment

Equipment driven by electric motors (rather than by diesel or gasoline engines) must be installed and
maintained in accordance with the National Electrical Code, ANSI/NFPA 70, or other applicable codes. A
power disconnect switch or circuit breaker must be located at the equipment. Check the nameplate for volt­age, frequency, and phase requirements. If only 3-phase power is available, connect any single-phase rated
equipment to only two wires of the 3-phase line. DO NOT CONNECT the equipment grounding conductor
(lead) to the third live wire of the 3-phase line, as this makes the equipment frame electrically HOT, which can
cause a fatal shock.

Always connect the grounding lead, if supplied in a power line cable, to the grounded switch box or build­ing ground. If not provided, use a separate grounding lead. Ensure that the current (amperage) capacity of
the grounding lead will be adequate for the worst fault current situation. Refer to the National Electrical Code
ANSI/NFPA 70 for details. Do not remove plug ground prongs. Use correctly mating receptacles.

2. Output Cables and Terminals

Inspect cables frequently for damage to the insulation and the connectors. Replace or repair cracked or
worn cables immediately. Do not overload cables. Do not touch output terminal while equipment is energized.

3. Service and Maintenance

This equipment must be maintained in good electrical and mechanical condition to avoid hazards stem­ming from disrepair. Report any equipment defect or safety hazard to the supervisor and discontinue use of
the equipment until its safety has been assured. Repairs should be made by qualified personnel only.

Before inspecting or servicing electrically-powered equipment, take the following precautions:

a. Shut OFF all power at the disconnecting switch or line breaker before inspecting or servicing the
equipment.

b. Lock switch OPEN (or remove line fuses) so that power cannot be turned on accidentally.
c. Disconnect power to equipment if it is out of service.
d. If troubleshooting must be done with the unit energized, have another person present who is trained in

turning off the equipment and providing or calling for first aid.

C . FIRE AND EXPLOSION PREVENTION

Fire and explosion are caused by electrical short circuits, combustible material near engine exhaust pip­ing, misuse of batteries and fuel, or unsafe operating or fueling conditions.

1. Electrical Short Circuits and Overloads

Overloaded or shorted equipment can become hot enough to cause fires by self destruction or by causing
nearby combustibles to ignite. For electrically-powered equipment, provide primary input protection to remove
short circuited or heavily overloaded equipment from the line.

2. Batteries

Batteries may explode and/or give off flammable hydrogen gas. Acid and arcing from a ruptured battery
can cause fires and additional failures. When servicing,do not smoke, cause sparking, or use open flame
near the battery.

3. Engine Fuel

Use only approved fuel container or fueling system. Fires and explosions can occur if the fuel tank is not
grounded prior to or during fuel transfer. Shut unit DOWN before removing fuel tank cap. DO NOT com­pletely fill tank, because heat from the equipment may cause fuel expansion overflow. Remove all spilled fuel
IMMEDIATELY, including any that penetrates the unit. After clean-up, open equipment doors and blow fumes
away with compressed air.

D. TOXIC FUME PREVENTION

Carbon monoxide - Engine exhaust fumes can kill and cause health problems. Pipe or vent the exhaust
fumes to a suitable exhaust duct or outdoors. Never locate engine exhausts near intake ducts of air condition­ers.

E. BODILY INJURY PREVENTION

Serious injury can result from contact with fans inside some equipment. Shut DOWN such equipment for
inspection and routine maintenance. When equipment is in operation, use extreme care in doing necessary
trouble-shooting and adjustment. Do not remove guards while equipment is operating.

F. MEDICAL AND FIRST AID TREATMENT

First aid facilities and a qualified first aid person should be available for each shift for immediate treat­ment of all injury victims. Electric shock victims should be checked by a physician and taken to a hospital im­mediately if any abnormal signs are observed.

EMERGENCY FIRST AID

Call physician immediately. Seek additional assistance. Use First Aid techniques recommended
by American Red Cross until medical help arrives.

IF BREATHING IS DIFFICULT, give oxygen, if available, and have victim lie down. FOR ELECTRI­CAL SHOCK, turn off power. Remove victim; if not breathing, begin artificial respiration, preferably
mouth-to-mouth. If no detectable pulse, begin external heart massage. CALL EMERGENCY RESCUE
SQUAD IMMEDIATELY.

G. EQUIPMENT PRECAUTIONARY LABELS

Inspect all precautionary labels on the equipment monthly. Order and inspect all labels that cannot be
easily read.

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Table of Contents

SUBJECT CHAPTER/SECTION PAGE

WARNING
LIST OF EFFECTIVE PAGES
INTRODUCTION

CHAPTER 1. DESCRIPTION/OPERATION

SECTION 1. DESCRIPTION 1-1 1

1. General 1-1 1

2. Orientation 1-1 1

3. Special Features 1-1 1

A.Protective Monitor 1-1 3
B.Pull-out Trays 1-1 3
C.Voltage Regulator 1-1 3
D.Test Circuitry 1-1 3
E.Electric Governor 1-1 3
F. “ROLL-OUT” FEATURE
(TOW TRACTOR-MOUNTED UNIT) 1-1 3

4. Identification 1-1 5

A. General 1-1 5
B. Generator Sets Available in 6911 Series. 1-1 5

5. Optional Equipment 1-1 6

A. Trailer 1-1 6
B. Transformer-Rectifier 1-1 6
C. Truck 1-1 6
D. Second Output and Control Box 1-1 6
E. Quick Start Kit 1-1 6

6. Canopy 1-1 6

7. Engine, Generator, and Controls

Assembly 1-1 7

A. Basic Engine 1-1 7
B. Engine Manufacturer’s Equipment 1-1 7
C. Hobart Engine Equipment 1-1 9

(1) Electric governor system 1-1 9

(a) Magnetic pickup 1-1 9
(b) Control unit 1-1 9
(c) Actuator 1-1 9

(2) Engine electrical system 1-1 9
(3) Engine protective devices 1-1 9
(4) Air cleaner 1-1 10
(5) Exhaust system 1-1 12
(6) Radiator 1-1 12

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SUBJECT CHAPTER/SECTION PAGE

D. Generator 1-1 13
E. Control Box Assembly 1-1 13

(1) Generator control tray 1-1 13

(a) Resistors 1-1 13
(b) Generator output monitors (meters) 1-1 14
(c) Meter and line switches 1-1 15
(d) Receptacle connector 1-1 15
(e) Tray 1-1 15
(f) Manual voltage control 1-1 15
(g) Excitation-deenergization relay 1-1 15

(2) Protective relay tray 1-1 15

(a) Sensing modules 1-1 17
(b) Memory and time delay module 1-1 17
(c) Indicating lights 1-1 18
(d) Plug-interlock relay 1-1 18
(e) Test-bank switch 1-1 18
(f) Resistor 1-1 18
(g) Fuse-interlock relay 1-1 18
(h) Connector 1-1 20
(k) Auxiliary underfrequency relay 1-1 20

F. Engine Control Panel 1-1 20

(1) Engine instruments 1-1 20
(2) Engine and generator controls 1-1 21
(3) Air cleaner indicator 1-1 22
(4) Test receptacle connector 1-1 22

G. Voltage Regulator 1-1 24
H. Power Module Panel Assembly 1-1 24

(1) Load contactor 1-1 24
(2) Current transformers 1-1 24
(3) Overload module 1-1 25
(4) Rectifier 1-1 25
(5) Terminal boards 1-1 25

8. Test Box 1-1 27

A. Description 1-1 27
B. Theory of Operation 1-1 28

SECTION 2. PREPARATION FOR USE,

STORAGE, OR SHIPPING 1-2 1

1. Preparation for Use 1-2 1

A. General 1-2 1

B. Inspection/Check 1-2 1

(a) Fuel 1-2 1
(b) Engine coolant 1-2 2
(c) Engine lubricating oil 1-2 2

C. Installing Output Cables 1-2 2
Units are generally shipped without generator

set-to-aircraft cables. 1-2 2

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SUBJECT CHAPTER/SECTION PAGE

2. Preparation for Storage 1-2 4

A. General 1-2 4
B. Temporary Storage 1-2 5
C. Long Time Storage (Over 30 Days) 1-2 5

3. Preparation for Shipment
(Tractor-Mounted Units Only) 1-2 6

SECTION 3. OPERATION 1-3 1

1.General 1-3 1

2. Operating the Generator Set 1-3 1

A. Pre-start Inspection 1-3 1
B. Normal Engine Starting Procedures 1-3 1
C. Cold Weather Engine Starting Procedures 1-3 4
D. Preparation for Power Delivery 1-3 5
E. Power Delivery 1-3 6
F. Preparation for Power Delivery

(Manual Voltage Control) 1-3 6
G. Power Delivery (Manual Voltage Control) 1-3 7
H. Discontinue Power Delivery 1-3 7
K. Stopping the Engine 1-3 7

3. Test Box Operation 1-3 8

4. Transformer-Rectifier Operation 1-3 9

A. Direct Current Power Delivery 1-3 9
B. Simultaneous 28.5-V DC and 115-V AC

Power Delivery 1-3 10

6. Trailer Operation 1-3 11

A. Towing 1-3 11
B. Parking 1-3 11

CHAPTER 2. SERVICE

SECTION 1. MAINTENANCE 2-1 1

1. General 2-1 1

2. Operation of Roll-Out Feature
(For Tractor-Mounted Units Only) 2-1 1

A. Roll Generator-Set Out for Service 2-1 1
B. Roll Generator-Set In to Normal Position 2-1 1

3. Inspection 2-1 1

4. Lubrication 2-1 3

A. General 2-1 3
B. Generator 2-1 3
C. Generator Controls 2-1 3

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SUBJECT CHAPTER/SECTION PAGE

D. Engine 2-1 3

(1) Lubrication schedule 2-1 3
(2) Oil specification 2-1 3
(3) Oil viscosity 2-1 3
(4) Changing engine oil 2-1 4
(5) Changing engine oil filter 2-1 4

E. Starter 2-1 4

5. Air Cleaner Service 2-1 5

A. Cartridge Removal 2-1 5
B. Cartridge Installation 2-1 5

6. Engine Fuel 2-1 6

A. Quality 2-1 6
B. Fuel Filter 2-1 6

7. Engine Cooling System 2-1 6

A. General 2-1 6
B. Radiator Cap 2-1 6

(1) General 2-1 6
(2) Removal 2-1 6
(3) Installation 2-1 7

C. Warm Weather Operation 2-1 7
D. Cold Weather Operation 2-1 7

(1) General 2-1 7
(2) Checking coolant solution 2-1 7
(3) Preparing the coolant solution 2-1 7
(4) Installing the antifreeze solution 2-1 7

E. Draining the Cooling System 2-1 8
F. Cleaning the Cooling System 2-1 8
G. Cleaning the Radiator Core 2-1 9
H. Filling the Cooling System 2-1 9

8. Generator Maintenance 2-1 9

A. Cleaning 2-1 9
B. Adjustment 2-1 10

9. Drive Belts 2-1 10

A. Checking Belt Tension 2-1 10
B. Belt Adjustment 2-1 10

10. Trailer, Truck and Battery Maintenance 2-1 10

11. Service Helps 2-1 10

A. Wiring 2-1 10
B.Control Box Trays 2-1 10
C. Generator Exciter 2-1 11
D. Engine Control Panel 2-1 12

SECTION 2. INSPECTION/CHECK 2-2 1

1. General 2-2 1

2. Engine 2-2 1

A. Fuel (See Fig. 1 for time schedules) 2-2 1
B. Lubrication 2-2 1

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SUBJECT CHAPTER/SECTION PAGE

C. Coolant 2-2 1
D. V-Belts 2-2 1
E. Exhaust System 2-2 1

3.Electrical System (12-V DC) 2-2 3

A. Lights 2-2 3
B. Fuses 2-2 3
C. Wiring and Connections 2-2 3

4. Electrical System (115-V AC) 2-2 4

A. Monitoring Instruments 2-2 4
B. Indicating Lights 2-2 4
C. Protective Modules 2-2 4
D. Wiring and Connections 2-2 4

5. Trailer and Truck 2-2 5

SECTION 3. ADJUSTMENT/TEST 2-3 1

1. General 2-3 1

2. Generator Set Test 2-3 1

A. Pre-operational Test Procedures 2-3 1
B. Operational Test Procedures 2-3 5

3. Generator Set Adjustment 2-3 10

A. Generator Adjustment 2-3 10
B. Generator Control Adjustments 2-3 10
C. Basic Engine Adjustments 2-3 10
D. Engine Accessories Adjustment 2-3 10
E. Electric Governor System Adjustment 2-3 11

(1) Actuator linkage adjustment 2-3 11
(2) Magnetic pickup adjustment 2-3 12
(3) Adjustment and Test of Controller and Actuator 2-3 14
(4) Checking Magnetic Pick-up signal 2-3 16

5. Generator and Exciter Test 2-3 16

6. Diode Test 2-3 17

A. Disconnect diode lead(s). 2-3 17

CHAPTER 3. TROUBLESHOOTING

SECTION 1. TROUBLE SHOOTING

PROCEDURES 3-1 1

1. General 3-1 1

2. Trouble Shooting Chart 3-1 1

3. Equipment for Troubleshooting 3-1 2

4. Safety 3-1 2

5. Parts Replacement 3-1 2

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SUBJECT CHAPTER/SECTION PAGE

6. Test Values 3-1 3

7. Checking Connections and Leads 3-1 3

8. Electric Governor Trouble Shooting 3-1 3

9. Engine Trouble Shooting Procedures 3-1 4

A. General 3-1 4

CHAPTER 4. ILLUSTRATED PARTS LIST

SECTION 1. INTRODUCTION 4-1 1

1. General 4-1 1

2. Purpose 4-1 1

3. Arrangement 4-1 1

4. Explanation of Parts List 4-1 1

A. Contents 4-1 1
B. Parts List Form 4-1 1

SECTION 2. MANUFACTURER’S CODES 4-2 1

1. Explanation of Manufacturer’s (Vendor)

Code List 4-2 1

SECTION 3. PARTS LIST 4-3 1

1. Explanation of Parts List Arrangement 4-3 1

2. Symbols and Abbreviations 4-3 1

SECTION 4. NUMERICAL INDEX 4-4 1

1. Explanation of Numerical Index 4-4 1

CHAPTER 5. OPTIONAL EQUIPMENT
CHAPTER 6. MANUFACTURER’S LITERATURE
UNUSUAL SERVICE CONDITIONS

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INTRODUCTION
This manual contains operation and maintenance information for a series of 400-Hertz generator sets

manufactured by Hobart Brothers Company, Power Systems Group, Troy, Ohio 45373.
This manual is not intended to be a textbook on electricity or electronics. Its primary purpose is to provide

information and instructions to experienced operators, electricians, and mechanics who have never seen or
operated this equipment. It is the intent of this manual to guide and assist operators and maintenance people
in the proper use and care of the equipment.

Use of the manual should not be put off until a trouble or need for help develops. Read the instructions before
starting the unit. Learn to use the manual and to locate information contained in it. Its style and arrangement
are very similar to commercial aircraft manuals. The manual is divided into six chapters. Each chapter is
divided into as many sections as required. Each new section starts with page 1. Each page is identified by
chapter, section and page number, which are located in the lower, outside corner. When information located
in another portion of the manual is referred to, its location is identified by a chapter, section, and paragraph, or
figure number. For example, “

(See 2-3, Para. B)”

refers to information located in Chapter 2, Section 3,
Paragraph B. If a Chapter and Section are not indicated in a reference, the referenced material is located in
the same section as the reference, Example,

(See Para. B).

In addition to operation and maintenance instructions, the manual contains an illustrated parts list in Chapter
4, and a collection of manufacturer’s literature and supplemental information in Chapter 6.

Content of the manual is arranged as follows:

Chapter 1. Description/Operation
Chapter 2. Servicing
Chapter 3. Troubleshooting
Chapter 4. Illustrated Parts List
Chapter 5. Optional Equipment
Chapter 6. Manufacturer’s Literature

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Introduction August 5/89 Revised
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CHAPTER 1. DESCRIPTION/OPERATION

SECTION 1. DESCRIPTION

1. General

The generator sets
The various configurations of the set are identified by adding a dash number
Series number.

The generator sets in the 6911 series feature armatures with Hoover Bearings, Browning Coupler,
and different magnetic pole construction for the generator revolving field. This new armature can be
easily identified by the two copper rings on each end of the field coils and copper wedges between
the magnetic poles.

Series 6911A generator sets feature the same magnetic pole construction for the generator revolving
field as Series 6911 generator sets. In addition, Series 6911A generator sets also feature wide-type
Fafnir bearings on the generator.

The basic generator set which includes the engine, generator and all controls is identical for all mod­els. Differences between models are those required by their respective mounting, such as trailer
mounting, tow tractor mounting, etc. Identification of different models within the Series will be ex­plained later in the Description.

Information and instructions throughout the manual apply to all models. Information which applies only
to a certain model will be qualified and identified as such.

The purpose of the generator set is to generate and deliver regulated, 400-Hz electrical power to a
parked
ators are not running. The engine, generator, and controls are designed into a compact unit which is
easily removable from a tow tractor. See Figure 2 for specifications and capabilities.

(or towed)

(see Fig. 1)

aircraft for operation of the aircraft’s electrical equipment when the on-board gener-

covered by the manual are identified by Series No. 6911 & 6911A.

(-1, -2, etc.)

suffix to the

2. Orientation

For purpose of orientation and to familiarize operators and maintenance personnel with the location of
components, the radiator is considered to be at the FRONT of the unit. The generator and controls
are at the REAR.

RIGHT and LEFT are determined by standing at the rear end facing the machine. Thus, the generator
control box, output receptacle connector, and engine control panel are mounted on the LEFT side at
the REAR of the unit.

3. Special Features

The generator set has many special features which are later described more fully under the assem­blies in which they appear. Some of the main features are mentioned here and described briefly.

April 30/96 Revised 1-1

Page 1

OM-2031

1. Canopy 6.Output cable horn

2. Access-vent covers 7. Mounting frame

3. Lifting eye 8. Engine fan exhaust deflectors

4. Windows 9. Engine exhaust pipe

5. Output receptacle cover 10. Radiator cap access cover

Generator Set

Figure 1

1-1 April 30/96 Revised
Page 2

A. Protective Monitor

OM-2031

A single, solid-state device
erator output circuit and functions to cause the load to be disconnected from the generator if an
abnormal condition of voltage, frequency, or load develops.

B. Pull-out Trays

The control box is equipped with pull-out, drawer-type trays
controls and equipment mounted in them. Each tray may be removed as an assembly by discon­necting a single quick-disconnect connector and tripping two safety latches.

C. Voltage Regulator

A solid-state

(used on 6911-2, 6911-3, 6911A-2, 6911A-3 units),

(See OM-2020 in Chapter 6)

panel when applicable). The regulator is also adjustable for a variety of output cable sizes and
lengths.A magamp type voltage regulator is used on Specs. 6911-1, 6911A-1, 6911A-4 units

(4, Fig. 8)

provides automatic voltage regulation at the aircraft (or distribution

receives signals from all of the fault sensing units in the gen-

(Fig. 6)

which provide easy access to

adjustable voltage regulator

(See TM-759 in Chapter 6).

D. Test Circuitry

A receptacle connector
cuitry is provided for the attachment of a test box manufactured by Hobart Brothers. This test cir­cuitry allows electricians to perform as many as twenty-four tests and checks from one location,
conveniently and easily.

(19, Fig. 9)

with wiring to various test points throughout the electrical cir-

E.E lectric Governor

The engine is equipped with an all electric type governor kit
equipment more fully described under the engine description.

F. “ROLL-OUT” FEATURE (TOW TRACTOR-MOUNTED UNIT)

For a generator set mounted on a tow tractor
two-channel-like tracks which are floor mounted in the generator compartment of the tow tractor.
Tracks are equipped with cam-follower, needle-bearing rollers which support the generator set
and allow it to roll in-and-out easily for servicing and maintenance. Additional rollers are mounted
on each side of the generator set main frame, near the rear, to add stability and to prevent the
unit from tipping downward at the front when it is rolled outward for service.

(Spec. 6911-2)

(5 and 12, Fig. 3)

the generator set is supplied with

and other special

(See Figure 21, Sec-

tion 4-3).

April 30/96 Revised 1-1

Page 3

OM-2031

Length overall 82 inches (2082.8 mm)
Width 36 inches (914.4 mm)
Height overall 43 inches (1092.2 mm)
Weight 3050 pounds (1383.2 kg)

Length overall 100 inches (2540 mm)
Width 78 inches (1981.2 mm)
Height overall 72 inches (1828.8 mm)
Weight 4950 pounds (2244.9 kg)

Output power rating 90 kVA
Output Voltage 115/200-V

PHYSICAL

BASIC UNIT

TRAILER-MOUNTED UNIT

GENERATOR

Rated load capacity 260-A
Frequency (cycles per second) 400-Hz
Output kilowatts 72-kW
Power factor 0.8 PF
Duty cycle 100%
Operating speed at 400-Hz 2000 RPM
Overload Capacity

(125 % of rated lad capacity

325 A

GENERATOR PROTECTIVE SYSTEM

Overvoltage relay trips 130-V to 134-V; resets 125-V
Undervoltage relay trips 102-V or below; resets 110-V
Overfrequency relay trips 415-Hz to 425-Hz; resets 410-Hz
Underfrequency relay trips 375-Hz to 385-Hz; resets 385-Hz
Overload relay trips at 112-kVA in less than 5 minutes
Undervoltage time delay relay trips 4 to 12 seconds

1-1 April 30/96 Revised
Page 4

Specifications and Capabilities

Figure 2 (Sheet 1 of 2)

OM-2031

Engine
Manufacturer Cummins
Model 6BTA5.9
Type Turbocharged, in-line, 6-cylinder, 4-cycle diesel
Displacement 359 cu. in. (5.8 liters)
Compression ratio 16.5:1
Firing order 1-5-3-6-2-4
Number of Main bearings 7
Horsepower at 2000 RPM 167
Governed speed 2000 RPM +/- 4.5%
Idle Speed 850 RPM +/- 25 RPM
Electrical System 12-volt
Oil capacity (with filter) 17.3 quarts (16.4 liters)
Oil capacity (without filter) 16.3 quarts (13.6 liters)
Coolant capacity 15.3 quarts (14.5 liters)
Fuel Diesel oil conforming to ASTM Spec.

D.975-66T, Nos. 1-D and 2-DD

Lube oil MIL-L-2104C or MIL-L-2104D

Specifications and Capabilities

Figure 2 (Sheet 2 of 2)

4. Identification

A. General

Generator sets are identifaied by their Specification numbers which consist of the Series number
plus a dash number (i.e. -1,-2, etc.) suffix. The suffix number indicates the mounting design of
the generator set. For example, Specification No. 6911 identifies a machine designed for mount­ing on a trailer or truck.

B. Generator Sets Available in 6911 and 6911A Series

The following identification chart lists machines currently available in each series.

SPECIFICATION

NUMBER

6911-1, 6911A-1 Trailer or Truck 430391C

MOUNTING VOLTAGE

REGULATOR

USED

6911-2, 6911A-2 Trailer or Truck 489812A
6911-3, 6911A-3 Tractor 489812A
6911A-4 Fixed, Fuel Tank and Batteries 430391C
6911A-5* Trailer or Truck 489812A

April 30/96 Revised 1-1

Page 5

OM-2031

5. Optional Equipment

Several items of optional equipment are available for the 6911 Series unit. Each piece of optional
equipment is covered by its own Instruction and Parts Manual and will not be covered in this basic
manual. When applicable, information for optional equipment will be located in Chapter 5.

Options are listed as follows:
A. Trailer

A four-wheel trailer with batteries and fuel tank is available.

B. Transformer-Rectifier

A transformer-rectifier
V, 400-Hz, AC power from the generator and converts it to a 28.5 V DC output.

C. Truck

Trucks with special bodies for mounting the generator set are available. Compartments in the
body are provided for batteries, cable-storage, etc. Trucks available are Ford, Chevrolet, and
GMC.

D. Second Output and Control Box

An auxiliary output and control box is available to provide a second independent 115-V AC output
circuit.

E. Quick Start Kit

(See Section 1-3, Para. 2C)

(T-R)

is available for use with the generator set. This T-R receives 115/200-

6. Canopy

A sheet metal enclosure, identified as a canopy
ator and electrical controls.

The canopy is designed to reduce the operational noise level in the immediate area of the machine.
Doors and panels are covered on the inside with Fiberglass acoustic material to reduce reflected and
conducted noise, and to absorb noise. Noise producing vibration in most frequently used doors on the
left side is reduced by the use of two-point slam locks. Less frequently used doors on the right side
are equipped with screw-operated latch fasteners which are tightened after latching to reduce vibra­tion. Insulating strips around all doors also reduce noise. Metal strips are mounted horizontally across
the front grille to deflect engine fan exhaust air and noise upward.

(1, Fig. 1),

provides protection for the engine, gener-

Two large openings in the canopy top provide an entrance for cooling air and an access to internal
components. A hood-type cover is mounted about two inches above each opening. The cover is
flanged downward and extends beyond the edges of the upwardly flanged opening to prevent en­trance of blowing rain while still allowing a good flow of air. Air enters the forward opening into the en­gine compartment and is discharged through the radiator by the engine fan. Air enters the rear
opening into the generator compartment. It is then circulated over generator controls and drawn into
the rear exciter and generator housings where it passes over all windings before being discharged by
the generator fan.

1-1 April 30/96 Revised
Page 6

OM-2031

This generator set is equipped with a canopy having doors on both sides. Panel mounted instruments
may be observed through two Plexiglass windows in the left rear door which covers the control box
and engine control panel. T he lower window is slanted outward at the bottom to provide access to en­gine controls when the door is closed. A centrally-located lifting eye attached to a lifting yoke extends
through the canopy top to provide an attaching point for chains, cables, or hook used to lift and move
the generator set.

7. Engine, Generator, and Controls Assembly

This assembly is the basic generator set without canopy. It includes all components required to gener­ate and regulate 400 Hz, 115/200 V, three phase power, and is operable when provided with fuel and
12 V DC power. The engine-generator assembly is mounted on a welded steel frame. A superstruc­ture, attached to the main frame, provides mounting facilities for the canopy, control box, and electri­cal equipment and controls.

A. Basic Engine

This generator set is equipped with a 6-cylinder, in-line, turbo-charged Cummins Diesel engine. See
Figure 2 for general specifications, and see Engine Operator’s Handbook in Chapter 6 for more de­tailed information.

B. Engine Manufacturer’s Equipment

As received from the engine manufacturer, the engine includes the following equipment which is
described in the Cummins Shop Manual

(1) Electronic stop control.
(2) Fuel filter.
(3) Reverse-flow, engine cooling fan to blow air outward through the radiator.

(Chapter 6)

.

April 30/96 Revised 1-1

Page 7

OM-2031

1. Mounting frame 8. Air cleaner 14. Engine control panel

2. Generator 9. Lifting yoke *15. Cable horn and clamp

3. Power module 10. Engine 16. Radiator

4. Control box 11. Engine exhaust pipe *17. Fuel valve solenoid
*5. Governor control box 12. Governor actuator 18. Oil pressure switch
*6. Starting fluid container 13. Output cable terminal 19. Muffler

7. Voltage regulator board

1-1 April 30/96 Revised
Page 8

* NOT ILLUSTRATED

Generator Set Components

Figure 3

C. Hobart Engine Equipment

The engine is modified at Hobart Brothers by the addition of the following equipment:

(1) Electric governor system

An electric governor kit is installed on the engine to replace a conventional, mechanical type.
The electric governor was selected for control of engine speed

quency)

response results in very close frequency control. Refer to the Barber Coleman Handbook in
Chapter 6 for a detailed description. A brief description is given below:

because it provides faster engine response to changes in load conditions. This fast

(and generator output fre-

The governor system consists of the following main components:

Magnetic pickup
Control unit
Actuator

(a) Magnetic pickup

The magnetic pickup is a device for detecting the speed of the engine. It is mounted in
the flywheel housing directly over the ring gear. It produces an AC signal to the control
unit when the ferrous flywheel teeth pass through the magnetic field at the end of the
pickup.

OM-2031

(b) Control unit

The control unit
nents. It receives an AC signal from the magnetic pickup and senses speed changes in
the engine. It provides a voltage signal to the actuator which causes the actuator to move
the fuel control lever as required to maintain a predetermined engine speed. Its power is
received from the 12-V DC battery system.

(c) Actuator

The actuator
required to maintain a constant engine speed. The actuator is operated by a DC signal
from the control unit.

(2) Engine electrical system

Items in the 12-volt engine electrical system that are provided by Hobart Brothers are:

(a) A heavy-duty motor starter
(b) Alternator with voltage regulator
(c) Starting switch

(d) Wiring harness

(3) Engine protective devices

(a) High coolant temperature switch

(5,Fig.3)

(12, Fig. 3)

is a box containing a compact assembly of solid state compo-

supplies the force needed to move and position the fuel lever as

A high coolant temperature switch is mounted in the front of the cylinder block to monitor
the coolant temperature. If the coolant temperature reaches 210 degrees F

, this normally closed switch opens and actuates the fuel valve solenoid which shuts

C)

down the engine.

April 30/96 Revised 1-1

(99 degrees

Page 9

OM-2031

(4) Air cleaner

(b) Oil pressure switch

A diaphragm-type switch monitors the pressure in the lubricating oil system. It is mounted
in the side of the cylinder block

(69 kPa)

10 psi
the engine.

, this switch opens and actuates the fuel valve solenoid which shuts down

(18, Fig. 3)

. If the pressure in the lube oil system falls to

The diesel-engine air cleaner
eliminator and a service indicator. The indicator functions to signal the operator when the car­tridge needs changing. A red cylindrical “flag”

(1)

ing chamber
pressure. As the cartridge becomes loaded with dirt and air pressure within the cleaner less­ens, the “flag” gradually rises higher in the glass viewing chamber. When the “flag” reaches
the top of the chamber, it locks in that position to warn the operator that the cartridge must be
changed. The “flag” is reset
of the indicator.

when air pressure within the air cleaner housing drops below the outside air

(Fig. 4)

(unlocked)

is a dry-cartridge type. It is equipped with a moisture

(2)

is forced upward in a glass enclosed view-

by pushing the reset button

(3)

located on the bottom

NOTE: Theserviceindicatorismountedontheenginecontrolpanelandconnectedtotheaircleaner
by a rubber hose. The indicator flag is visible only when the engine is running, or when the flag is
locked in WARNING position.

1-1 April 30/96 Revised
Page 10

OM-2031

April 30/96 Revised 1-1

1. Viewing chamber

2. Indicating “flag”

3. Reset button

Air Cleaner and Service Indicator

Figure 4

Page 11

OM-2031

(5) Exhaust system

The exhaust system consists of a special noise reducing muffler

(2)

nected by a pipe
rect exhaust and noise downward.

(6) Radiator

The radiator
assembly for cleaning and repair.

(16, Fig. 3)

to a conventional exhaust manifold

is a tube-type with bolted-on, top and bottom tanks which permit dis-

(3, Fig. 5)

(1).

Baffles in the tail pipe outlet di-

which is con-

1-1 April 30/96 Revised
Page 12

1. Exhaust Manifold

2. Exhaust Pipe

3. Muffler

Exhaust System

Figure 5

OM-2031

D. Generator

The 400-Hz generator is a brushless, revolving field, three-phase, alternating current type. The ro­tor assembly is mounted by two, permanently lubricated, sealed, ball bearings. The front bearing
is supported by the fan housing; the rear bearing is mounted in the exciter housing. Both of these
housings are attached to the main generator stator housing. The front end of the rotor shaft ex­tends forward beyond the rear bearing and into the exciter stator housing. The exciter rotor is
mounted on this shaft extension with a Woodruff key and is secured by a washer and 1/2"-13 thd,
cap screw. A rectifier with six diodes is mounted on the exciter rotor and converts exciter AC out­put to DC for excitation of the generator revolving fields. The exciter DC output to the generator
fields, and consequently the generator output, is controlled by the amount of DC voltage supplied
to exciter fields by the static voltage regulator. A centrifugal, radial-blade fan which is part of the
hub and coupling assembly, draws cooling air over all internal windings. Air enters at the exciter
end and is discharged at the drive end. The complete generator is bolted to the engine flywheel
housing.

E. Control Box Assembly

The control box
for generator and engine controls and monitoring equipment. The box is equipped with two,
drawer type trays which contain generator output control devices and monitoring instruments.
Trays slide in and out on nylon rollers for easy access to internally mounted components. Each
tray is easily removable by disconnecting an “Amphenol” connector, unlocking safety latches, and
sliding the complete tray assembly out of the control box.

A shielded, instrument panel light is mounted on the left side of the control box front panel, to illu­minate controls and instruments in the trays.

(1) Generator control tray (See Figure 7)

The generator control tray contains instruments and controls for monitoring and controlling
the generator output.

(a) Resistors

Two, 10-ohm, 100-watt, ballast resistors
citer DC field circuit.

A variable resistor
rheostat
the voltage range through which the rheostat can control generator output voltage.

(Fig. 6)

(13)

is a sheet metal enclosure which houses and provides mounting facilities

(2)

are connected in series in the generator ex-

(1)

is connected in series between the manual control rectifier

. Its purpose is to adjust the DC voltage to the rheostat and thus determine

(14)

and

April 30/96 Revised 1-1

Page 13

OM-2031

(b) Generator output monitors (meters)

The generator output is monitored by three instruments; a frequency meter

(9)

, and an ammeter

ter
the frequency of the generator output alternating current in the range of 380 to 420 Hz

(cycles per second)

to-neutral
meter selector switch

scribed below.)

V. The ammeter is also 3-1/2-inch size and is graduated 0 t o 500 A. The amperage value
in each of the three phases may be read on the ammeter by selecting the desired phase
with switch
load current to a lesser value, of definite ratio, which will operate the ammeter movement
without damage. The ammeter dial scale is graduated and numbered so that the pointer
will indicate the true load current value rather than the meter movement current.

1-1 April 30/96 Revised
Page 14

(A-N, B-N and C-N)

The voltmeter has a 3-1/2-inch face and the scale is graduated 0 to 300

(6)

. Three ammeter current transformers

Control Box

Figure 6

(10)

, a voltme-

(7)

. The frequency meter is a resonant-reed type, and indicates

. The voltmeter indicates the generator output voltage in each phase-

or phase-to-phase

(6)

and the line selector switch

(A-B, B-C and C-A)

as selected by the

(5).(These switches will be de-

(Ref.4,Fig.11)

lower the output

OM-2031

(c) Meter and line switches

These switches provide a means of selecting and determining which phase of voltage
and current is indicated on the voltmeter and ammeter and whether the voltage is line-to­neutral or line-to-line. The meter switch
located under the switch knob, is marked and lettered to indicate the three functional posi­tions of the meter switch.
The line switch
line-to-line voltage to the voltmeter. The nameplate is also marked to indicate the position
of this switch.

(d) Receptacle connector

(5)

(When the knob is pointing straight down, the switch is OFF.)

is a two position, toggle switch used to select either line-to-neutral or

(6)

is a four-position, rotary type. A nameplate

(4)

,

An “Amphenol” connector
trol box components.

(e) Tray

The tray
screw fastener

(f) Manual voltage control

When the automatic manual switch
plied to the rectifier
the rectifier is routed to the exciter field through a rheostat
age is thereby manually controlled by adjustment of the rheostat.

(g) Excitation-deenergization relay

The purpose of this relay
citer field only when engine speed is being controlled by the electric governor.

(2) Protective relay tray (see Figure 8)

(15)

slides in and out on nylon rollers. It is secured in place by a twist-lock,

(8)

.

(12)

(14)

rather than to the automatic voltage regulator. The DC output of

(3)

is to allow automatic excitation to be connected to the ex-

provides a means of quickly disconnecting all wires to con-

(11)

is placed in MANUAL position, AC power is sup-

(13)

. The generator output volt-

The bottom tray in the control box is identified as the protective relay tray and contains electri­cal and safety devices designed to protect the aircraft electrical system against damage
which could result from overvoltage, undervoltage, overfrequency, or underfrequency. The
tray also contains devices for the protection and control of the generator output electrical sys­tem.

April 30/96 Revised 1-1

Page 15

OM-2031

1. Resistor (50 ohm, 100 watt) 9. Voltmeter

2. Resistor (25 ohm, 100 watt) 10. Frequency meter

3. Excitation-deenergization relay 11. Automatic-manual switch

4. Instruction plate 12. Receptacle connector

5. Line selector toggle switch 13. Manual voltage control rheostat

6. Meter selector rotary switch 14. Manual control rectifier

7. AC ammeter 15. Tray

8. Tray fastener

1-1 April 30/96 Revised
Page 16

Generator Control Tray

Figure 7

(a) Sensing modules

OM-2031

The voltage sensing module
erator output leads between the generator and load contactor. These solid-state modules
sense any abnormal condition of voltage or frequency and signal the solid-state circuitry
of the memory and time delay module
put to the aircraft. Trip values are adjustable, however, adjustments should be made
ONLY under laboratory conditions.

A solid-state overload signaling device
monitor module and performs a function similar to the voltage and frequency sensing
modules.

(5)

and frequency sensing module

(4)

to open the load contactor and disconnect out-

(Ref. 7, Fig 11)

(6)

are connected to gen-

is also connected to the protective

Trip values for protective circuits are as follows:

Overvoltage trips at 130 V to 134 V
Undervoltage trips at 102 V or below
Overfrequency trips at 415 Hz to 425 Hz
Underfrequency trips at 390 Hz to 395 Hz
Undervoltage time delay
Overload circuit trips at any value over 125% rated load capacity.

See Para 6,H, (3) for more specific and detailed information regarding overload device.

(b) Memory and time delay module

(adjustable)

The memory and time delay module
ule. It is a solid-state device with a hermetically-sealed, reed-type relay. The printed cir­cuit board or “card” includes five memory circuits and a time delay circuit. Each circuit is
connected to a corresponding sensing circuit in the sensing modules
ory circuits are connected to the module relay coil, and any one of the circuits can ener­gize the coil to open the relay contacts. Thus, when a sensing device energizes any one
of the module circuits, the module relay is also energized to break the load contactor hold­ing circuit and allow the load contactor to open. All circuits, except the undervoltage cir­cuit, function immediately to open the load contactor. A time delay system is designed
into the undervoltage circuit to prevent nuisance opening of the contactor under condi­tions of momentary undervoltage in the generator output. An undervoltage condition
which continues uninterrupted for a period of 4 to 12 seconds
time delay circuit to open the load contactor. Each of the five circuits is connected to a
corresponding indicating light
curs.

The module relay will remain energized
set switch
to normal, CLOSED position.

(7)

is pushed to break the module 12-V DC circuit, and allow the relay to return

(4)

is sometimes called the protective monitor mod-

(10, 11, 13, 14 and 15)

(OPEN)

and the light will remain ON until the re-

(5 and 6)

(adjustable)

whichisturnedonwhenafaultoc-

. All mem-

will cause the

April 30/96 Revised 1-1

Page 17

OM-2031

(c) Indicating lights

The function of these lights
normal condition of overvoltage, underfrequency, etc., which caused the protective moni­tor system to function. Each of the five lights is connected to an actuating circuit within
the memory and time delay module. When one of the circuits is activated, it turns on the
applicable indicating light. The light will remain on until the reset switch
lamps in indicating lights may be tested by pressing switch

(d) Plug-interlock relay

The function of the plug interlock relay
the event the cable plug connector becomes accidentally disconnected from the aircraft
during power delivery, or if an attempt is made to deliver power when the output cable is
not connected to the aircraft. Twenty-eight-volt, direct current for operation of the relay is
supplied from the aircraft either through an on-board transformer rectifier, or from a
twenty-eight-volt, electrical system. Connection from the aircraft to the interlock relay is
made through terminals E and F on the output cable plug connector.

(e) Test-bank switch

A spst, toggle switch
supplying power to a load bank or to an aircraft not equipped with a plug interlock system.

(f) Resistor

(10, 11, 13, 14 and 15)

(1)

is to cause the output load contactor to open in

(18)

provides a means of by-passing the interlock relay

is to indicate, to the operator, the ab-

(8)

.

(7)

is pushed. All

(1)

when

A 100-ohm, 25-watt resistor
tect the relay in the event that phase C contacts in the load contactor should fail to close
when the generator ON switch is operated.

(g) Fuse-interlock relay

The function of the fuse-interlock relay
cuit and remove the load in case of a “blown” fuse

(21)

is connected in series with the plug interlock relay to pro-

(2)

is to interrupt the load contactor holding coil cir-

(17)

in the protective relay coil circuit.

1-1 April 30/96 Revised
Page 18

OM-2031

1. Plug-interlock relay 12. Tray fastener

2. Fuse-interlock relay 13. Overfrequency indicating light

3. Auxiliary underfrequency 14. Undervoltage indicating light
relay 15. Overvoltage indicating light

4. Memory and time delay module 16. Load contactor circuit fuse

5. Over-undervoltage module (2 A)

6. Over-underfrequency module 17. Protective system fuse (2 A)

7. Reset switch 18. Test bank switch

8. Light test switch 19. Receptacle connector

9. Hole plug 20. Terminal board

10. Overload indicating light 21. Resistor (100 ohm, 25 watt)

11. Underfrequency indicating 22. Tray
light

Protective Relay Tray

Figure 8

April 30/96 Revised 1-1

Page 19

OM-2031

(h) Connector

A twenty-six contact connector
the tray electrical components so that the complete tray assembly may be removed
quickly and easily.

(k) Auxiliary underfrequency relay

The function of the auxiliary underfrequency relay
tion-deenergization relay and disconnect the voltage regulator anytime generator fre­quency drops to 380 Hz or below. This protects the voltage regulator
resistors
tor output in its attempt to maintain voltage when the generator is operating at a speed
which cannot produce normal voltage output.

(2, Fig. 7)

against overload which could be caused by very high voltage regula-

(19)

provides a quick-disconnect facility for all wiring to

(3)

is to automatically open the excita-

(Fig. 10)

and ballast

NOTE: If the auxiliary underfrequency relay is tripped, it will be necessary to momentarily place
engine operating mode switch (5, Fig. 9) in BUILD-UP-VOLTAGE position to restore generator
voltage.

F. Engine Control Panel (See Fig. 9)

The engine control panel is mounted directly below the control box. In addition to engine con­trols and instruments, generator output controls are mounted here. A Plexiglass window in
the canopy rear door, slants outward at the bottom to form an opening for access to controls
when the door is closed.

(1) Engine instruments

Engine operation is monitored by an ammeter

(10)

an oil pressure gage

(a) Ammeter

The ammeter

graduated range is from -60 A through 0 A, to +60 A.

The temperature gage
dicating mechanism which is connected by a capillary tube to a bulb mounted in the engine cooling sys­tem. The gage indicates engine coolant temperature in the range of 100F to 220F.

The oil pressure gage
graduated from 0 PSI to 75 PSI. An oil pressure switch is mounted in a tee fitting directly behind the gage.
The switch connects 12-V DC power to the engine control system and to the generator 12-V DC control
system when the engine is running.

(4)

indicates the direction and value of current flow in the 12-V DC electrical system. Its

(b) Temperature gage

(8)

is a mechanical type of unit construction. It consists of a panel mounted in-

(c) O il pressure gage and oil pressure switch

(10)

is a bourdon tube type and indicates engine lubricating oil pressure. It is

. An hourmeter

(4)

, a coolant temperature gage

(6)

records engine operating time.

(8)

, and

1-1 April 30/96 Revised
Page 20

OM-2031

(d) Hourmeter

(6)

The hourmeter
and records engine running time and will record up to 9999.9 hours on five revolving drums. The hourme­ter operates only when the engine is running and the oil pressure switch is closed.

An electric fuel gage
generator set. A sending unit mounted in the trailer or truck mounted unit fuel tank supplies the signal to
the gage. Twelve-volt DC operating power is supplied to the fuel gage from two sources.

The gage functions when the engine is running, or when the instrument lights are ON. Since two
power sources are connected to the fuel gage system, a blocking diode
source circuit. One diode prevents energizing the motor-generator control circuit when panel lights are
ON. Another diode prevents operation of the panel lights by the engine-generator circuit when the engine
is running. To check fuel quantity when engine is stopped, use switch

(2) Engine and generator controls

The engine-generator control switch

switch)

automatically reposition to GENERATE position when released. In BUILD-UP-VOLTS position it performs
a dual function. First, it supplies power to the governor control box, which allows the engine to operate at
normal governed speed; second, it momentarily supplies current for closing the excitation-deenergization
relay
the manual voltage control circuit for excitation of the generator exciter. In GENERATE position, power is
maintained to the governor control box and to the excitation relay
IDLE position, power is disconnected so that the engine returns to idle speed and the exciter field is deen­ergized.

is a three-position toggle type. It is spring-loaded in one position, BUILD-UP-VOLTAGE, and will

(3, Fig. 7)

contacts, to make three-phase, 115-V AC power available to the voltage regulator, or to

is electrically driven from the 12-V DC battery system. The hourmeter measures

(e) Fuel gage and blocking diodes

(2, Fig. 9)

(a) Engine-generator control switch

accurately indicates the quantity of fuel oil in the tank provided for the

(18)

is required in each power

(3)

to turn ON panel lights.

(5) (also identified as the “build-up-voltage, generate, idle”

(3, Fig. 7)

. When the switch is placed in

(b) Contactor control switch

This is another three-position, toggle switch
When placed in the spring loaded CLOSE position, it provides 115-V AC power directly to a rectifier which
supplies DC power for closing the load contactor. When released it returns to the normal ON position and
continues to provide power to the rectifier, but in this switch position, AC power must pass through the
plug interlock and fuse interlock relays. In OFF position the switch opens the AC circuit to the rectifier,
thereby cutting off the source of DC power to the contactor coil which allows the contactor to open.

(c) Instrument light and switch

A shielded, instrument panel light

(3)

atoggleswitch

, which also controls instrument lights on the control box.

(1)

is mounted at the left side of the control panel. It is controlled by

(7,Fig.9)

identical to the engine-generator control switch.

April 30/96 Revised 1-1

Page 21

OM-2031

(d) Engine starting circuit

(15)

The pushbutton start switch
an auxiliary solenoid switch. The auxiliary switch then connects power to the starter solenoid which func­tions to engage the starter gear with the flywheel ring gear and apply power to the starter motor to crank
the engine. The auxiliary solenoid switch is necessary because the start pushbutton switch is not capable
of carrying the high amperage flow to the starter solenoid which would result if the starter gear and ring
gear should fail to engage. The permissive toggle switch
placed in the down

A green indicating light
The light operates only when the engine is running and fuel pressure is sufficiently high to close a fuel
pressure switch. The purpose of the pressure switch is to deactivate the protective circuit when the engine
is stopped and prevent battery discharge.

Another green indicating light
and power is available at the generator output terminal panel

The push-pull control
consists of a group of items designed to inject a highly volatile fluid into the engine air intake system to as­sist ignition of fuel when air temperature is too low for the heat of compression to ignite a normal fuel mix­ture. The starting aid consists of a cylindrical, fluid container and a valve
mounted on the lifting yoke. The valve is operated by the control
allows fluid to flow into the valve. Pushing the control IN forces fluid through a small tube and an atomiz­ing nozzle into the inlet manifold. The addition of atomized, highly volatile fuel into the inlet air assists in ig­niting the diesel fuel mixture.

(STOP)

(e) Indicating lights

position.

(14)

(f) Cold weather starting aid control

(11)

andpermissivetoggleswitch

(18)

glows to indicate that power is available to the engine protective system.

(9, Fig. 9)

controls operation of a cold weather starting aid

glows when the generator output load contactor is CLOSED

(18)

serve to connect power for closing

also stops the engine when the toggle is

(13, Fig. 3).

(see 1-3, Fig. 4)

(11, Fig. 9)

(Fig. 3).

. Pulling the control outward

The starting aid

which are

(g) Fuse

A 10-ampere fuse
and 12-V DC system in the main generator protective system.

(3) Air cleaner indicator

(4) Test receptacle connector

(13)

protects the 12-V DC engine control circuit, hourmeter, illuminating light circuit,

The air cleaner indicator
function was explained in Para. 6, C,

This Amphenol connector
to selected test points throughout the engine and generator electrical systems. Connec­tions and schematic diagrams indicate points at which the leads are connected. The re­ceptacle connector is designed to mate with a test box plug connector

(12)

is mounted on the engine control panel for easy viewing. Its

(3) (see Fig. 6).

(19)

provides an attaching point for leads which are connected

(see Fig. 12).

1-1 April 30/96 Revised
Page 22

OM-2031

1. Panel light 12. Air cleaner indicator

2. Fuel gage 13. Engine circuit fuse (10-A)

3. Light switch 14. Engine “ON” indicating light

4. DC Ammeter 15. Engine starter switch

5. Engine-generator control switch 16. (Deleted)

6. Hourmeter 17. Terminal board

7. Load contactor control switch 18. Permissive start switch

8. Coolant temperature gage 19. Test receptacle

9. Load contactor indicating light 20. Charging circuit resistor

10. Engine oil pressure gage

11. Cold weather starting aid control

April 30/96 Revised 1-1

Engine Control Panel

Figure 9

Page 23

OM-2031

G. Voltage Regulator
Mag-Amp type, Hobart Part No. 430391C, See TM-759 in Chapter 6 of this manual.

Solid-State type, H obart Part No. 489812A, See OM-2020 in Chapter 6 of this manual.
H. Power Module Panel Assembly

The power module panel assembly
is located at the right rear of the machine behind the control box. On all models except the
tow tractor mounted unit, it is accessible by removing rear access-vent cover
the canopy. The panel assembly provides sensing and overload protection for the output cir­cuit and provides a means of connecting and disconnecting generator output to and from the

(aircraft).

load

(1) Load contactor

The load contactor
and four sets of contacts. The three larger contacts conduct three-phase AC generator
output. A smaller contact set is connected in the protective monitor circuit and supplies
12-V DC power used by sensing relays to signal the protective monitor when a fault oc­curs. Three-phase, 400-Hz generator output power is conducted to the load contactor by
2/0 cables which pass through 3 sets of current transformers

NOTE

:Thiscontactor may be replaced by theoldstylecontactorusedinprevious60-KVAmachines.

(6, Fig. 10)

(Fig. 10)

is a sealed unit which contains a magnetic operating coil

sometimes referred to as the “contactor panel”,

(2, Fig. 1)

on

(3, 4, and 9).

This note is for the benefit of those users who may have old style contactors Part number 75GH-566

(Hartman No. A-874C) in stock.

(2) Current transformers

(a) Ammeter current transformers

Three current transformers

to 5-A)

graduated and numbered so that the ammeter pointer will indicate the true load current value rather than
the meter movement current.

which will operate the ammeter

(4)

lower the output load current to a lesser value of definite ratio

(4, Fig. 9)

movement without damage. The ammeter dial scale is

(250-A

(b) Line-drop current transformers

The three line-drop current transformers
tude and power factor of current flowing from generator to load. They feed a signal to the voltage regula­tor which interprets the signal and alters the exciter field current as required to maintain a constant
predetermined voltage at the load

(see Voltage Regulator Manuals No. TM-759 for a Mag-Amp type or

OM-2020 for a Solid-State type regulator).

(c) Overload current transformers

Three overload current transformers
load current in each of the three output phases, and supply a reduced value current signal to the overload
module

1-1 April 30/96 Revised
Page 24

(7).

(9),

in conjunction with burden resistors

(3),

in conjunction with burden resistors

(8),

detect the magni-

(1),

monitor the output

(3) Overload module

OM-2031

Theoverloadmodule
formers
load condition exists in any generator output phase. A pull-apart electrical connector is
mounted on the overload module to provide quick-disconnect facilities for all wiring to the
module. The overload module is equipped with a hermetically sealed, reed-type relay. Re­lay contacts are normally open. The solidstate circuitry is designed to close relay contacts
when output current in ANY phase reaches 125% of normal rated output capacity. The
closed relay sends a signal to the protective monitor. This signal “gates” the overload
SCR
tor holding circuit, allowing the load contactor to open.

The following is a list of overload module characteristics:

NOTE

: The overload protective system will function when any phase carries 123% to 127% of rated

(3)

and to send a signal to the protective monitor module

(silicone-controlled rectifier)

(7)

is a solid-state device designed to interpret a signal from trans-

(4, Fig. 8)

in the protective monitor and interrupts the load contac-

load.

At 125% load the module will function in 4 minutes.
At 150% load the module will function in 16 seconds.
At 200% load the module will function in 4 seconds.

NOTE: All times are plus or minus 25% and are nonadjustable.

(4) Rectifier

A diode-bridge rectifier
converts it to a pulsating, direct current for energization of the load contactor holding coil
only. This DC coil-holding circuit is controlled indirectly be controlling the 400-Hz AC to
the rectifier. The ground circuit for the rectifier’s AC supply must pass through the relay
contacts in the protective monitor module to ground cable N. Therefore, any time a protec­tive device functions to open the protective monitor relay, the rectifier’s AC circuit is
opened. No DC is then available for the load contactor holding coil, hence, the load con­tactor opens.

(5)

receives 400-Hz AC from phase C of the generator output an

when an over-

(5) Terminal boards

(2)

Three terminal boards

April 30/96 Revised 1-1

provide connection facilities for small leads.

Page 25

OM-2031

Power Module Panel Assembly

1-1 April 30/96 Revised
Page 26

1. Overload resistor (16.6 ohm, 25 watt)

2. Terminal board

3. Overload current transformer

4. Ammeter current transformer

5. Rectifier

6. Load contactor

7. Overload module

8. Line drop resistor (50 ohm, 25 watt)

9. Line drop current transformer

10. Blocking diode

Figure 10

8. Test Box

The test box is an optional accessory item used for testing the generator set. All generator
sets are wired to accommodate a test box, however, the box is supplied only when ordered

(Part Number 388318A-1).

A. Description (See Fig. 11)

The test box assembly consists of a rotary selector switch, momentary contact pushbut­ton switch, and two, insulated-tip test jacks, mounted in a small metal box. Connection to
the generator set is made through a wiring harness equipped with a 26-contact plug con­nector which mates with a receptacle connector.

OM-2031

April 30/96 Revised 1-1

1. Test box

2. Cable

3. Plug connector

Test Box Assembly (Optional)

Figure 11

Page 27

OM-2031

B. Theory of Operation

Wire leads are connected to the electrical circuitry of the generator set at various points
and routed to a receptacle connector, mounted on the engine control panel. They are con­nected to the test box rotary switch by a plug connector and wiring harness.

The rotary selector switch is wired in such a manner that for any switch position, two pre­selected test points in the generator set circuitry are connected for testing. The selector
switch may be rotated to any one of 22 positions, however not all positions are used in
this installation. An instruction plate mounted under the switch knob indicates switch posi­tions and component tested in each position. Normal voltage for each test is a lso indi­cated.

Two test jacks are provided for connection of the test prods of a voltmeter. After the volt­meter is connected and selector switch positioned, the test circuit is closed by pressing
the pushbutton switch. A voltage value may then be observed on the voltmeter. This ar­rangement prevents energization of test circuitry and equipment for extended periods and
allows the operator to reset and adjust the voltmeter without disconnecting it from the box.

For operating instructions, see Sect. 1-3, Para. 3

9. Special Equipment for Specification 6911A-5 Generator Sets

The assemblies below, which are optional on other units covered by this manual, are stand­ard equipment for Specification 6911A-5 generator sets, and are installed at the factory when
a generator set of this specification is ordered by the customer.

A. Low-Fuel Shutdown Assembly with Pilot Light

This low fuel shutdown assembly, Hobart Part Number 285953, stops the engine when
the fuel level in the fuel tank becomes low before the unit runs out of fuel. A liquid-level
detector, mounted in the fuel tank, opens the power to the engine governor system when
fuel drops to a predetermined level in the fuel tank, and the pilot light that is a part of this
assembly comes on.

B. The Low Coolant Shutdown Kit

The low coolant shutdown kit on this generator set stops the engine before overheating,
caused by low coolant, can occur. A liquid-level detector, mounted in the radiator tank,
opens the power to the engine fuel valve solenoid when coolant drops to a predetermined
level in the radiator.

NOTE: Radiator MUST be refilled after a low-coolant shutdown before engine can be restarted.

C. Emergency Stop Switch

This switch, Hobart Part Number 285958, on the generator set control panel, is used
manually by the operator to stop the engine quickly and safely in the event of an emer­gency observed by the operator.

.

D. Forklift Support Assembly

This assembly, Hobart Part Number 482743, permits the safe lifting of the generator set
with a forklift of sufficient lifting capacity. The forklift used should have a lifting capacity of
at least 5000 pounds

1-1 April 30/96 Revised
Page 28

(2267.6 kg)

.

SECTION 2. PREPARATION FOR USE, STORAGE, OR SHIPPING

1. Preparation for Use

A. General

These instructions are based on the assumption that the tow tractor mounted unit is properly installed on
the tractor and that all necessary fuel and electrical connections have been made. Hobart Brothers Com­pany does not build an aircraft tow tractor. Generator sets for tractor mounting are installed by the cus­tomer, or tractor manufacturer. Other generator sets, when ordered with truck or trailer, are mounted at
the Hobart factory and are shipped in running condition and ready for operation after inspection and check.

WARNING: IMPROPER OPERATION CAN KILL, INJURE, OR CAUSE DAM­AGE! READ AND UNDERSTAND OPERATING INSTRUCTIONS IN SECTION 1­3 BEFORE OPERATING THE UNIT.

OM-2031

B. Inspection/Check
Inspect the unit thoroughly prior to operation.

(1) Remove blocking, banding, ties, and other securing material.
(2) Inspect exterior for shipping damage such broken lights, damaged sheet metal, etc.
(3) Open all canopy doors and inspect interior for foreign material such as rags, tools, shipping pa-

pers, etc.
(4) Check fuel, coolant, and oil hoses and connections for visible leaks. Visually inspect the compart-

ment floor and ground surface under the unit for signs of leakage. If leaks are found, correct by tight­ening hose clamps, tube fittings, etc., as required.

(5) Check security of tractor mounted generator set retaining components
(6) Check the following for sufficient quantity:

(a) Fuel

Turn ON panel lights to energize fuel gage when engine is stopped.

plied from the tow tractor tank.)

(Sect. 2-1, Fig. 2).

(Tractor-mounted units are sup-

August 5/89 Revised 1-2

Page 1

OM-2031

(b) Engine coolant

The radiator cap is accessible by opening the hinged access cover on the front canopy housing. Cool­ant level should be approximately one inch below the filler neck. Allow a capacity for coolant expan­sion.

CAUTION: BE SURE THE COOLING SYSTEM ANTIFREEZE SOLUTION IS ADEQUATE TO PRO­TECT BELOW LOWEST TEMPERATURE EXPECTED.

NOTE: For antifreeze protection, use a solution of 50% permanent antifreeze (Ethylene glycol) and 50%
clean water.

(c) Engine lubricating oil

Oil level should be at “FULL” mark on oil level gage rod. See the Perkins Shop Manual for oil recom­mendations.

(7) Check air cleaner

The air cleaner
material covering the air inlet area.

C. Installing Output Cables
Units are generally shipped without generator set-to-aircraft cables.

(Sect. 1-1, Fig. 3, item 8)

is a “dry” type. Be sure there are no papers, tapes, or other

NOTE: Generator sets designed for tractor mounting are equipped with a generator output receptacle
connector. No output cable wiring is required. An output cable assembly with plug connector on each
end is required for tractor-mounted machines (see 1-1; 12, Fig. 3).

(1) Three-phase, AC output cable assembly installation
The AC output terminal panel is located on the left side, below the air cleaner and left of the engine

control panel

(a) Open left rear canopy doors and loosen cable clamp screws at cable horn
(b) Route cables through cable horn and clamp and upward to terminal board.

(see Fig. 1).

(see 1-1; 13, Fig. 3).

NOTE: Conductor size recommended for AC output is 2/0 size. Use No. 12 size for control (E and F
terminals).Largecables(A,B, C, N)should beequippedwith terminalshavingat leasta 3/8-inchdiameter
mounting hole. Mounting hole in small leads (E and F) should be at least 1/4-inch diameter.

1-2 August 5/89 Revised
Page 2

OM-2031

(c) Each terminal stud is identified by an identification plate. Each cable should be identified by a
band-type marker. Connect cable “A” to terminal “A”, “B” to “B”, etc. Tighten terminal nuts se­curely. Connect small plug interlock lead “E” or “F” to terminal “E” or “F”.

(d) Tighten clamp screws securely, but avoid damage to cable insulation.

(2) Transformer-rectifier

(DC)

output cable installation

as illustrated in Figure 2. Use 4/0 size cables.

(optional equipment)

. Install DC output cables

August 5/89 Revised 1-2

AC Output Terminal Panel

Figure 1

Page 3

OM-2031

T-R Output Cable Installation

Figure 2

2. Preparation for Storage

When a generator set is to be stored or removed from operation, special precautions should be taken to
protect the internal and external parts from rust, corrosion, and gumming in the engine fuel system.

A. General

(1) The unit should be prepared for storage as soon as possible after being removed from service.
(2) The unit should be stored in a building which is dry and which may be heated during winter

months.
(3) Moisture absorbing chemicals are available for use where excessive dampness is a problem, how-

ever the unit must be completely packaged and sealed if moisture absorbing chemicals are to be ef­fective.

1-2 August 5/89 Revised
Page 4

B. Temporary Storage

When storing the unit for 30 days or less, prepare as follows:

(1) Lubricate the unit completely in accordance with instructions in Sect. 2-1. This will include chang­ing engine oil, and all filter elements.

(2) Start the engine and operate for about two minutes so that all internal engine components will be
coated with new oil.

NOTE: Do not drain the fuel system or crankcase after this run.

(3) Make certain the cooling system antifreeze solution is adequate to protect below the lowest tem­peratures expected during the storage period. See 2-1; Para. 7, D. Be sure the solution is thoroughly
mixed.

(4) Clean the exterior of the engine with fuel oil. Dry with clean rags and compressed air.
(5) Seal all engine openings. Use a waterproof, vaporproof material which is strong enough to resist

puncture damage from air pressures.

OM-2031

C. Long Time Storage (Over 30 Days)

(1) The unit may be stored for long periods with no special preparation if it is possible to operate the

engineonceeachweek.

(a) Make certain the cooling system is adequately protected.
(b) Start the engine and operate at a fast idle

reached at least 140 deg F.

(800 to 1000 RPM)

until coolant temperature has

WARNING: MAKE CERTAIN OF ADEQUATE VENTILATION BEFORE START­ING THE ENGINE.

(c) Operate normal operating controls.

(2) If weekly operation is not possible, prepare and protect the engine in accordance with instructions

in Perkins Diesel Operator’s Manual.
(3) To protect the generator and other electrical components, the complete unit should be packaged,

using moisture proof packaging and sealing material. Place containers of moisture absorbing chemi­cals, such as silica-gel, in the unit before packaging.

August 5/89 Revised 1-2

Page 5

OM-2031

3. Preparation for Shipment (Tractor-Mounted Units Only)

During long shipments by rail
vibration, jolting, etc.

CAUTION: WHEN SHIPPING THE UNIT (MOUNTED IN A TOW TRACTOR), PROVIDE ADDITIONAL
RETAININGMATERIALSTO MAKE CERTAINTHE GENERATORSET CANNOT ROLL OUT OF THE
TOW TRACTOR.

NOTE: It is suggested that strong banding may be used to secure the generator set, or a strong steel
bar may be welded or bolted across the front of the generator set frame.

(and other)

the generator set retaining hardware may become loosened by

1-2 August 5/89 Revised
Page 6

SECTION 3. OPERATION

1.General

This section contains information and instructions for the safe and efficient operation of the equipment.
Operating instructions are presented in step-by-step sequence of procedures to be followed in supplying
400-Hz power to an aircraft.

WARNING: IMPROPER OPERATION CAN KILL! EAR PROTECTION EQUIP­MENT MAY BE NECESSARY WHEN WORKING IN CLOSE PROXIMITY TO
THIS EQUIPMENT. READ AND FOLLOW ALL OF THE OPERATING INSTRUC­TIONS BEFORE ATTEMPTING TO OPERATE THE EQUIPMENT.

2. Operating the Generator Set

A. Pre-start Inspection

(1) Open the fuel shut-off valve.
(2) Provide 12-V DC power to the engine starting system.

OM-2031

(3) Check the engine and generator compartments and remove rags or other foreign materials.

B. Normal Engine Starting Procedures

Engine starting procedures are outlined below. Engine operating controls and monitoring instruments
are illustrated in Fig. 1.

(1) If illumination is required, place light switch

NOTE: This switch must be ON to check fuel when engine is stopped.

(2) Hold engine start switch

(28)

ton
switch

(3) Check ammeter
(4) Check fuel gage
(5) Place engine generator control switch
(6) Activate generator output contactor switch

to crank engine. When engine starts, release pushbutton. Continue to hold engine start

(30)

in position until oil pressure gage

(17)

(15)

(30, Fig. 1)

for charge reading.

and oil gage

in START position momentarily. Push engine start pushbut-

(23).

(16)

in ON position.

(23)

reads at least 20 PSI pressure. Release switch

(18)

in IDLE position.

(20).

(30).

October 1/95 Revised 1-3

Page 1

OM-2031

1. Frequency meter

2. Voltmeter

3. Fastener

4. AC Ammeter

5. Meter switch

6. Line switch

7. Reset switch

8. Light test switch

9. Fault indicating lights

10. Load contactor circuit fuse (2-A)

11. Protective system fuse (2-A)

12. Protective relay tray

13. Instrument panel light

14. Generator control tray

15. Fuel gage

16. Light switch

17. DC Ammeter

Operating Controls and Instruments

Figure 1 (Sheet 1 of 2)

1-3 October 1/95 Revised
Page 2

18. Engine-generator control switch

19. Hourmeter

20. Load contactor control switch

21. Coolant temperature gage

22. Load contactor indicating light

23. Oil pressure gage

24. Cold weather starting aid control

25. Air cleaner indicator

26. Engine circuit fuse (10-A)

27. Engine protective circuit indicating light

28. Engine starter switch

29. Blocking diodes

30. Permissive start switch

31. Test receptacle connector

OM-2031

32. Manual voltage control rheostat

33. Automatic-manual voltage control
switch

34. Test bank switch

October 1/95 Revised 1-3

35. Light test switch

36. Reset switch

Operating Controls and Instruments

Figure 1 (Sheet 2 of 2)

Page 3

OM-2031

C. Cold Weather Engine Starting Procedures

A cold weather starting-aid kit
low 50 degree F. To start the engine, using the starting aid, proceed as follows:

(1) Position switches and controls as instructed in steps
Starting Procedures, above.

(2) Prepare starting aid for use. The starting aid is shipped in a safe condition and is not operable un­til assembled. Assemble as follows:

(Fig. 2)

is provided to assist in starting the engine at temperatures be-

(1)

through

(4),

paragraph B, Normal Engine

WARNING: FIRES, FUMES, AND FLYING PARTS CAN KILL OR INJURE!
STARTING FLUID IS EXTREMELY FLAMMABLE. IT IS UNDER PRESSURE.
USE CAUTION WHEN HANDLING. AVOID CONTACT WITH SKIN AND AVOID
BREATHING VAPOR.

(a) Loosen clamp screws

tective cap

(b) Usebottleopenertoremovecylindercap
(c) Slide the cylinder

aid is now ready to use.

(3)

and plug

(1, Fig. 2)

and slide the cylinder

(4).

(3).

Unscrew and remove plug

(2)

downward and thread into the valve

(2)

upward sufficiently to remove pro-

(4).

(5).

Tighten securely. The starting

1. Clamp screw

2. Fluid cylinder

3. Cap

4. Plug

5. Valve

Cold Weather Starting Aid

(When Provided)

Figure 2

1-3 October 1/95 Revised
Page 4

(3) Cold weather starting procedures are exactly the same as for normal starting except:

OM-2031

(a) Before cranking the engine, pull the starting aid control

travel. Hold for 2 to 3 seconds.

(This allows the starting aid valve chamber to fill with pressurized

(24, Fig. 1)

OUT to the full extent of its

ethyl ether.)

(b) Push the control IN.
(c) Push starter switch
(d) Follow normal starting procedures and CAUTIONS above [steps
(e) In extremely cold weather it may be necessary to repeat steps

(This step sprays starting fluid into the engine intake manifold.)

(28)

to crank engine.

(5)

(a)

through

and

(b)

(7),

above.

para. 2, B].

CAUTION: USE STARTING AID ONLY FOR STARTING. DO NOT OPERATE
WHILE ENGINE IS RUNNING.

WARNING: DO NOT “FLOOD” THE ENGINE WITH STARTING FLUID. A SERI­OUS EXPLOSION COULD RESULT.

D. Preparation for Power Delivery (Normal Automatic Voltage Control)

The following are power delivery preparation procedures to be followed after the engine is started.

(1) Check and position switches and controls.

(a) Loosen fastener

switch

(b) Loosen fastener
CRAFT position if the aircraft being serviced is equipped with 28.5-V DC interlock relay system.

(33)

in AUTOMATIC position. Close tray and secure.

(If not, place in TEST BANK position.)

(c) Meter switch

(2) Connect output cable plug connector to aircraft receptacle. Be sure connectors are mated fully

and securely.

E. Power Delivery (Automatic Voltage Control)

(1) Place engine-generator control switch

then allow it to position itself in GEN position. The electric governor will immediately increase engine
speed to 2000 RPM and maintain it.

(2) Observe generator instruments. Frequency meter

(2)

meter
(3) The final step in delivering power is closing the load contactor. When satisfactory frequency and

voltage values are indicated by the instruments, close the load contactor by momentarily placing the
load contactor control switch
light
the aircraft. As soon as the light glows, release the switch. It will automatically return to the center ON
position.

should indicate 115 V AC when line switch

(22)

should glow at once to indicate that the load contactor is closed and power is available at

(3,Fig.1)

(3)

and pull protective relay tray outward. Place test bank switch

(5)

may be in any position except pointing straight DOWN.

and pull generator control tray outward. Place automatic-manual

Slide tray in and secure.

(20)

in the top

(18, Fig. 1)

(spring loaded),

in BUILD-UP-VOLTAGE position momentarily,

(1, Fig. 1)

(6)

is in LINE-TO-NEUTRAL position.

should indicate exactly 400 Hz. Volt-

CLOSE position. The green indicating

(34)

in AIR-

October 1/95 Revised 1-3

Page 5

OM-2031

NOTE:

are ON, it indicates that 28.5-V DC holding current is not being supplied from the aircraft to the
plug-interlock relay. Correct the condition an again operate the load contactor control switch (20) as
above.

F. Preparation for Power Delivery (Manual Voltage Control)

G. Power Delivery (Manual Voltage Control)

Power delivery using manual voltage control is the same as automatic delivery [Para. E, (1) thru (5)
above] except:

If the indicating light (22) should “go-out” as soon as the switch is released, and no fault lights

(4) It is recommended that the operator check output voltage and current in each of the three phases

(5)

early in the power delivery run. Use the meter switch
select line-to-line or line-to-neutral voltage. If the load is changing, it is good operating practice to ob­serve the instruments until load conditions stabilize.

(5) A condition of overvoltage, undervoltage, underfrequency, overfrequency, or overload in the out­put circuit will automatically open the load contactor and turn on the applicable indicating light to sig­nal the operator which of the above faults caused the protective monitor system to operate. After the
fault has been corrected, press the reset switch
tive relay system. Proceed with power delivery by operating the load contactor switch.

Preparation for power delivery using manual voltage control is exactly the same as for automatic con-

(1)

thru

(2)

trol [Para. 2, D,

(1) Place automatic-manual switch
(2) Set the manual voltage control rheostat

above] except:

(33)

in MANUAL position.

(7)

(32)

near its mid-range position.

to select the phase. Use the line switch

to turn off the indicating light and reset the protec-

(6)

to

(32)

(1) Control generator output voltage by adjusting the rheostat
reading on the voltmeter

COUNTERCLOCKWISE to DECREASE voltage.
(2) Adjust voltage to 115 V AC.
(3) During manual power delivery the operator must remain with the generator set to adjust output

voltage for varying loads and conditions.

H. Discontinue Power Delivery

(1) Place the load contactor switch

to indicate that the load contactor has opened and power is no longer being delivered to the aircraft.

(2) Place engine-generator control switch
(3) Disconnect output cable from aircraft.

(2).

Turn the rheostat

(20)

(32)

knob CLOCKWISE to INCREASE voltage and

in OFF position. Green light

(18)

in IDLE position.

to maintain a steady 115-V AC

(22)

should go OFF immediately

WARNING: HIGH VOLTAGE - ELECTRIC SHOCK OR FIRE CAN KILL! NEVER
DISCONNECT THE OUTPUT CABLE WHILE POWER IS BEING DELIVERED.

K. Stopping the Engine

(1) Allow the engine to idle a few minutes before stopping, to permit cooling.
(2) To stop the engine, move the START-RUN-STOP switch

(30)

to the STOP

(down)

position.

1-3 October 1/95 Revised
Page 6

3. Test Box Operation

The test box is useful and convenient in testing the generator set after repair or overhaul and also in
trouble shooting. To operate the test box, proceed as follows:

A. Open left, rear canopy doors and connect the test box plug connector (see 1-1; 3, Fig. 14) to the
test receptacle connector (Fig. 4).

B. Connect the test prods of a voltmeter at the test jacks (3 and 4, Fig. 3). Test jacks are color coded.
RED indicates POSITIVE. BLACK indicates NEGATIVE.

C. Locate the component or circuit to be tested in the DESCRIPTION column on the instruction plate
and set the selector switch (1, Fig. 3) to the number indicated opposite the description.

D. Note the normal voltage value and kind of current (AC or DC) to be expected at the position and
set voltmeter accordingly.

E. Comply with conditions indicated in CONDITIONS column for the particular test being performed.
F. Press the pushbutton switch (2) and observe voltage indicated by the voltmeter. Compare to nor-

mal voltage indicated in VOLTAGE column.

G. Release pushbutton switch.
H. Repeat steps A thru G for other test as required.

OM-2031

J. When test are completed, disconnect the test equipment and close canopy doors.

October 1/95 Revised 1-3

Test Box Operating Controls

Figure 3

Page 7

OM-2031

Test Receptacle

Connector

Figure 4

4. Transformer-Rectifier Operation

Transformer-Rectifier operating instructions are contained in its operating manual, however some gener­ator set instructions are required here.

A. Direct Current Power Delivery

NOTE: If the customer adds a Transformer-Rectifier to a standard machine which was
with a T-R when it left the factory, he must remove the jumper lead which will be found on the small
terminal strip in t he generator set voltage regulator (see 1-1; 19, Fig. 12). If your generator set has a
factory installed T-R, the jumper will have been removed.

(1) When delivering power from a T-R, prepare the generator set for DC power delivery the same as
for AC delivery, except do not connect AC output cable and do not close AC load contactor (see Para.
2, D and E).

(2) For T-R operating instructions, see Hobart Manual No. OM-433.

B. Simultaneous 28.5-V DC and 115-V AC Power Delivery

If both 28.5-V DC and 115-V AC must be delivered at the same time, the following rules and precau­tions

must be observed.

(1) Place T-R current limiting switch in OFF position. This will eliminate the soft start feature of the T­R, but will prevent AC voltage from dropping low enough to trip the AC load contactor.

(2) Line-drop compensation on the T-R must be REDUCED or turned DOWN completely to prevent
opening of the AC load contactor by an overvoltage condition. Readjust T-R line-drop compensation
so that AC voltage (as indicated by the generator set voltmeter) does not exceed 118-V AC when the
DC load is 500 Amperes. If higher DC voltage is needed, adjust T-R line-drop compensation as re­quired.Observe AC voltage while making this adjustment to be certain that it does not go TOO HIGH
with DC load.

(Optional Equipment) (See Fig. 5)

NOT

equipped

(3) During simultaneous, continuous operation, loads on either circuit are limited only by the capaci­ties of their respective circuits, however, the combined loads should not exceed the rated capacity of
the generator set (90 KVA or 72KW).

1-3 October 1/95 Revised
Page 8

OM-2031

6. Trailer Operation (Optional)

A. Towing

Observe the following rules when towing the trailer.

(1) Be sure all output cables are disconnected and properly stowed.
(2) Be sure parking brake is released.
(3) Avoid turns which are shorter than the steering linkage will freely allow.
(4) Avoid dangerous speed and sudden turns.

B. Parking

Observe the following rules when parking the trailer.

(1) Apply parking brake before disconnecting tow vehicle.
(2) Always place drawbar in an upright, vertical position when trailer is parked.

Transformer-Rectifier

Figure 5

October 1/95 Revised 1-3

Page 9

OM-2031

7. Low Fuel Shutdown Assembly

A. Description

The low fuel shutdown assembly, when requested as an option by a customer, may be used with all
generator set specifications covered by this manual. It is identified by H obart Part Number 285953 .
Its purpose is to stop the engine when the fuel level in the fuel tank becomes low before the unit runs
out of fuel. A liquid-level detector, mounted in the fuel tank, opens the power to the engine fuel valve
solenoid when fuel drops to a predetermined level in the fuel tank.

NOTE: Fuel tank MUST be refilled after a low-fuel shutdown before engine can be restarted.

B. Location of Relay and Low Fuel Sensor

Figure 6 shows where the low fuel relay is installed on the rear of the generator control box., and Fig­ure 7 shows where the low fuel sensor is installed on the fuel tank. Engine schematic diagram
281886 in Chapter 6 identifies the low fuel shutdown sensor as item S54, and the low fuel relay as
K65.

1. Control box

2. Relay retainer spring

3. Relay

4. Relay socket

5. Relay mounting bracket

Location for Relay on

Generator Control Box

Figure 6

1-3 October 1/95 Revised
Page 10

OM-2031

Location of Low Fuel Level Switch

Figure 7

C. Checking Operation of the Low Fuel Shutdown Assembly

The low fuel shutdown sensor (S54) has a TEST terminal, which permits testing of the sensor by elec­trically simulating a low fuel condition. To check operation of the low fuel shutdown sensor:

(1) Turn on the generator set and operate it at idle speed.
(2) Using a jumper wire with an alligator clip on each end, ground the TEST terminal on the low fuel

shutdown sensor. The generator set engine should shut off immediately.

October 1/95 Revised 1-3

Page 11

OM-2031

D. Replacement Parts

The following chart is a list of the major items which comprise the low fuel shutdown assembly, except
for hardware which is available from any hardware store. If it becomes necessary to replace any of
the items listed below, these items may b e ordered from Hobart Brothers Company using their part
numbers as given below.

ITEM

1
2

3
4

5
6
7

8
9

10

11

12

DESCRIPTION

Socket, Relay 16DA-4052-0
Mount, Socket, Relay 16DA-4029
Screw, #6-32 X 3/8,

SF-TAP, PAN HD, ST
Relay, Enclosed 283000-1
Retainer, Relay, Spring 16DA-4253-0
Diode 1CZ-93B
Sensor, Low Fuel Level 285954-1
Harness, Connector,

Sensor

Splice, Butt 400161-1
Sleeving, Heat-Shrink, 1/8" 484689-1

Sleeving, Heat-Shrink,

3/16"

Sleeving, Wire, Yellow 41501

HOBART

PART No.

W-11223-2

285955-1

484690-2

NUMBER

REQUIRED

1
1

2
1

1
1
1

1
4
2

4

86"

13

14

15

16

17

18

19

1-3 October 1/95 Revised
Page 12

Clamp, Wire 12CW-908

Tubing, 1/2", Z-Flex 76A-1131

End, 1/2", Z-Flex 76A-1135

Screw, M10-1.5 X 20 mm,

HEX-HD CAP
Washer, Flat, M10, ST 281929-6

Washer, Lock, M10, ST 281930-6

Washer, Lock, M10, IET 283467-6

405061-8

2

30"

2

1

1

1

1

8. Low Coolant Shutdown Assembly

A. Description

The low coolant shutdown assembly, when provided, is used with Specification 6911A-5 Hobart en­gine-drive generator sets. Its purpose is to stop the engine before overheating, caused by low cool­ant level, can occur. A liquid-level detector, mounted in the radiator, opens the power to the engine
coolant level solenoid when coolant drops to a predetermined level in the radiator.

NOTE: Radiator MUST be refilled after a low-coolant shutdown before engine can be restarted.

B. Location of Low Coolant Relay and Low Coolant Sensor

Figure 6 shows where the low coolant relay is installed on the rear of the generator control box., and
Figure 8 shows where the low coolant sensor is installed on the radiator. Engine schematic diagram
281886 in Chapter 6 identifies the low coolant shutdown sensor as item S45, and the low coolant re­layasK28.

C. Checking Operation of the Low Coolant Shutdown Assembly

The low coolant shutdown sensor, shown in Figure 8, has a TEST terminal, which permits testing of
the sensor by electrically simulating a low coolant condition. To check operation of the low coolant
shutdown sensor:

(1) Turn on the generator set and operate it at idle speed.

OM-2031

(2) Using a jumper wire with an alligator clip on each end, ground the TEST terminal on the low cool-

ant shutdown sensor. The generator set engine should shut off immediately.

Location of Low

Coolant Level

Switch

Figure 8

October 1/95 Revised 1-3

Page 13

OM-2031

D. Replacement Parts

The following chart is a list of the major items which comprise the low coolant shutdown assembly, ex­cept for hardware which is available from any hardware store. If it becomes necessary to replace any
of the items listed below, these items may be ordered from Hobart Brothers Company using their part
numbers as given below.

ITEM

1
2

3
4

5
6
7

8
9

10

11

12

DESCRIPTION

Socket, Relay 16DA-4052-0
Mount, Socket, Relay 16DA-4029
Screw, #6-32 X 3/8,

SF-TAP, PAN HD, ST
Relay, Enclosed 283000-1
Retainer, Relay, Spring 16DA-4253-0
Diode 1CZ-93B
Radiator, Assembly 285961
Harness, Connector,

Sensor

Splice, Butt 400161-1
Sleeving, Heat-Shrink, 1/8" 484689-1

Sleeving, Heat-Shrink,

3/16"

Sleeving, Wire, Yellow 41501

HOBART

PART No.

W-11223-2

285955-1

484690-2

NUMBER

REQUIRED

1
1

2
1

1
1
1

1
4
2

4

55"

13

14

15

16

17

18

19

20

1-3 October 1/95 Revised
Page 14

Clamp, Wire 12CW-908

Tubing, 1/2", Z-Flex 76A-1131

End, 1/2", Z-Flex 76A-1135

Screw, M10-1.5 X 20 mm,

HEX-HD CAP
Washer, Flat, M10, ST 281929-6

Washer, Lock, M10, ST 281930-6

Washer, Lock, M10, IET 283467-6

Cap, Radiator 181930

405061-8

2

55"

2

1

1

1

1

1

9. Emergency Stop Assembly

A. Description of the Emergency Stop sensor

The emergency stop assembly, when requested as an option by a customer, may be used with all
generator set specifications covered by this manual. It is identified by H obart Part Number 285958 .
Its purpose is to stop the engine in the event that a condition develops which could damage the gener­ator set or endanger personnel, such as uncontrolled overspeed or an open flame in the interior of the
unit.

B. Location of the Emergency Stop sensor

The emergency stop switch is a red mushroom-shaped switch installed on the left side of the unit, on
the door that is just left of the engine control panel door. Engine schematic diagram 281886 in Chap­ter 6 identifies the emergency stop switch as item S28.

C. Checking Operation of the Emergency Stop sensor

To check operation of the emergency stop switch:

(1) Turn the generator set ON and operate it at idle speed.
(2) Press the emergency stop switch. The engine should shut off immediately.

D. Replacement Parts for the Emergency Stop sensor

OM-2031

The following chart is a list of the major items which comprise the emergency stop sensor assembly,
except for hardware which is available from any hardware store. If it becomes necessary to replace
any of the items listed below, these items may be ordered from Hobart Brothers Company using their
part numbers as given below.

ITEM

Plate, Legend 285681
sensor, Operator, PB, Mushroom 77A-1157
Guard, Mushroom Button 285125
Sleeving, Yellow 41502
Tie, Anchor, Cable, Plastic 400826-1
Screw, M3.5 X 9.5 mm,

PAN-HD, SF-TAP

HOBART

PART No.

282909-1

NUMBER

REQUIRED

1
1
1
60"
3

2

October 1/95 Revised 1-3

Page 15

OM-2031

10. Service Information

If you have any questions concerning your Hobart Ground Power Division equipment, you are in­vited to contact our Service Department by mail, telephone or FAX.

Write: Hobart Brother Company

Ground Power Division
Service Department
1177 Trade Square East
Troy, Ohio 45373
U.S.A.

In U.S.A. Call: [phone] (Parts)

[phone] (Service)

From Other Countries Call: [phone] (Parts)

[phone] (Service)

FAX: [phone] (Parts)

[phone] (Service)

1-3 October 1/95 Revised
Page 16

OM-2031

CHAPTER 2. SERVICE

SECTION 1. MAINTENANCE

1. General

To make certain the generator set is always ready for operation, it must be inspected and maintained
regularly and systematically so that defects may be discovered and corrected before they result in serious
damage or failure of the equipment.

WARNING! Electric shock, flying parts, or fire can kill or injure! Stop
operation immediately if a serious or possibly dangerous fault is discovered.

2. Operation of Roll-Out Feature (For Tractor-Mounted Units Only)

One of the first things to learn about the service operation is how to roll the generator partially out of the
tow tractor so that components on the right side and bottom of the unit are more accessible.

A. Roll Generator-Set Out for Service

(1) Make CERTAIN the stop-bar
(2) Remove two each attaching nuts, screws, and lockwashers

at the front of the machine.
(3) Roll the generator set outward carefully, until the stop-bar

left track. This will allow access to the right side and underside of the engine.

B. Roll Generator-Set In to Normal Position

(1) Roll the machine inward carefully until the retaining brackets

in the tracks.
(2) Install attaching screws, nuts, and lockwashers and tighten securely.

(Figure 1)

is down as far as it will go in SAFETY position.

(1,Fig.2)

(Figure 1)

(2, Figure 2)

from retaining brackets

contacts the stop-block in the

contact the end gussets

3. Inspection

A periodic inspection should be established and maintained. A suggested inspection/check schedule is
provided in 2-2, Figure 1, however it may be modified as required to meet varying operating and
environmental conditions. If the generator set is mounted on a tow tractor, it is suggested that inspections
be coordinated.

(2)

November 18/91 Revised 2-1

Page 1

OM-2031

Roll-Out Stop-Bar (For tractor-mounted units only)

Figure 1

1. Attaching hardware: nuts,
screws, and lockwashers

2. Retaining brackets

Generator Set Retaining Components

(Tractor-mounted unit only)

Figure 2

2-1 November 18/91 Revised
Page 2

4. Lubrication

A. General

Proper lubrication is one of the most important steps in good maintenance procedures. Proper
lubrication means the use of correct lubricants and adherence to a proper time schedule. Frequency
of lubrication and recommended lubricants are indicated in Figure 3.

B. Generator

The 400-Hz generator requires NO lubrication. The rotor is supported by two ball bearing assemblies
which are lubricated and sealed at the factory for lifetime, maintenance-free operation. It is suggested
that generator bearings be checked after 5000 hours of operation.

C. Generator Controls

Generator controls and instruments require no scheduled periodic lubrication. A few drops of oil may
be required on door hinges occasionally to insure free an quiet operation.

D. Engine

Although the engine and its accessories require no more attention than any other similar installation,
they still inherently require a major portion of the generator set lubrication and maintenance.
Recommendations regarding engine lubrication have been taken from the engine manufacturer’s
“Operator’s Manual” and incorporated here to make them more readily available to operators and
maintenance personnel.

OM-2031

(1) Lubrication schedule

Time schedules indicated on the Lubrication Chart, Fig. 3, are approximate. They are based on
average operating conditions. It may be necessary to lubricate more frequently under severe
operating conditions such as: low engine temperatures, excessively heavy loads and high oil
temperatures, or intermittent operation. However, time intervals should not exceed those
indicated in the chart without careful evaluation.

(2) Oil specification

Oil recommended by the engine manufacturer is identified by a military specification number, MIL­L-2104B. Because of the substantial increase in additive concentration in some MIL-L-2104B oils
to meet service “MS” requirements, recommended oil is qualified still further by the following
limitations

(a) Zinc, as zinc diorganodithiophosphate, between a minimum of 0.07 and a maximum of 0.10
percent by weight.

(b) Sulfated ash
contain only barium detergent-dispersants where 1.50 percent by weight is allowed.

Diesel lubricating oil specifications are discussed in the Cummins Handbook for Diesel Engines.

(3) Oil viscosity

The use of an SAE-30 grade oil is recommended for year-round service. The engine is equipped
with an ether starting aid to assist in engine starting during cold weather when SAE-30 oil is used.
Multi-grade oils are NOT recommended, and should be considered only as a “last resort” to
facilitate engine starting.

(ASTM D-874)

of 1.00 percent maximum by weight, except lubricants that

November 18/91 Revised 2-1

Page 3

OM-2031

(4) Changing engine oil

Change engine lubricating oil following the instructions in the Cummins Engine Shop Manual

(Chapter 6).

(5) Changing engine oil filter

Change the oil filter following the instructions in the Cummins Engine Shop Manual (Chapter 6).

E. Starter

The starting motor is lubricated at assembly and should be relubricated only when the starter is
removed from the engine or when disassembled.

Remove pipe plugs on outside of motor and apply a few drops of light engine oil to the oil wicks.

Lube oil capacity for this engine is 17.3 QUARTS.

ITEM MAINTENANCE REQUIRED

Lube Oil Checkoil level daily or after every 10 hours of use. Change oil after 200 hours

or one month of use. Use heavy duty oil such as SAE-30 (MIL-L-2104B).
Engine lube oil capacity: 17.3 QUARTS.

Lube Oil Filter Change oil filter every 200 hours or 1 month of use.

Fuel Oil Filter Drain filter daily. Change filter element every 800 hours or 6 months of use.

Starter Lubricate as needed, using heavy duty engine oil such as SAE-30

(MIL-L-2104B). Lubricate only when starter is removed from engine.

Coolant Check coolant level daily. Service and maintain coolant system according to

para. 6. Engine coolant capacity: 15.3 QUARTS.

Air Cleaner Change air cleaner cartridge as required by air cleaner indicator (on engine

control panel).

AC Generator AC generator bearings are sealed and require no periodic lubrication.

Lubrication and Maintenance Chart

Figure 3

2-1 November 18/91 Revised
Page 4

5. Air Cleaner Service

The air cleaner is a dry type with replaceable filter cartridges. A definite time schedule for changing the
filter cartridge cannot be determined because of varying operating conditions. Change the filter cartridge
when the red indicator “flag” reaches the top of the viewing chamber and locks in that position. Change
the cartridge as follows:

A. Cartridge Removal (See Fig. 4)

OM-2031

(1) Open canopy door and remove clamp assembly
(2) Remove baffle assembly
(3) Remove primary element

(7).

(4),

and replace with new element.

(3)

from air cleaner

Caution: Do not clean or re-use cartridge.

(4) Inspect the interior of the cleaner housing

B. Cartridge Installation (See Fig. 4)

(1) Carefully install the new cartridge into the housing. Avoid bumping the cartridge tubes against the

housing sealing flange. Seat the cartridge properly within the housing. Press all edges and corners of
the cartridge firmly with fingers to effect a positive air seal against the sealing flange of the housing.

(1).

Make certain it is free from all foreign material.

Caution: Under no circumstances should the cartridge be pounded or struck
in the center to effect a seal.

(2) Lock the cartridge in place by installing the baffle assembly

(8)

assembly

in place. Tighten clamp

(3)

down in place.

(7)

and clamp assembly

(3)

with cup

1. Body Assembly 5. Washer Gasket

2. “O” Ring 6. Wing Nut

3. Clamp Assembly 7. Baffle Assembly

4. Primary Element 8. Cup Assembly

November 18/91 Revised 2-1

Air Cleaner Cartridge Replacement

Figure 4

Page 5

OM-2031

6. Engine Fuel

A. Recommendations/Specifications

The quality of fuel oil used in the diesel engine is a major factor in engine performance and life. Fuel
oil must be clean, completely distilled, stable and non-corrosive. Use low sulphur content fuel having
a cloud point that is at least 10
temperature at which crystals begin to form in diesel fuel. The viscosity of the fuel must be kept
above 1.3 centistrokes to provide adequate fuel system lubrication.

WARNING ! Do not mix gasoline or alcohol with diesel fuel. This mixture can
cause an explosion.

Caution: Due to the precise tolerances of diesel injection systems, it is
extremely important that the fuel be kept clean and free of dirt or water. Dirt
or water in the system can cause severe damage to both the injection pump
and the injection nozzles.

Use ASTM No. 2D fuel with a minimum Cetane number of 40. No. 2 diesel fuel gives the best
economy and performance under most operating conditions. Fuels with Cetane numbers higher than
40 may be needed in high altitudes or extremely low ambient temperatures to prevent misfires and
excessive smoke.

At operating temperatures below 0
“winterized” No. 2D.

o

below the lowest expected fuel temperature. Cloud point is the

o

C(32oF), use a blend of No. 1D and No. 2D fuels, also known as

NOTE: No. 1D fuels can be used, but fuel economy wil be reduced.

Caution: Low viscosity fuel such as Jet-A fuel, will cause excessive wear on
the engine fuel pump and reduce its life expectancy unless lubricating oil is
added to the Jet A fuel.

Jet-A fuel - which is a low viscosity fuel - may be used, provided that lubricating oil is added to the
diesel fuel in the amount of 5% of the fuel mixture. Use one quart of lubricating oil per 5 gallons of Jet­A fuel.

B. Fuel Filter

Refer to Cummins Shop Manual in Chapter 6 for instructions on removal and replacement of fuel filter
elements.

7. Engine Cooling System

A. General

Cooling system device requires much more than maintaining the proper coolant level in the radiator.
During warm seasons and in warm climates, plain water can be used as a coolant if the system is
protected against rust by a rust inhibitor additive. During cold seasons and in cold climates, the
system must, of course, be protected against freezing. At no time should the system be operated for
any length of time on plain water, without a rust inhibitor or antifreeze. Draining, cleaning, and filling
the cooling system are covered in Para. 7, E through H.

2-1 November 18/91 Revised
Page 6

OM-2031

B. Radiator Cap

(1) General

A pressure valve is built into the radiator cap. It is designed to open at a pressure of
approximately seven pounds per square inch.

(2) Removal

WARNING ! Hot steam and fluids will severely burn! When removing cap
from a very hot radiator, do not turn cap past safety stop until all pressure or
steam has escaped. Use protective clothing. Allow engine to cool before
adding coolant.

To remove, turn the cap to the left
released, press down on the cap and continue to turn until the cap is free to be removed.

(3) Installation

When installing the cap be sure it is turned clockwise as far as it will go so that the pressure
retaining valve will be functional.

C. Warm Weather Operation

During warm weather operation, if water is used in the cooling system instead of an antifreeze
solution, keep the cooling system free of rust and sludge by adding a cooling system conditioner that
is compatible with aluminum. Instructions for u se of the conditioner are printed on each can.

(counterclockwise)

to the safety stop. When all pressure is

Caution: Use only a corrosion inhibitor that is compatible with aluminum. Do
not use inhibitors labeled as “acid neutralizer”.

D. Cold Weather Operation

(1) General

A permanent type,

(Ethylene Glycol)

antifreeze is recommended for use in the cooling system.

Caution: (a) Do not use “methanol” or alcohol as an antifreeze.

(b) Do not use two different types of antifreeze. Mixed solutions (two types)
make it impossible to determine if the cooling system has adequate
protection against freezing.

(2) Checking coolant solution

Check the solution frequently to be sure the cooling system has sufficient protection against
freezing.

NOTE: (a) When testing the solution, be sure the coolant is at operating temperature.
(b) Follow manufacturer’s instructions on tester.

November 18/91 Revised 2-1

Page 7

OM-2031

(3) Preparing the coolant solution

The following table
antifreeze to 65% antifreeze. Percentages are based on permanent type
antifreeze. Most antifreeze containers have a similar table printed on the label.

(4) Installing the antifreeze solution

Before installing antifreeze in the system, make the following checks:
(a) Check the system for signs of leaks.
(b) Inspect all hoses and tighten all hose clamps. Install new hoses if necessary.
(c) Drain and clean the system. Ref. Paras. 7,E and 7,F.
(d) Check the condition and tension of the fan and water pump belts and alternator belts. Replace

the belts if necessary.
(e) Be sure radiator and engine drain valves are closed, and all connections are securely

tightened.
(f) Install the required amount of antifreeze: 15.3 QUARTS. Fill the system with coolant as

outlined under Para. 7, H.

FREEZING POINT PERCENTAGE OF ANTI­(FAHRENHEIT) FREEZE IN SOLUTION

20 16%
+10 25%
0 33-1/3%

-10 40%

-20 45%

-30 50%

-40 54%

-50 58%

-60 62%

-70 65%

(Figure 5)

indicates the freezing points of solutions varying from 16%

(Ethylene Glycol)

Antifreeze Solution Table

Figure 5

E. Draining the Cooling System

Drain the cooling system immediately after stopping the engine, while most of the sediment is in
suspension. Proceed as follows:

(1) Remove radiator cap.
(2) Open radiator drain valve

Manual for exact locations of engine coolant drain valves.

NOTE: When draining the system for storage, remove all drain valves and remove drain plug.

(3) Allow the system to drain completely.

NOTE: Be sure the drain valves do not plug-up during draining.

(4) When the system is completely drained, close all drain valves except when draining for storage.

2-1 November 18/91 Revised
Page 8

(at bottom of radiator)

and engine drain valves. See John Deere Shop

F. Cleaning the Cooling System

Drain and thoroughly flush the cooling system twice a year or more often if necessary. The
appearance of rust in the radiator, or in the coolant is an indication that the inhibitor has become
weakened and it is possible that some sludge has accumulated in the system. When this condition
exists, proceed as follows:

(1) Run the engine until it reaches normal operating temperature; then stop the engine and drain the
cooling system

(Ref. Para. 7, E).

OM-2031

(2) Fill the cooling system with clean coolant
(3) Add a flushing compound, that is compatible with aluminum, to the cooling system in accordance

with the instructions furnished with the compound.

(4) Start the engine and flush the system as directed by the instructions furnished with the compound.
(5) After the system has been flushed and thoroughly cleaned of the c ompound, refill the clean

coolant

G. Cleaning the Radiator Core

Blow out insects and dirt from the radiator core air passages, using air or water under pressure.
Engine overheating is often caused by bent or clogged radiator fins. When straightening bent fins, be
careful not to injure the tubes or to break the bond between the fins and tubes.

H. Filling the Cooling System

Add a cooling system corrosion inhibitor

(Ref. Para. 7, H).

the air temperatures expected are at freezing,+32 deg F or lower).

desired. See Fig. 3 for cooling system capacity.

(1) Engine must be STOPPED. Close all drain valves except top water outlet valve. Leave this valve
OPEN to allow air to escape.

(2) Pour coolant into radiator slowly until system is filled to level of top drain valve. Close valve and

continue to fill system until coolant reaches a level approximately 1 inch below the radiator filler neck.

(Ref. Para. 7, H).

(for warm weather operation)

Antifreeze may be premixed if

or permanent antifreeze

(when

NOTE: If antifreeze solution is not premixed, pour required antifreeze in first. Install corrosion inhibitor
according to directions on container.

(3) Start the engine and allow it to idle. Add coolant if trapped air escapes from the system and the
coolant level falls.

(4) Continue to check coolant level until the engine reaches operating temperature. Add coolant, if
needed, to fill to the required level, 1 inch below filler neck. Install radiator cap.

NOTE: It is good practice to attach a card, indicating the cooling system contents, and the date serviced
to the radiator filler neck.

November 18/91 Revised 2-1

Page 9

OM-2031

8. Generator Maintenance

The 400-Hz generator requires no maintenance or service other t han periodic cleaning. The unit is
brushless, and bearings are permanently lubricated and sealed.

WARNING ! Electric shock and fire can kill or injure! BE sure the unit is
completely dry before operating. Do not use a flammable solvent.

A. Cleaning

The generator may be cleaned by careful use of compressed air and/or a good, SAFE commercial
cleaner. Steam cleaning of the generator is no longer recommended because the use of steam and
harsh chemical compounds may result in damage to insulation and other generator components.

B. Adjustment

The generator itself requires no adjustment. Adjustment procedures for generator controls will be
covered in Section 2-3.

9. Drive Belts

Twin belts from the crankshaft pulley are used to drive the alternator and water pump. For proper engine
operation these belts should be in good condition and at proper tension at all times.

A. Checking Belt Tension

Check belt tension every 200 hours of engine operation, or biweekly. Belts which are too tight are
destructive to bearings of the alternator and water pump. A loose belt will slip and cause inefficient
operation of the alternator and/or the water pump.

To check belt tension, press each belt firmly with the thumb at a point halfway between the alternator
pulley and the crankshaft pulley. A properly adjusted belt should deflect about 3/8 inch.

B. Belt Adjustment

To adjust belt tension, loosen the alternator mounting bolts and change the position of the alternator.
Upon obtaining the correct tension, re-tighten both alternator mounting bolts.

When new belts are fitted, it is necessary to run the engine for a short period to allow the new belts to
settle into the grooves of the pulleys and thus show any initial stretching that is going to occur.
Recheck belt tension after running the engine and adjust as necessary. Twin drive belts should be
changed in pairs.

10. Trailer, Truck and Battery Maintenance

If the generator set comes with either the trailer or truck option, refer to Chapter 5 for the number of the
manual which covers the particular option. The manual referred to will provide the appropriate
maintenance procedure. Both manuals cover battery maintenance, as, when either option is used, the
batteries are installed within it.

2-1 November 18/91 Revised
Page 10

11. Service Helps

A. Wiring

All small wire leads are routed through plastic flexible conduit which protects them and makes a neat
easily removable and replaceable wiring harness arrangement. This wiring method allows the
replacement of a single wire lead with a minimum of difficulty. All wires are color coded.

B.Control Box Trays

Control box trays may be removed easily and moved to a work bench for service or replacement of
parts.

(1) Tray removal

OM-2031

(a) Loosen screw-lock fastener
(b) Slide tray outward and disconnect Amphenol connector
(c) Support tray with hands at each side of tray near latches

down with thumbs, then slide tray out of box.

(2) Tray installation

(a) Use both hands to support tray as in removal above.
(b) Align rails
(c) Connect Amphenol connector

(4)

with tracks

(2, Fig. 6)

(5)

and slide tray into box. Latches will lock automatically.

(3).

(3).

(1).

Unlock latches

(1)

by pressing

1. Latch

2. Fastener

3. Connector

4. Rail

5. Track

November 18/91 Revised 2-1

Tray Removal (Typical)

Figure 6

Page 11

OM-2031

C. Generator Exciter

Provisions have been made to allow removal of the generator exciter without disturbing or removing
the complete generator.

(1) Preparation for exciter removal.

(a) Remove main frame rear cross member by removing four attaching cap screws

(2) Exciter removal

RefertoTM-360inChapter6forexciterinstructions.

(3) Exciter installation

(a) Install exciter in accordance with TM-360.
(b) Reinstall rear frame member and tighten screws securely.

(See Fig. 7).

NOTE: It may be necessary to use a large “C” clamp or other arrangement to position frame side rails
and align rear frame member mounting holes.

2-1 November 18/91 Revised
Page 12

Removable Rear Frame Cross-Member

Figure 7

D. Engine Control Panel

The engine control panel is designed and mounted in such a manner that it may be released from its
mounted position and tilted outward for access to components mounted on the back side
Do not disconnect the wires.

(1) Tilt out engine control panel

(a) Remove clamp screw which supports wire conduit above output terminal panel.
(b) Remove four cap screws which attach engine control panel to frame superstructure.
(c) Maneuver panel to tilt it inward at the bottom and outward at the top.

(2) Reinstall engine control panel

(a) Maneuver panel into position and align mounting holes. Install mounting screws and secure.
(b) Secure wire conduit in its original position with clamp and screw.

(see Fig. 8).

OM-2031

November 18/91 Revised 2-1

Engine Control Panel in Tilt-out Position

Figure 8

Page 13

OM-2031

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2-1 November 18/91 Revised
Page 14

SECTION 2. INSPECTION/CHECK

1. General

This section describes inspections and checks to be performed in conjunction with Inspection/Check

Schedule, Figure 1.

2. Engine

A. Fuel (See Fig. 1 for time schedules)

(1) Check fuel quantity DAILY.
(2) Drain fuel filters and change fuel filter elements in accordance with instructions in Cummins Shop

Manual.

(3) Open fuel tank drain every 500 hours to drain off water and sediment.

B. Lubrication

OM-2031

(1) Check crankcase oil level DAILY.
(2) Lubricate in accordance with Lubrication Chart

C. Coolant

(1) Check coolant level DAILY.
(2) Inspect for signs of rust and corrosion. Change coolant if rust and sediment are present. See 2-1;

Para.7,E,F,andH.

(3) Inspect hoses for cracks and deterioration. Inspect clamps for tightness.

D. V-Belts

(1) Inspect V-belts for proper tension and adjust if necessary after each 200 hours of operation.

2-1; Para. 7, A, B, and C.)

E. Exhaust System

(1) Visually inspect muffler and exhaust pipes for signs of approaching failure.
(2) Listen for any gasket or joint leaks.

(Ref.2-1;Fig.3).

(See

August 5/89 Revised 2-2

Page 1

OM-2031

Bi- Bi­Daily Weekly Weekly Monthly Monthly 6 Mo.
or or or or or or

AR 8 Hrs. 50 Hrs. 100 Hrs. 200 Hrs. 400 Hrs. 1200 Hrs.

ENGINE

Check fuel quantity X
Check crankcase oil level X
Check coolant level X
Change engine oil filter
element X
Change engine oil X
Replace air cleaner cartridge X
Inspect cooling system hoses,

tubes, fittings & clamps X
Check V-belt tension X
Drain/refill cooling system TWICE ANNUALLY
Change fuel filter elements X
Lubricate SEE LUBRICATION CHART
Check exhaust system X
Open fuel tank drain EVERY 500 HRS.

ELECTRICAL

Check all lights X
Clean battery terminals X
Check wiring X
Check connections X

400 Hz GENERATING AND CONTROL SYSTEM

Check output cable &
connector X
Check voltmeter X
Check ammeter X
Check frequency meter X
Check all lights X
Check protective relays X
Check safety switches X
Inspect all wiring &
connections X
Clean & inspect generally X

Inspection/Check/Maintenance Schedule

Figure 1

2-2 August 5/89 Revised
Page 2

(3) Replace any defective parts at once.

WARNING: EXHAUST FUMES OR FIRE CAN KILL OR INJURE! IMMEDIATELY
REPAIR DEFECTIVE EXHAUST SYSTEMS.

3.Electrical System (12-V DC)

A. Lights

OM-2031

Check all lights for proper operation DAILY. Replace any defective lamps
Figure 2 lists ALL lamps, their location, and part numbers.

B. Fuses

Check and replace fuses as required. See Figure 3 for fuse sizes and locations. Figure 3 includes all
fuses used in both the engine and generator electrical systems.

(bulbs)

as soon as discovered.

Light Lamp Lamp
Identification Location Manufacturer Number

Instrument Panel Control Box Lamp Industry 63
Lights Trade No.

Engine ON Indicating Engine Control LampIndustry 1815
Light Panel Trade No.

Contactor CLOSED Engine Control Lamp Industry 1815
Indicating Light Panel Trade No.

Fault Indicating Protective Relay Lamp Industry 1815
Lights Tray Trade No.

Clearance Lights Canopy Lamp Industry 57

C. Wiring and Connections

(1) Inspect all cables and leads for broken, worn, and damaged insulation.

August 5/89 Revised 2-2

Lamp Identification Chart

Figure 2

Page 3

OM-2031

(2) Check electrical connections for looseness.

NOTE: A darkened terminal generally indicates a loose connection.

4. Electrical System (115-V AC)

The 400-Hz generator and controls are designed to be as maintenance free as possible. No lubrication is
necessary and no periodic maintenance adjustments are required. However, some regular checks should
be made to be sure all controls, instruments, etc., are working properly.

A. Monitoring Instruments
Observe operation of voltmeter, ammeter, and frequency meter each time the unit is started.

Item Protected Location Illustration Size & Type

Instrument panel Engine control Sect. 1-1, Fig.9, 10A Type AGC
lights & engine panel item 13
circuit

Protective relay Protective relay Sect. 1-1, Fig.8, 2A Type AGC
system tray item 17

Voltage regulator Voltageregulator Sect. 1-1, Fig. 10, 5A Type AGC

item 12

Load contactor Protective relay Sect. 1-1, Fig. 8, 2A Type AGC
circuit tray item 16

Fuse Identification Chart

Figure 3

B. Indicating Lights

Check lamps
relay tray may be tested by pressing test switch

C. Protective Modules

Check operation of all protective modules to make certain they will function if a fault should occur in the
output circuit.

D. Wiring and Connections

(1) Check all cables, leads, and wiring for broken, worn, and damaged insulation.

(bulbs)

(See 2-3; Para. 3, B.)

in all of the indicating lights at each start up. Fault indicating lights in the protective

(1-1; 8, Fig. 8)

(2) Check all connections for tightness.

WARNING: STOP OPERATIONS AND STOP ENGINE BEFORE TOUCHING EX­POSED CONDUCTORS OR TERMINALS.

2-2 August 5/89 Revised
Page 4

(3) Check the output cable plug connector for damaged contactors in the end of the plug.

5. Trailer and Truck

If the generator set comes with either the trailer or truck option, refer to Chapter 5 for the number of the
Hobart manual which covers the particular option. The manual referred to will provide the appropriate in­spection procedure. Both manuals cover batteries, as, when either option is used, the b atteries are in­stalled within it.

OM-2031

August 5/89 Revised 2-2

Page 5

OM-2031

This page intentionally left blank

2-2 August 5/89 Revised
Page 6

SECTION 3. ADJUSTMENT/TEST

1. General

Adjustment and test procedures are most applicable to testing and adjusting the generator set after a ma-

jor repair, replacement of parts, or overhaul.

2. Generator Set Test

A. Pre-operational Test Procedures

(1) Connect cables from the generator output terminals to a load bank. Use cables of the same size

and length as those to be used in service. Be sure the generator output “N” cable is grounded.
(2) Check engine oil level. Oil should be at FULL mark on gage rod.

OM-2031

(3) Check radiator coolant level
(4) Check tension of fan and generator V-belts.
(5) If governor throttle linkage was disturbed, check all linkage to make certain engine speed may be

controlled when the engine is started.

(6) Inspect for oil, fuel, and coolant leaks.
(7) If the setting of the voltage regulator rheostat

tor)

has been disturbed, set it at CENTER position

(Ref. Section 2-1, Para. 7, H).

(See TM-759 or OM-2020 for your particular regula-

(halfway between full clockwise position and full

counterclockwise position).

(8) Check engine circuit fuse

(13)

lights
(9) Check fault indicating lights

lamps are good.
(10) Make a general inspection of all wiring and terminals. Inspect the equipment to be certain no

damage will result from starting the engine.
(11) At initial start-up after generator overhaul or repair, “flash” the exciter field by momentarily apply-

ing 12-V DC to the field windings as follows:

CAUTION:ENGINE MUST NOT BE RUNNING WHEN FLASHING FIELD IF VOLTAGE REGULATOR
DAMAGE IS TO BE PREV ENTED.

operate, the fuse

(a) Flashing exciter field using test box.

(26, Fig. 1)

(26),

switch

(9)

by placing panel light switch

(16),

by pressing test switch

and lamps are good.

(8).

If lights glow, fuse

(16)

in ON position. If panel

(11)

and indicating

If a test box

(see Sect. 1-3, Fig. 3)

4).

(aa) Rotate the selector knob
(bb) Use two jumper leads, each equipped with an alligator clip and a test prod, to connect

12-V DC power to test jacks
minal on starter solenoid to red test jack. Connect negative lead from starter ground terminal
to black test jack.

(cc) Momentarily pressing pushbutton switch
field.

August 5/89 Revised 2-3

is available, connect it to receptacle connector

(Sect. 1-3, Fig. 3, item 1)

(2 and 3)

on the test box. Connect positive jumper from input ter-

(Sect.1-3,Fig.3,item2)

to position 8.

will flash the exciter

(Sect. 1-3, Fig.

Page 1

OM-2031

(dd) Disconnect jumper leads.

(b) Flashing exciter field without test box.

(aa) Remove test receptacle cover

on one end and an “alligator” clip on the other. Insert the test prod of one lead in terminal “D”
of the test receptacle
Insert the test prod of the second lead in terminal “F” of the test receptacle and momentarily
touch the other end

CAUTION: FLASHING THE FIELD IN A REVERSE DIRECTION COULD CAUSE DAMAGE TO
VOLTAGE REGULATOR DIODES.

(see Fig. 1),

(alligator clip)

(1-3; Fig. 4).

and connect the other end of the lead to a good GROUND.
to the “hot” terminal on the starter solenoid to flash the field.

Use two test leads equipped with a test prod

NOTE: If test leads with test prods are not available, insert short pieces of wire in proper test terminals
to make connections.

(bb) Disconnect leads and install receptacle cover.

(12) Check position of load contactor “on-off” switch

(18).

(a) Load contactor switch
(b) Engine-generator control switch

(20)

must be in OFF position.

(18)

must be in IDLE position.

(20, Fig. 1),

and engine-generator control switch

2-3 August 5/89 Revised
Page 2

OM-2031

1. Frequency meter 17. DC Ammeter

2. Voltmeter 18. Engine-generator control switch

3. Fastener 19. Hourmeter

4. AC Ammeter 20. Load contactor control switch

5. Meter switch 21. Coolant temperature gage

6. Line switch 22. Load contactor indicating light

7. Reset switch 23. Oil pressure gage

8. Light test switch 24. Cold weather starting aid control

9. Fault indicating lights 25. Air cleaner indicator

10. Load contactor circuit fuse (2-A) 26. Engine circuit fuse (10-A)

11. Protective system fuse (2-A) 27. Engine protective circuit

12. Protective relay tray indicating light

13. Instrument panel light 28. Engine starter switch

14. Generator control tray 29. (Deleted)

15. Fuel gage 30. Permissive start switch

16. Light switch 31. Test receptacle connector

Operating Controls and Instruments

Figure 1 (Sheet 1 of 2)

August 5/89 Revised 2-3

Page 3

OM-2031

2-3 August 5/89 Revised
Page 4

32. Manual voltage control rheostat

33. Automatic-manual voltage
control switch

34. Test bank switch

35. Light test switch

36. Reset switch

Operating Controls and Instruments

Figure 1 (Sheet 2 of 2)

Test Receptacle Connector Terminals Identification

Figure 2

OM-2031

B. Operational Test Procedures

(1) Start the engine in accordance with instructions in 1-3; Para. 2, A thru C.
(2) Check operation of engine instruments: DC ammeter

(21),

oil pressure gage

(3) Check engine idle speed. Should be 825 to 875 RPM. Adjust, if necessary, in accordance with in­structions in Engine Operator’s Manual.

(23),

and hourmeter

(19).

(17, Fig. 1),

coolant temperature indicator

NOTE: A stroboscope is required for this check.

(4) Again check for oil, fuel, and coolant leaks and correct any leaking condition.
(5) Position switches and controls for automatic voltage regulation and power delivery as follows:

(a) Place automatic-manual switch
(b) Place test-bank switch
(c) Meter switch
(d) If the adjustment of the voltage regulator rheostat

turbed, position the knob to mid-range position.

(6) Bring the engine up to governed speed and also energize the generator by holding the engine-gen­erator control switch
position in “center” RUN position.

(5)

(18)

(34)

may be in any position except pointing straight down.

in BUILD-UP-VOLTS position momentarily. Release switch and allow it to

(33, Fig. 1)

in AIRCRAFT position.

in AUTOMATIC position.

(See TM-759/OM-2020)

has been dis-

If the engine “comes-up” to governed speed and a voltage value appears on the voltmeter
electric governor and excitation deenergization relay circuits are functioning.

(7) Observe frequency meter
Hz. If not, adjust engine governed speed. See Fig. 8.

(8) Observe voltmeter

August 5/89 Revised 2-3

(1).

If engine speed is properly adjusted, frequency will be exactly 400

(2).

Use rheostat to adjust voltage to 115 V AC.

(2),

the

Page 5

OM-2031

(9) Measure governor actuator input signal. See Par. 3, E,
(10) Measure governor magnetic pickup signal. See Para. 3, E,
(11) Check speed limiting governor

Set engine speed-limiting governor to 2300 + 25 RPM. See John Deere Diesel Handbook in
Chapter 6 for instructions on how to set the governor.

(12) Check adjustable voltage range in automatic operating mode.

(a) Observe voltmeter

age should be at least 134 V AC, or higher.

a

nd turn rheostat CLOCKWISE to full clockwise position. Maximum volt-

(4), (a).

(4), (b).

NOTE: If voltage should decrease w hen the knob is turned clockwise, it indicates that internal wiring of
the voltage regulator is incorrect. Replace the complete regulator tray assembly.

(b) Observe voltmeter and turn rheostat knob to full COUNTERCLOCKWISE position. Minimum
voltage should be 108 V AC, or lower.

(13) Observe voltmeter and adjust rheostat to obtain 115-V AC voltmeter reading.
(14) Check adjustable voltage range in manual operating mode.

(a) Open the generator control tray
MANUAL position.

(14, Fig. 1)

and place the automatic-manual switch (33) in

(b) Observe voltmeter
sition. Maximum voltage should be at least 160 V AC.

(c) Observe voltmeter and turn rheostat
voltageshouldbe95VACorless.

(d) Adjust voltage to 115 V AC, then return the automatic-manual switch to AUTOMATIC position.
(15) Position load bank switches, etc., to apply a light load to the generator.
(16) Place the load contactor “on-off” switch

Hold in this position momentarily. Hold in this position momentarily. The indicating light
glow GREEN and an amperage value should appear on the AC ammeter

(17) Release the switch
open immediately, and the generator “on” indicating light should go OFF. This is because the plug in­terlock relay
that the plug interlock contacts are OPEN as they should be when the interlock coil is not receiving 28­V DC power.

(18) Open the protective relay tray and place the test bank switch
(19) Again place the load contactor switch

GREEN and remain ON when the switch is released and allowed to return to the center ON position.

This indicates that the test bank switch
(20) Return the test bank switch to AIRCRAFT position. The load contactor should open at once and

the green indicating light
(21) Connect a source of 24-V DC power

“N” and “F”
and PLUS to terminal E or F.

(Ref.1-1;1,Fig.8)

(or “E”)

at the output terminal panel. Connection polarity should be: MINUS to terminal N

(2)

and turn manual control rheostat

(32)

to full COUNTERCLOCKWISE position. Minimum

(20, Fig. 1)

in the top, spring loaded, CLOSE position.

(32)

CLOCKWISE to full clockwise po-

(22)

should

(4).

(2)

and allow it to return to the center ON position. The load contactor should

is not receiving power from an outside source of 28 V DC. It indicates

(22)

should go off.

(34, Fig. 1)

(20)

in the top, CLOSE position. Light

(34)

is functioning to by-pass the plug interlock relay.

(two twelve-volt batteries connected in

in TEST BANK position.

(22)

should glow

series) to terminals

(22) With test-bank switch in AIRCRAFT position, hold the contactor operating switch
CLOSE position momentarily. The generator “on” indicating light

2-3 August 5/89 Revised
Page 6

(20)

(22)

should glow GREEN and re-

in top,

OM-2031

main on when the switch is released and allowed to return to the center ON position. This indicates

that the load contactor is closed and the plug interlock relay is functioning properly.

(23) Apply 1/3 to 1/2 load at the load bank and allow the unit to run for 15 to 30 minutes. Observe op-

eration of all monitoring instruments.

(24) Increase load bank resistance to apply a full load.

(25) Check operation of the governor by observing the frequency meter

switched from no-load to full-load and vice versa. Use the contactor control switch

remove load several times. Frequency drop should be no more than 1 Hz. Adjust governor if neces-

sary

(seePara.4,E,(3)).

(26) Follow instructions in Para. 4, B,

ometers. Set knob pointer on cable size potentiometer to size

knob pointer on cable length potentiometer to length

instruction plate (mounted below knobs).

(27) Check voltage regulator, at intervals, from no-load to full load, and on up to 125% load. Observe

and note voltage at various loads. Voltages should vary no more than plus or minus 1% from 115 V.

(28) Check accuracy of voltmeter.

(a) Open generator control tray
(b) Connect a master voltmeter of known accuracy to terminals of the voltmeter
(c) Compare unit voltmeter reading with master meter. Error must not exceed 2% of full scale.

(29) Check accuracy of AC ammeter.

(a) Connect a master ammeter of known accuracy to the AC ammeter
(b) Compare unit ammeter reading with master meter under various loads. Error must not exceed

4% of full scale.

(30) Check operation of meter selector switch

sition.

(2) (b)

to set voltage regulator line drop compensation potenti-

(14, Fig. 1).

(2/0, 4/0, etc.)

(20 feet, 40 feet, etc.)

(5).

A voltage value should be shown in each switch po-

(1, Fig. 1)

of cable being used. See

when generator is

(20)

to apply and

of cable being used. Set

(2).

(4)

terminals.

(6).

(31) Check operation of the line switch

theswitchisinLINE-TO-NEUTRAL position. A voltage of approximately 200 V AC should be indi-

catedwhentheswitchisplacedinLINE-TO-LINE position.

(32) Check accuracy of frequency meter.

(a) Connect a master frequency meter of known accuracy to the frequency meter
(b) Compare meter readings. Error must not exceed 1% of full scale.

(33) Operate the unit not less than 10 minutes under full load. The overload device

MUST NOT trip.

11)

(34) Operate at 125% rated load for 5 minutes immediately following the full load run. The overload

device MUST trip within 5 minutes and the overload indicating light

cate an overload condition.

(35) Reduce load to normal. Turn off indicating light by pressing reset switch

August 5/89 Revised 2-3

A normal voltage of 115 V AC should be indicated when

(1)

terminals.

(Ref. 1-1; 7, Fig.

(9, Fig. 1)

must come ON to indi-

(7, Fig. 1).

Page 7

OM-2031

(36) Check engine oil pressure at governed speed

when the engine is hot. Check engine coolant temperature. Gage should indicate in the range of 180
degrees to 190 degrees depending upon ambient temperature.

(37) Check operation of fuse interlock
move protective relay circuit fuse
indicates that the fuse interlock relay is functioning properly. Replace fuse and apply load.

(Ref.1-1;2,Fig.8).

(Ref. 11, Fig. 1).

(2000 RPM).

The load contactor should open immediately. This

Gage should indicate at least 38 PSI

With unit operating normally under load, re-

NOTE: Make all protective relay tests with the unit operating under load.

(38) Check operation of overvoltage relay and indicating light.

(a) With the unit running at normal load, adjust the voltage regulator rheostat to increase voltage

(turn clockwise)

load contactor and turn on the overvoltage indicating light. The overvoltage sensing relay should

trip when voltage reaches 130 V to 134 V.

(b) Return unit to normal operating conditions by adjusting voltage regulator rheostat and press-

ing reset switch
(39) Check operation of undervoltage sensing relay, indicating light, and time delay. Before starting

this check, let us understand the sequence of events which should happen when voltage is reduced
to 103 V or lower. At some value between 103 V and 93 V, the undervoltage sensing relay

5, Fig. 8)

delay circuit is activated,
tive monitor relay which, in turn, will open the load contactor to stop power delivery. As a result of the
action, the undervoltage indicating light
watch is required for this check. Proceed as follows:

should function to activate the undervoltage time delay circuit. Five seconds after the time

until the over-voltage sensing relay actuates the protective monitor to open the

(7).

(if the undervoltage condition continues)

(9)

should be turned ON. A stopwatch or sweep-second-hand

it should function to open the protec-

(Ref. 1-1;

(a) With unit running at normal load, use the voltage regulator rheostat to reduce voltage to 104V.

The load contactor should NOT open after a 5-second delay.

(b) Reduce voltage in steps of 1 V, with a delay of at least 5 seconds between steps. Restart stop-

watch or note position of sweep-secondhand each time voltage is reduced. At some voltage value

between 103 V and 93 V, and 4 to 12 seconds after a new voltage setting is made, the load con-

tactor should be opened and the undervoltage indicating light should be turned on by the step-by-

step action of the undervoltage sensing relay, time delay circuit, and protective monitor relay.

NOTE: 1. The 4 to 12 second time delay is generally set at 5 seconds.

2. It may be necessary to switch to MANUAL control to obtain these low voltages.

(c) If the load contactor is not opened at 103 V to 93 V, it will be necessary to refer to the Trouble

Shooting Chart, Section 3-1, to determine which component of the undervoltage protective circuit

is defective.

(d) If the undervoltage circuit performs satisfactorily, return the unit to normal operation by adjust-

ing the voltage to 115 V, pressing the reset switch, and closing the load contactor.
(40) Check underfrequency sensing relay, protective monitor, and indicating light. At some frequency

value

(Hz, cycles-per-second)

function to signal the underfrequency circuit in the protective monitor module to OPEN the load con­tactor holding circuit, thus OPENING the load c ontactor. To check the underfrequency protective com­ponents, proceed as follows:

from 385 Hz down to 375 Hz, the underfrequency sensing relay should

2-3 August 5/89 Revised
Page 8

OM-2031

(a) While the unit is operating normally under load, reduce generator output frequency by reduc­ing engine speed. Use the governed speed setting potentiometer. Turn adjusting screw COUN-
TERCLOCKWISE gradually to reduce engine speed until frequency meter indicates 386 Hz.
Underfrequency protective relay should not function to open the load contactor at this frequency.
Reduce frequency in steps of 1 Hz.

(b) If the protective system functions to open the load contactor and turn on the underfrequency
light after some frequency between 385 Hz and 37 Hz is reached, all components of the system
are functioning properly. If the load contactor is not opened within the above frequency range, re­fer to Trouble Shooting Chart to determine which component is defective.

(c) Return unit to normal operating condition.

(41) Check overfrequency sensing relay, protective monitor, and indicating light. This protective circuit

operates in exactly the same manner as the underfrequency circuit except its operating range is from

415 Hz to 425 Hz. Its purpose also is to open the load contactor and turn on an indicating light.

(a) Check procedures are the same for overfrequency as for underfrequency
engine speed is INCREASED to create a condition of overfrequency.

(b) If the overfrequency system functions to open the load contactor and turn on the overfre­quency light after some frequency between 415 Hz and 425 Hz is reached, all components of the
system are functioning properly. If the load contactor is not opened within the above frequency
range, refer to Trouble Shooting Chart to determine which component is defective.

(42) If the generator is operating under load at this point, place the contactor control switch

in OFF position to open load contactor and disconnect load. There will be no further need for the

1)

load bank in the following checks.

(43) With the engine running at normal governed speed, check the entire unit for vibration and for any

parts which may have become loosened during the above checks. Tighten any loose attaching hard-

ware as required.

(44) Check 400-Hz generator bearings. Use a stethoscope or metal sounding rod to listen for unusual

noises. If using a metal rod, place one end on the generator housing and hold the other end near the

ear. Hold the rod with three fingers and use the index finger and thumb to form a “sounding chamber”

between the rod and the ear. Do NOT allow the rod to touch the ear. Listen for “grinding” or pounding

sounds which would indicate a defective bearing. An engine noise may be “telegraphed” to the gener-

ator and misinterpreted as a generator noise. Send the unit to overhaul if in doubt of bearing service-

ability.

(above)

except that

(20, Fig.

WARNING: ELECTRIC SHOCK, MOVING PARTS, AND NOISE CAN KILL OR
INJURE! IF A METAL SOUNDING ROD IS USED TO DETECT BEARING
NOISES, EXERCISE EXTREME CARE TO AVOID INJURY.

August 5/89 Revised 2-3

Page 9

OM-2031

3. Generator Set Adjustment

A. Generator Adjustment

The 400-Hz generator is a brushless type requiring no adjustments of any kind.

B. Generator Control Adjustments

The following items may require adjustment at some time during the life of the equipment.

(1) Adjust manual voltage control, variable resistor.
See TM-759 or OM-2020 for your particular Regulator.
(2) Adjust 400-Hz voltage regulator.
See TM-759 or OM-2020 for your particular Regulator.

C. Basic Engine Adjustments

Adjustment procedures applicable to the diesel engine are included in the John Deere Diesel Handbook
which accompanies this Hobart manual. Specific information for this particular engine is listed in Figure 6.

D. Engine Accessories Adjustment

(1) Generator and fan belt adjustment Refer to 2-1; Para. 8 for fan belt adjustment instructions.

NOTE: Replace fan belts as a matched set.

Manufacturer Cummins
Model 6BTA5.9
Type Turbocharged, In-line, 6-cylinder,

4-cycle Diesel
Displacement 359 cu. in. (5.88 liters)
Compression ratio 16.5 : 1
Firing order 1-5-3-6-2-4
Number of main bearings 7
Horsepower at 2000 RPM 167
Governed speed 2000 RPM
Idle Speed 850
Electrical System 12 volt
Oil capacity 17.3 QUARTS (16.4 LITERS)
Coolant capacity (approx.) 15.3 QUARTS (14.5 LITERS)
Fuel Diesel oil conforming to ASTM

Lube oil MIL-L-2014C or MIL-L-2014D

+

25 RPM

Specification D.975-66T,

Nos. 1-D and 2-D

+

4.5%

2-3 August 5/89 Revised
Page 10

Engine Specifications

Figure 3

OM-2031

E. Electric Governor System Adjustment

Two electric governor system main components, namely the magnetic pickup and controller, have critical
adjustments which can affect engine performance and therefore generator output. The adjustment of the
actuator linkage can also affect engine performance.

When the complete system is to be checked and/or adjusted, a definite sequence of procedures should
be followed:

First - Check or adjust actuator linkage
Second - Check or adjust magnetic pick-up
Third - Check or adjust electric control box

(1) Actuator linkage adjustment

The proper adjustment of the mechanical linkage between the electric actuator and engine speed

control lever is important to the satisfactory operation of the complete system.
Exact adjustment instructions regarding effective length of rod assembly

regarding the proper hole in actuator lever in which to attach ball joint
cause of slight variations in brackets, mountings, and engine performance characteristics. However,
definite rules must be followed in making the adjustments:

RULE 1. Adjust linkage to use FULL TRAVEL of actuator output shaft
RULE 2. Linkage must move speed control lever from FULL IDLE to FULL SPEED position, or

VERY CLOSE to FULL SPEED position in order for the generator to pull 125% load.

Check and adjust linkage as follows, with engine stopped.

(a) Before making adjustment, observe and note which hole in actuator lever

(4).

ball joint
Disconnect ball joint

(b) Be sure neither lever (the actuator lever, 3, or the fuel control lever) has slipped on shafts. If a
lever has slipped, position it correctly and tighten securely.

(c) Place both levers
hole in actuator lever
loosen nuts (5) and adjust effective length of rod assembly (4,5,6 and 7, Fig. 4) so that connec­tioncanbemade.

(d) Manually operate actuator lever back and forth between FULL IDLE and FULL SPEED. If ad­justment is unsatisfactory, try another hole in ACTUATOR lever and readjust rod length.

It does not necessarily have to be the same hole as may have been previously used.

(4)

from actuator lever

(3 and 7)

(3)

in FULL IDLE position an attempt to connect ball joint

fromwhichitwasremovedinstep

(3).

(a).

(items 4,5,6, and 7,Fig. 4),

(4)

cannot be determined be-

(1).

(3)

is used to mount

(4)

at the

If connection cannot be made,

or

(e) Tighten all parts securely when adjustment is completed.

August 5/89 Revised 2-3

Page 11

OM-2031

1. Actuator shaft 5. Nut

2. Signal input connector 6. R od

3. Actuator lever 7. Ball Joint, Fuel Control Lever

4. Ball joint, actuator

(2) Magnetic pickup adjustment

The strength of the magnetic pickup signal to the control box can be weakened if the tip of the pickup
is too far from the flywheel ring gear. If the pickup is to be removed for any reason, or if the signal is
weak

(less than 2.5-V AC)

rated speed, proceed as follows:

(a) Disconnect “pull-apart” connector
(b) Loosen nut
(c) Inspect to make certain the tip is not damaged from contact with the ring gear teeth, replace

pickup if damaged.

2-3 August 5/89 Revised
Page 12

(3)

and remove magnetic pickup

Governor Actuator Linkage

Figure 4

as indicated by a voltage test at the pick-up with the engine running at

(1, Fig. 5).

(2).

OM-2031

(d) Rotate the engine as required to locate a ring gear tooth directly below the tapped, pickup
mounting hole. An imaginary line should pass through the center of the mounting hole, the center
of a flywheel tooth and the center of the flywheel.

(e) Install the magnetic pickup into the tapped mounting hole and thread it in until the tip touches
the “in-line” flywheel gear tooth.

CAUTION: THE PICKUP

TIP MUST BE DIRECTLY OVER A TOOTH AND NOT BETWEEN TEETH

WHEN ADJUSTMENT IS MADE.

(f) Back the pickup outward

(3).

and tighten nut

This adjustment will result in a clearance of approximately 0.028 inch between

(counterclockwise)

1/2 turn. Hold the pickup securely in this position

the pickup tip and the flywheel teeth and give an operating AC voltage of 4 V to 8 V at controller
terminals 5 and 6 when the engine is running at no load and governed speed, and approximately

2.5-V at cranking speed.

NOTE: As little a 1-V is required for operation of governor control box. Magnetic pickup voltage does not

have

to be 4-V to 8-V.

August 5/89 Revised 2-3

1. Connector

2. Magnetic pick-up

3. Nut

Magnetic Pickup Adjustment

Figure 5

Page 13

OM-2031

(3) Adjustment and Test of Controller and Actuator

Refer to Figure 6. The controller has three identical control potentiometers See inset): the GAIN po­tentiometer, the DROOP potentiometer, and the potentiometer marked “I”. In addition, a SPEED con­trol potentiometer is located just next to the GAIN potentiometer. Make controller settings as follows:

(a) Preliminary Controller Settings

(1) With the engine of the generator set turned OFF,setthe“I” adjustment at the FOURTH in-

crement mark from zero.

(2) Set the GAIN adjustment at the THIRD increment mark from zero.
(3) Set DROOP adjustment COUNTERCLOCKWISE to minimum

Figure 6.
(4) Start the engine and adjust the controller’s SPEED potentiometer until engine is operating

at rated speed
and turning it COUNTERCLOCKWISE decreases engine RPM.

(b) Checking No-Load Operation of Controller

(1) Turn the GAIN potentiometer control slowly CLOCKWISE until the governor becomes un-

stable and the actuator lever

(2000 RPM)

. Turning the adjustment CLOCKWISE increases engine RPM

(3,Fig.4)

oscillates.

(If the actuator lever DOESN’T oscillate at

(zero)

position as shown in

this setting, upset the lever manually to cause it to oscillate).

(2) Next, turn the same GAIN potentiometer control slowly COUNTERCLOCKWISE until the
governor becomes stable and the oscillations cease.

(3) Turn the “I” potentiometer control slowly CLOCKWISE until the governor again becomes
unstable and the actuator lever

• If the governor DOES NOT become unstable and the lever DOES NOT oscillate, place “I”
potentiometer control setting at approximately EIGHT increment marks from zero

(3, Fig. 4)

oscillates.

(or TWO

increment marks from maximum setting).

• If the governor DOES become unstable, and the actuator lever DOES oscillate, turn the “I”
potentiometer control slowly COUNTERCLOCKWISE until the governor becomes stable
and the oscillations cease.

NOTE: For more accurate and dependable settings, when making GAIN and “I” adjustments, ALWAYS
adjust GAIN before adjusting “I”.

(c) Checking Operation of Controller Under Load

Apply a load to the generator set, then remove the load and observe the length of time re­quired for engine speed to again stabilize. Engine speed should stabilize within 3 to 5 dimin­ishing oscillations. If this does not happen, proceed as follows:

(1) With the generator set operating at no load, turn the GAIN setting slightly in the COUN­TERCLOCKWISE direction.

(2) Apply load again to the generator set. Then remove the load again and observe the length

of time required for engine speed to stabilize. It should now stabilize in 3 to 5 diminishing oscil­lations.

NOTE: If engine speed STILL doesn’t stabilize, recheck governor linkage. If linkage is set properly, the
governor controller is probably defective.

2-3 August 5/89 Revised
Page 14