Hobart 90CU24 Operation And Maintenance Manual

OM-2084

112797 Revised 10/98

Operation and Maintenance Manual

Model 90CU24 Generator Sets

Series 500392

Hobart Brothers Company

Ground Power Division

Troy, OH 45373

U.S.A.

WARRANTY

HOBART BROTHERS COMPANY, TROY, OHIO, U.S.A.

GROUND POWER DIVISION

1. Hobart Brothers Company (hereinafter called HOBART) warrants that each new and unused Hobart Ground

Power Equipment, (hereinafter called the PRODUCT) is of good workmanship and is free from mechanical defects, provided that (1) the PRODUCT is installed and operated in accordance with the printed instructions of HOBART, (2) the PRODUCT is used under the normal operating conditions for which it is designed, (3) the PRODUCT is not subjected to misuse, negligence or accident, and (4) the PRODUCT receives proper care,

lubrication, protection, and maintenance under the supervision of trained personnel.

2. This warranty expires 15 months after shipment by HOBART to the first user, or 12 months after installation,

whichever first occurs.

3. This warranty does not apply to: primary and secondary switch contacts, cable connectors, carbon brushes, fuses,

bulbs, and filters unless found to be defective prior to use.

4. Hobart DOES NOT WARRANT THE FOLLOWING COMPONENTS: Engines (gasoline or diesel),storage

batteries, engine starters generators, alternators, regulators, governors, tires, axles,transmissions,and cable retrieving devices. Many of the foregoingcomponents are warranted directly by the manufacturer to the first user and serviced by a worldwide network of distributors and others authorized to handle claims for component manufacturers. A first user’s claim should be presented directly to such an authorized component service outlet. In the event any component manufacturerhas warranted its component to HOBART and will not deal directly with a first user then HOBART will cooperate with the first user in the presentation of a claim to such manufacturer. Under NO circumstances does HOBART assume any liability for any warranty claim against or warranty work done by or in behalf of any manufacturer of the foregoing components.

5. This warranty is extended by HOBART only to the purchaser of new PRODUCTS from HOBART or one of its

authorized distributors. The PRODUCTS purchased under this warranty are intended for use exclusively by the buyer and his employees and by no other persons and, therefore, there shall be no third party beneficiary to this warranty.

6. A claim of defects in any PRODUCT covered by this warranty is subject to HOBART factory inspection and

judgment. HOBART’S liability is limited to repair of any defects found by HOBART to exist, or at HOBART’S option the replacement of the defective product, F.O.B.factory, after the defective product has been returned by the purchaser at its expense to HOBART’S shipping place. Replacement and exchange parts will be warranted for the remainder of the original Warranty, orfor a period of ninety (90) days, whichever is greater.

7. UNDER NO CIRCUMSTANCES whatsoever shall HOBART and its authorized distributors be liable for any special

or consequential damages, whether based on lost goodwill, lost resale profits, work stoppage impairment of other goods or otherwise, and whether arising out of breach of any express or implied warranty, breach of contract, negligence or otherwise, except only in the case of personal injury as may be required by applicable law.

8. Continued use of the PRODUCT(S) after discovery of a defect VOIDS ALL WARRANTIES.

9. Except as authorized in writing, this warranty does not cover any equipment that has been altered by any party

other than HOBART.

10. THERE ARE NO WARRANTIES WHICH EXTEND BEYOND THE DESCRIPTION ON THE FACE HERE OF.

HOBART MAKES NO WARRANTIES, EXPRESSED OR IMPLIED, OF ERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

11. HOBART neither assumes nor authorizes any person to assume for HOBART any liability in connection with the

PRODUCTS sold, and there are no oral agreements or warranties collateral to or affecting this written Warranty.

This warranty and all undertakings of HOBART thereunder shall be governed by the laws of the State of Ohio, United States of America.

AT ALL TIMES, SAFETY MUST BE CONSIDERED AN IMPORTANT FACTOR IN THE INSTALLATION,

WARNING

SERVICING AND OPERATION OF THE PRODUCT, AND SKILLED, TECHNICALLY QUALIFIED PERSONNEL

SHOULD ALWAYS BE EMPLOYED FOR SUCH TASKS.

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

Safety Warnings and Cautions

WARNING

IMPORTANT

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.

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

CALIFORNIA PROPOSITION 65 - DIESEL ENGINES. Diesel engine exhaust and some of its constituents are known to the State of California to cause cancer, birth defects and other reproductive harm.

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 to break load and prevent tools from causing short circuits.

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

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. Installation and Grounding of Electrically Powered Equipment

Equipment driven by electric motors 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.

November 27/1997 Safety Warnings

(rather than by diesel or gasoline engines)

must be installed

Page 1

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

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 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.

b. 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.

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.

(amperage)

b. Lock switch OPEN 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.

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.

a. 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.

b. 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.

c. 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.

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.

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.

(or remove line fuses)

so that power cannot be turned on accidentally.

Safety Warnings November 27/1997 Page 2

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

7. 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

Equipment Precautionary Labels

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

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.

November 27/1997 Safety Warnings

Page 3

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

This page intentionally left blank.

Safety Warnings November 27/1997 Page 4

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

Introduction

This manual contains operation and maintenance information for a Hobart generator set manufactured by Hobart Brothers Company, Ground Power Division, 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 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 five 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: “ Paragraph 1.a. If a chapter and section are not indicated in a reference, the referenced material is located in the same section as the reference, for example: “

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 5.

Appendix A contains a list of options and corresponding TO documents. If the machine purchased contains one of these options, the corresponding TO will be inserted in this section.

Content of the manual is arranged as follows:

Chapter 1. Description/Operation Chapter 2. Servicing/Troubleshooting Chapter 3. Overhaul/Major Repair Chapter 4. Illustrated Parts List Chapter 5. Manufacturer’s Literature Appendix A. Options / Features

(see Section 2-3, Paragraph 1.a.)

” refers to information located in Chapter 2, Section 3,

(see Paragraph 1.a.).

”

Introduction November 27/1997 Page 1

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

This page intentionally left blank.

November 27/1997 Introduction

Page 2

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

Table of Contents

Chapter-Section Page

Chapter 1. Description / Operation

Section 1. Description 1-1 1

General 1-1 1 Orientation 1-1 1 Optional Equipment 1-1 1 Special Features 1-1 1

Protective Monitor 1-1 1 Voltage Regulator 1-1 1 Electric Governor 1-1 1

Canopy 1-1 1 Engine, Generator, and Control Box 1-1 4

Basic Engine 1-1 4 Engine Manufacturer’s Equipment 1-1 4 Engine Cooling Fan 1-1 6 Occasional Engine Faults 1-1 6 Hobart Installed Engine Equipment 1-1 7 Generator 1-1 8

Control Box Assembly 1-1 9

Power Module Panel Assembly 1-1 18

Section 2. Preparation for Use, Storage or Shipping 1-2 1

Preparation for Use 1-2 1

Inspection/Check 1-2 1 Installing Three-phase AC Output Cables 1-2 2

Preparation for Storage 1-2 3

General 1-2 3 Temporary Storage 1-2 3 Long Time Storage (Over 30 Days) 1-2 3 Preparation for Shipment 1-2 4

November 27/1997 Table of Contents

Page 1

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

Section 3. Operation 1-3 1

General 1-3 1 Operating the Unit 1-3 1

Pre-start inspection 1-3 1 Normal Engine Starting Procedures 1-3 1 Failed Starting Procedures 1-3 4 Power Delivery 1-3 4 Discontinue Power Delivery with Unit Shutdown 1-3 5

Chapter 2. Servicing

Section 1. Maintenance Inspection/Check 2-1 1

General 2-1 1 Maintenance Schedule 2-1 1

General 2-1 1 Maintenance Schedule Check Sheet 2-1 1 Time Intervals 2-1 1 Identification of Interval Periods 2-1 1

Inspection/Check 2-1 4

General 2-1 4 “AR” Checks and Operations (As Required) 2-1 4 “BR” Checks and Operations (Break-In Period) 2-1 4 “A” Checks and Operations (10 Hours or Daily) 2-1 5 “B” Check and Operations (250 Hours or 3 Months) 2-1 7 “C” Checks and Operations (500 Hours or 6 Months) 2-1 7 “D” Checks and Operations (1000 Hours or 1 Year) 2-1 8 “E” Checks and Operations (1500 Hours or 1 ½ Years) 2-1 8 “F” Checks and Operations (2000 Hours or 2 Years) 2-1 10 Seasonal Maintenance Checks (Engine) 2-1 11 Lamps and Circuit Breakers 2-1 12

Section 2. Maintenance Procedures 2-2 1

General 2-2 1 Lubrication 2-2 1

General 2-2 1 AC Generator 2-2 1 Generator Controls 2-2 1 Engine 2-2 1 Engine Accessories Lubrication 2-2 5

Servicing the Air Cleaner 2-2 6

Inspecting the Air Cleaner 2-2 6 Changing the Air Filter 2-2 6 Disposal 2-2 6

Table of Contents November 27/1997 Page 2

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

Engine Fuel 2-2 7

How to Select Fuel—Quality 2-2 7 Cold Weather Operation 2-2 7

Engine Fuel System 2-2 7

Fuel Tank 2-2 8 Fuel Pre-Filter/Separator 2-2 8 Fuel Pump 2-2 9 Fuel Filter and Pre-filter Straining Screen 2-2 9 Fuel Return 2-2 11 Priming Fuel System 2-2 11

Engine Cooling System 2-2 14

General 2-2 14 Radiator Cap 2-2 14 Coolant 2-2 14 Draining the Cooling System 2-2 15 Flushing the Cooling System 2-2 15 Cleaning the Radiator Core 2-2 15 Filling the Cooling System 2-2 16 Thermostat 2-2 16 Coolant Filter Removal 2-2 16

Drive Belts 2-2 17

General 2-2 17 Preparation for Belt Check and Adjustment 2-2 17 Check Fan Belt Tension 2-2 17

Generator Maintenance 2-2 18 Cleaning 2-2 18

Adjustment 2-2 18

Section 3. Adjustment/Test 2-3 1

General 2-3 1 Testing the Generator Set 2-3 1

Pre-operational Test Procedures 2-3 1 Operational Test Procedures 2-3 4 Testing the No. 1 output circuit 2-3 5

November 27/1997 Table of Contents

Page 3

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

Testing the No. 2 output circuit 2-3 6 Testing and checking meters, switches,

relays, and indicating lights 2-3 7

Re-checking the entire unit after testing 2-3 9

Generator Set Adjustment 2-3 10

Generator Adjustment 2-3 10 Adjust 400 Hz voltage regulator 2-3 10 Basic Engine Adjustments 2-3 11 Engine Accessories Adjustment 2-3 11 Electric Governor System Adjustment 2-3 12

Generator and Exciter Test 2-3 18 Diode Test 2-3 18

Section 4. Troubleshooting Procedures 2-4 1

General 2-4 1 Equipment for Troubleshooting 2-4 1 Parts Replacement 2-4 1 Test Values 2-4 2 Check Connections and Leads 2-4 2 Electric Governor Troubleshooting 2-4 2 Engine Troubleshooting 2-4 3 Illustrations 2-4 3 Connection and Schematic Diagrams 2-4 3 Engine Controls 2-4 7 Generator Excitation Circuits 2-4 13 No. 1 Load Contactor Operating Circuit 2-4 15 No. 2 Load Contactor Operating Circuit 2-4 18 Protective Circuit 2-4 20 Generator 2-4 23

Chapter 3. Overhaul/Major Repair

Section 1. Exciter Armature 3-1 1

General 3-1 1 Exciter Armature 3-1 2 Exciter Armature Replacement 3-1 2

General 3-1 2 Tools Needed for Exciter Armature

Removal and Installation 3-1 3 Conditions for Exciter Removal 3-1 3 Preparation for Exciter Armature Removal 3-1 4 Exciter Armature Removal 3-1 4

Table of Contents November 27/1997 Page 4

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

Installing the Exciter Armature 3-1 6

Preparation for Exciter Armature Installation 3-1 6 Exciter Armature Installation 3-1 6

Section 2. Dual Bearing Flexible Coupling

General 3-2 1

Coupling Bolts 3-2 1

Disassembly 3-2 1

Separate Engine and Generator 3-2 1 Remove Coupling Assembly 3-2 2

Coupling Service 3-2 3

Coupling Kit 3-2 4 Bushing Kits 3-2 4 Bushing Replacement 3-2 4

Coupling Installation 3-2 5

Cleaning 3-2 5 Assembly 3-2 5

Reassemble Engine and Generator 3-2 10 Run-in and Periodic Check 3-2 10

Section 3. Generator Assembly 3-3 1

General 3-3 1 Procedure for Generator Assembly Removal 3-3 1

Procedure for Gaining Access to the Generator 3-3 1 Removing the generator Assembly 3-3 3

Installing a Generator Assembly 3-3 4

Remounting the Generator Assembly 3-3 4 Remounting the Previously Removed Assemblies 3-3 4

November 27/1997 Table of Contents

Page 5

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

Chapter 4. Illustrated Parts List 4-1 1

Section 1. Introduction 4-1 1

General 4-1 1 Purpose 4-1 1 Arrangement 4-1 1 Explanation of Parts List 4-1 1

Contents 4-1 1 Parts List Form 4-1 1

Section 2. Manufacturer’s Codes 4-2 1

Explanation of Manufacturer’s (Vendor) Code List 4-2 1

Section 3. Illustrated Parts List 4-3 1

Explanation of Parts List Arrangement 4-3 1 Symbols and Abbreviations 4-3 1

Section 4. Numerical Index 4-4 1

Explanation of Numerical Index 4-4 1 Numerical Index 4-4 1

Chapter 5. Manufacturer’s Literature 5-1 1 Appendix A. Options/Features Appendix A 1 Unusual Service Conditions Wet Stacking

Table of Contents November 27/1997 Page 6

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

Chapter 1. Description / Operation

Section 1. Description

1. General

The basic generator set covered in this manual is manufactured by Hobart Brothers Company, Ground Power Division, in Troy, Ohio. It is rated at 90 KVA and is designed to produce and deliver 115/200-volt, 400 Hz, 3-phase AC power to a parked aircraft or to Hobart approved test banks only. Series 500392 consists of the following part numbers:

Part Number 500392-001 identifies a single output unit structured* for trailer mounting. Part Number 500392-002 identifies a dual output unit structured* for trailer mounting. Part Number 500392-003 identifies a single output unit structured* for fixed/truck mounting. Part Number 500392-004 identifies a dual output unit structured* for fixed/truck mounting. Part Number 500392-005 identifies a single output trailer mounted unit similar to 500392-001. A

list of other features that make the 500392-005 unique is located with the Appendix in the back of this manual.

*In this manual, part numbers 500392-001 and 500392-003 are identical (single output) units. Part numbers 500392-002 and 500392-004 are identical (dual output) units. The difference between the units are the options available for them. For example, a fixed/truck mounting kit is not available for part numbers 500392-001 or 500392-002. See Appendix A.

Orientation

For purpose of orientation, the radiator is considered to be at the REAR of the unit. The generator and controls are at the FRONT. RIGHT and LEFT are determined by standing at the REAR end facing the machine. Thus, the control box is mounted on the LEFT side at the FRONT of the unit.

Optional Equipment

Chapters 1 through 5 of this Operation and Maintenance Manual identifies only the “strip down” version of the 90CU24 generator set. A list of optional equipment which make this manual unique to the generator set that you have purchased, appears in Appendix A. A few items included in Appendix A are cable trays, trailers, 28-volt DC power transformer-rectifiers, etc.

Special Features

The generator set has special features in which are described more fully under assemblies in which they appear. Three features, protective monitor, voltage regulator, and electric governor are mentioned here and described briefly.

a. Protective Monitor

The protective monitoring system receives signals from the fault sensing units in the generator 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. Voltage Regulator

A microprocessor-type, adjustable voltage regulator provides automatic voltage regulation at the aircraft. The regulator is also adjustable for a variety of output cable sizes and lengths.

November 27/1997 Chapter 1-1

Page 1

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

1. Control Panel

2. Output Cable Clamps

3. Frame

4. Emergency Stop Switch

5. Canopy

6. Radiator Access Door

Generator Set

Figure 1

Chapter 1-1 November 27/1997 Page 2

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

c. Electric Governor

The engine is equipped with an electric governor kit and other special equipment more fully described under the engine description.

Canopy

A sheet metal enclosure, identified as a canopy, provides protection for the engine, generator, and electrical controls. The canopy is designed to reduce the operational noise level in the immediate area of the machine.

Physical Basic Unit

Length 100 in. (2540 mm) 148 in. (3759 mm) Width 45 in. (1143 mm) 77 in. (1956 mm) Height 47.5 in. (1203 mm) 61 in. (1549mm) Weight with T-R 6700 lb. (3039 kg) Weight of optional T-R 300 lb. (136 kg) Not applicable

Generator

Output power rating (kVA) Output Voltage 115/200 Volts Rated load capacity (Amps) 260 Amps Frequency (Hz) 400 Hz Output kilowatts 72 Power factor 0.8 Duty cycle 100% Operating speed (RPM) 2400 RPM Overload capacity, both outputs:

125% rated load (Amps) Output cable size 2/0

Over voltage Trips at 126 volts after a 1-second time delay

Under voltage Trips at any voltage below 100 volts after 7 seconds. Over frequency Trips at any value between 426-Hz and 480-Hz after a 5-second

Under frequency Trips at 375-Hz or less after a 5-second time delay. Overload time delay Trips in approximately 5 minutes at 125% load on either or both

90 kVA

325

Generator Protective System

Trips at 140 volts in 160 milliseconds. Trips at 180 volts in 50 milliseconds.

time delay. Trips immediately at any frequency exceeding 480-Hz.

outputs.

With Trailer

Specifications and Capabilities

Figure 2

November 27/1997 Chapter 1-1

(Sheet 1 of 2)

Page 3

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

Manufacturer Cummins Engine Company, Inc.

Model No. 6BT5.9C165 Type In-line 6 cylinder 4 Cycle Diesel Bore and Stroke 4.02 x 4.72 inches (10.2 x 11.9 cm) Displacement 359 c.i. (5.9 liters) Compression Ratio 17.5 : 1 Horsepower 165 Idle speed 850+/-50 RPM High speed limiting Approx. 2750 +/-75 RPM Normal governed speed 2400 RPM Electrical system 12-V DC Ground Negative Firing order (RH rotation) 1-5-3-6-2-4 Lubricating oil capacity (w/filter) 16 quarts (15.1 liters) Coolant capacity system 38 quarts (36 liters)

Engine

Columbus, Ohio 47201

Specifications and Capabilities

Figure 2 (Sheet 2 of 2)

Engine and Generator

The engine and generator comprise the principal components of the generator set. They are mounted on the welded steel frame of the chassis. The engine coolant radiator is also mounted on the frame just forward of the engine-generator combination. Figure 3 is an illustration showing the location of all major components and sub-assemblies.

a. Basic Engine.

The basic engine is an in-line 6-cylinder diesel rated at 165 horsepower. See Fig. 2 for general specifications.

b. Engine Manufacturer’s Equipment

As received from the engine manufacturer, the engine includes the following equipment which is more fully described in the Cummins Operation and Maintenance Manual.

(1)

Electrical System The 12-V DC electrical generating and starting system includes an alternator, voltage regulator,

and starter with solenoid switch.

(2)

Fuel Filter The fuel filter is a spin-on disposable, vacuum type connected between the fuel lift pump and

injector pump

(3)

Oil Filter The engine oil filter is a spin-on, full-flow type. It is mounted on the right side of the engine.

Chapter 1-1 November 27/1997 Page 4

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

1. Radiator

2. Engine

3. Generator

4. Air Cleaner

5. Control Box

Generator Set Components

Figure 3

November 27/1997 Chapter 1-1

6. Output Module Panel

7. Engine-Generator Control Panel

8. Mounting Frame

9. Muffler

Page 5

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

(4)

Engine over-speed protection The engine is protected against over-speed by a speed-limiting mechanism in the mechanical

governor.

c. Engine-cooling fan

The engine fan is designed to blow air inward as a conventional fan does.

Refer to the engine Operation and Maintenance Manual in Chapter 5 for more engine details.

d. Engine faults

The following is a table listing faults which may occasionally occur. Column two of the table explains what happens in the engine’s circuitry when the fault occurs, and column three tells how to return the generator set to service.

outward through the radiator, rather than pull the air

ENGINE FAULTS

Engine Fault Condition What This Fault Condition Does

Over temperature or low oil pressure

Low fuel Turns on the low fuel indicating

Clogged air cleaner or other restriction in the combustion air inlet.

Automatically removes power from the electric governor controller, shuts down the engine, and turns on the applicable indicating light.

light (27, Fig. 5). Depending on the position of JP2 and JP3 on the control PC board, a low fuel fault may cause the engine to idle, shut down, or continue to run at rated speed.

Turns on the air cleaner restriction indicating light (6, Fig. 5)

To Put the Generator Set Back

into Service:

a) Press the engine stop button (20, Fig. 5) to turn off the indicating light and reset the protective system. b) Or use E-STOP (4, fig. 1)

button for immediate reset.

a) The low fuel fault indicating function must be reset by

pressing the engine stop button (20, Fig. 5). Fuel must be

added prior to attempting

another engine start.

b) Or use E-STOP (4, fig. 1)

button for immediate reset.

a) Press the engine stop button

(20, Fig. 5). The restriction must be removed prior to attempting another engine start.

b) Or use E-STOP (4, fig. 1) ]

button for immediate reset.

Chapter 1-1 November 27/1997 Page 6

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

e. Hobart Installed Equipment

This generator set is modified at Hobart Brothers by the addition of the following equipment:

(1)

Shut Down/Reset device In addition to the other devices provided by the engine manufacturer, an engine shutdown/reset

feature is added by Hobart Brothers.

EMERGENCY SHUTDOWN/RESET SWITCH (mushroom button). The emergency shutdown switch has two purposes. One is to Reset the starting circuit

following a failed starting sequence. The other is to provide instant shut off of the generator set by disconnecting power to the governor circuit through the control box. It is located on the left side of the generator set on the door near the control box.

To operate the EMERGENCY SHUTDOWN/RESET SWITCH:

• Push button in until engine stops or until button travel stops

• Pull the button back out to reset

(2)

Engine Safety Devices In addition to the safety devices provided by the engine manufacturer, other engine shutdown

features are added by Hobart Brothers

Coolant high temperature shutdown system The coolant temperature shutdown system consists of a Detroit Diesel supplied temperature

switch. This switch controls a relay in the control box, which is in series with the governor system. This relay will stop the engine if the temperature reaches 220º F (96º C).

Oil pressure shutdown system The oil pressure shutdown system consists of a Hobart supplied oil pressure switch. This

switch is diaphragm operated and held is closed position by any normal oil pressure above 12 PSI (83 kPA). It is connected in series with the fuel shutoff valve and will open the holding circuit if the oil pressure drops to 12 PSI (83 kPA) or below.

(3)

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 (and generator output frequency) because it provides faster engine response to changes in load conditions. This fast response results in very close frequency control. A brief description is given below:

The governor system consists of the following main components:

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.

Control unit The control unit is a box containing a compact assembly of solid state components. 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.

Actuator The actuator supplies the force needed to move and position the fuel lever as required to

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

November 27/1997 Chapter 1-1

Page 7

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

(4)

Radiator

The radiator is a one-piece type designed for long periods of operation without servicing. Refer to Section 2-1 for servicing procedure.

(5)

Air cleaner The diesel-engine air cleaner (fig. 4) is so constructed that air enters through its cylindrical body,

and then is filtered in the process before being passed onto the engine turbo-charge assembly. An air cleaner service indicator device is mounted on the air cleaner assembly to monitor air flow

in the air cleaner. As the air cleaner becomes filled with dust, dirt, and carbon, the intake system air flow becomes increasingly restricted. This restriction causes a diaphragm inside the indicator to move toward an electrical contact. When the maximum allowable restriction level is reached, the circuit closes and the air cleaner indicator light (6, Fig. 5) on the engine-generator control panel is illuminated to warn the operator that the air cleaner must be changed. The electrical indicator automatically resets after a new air cleaner is installed.

Service Indicator

Air Cleaner

Air Cleaner and

Service Indicator

Figure 4

f. Generator

The 400 Hz generator is a brushless, revolving field, three-phase, alternating current type. The generator set covered by this manual is a dual-bearing type. The front end of the rotor shaft extends forward beyond the front bearing and is attached to the engine flywheel by a flexible coupling assembly. The rear end of the rotor shaft extends rearward beyond the rear bearing and into the exciter stator housing. The exciter rotor is mounted on this shaft extension with a key and is secured by a washer and 1/2"-13 thread cap screw. A rectifier with three 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 voltage regulator. A centrifugal, radial-blade fan which is part of the flexible 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.

Chapter 1-1 November 27/1997 Page 8

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

7. Control Box Assembly

The control box is a sheet metal enclosure which houses and provides mounting facilities for engine and generator controls and monitoring equipment.

a. Control Panel (Fig. 5)

On the door of this control box is the control panel. The control panel is divided into three sections. On the left side of the control panel, as one faces it, are engine meters and indicating lights. On the right side of the control panel are generator meters and indicating lights. At the bottom of the control panel are push-button switches for operating the engine and generator.

(1)

Panel lights and panel light push-button switch Meters are lighted from inside the control panel. They are controlled by a push-button switch (28)

at the bottom left on the control panel.

(2)

Engine hour meter The hour meter (5) is electrically driven from the 12-V DC battery system. The hour meter

measures and records engine running time and will record up to 9999.9 hours on five revolving drums. It is only functional when when the engine is running and the oil pressure safety shutdown switch, mounted on the engine block, is closed.

(3)

Engine oil pressure gage The oil pressure gage (7) is an electrical type which is connected by a wire to an oil pressure

sensor installed in the engine lubricating system. The range is 0 to 125 PSI (0 to 862 KPA).

(4)

Engine ON indicating light When the engine control push-button switch (26) is pressed to start the engine, a green

indicating light within the push-button switch glows.

(5)

Engine coolant temperature gage The temperature gage (3) is an electrical type which is connected by a wire to a water

temperature sensor installed in the engine cooling system. The gage indicates engine coolant temperature in the range of 100 to 240 º F (38 to 116º C).

(6)

Engine start push-button switch

This push-button switch (26) which actuates the solenoid switch to connect power to the engine starting motor. 12-V DC power is supplied directly to the governor controller and the oil pressure safety shutdown switch is bypassed. This bypass is necessary for engine starting because the low oil pressure switch is CLOSED until the engine is running normally.

When pressed a second time, this push-button switch provides a 12-V DC signal to the speed adjust PC board on the governor controller, which causes the governor actuator to adjust the engine speed to 2400 RPM. At the same time, a ground signal is provided to the regulator, enabling the generator to build up voltage for 400-Hz generator output.

Pressing the push-button switch once more removes these signals and the engine reverts to idle speed.

(7)

Engine stop push-button switch When the engine stop push-button switch (20) is pressed once, the indicator within the switch

will glow (red). Then a 3 - 5 minute delay will occur to permit the turbo and other engine components to cool evenly. After the delay, power is disconnected from the governor controller. This governor actuator will then close and shut off fuel to the engine so the engine can shut down.

when pressed, connects 12-V DC power to the starter solenoid coil

November 27/1997 Chapter 1-1

Page 9

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

1. Fuel Gage

2. Front Panel

3. Engine Coolant Temperature Meter

4. Over Temperature Indicator Light (Red)

5. Engine Hour Meter

6. Indicating Light, Air Cleaner Restriction (Red)

7. Oil Pressure Gage

8. Engine Ammeter

9. Frequency Meter

10. Control Box Label

11. Strip Lights (3)

12. Generator Ammeter

13. Voltmeter

14. Overload Indicator Light

Engine Generator Control Panel

(Dual Output Shown)

Figure 5

Chapter 1-1 November 27/1997 Page 10

15. Over Voltage Indicator Light

16. Adjustable Grip Latch

17. Under Voltage Indicator Light (Red)

18. Meter Selector Switch

19. Test-Reset Push-Button Switch (Red)

20. Engine Stop Push-Button Switch

21. Under Frequency Indicator Light (Red)

22. No. 2 Contactor Push-Button Switch (Orange)

23. Over Frequency Indicator Light (Red)

24. No. 1 Contactor Push-Button Switch (Yellow)

25. Low Oil Pressure Indicator Light (Red)

26. Engine Start Push-Button Switch (Green)

27. Low Fuel Indicator Light (Red)

28. Panel Light Push-Button Switch (Yellow)

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

(8)

Engine ammeter The ammeter (8) indicates the direction and value of current flow from or to the 12-V DC battery.

Its graduated range is from -60 A through O A to + 60 A.

(9)

Engine fuel gage An electric fuel gauge (1) receives its controlling signal from a sending unit in the fuel tank.

Twelve volt DC operating power is supplied to the fuel gauge when the green engine start push-button switch (26) is pressed. The fuel level can be checked when the unit isn’t running by pressing the yellow lamps push-button switch (28)

(10)

Protective system Indicating lights, test and reset push-button switches The function of this set of five lights (14, 15, 17, 21 and 23)

abnormal condition of over voltage, under frequency, 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 test/reset push-button switch (19) is pushed. All lamps in indicating lights may be tested by pressing the test/reset push-button switch. A lamps test should be performed only when disconnected from a load, as the contactor(s) will open during the test cycle.

(11)

Engine systems warning lights (red) Four red indicator lights are illuminated to warn the operator of abnormal engine operations

which must be corrected. These indicators are: The over temperature indicator light (4), air cleaner restriction indicator (27). The function of the air cleaner indicator circuit is explained in detail in Para. 6, E, (4).

(6)

, low oil pressure indicator light (25),and low fuel indicator light

is to indicate, to the operator, the

(12)

Generator output monitors The generator output is monitored by three instruments; a frequency meter (9),a voltmeter (13)

and an ammeter (12). The frequency meter is an analog type, and indicates the frequency of the generator output alternating current in the range of 360 to 440 Hz voltmeter indicates the generator output voltage in each phase-to-neutral (A-N, B-N and C-N) or phase-to-phase (A-B, B-C and C-A) as selected by the meter selector swit ch (18) has a 3-1/2-inch face and the scale is graduated 0 to 300 V. The ammeter is also 3-1/2-inch size and is graduated 0 to 500 A. The amperage value in each of the three phases may be read on the ammeter by selecting the desired phase with meter selector switch (18) current transformers, located on the output module (Fig. 9), lower the output 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.

(13)

Voltmeter-ammeter selector switch This switch provides 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-to-neutral or line-to-line. The meter switch (18) is a six-position, rotary type. A nameplate, located under the switch knob, is marked and lettered to indicate the six functional positions of the meter switch.

(14)

Load contactor indicating lights Indicating lights within the respective contactor control push-button switches (22 orange and 24

yellow) glow when the circuit is energized, indicating that power is available at the plug. When the load contactor opens for any reason, the light is turned OFF.

(meters)

(cycles per second)

The voltmeter

Three ammeter

. The

November 27/1997 Chapter 1-1

Page 11

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

1. Control Box Wrapper

2. Control Box Top

3. Receptacles (4)

4. Memory and Time Delay PC Board

5. Over-Under Frequency PC Board

6. Over-Under Voltage PC Board

7. Voltage Regulator PC Board

8. Terminal Blocks (2)

9. Switch Mounting Bracket

11. Panel Lights (2)

12. Engine Circuit Breaker (10A)

13. Controls Circuit Breaker (5A)

14. Marker Light Circuit Breaker (10A)

15. Contactors Circuit Breaker (5A)

16. Test Bank / Aircraft Switch, No. 2 Output

17. Test Bank / Aircraft Switch, No. 1 Output

18. Regulated / Diagnostic Switch

19. Generator Set Control PC Board

10. Label, Switch Mounting Bracket

Control Box Interior Components (Dual Output Shown)

Figure 6

Chapter 1-1 November 27/1997 Page 12

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

b. Control Box Interior Components (Fig. 6)

(1)

Test bank aircraft switches For each load contactor circuit, a single-pole, single-throw toggle switch (16 or 17) provides a

means of bypassing the interlock circuit for that contactor when supplying power to a load bank or to an aircraft not equipped with a plug interlock system.

(2)

Regulated-diagnostic switch When the regulated-diagnostic switch

output voltage is regulated by the solid state voltage regulator (7,Fig. 6, and Fig. 8) for 115/200 V-AC output to an aircraft. When this switch is placed in the DIAGNOSTIC (up) position, battery voltage (12-V DC) is applied to the generator exciter with the engine running at rated RPM, in order to check the operation of the generator. By applying this 12 V-DC battery voltage to the exciter and observing generator output voltage, it can be determined if a particular power output malfunction is caused by a defective generator or by a defective voltage regulator. When this switch is in the MAINTENANCE position, no current is supplied to the generator exciter. However, a low-level, unregulated voltage of approximately 30-V AC will be produced at the generator output terminals due to the residual magnetism of the exciter.

(3)

Circuit breakers A 10-ampere circuit breaker (12), protects the 12-V DC engine governor and fault circuits, and

another 10-ampere circuit breaker (14) breaker (13) protects the 12-V DC control system, and another 5-ampere circuit breaker (15) protects the circuits of the load contactors.

(18)

is in the REGULATED (down) position, generator

protects the 12-V DC lighting system. A 5-ampere circuit

(4)

Memory-time delay module The memory and time delay module (4) is sometimes called the protective monitor module. It is

a solid-state device with a hermetically-sealed, reed-type circuit. The printed circuit board includes five memory circuits and a time delay circuit. Each circuit is connected to a corresponding sensing circuit in the sensing modules. All memory circuits are connected to the module circuit relay coil, and any one of the circuits can energize the coil to open the circuit relay contacts. Thus, when a sensing device energizes any one of the module circuits, the module circuit is also energized to break the load contactor holding circuit and allow the load contactor to open. A time delay system is designed into the under voltage circuit to prevent nuisance opening of the contactor under conditions of momentary under voltage in the generator output. An under voltage condition which continues uninterrupted for a period of 4 to 12 seconds (adjustable) will cause the time delay circuit to open the load contactor. Each of the five circuits is connected to a corresponding indicating light (Fig. 5; 14, 15, 17, 21 or 23) occurs. The module circuit will remain energized (OPEN) and the light will remain ON until the reset push-button switch (19, Fig. 5) is pushed to break the module 12-V circuit, and allow the circuit to return to normal, CLOSED position.

(5)

Sensing modules The voltage sensing module (6) and frequency sensing module (5) are connected to generator

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 (4) to open the load contactor and disconnect output to the aircraft. Trip values are adjustable; however, adjustments should be made ONLY under laboratory conditions.

On the 400-Hz output module, one solid-state overload signaling device (1, Fig. 9), is also connected to the protective monitor module. Its function is similar to the voltage and frequency sensing modules.

which is turned on when a fault

November 27/1997 Chapter 1-1

Page 13

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

Trip values for protective circuits are as follows:

Over voltage relay Trips at 126 volts after 1-second time delay.

Under voltage relay Trips at 100 volts after 7 seconds. Over frequency relay Trips at any value between 420-Hz and 480-Hz

Under frequency Trips at 380-Hz or less after a 7-second time

Overload time delay Trips in approximately 5 minutes at 125% load

(6)

Generator Set Control PC Board The generator set control PC board (19, Fig. 6 and Figure 7) is a central location for the various

plug-in relays used for generator operation. Troubleshooting is thus easier for technicians working on the generator set. This PC board contains the following relays and associated circuitry.

Trips at 140 volts in 160 milliseconds. Trips at 180 volts in 50 milliseconds.

after a 5-second time delay. Trips immediately at any frequency exceeding 480-Hz.

delay.

on either output or both outputs.

• Master relay, K69, routes 12-V DC power to all circuits, except panel and clearance lights. This relay is operated upon pressing the START push-button switch remains in the OPERATE condition until it is RESET by the STOP push-button switch

(26, Fig. 5)

, and

(20,

Fig. 5).

• Bypass relay, K73, is also activated by pressing the START push-button switch. Relay K73 enables the start signal to the starter solenoid for 5 seconds after it is initially activated. K73 also disables the low oil pressure fault circuit during this 5 second period.

• Idle-excitation relay, K68, controls engine speed and generator excitation. K68 activates to idle the engine and remove excitation from the generator. In the RESET state, K68 provides a 12-V DC signal to the governor controller, causing the engine to attain rated speed (2400 RPM). At the same time, K68 provides a ground signal to voltage regulator, which enables excitation current to the generator. When the engine is running, K68 changes from OPERATE to RESET, or vice-versa, with each closure of the START push-button switch. Auxiliary circuit also controls the idle-excitation relay. This auxiliary circuit causes the relay to operate when: (1) Engine is at rest and the start push-button switch (26, Fig. 5) is pressed, (2) Any engine fault, except the air filter restriction, occurs.

• The circuit which controls K68 also drives a flasher circuit that controls the lamp within the START push-button switch (26, Fig. 5).

• Relay K72 controls the No. 1 contactor. When the engine is at rated speed, and voltage has built up, K72 changes from OPERATE to RESET, or vice-versa, with each closure of the No. 1 contactor push-button switch. An auxiliary circuit will reset K72 when the No. 1 plug is removed from the aircraft. The No. 2 contactor control relay, K272 operates in the same manner.

• Relay K70 controls panel and clearance lights. This relay changes from OPERATE to RESET, or vice-versa, with each closure of the LAMPS push-button switch (28, Fig. 5)

The fuel gage is also powered by K70 when the engine is at rest. K70 is reset, turning off all lights, when the engine STOP push-button switch is pressed.

Chapter 1-1 November 27/1997 Page 14

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

1. Master Relay (K69)

2. Idle-Excitation Relay (K68)

3. Over Temperature Fault Relay (K67)

4. Low Oil Pressure Fault Relay (K71)

5. No. 2 Contactor Control Relay (K272)

6. Panel and Clearance Lights Relay (K70)

Generator Set Control PC Board

November 27/1997 Chapter 1-1

7. No. 2 Plug-Interlock Relay (K202)

8. No. 1 Plug-Interlock Relay (K2)

9. Bypass Relay (K73))

10. Low Fuel Fault Relay (K65)

11. Air Filter Fault Relay (K66)

12. No. 1 Contactor Control Relay (K72)

Figure 7

Page 15

OM-2084 / Operation and Maintenance Manual 90CU24 / Series 500392 Generator Sets

• Relays K65, K66, K67 and K71 are fault relays. Each receives a signal from engine sensors, and illuminate panel lights to indicate the presence of a fault. Activation of the over temperature relay, K67, or low oil pressure relay, K71, result in interruption of 12-V DC power to the governor controller, causing the engine to shut down. Activation of low fuel relay K65 may result in the engine reverting to idle speed or shut-down, depending on the condition set by jumpers JP2 and JP3. The only result of an air filter fault, is that relay K66 causes illumination of the panel light. All engine fault relays remain activated until power is removed by pressing the STOP push-button switch (20, Fig. 5) or the emergency stop switch.

• The plug-interlock relays (K2 and K202) on the control PC board cause the respective output load contactors to open in 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 circuit is supplied from the aircraft either through an on-board transformer- rectifier, or from a twenty-eight volt electrical system. Connection from aircraft to the interlock circuit is made through terminals E and F on the output cable plug

(7)

Voltage regulator PC board This voltage regulator (7, Fig. 6 and Fig. 8) is designed to provide 1% voltage regulation for all

loads up to 100% of rated load on a three-phase, four-wire, 115/200-volt, 400-Hz brushless alternator. This regulator provides field excitation power as required to meet varying alternator load conditions to hold the alternator voltage constant. In addition, the voltage regulator PC board circuitry provides line drop compensation. Any deviation of the alternator voltage from its set, regulated level is sensed at the voltage regulator PC board. The sensing signal is compared to a reference signal, and, with associated circuitry, varies the field power supplied to the rotary exciter.

• When the machine is started, and the engine is at rated speed, the rotary exciter is excited from alternator residual magnetism through the half-wave rectifier bridge, located on the voltage regulator PC board assembly. As the rotary exciter voltage increases, alternator excitation increases and the alternator voltage builds up. The sensing circuit of the voltage regulator PC board then compares the input voltage to a reference voltage and adjusts the field power of the rotary exciter to bring the voltage into regulation limits.

• When the alternator is loaded, its terminal voltage decreases, lowering the rectified three-phase voltage of the voltage sensing circuit. The sensing voltage is low in respect to its reference voltage, causing the voltage regulator PC circuitry to increase the power to the field of the rotary exciter. The alternator voltage increases until the voltage returns to its regulated value.

• When a load is removed from the alternator, the alternator voltage rises. The rectified three-phase voltage sensing signal increases, causing this signal to be higher than the reference signal. The associated voltage regulator circuitry causes the field power of the rotary exciter to decrease, lowering the alternator voltage until the voltage returns to regulated value. The line drop voltage compensation circuit consists of: (1) A current transformer on each phase of the load circuit, and (2) A fixed resistance in parallel with each current transformer. The current transformers detect the magnitude of current flowing through the power cables from the alternator to its load and feed a signal into the voltage regulator PC board. The PC board processes this signal to change the output voltage proportional to the current draw. The regulator output increases slightly so that the alternator output voltage is equal to the regulated voltage plus the voltage drop in the lines. The line drop compensation potentiometer may be adjusted to match exactly the voltage drop of the power cables carrying the load current.

• A receptacle connector at the bottom of the voltage regulator PC board provides a quick connect-disconnect facility for interconnecting wire leads.

Chapter 1-1 November 27/1997 Page 16

+ 184 hidden pages

Hobart 90CU24 Operation And Maintenance Manual

Specifications and Main Features

Frequently Asked Questions

User Manual