Northern Lights 281PSL1500, 281PSL1501, 281PSL1502, 282PSL1503, 282PSL1504 User Manual

MAGNAPLUS® GENERATOR

www.marathonelectric.com

280–430 Frame

Installation, Operation,

and Maintenance Manual

Marathon Electric Mfg. Corp.

A Subsidiary of Regal-Beloit Corp.

P.O. Box 8003

Wausau, WI 54402-8003

Phone: [phone]

Fax: [phone]

CONTENTS

Safety 2
Receiving and Storage 2
Principles of Operation 3 - 4
Installation 4 - 6
Wiring Connections 6 - 9
Operation 9 - 10
Maintenance 10 - 11
Testing 11 - 12
Service 12 - 14
Troubleshooting 14 - 17
Specifications 18
Parts List & Recommended Spare Parts 19 - 20

SAFETY

When in doubt, ask. Questions are much easier to handle
than mistakes caused by a misunderstanding of the
information presented in this manual.

RECEIVING AND STORAGE

RECEIVING AND STORAGE

Upon receipt of the generator, it is recommended that it be
carefully examined for possible shipping damage. The
generator was given to the freight carrier in good condition;
thus, the carrier is responsible for the product from the
factory dock to the destination. Any damage should be
noted on the freight bill before accepting the shipment. Any
claims for damage must be promptly filed with the delivering
carrier.

PLEASE REMEMBER SAFETY FIRST. If you are not sure
of the instructions or procedures contained herein, seek
qualified help before continuing.

This service manual emphasizes the safety precautions
necessary during the installation, operation, and
maintenance of your MagnaPLUS generator. Each section
of this manual has caution and warning messages. These
messages are for your safety, and the safety of the
equipment involved. If any of these cautions or warnings
are not readily understood, seek clarification from qualified
personnel before proceeding.

Before any service work is done, disconnect all power
sources and lock out all controls to prevent an unexpected
start-up of the generator set driver. Proper grounding
(earthing) of the generator frame and distribution system in
compliance with local and national electrical codes and
specific site requirements must be provided. These safety
precautions are necessary to prevent potential serious
personal injury, or even death.

The hazards associated with lifting or moving your
MagnaPLUS generator are pointed out in the installation and
maintenance sections. Incorrect lifting or moving can result
in personal injury or damage to the unit.

Prior to start-up of the unit ensure that all generator leads
are properly connected to the generator link board located
inside the connection box. Always assume that there will
be voltage present at the generator terminals whenever the
generator's shaft is rotating, and proceed accordingly.
Residual voltage is present at the generator terminals and at
the automatic voltage regulator panel connections even with
the regulator fuse removed. Caution must be exercised, or
serious injury or death can result.

UNPACKING AND HANDLING

Carefully read all instruction tags shipped with the unit.
When lifting, attach an overhead crane to the lifting lug(s)
on the generator frame. Apply lifting forces in a vertical
direction. When transporting single bearing generators, the
generator’s rotor must be adequately supported to prevent
damage.

WARNING

THE LIFTING LUG(S) ON THE GENERATOR ARE
DESIGNED TO SUPPORT THE GENERATOR ONLY.
DO NOT LIFT A COMPLETE GENERATOR AND
DRIVER ASSEMBLY BY MEANS OF LIFTING
LUG(S) ON THE GENERATOR. PERSONAL INJURY
OR EQUIPMENT DAMAGE MAY RESULT.

STORAGE

In the event that the generator is not immediately installed
on its prime mover, it is recommended that the unit be
stored indoors in a clean, dry area which is not subject to
rapid changes in temperature and humidity. If the generator
is stored for a long period of time, the generator should be
tested, cleaned and dried as required before being put into
service. See the maintenance section of this manual for
further information. If the unit has been stored in an area
where it has been subject to vibration, it is recommended
that the bearing(s) be inspected and replaced as necessary.

This manual is not intended to be a substitute for properly
trained personnel. Installation and repairs should only be
attempted by qualified, trained people. The cautions and
warnings point out known conditions and situations that are
potentially hazardous. Each installation may well create its
own set of hazards

2

PRINCIPLES OF OPERATION

PMG (optional)

PMG Field

(rotor)

N

S

PMG

Armature

(stator)

PMG Input Power (optional)

Exciter Field

(stator)

(+)

DC
(in)

(-)

Exciter Field Power

(1 phase, 300/250 hertz)

Rotating Assembly

Exciter Armature

(rotor)

3 Phase AC (out)

Rotating Rectifier Assembly

3 Phase -- Full Bridge

(DC out)

Automatic

Voltage

Regulator

Main Field

(rotor)

(+)

DC

(in)

(-)

Input Power -- Single Phase

(shunt powered regulator)

Sensing Input -- Single Phase

FIGURE 1 -- MagnaPLUS Circuit Diagram

Main Armature

3 Phase AC (out)

3 phase (optional)

(stator)

L

1

L

2

L

3

FIGURE 2 -- Typical MagnaPLUS Layout Diagram

3

PRINCIPLE OF OPERATION

horsepower per generator KW in motor starting capability.
For specific data contact Marathon Electric.

MagnaPLUS generators are a brushless, self excited,
externally voltage regulated, synchronous AC generator.
The generator is made up of six major components: main
stator (armature), main rotor (field), exciter stator (field),
exciter rotor (armature), rectifier assembly, and voltage
regulator. In understanding the above terminology, note the
following: stators are stationary, rotors rotate, a field is an
electrical input, and an armature is an electrical output.
These system components are electrically interconnected as
shown in figure 1 and physically located as shown in
figure 2.

The generator’s exciter consists of a stationary field and a
rotating armature. The stationary field (exciter stator) is
designed to be the primary source of the generator’s
residual magnetism. This residual magnetism allows the
exciter rotor (armature) to produce AC voltage even when
the exciter stator (field) is not powered. This AC voltage is
rectified to DC by the rotating rectifier assembly and fed
directly to the main rotor (field). As the generator shaft
continues to rotate, the main rotor (field) induces a voltage
into the generator's main stator (armature). At rated speed,
the main stator’s voltage produced by the residual
magnetism of the exciter allows the automatic voltage
regulator to function. The regulator provides voltage to the
exciter resulting in a build-up of generator terminal voltage.
This system of using residual magnetism eliminates the
need for a special field flashing circuit in the regulator. After
the generator has established the initial residual voltage, the
regulator provides a controlled DC field voltage to the exciter
stator resulting in a controlled generator terminal voltage.

PARALLEL OPERATION

All MagnaPlus generators are built with 2/3 pitch main stator
windings and full amortisseur (damper) windings. These
features make the MagnaPlus generators suitable for
parallel operation when equipped with the proper voltage
regulators and voltage regulator accessories. Consult with
the factory for further information relative to parallel
operations.

NONLINEAR LOADING

Solid state electronic control devices (variable frequency
drives, precision motor controls, battery chargers, etc.)
utilize electronic switching circuits (thyristors, SCRs, Diodes,
etc.). These switching circuits introduce high frequency
harmonics which distort the normal wave form of the
generator. This creates additional heat in the generator
windings and may cause the generator to over-heat.
Problems which can occur are not limited to the generator.
Poor wave shape may adversely effect various loads
connected to the generator. Consult Marathon Electric for
further information relative to nonlinear loads.

INSTALLATION

PREPARATION FOR USE

Voltage Regulation

In the standard configuration (shunt excited), the automatic
voltage regulator receives both its input power and voltage
sensing from the generator's output terminals (See
Figure 1). With the optional PMG configuration, the
regulator receives input power from the PMG. The regulator
automatically monitors the generator's output voltage
against an internal reference set point and provides the
necessary DC output voltage to the exciter field required to
maintain constant generator terminal voltage. The
generator's terminal voltage is changed by adjusting the
regulator's reference set point. Consult the regulator
manual for specific adjustment and operating instructions.

MOTOR STARTING

When a motor is started, a large surge of current is drawn
by the motor. This starting current is equivalent to the
motors locked rotor or stall current and is 5 to 10 times
normal full load current. When the generator supplies this
in-rush of starting current, the generator voltage dips
temporarily. If the motor is too large for the generator, the
generator’s voltage dips greater than 30 percent. This may
result in the motor starter de-energizing or the motor
stalling. MagnaPlus generators generally supply .3 to .4

Although the generator has been carefully inspected and
tested in operation prior to shipment from the factory, it is
recommended that the generator be thoroughly inspected.
Check all bolts for tightness and examine the insulation on
lead wires for chafing prior to proceeding with installation.
Remove all shipping tapes, bags, skids and rotor support
blocking. For two bearing units, rotate the shaft by hand to
ensure that it rotates smoothly without binding.

4

WARNING

DISABLE AND LOCKOUT ANY ENGINE CRANKING
DEVICES BEFORE ATTEMPTING TO INSTALL OR
SERVICE THE GENERATOR. FOR ELECTRIC
START SETS, DISCONNECT THE CRANKING
BATTERY. FOR AIR START, DISCONNECT THE AIR
SUPPLY. FOR MOTOR GENERATOR SETS, OPEN
THE POWER SUPPLY TO THE DRIVE MOTOR.
FAILURE TO COMPLY WITH THESE SAFETY
PROCEDURES COULD RESULT IN SEVERE
PERSONAL INJURY OR EQUIPMENT DAMAGE.

NEVER "BAR OVER" THE ENGINE GENERATOR
SET USING THE GENERATOR'S FAN. THE FAN IS
NOT DESIGNED FOR THIS PURPOSE. BARRING
OVER THE SET WITH THE FAN COULD DAMAGE
THE FAN AND RESULT IN PERSONAL INJURY OR
EQUIPMENT DAMAGE.

driver and the generator's shaft. Aligning the generator and
its driver as accurately as possible will reduce vibration,
increase bearing life, and ensure minimum coupling wear. It
may be necessary to shim the generator feet for proper
support and alignment. Secure the feet of the generator
with grade 5 or greater bolts through the holes provided in
the mounting feet. Consult the coupling manufacturer's
instructions for alignment specifications and procedures.

GENERATOR MOUNTING

Two Bearing Units -- Belt Driven

Two bearing MagnaPLUS generators can be belt driven
provided belts are sized and applied correctly. Please refer
to your supplier of belts and sheaves for correct sizing and
tensioning specifications. A bearing life calculation should
be performed. Marathon Electric recommends a minimum
B-10 life of 40,000 hours. If cog type belts are used, a
vibration may be introduced which could lead to premature
failure of the bearings.

GENERATOR MOUNTING

Single Bearing Units.

Single bearing units are provided with an SAE flywheel
housing adapter flange and flexible drive discs. Coupling
the generator's shaft to the engine flywheel is accomplished
with special steel drive discs bolted to the shaft. In addition
to the drive discs, there may be a hub spacer, spacer discs,
or a combination of hub spacer and spacer discs inserted
between the drive discs and the shaft to achieve the proper
shaft extension ("G" dimension per SAE J620c). Holes are
provided in the periphery of the coupling discs which
correspond to tapped holes in the prime mover's flywheel.
The outside diameter of the drive discs fit in a rabbet in the
flywheel so that concentricity is assured.

Grade 8 place bolts and hardened washers are
recommended to mount the drive discs to the flywheel. DO
NOT USE SPLIT TYPE LOCK WASHERS. Split lock
washers when biting into the drive disc cause stress risers
which may result in the disc fracturing.

The SAE flywheel housing adapter ring and the engine
flywheel housing are designed to match each other with no
further alignment necessary. Use grade 5 or greater
mounting bolts. MagnaPLUS generator frames are
constructed with two or three bolt holes per foot. The feet
should be shimmed where necessary to obtain solid contact
with the sub-base. With the frame securely bolted to the
engine flywheel housing, there is no side thrust or pull on
the generator frame, thus no real need to secure the feet
with more than one bolt per foot.

END PLAY TESTING

Refer to the engine manual for recommended end play
specifications and measurement procedures. If end play is
not to specification, it is an indication that the generator
shaft is not moving freely in the assembly, and normal life of
the thrust bearing could be impaired. Probable causes of
this problem are:

1. Improper seating of drive discs in the flywheel resulting
in misalignment.

2. Improper mating of generator frame to engine flywheel
housing resulting in misalignment.

3. Improper "G" dimension per SAE J620c on either the
engine or generator.

TORSIONAL VIBRATION

Torsional vibrations are generated in all rotating shaft
systems. In some cases, the amplitude of these vibrations
at critical speeds may cause damage to either the
generator, its driver, or both. It is therefore necessary to
examine the torsional vibration effect on the entire rotating
system. IT IS THE RESPONSIBILITY OF THE
GENERATOR SET ASSEMBLER TO ASSURE THE
TORSIONAL COMPATIBILITY OF THE GENERATOR AND
ITS DRIVER. Drawings showing pertinent dimensions and
weights of the rotating assembly will be supplied by
Marathon Electric upon request.

GENERATOR MOUNTING

Two Bearing Generators -- Direct Drive

Two bearing generators are provided with a keyed shaft
extension. For direct drive generators, the assembler
furnishes a flexible coupling which is installed between the

5

ENVIRONMENTAL CONSIDERATIONS

380

219

The MagnaPLUS generator is designed for heavy duty
industrial applications; however, dirt, moisture, heat and
vibration are enemies of rotating electrical machinery.
Excessive exposure to the elements may shorten generator
life. The temperature of the cooling air entering the intake
openings of the generator should not exceed the ambient
temperature shown on the generator’s nameplate.
Generators intended for outdoor application should be
protected with housings having adequate ventilation.
Although the standard insulation systems are moisture and
humidity resistant, space heaters are recommended for
extreme conditions. If the generator is to be installed in an
area where blowing sand and dust are present, the
enclosure should be fitted with filters. Filters reduce erosion
on the generator's insulation by blocking high velocity
abrasive particles generated by the flow of cooling air
through the generator. Consult the factory for appropriate
filters and generator deratings required.

WIRING CONNECTIONS

Wiring of the generator and accessories should be
done in accordance with good electrical practices.
Follow government, industry and association
standards.

The generator conduit box construction allows cable entry
from multiple sides. A hole saw or other appropriate tool
may be used to provide for conduit entrance. Protect the

interior of the generator from shavings when drilling or
sawing. An approved connector must be used in
conjunction with the conduit. To minimize the transmission
of vibration, it is essential that flexible conduit be used for all
electrical entrance to the generator conduit box.

All MagnaPLUS generators are equipped with link boards
(terminal strips) for both internal and external connections.
All connections made to the studs of the link board should
be made with high quality ring terminals. Ring terminal
sizes are: 6 mm (280 Series Frames) and 10 mm (360 and
430 Series Frames). Torque link board connections to the
following specifications: 280 frame -- 5.4 NM (4 Ft Lb); 360
& 430 frame -- 27 NM (20 Ft Lb).

Refer to the connection diagram supplied with the generator
and / or the proper diagrams shown in this manual. Install
all inter-component and external wiring in accordance with
national and local electrical codes. The neutral in the
following connection diagrams shown below may be either
grounded (earthed) or left above ground potential (floating).
See national and local codes and / or the system
distribution wiring schematic diagram for the proper
connection of the neutral.

The following connection diagrams are shown for
twelve lead generators. Ten lead generators have the
same terminal designations except for leads T10, T11,
and T12. These three leads are internally connected
inside the generator and brought out as a single lead
(T0). Ten lead generators can only be connected in a
wye configuration

HIGH (SERIES) WYE CONNECTION

L

1

T

1

VOLTAGE (HIGH WYE)

T

4

T

7

T

T

12

T

9

T

6

T

3

L

3

10

T

11

T

8

T

5

L - N

L - L

T

2

L

2

Hz L-L L-N

60 480 277

460 266
440 254
416 240
380 219

50 416 240

400 231

6