Gillette SRVM3 SERVICE MANUAL

SERVICE MANUAL

FOR

BRUSHLESS GENERATORS

SRVM3

GIL-MAN-933-20120823

2.2 KW THROUGH 15 KW

Gillette Generators, Inc.

2921 Thorne Drive • Elkhart, IN 46514

Web Site - http://www.gillettegenerators.com

E-mail - [e-mail]

Technical Support (8

00) 777-9639

Phone - [phone]

FAX - [phone]

TABLE OF CONTENTS

SUBJECT PAGE

Safety Precautions 2-3
Description of A-C Generator Operation 4
Scheduled Maintenance 5
Generator Repair Procedures 5-9
Generator Dis-Assembly and Re-Assembly 10
Parts Identification 11-23
Wiring Diagrams 24-28
Warranty for K2N & BDN2, O.E.M Generators 29
Warranty for Complete Portable Generator Sets 30

SAFETY PRECAUTIONS

This service manual describes only the methods of repai r
concerning the gene rator. Always refer to the engine
manufacturer's repair manual for its o wn repair
procedures.

Read through this m anual. Then carefully follo w all
recommendations and safety precautions to keep the
generator functioning properly and to avoid any serious
body injury.

WARNING!

!

MOVING PARTS! Keep hands, loose clothing, necktie,

hair or test lead s well a way from all moving items a s
serious injury could result from enta nglement. Never run
generator or engine with guards o r protective covers
removed.

WARNING!

!

LETHAL EXHAUST GAS! The running engine

releases deadly carbon monoxide as part of the n ormal
exhaust gas. This poiso nous carbon monoxide gas is
particularly dangerous because it is odo rless and
colorless. Never operate the ge nerator set i nside a
building unless this exhaust gas is safely piped o utside
and the proper amount of free fresh air is allowed to enter,
ventilate, and leave the building. Ne ver operate engin e
where exhaust gas may travel insid e occupied building.
Avoid breathing fumes when working on or near generator
set. Use extreme ca ution when ope rating gen-set with
LPG, PROPANE, or NATURAL GAS fuel. Always consult
your local gas co mpany and fire departm ent before
operation is begun to confirm sa fe installation and
operating conditions.

(2)

WARNING!

!

BURN HAZARD! All e ngine parts and muffler will get

extremely hot while running. Com plete engine should be
allowed to cool down before set is worked on and
repaired.

WARNING!

!

HIGH VOLTAGE! The job function of the genera tor is

to produce electricity, and wh enever this en ergy is
present, there is the pot ential of ele ctrical shock and
death by electro cution. No one, e xcept trained and
qualified repairmen, should be allowe d to work o n the
generator. Keep everyone, especially children, a way
from unguarded or running set. Wirin g should be
inspected frequently. Rep lace any leads that are fra yed
or in poor condition. Be sure that generator and plugged
in equipment are pro perly grounded. Do not operate
electrical equipment when standing in water, wet ground
or when your hands are wet.

WARNING!

!

FIRE HAZARD! Avoid flash fire. Do not smoke or allow

flame or spa rk near en gine. Never try to fill engine fuel
tank while the engine is running. Safely empty fuel tank
before tipping engine to drain oil. Always u se a safe,
portable, vented fuel tank that is designed for the purpose
of storing or hauling fuel when filling the en gine mounted
fuel tank. Wipe up any fuel spill age before operating
engine. Never allow chil dren or other u nqualified people
around or near this equipment.

WARNING!

WARNING!

!

DANGEROUS FUELS! Use extre me caution when

handling, storing and using fuels. All fuels a re explosive
in a vapor condition. Store all types of fuel in a well
ventilated area away from all flames, sparks, and
children. Ne ver add fuel t o tank while engine is running
since spilled fuel may ig nite from ig nition spark or hot
engine parts. Keep fuel lines in tight and in good
condition. Don't use rigid fuel lines in place of the original
flexible fuel lines. Do not operate generator set when fuel
spillage, fuel leakage or electrical sparks are noticed.

GASOLINE - Always store gasoline in approved red

containers that are cle arly marked "ga soline" and having
proper venting. Don't store gasoline in occupied building.

WARNING!

!

DANGEROUS ACID! Avoid all c ontact with battery

electrolyte. It contains a dang erous acid which can burn
skin, burn holes in clothing, and cause permanent damage
to eyes. Al ways wear protective safety goggles when
working around batteries. If battery electrolyte is splashed
in the eye s or on skin, i mmediately flush area for 30
minutes with large qua ntities of clean fresh water. Seek
immediate medical aid in event of eye contact. Never add
battery acid to a battery that is in service as it may result in
dangerous splattering of electrolyte.

!

EXPLOSIVE BATTERY GASES! A battery under

charge can emit highly explosive gases. Do not smoke or
permit flame or sp ark near battery, esp ecially when it is
being charged. Avoid contacting b attery terminals with
tools to prevent burns o r sparks that could cause an
explosion. Remove all jewelry befo re handling battery to
avoid burns. Battery compa rtments should be well
ventilated to prevent accumulation of explosive gases.

WARNING!

!

HIGH VOLTAGE! The capacitor contains high voltage.

Use extreme caution wh en handling the capacit or as
electrical shock can result. Always di scharge capacitor
before handling by placing an insulated handle screwdriver
across capacitor terminals.

WARNING!

!

ELECTRICAL SHOCK! When "flashing" the generator

by applying 12 volts DC battery voltage to ca pacitor
terminals, be careful to avoid touching any b are and
exposed battery and cap acitor terminals as dan gerous
electric shock is present.

WARNING!

!

ELECTRICAL SHOCK! A battery can cause electrical

burns and shocks. Use e xtreme care when working on
batteries to avoid elect rical connections through tools,
wristwatches, rings, or any other type of jewelry.

Always use factory supplied, original parts. Substitution parts
often cause m ore failures resulting in eq uipment down-time,
due to lower values of look-alike components.

You can rel y on 24-hour shipment of common rep air parts of
these “brushless” generators.

Call us a nd ask for our parts manag er to obtain a ny part you
may require.

WARRANTY CLAIM: Notif y factory before any attempt is
made to repair a Gen-Set. D efective parts must be se nt to us
for inspection before warranty claim is approved.

WARNING!

!

DANGER OF ELECTROCUTION! Some of the test

procedures require that the generator set be running while
tests are performed. Extreme caution must be used when
making these tests as potential electric shock is present.

This manual and the manufacturer cannot possibly anticipate
every possible happening that might i nvolve a hazard. T he
listings, warnings, and ca utions in this man ual and on tags
and decals affixed to the equipment are, therefore, NOT ALL
INCLUSIVE. If a certain procedure, work method, test method
and operating procedure that are n ot recommended by this
manual and by this manufacture r is used, you must assu me
all responsibility that it is safe for y ou and for all others. You
must also b e sure that the generator will not be harmed or
damaged or made unsafe by the procedure, work, or method
you have chosen. If y ou modify or change this equipment in
any way from the origin al design, you must assume all
responsibility for its safe operation.

(3)

DESCRIPTION OF A-C GENERATOR OPERATION

A-C GENERATOR

The A-C ge nerator converts the mecha nical energy from
the engine t o electrical power. The re are fou r major
components involved in the bru shless "Power-Assist"
generator set. The construction of each m ajor part is
described in detail.

POWER GENERATION

The rotor windings are initially charged with a D-C voltage
and permanently retains a residual magnetic flux. Duri ng
start-up, an initial flow of electric current is induce d in the
winding of the capa citor coils (l ocated in the stator). The
lines of m agnetic flux, fro m the ch arged rotor, are cut by
the stator field coil windin gs. This induced flow of current
and voltage is very low.

As the engin e increases in spe ed, the voltage indu ced in
the capacitor windings rises. An alternating curren t flows
in these windings. The rising and falling magnetic field
from this cu rrent is cut by the field coils in the rotor,
inducing an excitation voltage. A dio de (rectifier) in the
rotor field winding rectifies the current from A- C to D-C.
The D-C current in the rotor field generates its own
magnetic field which sweeps past the main power
windings in the stator. This swe eping magnetic field
induces the rated voltage in the main winding as long as
the rotor is turning at the correct speed.

When the el ectric load is con nected to the main power
winding, the cap acitor coil circuit will tend to preve nt the
main winding voltage from falling; therefore, acting as a
capacitor regulator.

This innovative voltage stabilizin g effect is calle d "Power­Assist" and is an exclusive design with these products.

GENERATOR CONSTRUCTION

Each generator component is d escribed in detail. (See
Figure 1)

THE ROTOR

The engine end of rotor inner shaft is tapered and is
connected directly to the male taper of engine crankshaft.
This end is supported by the en gine crankshaft ball
bearing. The opposite end of roto r is supported by a ball
bearing in the bearin g bracket. There are two in dividual
coils wound on the roto r. These two windings create a
permanent magnetic field for the main stato r power
winding. Wh en the gen-set is working with the cap acitor
removed, this rotor winding will generate approximately 8 ­12 VAC at 120 VAC normal output and 16 - 24 VAC at 240
VAC normal output in mai n winding, due to what is called
“Residual Magnetism”.

THE STATOR

The stator is a cylinder and the inside diameter is sl otted
lengthwise. The win dings of both main power and
capacitor coils (called exciter windings) are placed in these
stator slots. The mai n power windings are connected
directly to the output re ceptacles. The exciter winding will
produce power for the rotor field and are co nnected
directly to the capacitor.

THE CAPACITOR

This device is connected in series with the exciter winding,
and its only purpo se is to act as a voltage re gulator,
preventing voltage drop when load is applied.

THE DIODE

Two diodes (rectifiers) form a full wave rectifier ci rcuit to
convert the induced A-C current to D-C current for full rotor
field excitation. Both diodes are lo cated on a disc heat­sink in the cooling air flow and are oversized seven time s
required capacity for complete fail-proof design.

(4)

FIGURE 1

SCHEDULED MAINTENANCE

Scheduled maintenance is "preve ntative maintenance".
Major repairs can be avoided by correcting problems when
they are small. Always look for signs of potential trouble,
such as loose electrical connections, loose ha rdware or
loose mechanical connections. Loose screws and bolts,
bad fuel connections. Always test the GFCI receptacles (if
your gen-set has them) before each use.

ITEM OF INSPECTION AND SERVICE

Operate in only dry, well ventilated areas.
Inspect for broken or dirty receptacles.
Remove inspection cover and view windings

for burned or dirty windings.
Tighten all stator thru-bolts, rotor thru-bolts.

Inspect wiring for frayed or damaged insulation.
Tighten all screws on all receptacles. Inspect connections to
capacitor. They must be tight.
Remove all ground wires, clean wire terminals and ground
location. Re-assemble ground wire.

GENERATOR REPAIR PROCEDURES

When running the generator set, note any unusual n oises
or unusual smells. Alwa ys follow all safety precautions
listed in the front of thi s manual. Refer to tabl e on this
page for sche duled maintenance of the generato r.
Perform each function at the indicated time interval. Refer
to engine manual for its individual service requirements.

BEFORE

EACH START

EVERY 50

HOURS

EVERY 200

HOURS

x
x

x

x

x
x

GENERAL

When repairing the generato r, always con sider the
simplest possible causes first. Narrow the problem down
to a specific function al system. For a generator to work
properly, all internal and external parts must be clean. All
electrical connections must be tight. If the generato r
produces no electrical power, check the following possible
causes in t he exact sequence of (10) repai r steps,
beginning with the most frequent problem, before the gen­set is dis-assembled.

STEP 1. Engine Speed: Improper low engine speed

setting is ve ry common and re sults in being the main
problem in a no voltage condition. This should be the first
item to check. Determin e the engine speed at no load
applied to generato r with a tachometer or other qu alified
speed indicator. The en gine must be running at 3750
RPM (± 60 RPM) or in t he case of a special 50 cycle
winding, the running speed must b e at 3150 RPM (± 50
RPM) for proper voltage output.

The brushless "Power-Assist" winding is de signed to
produce no voltage output if engine speed is reduced 15%
or more (3 100 RPM at normal speed of 3750 RPM 60
hertz or 2600 RPM at n ormal speed of 3150 RP M 50
hertz) below required speed. Thi s design feature
eliminates the problem of low voltage output at low speeds
which is a co mmon problem with comp etitor's generators
and which may result in damage to the plugged-in electric
load.
Proper speed setting can also be id entified by n o load
voltage output of 122 - 125 volts or no load frequen cy
output of 62 hertz. If speed setting is prop er and not the
cause of no voltage out put, proceed to the next repai r
step, #2.

STEP 2. Open Circuit Breaker: The A-C mainline

circuit breaker acts to protect the main power wi nding. It
will trip open immediately upon short circuit and trip open
within 30 seconds at approximately 15% overload. To
restore A-C output, close circuit brea ker. Reduce the
amount of electric load if breaker continues to trip open. If
generator has no electric load applied and breaker
continues to trip, replace defective breaker.

If you are operating the gen -set when ambient
temperatures are higher than 105 F, the thermal brea kers
will automatically trip as a normal function. Do not operate
generator in these hot con ditions. If the circuit breaker is
determined not to be the cause, proceed to the next repair
step, #3.

STEP 3. Open or Shorted Capacitor:
Our voltage regulating capacitors are of one common size,
50 mfd at 4 40 volts. T hey can be used in a ny size
generator for complete interchangeability. If this capacitor
is open or shorted near to no voltage output will result.
Always handle or te st the capacitor when the engine is
stopped. Extremely high voltage is prese nt at the
capacitor terminals while generator is in use and these
terminals should not be touched as a potential e lectric
shock condition exists. Also, when engine is stopped, the
capacitor will still contain high voltage. Use extrem e
caution when handling capacitors. A potential shock
condition still exists if saf e handling procedures are not
used. Always discharge the capacitor before handling by
placing a conductor, such as an insulated handle
screwdriver, across the capa citor terminals while h olding
on to insulated handle only. This will short out the voltage
stored in capacitor, thus discharging the capacitor. A loud
audible noise will result when capacitor is discharged.

(5)

With the engine stop ped, remove the protective plasti c
cover from capacitor lead connections. Discon nect both
red capacitor winding leads from the capacitor. Check the
capacitor "charge and discharge" readings using an
ohmmeter on the RX-100 scale. (See Figure 2)

When the ohmmeter lea ds are pla ced on the capacit or
terminals, a meter deflection should be seen (cha rging)
followed by a slow return to infinity (discharging). Reverse
the ohmmeter leads and repeat the procedu re for the
same results. No meter deflection or continuing continuity
indicates an open or shorted capacitor.

All capacitors have an internal, built-i n circuit brea ker. If
capacitor becomes "shorted", this internal circuit breaker
trips open and causes the entire top portion (where
terminals are located) to become extremely convexed or to
push outward. When this happ ens, the cap acitor is bad
and must be replaced.

CAUTION: Inspect connection of red wires to capacitor
terminals. They must be sold ered rigidly tight. Repair or
replace any loose or poor connections. If there i s no
method to check the cap acitor, check the Yellow Page s
and call any electric motor repair shop. They have the
equipment to test cap acitors. If the capaci tor is
determined not to be the cause, proceed to the next repair
step #4.

lost. As the generator is brushless, the field cann ot be
"flashed" in the normal way.

The residual magnetism can sometimes be restored by
connecting a full electric l oad to the re ceptacles and then
manually increase engine speed to approximately 4500
RPM for two se conds. This all ows the com pounding
system to assist the full load circuit with a resulting
increase in the effective residual voltage. This is the quick
method and sometimes it does not work. If residu al
magnetism of 4-6 volts is not resto red, proceed to actua l
"flashing" of the rotor winding.

The generator set should be run at normal no-load speed,
A 12 VDC battery should then be instanta neously
"flashed" ("touched" for only one second) across the
capacitor terminals. Pola rity is of no con cern. Th e red
leads should remain connected to the cap acitor. The
output voltage should then build up to normal levels. (See
Figure 3.)

Caution: Flashi ng the field has resto red voltage o utput;
but when set is stopped and restarted with resultin g no
voltage output, then check engine speed as it is too low.

A potential shock hazard exists when handling battery and
battery jumper leads. Never wear jewelry, or use tools, or
metal items that may make cont act across battery
terminals. Revie w safety rules at the begin ning of this
manual.

If residual m agnetism was not the problem, pro ceed to
next step, #5.

FIGURE 2

STEP 4. Loss of Rotor Residual Magnetism-Flashing
Field: The rotor windings have b een "charged" with a

powerful D-C current, and it will hold a residual magnetism
within its metal lamination stack. When every comp onent
in the rotor system (roto r windings and diodes) are good
and engine speed is correct, an A-C voltage of 8 -12 volts
on 120 VAC and 16 - 24 volts can be measured at the 240
VAC load lin es of stato r power outp ut leads. Wit h no
voltage present, or o ne-half or le ss of above designated
voltage, it can be presum ed that resid ual voltage is lost,
and the rotor winding must be re-energized or "flashed".

If the rotor h as been removed or the generator has been
stored for over six months, the rotor' s magnetism may be

(6)

FIGURE 3

STEP 5. Receptacle Panel Wiring: Inspect the
receptacle panel for worn or loose wires. Make sure all
wires are se cure and tight at the screws of recep tacles.
Do not allow wires to be pinched, kin ked or damag ed in
any way. Inspect for tight connections at circuit breakers,
capacitors, and all receptacles. Rep lace any broken
component. Test any GFCI receptacles by use of its built­in test and reset buttons. Panel wiring must conform with
diagrams as shown on Page 28 through 33. If panel wiring
checks good, proceed to next repair step, #6.

STEP 6. Open, Shorted, or Grounded Stator Main
Windings: The stator is the outside stationary winding as

shown in Figure 1. It consists of copper wire laid in a steel
laminated frame. To remove stator assembly, follow dis­assembly instructions, part #1 through #5, on page 10.

The stator windings form two main poles and have four
coils per pole with two lead wire s connected to each pole
winding. The large black lead wires are numbered #1 and
#2 for one field pole; #3 and #4 for the other field pole . To
test the main powe r winding, disconnect all lead wires.
Set ohmmeter to lowest O HM x 1 scale. Place one meter
test lead on #1 lead of stator winding and the other test
lead on #2 lead of stator winding. (see fig. 4) Then record
this resistance value. Measure resistance values of leads
#3 and #4 of the second main pole winding. Record all
values and check them with resistance chart on Page 8.

When testing for resi stance, also test for gro unded field
coils. One ohmmete r test lead stays on field coil lead
while the other test lea d is touched to a good "g round"
surface of the metal frame bracket hol ding these coils. A
reading of th e ohmmeter indicates a bad condition of a
ground field coil and stator assembly should be replaced.

CAUTION: Make sure all leads are disconnected and
free. The #2 & #3 main field coil leads are intenti onally
grounded to form a neutral and will g ive meter a false
reading.

Grounded field coils indicate defective stator.

No reading or resistance values when testing between two
lead wires (#1 and #2 or #3 an d #4) indicate an open
stator, and it should be replaced.

Check all met er resistances with chart resistances on
Page 8. A quick test for the entire stator winding assembly
is to disconnect the two red wires from the capacitor. With
capacitor out of the circuit, conne ct 12 VDC to the se two
red wires an d start the g en-set. If you measure 30-40
VAC from 240 volt rece ptacle with an AC voltmeter, the
main winding, the rotor, a nd the capa citor are goo d; but
the exciter winding (wound on top of the main winding) is
bad. This requires a complete replacement of stator
assembly. If stator main windi ng tests good, pro ceed to
next repair step, #7, for further stator tests.

STEP 7. Open, Shorted, or Grounded Stator Exciter
Winding: The exciter windi ng is laid directly on top of

main winding inside stator assembly. It has two coil s per
pole and is conne cted to two re d lead wires. Same test
procedures as described in Item 6 a re used to test the
exciter winding. Disconnect and remove the two red wires
from the capacitor. Mea sure resistance across the se red
wires that lead into stator winding an d test for grounded
exciter winding.

Test also for continuity between red wires and all main
power winding leads, having lead #1 - #2 and # 3 - #4. If
meter shows reading, the exciter winding has shorted
(made connection) into the main power winding, and stator
is defective. The red wires should not have any continuity

with any of the four black wires, and they should not have
continuity with a good ground surface.

Check all resistance values with the resistance chart found
on Page 8. If complete st ator winding is not the problem,
proceed to the next repair step, #8.

STEP 8. Open, Shorted or Grounded Rotor Winding:
The rotor assembly consists of two separate coils with two
diodes mounted on a special heat-sink disc. For thi s test,
it is necessary to remove the bearing bracket and stator so
there is room to work on the rotor.

Prior to te sting, visually i nspect windings for dark streaks
(shorted), check ball b earing by h and rotation. If it is
rough, noisy or dry, re place bearing. Try a quick
resistance test by placing ohmmeter t est probes across
the solder connection of each diode (rectifier) that is
mounted on rotor. The resulting resistance must compare
with rotor resistance as listed on chart as sho wn on Page

8. If resistance does not co mpare, further testing is
required by removing the diodes from the rotor winding.

The two copper wires must be removed from the tip of the
diodes where they are soldered. Remove these wires with
the aid of a solder gun being careful not to brea k any
copper wires. With copper wires free, check each coil with
an ohmmeter on its lo west OHM x 1 scale. Record this
value and compare it with the roto r resistance chart on
Page 8.

Also test each coil to ground: One meter test lead to coil
wire and the other test lead to the metal bracket that holds
these coils. An ohmmeter reading indicates a grou nded
defective rotor, and it should be replaced. (See Figure 4)

Always inspect all stator and rotor windings for clea n
condition. Windings that are covered with mud, dirt, paint,
and chemicals may test good; but they won't last long
unless they are clean ed with an approved electrical
cleaner then resealed with an air dry electrical varnish.

STEP 9. Diode (Rectifier): The ex clusive and unique
design of this "Power-Assist" brushless generator is the fail

-proof diode system. It is hig hly unlikely that a diode
should ever have to be replaced. Thi s is why the diode
testing is reserved for the last test. Diodes are the number
one replacement problem with all other porta ble gen-set
brands. Ou r 1600 volt, 25 amp diod e capacity resists all
spike problems, and it is a rare o ccurrence to have these
special diodes fail. Ho wever, the repairman must be
familiar with the function and repair of these diodes. Page
28 shows the diode position and connection.

A diode can “SHORT” or “OPEN” to become defective. A
shorted diode is the most common defect in competitor’s
generators, but not in this design, due to highly over-rated
diode values. Howeve r, one or b oth diodes, as well as
windings, can be destroyed if utility power i s allowed to
enter the gen-set. If gen-set is used for emergency power,
with no isolating transfer switch, the return of utility power
will enter the gen-set system.

(7)

If the engine no load speed is norm al 3750 RPM but
output voltage is only half the normal volts, one of the two
diodes may be open, It is necessary to determine whether
this voltage is a result of an o pen diode or is due to a
defective rotor or stator winding. Suspe ct a defe ctive
capacitor if both diodes and windings are good.

Use an ohmmeter in the lowest scale OHMS x 1 position.
Test the dio de in the forwa rd (positive) position. The
ohmmeter should read approximately 15 OHMS (or close
to zero). Reverse the ohmmeter test leads and read over
2000 ohms (or close to infinity). (See Figure 4.)

Simply put, regardle ss of meter polari ty, the ohmmeter
reading should be ze ro in one direction and infinity in the
opposite direction (reversed meter test leads). The same
infinity reading in both direction s indicates an open d iode.

Many other conditions may happe n to cau se no voltage
output with no apparent reason:

A) If generat or has be en under water or left in a severe
rain, the insulation system is soaked and will ground out if
used. The generator must be taken apart and both stator
and rotor must be oven baked at 300ºF for 3 hours.

B) If generator windings have been exposed to salt water
(road salt or sea water), a condition b etween exciter and
main winding will create a certain val ue of capacitance,
nullifying standard cap acitance. The windi ngs must be
cleaned and baked dry, as described in item (A).

STATOR, ROTOR, AND

DIODE RESISTANCE

MEASUREMENT

METHODS

A zero reading in both directions indicates a shorted diode.
Both examples indi cate a defective diode and sho uld be
replaced. When on e diode is defe ctive, it is advised to
replace both diodes as the rem aining may have been
weakened. Use a sol dering iron to soften solde r and
remove the copper conductor wires from the diode. When
re-soldering copper wires to new diode, be careful n ot to
damage, crack, or break the copper wires. Do not allow
heat of sold ering iron to remain on diode for over ten
seconds or diode damage may result.

NOTE: Dep ending on meter manufa cturer, the red and
black leads may be reversed in location as sho wn in
Figure 4. If diodes test good, pro ceed to the next r epair
step, #10.

STEP 10. Actual component testing is no w complete.
Defect or pro blem should have been found during these
repair steps #1 through #9. If probl em exists, call service
department toll-free [phone] and ask for additional
repair help.

GENERATOR SIZE MAIN WINDING CAPACITOR WINDING ROTOR WINDING

AND KW RATING MINIMUM MAXIMUM MINIMUM MAXIMUM MINIMUM MAXIMUM

2.8 AND 3.0 KW, 2 1/2

LAMINATION LENGTH

4.0 KW, 3”

LAMINATION LENGTH

5.0 KW, 3 7/8”

LAMINATION LENGTH

6.0 KW, 4 1/4

LAMINATION LENGTH

6.5 AND 7.5KW, 4 3/4

LAMINATION LENGTH

9.0 KW, 5 1/2”

LAMINATION LENGTH

10.5 KW, 6”

LAMINATION LENGTH

12.0 KW, 6 1/2”

LAMINATION LENGTH

15.0 KW 7 3/4”

LAMINATION LENGTH

18.0 KW 10”

LAMINATION LENGTH

CAUTION: THESE RESISTANCE VALUES ARE VERY SMALL AND TESTING REQUIRES A GOOD QUALITY LOW RESISTANCE READING METER. ALL METER
READINGS OF ZERO INDICATE AN OPEN(BAD) W INDING. ALL METER READINGS FROM WINDING TO METAL FRAME(GROUND), INDICATE A GROUNDED
(BAD) WINDING. ROTOR RESISTANCE IS MEASURED ACROSS EACH SOLDER JO INT OF THE TWO DIODES, WHICH ARE CONNECTED IN PARRALLEL WITH
ROTOR COILS. TO DETERMINE RESISTANCE OF EACH SINGLE POLE, MULTIPLY CHART RESISTANCE X 4, THEN ÷ BY 2.

(8)

.905 .915 1.625 1.635 .850 .870

.568 .563 1.942 1.947 .905 .875

.365 .370 1.455 1.460 .710 .730

.343 .348 1.227 1.232 .735 .755

.247 .252 1.446 1.451 .832 .852

.169 .174 1.218 1.223 .515 .535

.130 .135 .563 .568 .555 .575

.119 .124 .562 .567 .587 .607

.092 .097 .449 .454 .655 .675

N/A N/A N/A N/A N/A N/A

FIGURE 4

QUICK REFERENCE GENERATOR FAULT GUIDE

SYMPTOM POSSIBLE CAUSE REMEDY

Generator rotor speed is too low.

Circuit breaker is tripped open.

Increase engine speed to 3750 RPM,
62 hertz, 125 volts, no load setting.

Reset breaker, Check GFCI receptacles
for proper operation

No Output Voltage,
or a small, 16 to 24 VAC,
as measured on two hot

positions of 240 VAC receptacle

Low Output Voltage

High Output Voltage

Open, shorted capacitor or red leads
disconnected from capacitor.

Loss of rotor residual magnetism.
(A reading of approximately 16 - 24 volts
AC, indicates residual magnetism)

Defective receptacle panel.

One or both diodes open or shorted.
(see figure 4)

Open or shorted main power windings. Replace stator.

Open or shorted capacitor windings. Replace stator.

Open or shorted rotor winding. Replace rotor.

No load voltage between 8 - 12 volts at
correct operating speed, on 120 VAC

Engine speed slightly below operating
speed but enough to collapse all output.

Rotor winding wire broken off at diode
solder joint.

Rotor slipping and free wheeling on engine
crankshaft.

Rotor winding partially shorted. Test rotor winding. Replace rotor.

Generator rotor speed too high.

Higher micro-farad size capacitor is used.

Replace capacitor or connected leads.

Restore magnetism by loading generator
or flashing rotor fields.

Inspect all wiring and components on
receptacle panel. Repair or replace

Replace both diodes

One diode is open . capacitor is defective
or exciter winding is bad.

Increase engine speed to 3750 RPM,
62hertz, 125 volts, no load setting.

Re-solder copper wire to diode.

(1) Tighten rotor thru-bolt.
(2) Possible broken engine crankshaft.

Reduce engine speed to 3750 RPM,
62 hertz, 125 volts, no load setting.

Check capacitor size. It should be 50 mfd.,
440 volts.

Some generators have multiple copper

Test resistance measurements - replace
stator.

Replace diodes.

The No Load Voltage Output

wires in field coil. One or more of these
individual wires may break off the
connecting lead wire.

Rotor diodes have a partial loss of blocking
characteristics but still tests good.

is at normal reading but drops

down as electric load is applied.

Engine is in need of repair. Carboned
cylinder head, bad fuel, or defective engine
governor will reduce effective horse power.

The connected electric load has an
unacceptable power factor, below .7
lagging inductive load.

Have authorized repair station test engine.

Correct the power factor to be between .9
and 1.0.

If diode has shorted to conduction of both directions, the residual magnetism of rotor field may have been destroyed
and it may be necessary to “flash” the exciter winding.

The generator set may be limited by the horsepower rating of the engine. As a guide, the engine has to supply (2)
horsepower for each 1000 watts of power.

Rotation can be in either direction. There is no voltage output when engine speed drops 20% below normal 3750 rpm
62 hertz duty or 3150 rpm 52 hertz duty.

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