Winco Rotating Armature Design User Manual

TROUBLESHOOTING
ROTATING ARMATURE
GENERATORS

GENERAL INFORMATION

The main components of the generator are: armature, field
coils, cooling fan, brushes, brush holder assembly, end brack­ets, rectifier and voltage regulator. Before performing any
maintenance on the generator, isolate and/or disable the drive
system so the unit can not be accidentally started while being
repaired.

The troubleshooting chart lists various symptoms of poor
generator operation with possible causes and the appropri­ate corrective action. You will need a volt-ohm meter or test
light to check some of the causes. For some of the other
causes you will need to check generator speed. To check
generator speed you can use a frequency meter, a tachom­eter, or a 120V-60Hz electric clock and a correctly operat­ing wrist watch. (Run the electric clock on generator power
and compare the clock’s second hand movement with that
of the wrist watch. They should run at the same speed. If
clock runs faster, generator speed is too high, and vice
versa.)

CAUTION: Equipment Damage

Most electrical equipment in North America operates
satisfactorily at frequencies between 59 and 61 Hz (cycles
per second.) Operating the generator at frequencies outside
that range may cause damage to the generator and/or to
electrical equipment driven by the generator.

Periodical Maintenance

after every 200 hours of operation thereafter. Remove brushes
one at a time and check for length; be sure that each moves
freely in the brush holder. Brushes should be replaced when
worn down to 3/8”. Replace brushes in complete sets, never
singly. When replacing brushes, be careful to reconnect the
lead wires properly.

Poor contact (or “skipping”) between brush and slip ring is
caused by oil and grit, flint, or other hard substance on the
brush, or by the brush not being properly shaped to fit the slip
rings. Remedy these defects by fitting the brushes to the slip­ring curvature. Place # 00 sandpaper under the brushes with
the abrasive side to the brushes, and work it back and forth
until the brushes are the same shape as the slip-rings.

B. Slip rings

The four continuous copper rings located on the end of the
armature are the generator output slip rings. For proper
generator output, the surface of the slip rings must have a
smooth, shiny, highly polished finish. Normal brush seating
will transfer a shiny black finish that will seat the copper
surface. This finish should not be removed unless it
becomes dull or begins to build up. Under sustained use, it
is advisable to check and if necessary, polish the ring
surfaces with a crocus cloth to maintain the smooth finish.

ELECTRICAL TESTING

A. Testing generator fields for opens and grounds.

Service/maintenance items include periodic external physical
inspection for missing hardware or damage to mounting or
drive system and checking the oil level in the gear case. It is
recommended that the generator be operated at least monthly
under normal loads to familiarize operators with the proce­dures and controls as well as to dry out any accumulated
condensation or other moisture in the generator electrical
windings. The maintenance and service attention invested
will insure getting the peak performence that was designed
into the unit.

Routine preventive maintenance minimizes costly repairs
and generator down-time. Before each use, inspect the
generator: gear case oil level should be correct, cooling
vents and screens should be clear, and generator mounting
hardware should be tight. Clean and inspect the generator
after storing it for long periods, and after using it in ex­tremely dusty conditions or in severe weather, such as rain
or blowing snow.

Generator Maintenance

A. Brushes

Under ordinary circumstances, brushes will operate for ex­tremely long periods without requiring replacement. They
should be inspected after the first 500 hours of operation, and

1. Disconnect field leads from rectifier or the regulator.

2. Set multimeter to read resistance, and connect the meter
leads to the field leads. If field is open, meter will read
infinite resistance (very high ohms). Repair or replace field
if it is open.

3. Leaving one meter lead connected to the field, connect
the other meter lead to the field shell. If meter indicates
continuity (any reading -should be infinite resistance). The

field is grounded and should be repaired or replaced. To
determine which of the fields is grounded, cut the connec
tor between the two coils and retest to determine which

B. Testing the Armature for Opens and Grounds

1. Remove all brushes.

2. Ground fault test - set multimeter to read high resistance
(meg-ohms).Holding one meter lead against a clean spot
on the armature shaft, touch the other lead to each of the
slip rings (one at a time) while observing the meter. If meter
indicates continuity (any reading lower than one meg­ohm), the armature is grounded. Dirt between the slip rings
and on the insulator surface can cause grounding. If ground­ing was indicated, carefully clean all dirt off the slip rings and
their insulators and then recheck it. Replace the armature if
it is grounded and unrepairable.

3. Open Test. Set meter to read low resistance (R x 1
ohms). Holding one meter lead on surface of slip ring
No. 1, touch other meter lead to surface of slip ring No.
2 while observing the meter. Meter should indicate
continuity (low resistance - less than one ohm is typical). If
the meter indicates open circuit (infinite resistance) part of
armature winding is open. This may be caused by a
repairable defect in the connection at the slip ring, however
generally an open armature will have to be replaced.
Continue reading the continuity between slip ring No. 2 to
No. 3 and No.2 and No.4. All the slip rings should have
continuity to slip ring number 2, the neutral ring.

NOTE: If these tests have not located the trouble, remove the
armature and have it tested for opens, shorts, and grounds on
a growler.

C. Testing Rectifiers

The field excitation is supplied through a full wave bridge
rectifier. This type of rectifier has four terminals, two AC, a
DC positive and a DC negative.

and red to the AC terminals, each in turn. An opposite
reading should be observed.

5. Connect the red ohmmeter lead to the negative DC (-)
terminal.

6. Connect the black lead to each of the AC terminals in turn.
Either a high or low resistance reading will be obtained.

7. Reverse the meter leads, (black lead to the DC NEG (-)
and red to the AC terminals, each in turn. An opposite reading
should be observed.

8. Check each terminal to the case. An open circuit (very
high resistance) reading should be observed. A battery pow
ered test light is used. Follow the same procedures described
above. A good diode element will allow current to pass to the
light in the test lamp when the leads are connected in the
forward direction.

9. If the rectifier fails any of the above tests, it should be
considered defective and replaced.

Condenser Testing

Condensers are built into the generator circuit to minimize
radio interference during operation. If a condenser shorts out,
it will also short out the generator output. To determine
whether a condenser is shorted, stop the generator and
disconnect the condenser lead wire from the brush holder.
Using a multimeter on the R x 100 scale, check the resistance
of the condenser. Normal response is a sharp swing of the
meter towards low resistance and then a steady rise towards
high resistance (open circuit). If the capacitor is shorted it will
show as a constant low resistance.
Otherwise, restart the generator without the capacitor connected
to recheck the generator for output. If the generator then
provides power, the condenser was at fault and should be
replaced. (If the generator doesn't provide power, the problem
was not caused by that condenser, reconnect the lead wire).

A rectifier may be tested in the following manner:

1. Disconnect all leads from rectifier.

2. Connect the red ohmmeter lead to the positive DC (+)
terminal.

3. Connect the black lead to each of the AC terminals in turn.
Either a high or low resistance reading will be obtained.

4. Reverse the meter leads, (black lead to the DC POS (+)

9089-10

225 South Cordova Avenue
Le Center, Minnesota 56057
507-357-6821

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