Rotor; Stator - Kohler 5E Service Manual

11. Set engine speed to 47.5 Hz for 50 Hz generator
sets and 57.5 Hz for 60 Hz generator sets for the
desired cut-in frequency.
12. Slowly turn the volts/Hz pot counterclockwise until
the frequency matches that of the engine
frequency (47.5 or 57.5 Hz) or until the voltage just
begins to drop.
13. Reset the engine speed to the normal frequency
(50 Hz or 60 Hz).
14. Recheck the AC voltage output and stability as
described in steps 5--7.
15. Stop the generator set.

7.3 Rotor

The two-pole rotor creates the magnetic field needed to
sustain alternating current in the stator windings. Before
testing, inspect the rotor for visible damage to pole
shoes, insulation, exposed coil windings, and collector
ring surfaces. Check the rotor bearing for noisy
operation, excessive wear, radial or axial movement,
and/or heat discoloration.
necessary.
Collector rings acquire a glossy brown finish in normal
operation. Do not attempt to maintain a bright, newly
machined appearance. Wipe the collector rings with a
dry, lint-free cloth. Use a commutator stone to remove
the groves on the collector rings. Do not use emery or
carborundum paper or cloth. Remove all carbon dust
from the generator. Remove the black or pitted surface
of the collector rings using a lathe.
Check the rotor for continuity and resistance. Lift the
brushes and measure the rotor resistance between the
two collector rings. See Section 1.5.
Note: When checking rotor resistance with the rotor
installed, brushes must not be in contact with
rotor collector rings. Use a brush retainer on
brushes for accurate resistance readings.
TP-5986 4/03
Replace or repair as
Note: Use the values in Section 1 as a reference for
rotor resistance readings. Take readings at room
temperature or about 21°C (70°F). Rotor
resistance will vary directly with increase in
temperature.
To check whether the rotor is shorted to ground, touch
one ohmmeter lead to either collector ring and the other
lead to the rotor poles or shaft. The meter should
register no continuity.
Repair or replace the rotor if the previous tests detect
any faults.

7.4 Stator

The stator consists of a series of coils of wire laid in a
laminated steel frame. The stator leads supply voltage
to the AC load and exciter regulator. See Figure 7-7 for
coil lead description.
Stator Leads
1--2
3--4
33--44
55--33 Voltage regulator power source
B1--B2
Figure 7-7 Stator Coil Lead Description
Before testing the stator, inspect it for heat discoloration
and visible damage to the exposed coil windings and
varnished areas of the frame laminations. Be sure the
stator is securely fastened in the stator housing.
The stator produces electrical output (AC) as the
magnetized main field rotates within the stator windings.
Test the condition of the stator according to the following
procedure.
Leads 1, 2, 3, and 4 are the generator output leads.
Leads 33, 44, and 55 are the voltage regulator supply
and sensing leads. The output of leads B1 and B2 is the
control voltage for the controller.
Section 7 Generator Troubleshooting
Description
Output coil
Output coil
Control wires from 3 and 4
Controller power source
29