
SEBU8219-01 129
Maintenance Section
Winding - Test
Table 19
Tools Needed
Part Number Part
(1)
Quantity
6V-7070
Digital
Multimeter
1
146-4080
Digital
Multimeter
(RS232)
1
(1)
Only one multimeter is necessary for this test. Either of the
multimeters that are shown will work.
The high voltage that is produced by an operating
generator set can cause severe injury or death.
Before performing any maintenance or repairs,
ensure that the generator will not start.
Place the engine c ontrol switch in the “OFF” posi-
tion. Attach “DO NOT OPERATE” tags to all start-
ing controls. Disconnect the batteries or disable
the starting system. Lock out all switchgear and
automatic transfer switches that are associated
with the generator.
Measure the resistance of the following windings:
(L1), (L2), (L3), (L4), and (L5). The winding that
is being tested must be disconnected from the
other components before the resistance can be
measured. The following resistance measurements
are approximations. If the measured value is
not near the listed approximation, the winding is
probably damaged. For a more precise resistance
value, consult the Technical Marketing Information
(TMI). Refer to the generator arrangement that is in
question.
Note: The winding temperature affects the
resistance. When the winding temperature increases,
the winding resistance also increases. When
the winding temperature decreases, the winding
resistance also decreases. Therefore, a correct
measurement can be performed only when the
winding is at room temperature.
The following armature windings have very little
resistance: (L2), (L4), and (L5). The resistance of
these windings will measure near 0 ohms. Use a
milliohmmeter to measure the resistance of the
armature windings.
Exciter Armature (Rotor) (L2) – less than 0.1 ohm
Main armature (Stator) (L4) – less than 0.1 ohm
Pilot Exciter Armature (L5) – less than 0.1 ohm
Use a multimeter in order to measure the resistance
of field windings (L1) and (L3).
Exciter Field (
Stator) (L1) – approximately 3.0
ohms to 6.0 ohms
Main Field (Ro
tor) (L3) – approximately 0.75 ohms
to 2.0 ohms
Note: There sh
ould be no continuity between any
winding and ground. There should be no continuity
between any winding and another winding.