TM 55-6115-491-40
CAUTION
Disconnect the leads of the capacitor (4, figure 3-2) from the terminal block (8)
before making dielectric tests.
a. Connect the neutral terminals together and
e. There shall be no grounded circuits or shorts
apply 700 volts (RMS) from terminal T1 to ground for one
between circuits.
minute.
4-20. COMMUTATOR RUNOUT TEST.
b.
With no connections between output
4-21. Using a dial indicator, check commutator runout
terminals, apply 700 volts (RMS) between the following
and bar-to-bar 'difference, by rotating the rotor assembly
sets of terminals: T1 and T2, T2 and T3, T3 and T1
on its bearings. Maximum total indicated runout shall be
c. Check the exciter circuit by applying 550 volts
0.001 inch and maximum bar-to-bar difference shall be
(RMS) from terminal F1 to ground for one minute.
0.0002 inch.
d. Check the permanent magnet generator
4-22. TROUBLESHOOTING.
stator winding by applying 250 volts (RMS) between
4-23. If the generator fails to perform as indicated in the
Terminal PMT and ground for 30 seconds.
preceding tests, consult the troubleshooting chart, table
Table 4-1. Troubleshooting (Sheet 1 of 3)
TROUBLE
PROBABLE CAUSE
REMEDY
Generator voltmeter indicates zero
Defective voltmeter
Replace the voltmeter.
Defective selector switch
Replace the selector switch.
Loose connections in voltmeter circuit
Tighten connections.
Generator switch is "OFF"
Generator switch to "ON."
Insufficient residual magnetism in
Operate "Reset" on control panel.
exciter poles.
Brushes making poor contact with
Seat and run in the brushes. Refer to
commutator or slip ring
Short-circuited or grounded armature
Replace the rotor.
Shorted or open exciter field winding
Replace the exciter stator.
Broken splined shaft
Replace the shaft.
Shorted or open field winding in AC
Replace the rotor.
generator
Shorted or open AC stator winding
Replace the complete housing and
stator.
Table 4-1. Troubleshooting (Sheet 2 of 3)
TROUBLE
PROBABLE CAUSE
REMEDY
Generator fails to deliver full power to
Line contactor open
Close the line contactor
system
Shorted field winding in rotor of AC
Replace the rotor.
generator
Shorted armature in exciter rotor
Replace the rotor.
Shorted exciter field
Replace the exciter stator.
AC stator winding shorted
Replace the complete stator.
Excessive output voltage modulation
Poor brush contact
Seat and run in brushes. Refer to
Intermittent-short or open in exciter field
Replace exciter stator.
Intermittent short in exciter armature
Replace the rotor. coils
Intermittent short or open in field of AC
Replace the rotor.
generator
Malfunctioning voltage regulator
Replace the voltage regulator.
Loose connections between generator
Tighten the connections.
and exciter field
Loose connection to commutator or slip
Tighten the connection.
ring brushes
Change 1 4-8
