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BOOK 0958-B
28
TABLE 6. TROUBLESHOOTING
INDICATION POSSIBLE CAUSE CORRECTIVE ACTION
9. Line and motor arma
ture current excessive
Motor overloaded
Check shunt field current.
a
Low shunt field
current causes excessive armature current. If
field current is adequate, check for a mechani
cal overload. If the unloaded motor shaft does
not rotate freely, check motor bearings. Also
check for a shorted motor armature. Motor
overload can also be caused by incorrect gear
ratio. Correct accordingly.
Open shunt field winding or wiring to
the motor shunt field
Check the motor shunt field and associated
circuitry for a loose connection or a broken
wire. Repair accordingly.
Shunt field connected for incorrect
voltage
Check motor rating and refer to Table 12 on
page 34.
10. Shunt field current
a
too low
Diode D39, D40, D41, or D42 failure Replace faulty diode or the control board.
Shunt field connected for incorrect
voltage
Check motor rating and refer to Table 12 on
page 34.
11. Shunt field current
a
too high
Shunt field windings shorted
Measure the shunt field resistance and com
pare with the motor rating. Repair or replace
the motor.
Ventilation insufficient
Remove dirt, dust, and debris from the motor
intake and exhaust screens.
Excessive motor load at low speed Reduce the load or increase the speed.
Line and motor armature current
excessive
See Indication 9.
Motor overheating from friction Check for misalignment. Realign the motor.
12. Motor thermal guard
tripped (if used)
Shorted motor windings or faulty bear-
ings
Repair or replace the motor.
a. Does not apply to permanent-magnet motors.
b. Does not apply to shunt-wound motors.