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BOOK 0958-B
26
TABLE 6. TROUBLESHOOTING
INDICATION POSSIBLE CAUSE CORRECTIVE ACTION
One or more SCR‘s or Diode D1b
shorted
Replace shorted devices or the control board.
Motor shorted or grounded Repair or replace the motor.
3. Controller line fuse
blows when a Start com-
mand is initiated
Control board failure causing SCR’s to
turn-on fully
Replace the control board.
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.
Loose or corroded connection. Wiring
faulty, incorrect, or grounded
Check all terminals, connections, and wiring
between the line, controller, and motor.
Motor shorted or grounded Repair or replace the motor.
One or more SCR‘s or Diode D1b
breaking down (shorting intermit-
tently)
Replace faulty devices or the control board.
4. Controller line fuse
blows while the motor is
running
Control board failure causing SCR
false firing or misfiring
Replace the control board.
Minimum speed not adjusted correctly
Turn the MIN SPD potentiometer counter
clockwise.
Motor armature grounded Correct ground fault.
5. Minimum speed
excessive
Control board failure Replace the control board.
Maximum speed set too high
Turn the MAX SPD potentiometer counter
clockwise.
Controller not calibrated correctly Refer to Steps 4 and 5 on page 5.
Open shunt field winding or wiring to
the motor shunt field
a
Check the motor shunt field and associated
circuitry for a loose connection or a broken
wire. Repair accordingly.
6. Maximum speed
excessive
Motor field demagnetized
b
Replace the motor.
Cont’d on next page