Boston gear Ratiotrol P-3026-BG, Installation And Operation Manual, Page: 12 / 21

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P-3026 • Doc. No. 60881 • Boston Gear
®
Ratiotrol
®
DC Motor Speed Control
Maintenance
Troubleshooting
Most electrical failures are caused by incorrect
connections, overload, or the accumulation of
dirt, dust, or moisture. Dirt and dust deposits
limit the transfer of heat from the solid-state
components. Moisture, usually caused by either
"wash-down" or condensation, can cause
insulation failures and short circuits. Be sure
the controller is clean and dry before doing
troubleshooting.
Be sure the AC input power
is turned-off before working in
the controller.
If repeated circuit breaker tripping and/or power
bridge failures occur, check the AC input power
for transients (high level spikes) or rapid power
fluctuations.
If a circuit board fails, check all inputs to the
board for proper values before replacing
the board.
Use standard troubleshooting procedures, e.g.,
continuity checks, to detect faults in relay and
switching logic and operator controls.
Section IV
Table 5 – Troubleshooting
Indication Possible Cause Corrective Action
1. AC POWER ON/OFF switch Wiring faulty or incorrect Check all external wiring terminating
trips immediately when in the controller. Correct accordingly.
turned-on Circuit, component, or wiring grounded Remove unwanted ground.
Power Bridge BR1 shorted Replace BR1
Power board failure Replace power board.
Control board failure Replace control board.
Shunt field shorted or grounded Repair or replace motor.
2. AC POWER ON/OFF switch Power Bridge BR1 shorted Replace BR1.
trips when motor starts to turn
Motor shorted or grounded Repair or replace motor.
Control board failure causing
Replace control board.
SCR’s to turn-on fully
3. AC POWER ON/OFF trips
Overload
Check shunt field current.
while motor is running Insufficient shunt field current
causes excessive armature current.
If field current is OK, check for
mechanical overload. If the unloaded
motor shaft does not rotate
freely, replace motor bearings. Also
check for shorted armature. Correct
accordingly.
Loose or corroded connection. Check AC POWER ON/OFF switch
Wiring faulty, incorrect or grounded terminals and all terminals,
connections, and wiring
between the line, controller
and motor.
Motor shorted or grounded Repair or replace motor.
SCR and/or diode breaking down Replace BR1.
(intermittently shorting) in Power
Bridge BR1
Control board failure causing SCR Replace control board.
false firing or misfiring
WARNING