Boston gear Ratiotrol P-3026-BG, Installation And Operation Manual, Page: 14 / 21

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P-3026 • Doc. No. 60881 • Boston Gear
®
Ratiotrol
®
DC Motor Speed Control
Maintenance
Table 5 – Troubleshooting (con't)
Indication Possible Cause Corrective Action
8.Unstable Speed IR compensator misadjusted See "Adjustment Instructions".
(Con’t) SCR(s) misfiring or false firing Replace Power Bridge BR1
and/or control board.
9. High, unstable speed, Armature and field connections Check controller-to-motor
low torque interchanged wiring.
Power Bridge BR1 failure Replace BR1.
10. Top speed only 1/2 Power Bridge BR1 failure Replace BR1.
(approximately) of motor base
speed and motor noisy
(possible half-waving) Faulty control board Replace control board.
11. Motor surges when starting Open or faulty K1 Relay contact Replace Relay K1 or the power
board. Contact must close between
starts.
Power Bridge BR1 breaking down Replace BR1.
(shorting intermittently)
Faulty control board Replace control board.
12. Line and armature current Overload Check shunt field current.
excessive Insufficient shunt field current
causes excessive armature
current. If field current is OK,
check for mechanical overload. If
unloaded motor shaft does not
rotate freely, replace motor
bearings. Also check for shorted
armature. Correct accordingly.
13. Shunt field current insufficient Open shunt field winding or wiring Check motor shunt field and
to the shunt field associated circuitry for loose
connection or broken wire.Repair
accordingly.
Power Bridge BR1 failure Replace BR1.
14. Shunt field current excessive Power Bridge BR1 failure Replace BR1.
Shunt field windings shorted Check shunt field current and/or
measure shunt field resistance
and compare with motor data
plate. Repair or replace motor.
15. Motor thermal switch open Ventilation insufficient Free the motor intake and
(if used) exhaust screens from dirt, dust
and debris.
Motor armature drawing Check shunt field current.
excessive current Insufficient shunt field current
causes excessive armature
current. If field current is OK,
check for a mechanical overload.
Correct accordingly. Motor fields
should be connected for low
voltage.
Motor overheating from friction Check for misalignment. Realign
motor.
Shorted motor windings or Repair motor.
faulty bearings
Section IV