Troubleshoot AC Motors – Part 1

Posted 3/1/2004

Problem A – Motor won’t start or motor accelerates too slowly

A1: Check input power to starter. Is there power on all lines? (Three-phase motors won’t start on one-phase.) Restore power on all lines
A2: Check starter. Is overload protection   device opened? Replace or reset device. Does it open again when starting?
A3: Is there power on all lines to motor? Repair starter
A4: Is voltage to motor more than 10% below nameplate voltage? Restore proper voltage.
A5: Check motor terminal connections. Are any loose or broken? Repair connections.
A6: May be wrong motor for application. Is starting load too high? Install Design C or Design D motor. Install larger motor.
A7: Is driven machine jammed or overloaded? Remove jam or overload.
A8: Are misalignments, bad bearings or damaged components causing excessive friction in driven machine or power transmission system? Repair or replace component.
A9: Are bad bearings, bent shaft, damaged end bells, rubbing fan or rotor or other problem causing excessive friction in the motor? Repair or replace motor.
A10: Check stator. Are any coils open, shored or grounded? Repair coil or replace motor.
A11: Check commutator. Are any bars or rings broken? Replace rotor.