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4-4 Troubleshooting
Indication Possible Cause Corrective Action
MIN. Output Frequency
Limit set too high
Adjust setting of Min. Output
Frequency Limit
Motor will
not stop
Improper speed command Verify control is receiving proper
command signals at the control
terminal strip
not stop
rotation
Verify control is set to receive your
type of speed command
Speed potentiometer
failure
Replace potentiometer
Oscillating load Correct the loading problem
Unstable
Unstable input power Correct the input power problem
Unstable
motor speed
Slip compensation set too
high
Adjust slip compensation
Torque boost set too high Adjust torque boost setting
Motor runs
rough at low
Misalignment of
motor/load coupling
Verify and align motor/load
coupling
speeds
Defective motor Replace motor.
Clean the motor air intake and
exhaust areas
Insufficient motor
ventilation
Check external blower for proper
operation
ventilation
Verify motor’s internal fan is
securely coupled to shaft
Check for excessive motor load
External trip
fault
Motor drawing excessive
current
Verify proper motor and control
rating
Adjust V/Hz profile
Volts/Hertz ratio not
Adjust control base frequency
adjusted
Adjust Max. Output Volts
Connect thermostat
No thermostat connected Verify connection of all external trip
circuits used with thermostat
Over current
Accel/Decel rate set too
quickly
Increase Accel/Decel rate
Over current
Torque boost set too high Reduce torque boost setting
Timed
overload
Motor overloaded Verify proper motor and control
rating
overload
fault
Correct the loading problem