Chapter 8 - Troubleshooting & Maintenance
8-2
8.2 Fault Remedy
Function
Cause Remedy
Over Current 2 Short circuit between the upper and lower IGBTs.
Short has occurred in motor circuit or windings.
Acceleration/Deceleration time is too short.
Check IGBT with multimeter in diode check mode.
Check motor wiring and windings. Set SET-06 to
0.7kHz and if VFD does not trip or it takes
longer to trip, the motor winding has insulation
problems. Install output reactor.
Increase acceleration time.
Over Current
Protection 1
Accel/Decel time is too short for high inertia load.
VFD is undersized for the motor rating.
Output short or ground fault has occurred.
Mechanical motor brake is not controlled properly.
The VFD is overheated.
Increase Accel/Decel time.
Upsize VFD.
Check motor wiring and windings.
Check mechanical brake operation timing.
Check VFD temperature and cooling fans.
*Caution: Frequent VFD starting with this fault
may damage the VFD power components.
Overload
Protection
The VFD and motor are undersized for application.
Incorrect VFD capacity is selected.
Incorrect V/F pattern.
Increase VFD and motor size.
Select correct VFD capacity.
Select correct V/F pattern.
(ETH)
Electronic
Thermal Motor
Overload
ETH level setting is too low.
Accel time is too low.
Motor is overloaded.
Motor is undersized for this load.
Incorrect HP rating is selected.
The control is set to incorrect V/F pattern.
Motor operates at too low speed too long.
Set ETH to a proper level.
Increase Accel time.
Reduce motor load and/or run duty cycle.
Increase motor size.
Select correct HP rating.
Select correct V/F pattern.
Set VFD frequency limit to 20-30Hz.
Ground Fault
Protection
Ground fault has occurred in the motor circuit. Check output wiring and insulation of motor
windings with Megger tester.
*Caution: Disconnect motor leads from VFD
before performing Megger test.
Over Voltage
Protection
Deceleration time is too short.
Mechanically unbalanced load.
Regenerative power from motor during Decel.
Line voltage is too high.
Increase deceleration time.
Check DC bus voltage, change V/F curve, or use
Dynamic Braking Unit and Resistor.
Check line voltage and call utility company.
Low Voltage
Protection
Line voltage low.
Load larger than line capacity is connected to line.
(welding machine, motor with high starting current
connected to the commercial line)
Faulty magnetic switch at the input side of VFD
Check line voltage.
Increase line capacity.
Exchange magnetic switch (contactor).
VFD Overheat Cooling fan malfunction.
Enclosure cooling fan filter is dirty.
Ambient temperature is too high.
Replace cooling fan(s).
Clean or replace enclosure cooling fan filter
Upsize VFD for higher temperature rating.
Output Phase
Open
Faulty contact of magnetic switch at output
Faulty output wiring
Check magnetic switch (contactor) at VFD output.
Check output wiring.
External Trip Digital input set for External Trip is activated Eliminate trip condition at circuit connected to
external trip terminal or remove external trip input.
H/W Fault W-Dog error (CPU fault)
EEP error (memory fault)
ADC Offset (current feedback circuit fault)
Exchange VFD.
Com./CPU
Error
Faulty connection between VFD and keypad.
Control board malfunction.
Keypad is bad
Check connector.
Replace control board
Replace keypad.
Frequency
Reference is
Lost
LOP (Loss of reference from the Option),
LOR (Remote)
LOV (V1),
LOI (I),
LOX (Sub-V2, ENC)
Eliminate the reference signal loss problem.
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