WEG CFW500 fault F0074: Ground fault
Ground overcurrent: an overcurrent from an output phase to ground (PE). Like F0070, the protection acts in hardware and cuts the output pulses instantly. WEG notes the fault can be disabled with P0343, but warns that disabling ground-fault protection may damage the inverter and should only be done under WEG’s direction.
Diagnose this with AI
Try Free Drive Diagnostic Upload a keypad photo, the fault history or a parameter export from your WEG CFW500. InduQT compares the evidence and suggests the next useful checks.
When it happens
- At start or while running, when an output phase is shorted to ground
- With long motor cables, from current peaks caused by cable capacitance
Likely causes and checks
1Short circuit to ground in one or more output phases
- Points to it
- Trips at start or when moisture or damage affects the motor or cable; may alternate with F0070.
- Check
- With the motor disconnected from the inverter, insulation-test the motor and motor cable to ground.
2Motor cable capacitance too high
- Points to it
- Long motor cable; insulation tests are good but trips persist.
- Check
- Check the motor cable length and type against the CFW500 user’s manual.
Telling it apart
- F0074 is phase to ground; F0070 is phase to phase or a short on the DC link or braking resistor.
- Good insulation results with a long motor cable point to cable capacitance rather than an insulation fault.
Relevant parameters
| Parameter | Name | Why it matters |
|---|---|---|
| P0343 | Mask for faults and alarms | Bit 0 enables F0074; WEG warns not to disable it except under WEG technical direction. |
Evidence to collect
- Fault history P0050–P0055
- Insulation test results for the motor and cable, with the motor disconnected
- Motor cable length and type
- Setting of P0343
Work on fuel trains, burners, pressure vessels and electrical equipment must be done by qualified personnel following the manufacturer’s documentation and local codes. Never bypass a safety device or interlock.