F0021 fault in WEG CFW500 Drive indicates Undervoltage on the DC Link. This means the internal DC bus voltage has dropped too low, often caused by input power dips or phase loss.
Cause:
- Wrong voltage supply (comply with inverter rating plate and parameter P0296).
- Mains voltage dropped producing a DC Link voltage below the minimum value (monitored in P0004):
- Ud < 200 Vdc in 200-240 Vac (P0296 = 0).
- Ud < 360 Vdc in 380-480 Vac (P0296 = 1).
- Ud < 500 Vdc in 500-600 Vac (P0296 = 2).
- Phase fault on the input.
- Fault in the pre-charge circuit.
Remedy:
Check input mains voltages. Check terminal blocks and check for missing phases. Verify parameters in P0296.
