Earth leakage- troubleshooting 1

[bamia]

Hello everyone,

I was troubleshooting earth leakage VFD error (ABB ACH580) and the manual suggested the following, among other things:

Check there are no power factor correction capacitors or surge absorbers in motor cable

Could you please expand on that, why and how would those two things produce earth leakage fault. (not applicable in my case but just curious)


Thanks

 

[jraef]

Earth leakage measurement on a VFD is a Residual Current Detection summation process of the 3 phases, using Hall Effect transducers on the DC bus feeds to the 6 output transistors. When capacitors are on the OUTPUT side of the VFD, which is actually PWM pulses of DC, the capacitor charging current can be unequal for that brief moment in time, but the hall effect transducers will pick it up and cause a trip. It's not that the capacitors are CAUSING an earth leakage, but the VFD detection circuit cannot tell the difference, so it will ASSUME that's what its happening.