A customer wants to connect a piece of equipment with a VFD to a GFI circuit. It runs fine on a normal breaker but trips the GFI breaker. (It isn't the motor)
I would recommend replacing the drive if the new drive wouldn't have the same problem. A couple years ago, I wouldn't have thought that CSA/UL equipment would have a ground fault, but now I know better.
It's that their wave forms are electronically perceived by GFCI circuitry as being faulted.
It's inherent in the design of a GFCI's 'balance' circuit that the hot is compared to the return.
VFDs create zany harmonics that rise above the threshold of instantaneous imbalance -- triggering a 'trip.'
Hence, one must install an Equipment Utillization Receptacle rated at a higher threshold.
"In the case of Heat Trace Cables, instead of using the Class A, 6ma Trip Threshold GFCI Devices for controlling excessive "Leakage", Ground Fault Protection for Equipment ("GFPE") Devices are used. The standard Trip Threshold for these GFPE Devices = 30ma (0.03A)."
Per Scott ^^^^ down at the end of the GFI Tripping thread.
Why is the circuit GF protected? Is it protected by a class A device whick trips at 6ma or a GFI at 30 ma as Tesla outlined? There are a lot of exceptions for specific equipment from GF protection because motors often trip GFCI devices. For example a domestic sump pump is located outdoors and the receptacle is in a location that would normally require GFCI protection. We have a rule in the Canadian code book that allows the pump to not be GFI protected as the pumps work is critical. Just need to use a single receptacle and in use cover with a lock to prevent casual use of the outlet. I would expect this is generally true for the NEC too?