AFCIs, MOVs, and Variable Speed Motors

Wild guess: the MOV clamps when accelerating and the clamping action shapes the current waveform to fool the ACFI to think it is a high frequency arc?

Clamped sine has overtones...

Or the ACFI is sensitive

Cheers

Klaus

I think so too.

does the outlet strip have movs connected to the saftey ground pin?

may be an accumulation of leakage to ground and the ground fault portion of the acfi is tripping.

I'll look into it, but as I understand it the AFCI is not looking for a GND fault, it's looking for something like a line to neutral discharge similar to an arc through defective insulation.

or maybe the MOVs have nothing to do with it, simply the added length of wire changing a resonance.

I believe AFCIs are required to have ground fault detection at 50mA or less. It is typically 30mA. The idea is that an arc with a ground present may damage insulation and also involve a ground fault.

One of the manufacturers had UL test whether a "glowing connection" would cause a ground fault on a grounded receptacle. A "glowing connection" is a loose connection at the screw that produces a lot of heat, but is not (at that point) an arc. From memory, 25% or more caused deterioration that caused a ground fault trip.

The early AFCIs only detected at a current level that would see a "parallel" fault - line to neutral or ground. After about a year they would detect at a level (5 A?} that would detect a "series" arc (loose connection).