AFCI and GFCI problems installing high-current consumer equipment

[Treadmark]

I am a designer of consumer equipment and have a question on the proliferation of these new circuit breakers. Our equipment uses high current, 12-17Amps at 115v, that is a pulsed load from an AC motor and drive. Peak currents can be as high as 30A. The equipment has been tested and certified by UL for these ratings and we require a 20A dedicated line. However, lately when connected to a dedicated circuit protected by AFCI or GFCI that we are encountering mostly in households, we trip the protection device. Again, we pass the latest UL standards and even CE's (Europe) more comprehensive standards.

NEC is requiring AFCI in all habitable rooms of a domicile. I'm wondering how other high current, especially high starting current, equipment such as air conditions live on these types of circuits? Or have I just not heard the fallout?

 

[ELA]

There are lots of threads here on AFCI issues tripping on various loads such as vacuum cleaners.

Since the AFCI also incorporates a leakage detector you might try some testing to determine if it is leakage (as implied by the fact that the machine trips a GFCI) or if it is that the current pulses "look" too much like an arc signature.

If you can rule out leakage then it might also be EMI causing the breakers to trip. I have also experienced GFCI trips when a servo drive decelerates (during regeneration). Early versions of GFCI's did not address the need for EMI filtering as well a newer versions.

I heard you say that you meet CE standards. This implies you are below are certain level of conducted EMI. It might not be low enough to prevent nuisance tripping of the GFCI. You might try additional EMI filtering between the device and the breaker as a test (as long as you do not introduce too much additional leakage due to the filter itself).

Have you collected any data . Measured leakage currents, current pulse waveforms etc. ? It would be nice if you could monitor the hot and neutral (differential) currents with a clamp on current probe that has an output to a scope.

 

[iwire]

Since the AFCI also incorporates a leakage detector you might try some testing to determine if it is leakage (as implied by the fact that the machine trips a GFCI)

That seems like the place to look as a GFCI should not be tripping on 'arc like' signatures. :smile:

Also GFCI usually work fine with high inrush loads like motors, we use GFCIs all the time on construction sites where items like Chop saws have running currents of 15 to 20 amps and inrush current as high as the extension cords will pass.

 

[winnie]

You might also look at _capacitive_ coupling from your 'AC motor and drive'.

If you are actually using a VSD on this thing, then you will have a high frequency capacitive current, alternately charging and discharging the motor winding capacitance. This capacitive current could trip a GFCI if large enough.

-Jon

 

[acrwc10]

This may sound like a simple question but have you just plugged you equipment into a GFI outlet in the shop to see how it reacts ? Or gotten a AFCI circuit to test it on to see what brand AFCI's are tripping, if it is not all manufacturers. If it was me I would set up a test bench with different brand 2 circuit load centers and AFCI / GFCI protection to test different ones trip. Some brands of AFCI's will not trip, when others will.