Mike Sherman
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------ Original Message ------
From: Ted Eckert
To: [email protected]
Sent: July 21, 2015 at 1:16 PM
Subject: Re: [PSES] GFCI Nuisance Tripping
Hello Brian,
UL 943 does require testing for conducted immunity. The standard calls out the IEC 61000-4-6 test method. The test level is 0.5 V with a frequency range of 150 kHz - 230 MHz. However, UL 943C states that the immunity tests of 943 are not required to be performed on special purpose GFCIs covered under 943C.
GFCIs typically are fairly simple in design. There is just a simple circuit looking for an imbalance on line and neutral. The standard call out no frequency response and they can have problems with high frequency noise. I had one product that passed the IEC 60950-1 leakage current test with 1.5 mA of leakage current when using the specified human body model circuit. However, if you used a multimeter, you could measure 9 mA due to the high frequency components. This product would regularly trip GFCIs.
The long standing assumption was that GFCIs would only be used for kitchens, bathrooms and garages where moisture may be present. The standards haven't caught up to the concept that your kitchen appliances might have built-in computers with switching power supplies.
Ted Eckert
The opinions expressed are my own an may not reflect those of my employer.
-----Original Message-----
From: Kunde, Brian [mailto:[email protected]]
Sent: Tuesday, July 21, 2015 9:04 AM
To: [email protected]
Subject: [PSES] GFCI Nuisance Tripping
Standard Class A 115V~ GFCI (Ground-Fault Circuit Interrupters) are designed to TRIP at currents around 6mA. I assume this current is accurately detected between DC and some harmonic of 60hz. However, it is common knowledge that GFCIs can false trip or nuisance trip when used with motor speed controllers, lighting dimmer switches, frequency drives, etc. .
I'm not familiar with UL 943C. Does this standard call out specific immunity levels, energy and frequency, that GFCI must properly operate at? Are there published Trip Curves that shows current vs frequency?
Has anyone run across published data showing high frequency trip characteristics of GFCIs?
We have been burned in the past with nuisance tripping GFCIs when products with frequency drives ramp start a motor. We are trying to understand exactly what is causing the GFCI to trip so we can design out the problem in future products. Any insight, recommendations, or suggestions would be most appreciated.
Best regards,
The Other Brian
________________________________
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