Can QO and HOM GFI breakers work on high frequency systems?
Issue:
Will QO-GFI and HOM-GFI breakers work on a load that generates a high frequency (such as a VFD), or will the high frequently cause the GFI to nuisance trip?
Product Line:
Circuit Breakers
Resolution:
QO-GFI and HOM-GFI circuit breakers are rated to be used on 60 Hz systems only, and are designed to trip when a 60 Hz ground fault current between 4 mA and 6 mA is detected.
Even when used on 60 Hz systems, some types of loads (e.g. VFD) can generate a high frequency ground fault current. That high frequency ground fault current can be additive and may increase the sensitivity of the GFI breaker, causing the GFI breaker to nuisance trip as a result of the high frequency ground fault current being present. To reduce the effect of the high frequency, in 1999 a "high frequency roll off" circuit was added to GFI breakers. GFI breakers with the roll off circuit are less likely to nuisance trip when there is high frequency.
If you have pre-1999 GFI breakers feeding loads that generate high frequency ground fault current, and those breakers are nuisance tripping, consider replacing them with newer GFI breakers (which have the high frequency roll off circuit).
Will QO-GFI and HOM-GFI breakers work on a load that generates a high frequency (such as a VFD), or will the high frequently cause the GFI to nuisance trip?
Product Line:
Circuit Breakers
Resolution:
QO-GFI and HOM-GFI circuit breakers are rated to be used on 60 Hz systems only, and are designed to trip when a 60 Hz ground fault current between 4 mA and 6 mA is detected.
Even when used on 60 Hz systems, some types of loads (e.g. VFD) can generate a high frequency ground fault current. That high frequency ground fault current can be additive and may increase the sensitivity of the GFI breaker, causing the GFI breaker to nuisance trip as a result of the high frequency ground fault current being present. To reduce the effect of the high frequency, in 1999 a "high frequency roll off" circuit was added to GFI breakers. GFI breakers with the roll off circuit are less likely to nuisance trip when there is high frequency.
If you have pre-1999 GFI breakers feeding loads that generate high frequency ground fault current, and those breakers are nuisance tripping, consider replacing them with newer GFI breakers (which have the high frequency roll off circuit).
Released for: Schneider Electric Canada
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