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54067323 (banned)
join:2012-09-25
Tuscaloosa, AL

1 edit

54067323 (banned) to lutful

Member

to lutful

Re: The GFI for the refrigerator tripped

said by lutful:

Here is a relevant discussion from Mike Holt's forum: »forums.mikeholt.com/show ··· ?t=92263

Revelant is comparing a "Our company makes a commercial/industrial bench top polisher/grinder which uses a water supply, so our customers want to use a GFCI. It runs on 115VAC single phase which powers a motor speed controller (frequency drive), which drives a 1hp 3 phase 230VAC motor. When the motor runs, the GFCI will trip almost instantly." to a residential refrigerator?

You have to be kidding.

shdesigns
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shdesigns

Premium Member

said by 54067323:

Revelant is comparing a "Our company makes a commercial/industrial bench top polisher/grinder which uses a water supply, so our customers want to use a GFCI. It runs on 115VAC single phase which powers a motor speed controller (frequency drive), which drives a 1hp 3 phase 230VAC motor. When the motor runs, the GFCI will trip almost instantly." to a residential refrigerator?

You have to be kidding.

My VFD running the 220V 3-phase motor on my lathe will trip the GFCI instantly.

It says why in the VFD manual. I used a generic motor. The manual states a non VFD-certified motor will have too much capacitance for the high-frequency pulses generated by the VFD and cause leakage currents.

Even with a VFD-rated motor it may need a reactor to reduce the stray currents.

BTW, my VFD runs at 8khz PWM.

This has nothing to do with a fridge

Sounds like this polisher/grinder took some shortcuts.
lutful
... of ideas
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join:2005-06-16
Ottawa, ON

2 edits

lutful

Premium Member

said by shdesigns:

This has nothing to do with a fridge

The UK IET link I posted earlier has the title "Fridge Freezer tripping RCD" ... residual current device being the proper term for GFCI/GFI.
»www.theiet.org/forums/fo ··· id=34284

*** another relevant link: »www.google.com/patents/US8011198
A/C compressor, not fridge, but address transient leakage tripping GFCI. Effects of the Invention Even if the motor is immersed in the lubricating oil, the leakage current is reduced, and the occurrence of a trouble such that the earth leakage breaker malfunctions is suppressed.
said by shdesigns:

Sounds like this polisher/grinder took some shortcuts.

The "relevant" issue highlighted in those links is the inability of typical GFCI to distinguish between steady 60Hz leakage current (dangerous to humans) and transient higher frequency leakage current (usually not dangerous to humans, but may trip GFCI).

The polisher/grinder guy actually measured the steady leakage current (2mA) and correctly assumed GFCI was tripping because of high frequency noise. He probably did not have the equipment to measure transient leakage current.

I have measured quite a few fridges, old and new, compressor on and off, on dry vs humid days. Typical GFCI trips between 4mA-6mA while the transients peak between 5mA-10mA. It is not a good match.

Since Leviton (and probably other companies) have started selling newer design GFCI which are less sensitive to transient leakage current, there is no reason to stay with older design GFCI for fridge, microwave and other troublesome appliances.
54067323 (banned)
join:2012-09-25
Tuscaloosa, AL

54067323 (banned)

Member

said by lutful:

*** another relevant link: »www.google.com/patents/US8011198

Which still has nothing to do with the compressor in a residential refrigerator.