New GFI 110v outlets blow out TECO VFD

Glenn Brooks

Glenn Brooks

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I decided to install three new 110 v outlets at my grinder bench to accommodate my power tools. The county electrical code requires GFI outlets when any upgrades are accomplished, so I installed 3 GFI outlets.

Now my baldor 8” grinder doesn’t work. It is powered with a Teco L510 110 to 220 3 phase VFD. when I push the on button, the VFD powers up the grinder for maybe 2 or 3 seconds, then the gfi circuit trips and the grinder goes dead.

Of course, with the old standard plugs, the VFD and grinder work just fine. But the electrical inspectors won’t sign off on old style plugs, demand GFI’s.

Any one advise me how to fix this? Maybe some parameter in the VFD?

thanks
Glenn
 
I was always told not to use motors on GFI circuits. I am curious to hear the experts replies on this. Do you have to use GFI receptacles or can you use GFI circuit breakers? Would one work better than the other potentially? (by potentially I don't mean electrical potential I mean theoretical potential or hypothetically....oh, never mind.)
Robert
 
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Do you have a good earth ground on the Baldor separate from the one in the power cord? What about the Teco ground? Robert has a good point; maybe the GFI breakers are less sensitive than the outlets
Mark S.
 
GFCI or AFCI? AFCI is required by NEC in almost all new applications. GFCI in some applications. My Grizzly mill wouldn't run on the code required GFCI (unfinished basement) and a call to tech support was not much help.
Somehow some of the power to the drive isn't getting back or, the more likely reason, the drive is creating some interference that trips the GFCI. Ask any ham radio operator about some GFCI or AFCI devices tripping when transmitting. Try some ferrite cores around the power supply cord to the VFD.
 
Mark, the motor and VFD are bonded together thru the pedestal mount, but I do not have the motor or VFD grounded directly. They do ground thru the ground wire in the circuit coming from the main panel. I can certainly run a separate ground wire directly to a grounding rod I installed just for this purpose.

Jim, these are common residential GFCI fixtures. Not sure what an AFCI is...

In googling Teco VFD’S it appears many people say this is an insolvable problem as required GFCI receptacles sense differtial current and automatically assume a ground fault when none actually exists - if I am paraphrasing correctly. So far, the fix seems to be, get the inspection signed off, then replace the da&n things with standard electrical outlets.
 
Replace the 110 with 220 to avoid the GFCI issue completely. I cannot say what you should do after the inspection is signed off but there is mention of using the ferrite rings and to reduce the length of wire to the motor if possible and increase or actually attach the shield ground to remove EFI. Lots of chatter on the web about this and with the codes moving to more GFCI and AFCI is Arc-fault breakers for home use, issues will occur and manufactures have to step up.

https://library.e.abb.com/public/bbe3c864d311f0e88525792000750ed3/LVD-EOTN14U-EN.pdf
 
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Does an AFCI breaker also provide GFI safety?
If you hard wired the Teco VFD ( no receptacle) would the AFCI or GFI be required?
R
 
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Well, I don’t have 3 phase in this area of my shop, so eliminating the VFD isn’t an option for me. Hardwiring the VFD to the 110 circuit IS an option. I’ll have to ask the county inspector if that is permissible under the code. Might be an excellent option.

Thanks
Glenn
 
You cannot use a residential GFI with a VFD, it induces current (leakage) in the neutral wire that will trip them every time. In industrial settings that require a GFI, you can buy a comercial one specific for use with VFDs and they are very expensive. An AFCI is not a GFI, although they do sell combination units, the GFI will still trip. I suggest you call Teco Tech., but I have seen this problem countless times and the only solution is to not have the VFD on a GFI outlet.
https://www.schneider-electric.us/en/faqs/FA274920/
http://www.bender.org/
 
Glenn, you might find that the "leakage" that mksj refers to is caused by an RFI (or EMC) filter that is sometimes installed to limit radio frequency interference from the vfd, rather than leakage from the drive itself. They have a connection to ground, via internal capacitors, which can pass enough current to trip the gfci. I would agree tho' that hard wiring the unit would be the best option, preferably through an industrial type ground fault circuit breaker.
Cheers Tim
 
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