120v vfd for 3 phase

[stinkity stoink]

Quite a bit of discussion, but I can’t seem to find the GFCI outlet I’m looking for.
I upgraded my old drill press to 1.5 horsepower three phase motor. I have it wired for the low-voltage 208 on the three phase motor . I am using a VFD that powers off of a 120 V outlet single phase. Everything works great if I plug it into a non-GFCI outlet. It keeps tripping the GFCI outlet.
I have been trying to read, and they say there are GFCI outlets out that are a different classification that would work, but I can’t seem to find any. Or maybe I am just reading wrong. If anybody has any info on where to get it or what it’s actually called please speak up.
thank you
Dave

 

[matt_i]

GFCI is never going to play well with a VFD setup like that. I had similar issues with a diamond wheel/solid carbide scraping tool grinder I built from a double shafted 3ph 1/4hp motor from a scroll saw. Same type of VFD. Make sure all ground paths are solidly connected to your machine and back thru to the outlet and just live that way. I personally don't think you are in very much danger if you can make solid connections and your wiring is touch-safe to start with.

 

[mm08822]

You want a GFCI recept labeled "HF". Leviton claims their gfci recepts already meet the requirement and website refers to the HF feature.

But, none of their GFCIs that I've purchased recently have the HF marking. Supposedly, Sept. 1, 2026 is when the ac gfci requirement become effective. So I expect these gfci cb's will contain the HF functionality. If that is the case, then I assume the functionality should easily trickle down to 15/20a, 120v gfci recepts.

Here's a thread that discusses the topic: https://www.garagejournal.com/forum...tion-for-you-contractors.557609/post-11630234

 

[stinkity stoink]

GFCI is never going to play well with a VFD setup like that. I had similar issues with a diamond wheel/solid carbide scraping tool grinder I built from a double shafted 3ph 1/4hp motor from a scroll saw. Same type of VFD. Make sure all ground paths are solidly connected to your machine and back thru to the outlet and just live that way. I personally don't think you are in very much danger if you can make solid connections and your wiring is touch-safe to start with.

I was thinking about just living with it ,but I figured if I find one that works I would use it.

 

[stinkity stoink]

You want a GFCI recept labeled "HF". Leviton claims their gfci recepts already meet the requirement and website refers to the HF feature.

But, none of their GFCIs that I've purchased recently have the HF marking. Supposedly, Sept. 1, 2026 is when the ac gfci requirement become effective. So I expect these gfci cb's will contain the HF functionality. If that is the case, then I assume the functionality should easily trickle down to 15/20a, 120v gfci recepts.

Here's a thread that discusses the topic: https://www.garagejournal.com/forum...tion-for-you-contractors.557609/post-11630234

Thats one of the several threads I read. I am all over the place

 

[mm08822]

Thats one of the several threads I read. I am all over the place

Here's a draft to change that timeline that the ac industry is pushing for. I really don't know where the electrical product manufacturer's are with a gfci device that will comply with the UL Supplement B requirements. I would think the first mfr with development completed would be blowing their horn, but I haven't seen anything.....

 

[TurnipTruck]

I thought we talked about this just a couple months ago?

 

[u2slow]

Feeding 120V to a 208v motor is certainly not ideal. A VFD isnt a transformer.

Thankfully a drill press is a type of machine that runs mostly unloaded or lightly loaded. Watch the temperature and dont be surprised if it experiences a shortened life.

I wouldnt run it on a GFCI at all.

 

[LopezBart]

Feeding 120V to a 208v motor is certainly not ideal. A VFD isnt a transformer.

It works because the 120 VAC is converted to high voltage DC using a voltage doubler rectifier circuit ( https://en.wikipedia.org/wiki/Voltage_doubler ) and then used to produce 208 three phase in the usual manner.

This works for loads up to 1 hp; past that, you need 240VAC input....

 

[u3b3rg33k]

Feeding 120V to a 208v motor is certainly not ideal. A VFD isnt a transformer.

Thankfully a drill press is a type of machine that runs mostly unloaded or lightly loaded. Watch the temperature and dont be surprised if it experiences a shortened life.

I wouldnt run it on a GFCI at all.

120V input VFDs typically have voltage doublers. kinda like old computer power supplies had that 120/220v toggle switch. same thing.

fun fact, you can run a 400v class VFD on 200v class power with... a DIY voltage doubler feeding the DC bus! precharge resistor recommended. as always, try not to die.

 

[u2slow]

120V input VFDs typically have voltage doublers. kinda like old computer power supplies had that 120/220v toggle switch. same thing.

Noted.
I havent dabbled much with small VFDs, but the ones I have... must be basic ones. Nominal V-in = nominal V-out.

 

[u3b3rg33k]

Noted.
I havent dabbled much with small VFDs, but the ones I have... must be basic ones. Nominal V-in = nominal V-out.

there's more than a handful of models meant for small motors that take in 120V.

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if we do the math we run out of amps pretty fast on 120V input power.
5.8A*1.73*2=20.068 A
so I assume that's why they stop at 1.5HP. but you can do a lot with 1.5HP

 

[u2slow]

there's more than a handful of models meant for small motors that take in 120V.

Like I said, I havent dabbled with any for 120V input.