VFD as 3Ph shop supply

Wiring length.

You can damage the drive by switching big motors on it, and also, long wiring may create huge voltage spikes and damage your motors and general insulation.

You can somewhat mitigate the effect of wiring length, any VFD manual talks about this. Basically you would need to set up an inductor.

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manual

Yeah... some vendors call them "surge arrestors", but that's not quite accurate. I understand how to do that. It wouldn't even be much of a stretch to install "soft start" features on any motor that started with no load.

The "long wiring" in my shop would be a maximum of 25', if I centralized the VFD.

LLoyd

All of what Iggy said, plus larger VFDs often won't accept single phase power input, and smaller VFDs are pretty reasonably priced these days and I'm pretty sure using individual VFDs will cost less that buying one monster single phase input capable VFD.

And it will be much more convenient.

I have very reasonably priced VFDs 3-5 HP nameplate rating for sale. They work with single phase with some derating

Can you get VFDs that large that also accept single-phase input?

Assuming that you can, I think you can switch motors in and out so long as there is at least one large motor always connected and spinning. In other words, the large motor acts as a rotary phase converter and buffer, absorbing the surges caused by motor switching. The real test is when someone plug reverses a big machine somewhere. The large motor must be big enough to absorb this.

Put the large motor near the VFD, and feed the rest of the shop from the motor terminals, so the wiring beyond the motor isn't really sensed by the VFD.

Joe Gwinn

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Links? LS

Here the 5 HP model. I also have 3 HP.

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Ok... that's nice, but I can't seem to find the ebay listing, and don't know your "store" name, if you have one.

LLoyd

Sure, some Yaskawa models that will run on single phase are available up to 30 or 40HP. I installed 2 10HP Emerson drives last week on single phase input. 240V drives from that series go up to 30HP.

I don't see the point. You're using a significant fraction of the VFD's capacity to run a motor that could serve the same function running as a simple RPC. In other words, the VFD isn't doing anything useful.

I do not currently have them on ebay.

Polyspede turns out a series that goes up to 30HP rated 3ph output from single phase input. I have the 15HP model.

Yes, same type I bought. The one I installed on my Bridgeport is performing well.

Well, the length is the sum total of the length of all wires. So if you have five circuits, each is 20 ft, then your length is 100 ft. The issue is cable capacitance. More cable, more capacitance.

Delightful. I have a bunch of people who put them on mills.

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So, you tune it with the appropriate series inductor. That part isn't a tough one to overcome. Of course, one could also run separate wires at suitable spacing. Twisting wouldn't have much effect at 60Hz.

LLoyd

Iggy I don't have any experience with VFD's. I run a rotary converter on my cold saw and grinding table. I have several other applications that I could use a VFD on. A bandsaw and drill press and Atlas lathe are a few. How quickly can the speed be changed? Do you program the speeds you want and just push a key or two when you need a different speed? Steve

You can, and they will cost you big bucks. About $1,000 for 10 HP.

Whether you can get a 3 phase rated high HP VFD, and coax it into taking single phase input, is a very big question. I will soon work on it.

This depends on their relative sizes, I think that Lloyd wants to have only one motor operating at any given time.

You can connect a potentiometer to one, and on/off switch, and use that for switching and speed changing.