Step up transformer

Ok, I used the search but didnt find what I was looking for so here it is.

I have a 2hp 3ph mtr in my lathe, I have a 220v 1ph to 220v 3ph VFD(Hitachi X200), but I only have 110v for the small shop. Can I get a step up transformer go from 110v to 220v then connect that to the VFD and then power the lathe???? If so can you enlighten me on this process?

Thanks,
Keith

Greywolf36 said:

Ok, I used the search but didnt find what I was looking for so here it is.

I have a 2hp 3ph mtr in my lathe, I have a 220v 1ph to 220v 3ph VFD(Hitachi X200), but I only have 110v for the small shop. Can I get a step up transformer go from 110v to 220v then connect that to the VFD and then power the lathe???? If so can you enlighten me on this process?

Thanks,
Keith

Click to expand...

Keith, I think there may be a VFD that goes from 110V 2 HP to 220V 3Phase, check the Teco, Hitachi, and Automation websites. Tiny

If you already have the VFD and it requires 240, then you can usually get a suitable transformer from any local Electrical Supplier. The bigger ones carry a range in stock.
The only problem is I would say you would need around a 3kva and that would mean you will need a suitably wired 120v 25amp socket or supply.
If you have to wire this in then you may as well run a 240v pair.
The same current applies even if you get a 120v input VFD.
Minder.

Yes!

The short answer, Keith, is YES.

The long answer, Keith... is YES.

Use an appropriately sized transformer intended for stepping 240 to 120 (usually they'll be 480/240 to 240/120), but connect it backwards. You'll have 240v out.

Just keep in mind that a 120v outlet is only good for either 15 or 20A, so you're limited to about 2hp. As Minder noted, you'll be askin' for everything that circuit has... IF you're running the motor at full-snot load.

Once up and running, you'll either find and learn that limit (breaker tripping), or you'll never get that far, and run away laughing.

Regardless of the 1 phase to 3 phase conversion issue with the VFD, you are still pulling the equivalent amps of a 2HP 115V motor to run that (actually slightly more because of losses in the VFD). 2HP 115V is typically around 18-23A FLC depending on the motor.

On a 115V 15A normal wall outlet of the cheap type used by builders to minimally pass code inspection, you are limited to 15A. That will limit you to 1HP. That is why, by the way, the 115V input VFDs that run 230V motors stop at 1HP.

Wires must be sized to 125% of a motor's FLC and breakers can only be loaded to 80%. So even if you have 12ga wire and a 20A breaker, you can only run 16A on that and that will be well short of the FLC on a 2HP motor.

To run 2HP at 115V you will need a 30A minimum circuit using 10ga wire. I have never seen a 30A 115V circuit as a standard for a commercial building, they are possible, but usually done after-the-fact. So since most likely you will have to have someone add wiring, you should just have them add a 230V single phase circuit.

yes, you can.

You need a "4-way" transformer as mentioned by an earlier poster.

You SHOULD set the VFD current limit to allow only about 0.9 to1 HP. That will avoid nuisance opening of the branch circuit protector.

Your FLA at 2HP will be around 6.8A, so a good current limit for this case would be around 2.8 to 3A. That should keep you from popping breakers, and allow reduced power usage of the lathe.