Will A VFD Be An Acceptable Way To Power This Lathe

projectnut · Jun 10, 2017

I acquired a Sheldon MW-56-P lathe earlier this year. It has a 2 hp, 220/440 volt, 3 phase motor. I have several other pieces of 3 phase equipment currently running on static converters. When I got the new lathe it came with a 15 hp rotary converter. The original intent was to use it to power the entire shop. However I will need to install another 100 amp sub panel to power the converter, and add several 3 phase circuits.

Given my current work load and outside responsibilities I don't have the time now to install a new sub panel and rewire the shop. I am considering a VFD as a solution to getting the machine up and running. I don't know anything about VFD's. I do know I need to generate 3 phase power, but that's about it. The lathe has a Worthington drive for speed changes so the VFD will not be used for this purpose.

Would a VFD be the proper way to power this lathe, or are there other more appropriate devices that could generate 3 phase? Also if a VFD is the proper choice how should amps it be sized. The motor plate says it will draw 7 amps at full load when wired for 220 volts.

JST · Jun 10, 2017

Something from 10A or so or larger will be suitable.

The VFD will produce 3 phase, yes. You need to get one that accepts single phase input and produces full rated output. They exist. Hitachi, Teco, and Invertek should have them, possibly others.

You need to use the VFD to start and stop the machine, NOT the machine controls.

Monarchist · Jun 10, 2017

projectnut said:
I acquired a Sheldon MW-56-P lathe earlier this year. It has a 2 hp, 220/440 volt, 3 phase motor. I have several other pieces of 3 phase equipment currently running on static converters. When I got the new lathe it came with a 15 hp rotary converter. The original intent was to use it to power the entire shop. However I will need to install another 100 amp sub panel to power the converter, and add several 3 phase circuits.

Given my current work load and outside responsibilities I don't have the time now to install a new sub panel and rewire the shop. I am considering a VFD as a solution to getting the machine up and running. I don't know anything about VFD's. I do know I need to generate 3 phase power, but that's about it. The lathe has a Worthington drive for speed changes so the VFD will not be used for this purpose.

Would a VFD be the proper way to power this lathe, or are there other more appropriate devices that could generate 3 phase? Also if a VFD is the proper choice how should amps it be sized. The motor plate says it will draw 7 amps at full load when wired for 220 volts.

If you do not need variable speed, and do not want to 'give up' the existing on-machine controls in favor of the VFD's front panel, or remoted ones you'd have to wire yourself, it sounds as if you would be stacking one more band-aid atop others.

Might be less total wiring changes to either use that 15 HP RPC, or downsize to a 10 HP - even a 7.5 HP. Then you can go ahead and use MUCH better Rotary Conversion to replace the static converters as well.

Any 3-P switchgear ordinarily is meant to live in separate housings from 1-P, anyway, so as part of the migration of presently static-off-single-phase breakers to the 3-P side of the RPC, you might NOT have to add a new 1-P loadcenter at all.

MIND - some 'guesswork' in there, but I'd not use static converters for anything larger than 3/4 to 1 HP, and a 2 HP lathe motor is a rather light load as well, so.

Could it be that all you really need is a 5 HP RPC idler, or a 5 HP + 5 HP "supplementary" idler?

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Will A VFD Be An Acceptable Way To Power This Lathe

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