step up transformer and rotary phase convertor.

Larry on Lake Superior · May 6, 2020

Shop has 220V 3 phase supplied by rotary phase convertor.
Lathe has 3hp 2 speed 440V ONLY! 3 phase motor.
Is the lathe likely to work ok when fed by a 3 phase step up transformer?
Maybe simplifying control circuits and going to a 220V motor is more practical.
Lathe is in a large well equipped hobby shop and would never run unattended.
The lathe is a P & W Model C with 18 geared speeds. 36 speeds is an unneeded luxury.

Thank you for your input.
Larry

SomeoneSomewhere · May 7, 2020

It should work fine if the transformer is adequately sized, including keeping both speeds.

thermite · May 7, 2020

Larry on Lake Superior said:
Shop has 220V 3 phase supplied by rotary phase convertor.
Lathe has 3hp 2 speed 440V ONLY! 3 phase motor.
Is the lathe likely to work ok when fed by a 3 phase step up transformer?
Maybe simplifying control circuits and going to a 220V motor is more practical.
Lathe is in a large well equipped hobby shop and would never run unattended.
The lathe is a P & W Model C with 18 geared speeds. 36 speeds is an unneeded luxury.

Thank you for your input.
Larry

Transformer need not be a problem. I'd suggest a 5 KVA, 6.6 or even a 7.5 KVA.

A "little" overkill vs "the math" is good. Twice the motor HP as KVA insures no "choking" of the power under sudden heavy load and lower heat-rise at the transformer under steady load but .. sanity check..

Part of that is actually about what is common, hence easier to find fast, and hopefully at a better price.

Sometimes that includes "free shipping".. as had me buy a couple of mine clear from West coast suppliers to Virginia.

motion guru · May 10, 2020

Yes, 230 single phase -> phase converter -> 230:440 transformer -> lathe is no problem. If the transformer has adjustable taps, you can use these to help balance the voltage across phases. When I started out in my garage 25 years ago, this is how I tested a lot of the systems I built for customers. I had a contactor between the phase converter and the transformer so that the phase converter could start and get up to speed before energizing the transformer. Worked well for powering up all kinds of 3 phase equipment.

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step up transformer and rotary phase convertor.

Larry on Lake Superior

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thermite

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