3-phase motor

[bdarin]

Got an old Atlas horizontal mill that came with a 220V 3-phase motor. Is it worth getting an electronic phase converter for this thing or should I just chuck it and use a modern motor. The mill only requires 1/3HP to work so I suppose a 110V motor would be fine, but the 3-phase came with the machine. I guess my question is: is the old motor worth the hassle or should I just put on a different motor and get on with it?

[SGW]

The cheapest way out is clearly a used 1/3 hp 120V motor, which you ought to be able to find all over the place. I'd probably try to boost that up to a 1/2 hp, if I could find a used 1/2 hp motor cheap, but that ought to be plenty. I don't see any reason to use the 3-phase motor with a VFD, unless you particularly want the variable-speed feature the VFD would give you. That's undeniably nice, but it's not clear you need it.

Personally, I'd put a new (used) 120V motor on it and see if the belt and pulley arrangement of the mill supplied enough variety of speeds to suit my needs. If not, you can always resurrect the 3-phase motor and get a VFD.

But it's really up to you. I don't think there's a "right" answer. Your preference.

[Thrud]

A newer motor should be more energy efficient and cost you less in the long run - plus it will be smaller in physical size.

Dave

[C. Tate]

It is possible to make a phase converter from an electric motor. I have never done this but my father-in-law was electrical engineer with the power co. and he told me how.

1. Attach 220 single phase to the donor motor just like you normally would leaving one wire attached to nothing.

2. Connect your three leads from the machine motor to the three on the donor motor. You should now have two bundles containing three wires and one bundle containing two wires.

3. Turn on power to the donor motor leaving machine motor off, you will have to pull start the donor since it does not have proper power supply use a piece of rope and pulley to start shaft. A three phase motor will run single phase with no load and will generate the third phase to run your other motor. Use a motor larger than the one on your machine.


I HAVE NOT DONE THIS AND CANNOT GAURANTEE THAT IT WILL WORK OR THAT MY WIRING INSTRUCTIONS ARE CORRECT. CHECK WITH YOUR ELECTRICIAN BEFORE YOU DO THIS.

[SGW]

Yes, that will work pretty well. There's a good description of how to do this, including how to make the "converter" motor self-starting, at http://www.metalwebnews.com/howto/ph-conv/ph-conv.html