Convert Lathe Motor to 3-Phase?

@Gaffer I've done 2 VFD conversions for lathes (for me) and advised on many more.

Short answer: Yes you can, and you might love it.

The Baldor motor is just under 1 HP real power. Because of its use, it is intended for 'soft start' which a VFD provides. Because of the weight of the chuck and drive train I *usually* advise going to the next higher increment in horsepower to minimize strain on the motor when starting up the chuck/drive train.

This motor is *intended* to start under load, but dropping down to 1HP will be noticeable. Since your motor/VFD is likely to cost you around 100$, your risk is minimal. You will gain a lot of advantages using a VFD on a lathe, so give it a try.

I would first wire the new motor/VFD completely separate from the lathe, install it, and then see if it meets expectations. I did a LOT of work on a 1/2 HP South Bend lathe in my time so if you are OK going slow, then you will love it.
 
Another thing to consider is the frame size. Your existing motor is a NEMA 184 frame. The three phase motor you're looking at is a NEMA 145T. Google electric motor NEMA frame dimensions so you can compare to make sure you can adapt the new motor to your existing space.

Ted
 
Gaffer said:
I found on CL a Baldor 3-phase for $75 (said to be in excellent condition), and am now considering buying it and adding a VFD. I know just enough about this to make a bad decision and get into trouble. Both motors have the same size shaft, RPM, and HP. Is this a bad idea? Note the difference in HP - is this an issue? Here are the photos of the ID plates.
Click to expand...

As has been noted, that motor you're looking at is for a very specialized application. The "special" rating in the horsepower box means somebody ordered custom spec motors to bolt on to some appliance that's gonna be rated by the advertising department, not NEMA or anybody like that. Like the five horsepower compressors you buy at the box store that have a standard 120 volt, 15 amp plug that would fit in your living room outlet.....

I don't think it's "that" bad, but it is definitely a very significantly smaller "actual" horsepower than what you've got. It's also going for (at least around here), a lot less than any good condition, loose Baldor motor goes for.

And then there's the speed control idea. You're going to want an overrated motor for that, if you're going to slow it down any. This would be a double loss. Ouch.

Personally, I'd investigate what's going on with the existing motor. If "fixing the electrical" isn't in your wheelhouse, let me suggest that starting over from scratch is gonna be the same job, but in multiple places, and lots more of it... The original motor will be a good one, and well suited, assuming it is or can be easily made fully functional. That's my vote here. Or hold out for a more "lego" motor that's designed to national standards, so your add ons can work with it more transparently.
 
Jake M said:
As has been noted, that motor you're looking at is for a very specialized application. The "special" rating in the horsepower box means somebody ordered custom spec motors to bolt on to some appliance that's gonna be rated by the advertising department, not NEMA or anybody like that. Like the five horsepower compressors you buy at the box store that have a standard 120 volt, 15 amp plug that would fit in your living room outlet.....

I don't think it's "that" bad, but it is definitely a very significantly smaller "actual" horsepower than what you've got. It's also going for (at least around here), a lot less than any good condition, loose Baldor motor goes for.

And then there's the speed control idea. You're going to want an overrated motor for that, if you're going to slow it down any. This would be a double loss. Ouch.

Personally, I'd investigate what's going on with the existing motor. If "fixing the electrical" isn't in your wheelhouse, let me suggest that starting over from scratch is gonna be the same job, but in multiple places, and lots more of it... The original motor will be a good one, and well suited, assuming it is or can be easily made fully functional. That's my vote here. Or hold out for a more "lego" motor that's designed to national standards, so your add ons can work with it more transparently.
Click to expand...
I'm passing on the 3-phase conversion. My motor worked fine, and I just replaced the bearings. When I finish painting it, I'll work out the wiring. @markba633csi has been helpful. Thanks
 
We can pick up the old thread if you want to- I just posted there
-Mark
 
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