3 ph motor options?

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Jason280

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I have a couple of Atlas/Sears lathes, a 3986 and a 101-07403, both with single phase 120v motors. I am considering converting to a 3ph motor, and using a VFD. I've found a potential motor to use, but I honestly don't know that much about 3ph electric motors. This one is a North American Electric, model # PE145T-1.5-4, which is a 1.5hp 1750 rpm (with what looks like the correct footprint/frame size). Any reason this motor wouldn't work for my application? I couldn't quite tell from the ad, but are these actual US manufactured or import electric motors? Aren't all 3ph electric motors reversible?

Thanks!
 
Looking at the specs on the motor, its a 145T frame....which I assume means a 7/8" keyed shaft. I can't remember if the Atlas lathes use a 1/2 or 5/8" shaft or not (I'll have to measure the pulley once I get a chance).
 
Should work fine. Just keep in mind at half speed you have half the power. So, you will have abut .5 hp at 500 rpm with a 1.5 Hp motor. This about the minimum to run a lathe. If you have room, and $, a larger motor will give you more speed range before loosing enough power.

Also, if your 1 phase motor is also 1750 RPM consider a smaller pulley for more torque. You can run that motor up to 3000 to 3600 RPM for a range of 500 to 3600. Don't run the lathe itself at much higher RPM than it was built for.
 
A 5/8" shaft is a lot more convenient- most all Atlas motor pulleys are 5/8"
 
A VFD will handle reversing your 3 phase motor.
Best thing I did when swapping motors was to bore out my pulley to accomodate a taper bushing. Once bored to the right taper, you can just use a different bushing of the same series to accomodate different shaft sizes.
 
Jason280 said:
I couldn't quite tell from the ad, but are these actual US manufactured or import electric motors?
Click to expand...


From the "About Us" page-

Company History​

In 1993, North American Electric began sourcing high quality, high performance electric motors and gearing from around the world and distributed them on a national and international level.

It doesn't look good...
 
Best thing I did when swapping motors was to bore out my pulley
Click to expand...

I thought I *might* have to do this, awaiting confirmation now on the shaft size of the 3 phase.
 
According to a couple of Atlas brochures I have, the standard motor for the later 12" Atlas/Craftsman lathes was 1/2 HP, 1725 RPM, with a 3/4 HP as an option. Most, if not all were 56 frame. Earlier versions used 1/2 HP motors, and the standard motor for the 10" Atlas lathes was 1/3 HP, all 56 frame, and 3 phase versions were also available with the same frame. I have a Model 12700, one of the last Atlas lathes made, and it came with a 1 HP, 1725 RPM 3 phase motor. I'm not sure that it is a true 1 HP, because the amp rating at 230V is only 4.1. The frame size is 56M, and I assume that the M refers to a shroud on the end of the motor opposite the 5/8" shaft. This lathe has the 1/2" thick ways, which makes it more rigid that the earlier versions with 3/8" thick ways.

For ease of conversion, look for a 56 frame, 3 phase motor. Don't feel that you need a larger HP motor. Atlas felt that 3/4 HP was maximum for the 3900-series lathes, so a 1 HP motor is a step up, instead of a leap.

You can adjust belts easily, so don't feel that you have to run the motor real slow. Adjust the belts instead. Remember, there is a back gear, too. 45 cycles per second gives about 1300 RPM, which is 1/3 slower than standard, and 2/3 HP. This is greater than the standard power from Atlas.
 
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