Re: Serpentine > Motor conversion


Hello Louis,

I just wanted to say thank you for taking the time to share your experience and thoughts on the VFD's and
what you've used. Your information really helped me out, and I'll put it to good use.

I do have a subsequent question - if I would go variable speed with a VFD, would I need to use the original
drive motor assembly/drive cone.?. or is that just a matter of preference?


On Saturday, September 19, 2020, 03:35:17 PM EDT, Louis via <l_schoolkate@...> wrote:


Based on my experience with repowering machines over the past 20 years and having half a dozen machines here running vfd's, here's my thoughts.

If you want or need variable speed, a VFD is the way to go. I've tried a treadmill motor once and wasn't happy. A vfd (especially the newer sensorless vector types) works much better. The controls are more flexible and they adapt well to a wide variety of 3 ph motors. I've run everything from a new VFD rated 2Hp motor to an antique motor made around 1900 (with cotton insulated wiring) with no issues.

It's very easy to run the low voltage VFD control wiring. Much easier than 12v IMHO. Just make sure to use shielded wire.

For a mill, a vfd rated to match the motor HP works fine with no issues. For a lathe, especially a larger one with bigger chucks, it's probably a good idea to get a vfd rated higher. Otherwise a large chuck slowing down will likely throw an error code. The OP mentioned using a braking resister but I haven't taken that path so far. 

For a 3 Ph motor rated at 1HP or lower, a VFD rated for 110v 1ph input, 220v 3 Ph output will work fine. I have a small mill and a shaper running that way with no issues. For motors over 1 Hp you need 220v so you can run an appropriately sized 220v 1 ph input 3Ph output VFD.

If you don't need variable speed, your typical small 1 Ph induction motors work fine for most machine tools provided you have something in place that gives you the correct speeds for what you want to do. I have several 1 Ph motors from 1/2 to 2 Hp that have been running for a long time with no issues. I have burned single phase motors out a couple of times but they were very well used!

I you install a VFD, make sure it's well clear of chips. All it takes is a tiny piece of metal to short it all out. Mine are mostly installed inside vented, grounded dedicated boxes.  

As for VFD brands, I standardized on Teco quite some time back. Other than one failure almost right out of the box that was replaced on warranty, no issues so far. I buy mine from either Dealers Industrial up in New Jersey or FactoryMation in Georgia. They seem to have decent prices and I've had good service from both with no issues.

That's about all I can think of.



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