Motor rewinding question

Hello, machinefolk,

One of my friends has a bit of a problem, and I thought I'd ask here to try to help him out.

He's rebuilding a small machine, of 1940's vintage, on which the motor is wound for 440V only, 3 phase,
of course. It is a a little one, 3/4 hp., and appears to be generally the common or garden variety GE product of its time, except that the stator housing is a special for that particular machine.

Using a transformer to run it on 440 is not a realistic option, as the insulation in the windings looks a bit cracked and perished.

Our local electric motor electric shop, which did rewinding on small motors like this one, shut down a few years ago, when the owner retired. The remaining motor shops in this area say they do large motors only, and so won't rewind this little one.

Does anyone here know of a reliable motor shop.......(anywhere in conus, that stator would be cheap to ship UPS)..... that would take on the job of rewinding a 3/4 hp. motor, and make a proper job of it?

cheers

Carla

I send all my motors to this place,
http://www.johnsonelectricinc.com

Carla,

I'm in Eureka and these folks are down the road, in Arcata. I've dealt with them for over 30 years, they know their motors and are very fair.

They don't have a website but I'll include a phone number. Ask for the motor shop. (707) 822-2485 Industrial Electric Arcata, INC

Stuart

"West Coast, USA" covers a lot of territory, Carla. I use Reed Electric in Portland, Oregon, but there must be another five or six capable shops in town.

Good to hear from you Carla.

If the insulation appears iffy, I would see if a bake out, dunk in varnish*, and rebake would fix things, and enable the use on the intended 440.

* "Dunk" meaning in a pressure tank, a proper insulating job, where you pull a vacuum first, then apply pressure.

A couple of members here have done it using a standard spray painting tank.

Near 99% probability you can rewire for 220, but insulation might not survive pulling on the coils to locate the correct wires to cut

digger doug said:

Good to hear from you Carla.

If the insulation appears iffy, I would see if a bake out, dunk in varnish*, and rebake would fix things, and enable the use on the intended 440.

* "Dunk" meaning in a pressure tank, a proper insulating job, where you pull a vacuum first, then apply pressure.

A couple of members here have done it using a standard spray painting tank.

Click to expand...

The proper term is vacuum pressure impregnation, VPI. I am set up to do it and have the proper insulating varnish. If you pay for shipping the stator, keep the end bells and rotor, I will do it and do a megger check afterward as a mitzvah for a long time member.

The normal procedure is to bake it somewhere over 212 degrees and put in a vacuum chamber for a few hours. After that, there ain't no --ing moisture in the windings. Then you let in varnish to cover the coils and admit air. For tightly wound transformers extra pressure is good but with random wound coils like motor fields, atmospheric pressure is enough. The varnish will penetrate to every crevice. Then a bake at 265F or so for an hour or two and you have totally sealed windings.

Bill

9100 said:

The proper term is vacuum pressure impregnation, VPI. I am set up to do it and have the proper insulating varnish. If you pay for shipping the stator, keep the end bells and rotor, I will do it and do a megger check afterward as a mitzvah for a long time member.

The normal procedure is to bake it somewhere over 212 degrees and put in a vacuum chamber for a few hours. After that, there ain't no --ing moisture in the windings. Then you let in varnish to cover the coils and admit air. For tightly wound transformers extra pressure is good but with random wound coils like motor fields, atmospheric pressure is enough. The varnish will penetrate to every crevice. Then a bake at 265F or so for an hour or two and you have totally sealed windings.

Bill

Click to expand...

It IS ?

Gollee sarge,........

FWIW I started by composing the 2nd paragraph with the PROPER term of "VPI"
But didn't think a LAWYER would be GRADING my posting, nor did I want to
scare Carla away from something she is probably capable of doing IN HOUSE.