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Rewinding a stator

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dbassing

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Hello,
I have an old Master Gearhead motor that needs to have the stator rewound. It is a repulsion-induction motor 1/2 HP 110V single phase. I am thinking that I could do this myself and so have started down this road to learn how to do a rewinding. I have a good idea of the basics and am thinking that if anyone has experience in doing this sort of thing I would be most appreciative if they would chime in and if possible let me post questions here. I hope to do a thread showing the process. It may be a complete failure but I have nothing to lose and I may learn something in the process.

Thanks,
David
 

mksj

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I have seen other posts of individuals rewinding older motors to preserve the vintage machinery, not an easy task if done correctly and a learning curve. It is time consuming and costly for a one off job, but a learning exercise. Can't find the post which outlined the process, these are two files that I have specific to this topic, one is for motor rewinding supplies, the other gives some basic information on rewinding.
 

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Fabrickator

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In the 80's, I worked in a R&D shop that made unique machines and motors. We had a full time "OG" who did nothing but wind/repair and actually design/build to engineers specs from scratch, any electric motor. He learned electric motors in the Navy in which he served for 25 years before he was hired at this shop. He was a great find, he could ask his own price because you just don't find guys like him anymore. As seems to happen so many times with really talented, nice guys, he died at a rather young age before retirement. I really enjoyed just hanging in his corner of the shop when I had time to watch how it's done.

He would wind his bundles on a special machine that collapses so you can remove them, wrap with insulating paper, carefully pound them in the stator grooves, solder them up, test continuity, dip & bake them. We even made an electric dyno out of a huge load bank so we could test/document them for power and torque output.
 

dbassing

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Well the crashed server explains why some of my and other posts have disappeared. Would those who took the time to respond to this thread repost. It would be good to have a record of the resources that were posted.

If I remember correctly, someone asked if the stator actually did need rewinding. My response is: I initially took the stator into our local motor shop. They tested for continuity which was good and tested to see if the windings had a short to the motor case. All good there. When they used an electrical tool called "growler", which I believe creates a magnetic field, they found one pole of the winding that indicated a problem. My initial reason for taking the stator in was the leads coming from the stator were in bad shape, with cracked and crumbly insulation.

Another post pointed out the possibility of using a 3 phase motor with vfd to run the horizontal mill. I am looking into this as well as rewinding the original motor. There is a cost for both and I will make a decision as to which way to go when I get more info.

Thanks all for your questions and comments,
David
 

mksj

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There is a learning curve to rewinding a motor, and often you have to buy the supplies in bulk form along with the resin. A rough guess on rewinding is probably around $400-500, but will be helpful to see what price quotes you get. One reason why on smaller motors, they are usually a toss as opposed rewinding as a new motor is less expensive if a suitable replacement can be found. What I have also seen on this model with replacement motors, that instead of getting a geared motor reduction, they change the drive pulley ratio to give a similar reduction. I would also check to see if machine reduction gear can be mated to a new motor. Some photos may help.

On using a 1750 RPM motor as a direct replacement, it would need to be a 2Hp and the performance would suffer if running it at 25% of its rated RPM to achieve the slower speed. I would be more inclined to use a 900 or 1200 RPM motor, the two below are possibilities and inexpensive. The posted weights are incorrect. Unfortunately the slower the 60Hz speed motor the heavier they get. A Teco L510 VFD 2Hp would run $170. So you are looking at $300-400 for the Brook Compton or the Baldor 1200 RPM motor with the Teco 2Hp VFD. If you can rebelt the speed down to a 2:1 you will have the best of both worlds, a wider speed range with a bit more on the top end. It would also be worthwhile to see if you can adapt a new motor to the gearbox, that would be the least expensive and time consuming option, the site listed below have motors in the 0.5-1.0Hp range for under $150. There are gear motors, but they are expensive.
http://dealerselectric.com/TA6N1-5-3.asp
http://dealerselectric.com/35U570S391.asp
http://dealerselectric.com/L510-202-H1-N.asp
 

Silverbullet

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#6
Question when the motor was cked did they know it was a repulsion motor . Seems to me I remember something about cking with a growler on those. It was only one step or way they could be cked out with them. I don't know it just keeps telling me , don't get old and take lots of morphine. But a red flag comes up on how to Ck those type out in my memory. DERN I hate that. Anyway you could try spray varnish to insulate the windings then clean the comutator and grooves and Ck again. Been a long time since I did them. We had old equipment and had to rebuild in those days.
 
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