fractional hp motor wire repair

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whateg0
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fractional hp motor wire repair

Post by whateg0 »

I have an old single phase, probably 1/3 hp, motor that seems fine, except that the insulation on the wiring inside the motor is in poor shape. I know I may fix this and find that there are other things wrong with it, and I already have probably a dozen other motors of various sizes in both single and three phase. But, I want to see if I can get this one running. I've searched and searched, and maybe I did a poor job of searching, but I can't seem to find much information on what wiring or ratings are suitable for use inside a motor. I am tempted to use some general purpose stranded wire, but I know that temps inside motors can get pretty high. Thoughts/advice?
motorwire.jpg
Dave
Magicniner
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Re: fractional hp motor wire repair

Post by Magicniner »

Research temperatures and specifications?
I just buy good quality new motors, nearly everything I have is 3 phase with a VFD.
I do make good money with my shop time though, so it matters to me how much of it I spend on inconsequentials.
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SteveHGraham
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Re: fractional hp motor wire repair

Post by SteveHGraham »

http://totalwinding.com/magnet-wire.html

Maybe you can measure the gauge with a micrometer and order something identical. Ebay also sells this stuff.
Every hard-fried egg began life sunny-side up.
John Hasler
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Re: fractional hp motor wire repair

Post by John Hasler »

Use 105C rated THHN or THWN of the same gauge as what you are replacing.
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SteveHGraham
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Re: fractional hp motor wire repair

Post by SteveHGraham »

I think I misunderstood. I thought you wanted to rewire the rotor. If you're looking for plain old insulated wire, Teflon insulation resists very high heat. You can solder the wire very close to the insulation without melting or burning it. I'm sure you don't need that level of protection, though.
Every hard-fried egg began life sunny-side up.
John Hasler
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Re: fractional hp motor wire repair

Post by John Hasler »

Teflon can stand a lot of heat but it has inferior resistance to abrasion and cold flow.

MTW (machine tool wire) is also a possibility if you can get it in small quantites. True MTW (i.e., not multirated THHN/THWN/MTW) is a bit more flexible for installation into tight spaces such as the interior of a motor.
whateg0
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Re: fractional hp motor wire repair

Post by whateg0 »

Thanks John! That's what I was looking for. I'll look for MTW as there are some tight bends the wire has to make to get around from where the switch is to where it connects to the capacitor.
whateg0
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Re: fractional hp motor wire repair

Post by whateg0 »

Steve, almost all of the search results I found were IRT rewinding the motor. But, I couldn't find anything on the rest of it. Thanks, though.
spro
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Re: fractional hp motor wire repair

Post by spro »

This is good and very important because you can't find, well you can find old ones. Older ones are drying up. There are particular motors which they will never make again but they had the torque and guts to work a long time. Back to basics, like it or not, heavy stuff with kinetic energy, flattened the pulses.
This is all old news but... Certain motors are the ones for vertical heads because the drive shaft ..because it is short but the bearing retainer fits inside the case. It presents a longer shaft to the bull pulley. Heavy old stuff which did work.
spro
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Re: fractional hp motor wire repair

Post by spro »

I believe that I'm needing to go away. All of this has been said before. Many heads now driven differently. That is fine but the original mass of weight was calculated.
Howard Gorin
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Re: fractional hp motor wire repair

Post by Howard Gorin »

Many older machine tool are wired with rubber insulated wire, there is a cotton braid protecting the rubber.
Oil and heat are the enemies of rubber.
I am presently overhauling a Do-All band saw, circa 1942.
Both the saw wiring and the motor leads were crumbling
Replacing motor lead wires is not expensive.
If you use Teflon insulated wire, protect the Teflon insulation with fiberglass sleeving.
The motor shop I use will do an insulation test first.
If the motor insulation checks out OK, the shop replaces the leads, dips and bakes the stator for about $60.00-$80.00.
The varnish is important!
The varnish keeps the windings from being moved slightly by the magnetic field they generate.
Without the varnish the windings can rub and wear through the very thin enamel that insulates the winding wire
This is for a repair, not a rewind
SteveM
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Re: fractional hp motor wire repair

Post by SteveM »

Howard Gorin wrote: Mon Dec 10, 2018 9:15 pm The varnish is important!
The varnish keeps the windings from being moved slightly by the magnetic field they generate.
Without the varnish the windings can rub and wear through the very thin enamel that insulates the winding wire
This is for a repair, not a rewind
Learned something new today.

Forgot two things, though.

Steve
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