Small Electric Motors - Any Hope?

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TomKro

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Spent a little time checking out some old electric motors for a neighbor. I put power to the motors to see if they're any good, but limited success. One just hums, the others spin, but four of the motors show voltage on the cases under power.

ElectricMotrors_resized.jpg

I opened up the junction boxes to look for wiring damage and shorts. Lots of cruddy feed wiring, but I cleaned up the connections with ring terminals. Nothing else obviously bad, but four cases still showing some voltage under power.

Any idea what to check next? Or off to the scrap pile? Any benefit to splitting them open and digging deeper?

Sort of humorous (to me), one of the wiring diagrams indicates "UNGRND". I guess that's the hot leg. I have just enough electric background to be dangerous.

Unground_resize_cropped.jpg


Any guidance is appreciated.

TomKro
 
I think you have pretty much done what you could ex cept the one that just hums. That one could be the start circuit and careful disassembly and cleaning could resolve that. Check the start capacitor as well. That is probably a good one yet.
 
The one that hums is really old. Constructed with some sort of oddball square end mounts, but no saddle to mount it.

I'll probably open that one up purely out of curiosity.

Thanks for the advice.

TomKro
 
Please take and post pictures reguardless of the results.
 
Could be the start capacitors, which are typically in the bulging compartment on the outside.
Note that you should short the terminals before touching these as they can hold a charge if they are any good.
 
The leakage to the case may be acceptable- You should check with an ohmmeter from both the power leads to the case- should measure higher than 1 meg ohm (1 million ohms) to be usable. Of course you would also run a ground wire to the case for any of those, if you were to put them in service
-Mark
 
the best way to learn something about induction motors ,IMO, is to take one apart,
there will be no mystery as to what a motor is made of after that
 
Curiosity got the best of me. Rainy saturday morning in Aberdeen.

Took the cap off the little humming motor. A bit of sawdust in there.

SquareBossMotor_Precleanout_resized.jpg


Cleaned it up as best I could. Used a point file on the contacts and some spray cleaner.

SquareBossMotor_PostCleanout_resized.jpg

Looks as though three wires are creased and some broken insulation. I sprayed a little "liquid tape" into a dish and painted on some insulation. Still no luck. Motor didn't spin up, and I didn't keep the power on it long enough to check the case.

Either the wires are frayed too much inside the insulation or maybe something is shorted in the windings (?). I'm getting close to the limit of my abilities on this one. Not sure if I can solder in new wires without making more of a mess.

Gonna pack it up for now on this motor.

As to the the other motors with hot cases, I'm going to have to acquire a better ohm meter. Don't think I should trust my $10 multi-tester from Radio Shack. Been bouncing around in a tool box for a few decades. When I re-wired the feeds with ring terminals, I left the ground leads extra long. Still a little hope for the four other motors, but fading fast...

Thanks for the help.
TomKro
 
Yep, that motor was pretty sad.

BTW, I don't plan on relying on the painted on insulation for operation. Mainly to find the cause of the hot case.

It gets better. Here's the "good" motor. No sense using electrical tape when duct tape is handy...

PowerCord_GoodMotor_resized.jpg

The motor itself is actually pretty clean. Power cord needs some TLC.

TomKro
 
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