So I Am Testing The Motor

[crokett]

I brought the motor home to test. The motor has 4 leads. Black (hot) White (neutral) and two whites that are each of the coils. It was wired for 220 with the two whites wired together. I tested the hot to neutral, that showed resistance. I rewired for 110 and checked again, that showed resistance. Testing white to white had no resistance but I would expect that. The motor spins with no noises, hesitation, etc.

I cracked the cover and found this:


The brushes look good. I tested each of the wires connecting the brushes as well as testing wire to wire. Since there are brushes there is not a start cap, correct?

I only pulled one end cover off. The covers help align the shaft and I did not want to have to piece it back together. Is there anything I can check on the pulley end?

I don't see anything obviously wrong, is there any reason not to connect power and see what happens? I am thinking maybe since it was wired for 220 the place I got it from was testing it on 110 so that is why they thought it was bad.

[just started]

Dave, it looks like 1 of the brush leads was crimped under the end bell. Check it to make sure there are no damaged wires and then carefully reroute it so that can't happen again. You may be right about them trying it on 120, especially if it had the wrong plug on the wire. I think you are ready to power it up. Good luck.

[Tom Slick]

Brushes = no start cap
nothing to check on pulley end

In your picture the windings in the motor at 9 o'clock (where the leads enter) look black, are they burned? Have you checked any of the leads to ground?

[crokett]

The brush lead looking crimped is the camera angle. But you have me paranoid now so I will recheck that tonight.

Tom, I think that is just the color of the windings but will check again. I didn't smell anything on the motor except for what a 50 year old motor normally smells like. Would I have to pull the entire thing out of the housing to check the leads? I could, I am just nervous about not getting it back in.

When I got it any plug/switch had been cut off - there was just a pair of leads wire nutted to the hot/neutral. I am thinking they tried to test it wired for 220 @ 110 because the guy I got it from didn't seem to know much about much. Not that I'm a genius but he thought I was brilliant in the way I suggested we load it on my trailer.

[cgallery]

It is kinda interesting that the varnish on the windings looks cooked in that area.

Is it possible that they got hot enough to burn the insulation, but not hot enough to open?

Is there more than one set of windings? If yes, then they should all match pretty closely in resistance, no? And if they should match and don't, then something is wrong, right?

That's a lot of if's. I do find this thread fascinating, though.

[eccentrictinkerer]

FWIW, when I've got a suspicious motor or other device, I hook a 120 volt - 100 watt light bulb in series with the device.

The bulb acts as a current limiter and prevents a short to the breaker.

If the bulb lights full on the device may be shorted (it could also be a very high current device). The bulb should allow enough current to flow safely to get all but the largest motors at least turning slow.

[crokett]

I will try the lightbulb idea, that is a good one. At this point the motor is either busted or not and if it is, whatever testing I do to it it won't hurt it.

[crokett]

Well that was a non-event. I wired the motor for 110, plugged it in aaand....
nothing. Looks like it will get repaired or replaced.

I did notice last night that one coil had a higher resistance than the other. So I guess that might be an indicator something is bad?

[Uncle Cracker]

After careful consideration, using all the resources at my disposal, I have determined that my final assessment is that it's fried...

[just started]

When you say nothing, you mean totally? Not even a little hum or any change in the way the rotor felt when you turned it by hand? Did you try the light bulb?

[jonmulzer]

Something does not add up here. Based on your earlier testing with a multimeter, it should have hummed or at the least popped a breaker. Did you do the lightbulb trick? If so, was it lit?

[crokett]

Light bulb was lit, and brightly too. I thought the motor should do something, but nada. No hums, pops or anything, even when turning by hand. The budget committee says I have to wait to get this motor repaired/replaced so I will try mixing the leads up tomorrow, I might have wired it incorrectly for 110.

[just started]

Did you try it without the light bulb? Did you ohm the power leads (minus the light bulb)?

[crokett]

Ok fellas, based on the assumption that my understanding, testing (or both) is flawed I did some more testing and wrote some stuff down.

The motor has a label with diagrams for wiring 110 v 220. When I got it it was wired for 220. The diagram labels the leads black, yellow, red and green. The only one I can ID is black. The others either have been replaced or the color is gone. For my purposes, I will call black #1, the rest will arbitrarily be #2, #3 and #4. For 110, the wires are paired, #1+#2 and #3+#4. For 220, #2+#3 are connected and #1,#4 are the hots.

Testing connectivity: My meter is set to 200 ohms. Open circuit (infinite resistance) is displayed as 1. The two meter leads connected show .3 ohms. The lightbulb by itself shows a resistance of 24. Testing the motor I get pair #1+#2 showing resistance of .6 ohms. Pair #3+#4 shows resistance of 1.5 ohms. Pair #1+#3 and #2+#4 show open. Pair #1+#4 shows open unless #2+#3 are connected together - as expected, this is 220V wiring.

One lightbulb terminal is wired to the white wire on my extension cord. A wire goes from other terminal to 1 motor wire pair. Black wire on extension cord is wired to other motor wire pair. When wired through bulb:
pairing #1+#2 and #3+#4 shows resistance of 26.5 ohms and when cord is plugged in, lightbulb lights brightly, motor does not run. Any other combo of motor wire pairs, circuit shows open and lightbulb does not light.

So I am pretty sure based on difference in resistance and visual evidence one coil is bad. I am also pretty sure it is the coil for wire pair #1+#2 since that pair shows resistance closer to just sticking the meter leads together. Correct?