Identifying a 3-ph motor with no dataplate

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BigMouse
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Identifying a 3-ph motor with no dataplate

Post by BigMouse » Sun, 30 Sep 2012, 22:07

A while back I picked up a 132frame aluminium 3-phase induction motor. There was an ABB sticker on it, but that was just from a service centre. There are no other markings on the motor, and no dataplate. The junction box has 6 terminals, so I set it to the lower voltage configuration (based on other motors I've played with) and have been running 230vac on it without incident, though I've not loaded it. I'd like to get some more detailed specs for it, such as number of poles, actual voltage ratings, power rating, etc. I know I can get the poles from running the motor and measuring the RPM, but what about the other stuff? Any tips? I've had the end bells off to grease the bearings (they're very worn out) though I didn't take any photos.

If anybody is happy to help out with identification, I'll take whatever photos you need.

I already have a motor custom wound to 48vac for my conversion, but this one is a lighter frame (aluminium end bells instead of cast iron) and it'd be nice to have a spare either just to have on hand, or to use in other projects. Or maybe I could be tempted to siamese them together. Siamese AC induction motors... has this been done? ;-)

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Identifying a 3-ph motor with no dataplate

Post by coulomb » Sun, 30 Sep 2012, 22:17

BigMouse wrote: I'd like to get some more detailed specs for it, such as number of poles, actual voltage ratings, power rating, etc.
You might get some clues from an auto-ident using a VFD of some sort. You could compare resistance with other motors of the same frame size to get an idea of power rating. Another clue could come from how fast the RPM comes down with load. Again, it would be helpful to compare with other motors. But for this you will need a mechanical load, which could be awkward to arrange in the multi kilowatt range.
Siamese AC induction motors... has this been done? ;-)

I think you'd really want dual controllers, and that makes the idea rather less attractive, I think.
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Identifying a 3-ph motor with no dataplate

Post by coulomb » Sun, 30 Sep 2012, 22:25

For a really crude relative-rpm measurement, you could maybe paint a stripe on the shaft or pulley if there is one and observe it under non-compact fluorescent light (this is actually flashing at 100 Hz). Maybe two stripes on opposite sides would work better. For a 4-pole motor, 4 stripes might work better again. Alternating red and blue (e.g.) stripes might tell you whether it is 2 or 4 pole.

I've never tried it, but I imagine that slip of up to ~ 2 Hz would be visible.
Last edited by coulomb on Sun, 30 Sep 2012, 12:28, edited 1 time in total.
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Identifying a 3-ph motor with no dataplate

Post by BigMouse » Sun, 30 Sep 2012, 22:25

coulomb wrote:
Siamese AC induction motors... has this been done? ;-)

I think you'd really want dual controllers, and that makes the idea rather less attractive, I think.


Nothing wrong with that, if the controllers are designed to work together ;-)

Thanks for the tips. I suppose if it's 4-pole (same as my other motor), it could be wound the same regardless of the original power/voltage (assuming the slot numbers and sizes are the same).

I bought the motor to use as a dyno load for my custom wound one, but I'm finding that it may just be easier to put it in a car and use THAT as a load.

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