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Topic Title: old 3 phase induction motors
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Created On: 02 July 2013 06:34 PM
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 02 July 2013 06:34 PM
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chunk522

Posts: 126
Joined: 12 December 2010

Hi everyone,
Ive been out to and old Wadkin drill (to say the least in a very good condition) today as the owner was complaing of flashing coming from the motor casing and tripping out the mcb.
I took the terminal cover off and there were only the 3 wires on the terminal so Im guessing the star connection must be internally connected giving me a limit on testing the windings, I stripped out the rotor shaft and the cage and cables were inclosued in some kind of pitch solid material, I have never come across one of these before my question is is there another way of testing the windings phase to phase and does any one know if the motor can be rewound as its so old Im guessing 1930s motor
Thanks
 02 July 2013 09:14 PM
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statter

Posts: 126
Joined: 06 February 2013

I'd try the following
Winding continuity - look for equal readings between terminals in all combinations A-B, A-C, B-C.

Insulation test to metalwork.

If you can expose the windings it can be rewound.
Can you see where it has been sparking - check the rotor too - sparking would be very unusual there but if there is no visible damage to the stator you have to consider it. The other source would be loose terminals - easy to check.

I've seen physical removal (knife/chisel), Heat and solvents all used successfully. The main thing is to avoid damaging the insulation between the laminations as these would then have to be separated and the insulation restored and this could be awkward/ expensive.
 02 July 2013 10:45 PM
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chunk522

Posts: 126
Joined: 12 December 2010

Originally posted by: statter

I'd try the following

Winding continuity - look for equal readings between terminals in all combinations A-B, A-C, B-C.



Insulation test to metalwork.

I have done these and everything is ok



If you can expose the windings it can be rewound.

I am not sure on this I will post photo if I can .

Can you see where it has been sparking - check the rotor too - sparking would be very unusual there but if there is no visible damage to the stator you have to consider it. The other source would be loose terminals - easy to check.



I've seen physical removal (knife/chisel), Heat and solvents all used successfully. The main thing is to avoid damaging the insulation between the laminations as these would then have to be separated and the insulation restored and this could be awkward/ expensive.


Thanks statter I am unsure what the material is and there is no obvious sign of where it as been spaking as the stator is black not like a normal cage hopefully this pic will upload you can see the cables entering the stator into the solid materialm[URL=http://s814.photobucket.com/user/sadlerelec/media/335.jpg.html][/URL]
 03 July 2013 05:00 PM
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statter

Posts: 126
Joined: 06 February 2013

.....looks clean enough, casing looks fully enclosed from your pics so where exactly was it sparking?
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