PM Motor Repair Help

I would like to repair a 12 VDC PM field motor which has one fiel piec loose. The adhesive yielded and one pole fell off. In the process o cleaning off the old adhesive I lost track of the correct orientatio of th loose field piece. It can go into the motor frame in either of tw ways. Both o the field pieces are marked with a dot on one end. Do the dots go i th same direction or in the opposite direction

Desperate in L

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Generally speaking, dots indicate phase orientation; or in your case magnetic orientation. As a WAG (wild assed guess) I'd say the dots must go in the same direction. Since the adhesive is loose, why not try placing the dots in both directions as a test?

Bob Swinney

Reply to
Robert Swinney

Hi Bob Its hard to "try" since the motor won't run with a loose pole piece. It must be glued in place. I would guess that the dots would go on opposite ends since you want the poles to be additive (N to S, N to S) and all the poles would be made in a seperate process and all marked the same. The installer would select the correct direction.

I only get one try and I would like to not screw it up. Ceramic magnet pole pieces crack real easy.


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Well, then, look really carefully at the glue pattern on the piece that came out, and at the glue pattern in the socket, and see which way it went in. Might need strong light and 10X magnification, but maybe you'll get lucky and can figure it out. The other night I had to figure out which way two wires went into an auxiliary power connector on my BMW motorcycle, figured if I hooked them up backwards I might fry hundreds of dollars worth of German electronics, absolutely no reference material anywhere, looked real carefully, saw something, put it in consistent with what I resolved optically, and it worked. Whew.


Reply to
Grant Erwin

Think about a simple two pole electromagnet field motor with a single winding on the crosspiece of a "U" shaped magnetic structure, so the ends of the "U" form the two poles. With DC applied to the field, one pole will be north and the other south.

So, orient your loose magnet so that it is trying to pull toward the other pole piece, not push away from it.



Reply to
Jeff Wisnia

I may be mistaken but I do not think that you can change the polarization by rotating the magnet. I think the poles are at the faces of the magnet. The concave side would be one pole and the convex side the other. Checking the glue pattern is the best way to know which way it was installed. Clean it good, use a good epoxy and clamp it good while hardening. I have repaired automobile window and seat motors this way. Be sure you have the frame and rotor well under control when reassembling or you may damage something when the rotor is suddenly pulled in.

Reply to
Don Young

Right! And cover the other magnet with a rag or piece of wood. If that loose magnet gets away from you and crashes into the other one, you're out of luck.

Reply to
Don Foreman

If the magnets are simple 'C' shaped items it doesn't matter which way round they are installed.

Unless the magnets are mechanically assymmetric the ONLY thing that matters is that the magnets are radially magnetised with one magnet with an inner North pole and the other with an inner South pole.


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