rewinding a dc motor

[Mike Gibson]

I am getting ready to rewind a motor. Can it be wound 3 phase if it has brushes? If so how would the wire ends be connected?

[Mark Parsons]

Greetings Mike,

A brushed DC motor by definition is not 3 phase, it is DC. The brushes commutate the DC into successive rotor windings to cause a continuous magnetic attraction between individual coils and the permanent magnets on the stator.

A PM brushed DC motor can be used 'as is' for a DC generator. It will handle the same power as a generator as it is rated for as a motor. Motor / generator are mirror images of the same thing.

If your motor needs a rewind due to burnt windings or bad commutation contacts it may be better to find another motor in better shape. If it is the exact size you need and another is not readily available then you can take it to any motor rewind shop and have a professional job done with slot papers, varnish dipping, new brushes, bearings, etc, for relatively little money.

If rewinding yourself, I would use the same configuration as originally manufactured. Same wire gauge and number of turns in each slot.

A PM alternator is configured reverse to a PM DC motor. The magnets rotate and the stator coils are rectified to produce the DC. This type of AC motor / alternator is more reliable due to no brushes.

If you are interested in learning more about the different motors and theory, a condensed tutorial is published on the Reliance Motor web site - http://www.reliance.com/mtr/mtrthrmn.htm A more comprehensive tutorial is - http://www.eatonelectrical.com/unsecure/html/101basics/Module16/Output/WhatYouWillLearn.html

Regards,
Mark

[Mark Stirling]

Hi Mike,

I recommend a book called Electric Motor Repair - Robert Rosenberg, Holt Rhinehart pub. It covers the practical side of motor rewinding. Before you tear the windings apart you will want to check the connection arrangement and coil spans.

Mark