Dc Motor Brush Weirdness

What would cause the brushes in a 250 HP DC motor wear very bad on one side and not the other on a motor that was recently rewound. Also we find the leads to the brushes burned off on that side in many cases. All the usual suspects have been checked.

Brush holder tension is the same on both sides

Have you checked motor balance ???

No vibration or alignment problems. I think it has something to do with the motor rewind but I just don't know what. I think something was not done right but I don't know what could have been done wrong to cause this.

Kid,

What kind of motor ie shunt, compound (short or long shunted?)
voltage current and all those numbers of course. Is motor run in only one direction or is it reversed?

One factor affecting brushes is temperature - is one side of motor hotter than other? Have aux blower cooling motor with more airflow over one set of brushes than another?

They are all set at same angle relative to commutator?

Both sides of brush rigging firmly bolted?

Intriguing to say least

Dan Bentler

I have seen two causes of this. One was the wrong brushes (different compound) installed on one side. The other was caused by a misaligned holder so the brushes in that holder were not aligned as they should have been on the commutator.

Another reason I have seen once is that the commutator was not cleaned up concentrically to the shaft. The new brushes bounced slightly and as they bedded in the dust dropped on one side and fed into the holder making it 'sticky'. Suggest you assemble brushes, rotate motor by hand and see if the brushes move in and out during one turn.
Regards Paul

If you can see the brushes bouncing on a newly rebuilt motor because of lack concentricity on commutator you should either get a new machinist or a new dial indicator.

Hmm he did give a thought on one side the carbon dust would tend to fall away from brush and holder and on opposite side tend to collect on them. Good argument for cleaning motors.

Dan Bentler