Electric motor troubleshooting

[Bob W]

I have a Delta 13" portable planer that I have been using outside with a Honda 3500 watt generator providing power. Yesterday (11/29), the planer motor started to make noise and had that burning smell, I immediately shut everything down. I checked the brushes on the motor and one they both had chips on them; one worse than the other.



My questions are:

Are chipped brushes normal?

Did the noise cause the brushes to chip?

Did the brushes cause the noise?



Any help appreciated. Thanks.

 

[AKAMAC]

The motor on your saw should have a TEFC rating. If it doesn't then you probably got some junk in between the brushes and stator. Rotate the motor by hand to make sure there is no damage to the bearings, you can actually file the brushes flat and re-use them if they are not too worn. If the brushes are rough they will make the motor sound like it is binding up while running.

TEFC= totally enclosed fan cooled

 

[Tim1]

not enough generator

Hey bob, it sounds like you don't have enough generator for that planer. 3500 watts is only 35 amps and you might want to check with a amprobe the draw that the motor is requiring under load and startup! Typically not enough current for any reason(lenghth of cord, small wire,too much load,low amps) will cause the motor to get hot and self destruct. Just my experience, the hard way. Tim

 

[illflem]

Many times when the brushes fry the communtator gets scored also and will tear up new brushes rapidly.

A resurfacing tool like this one that you hold against the communtator while the motor is running will fix it right up and costs less than $10.



http://www.grainger.com/Grainger/productdetail.jsp?ItemKey=3GD76

 

[Bob W]

Tim, the planer has a 15 amp motor, so I assumed (bad idea, I know) that the generator would have more than sufficient power, even when the planer is under load.



AKAMAC, today I checked the planer in the basement. I couldn't turn it fast enough to hear any noise, or feel anything out of the ordinary. I plugged it in, and though it didn't sound as bad as the other day, it didn't sound like new. This may be due to using it outside all the time, but I did see more of the "blue arcing" that I've noticed on some motors. Is that normal? Can you tell that I'm an electrical troubleshooting "virgin"?



Thanks for all the help everyone, it's always nice to learn something.



Bob