I have a dc motor and it is 800 hp. The problem is that it is pin firing under the brushes when i put it under load. We have turned the the comm,bought new brush holder & springs, also bought new brushes in thinking that they could have been of poor quality. We have also installed shimms under the poles pieces. After checking them the shims were the wrong thickness and not in the right order meaning alum, steel. Also notieced that 2 of the insulators were cracked and replaced. The neurtral was also adjusted.

any ideas?

 

It seems to be arcing on the trailing edge of the brush

 

1) I am thinkin of returning the comm

2) Removing shimms poles may be too strong

 

thanks joe

Looks like you are missing the arc suppression capacitors.

it is a 600 volt armature and the fields are 240 volts that would really be a big cap. I think the inpoles are too strong or the brush grade is to hard

new brushes often do that until they wear in, they only come with a slight C shape cut in the otherwise flat face of the brush. over time they`ll seat much better