Arcs (Large Sparks) Occuring on a 1300kW DC Motor

[morteza4321]

sparks dc motor

We have got a 1300kW DC motor, Manufacturer BBC, we are getting arcs (large sparks) occuring in the armiture to the body of the motor. We are using the motor for a rolling mill gearbox, everytime the arcs (sparks) occur the motor is under zero load, ie no load is passed through the mill. PLease advise me what could be the cause of the arcs. And if possible how i can solve the problem, bear in mind that the motor has got a very large cooling system separate from it, also we have got billets being cut with blow torch nearby so might be from oxides in the air.
Thank You[/b]

 

[solvarg]

Not sure what you mean with "armature", but take a look at the length of the brushes. If they are not properly seated on the communator you will see sparks!
h**p://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/comtat.html