direct current motor burning


Thread Starter


question is regarding D C motors

we have face some problem on direct current motor. problem on commotator always sparking inside the winding and motor will get burn
Responding to Shetty's 23-Juk (14:54) question... There are a number of causes, To start with few:

a) Brushes not diametrically-opposed.

b) Brush "fingerprint" too large.

c) Brushes out of line; Brushes loose in holder.

d) Brush dimensions re different.

3) Electrical
a) Arcing excessive, supply voltage too high.

b) Arcing products follow brushes around commutator; armature coil faulted.

Then too, there are symptoms related to sound, that is chattering, humming, pounding.

Of course other symptoms are related to motor-type, motor-size, series-wound, shut-wound, compound-connected, frequency of starts, duty, etc.

In conclusion Shetty, you must provide additional info.

Regards, Phil Corso
personally i check the all above conditions.

motor capacity 1000kw and 600 armature voltage

field 210volt and 24.6amps

this field weakening motor. commutator surface keep in good clean
motor has water cooling system with heat exchanger
When did this problem start?

Was the motor running without this problem for some time and then it started?

Did it start after some maintenance or cleaning was performed on the motor?

How long has this motor been in service?

When was the last time the motor was "serviced"? A 1000kw motor is a pretty large motor and most large motors usually get regular, periodic service, including removal to a shop for cleaning and inspection and repair, if necessary. This motor also has cooling, another indication of it's physical size and load.

Has the current being drawn by the motor increased since before the problem began? Decreased?

Does the arcing increase with load, or is it present during unloaded operation also?

It would seem there is something physically wrong with the motor. Some DC motors have compensation windings to try reduce or eliminate arcing. There are all manner of different types of motors and windings and configurations.

It would seem prudent to have a knowledgeable person or firm have a look at the motor and how it's being operated and assess it's entire condition and make some recommendations.

Another cause of arcing is incorrect brush types and also the humidity of the air in the commutator area. Has something changed recently? New supplier for the brushes? Is there cooling air being supplied to the commutator that isn't being properly filtered or conditioned?

Loose brush holders/rigging can also cause arcing. But, it's more likely that something's amiss somewhere in the motors windings. Again, with a motor this large (and presumably important) it's a good idea to have a knowledgeable party in to have a look and make recommendations.
Shetty... Excellent, thus far.

Now provide some data regarding: driven machine; load (Amps); age; duty (27/7 or other); coolant inlet and outlet temp; coolant flow-rate; ambient temperature; motor temperature; speed; and what has been tried to correct problem, especially those suggested or recommended by the motor/machine supplier.

Regards, Phil
I would like to add two small checks that needs to be performed to all the above.

1. Have you checked the eccentricity of the commutator, i.e. is the commutator a perfect circle? For this check you need the machine shutdown and isolated, and it should be possible to turn it slowly by hand or crank.

2. Are the commutator slots properly done, i.e. is there sufficient undercut between the commutator segments to ensure that the segment insulation is not touching the brushes?

The surface condition of the commutator gives quite a good indication of the cause of problem. Brush/brushgear manufacturers give refernce charts of various effects and causes of brush sparking. Mind you this will be just a lead, proper diagnostics should be done by someone knowledgeable in DC machines.