The cause of the failure of dc motor controller and processing

Cannot be used normal starter is a dc motor controller is a kind of encounter. For this kind of circumstance how to deal with? Small make up to introduce below. 1. May be caused by power supply no voltage. Measures: check the power supply and fuse, to see if a failure. 2. May be caused by excitation circuit disconnection. Measures: check the field winding and starter, to see whether there is a disconnect. 3. May be caused by brush circuit disconnection. Measures: check the armature winding and commutator brush, see contact condition is normal. The above is not the cause of the starting and processing is introduced.