DC motor fault zone analysis is a vital plan of any DC motor maintenance program. Several troubles may arise in a DC motor. A few of them are discussed below:
- Failure to start
- Sparking at brushes
- Vibrations and pounding noises
- Overheating of DC Motor
Reasons for Failure to start
Failure to start may be due to the following reasons
- ground fault
- open or short-circuit fault
- wrong connections
- too low supply voltage
- frozen bearing
- excessive load.
Read: Working Principle of DC Motor
Reasons for Sparking at brushes
Sparking at brushes in a dc motor may be due to
- troubles in brushes
- troubles in commutator
- troubles in armature
- excessive load.
Brush troubles may arise due to the insufficient contact surface, too short brush, too little spring tension or wrong brush setting.
Commutator troubles may be due to dirt on the commutator, high mica, rough surface or eccentricity.
Armature troubles may be due to an open armature coil. An open armature coil will cause sparking each time the open coil passes the brush. The location of this open coil is noticeable by a burnt line between segments connecting the coil.
Read: Armature Reaction in DC Motor
Reasons for Vibrations and pounding noises
Vibrations and pounding noises may be due to
- worn bearings
- loose parts
- rotating parts hitting stationary parts
- armature unbalanced
- misalignment of machine
- loose coupling etc.
Reasons for Overheating of DC Motor
The overheating of dc motor may be due to
- overloads
- sparking at the brushes
- short-circuited armature or field coils
- too frequent starts or reversals
- poor ventilation
- incorrect voltage
Read: Testing of DC Machines
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