Troubles in D.C. Machine

1. Failure to start

This may be due to

1. Ground fault
2. Open or short-circuit fault
3. Wrong connections
4. Too low supply voltage
5. Frozen bearing
6. Excessive load.

2. Sparking at brushes

This may be due to

1. Troubles in brushes- it is due to irregular contact surface such as small spring tension, wrong brush setting etc.
2. Troubles in commutator- It is due to dirt layer present in commutator surface.
3. Troubles in armature- It is due to open an armature coil which passes the brush.
4. Excessive load.

3. Vibrations and pounding noises

These may be due to

1. Worn bearings
2. Loose parts
3. Rotating parts hitting stationary parts
4. Armature unbalanced
5. Misalignment of machine
6. Loose coupling etc.

4. Overheating

The overheating of the machine may be due to

1. Overloads
2. Sparking at the brushes
3. Short-circuited armature or field coils
4. Too frequent starts or reversals
5. Poor ventilation
6. Incorrect voltage.