Heavy short circuit in load

Running without load continuously

Continuous running without break

Change of direction of rotation very often

Field coils

Armature core

Laminated pole core

Winding conductors in armature

Because of armature reaction effect

Due to increased in armature resistance

Because of brush voltage drop decreases

Due to increased in shunt field inductance

Shunt generator

Series generator

Differential compound generator

Cumulative compound generator

Replacing the brushes frequently

Heating the machine by running periodically

Cleaning the commutator segments regularly

Blowing hot air in to the machine during maintenance