Maintain constant voltage

Collects the current unidirectionally

Reduces the voltage drop at brushes

Increases the terminal voltage than rated

Steel and graphite

Carbon and graphite

Cast iron and graphite

Aluminium and graphite

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