Reduce the air gap

Increase the field strength

Minimize the magnetic losses

Spread out flux uniformly in the air gap

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