Reduce armature current

Reduce armature voltage drop

Run armature with less weight

Reduce the temperature of armature

Protect brushes from damage

Protect the residual magnetism

Avoid short circuit in armature

Avoid over loading of generator

Connect more loads

Reduce commutation effect

Neutralize armature reaction effect

Increase the efficiency of generator

Loose brush contact

Armature resistance is more

Field resistance is above critical resistance

Prime mover is running at above rated speed

Shunt generator

Series generator

Compound generator

Self excited generator