Limit current in NVC
Protect the coil from short circuit
Protect the motor from overload
Protect the armature from short circuit
To regulate field voltage
To carry the load current
To keep maximum inductance
To reduce the armature reaction
Shunt motor
Series motor
Cumulative compound motor
Differential compound motor
Constant load requirements
Constant speed requirements
High starting torque requirements
Constant speed under varying load requirements
Limit the field cur
Limit the field voltage
Control the motor speed
Limit the armature current