Why do we Need a starter in DC motors?

While starting a DC motor huge amount of current can be driven to the windings due to the absence of the back emf. The current may rise about 4-6 times higher than the rated load current of the winding wire. So, it can damage the winding of the motor at the starting itself. To prevent such high current rush, starters are used in DC motors.

Actually, a starter consists of a variable series resistance which is added to the armature of the motor. It is used in order to reduce the starting voltage across the winding.

When the motor speeds up the starter resistance decrease gradually. And it will disconnect completely when the armature attains enough speed to generate the back emf (that is the normal speed). At a full speed, the starter has no effect on the armature circuit of the motor. Then the contacts of the motor terminals will be directly connected.