Why is a starter necessary to start a DC motor?

Starters in DC motors

Starters are used to protect DC motors from damage that can be caused by very high inrush currents and torque during startup.

This is done by providing external resistance to the motor, which is connected in series to the motor’s armature winding and restricts the current to an acceptable level.

\(V=E_b+I_aR_a\)

where, V = Terminal voltage

Eb = Back EMF

Ia = Armature Current

Ra = Armature Resistance

As Eb is directly proportional to the speed. So, at the starting speed is zero, hence Eb = 0

At starting:

\(V=0+I_aR_a\)

\(I_a={V\over R_a}\)

Hence, starters are used to limit starting current as the current at the starting of the motor is high.