Starters are used with DC motors because

A starter is necessary to start a DC motor because it restricts initial high armature current that exists, as the value of starting back-EMF is zero

Important:

A resistor is used in the starter for a DC shunt motor

• When the connected dc motor is to be started, the lever is turned gradually to the right
• When the lever touches point 1, the field winding gets directly connected across the supply, and the armature winding gets connected with resistances R1 to R5 in series
• During starting, full resistance is added in series with the armature winding
• Then, as the lever is moved further, the resistance is gradually is cut out from the armature circuit
• Now, as the lever reaches to position 6, all the resistance is cut out from the armature circuit and armature gets directly connected across the supply