Electrical Engineering ⇒ Topic : Series Motor

SERIES MOTOR

A series motor shown in Figure (a) can be run from either DC or AC (single-phase) supply provided that both the stator and rotor cores are laminated to limit the iron loss

               Figure (a) Series motor connected to AC supply.

Since field flux and armature current both change their magnitude and sign simultaneously, their product is always positive, even if both the parameters individually may be negative. Therefore, torque produced by the series motor is in the same direction for each half cycle of AC and is pulsating. We know

           ........... (1)

                 Figure (a) Field polarity with armature current variation

From Eq. (1), it is seen that the instantaneous torque has an alternating component,whose frequency is double the supply frequency.