Electrical Engineering ⇒ Topic : Starting of Induction Motors

Starting of Induction Motors The start a motor from rest and to bring it so normal operating speed required an input of energy (a) to supply the losses and (b) to provide the rotating path with kinetic energy. When the motor is direct switched on to a normal voltage supply, it draws a large starting current which is almost 6 to 7 times the rated full load current. Then

where T_s = Starting Torque, T_n = Full load torque, S_n, = Full load slip.

Starting of slip ring motors:- A Rheostat is provided in the rotor circuit.During starting the rheostat will be in maximum resistance position and the resistance being gradually cut out as the motor speeds up

Starting or squirrel cage induction motors :- A reduced voltage is applied during starting. The voltage is gradually increased by reducing the resistance as the motor picks up speed