A 2200 V, 2600 kW, 735 rpm, 50 Hz, 8 pole, 3-phase squirrel-cage induction motor has following parameters referred
A 2200 V, 2600 kW, 735 rpm, 50 Hz, 8 pole, 3-phase squirrel-cage induction motor has following parameters referred to the stator: R, = 0.075 2, R = 0.12, X, = 0.45 2, X = 0.55 12. Stator winding is delta connected and consists of two sections connected in parallel.
(1) Calculate starting torque and maximum torque as a ratio of rated torque, If the motor is Started by star-dalta switching. What is the maximum value of line current during starting?
(ii) Calculate transformation ratio of an auto-transformer so as to limit the maximum starting current to twice the rated value. What is the value of starting torque?