The induction motors are widely used worldwide for various applications.The motor takes high starting current at start.When the three phase supply is fed, a rotating magnetic field set up in the air gap.The flux get linked to the rotor winding and voltage is induced in the rotor conductor.The magnitude of the induced voltage depends on the difference between the synchronous speed and the actual speed of the motor.At start, this difference is maximum and equals to 1. We can say the slip of the motor at start is equal to 1.The induced rotor voltage is equal to ;
Er= slip* stator voltage(ES)
At start, slip = 1
Also the rotor reactance is more because of the higher rotor frequency as fr=s*fs
In a nutshell, the rotor is highly inductive at starting, hence the motor takes about 6 times current of its FLC.
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