The torque developed in the squirrel cage induction motor with auto-starter is _______.

Autotransformer Starting of induction motor

When the full supply voltage per phase (V₁) is applied to the motor with direct switching, then the starting line current drawn by the motor from the supply line is given by,

Now, with the autotransformer starting, if tapping of the autotransformer with transformation ratio 'k' is used, then the voltage available across the secondary winding terminals of the autotransformer is kV₁. Hence, the starting current of the motor with autotransformer starting is given by:

If the no-load current of the transformer is neglected, then, the ratio of currents in a transformer is inversely proportional to the voltage ratio:

∵ T α I

Therefore, the torque developed in the squirrel cage induction motor with auto-starter is K2 × torque with direct switching.