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A 3-phase induction motor has a starting torque of 200 N-m when switched on-directly to supply. If an auto-transformer with 50% tapping is used for starting, the starting torque would be

A 3-phase induction motor has a starting torque of 200 N-m when switched on-directly to supply. If an auto-transformer with 50% tapping is used for starting, the starting torque would be Correct Answer 50 N-m

Starting torque with auto-transformer is x2 times the starting torque with the direct switching.

Current drawn from the supply = x2 Isc

x is the tapping of auto-transformer

Starting torque with auto-transformer = (0.5)2 × 200 = 50 N-m

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