GATE 2025 IN – Question 46
A 2-pole, 50 Hz, 3-phase induction motor supplies power to a certain load at 2970 rpm. The torque-speed curve of this machine follows a linear relationship between synchronous speed and 95 % of synchronous speed. Assume mechanical and stray losses to be zero. If the load torque of the motor is doubled, the new operating speed of the motor, in rpm, is
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Correct answer: (A) 2940
Explanation
Synchronous speed is 120f/p=120×50/2=3000 rpm.
Initial slip speed is 3000−2970=30 rpm.
In the stated linear torque–slip region, doubling torque doubles slip speed to 60 rpm.
New speed is **2940 rpm, A**, still within the specified 95%–100% range.