GATE 2020 EE – Question 27

Electrical Machines · Three-phase induction machines: principle of operation, types, performance, torque-speed characteristics, no-load and blocked-rotor tests, equivalent circuit, starting and speed control · 1 mark · Numerical answer

A three-phase, 50 Hz, 4-pole induction motor runs at no-load with a slip of 1 %. With full load, the slip increases to 5 %. The % speed regulation of the motor (rounded off to 2 decimal places) is ________.

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Correct answer: 4.10 to 4.40

Explanation

The no-load speed is $0.99N_s$ and the full-load speed is $0.95N_s$. The speed regulation is $\frac{N_{nl}-N_{fl}}{N_{fl}}\times100=\frac{0.99-0.95}{0.95}\times100=4.21\%$.