GATE EE 2022 Set 1 — Question 64
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Electrical Machines → Synchronous Machines → Synchronous Reactance & Regulation
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Question
A star-connected 3-phase, , , synchronous motor has a synchronous reactance of per phase with negligible armature resistance. The shaft load on the motor is while the power factor is leading. The loss in the motor is . The magnitude of the per phase excitation emf of the motor, in volts, is __________. (round off to nearest integer).
Correct answer
240 to 248
Solution
1.Calculate the input power ():
The shaft load is the output power (). The total loss is .2.Calculate the phase current ():
For a 3-phase system: Since the motor is star-connected, .
3.Calculate the phase voltage ():
4.Calculate the excitation emf per phase ():
For a synchronous motor, the phasor equation is .Given a leading power factor of , .
Taking as reference:
Rounding to the nearest integer, we get .
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