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GATE 2022 : Electrical Machine Quiz 11

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Question 1

In a closed-loop control of squirrel cage induction motor, the field-oriented control strategy implemented is

Question 2

In Induction motor, what is the speed of rotation of rotor mmf vector with respect to respected to rotor (Ns is synchronous speed of rotating magnetic field and Nr is speed of rotor).

Question 3

Suppose a magnetic material is in the form of a cuboid with length 3m, breadth 1.5m and height 0.2m. An AC supply of 50 Hz frequency is supplied across it. Now the length of the cuboid is halved and breadth is reduced to one-third. Also the frequency is increased to 60 Hz. Find the ratio of hysteresis loss in original case to new case.

Question 4

An 8-pole generator has an output of 200 A at 500 V, the lap-connected armature has 1280 conductors, 160 commutator segments. If the brushes are advanced 4-segments from the no-load neutral axis, what is the cross-magnetising ampere-turns per pole?

Question 5

A synchronous generator delivering power of 0.9 pu. The synchronous reactance is 1 pu. The prime mover input is increased by 5% and the generator is running in overexcitation with the excitation emf of 1.8 pu. The percentage change in reactive power is___________.

Question 6

A 3-ϕ, 14.5 kW, 400V, four pole, 60 Hz, IM delivers full output power to a load connected to its shaft and running at speed of 1728 rpm. The windage and friction loss of the motor is 500 W. The value of rotor copper loss of motor will be-
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