GATE EE Electrical Machines PYQs & Answers

Questions 1–10 of 79. Imported answers require independent review unless marked reviewed.

A 15 kVA, 1100 V/220 V, single-phase two-winding transformer is configured as a 1.32 kV/1.1 kV autotransformer.

What will be the rating of the autotransformer?

Your answerChoose one option.

60 kVA

75 kVA

90 kVA

100 kVA

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A certain application requires power at a frequency of 16.67 Hz, while the available grid frequency is 50 Hz. A 3-phase synchronous motor connected to the 50 Hz, 3-phase grid, driving a synchronous generator, is used for this application.

Which one of the following combinations is a suitable choice for the number of poles in the motor and generator, respectively?

Your answerChoose one option.

2, 6

6, 2

4, 6

6, 4

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Which one of the following options is correct regarding the typical double-squirrel-cage structure used in induction motors?

Your answerChoose one option.

At starting, a larger portion of the rotor current flows in the outer cage

At starting, a larger portion of the rotor current flows in the inner cage

At rated speed, most of the rotor current flows in the outer cage

The purpose of the double-squirrel-cage structure is to lower the effective rotor resistance at start

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The figure shows the single-line diagram of a synchronous generator delivering

of power at unity power factor to an infinite bus.

Diagram for Electrical Engineering question 22

denotes the stator current phasor. If the field excitation is increased, which one of the following options correctly describes its effect on the stator current, power factor, and load angle of the machine?

Your answerChoose one option.

Stator current increases, power factor becomes lagging, load angle remains the same

Stator current decreases, power factor becomes leading, load angle remains the same

Stator current increases, power factor becomes lagging, load angle decreases

Stator current increases, power factor becomes leading, load angle increases

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A 220V/12V single-phase transformer is designed for use in India and rated 100 VA at 50 Hz. Later, this unit is shipped to the USA where it is used as a 110V/6V transformer at 60 Hz.

Which of the following statements is/are correct?

Your answerSelect all correct options. You can choose more than one.

No-load current drawn would be smaller for operation in the USA compared to that in India

For the same load current, the losses would be higher in the USA compared to that in India

The peak magnetic flux density in the core would be higher while operating in the USA compared to that in India

The eddy current losses in the core would be approximately 44% higher while operating in the USA compared to that in India

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Three single-phase 11kV/3.3kV transformers are connected to form a three-phase transformer bank with connections as shown.

Diagram for Electrical Engineering question 38

Considering ABC phase sequence, the vector group of the transformer is:

Your answerChoose one option.

Dd0

Dd4

Dd6

Dd10

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A balanced three-phase supply is given to a 30 kW, 4-pole, 400 V, 50 Hz, wound rotor induction motor with Y-connected stator and rotor windings. The motor is driving a constant torque load. With shorted sliprings, the machine runs at 1476 rpm.

When an external non-inductive resistance of 0.27 Ω per phase is connected in series in the rotor circuit, the steady-state speed drops to 1404 rpm.

Neglecting rotational losses, the actual per phase rotor winding resistance is ___ Ω

(Round off to two decimal places)

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The operating region of the developed torque (

) and speed (

) of an induction motor drive is given by the shaded region OQRE in the figure. The load torque (

) characteristic is also shown. The motor drive moves from the initial operating point O to the final operating point S. Which one of the following trajectories will take the shortest time?

Diagram for Electrical Engineering question 26

Your answerChoose one option.

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Instrument(s) required to synchronize an alternator to the grid is/are

Your answerSelect all correct options. You can choose more than one.

Voltmeter

Wattmeter

Synchroscope

Stroboscope

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The induced emf in a 3 kV, 4 pole, 3-phase star connected synchronous motor is considered to be equal and in phase with the terminal voltage under no load condition. On application of a mechanical load, the induced emf phasor is deflected by an angle of 2° mechanical with respect to the terminal voltage phasor. If the synchronous reactance is

, and stator resistance is negligible, then the motor armature current magnitude, in ampere, during loaded condition is closest to, __________ (round off to two decimal places).

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GATE EE Electrical Machines PYQs

How to practice Electrical Machines

Question 17

Question 20

Question 21

Question 22

Question 31

Question 38

Question 59

Question 26

Question 28

Question 35