GATE EE year:2018 PYQs & Answers — Page 7

Questions 61–65 of 65. Imported answers require independent review unless marked reviewed.

Topic practice 65 questionsPage 7 of 7

A 3-phase 900 kVA,

(

/Y), 50 Hz transformer has primary (high voltage side) resistance per phase of 0.3

and secondary (low voltage side) resistance per phase of 0.02

. Iron loss of the transformer is 10 kW. The full load % efficiency of the transformer operated at unity power factor is ________ (up to 2 decimal places).

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A 200 V DC series motor, when operating from rated voltage while driving a certain load, draws 10 A current and runs at 1000 r.p.m. The total series resistance is 1

. The magnetic circuit is assumed to be linear. At the same supply voltage, the load torque is increased by 44%. The speed of the motor in r.p.m. (rounded to the nearest integer) is ______.

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A dc to dc converter shown in the figure is charge a battery bank, B2 whose voltage is constant at 150 V. B1 is another battery bank whose voltage is constant at 50 V. The value of the inductor, L is 5 mH and the ideal switch, S is operated with a switching frequency of 5 kHz with a duty ratio of 0.4. Once the circuit has attained steady state and assuming the diode D to be ideal, the power transferred from B1 to B2 (in Watt) is __________ (up to 2 decimal places).

Diagram for Electrical Engineering question 53

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The equivalent circuit of a single phase induction motor is shown in the figure, where the parameters are

and

is the slip. At no-load, the motor speed can be approximated to be the synchronous speed. The no-load lagging power factor of the motor is _________ (up to 3 decimal places).

Diagram for Electrical Engineering question 54

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The voltage

across the terminals a and b as shown in the figure, is a sinusoidal voltage having a frequency

radian/s. When the inductor current

is in phase with the voltage

, the magnitude of the impedance

(in

) seen between the terminals a and b is ________ (up to 2 decimal places).

Diagram for Electrical Engineering question 55

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GATE EE year:2018 PYQs

Question 51

Question 52

Question 53

Question 54

Question 55