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GATE 2020: Toppers Quiz 18 (App update required to attempt this test)

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Question 1

A power system consist of 200 buses out of which 14 buses are generator bus, 15 buses are ones with variable shunt capacitors. 100 buses are load bus and 70 buses are ones with fixed shunt capacitors. The size of the Newton Raphson Jacobian Matrix is

Question 2

An alternator is running at a constant speed of 600 rpm and generating a voltage of frequency 60 Hz. Determine the number of field poles of the generator.

Question 3

Consider the common-collector amplifier in the figure (bias circuitry ensures that the transistor operates in forward active region, but has been omitted for simplicity). Let be the collector current, be the base-emitter voltage and be the thermal voltage. Also, and are the small-signal transconductance and output resistance of the transistor, respectively. Which one of the following conditions ensures a nearly constant small signal voltage gain for a wide range of values of ?

Question 4

In a 3 φ unsymmetrical transmission system the distance between conductors ab, bc and ca is 3 m, 4 m and 5 m respectively. The radius of each conductor is 2 cm. The capacitance of each phase is _________ pF/m.

Question 5

A single phase, 20 kVA, 2000/200V, 50 Hz transformer is reconfigured as an auto transformer to get an output voltage of 2200V. calculate the maximum kVA rating as an auto transformer –

Question 6

A discrete time system is designed using only adders, gains and delays. The transfer function of the system is
System H:
Y and X are two polynomial in z. When the system was constructed, users were dissatisfied with its response. So a new system H1 was designed by modifying system H.
System H1: Every delay element in H is replaced by a cascade of three delay elements followed by gain of 8.
If the system H had a pole at ej3π/2. then the system H1 will have a pole at

Question 7

In class-D commutation circuit, Edc = 100 V, L = 5 mH, C = 20 mF. Determine the minimum on time of SCR 1 and peak-value of capacitor current.

Question 8

A 3-phase induction motor rated 25 hp, 440 V with an efficiency of 0.85 and a power factor of 0.9 lag on full load is supplied from a 6600/440 V,  connected transformer. Ignoring the magnetizing current, the current in the high and low voltage phases when the motor is running at full load are respectively

Question 9

A universal motor (ac - operated) has a 2-pole armature with 960 conductors. At a certain load, the motor speed is 5000 rpm and the armature current is 4.6 A, the armature terminal voltage and input power are respectively 100 V and 300 W. Calculate the effective armature reactance in ohm assuming on armature resistance of 3.5 Ω.

Question 10

A resistance of 5 Ω is used for earthing the neutral of a 5 MVA, 11 kV alternator. The earth fault relay is set to operate at 0.5 A. The CTs have a ratio of 1000:10. The percentage of alternator winding unprotected is

Question 11

Given points M (1, 4, 2), N (-2, -3, -1), P (-3, 2, 2). Determine the unit vector in the direction of vector , where are the vectors pointing from the origin to the point M, N, P respectively.

Question 12

A synchronous generator of reactance 1.20 pu is connected to an infinite bus bar through transformer and a line of total reactance of 0.60 pu. The generator no load voltage is 1.20 pu and its inertia constant is H = 4 MW-s/MVA. The resistance and machine damping may be assumed negligible. The system frequency is 50 Hz. The frequency of natural oscillations if the generator is loaded to 50% of its maximum power limit is _______ Hz.

Question 13

The open-circuit and short-circuit characteristic of a single-phase synchronous generator are shown on the same graph below.

A field current of 60 A produces the rated voltage. If the effective armature resistance of the generator is 0.3 Ω, determine the synchronous reactance of the machine [in Ohm].

Question 14

A 220 V, 1000 rpm, 60 A separately-excited dc motor has an armature resistance of 0.1 Ω. It is fed from a single-phase full converter with an ac source voltage of 230 V, 50 Hz. Assuming continuous conduction, the firing angle for rated motor torque at (– 500) rpm is __________ °.

Question 15

Find the energy deliver by the independent source in the circuit given below-

Question 16

A 3- ɸ diode bridge rectifier charges a 200 V battery. Input voltage to rectifier is 3- ɸ, 400 V, 50 Hz with current limiting resistor in series with the battery of 15 Ω and an inductor in the load marks the output current almost ripple free. Source transformer rating (in kVA) is:

Question 17

A 100 MVA, 50 Hz generator feeding power through a double circuit transmission line with initial rotor angle 60 °. A 3 phase fault occurs at middle point of one of the lines. the internal voltage of the generator is 1.5 pu and equivalent transfer admittance during fault is 0.5 pu and the infinite bus voltage is 1.1 pu. The generator has an inertia constant of 4 MJ/MVA and it was delivering 1 pu power prior of the fault. The inertia constant in (MJ – sec/elect degree) is –

Question 18

A 3ɸ slip ring induction motor rated 16.5 kW, 6 pole, 50 Hz which runs at 950 rpm at full load with a rotor current per phase of 30 A. Total mechanical losses are 1 kW. The rotor resistance per phase is

Question 19

A 3-, half wave controlled rectifier is supplying an R-L load, where L∞. A freewheeling diode is also connected across the load. The converter is operating with firing angle of 60, then the RMS value of fundamental source current is

Question 20

In the sequential circuit below, initially the flip flop is cleared. If the input clock frequency is 5 KHZ. Than find the output clock frequency (in KHz).

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Dec 5ESE & GATE EE