Electrical Engineering GATE 2020 Questions with Answer

Ques 14 Control Systems

Consider a negative unity feedback system with the forward path transfer function:
(s² + s + 1) / (s³ + 2s² + 2s + K)
where K is a positive real number. The value of K for which the system will have some of its poles on the imaginary axis is:

Ques 15 Control Systems

The causal realization of a system transfer function H(s) having poles at (2,-1), (-2,1) and zeroes at (2,1), (-2,-1) will be

Ques 16 Control Systems

A stable real linear time-invariant system with single pole at p, has a transfer function:
H(s) = (s² + 100) / (s − p)
with a DC gain of 5. The smallest positive frequency, in rad/s, at unity gain is closest to:

Ques 17 Digital Circuits

A sequence detector is designed to detect precisely 3 digital inputs, with overlapping sequences detectable. For the sequence (1,0,1) and input data (1,1,0,1,0,0,1,1,0,1,0,1,1,0), what is the output of this detector?

Ques 18 Digital Electronics

An 8085 microprocessor accesses two memory locations (2001H) and (2002H), that contain 8-bit numbers 98H and BIH, respectively. The following program is executed:
LXI H.2001H
MVI A, 21H
INX H
ADD M
INX H
MOV M. A
HLT
At the end of this program, the memory location 2003H contains the number in decimal (base 10) form _______

Ques 19 Electrical Machines

A three-phase cylindrical rotor synchronous generator has a synchronous reactance X_S and a negligible armature resistance. The magnitude of per phase terminal voltage is V_A and the magnitude of per phase induced emf is E_A. Considering the following two statements, P and Q,
P: For any three-phase balanced leading load connected across the terminals of this synchronous generator, V_A is always more than E_A.
Q: For any three-phase balanced lagging load connected across the terminals of this synchronous generator, V_A is always less than E_A.
which of the following options is correct?

Ques 20 Electrical Machines

A three-phase, 50 Hz, 4-pole induction motor runs at no-load with a slip of 1%. With full load, the slip increases to 5%. The % speed regulation of the motor (rounded off to 2 decimal places) is ________.

Ques 21 Electrical Machines

A single-phase, 4 kVA, 200 V/100 V, 50 Hz transformer with laminated CRGO steel core has rated no-load loss of 450 W. When the high-voltage winding is excited with 160 V, 40 Hz sinusoidal ac supply, the no-load losses are found to be 320 W. When the high-voltage winding of the same transformer is supplied from a 100 V, 25 Hz sinusoidal ac source, the no-load losses will be _______ W (rounded off to 2 decimal places).

Ques 22 Electrical Machines

A 250 V de shunt motor has an armature resistance of 0.2 and a field resistance of 100 2. When the motor is operated on no-load at rated voltage, it draws an armature current of 5 A and runs at 1200 rpm. When a load is coupled to the motor, it draws total line current of 50 A at rated voltage, with a 5% reduction in the air-gap flux due to armature reaction. Voltage drop across the brushes can be taken as 1 V per brush under all operating conditions. The speed of the motor, in rpm, under this loaded condition, is closest to:

Ques 23 Electrical Machines

The figure below shows the per-phase Open Circuit Characteristics (measured in V) and Short Circuit Characteristics (measured in A) of a 14 kVA, 400 V, 50 Hz, 4-pole, 3-phase, delta connected alternator, driven at 1500 rpm. The field current, I_f is measured in A. Readings taken are marked as respective (x, y) coordinates in the figure.
Ratio of the unsaturated and saturated synchronous impedances (Z_s(unsat) / Z_s(sat)) of the alternator is closest to:

Ques 24 Electrical Machines

A cylindrical rotor synchronous generator with constant real power output and constant terminal voltage is supplying 100 A current to a 0.9 lagging power factor load. An ideal reactor is now connected in parallel with the load, as a result of which the total lagging reactive power requirement of the load is twice the previous value while the real power remains unchanged. The armature current is now _______ A (rounded off to 2 decimal places).

Ques 25 Electrical Machines

A cylindrical rotor synchronous generator has steady state synchronous reactance of 0.7 pu and subtransient reactance of 0.2 pu. It is operating at (1+j0) pu terminal voltage with an internal emf of (1+j0.7) pu. Following a three-phase solid short circuit fault at the terminal of the generator, the magnitude of the subtransient internal emf (rounded off to 2 decimal places) is _______ pu.

Ques 26 Electrical Machines

The figure shows a moving iron type meter. The coil has 100 turns and a length of 40 mm. The air gap is 1 mm on either side of the moving element. The flux density in the air gap is 0.2 T. Assume that the permeability of the moving iron element is infinite. The torque on the moving element is _______ x 10^-6 N-m (rounded off to 2 decimal places).