Electrical Engineering GATE 2018 Questions with Answer

Ques 53 Power Electronics

A dc to dc converter shown in the figure is charging 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. [cite: 112, 113] 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).

Ques 54 Power System

In the figure, the voltages are 𝑣₁(𝑡) = 100cos(𝜔𝑡), 𝑣₂(𝑡) = 100cos(𝜔𝑡 + 𝜋/18) and 𝑣₃(𝑡) = 100cos(𝜔𝑡 + 𝜋/36). The circuit is in sinusoidal steady state, and 𝑅 << 𝜔𝐿. 𝑃₁, 𝑃₂ and 𝑃₃ are the average power outputs. Which one of the following statements is true?

Ques 55 Power Systems

Consider a lossy transmission line with V₁ and V₂ as the sending and receiving end voltages, respectively. Z and X are the series impedance and reactance of the line, respectively. The steady-state stability limit for the transmission line will be

Ques 56 Power Systems

The series impedance matrix of a short three-phase transmission line in phase coordinates is If the positive sequence impedance is (1+j10) Ω, and the zero sequence is (4+j31) Ω, then the imaginary part of Z_m(in Ω) is ________ (up to 2 decimal places).

Ques 57 Power Systems

The positive, negative and zero sequence impedances of a 125 MVA, three-phase, 15.5 kV, star-grounded, 50 Hz generator are j0.1 pu, j0.05 pu and j0.01 pu respectively on the machine rating base. The machine is unloaded and working at the rated terminal voltage. If the grounding impedance of the generator is j0.01 pu, then the magnitude of fault current for a b-phase to ground fault (in kA) is ________ (up to 2 decimal places).

Ques 58 Power Systems

A 1000×1000 bus admittance matrix for an electric power system has 8000 non-zero elements. The minimum number of branches (transmission lines and transformers) in this system are ________ (up to 2 decimal places).

Ques 59 Power Systems

The positive, negative and zero sequence impedances of a three phase generator are Z₁, Z₂, and Z₀ respectively. For a line-to-line fault with fault impedance Z_f, the fault current is I_f1 = kI_f, where I_f is the fault current with zero fault impedance. The relation between Z_f and k is

Ques 60 Power Systems

Consider the two bus power system network with given loads as shown in the figure. All the values shown in the figure are in per unit. The reactive power supplied by generator _G1 and _G2 are Q_G1 and Q_G2 respectively. The per unit values of Q_G1, Q_G2 and line reactive power loss Q_loss respectively are:

Ques 61 Power Systems

The per-unit power output of a salient-pole generator which is connected to an infinite bus, is given by the expression: P = 1.4 sin(δ) + 0.15 sin(2δ), where δ is the load angle. Newton-Raphson method is used to calculate the value of δ for P = 0.8 pu. If the initial guess is 30°, then its value (in degree) at the end of the first iteration is:

Ques 62 Signals and Systems

A continuous-time input signal x(t) is an eigenfunction of an LTI system, if the output is

Ques 63 Signals and Systems

Consider the two continuous-time signals defined below:

Ques 64 Signals and Systems

The signal energy of the continuous-time signal x(t)=[(t−1)u(t−1)]−[(t−2)u(t−2)]−[(t−3)u(t−3)]+[(t−4)u(t−4)] is

Ques 65 Signals and Systems

The Fourier transform of a continuous-time signal x(t) is given by: X(ω) = ½(1 + jω), -∞ < ω < ∞, where j = √-1 and ω denotes frequency. Then the value of | ln(xt) | at t =1 is ___________ (up to 1 decimal place). (ln denotes the logarithm to base e)