Electrical Engineering Gate 2016 Set-1 Questions with Answer

Ques 53 GATE 2016 SET-1


The voltage (vs) across and the current (is) through a semiconductor switch during a turn-ON transition are shown in figure. The energy dissipated during the turn-ON transition, in mJ, is ________.


(0.125) is the correct answer.

Ques 54 GATE 2016 SET-1


A single-phase full-bridge voltage source inverter (VSI) is fed from a 300 V battery. A pulse of 120° duration is used to trigger the appropriate devices in each half-cycle. The rms value of the fundamental component of the output voltage, in volts, is

A

234

B

245

C

300

D

331


(a) is the correct answer.

Ques 55 GATE 2016 SET-1


In a 100 bus power system, there are 10 generators. In a particular iteration of Newton Raphson load flow technique (in polar coordinates), two of the PV buses are converted to PQ type. In this iteration,

A

the number of unknown voltage angles increases by two and the number of unknown voltage magnitudes increases by two.

B

the number of unknown voltage angles remains unchanged and the number of unknown voltage magnitudes increases by two.

C

the number of unknown voltage angles increases by two and the number of unknown voltage magnitudes decreases by two.

D

the number of unknown voltage angles remains unchanged and the number of unknown voltage magnitudes decreases by two.


(b) is the correct answer.

Ques 56 GATE 2016 SET-1


The magnitude of three-phase fault currents at buses A and B of a power system are 10 pu and 8 pu, respectively. Neglect all resistances in the system and consider the pre-fault system to be unloaded. The pre-fault voltage at all buses in the system is 1.0 pu. The voltage magnitude at bus B during a three-phase fault at bus A is 0.8 pu. The voltage magnitude at bus A during a three-phase fault at bus B, in pu, is ________.


(0.84) is the correct answer.

Ques 57 GATE 2016 SET-1


Consider a system consisting of a synchronous generator working at a lagging power factor, a synchronous motor working at an overexcited condition and a directly grid-connected induction generator. Consider capacitive VAr to be a source and inductive VAr to be a sink of reactive power. Which one of the following statements is TRUE?

A

Synchronous motor and synchronous generator are sources and induction generator is a sink of reactive power.

B

Synchronous motor and induction generator are sources and synchronous generator is a sink of reactive power.

C

Synchronous motor is a source and induction generator and synchronous generator are sinks of reactive power.

D

All are sources of reactive power.


(c) is the correct answer.

Ques 58 GATE 2016 SET-1


A three-phase cable is supplying 800 kW and 600 kVAr to an inductive load. It is intended to supply an additional resistive load of 100 kW through the same cable without increasing the heat dissipation in the cable, by providing a three-phase bank of capacitors connected in star across the load. Given the line voltage is 3.3 kV, 50 Hz, the capacitance per phase of the bank, expressed in microfarads, is ________.


(47.96) is the correct answer.

Ques 59 GATE 2016 SET-1


A 30 MVA, 3-phase, 50 Hz, 13.8 kV, star-connected synchronous generator has positive, negative and zero sequence reactances, 15%, 15% and 5% respectively. A reactance (Xn) is connected between the neutral of the generator and ground. A double line to ground fault takes place involving phases 'b' and 'c', with a fault impedance of j0.1 p.u. The value of Xn (in p.u.) that will limit the positive sequence generator current to 4270 A is ________.


(0.33) is the correct answer.

Ques 60 GATE 2016 SET-1


If the star side of the star-delta transformer shown in the figure is excited by a negative sequence voltage, then

A

VAB leads Vab by 60°

B

VAB lags Vab by 60°

C

VAB leads Vab by 30°

D

VAB lags Vab by 30°


(d) is the correct answer.

Ques 61 GATE 2016 SET-1


A single-phase transmission line has two conductors each of 10 mm radius. These are fixed at a center-to-center distance of 1 m in a horizontal plane. This is now converted to a three-phase transmission line by introducing a third conductor of the same radius. This conductor is fixed at an equal distance D from the two single-phase conductors. The three-phase line is fully transposed. The positive sequence inductance per phase of the three-phase system is to be 5% more than that of the inductance per conductor of the single-phase system. The distance D, in meters, is ________.


(1.427) is the correct answer.

Ques 62 GATE 2016 SET-1


Consider a continuous-time system with input x(t) and output y(t) given by y(t) = x(t)cos(t). This system is

A

linear and time-invariant

B

non-linear and time-invariant

C

linear and time-varying

D

non-linear and time-varying


(c) is the correct answer.

Ques 63 GATE 2016 SET-1


The value of ∫-∞+∞ e-tδ(2t-2) dt, where δ(t) is the Dirac delta function, is

A

1/(2e)

B

2/e

C

1/e2

D

1/(2e2)


(a) is the correct answer.

Ques 64 GATE 2016 SET-1


Suppose x1(t) and x2(t) have the Fourier transforms as shown below.

Which one of the following statements is TRUE?

A

x1(t) and x2(t) are complex and x1(t)x2(t) is also complex with nonzero imaginary part

B

x1(t) and x2(t) are real and x1(t)x2(t) is also real

C

x1(t) and x2(t) are complex but x1(t)x2(t) is real

D

x1(t) and x2(t) are imaginary but x1(t)x2(t) is real


(b) is the correct answer.

Ques 65 GATE 2016 SET-1


The output of a continuous-time, linear time-invariant system is denoted by T{x(t)} where x(t) is the input signal. A signal z(t) is called eigen-signal of the system T, when T{z(t)} = γz(t), where γ is a complex number, in general, and is called an eigenvalue of T. Suppose the impulse response of the system T is real and even. Which of the following statements is TRUE?

A

cos(t) is an eigen-signal but sin(t) is not

B

cos(t) and sin(t) are both eigen-signals but with different eigenvalues

C

sin(t) is an eigen-signal but cos(t) is not

D

cos(t) and sin(t) are both eigen-signals with identical eigenvalues


(d) is the correct answer.

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