JNTU
JNTU B.Tech II PRINCIPLES OF ELECTRICAL ENGINEERING Previous Question Paper (May - 2019 - R13)
Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks.
PART A
Give the solution for instantaneous current i(t) in a simple RL circuit without source. Take initial conditions i(0)=I0. Draw the response graph indicating the factors effecting the rate of decay.
Answer
For a source-free RL circuit, the governing differential equation is L(di/dt) + Ri = 0. Solving this with the initial condition i(0) = I0 yields the instantaneous current: i(t) = I0e-(R/L)t. The response is an exponential decay curve starting at I0, where the time constant τ = L/R determines the rate of decay; a smaller τ leads to a faster decay.
Find the Laplace transform of {e-2t sin(5t + 0.2π)}.
Answer
Using the identity sin(A+B) = sin A cos B + cos A sin B, sin(5t + 0.2π) = sin(5t)cos(0.2π) + cos(5t)sin(0.2π). Applying the Laplace transform L{e-atf(t)} = F(s+a), we get: L{e-2t(sin 5t cos 0.2π + cos 5t sin 0.2π)} = cos(0.2π) * [5 / ((s+2)2 + 25)] + sin(0.2π) * [(s+2) / ((s+2)2 + 25)].
Define input impedance of a one-port network. Give the formula to determine it.
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Define short circuit admittance parameters of a two-port network.
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Give the classification of filters.
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Draw the circuit diagram of π type attenuator.
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Give the EMF equation of a DC generator and explain the factors effecting it.
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List out various losses in DC machine and give the factors effecting them.
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Define Regulation of a transformer. Give the general expression for it.
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Give the applications of Stepper motors.
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PART B
For the network shown in figure 1, the switch is closed at t=0. Determine the current i(t) using solution to differential equations.
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Find i(t) if switch K is closed at t=0 as shown in figure 2.
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Determine the z-parameters of given network as shown in Figure 3.
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Write the standard Y-parameter equations. Obtain the Y-parameters in terms of Z-parameters.
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Obtain Z-parameters for the circuit shown in figure 4 and there by obtain ABCD parameters.
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What is the difference between constant-k and m-derived filters?
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Design a constant-k type band-pass filter π section to be terminated in 600Ω resistance having cut-off frequencies of 2 kHz and 5 kHz.
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Distinguish between Band Pass filter and Band Elimination filter with a suitable example.
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Explain the design procedure of constant K low pass filter.
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Explain the basic principle of operation of DC generator with the help of neat sketches.
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Explain the armature resistance and field control methods of speed control of DC shunt motor.
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Explain the different types of DC generators with the help of circuit diagrams.
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Give the procedure to determine the efficiency of DC machine using Swinburne’s Test. Draw the experimental circuit diagram.
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Give the constructional details of single-phase transformer with help of neat sketches.
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Develop an equivalent circuit of a single phase transformer from fundamentals.
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Explain the principle of operation of single phase transformer and draw the phasor diagram for no-load and on-load operating conditions.
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A 300kVA, 11kV/ 440V, single phase, 50Hz, transformer gave the following test results. Open circuit test on LV side with a normal voltage and frequency, input 1.3 kW, 4A; short circuit test HV side with voltage 600V, input 2.80kW, 15A. Calculate the efficiency and regulation for full load at 0.8 p.f. lagging.
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