JPSC Assistant Engineer 2021: Assistant Engineer Written Exam, Advt. No. 08/2018 and 08/2019, ELECTRICAL ENGINEERING PAPER-II SUBJECT-CODE-13
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AEUD
ELECTRICAL ENGINEHRING
PAPER - 11
SUBJFCT CODE : 13
Full Marks : 200 Time : 3 Hours
Iiestructious For Candidates :
Please read each Of the following iustructious caref ally bef lore attempting questions.
(1) Ariswers must be written in ENGLISH only.
(2) The question paper contains a total Of 8 questions in TWO Sections : Section-A
and Section-B. aTOUR questions in each section)
(3) Question No.1 Of section `A' and Question No. 5 Of section `B' are compulsop=
(4) Candidates have to attempt another THpeE qu_esttous from remaining SIX
questions choosing atleast ONE question from each section.
(5) Assume suitable data if f ;ound necessary.
(6) Wherever any assumption be pnde for answering a question, they must be
clearly indicated.
q) Marks carried by a question / section is indicated against it.
(8) Unless struck of f ; attempt of question shall be counted even if attempted partly.
(9) Any page or portion of the page lef i blank in the Answer Booklet must be clearly
struckoff
SECTION - A
Marks
5 x 8 - 40
1. (i) Derive the expression for saving in copper for an autotransformer as compared
to a conventional two winding transformer.
(ii) A 2-pole, 50-MVA,11 KV generator is supplying full load power at 0.8 p.f.
lagging.Iftheinertiacoustautofthemovingpartofthegeneratoris6MJ/MVA,
calculate the energy stored when the generator is running at the synchronous
speed of 3000 rpm. If the net input of the generator is suddenly increased to
62000 metric IIT, calculate the acceleration produced
(iii) Explain Impulse function and impulse response function.
(iv) Briefly discuss the Full - Adder with its truth table and logic diagram.
AEUD (13) Paper-II
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Marks
(v) Calculate the signal energy for the given signal. Also calculate the signal power.
a;(t) - e4t.u(t)
1 fiort=0
where u(t) =
0 fort=0
2. (a) Discuss the applications of different types ofD.C. motor with the field of speed
v/s armature current and torque v/s armature current characteristics. 20
a) A 1500 KVA, 6.6 KV, 3-a star cormected alternator has effective armature
resistance of 0.5 a/phase and synchronous reactance of 5 a/phase. Find the
percentage change in teminal voltage at
(i) unityp.f.
(ii) 0.8 laggingp.f.
(iii) 0.8 leadingp.f.
The speed and excitation current remains unchanged. 20
(a) Explain the different factors for the site selection of Hydro-power plant. Also
draw and explain its layout.
qJ) For the system shown in fiT#: 1, where a 3-ffault occur at point p.
Figure - 1
Find the critical clearing angle for clearing the fault with simultaneous opening
of the breaker 1 and breaker 2. The reactance value of various components are
indicated in the figure 1. The generator is delivering I.0 PU power at the instant
preceding the fault.
(a) For the load - fi.equency control of a single area system ; derive the speed
governing system model, turbine model and generator load model. Also draw its
complete block diagram. 20
a) A 440 V, 6-pole, 50 Hz, 3-phase delta comected induction motor rmning on full
load develops a usefu torque of 160 Nm when the rotor emf makes 120
complete cycle / min. Deteine the shaft power output. If the mechanical
torque lost in friction and core loss is 10 Nm, estimate :
(i) Copperloss inrotorwindings
(ii) Inputto themotor
(iii) Efficiency
The total stator loss is 1 KW. 20
AEUD (13) Paper-H
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Marks
SECTION-B 5 x 8 =40
(i) Draw and explain the torque speed characteristics ofa single phase induedon
motor based on revolving field theory.
(ii) In a power system the full input per-hour of plants 1 and 2 are given as :
F, = 0.20 P[2 + 30P, + 100 { perhour
F2 = 0.25 P22 + 40P2 + 150 i per hour
The linits of generator are
20 S P, i 80 MW
40 S P2 S 200 MW
Find the economic operating schedule of generation, if the load demand is 130
MW. Negleet transmission losses.
(iii) Discuss the co-relations between time domain and frequency domain parameters.
(iv) An AM broadcast station transmits a total power of 50 KW when the carrier is
modulated by a sinusoidal signal with a modulation index of 0.707, calculate :
(a) the carrierpower
a) the transmission efficiency, and
(c) the peak amplitude of the carrier assuming the antenna to be represented
by a (50 +jo) a load.
(v) Realize AND, OR, NOT logic gates, using universal gates.
(a) Discuss the advantages and drawbacks of closed loop control system.
a)) Derive the unit step response of a standard 2ad order system for underdamped
case and discuss it.
(c) Obtain the time response of the system described by the state equation and
output equation as
i(t,-[-ol-12]X(t,+[:]u,t,
andy(t)-[1 0]x(t)
with x(0) - and u(t) = 1 for t > 0 20
7. (a) Derive expression for the sigrial v3(t) in the figure 2 given below for
v](t) = 10 cos (2000 n t) + 4 sin (200 tt t). Assume that v2(t) = v[(t) + 0.1 v[2(t) and
that the BPF is an ideal unity gain filter with pass band from 800 Hz to 1200 Hz.
Non-linear System
y2(t)
Figure-2
AEUD (13) Paper-H
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a) For a system the impulse response h(t) is given as
h{t) = e-t u(t) + e2t u(_t)
The system is excited by
J:(t) - e-2t u(t)
20
Find the output y(t) for this system.
20
8. (a) Minimize the combinational logic circuit as shown in figure 3.
Figure - 3
a) Design a counter with the irregular binary count sequence shown in the state
20
diagram of figure 4 using J-K flip - flop.
Paper-II
iREUD (13)Official key not published for this paper.
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Source: Jharkhand Public Service Commission. Question paper published by Jharkhand Public Service Commission.