R13
Code: 13A02402
B.Tech III Year I Semester (R13) Regular Examinations December 2015
CONTROL SYSTEMS ENGINEERING
(Common to ECE and EIE)
(Use of ordinary graph sheets, semi log graphs and polar graphs are permitted in the examination hall)
Time: 3 hours
Max. Marks: 70
PART – A
(Compulsory Question)
1
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
*****
Answer the following: (10 X 02 = 20 Marks)
What is the effect of positive feedback on stability?
What are the differences between Synchro transmitter and control transformer?
The closed loop transfer function of a second order system is
. What is the type of
damping in the system?
Why derivative controller is not used alone in control systems?
What is the necessary and sufficient condition for stability in Routh’s stability criterion?
What is meant by damping pole in Root locus diagram?
Define Gain margin and Phase margin.
In minimum phase system, how the start and end of polar plot are identified?
State various properties of state transition matrix.
What are the advantages of state space analysis over transfer function analysis?
PART – B
(Answer all five units, 5 X 10 = 50 Marks)
UNIT – I
2
3
(a)
(b)
What is meant by open loop and closed loop control systems? Differentiate them.
Find the closed loop transfer function of the following block diagram using reduction technique.
(a)
(b)
OR
Define transfer function and also derive transfer function for AC Servo motor.
With the help of Mason’s gain formula find the overall transfer function of the following signal flow
graph.
Contd. in page 2
Page 1 of 2
R13
Code: 13A02402
UNIT – II
4
5
(a)
Obtain the response of a first order system
(b)
A closed loop servo is represented by the differential equation:
(a)
(b)
for unit step input.
. Where ‘c’ is the
displacement of the output shaft, ‘r’ is the displacement of the input shaft and e = r – c. Determine un
damped natural frequency, damping ratio and percentage maximum overshoot for unit step input.
OR
What is meant by transient response and steady state response? Explain in detail about various time
domain specifications.
Find the various static error constants for a unity feedback control system whose open loop transfer
function is:
.
UNIT – III
6
With the help of Routh’s stability criterion find the stability of the following systems represented by the
characteristic equations:
(i) s4 + 8s3 + 18s2 + 16s + 5 = 0.
(ii) s6 + 2s5 + 8s4 + 12s3 + 20s2 + 16s + 16 = 0.
(iii) s5 + s4 + 2s3 + 2s2 + 3s + 5 = 0.
OR
7
A negative feedback control system has the forward path transfer function:
.
Draw the root locus for 0 ≤ K ≤ ∞.
UNIT – IV
8
Sketch the bode plot for the following transfer function and determine phase margin and gain margin:
.
OR
9
The open loop transfer function of a unity feedback system is given by:
. Sketch the
polar plot and determine the gain margin and phase margin.
UNIT – V
10
(a)
Write the state variable formulation of the following parallel RLC network. The current through the
inductor and voltage across the capacitor are the output variables.
(b)
Compute the resolvent matrix and state transition matrix of the state matrix: A= 
0 1
.
 −1 −2 
OR
11
(a)
2
Obtain the state model of the transfer function: Y ( s ) = 3 s +23s + 4
U ( s ) s + 2s + 3s + 2
(b)
Diagonalize the system matrix,
.
*****
Page 2 of 2
R13
Code: 13A02501
B.Tech III Year I Semester (R13) Regular Examinations December 2015
ELECTRICAL MEASUREMENTS
(Electrical and Electronics Engineering)
Time: 3 hours
Max. Marks: 70
PART – A
(Compulsory Question)
*****
1
Answer the following: (10 X 02 = 20 Marks)
(a) What is ‘Swamping Resistance’? What is/are its characteristic(s)?
(b) What is the ratio of vertical to horizontal frequencies for an oscilloscope which displays the
following Lissajous figure?
(c) Frequency can be measured with which type of AC Bridge.
(d) How is the effect of Thermo-Electric EMFs eliminated when taking the readings with Kelvin’s
double bridge?
(e) What is Phantom loading? Why is it used?
(f) Write short notes on the shape of scale of an Electrodynamometer type wattmeter.
(g) Why should the secondary winding of a current transformer be never opened while its primary
winding is energized?
(h) Under what conditions, the phase angle error in potential transformers taken negative and under
what conditions it is taken as positive ?.
(i) What are Ballistic tests?
(j) List the three types of methods used for measurement of iron losses in ferromagnetic materials.
PART – B
(Answer all five units, 5 X 10 = 50 Marks)
UNIT – I
2
3
(a) What type of instrument is used for ‘AC measurements’ and what type of instruments is used for
DC measurements and what type of instrument is used as ‘transfer instrument’?
(b) The inductance of a moving iron ammeter with a full scale deflection of 900 at 1.5 A is given by the
expression
µH, where
is the deflection in radian from the zero
position. Estimate the angular deflection of the pointer for a current of 1.0 A
OR
Draw and explain the general block diagram of a Cathode Ray oscilloscope? How is frequency
measured in a cathode ray oscilloscope?
Contd. in page 2
Page 1 of 2
R13
Code: 13A02501
UNIT – II
4
5
(a) What type of bridge can be used for the measurement of dielectric of insulating oil used in
transformers? Justify.
(b) With a neat phasor diagram, explain how capacitance of an unknown capacitor can be determined
using Schering bridge.
OR
Identify and draw the phasor diagram of the bridge whose arms of a five node bridge are as
follows:
arm ab: an unknown impedance (R1, L1) in series with a non-inductive variable resistor r1,
arm bc: a non-inductive resistor R3 = 100 Ω ;
arm cd: a non-inductive resistor R4 = 200 Ω;
arm da a non-inductive resistor R2 = 250 Ω;
arm de: a non-inductive variable resistor r,
arm ec: a loss-less capacitor C = 1 uF, and arm be: a detector.
An AC supply is connected between a and c.
Also calculate the resistance and inductance R1, and L1. When under balance conditions
r1 = 43.1 Ω and r = 229.7 Ω?
UNIT – III
6
7
(a) Why is the measurement of power in circuits with low power factor by ordinary
electrodynamometer wattmeters is difficult and inaccurate? What special features are to be
incorporated in the above type of wattmeters to make it a ‘low power factor type wattmeter’?
(b) A 3-phase 500 V motor load has a power factor of 0.4. Two wattmeters are connected to measure
the input. They show the input to be 30 kW. Find the reading of each meter.
OR
With a neat sketch of phasor diagram, explain the construction and working principle of a single
phase Induction type energy meter.
UNIT – IV
8
9
What is the transformation ratio of a Current transformer? What are the causes of errors in current
transformers? Explain the design considerations that are to be taken to minimize those errors.
OR
(a) How is DC potentiometer used in the calibration of voltmeter and ammeter?
(b) How can AC potentiometer be used for the measurement of self reactance of a coil?
UNIT – V
10
11
Explain the use of Ballistic Galvanometer for the measurement of magnetic flux.
OR
How is Hysteresis loop determined by method of reversals?
*****
Page 2 of 2
R13
Code: 13A02502
B.Tech III Year I Semester (R13) Regular Examinations December 2015
ELECTRICAL POWER TRANSMISSION SYSTEMS
(Electrical and Electronics Engineering)
Max. Marks: 70
Time: 3 hours
1
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
PART – A
(Compulsory Question)
*****
Answer the following: (10 X 02 = 20 Marks)
Explain the effect of ground on capacitance.
Explain the significance of skin effect.
Define surge impedance loading and surge impedance.
Classify the types of transmission lines with an equivalent circuit.
Define string efficiency and explain its significance.
What is meant by sag template?
Explain about propagation of surges.
Explain reflection and refraction coefficients.
What is meant by grading? List out the types of grading.
List out the types of insulating materials.
PART – B
(Answer all five units, 5 X 10 = 50 Marks)
UNIT – I
2
(a)
(b)
3
(a)
(b)
What are bundled conductors? Why are they used?
Determine the capacitance per phase of a 3-phase, double circuit line, the conductors of which
are arranged in hexagonal spacing, the distance between conductors being 2.5 m. The diameter
of each conductor is 3 cm. Total length of line is 120 km.
OR
Derive an expression for the inductance per phase of a 3-phase unsymmetrical line.
A 1-phase line constructed 13.5 m above ground has spacing between the conductors 3.9 m. The
radius of the conductor is 1.78 cm. Determine the capacitance of the line per length, considering
the effect of earth and neglecting it.
UNIT – II
4
5
(a)
(b)
Explain the terms efficiency and regulation in relation to transmission lines.
A 3-phase, 50 Hz, 15 km transmission line supplying a total load of 850 kW at 0.8 p.f lagging and
11 kV has the following line constants: r = 0.45 ohms/km, x = 0.6 ohms/km. Calculate the line
current, receiving end voltage, voltage regulation and efficiency of transmission.
OR
Determine the A, B, C and D constants for a 3-phase, 50 Hz transmission line 250 km long
having the following distributed parameters: = 1.15 × 10-3 H/km, c = 7.8 × 10-9 F/km, r = 0.14
ohms/km, g = 0.
Contd. in page 2
Page 1 of 2
R13
Code: 13A02502
UNIT – III
6
(a)
(b)
7
(a)
(b)
Discuss the effect of both wind and ice on sag calculation.
A 3-phase, 50 Hz, 110 kV line with 1 cm diameter conductors are constructed so that corona
takes place if the line voltage exceeds 175 kV (rms). Determine the spacing between the
conductors. Assume smooth conductor. Air density factor = 1.0.
OR
What do you understand by grading of insulators? Explain.
A transmission line conductor weighing 0.85 kg/m is subjected to a wind pressure of 60 kg/m2 of
projected area. The conductor has ice coating of 1 cm thick. If the maximum permissible sag is
7.5 m, determine the permissible span between span two level supports. Take a factor of safety 2
and given that the density of ice is 915 kg/m2. Ultimate strength is 8000 kg and conductor
diameter 2 cm.
UNIT – IV
8
9
(a)
(b)
What is a Bewlwy-Lattice diagram? Explain its utility in the study of travelling waves.
Explain the nature of refracted components of voltage and current at the junction of two lines of
surge impedances Z1 and Z2.
OR
A 5 kV surge travels along a line of surge impedance 500 ohms.
(i) Find the magnitude of the incident current wave. The line is terminated by resistance of 800
ohms.
(ii) Find the rate of dissipation of energy and the values of reflected voltage and current waves.
(iii) What is the rate of energy reflection?
(iv) What should be the value of the terminating resistance so that energy in the wave is
completely dissipated, transmitted and reflected power?
UNIT – V
10
11
(a) Explain the constructional features of 3 core cables. Sketch a 3 core cable.
(b) In a 3-phase 3 core metal sheathed cables, the measured capacitance between any two cores is
2
Calculate the kilovolt amperes taken by cable when it is connected to 50 Hz, 11 kV bus bars.
OR
(a) Explain the theory of intersheath grading.
(b) A single core cable 1 km is length has a core diameter of 1.0 cm and a diameter under the sheath
of 2.5 cm. The relative permittivity is 3.5. The power factor on open circuit is 0.03. Calculate:
(i) The capacitance of the cable. (ii) Its equivalent insulation resistance. (iii) The charging current.
(iv) The dielectric loss when cable is connected to 6600 V, 50 Hz bus bars.
*****
Page 2 of 2
R13
Code: 13A02503
B.Tech III Year I Semester (R13) Regular Examinations December 2015
POWER ELECTRONICS
(Electrical and Electronics Engineering)
Time: 3 hours
1
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
Max. Marks: 70
PART – A
(Compulsory Question)
*****
Answer the following: (10 X 02 = 20 Marks)
What is difference between a Non-Punch through and Punch through IGBT?
What is the significance of turn-off gain of a GTO?
What is the purpose of inter-phase reactor in a three-phase line commutated converter?
A single phase full converter has a source voltage 230 V, 50 Hz. If the firing angle of the converter
is 600, what is its input power factor?
Input to the step up chopper is 200 V. The output required is 600 V. If the conducting time of
thyristor is 200 µsec. Compute chopping frequency.
What is the basic difference between time ratio control and current limit control of a chopper?
Why feedback diodes are used in bridge inverters?
A single phase half bridge inverter has dc input voltage 48 V. What is RMS value of output voltage?
The gate-cathode characteristics of a TRIAC are given by v g = 2 + 5i g . A triggering pulse train with
an amplitude of 10 V, ON period 10μs is applied to the gate through 10 Ω resistor. Calculate peak
gate power.
In which type of cycloconverters forced commutation is employed? Also give cycloconverter
applications.
PART – B
(Answer all five units, 5 X 10 = 50 Marks)
UNIT – I
2
3
Using two-transistor analogy, explain different turn on methods of SCR.
OR
A string of four series-connected thyristors is provided with static and dynamic equalizing circuits.
This string has to withstand an off state voltage of 10 kV. The static equalizing resistance is
25000 Ω and the dynamic equalizing circuit has RC = 40 Ω and C = 0.08 μF. The leakage currents
for four thyristors are 21 mA, 25 mA, 18 mA and 16 mA respectively. Determine voltage across
each SCR in the off-state and the discharge current of each capacitor at the time of turn-on.
Contd. in page 2
Page 1 of 2
R13
Code: 13A02503
UNIT – II
4
A 3-phase full converter charges a battery from a three phase supply of 230 V, 50 Hz. The battery
emf is 200 V and its internal resistance is 0.5 Ω. On account of inductance connected in series with
the battery, charging current is constant at 20 A. Compute the firing angle delay and the supply
power factor.
OR
The rectifier shown below has pure DC load current of 50 A and, Vs = 220 sin314t and unity
transformer ratio. if it is required to obtain an average output voltage of 70% of the maximum
possible output voltage, calculate:
5
(a)
(b)
(c)
(d)
(e)
The delay angle
The efficiency.
Ripple factor.
The peak inverse voltage (PIV) of the thyristor.
input displacement factor.
UNIT – III
A step down chopper feeding on RL load with input dc voltage of 200 V, with a load of R = 5 Ω,
L = 5 mH, switching frequency of 1 kHz and duty ratio of 0.5. Calculate: (i) Maximum and minimum
values of load current. (ii) Average value of load current. (iii) RMS load current. (iv) Effective input
resistance as seen by source. (v) RMS chopper current.
OR
With a neat circuit diagram and necessary waveforms, describe different modes of operation of a
voltage commutated chopper.
6
7
UNIT – IV
8
9
(a)
(b)
(c)
Explain the operation of a Series inverter with necessary circuit and waveforms.
OR
Single phase half bridge inverter has a resistive load of R = 3 Ω and dc input voltage Edc = 50 V,
calculate:
RMS output voltage at fundamental frequency.
The output power.
Average and peak current of each thyristor.
UNIT – V
10
11
With neat sketches explain different modes of operation of TRIAC.
OR
Describe the operation of a single phase bridge type cycloconverter with necessary circuit and
waveforms.
*****
Page 2 of 2
R13
Code: 13A02504
B.Tech III Year I Semester (R13) Regular Examinations December 2015
ELECTRICAL MACHINES – III
(Electrical and Electronics Engineering)
Time: 3 hours
Max. Marks: 70
PART – A
(Compulsory Question)
1
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
*****
Answer the following: (10 X 02 = 20 Marks)
What is breadth factor? Explain its effect on synchronous machine.
Draw and explain phasor diagram of cylindrical rotor alternator for lagging power factor.
Define voltage regulation and mention list of methods to find regulation of alternator.
What is meant by SCR? Explain its importance on performance of the machine.
Explain the effect of field current on performance of synchronous motor with variation of Ia and p.f.
Define synchronizing power and torque.
What is a synchronous condenser and write its applications?
What is hunting and list out its methods to eliminate hunting?
List out different starting methods of single phase induction motor.
Write down the types and applications of stepper motors.
PART – B
(Answer all five units, 5 X 10 = 50 Marks)
UNIT – I
2
3
(a) Derive an emf equation of an synchronous generator.
(b) Explain the effect of armature reaction on the operation of synchronous generator.
OR
(a) Explain the sources of harmonics. What are the various effects of harmonics on generated emf in
an alternator?
(b) An alternator is operating at no load has an induced EMF of 346.4 V/ph and a frequency of 60 Hz.
If the pole flux is decreased by 15% and the speed is increased by 6.8%. Determine:
(i) The induced EMF. (ii) Frequency.
UNIT – II
4
5
Describe the procedural steps to find regulation of an alternator using Z.P.F method.
OR
(a) Explain the two reaction theory of salient pole machine. Draw the phasor diagram and obtain
regulation of an alternator using this theory.
(b) Find the voltage regulation for a load of 1280 kW at 0.8 pf leading for a 3-phase 1600 kVA,
13500 V, star connected alternator having an armature resistance of 1.5 ohm per phase and a
synchronous reactance of 30 ohm/phase.
Contd. in page 2
Page 1 of 2
R13
Code: 13A02504
UNIT – III
6
7
(a) Two generators rated 420 MW and 580 MW are operating in parallel. The drop characteristics of
their governors are 3% and 4% respectively from no-load to full-load. If they are operating at 60 Hz
at no-load, how will they share 1000 MW load and what will be the system frequency?
(b) Give procedural steps to determine sub-transient, transient and steady state reactance of an
alternator.
OR
(a) Discuss the operation of synchronization of an alternator with an infinite bus
(b) A lighting load of 600 kW and a motor load of 707 kW at 0.707 p.f. are supplied by two alternators
running in parallel. One of the machines supplies 900 kW at 0.9 p.f. lagging. Find the load & p.f. of
the second machine.
UNIT – IV
8
9
(a) Explain the methods of starting the synchronous motor against the light loads and high load
torques.
(b) A 400 V synchronous motor gives a net output mechanical power of 7.35 kW and operates at 0.9
p.f lagging. Its effective resistance is 0.7 ohm. If the iron and mechanical losses are 550 W and
excitation losses are 750 W. Calculate armature current and commercial efficiency.
OR
(a) Explain bout the operation of synchronous induction motor.
(b) A3300 V delta connected synchronous motor has Xs = 18 ohms/phase. It operates at a leading
power factor of 0.707 when drawing 800 kW from mains. Find the excitation e.m.f.
UNIT – V
10
11
(a)
(b)
What is universal motor? Draw its phasor diagram and discuss its operation.
A universal motor has an inductance of 0.5H and a resistance of 30 ohms. When loaded and
connected to 250 V dc supply, it takes 0.8 A and runs at 2000 rpm. Find the speed when it’s
operating on 250 V, 50 Hz ac supply and drawing the same current.
OR
Draw the phasor diagram of an ac series motor. How can its performance be analyzed? Draw its
typical characteristics.
*****
Page 2 of 2
R13
Code: 13A52501
B.Tech III Year I Semester (R13) Regular Examinations December 2015
MANAGERIAL ECONOMICS & FINANCIAL ANALYSIS
(Common to CSE and EEE)
Time: 3 hours
Max. Marks: 70
PART – A
(Compulsory Question)
*****
1
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
Answer the following: (10 X 02 = 20 Marks)
What are Giffen goods?
Define Micro economics.
Distinguish between implicit and explicit cost.
What is margin of safety?
Define market skimming.
List the features of Oligopoly.
What are the current assets?
Write the features of capital budgeting.
Write about single entry book-keeping.
Define financial accounting.
PART – B
(Answer all five units, 5 X 10 = 50 Marks)
UNIT – I
2
3
Define elasticity of demand. List and explain different kinds of elasticity of demand.
OR
Define managerial economics. Explain its nature and scope.
UNIT – II
4
5
Define BEP. Explain how break-even analysis is used by the managers in their day-to-day operations.
OR
Critically evaluate the law of variable proportions with a neat diagram.
UNIT – III
6
7
Write brief note on: (i) Product differentiation. (ii) Market skimming.
(iii) Super normal profits. (iv) Shunt down price.
OR
Define economic liberalization. Discuss the impact of L.P.G polocy on Indian economy.
UNIT – IV
8
9
Define working capital. How do you estimate the fixed and working capital requirements of an industrial
unit?
OR
Consider the case of the following company M/S Venkata Ramana with the following two investment
alternatives each proposal of 6 lakhs. The details of cash inflows as follows:
Year
1
2
3
Proposal – I (Rs) 2,00,000 4,00,000 3,00,000
Proposal – II (Rs) 3,00,000 2,00,000 4,00,000
The cost of the capital is 12% factor per year. Which one you will choose: (i) NPV method. (ii) IRR
method.
UNIT – V
10
11
Give a brief account on the important records of accounting under Double-entry system of book keeping
and discuss briefly the scope of each.
OR
Explain the need to interpret financial statements in the context of profitability. What are the relevant
ratios?
*****