Transco Papers 123

8/19/2019 Transco Papers 123

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2013-06-20

APTRANSCO 2012 ELECTRICAL Previous Paper APTRANSCO 2012 KEY ELECTRICAL

1.

1. A voltage waveform v(t)= 12 t2 is applied across a 1H inductor for t>=0 withinitial current through it being zero. The current through the inductor fort>=0 is given by-----------(4t3)

2. Two incandescent light bulbs fo 40w and 60w ratingare connected in series across the mains. Then--------(the 40 bulb glows brighter)

3. Given two coupled inductors L1 and L2, their mutualinductances M satisfies-----(M

4. Consider the star network. The resistance betweenterminals A and B with C open 6ohms, between terminals B and C with A open is11ohms, and between terminals C and A with B open is 9ohms. Then------------(Ra=2, Rb=4, Rc=7)

5. In a series RLC circuit at resonance, the magnitudeof the voltage developed across the capacitor------( can be greater than theinput voltage, however, it is 900 out of phase with the input voltage)

6. A two port device is defined by the following pairof quations:

i1=2v1+v2 and i2=v1+v2 its impedance parameters(z11, z12, z21, z22) are-----(1,-1,-1,2)

7. The impulse response of an initially relaxed linearsystem is e-2tu(t).to produce a response of

te-2tu(t), the input must be equalto--------(e-2t u(t))

8. The no of roots on the equation 2s4+s3+3s2+5s+7=0

that lie in the right half of s plane is-------(2)

9. For a feedback control system of type 2, the steadystate error for a ramp input is-------(zero)

10. The output of a linear time invariant controlsystem is c(t) for a certain input r(t). if r(t) is modified by passing itthrough a block whose transfer function is e-s and then applied to the system,the modified output of the system would be-----------(c(t-1)u(t-1)

11. The phase lead compensation used to-----(decreases

both rise time and overshoot)

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12. Consider two buses connected by an impedance of(0+j5)ohm. The bus 1 voltage is 100/300 v, and bus 2 voltage is 100/00 v. the real andreactive power supplied by bus 1,resp are……….(1000w, 268 VAr)

13. For a fixed value of complex power flow in atransmission line having a sending end voltage V, the real power loss will beproportional to-----------(1/V2).

14. During a disturbance on a synchronous machine, therotor swings from A to B before finally settling down to a steady state atpoint C on the power angle curve. The speed of the machine during oscillationis synchronous at point(s)--------------------(A and B)

15. A 100 MVA, 11kv, 3 phase 50hz, 8 pole synchronousgenerator has an inertia constant H equal to 4 MJ/MVA. The stored energy in the

rotor of the generator at synchronous speed will be---(400MJ).

16. In a biased differential relay the bias is definedas a ratio of----------(operating coil current and restraining coil current))

17. Resistance switching is normally employedin------(ABCB)

18. The use of high speed circuit breakers----(improvessystem stability)

19. Keeping in view the cost and overall effectiveness,the following circuit breaker is best suited for capacitor bankswitching---(vacuum)

20. If the reference bus is changed in two load flowruns with the same system data and power obtained for reference bus taken asspecified P and Q in the latter run----------( the system losses will beunchanged but complex bus voltages will change.)

21. The gauss seidel load flow method has followingdisadvantages. Tick the incorrect statement------( unreliable convergence)

22. The torque speed characteristics of a repulsionmotor resembles which of the following dc motorcharacteristic------------(series)

23. Which type of motor is most suitable for computerprinter drive-----(stepper motor)

24. A 4 pole lap wound DC generator has a developedpower of P watts and voltage of E volts. Two adjacent brushes of the machineare removed as they are worn out. If the machine operates with the remaining

brushes, the developed voltage and power that can be obtained from the machineare----(E,P/4)


3/60

25. A 4 point starter is used to start and control thespeed of a -----------( dc shunt motor with field weakening control)

26. The function of oil in a transformer is-----( to

provide insulation and cooling)

27. The core flux of a practical transformer with aresistive load------------( is strictly constant with load changes)

28. In a transformer zero voltage regulation at fullload is----(possible at leading pf load)

29. A single phase transformer has a turns ratio of1:2, and is connected to a purely resistive load. The magnetizing current drawnis 1 A, and the secondary current is 1A. if core losses and leakage reactance

are neglected, the primary current is-(2.24A)

30. The low voltage winding of a 400/230V, single phase50hz transformer is to be connected to a 25hz, the supply voltage should be-------(115V)

31. A 400/100V, 10 KVA two winding transformer isreconnected as an auto transformer is reconnected as an auto transformer acrossa suitable voltage source. The maximum rating of such an arrangement could be-----(50KVA)

32. When the supply voltage to an induction motor isreduced by 10%, the maximum torque will decrease by approximately-------(20%)

33. In case of a split phase motor, the phase shift between currents in the two windings is around------(300)

34. Starting torque can be obtained in the case of asingle phase induction motor with identical main and auxiliary windings byconnecting-----( a capacitor in series with the auxiliary winding)

35. For a single phase capacitor start induction motor

which of the following statements is valid---( the direction of rotation can bechanged by reversing the main winding terminals)

36. An induction motor having full load torque of 60zNm when delta connected develops a starting torque of 120Nm. For the same supply voltage, if the motor is changed to star-connection, the starting torquedeveloped will be-------(40NM)

37. During hunting of synchronous motor –(damper bardevelops torque)

38. The phase sequence of a three phase alternator willreverse if -------(the field current remains the same but the direction of


4/60

rotation is reversed)

39. The effect of stray magnetic fields on theactuating torque of a portable instrument is max when the operating filed ofthe instrument and the stray fields are-(parallel)

40. A current of -8+6

(sinwt+300)A is passed through threemeters. They are a center zero PMMC meter, true rms meter and MI instrument.The respective reading( in A) will be----(-8,10,10)

41. R1 and R2 are the opposite arms of a wheatstone bridge as are R3 and R, the source voltage is applied across R1 and R3 under balanced conditions which one of the following is true---(R1=R2R3/R4)

42. A dc potentiometer is designed to measure up toabout 2v with a slide wire of 800mm. a standard cell of emf 1.18v obtains balance at 6010mm. a test cell is seen to obtain balance at 680mm. the emf ofthe test cell is-(1.34v)

43. The minimum number of wattmeters required tomeasure3 phase 3 wire or unbalanced power is—(2)

44. A reading of 120 is obtained when a standardinductor was connected in the circuit of a Q meter and the variable capacitoris adjusted to a value of 300pF. A lossless capacitor of unknown value C, is

then connected and the same reading was obtained when the variable capacitor isreadjusted to a value of 200pF. The value of Cx in pF is—(100)

45. The two inputs of a CRO are fed with the twostationary periodic signals. In the X Y mode, the screen shows a figure whichchanges from ellipse to circle and back to ellipse with its major axis changingorientation slowly and repeatedly. The following inference can be made fromthis----------(there is a constant but small phase difference between thesignals)

46. SCR can be turned off —( anode current should be

less than holding current)

47. The no. of pn junctions in SCR-----(3)

48. TRIAC is a—(antiparallel thyristors combination)

49. GTO can be turned off-(by using a negative currentpulse)

50. Which type of control is used for controlling theac drive by using thyristors--------(integral cycle)

51. In DC choppers the output voltage can be controlled


5/60

by using FM technique varying--------( T , Toff constant)

52. In phase control rectifiers the output voltageripple can be controlled by —‘(load inductance)

53. Which is not a current controlleddevice-----(MOSFET)

54. Inverter function---------(DC to AC with variablefrequency)

55. In phase controlled rectifires free wheeling diodemakes-(load current continuation)

56. Dielectric heating application----(wood)

57. In induction heating the following is abnormallyhigh--------(frequency)

58. Tractive effect w.r.t driving wheelaxis--------(tangential*)

59. welding transformer sets have-------------(highcurrent, low voltage)

60. Simplifyx’y’z+x’yz’+xy’z+xyz+xyz’=-------(y’z+yz’+xz)

61. Find out y=-----------------(P+Q+R+S)

OTHER PAPERS

AP TRANSCOELECTRICAL - TECHNICAL PAPER

SUB-ENGINEERSTECHNICAL PAPER 2012

ENGINEERSTECHNICAL PAPER 2012

ELECTRICALPAPER -SOME IMPORTANT QUESTIONS

AP GENCO -TECHNICAL PAPER

TECHNICALPAPER 2012

TECHNICAL


6/60

PAPER 2011

AP CPDCLELECTRICAL - TECHNICAL PAPER

TECHNICALPAPER 2010

BHEL ELECTRICAL- - TECHNICAL PAPER

TEHNICALPAPER 2010

TEHNICALPAPER 2009

2013-06-20

APTRANSCO 2012 ELECTRICAL Previous Paper APTRANSCO 2012 KEY ELECTRICAL

1.

1. A voltage waveform v(t)= 12 t2 is applied across a 1H inductor for t>=0 with

initial current through it being zero. The current through the inductor for

t>=0 is given by-----------(4t3)

2. Two incandescent light bulbs fo 40w and 60w rating

are connected in series across the mains. Then--------(the 40 bulb glows brighter)

3. Given two coupled inductors L1 and L2, their mutual

inductances M satisfies-----(M

4. Consider the star network. The resistance between

terminals A and B with C open 6ohms, between terminals B and C with A open is

11ohms, and between terminals C and A with B open is 9ohms. Then

------------(Ra=2, Rb=4, Rc=7)

5. In a series RLC circuit at resonance, the magnitude

of the voltage developed across the capacitor------( can be greater than the

input voltage, however, it is 900 out of phase with the input voltage)

6. A two port device is defined by the following pair

of quations:

i1=2v1+v2 and i2=v1+v2 its impedance parameters

(z11, z12, z21, z22) are-----(1,-1,-1,2)

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7/60

7. The impulse response of an initially relaxed linear

system is e-2tu(t).to produce a response of

te-2tu(t), the input must be equal

to--------(e-2t u(t))



9. For a feedback control system of type 2, the steady

state error for a ramp input is-------(zero)

10. The output of a linear time invariant control

system is c(t) for a certain input r(t). if r(t) is modified by passing it

through a block whose transfer function is e-s and then applied to the system,

the modified output of the system would be-----------(c(t-1)u(t-1)



12. Consider two buses connected by an impedance of

(0+j5)ohm. The bus 1 voltage is 100/300 v, and bus 2 voltage is 100/00 v. the real and reactive

power supplied by bus 1,

resp are……….(1000w, 268 VAr)

13. For a fixed value of complex power flow in a

transmission line having a sending end voltage V, the real power loss will beproportional to-----------(1/V2).

14. During a disturbance on a synchronous machine, the

rotor swings from A to B before finally settling down to a steady state at

point C on the power angle curve. The speed of the machine during oscillation

is synchronous at point(s)--------------------(A and B)

15. A 100 MVA, 11kv, 3 phase 50hz, 8 pole synchronous

generator has an inertia constant H equal to 4 MJ/MVA. The stored energy in the


16. In a biased differential relay the bias is defined

as a ratio of----------(operating coil current and restraining coil current))

17. Resistance switching is normally employed

in------(ABCB)

18. The use of high speed circuit breakers----(improves

system stability)

19. Keeping in view the cost and overall effectiveness,the following circuit breaker is best suited for capacitor bank


8/60

switching---(vacuum)

20. If the reference bus is changed in two load flow

runs with the same system data and power obtained for reference bus taken as

specified P and Q in the latter run----------( the system losses will be

unchanged but complex bus voltages will change.)

21. The gauss seidel load flow method has following

disadvantages. Tick the incorrect statement------( unreliable convergence)

22. The torque speed characteristics of a repulsion

motor resembles which of the following dc motor

characteristic------------(series)

23. Which type of motor is most suitable for computer

printer drive-----(stepper motor)

24. A 4 pole lap wound DC generator has a developed

power of P watts and voltage of E volts. Two adjacent brushes of the machine

are removed as they are worn out. If the machine operates with the remaining

brushes, the developed voltage and power that can be obtained from the machine

are----(E,P/4)

25. A 4 point starter is used to start and control the

speed of a -----------( dc shunt motor with field weakening control)

26. The function of oil in a transformer is-----( toprovide insulation and cooling)

27. The core flux of a practical transformer with a

resistive load------------( is strictly constant with load changes)

28. In a transformer zero voltage regulation at full

load is----(possible at leading pf load)

29. A single phase transformer has a turns ratio of

1:2, and is connected to a purely resistive load. The magnetizing current drawn

is 1 A, and the secondary current is 1A. if core losses and leakage reactance


30. The low voltage winding of a 400/230V, single phase

50hz transformer is to be connected to a 25hz, the supply voltage should

be-------(115V)

31. A 400/100V, 10 KVA two winding transformer is

reconnected as an auto transformer is reconnected as an auto transformer across

a suitable voltage source. The maximum rating of such an arrangement could

be-----(50KVA)


9/60

32. When the supply voltage to an induction motor is

reduced by 10%, the maximum torque will decrease by approximately-------(20%)

33. In case of a split phase motor, the phase shift

between currents in the two windings is around------(300)

34. Starting torque can be obtained in the case of a

single phase induction motor with identical main and auxiliary windings by

connecting-----( a capacitor in series with the auxiliary winding)


which of the following statements is valid---( the direction of rotation can be

changed by reversing the main winding terminals)

36. An induction motor having full load torque of 60zNm

when delta connected develops a starting torque of 120Nm. For the same supply

voltage, if the motor is changed to star-connection, the starting torque

developed will be-------(40NM)

37. During hunting of synchronous motor –(damper bar

develops torque)

38. The phase sequence of a three phase alternator will

reverse if -------(the field current remains the same but the direction of


39. The effect of stray magnetic fields on theactuating torque of a portable instrument is max when the operating filed of

the instrument and the stray fields are-(parallel)


(sinwt+300)A is passed through three

meters. They are a center zero PMMC meter, true rms meter and MI instrument.

The respective reading( in A) will be----(-8,10,10)

41. R1 and R2 are the opposite arms of a wheatstone

bridge as are R3 and R, the source voltage is applied across R1 and R3 under

balanced conditions which one of the following is true---(R1=R2R3/R4)

42. A dc potentiometer is designed to measure up to

about 2v with a slide wire of 800mm. a standard cell of emf 1.18v obtains

balance at 6010mm. a test cell is seen to obtain balance at 680mm. the emf of

the test cell is-(1.34v)

43. The minimum number of wattmeters required to

measure3 phase 3 wire or unbalanced power is—(2)

44. A reading of 120 is obtained when a standard


10/60


11/60

current, low voltage)

60. Simplify

x’y’z+x’yz’+xy’z+xyz+xyz’=-------(y’z+yz’+xz)

61. Find out y=-----------------(P+Q+R+S)

OTHER PAPERS

AP TRANSCO

ELECTRICAL - TECHNICAL PAPER

SUB-ENGINEERS

TECHNICAL PAPER 2012

ENGINEERS


ELECTRICAL

PAPER -SOME IMPORTANT QUESTIONS

AP GENCO -

TECHNICAL PAPER

TECHNICAL

PAPER 2012

TECHNICAL

PAPER 2011

AP CPDCL

ELECTRICAL - TECHNICAL PAPER

TECHNICAL

PAPER 2010

BHEL ELECTRICAL

- - TECHNICAL PAPER

TEHNICAL

PAPER 2010

TEHNICAL

PAPER 2009


12/60

1. In a dc shunt motor the terminal voltage is halved while the torque is kept

constant. The resulting approximate variation in speed ” ω” and armature

current “Ia„” will be

(A) Both ω and Iaare doubled.

(B) ω is constant and Ia is doubled

(C) w is doubled while Ia is halved

(D) w is constant but Ia is halved

Ans: B

2.The current from the stator of an alternator is taken out to the external load

circuit through

(A) slip rings.

(B) commutator segments.

(C) solid connections.

(D) carbon brushes.

Ans: C

3.A motor which can conveniently be operated at lagging as well as leading

power factors is the

(A) squirrel cage induction motor.

(B) wound rotor induction motor.

(C) synchronous motor.

(D) DC shunt motor.

Ans: C

4 The frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction

motor at full load speed is about

(A) 50 Hz.

(B) 20 Hz.


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(C) 2 Hz.

(D) Zero.

Ans: C

5.The size of a conductor used in power cables depends on the

(A) operating voltage. (B) power factor.

(C) current to be carried. (D) type of insulation

used.

Ans: C

6. The most suitable servomotor for low power applications is

(A) a dc series motor.

(B) a dc shunt motor.

(C) an ac two-phase induction motor.

(D) an ac series motor.

Ans: B

7.A two-winding single phase transformer has a voltage regulation of 4.5% at

full-load and unity power-factor. At full-load and 0.80 power-factor lagging

load the voltage regulation will be

(A) 4.5%. (B) less than 4.5%. (C) more than

4.5%. (D) 4.5% or more than 4.5%. Ans: C

8 When a synchronous motor is running at synchronous speed, the damper

winding produces

(A) damping torque.

(B) eddy current torque.

(C) torque aiding the developed torque.

(D) no torque.

Ans: D


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9 If a transformer primary is energised from a square wave voltage source, its

output voltage will be

(A) A square wave.

(B) A sine wave.

(C) A triangular wave.

(D) A pulse wave.

Ans: A

10 In a d.c. series motor the electromagnetic torque developed is proportional

to

(A) Ia

(B) (Ia)2

(C) 1/Ia

(D) 1/(Ia)2

Ans: B

11.The two windings of a transformer is

(A) conductively linked.

(B) inductively linked.

(C) not linked at all.

(D) electrically linked.

Ans : B

12.In a 3 – phase induction motor running at slip „s‟ the mechanical power

developed in terms of air gap power

(A) (s-1)Pg

( B) Pg/(1-s)

(C) (1-s)Pg


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(D) s.Pg

Ans: C

13. In a 3 – phase induction motor the maximum torque

(A) is proportional to rotor resistance r 2

(B) does not depend on r 2

(C) is proportional to sqrt(r 2)

(D) is proportional to (r 2)2

Ans: B

13 In a d.c. machine, the armature mmf is

(A) stationary w.r.t. armature.

(B) rotating w.r.t. field.

(C) stationary w.r.t. field.

(D) rotating w.r.t. brushes.

Ans: C

14 In a transformer the voltage regulation will be zero when it operates at

(A) unity p.f.

(B) leading p.f.

(C) lagging p.f.

(D) zero p.f. leading.

Ans: B

15. A salient pole synchronous motor is running at no load. Its field current is

switched off. The motor will

(A) come to stop.

(B) continue to run at synchronous speed.


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(C) continue to run at a speed slightly more than the synchronous speed.

(D) continue to run at a speed slightly less than the synchronous speed.

Ans: B

16.The maximum power in cylindrical and salient pole machines is obtained

respectively at load angles of

(A) 900,900

(B) 900

(D) 900,


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(B) it cannot be readily interfaced with micro computer based controller.

(C) the angular displacement cannot be precisely controlled.

(D) it cannot be used for positioning of work tables and tools in NC machines.

Ans: A

20.The emf induced in the primary of a transformer

(A) is in phase with the flux.

(B) lags behind the flux by 90 degree.

(C) leads the flux by 90 degree.

(D) is in phase opposition to that of flux.

Ans: C

21.The d.c. series motor should always be started with load because

(A) at no load, it will rotate at dangerously high speed.

(B) it will fail to start.

(C) it will not develop high starting torque.

(D) all are true.

Ans: A

22.The relative speed between the magnetic fields of stator and rotor under

steady state operation is zero for a

(A) dc machine.

(B) 3 phase induction machine.

(C) synchronous machine.

(D) single phase induction machine.

Ans: all options are correct

23.The power factor of a squirrel cage induction motor is

(A) low at light load only.


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(B) low at heavy load only.

(C) low at light and heavy load both.

(D) low at rated load only.

Ans: A

24. A hysteresis motor

(A) is not a self-starting motor.

(B) is a constant speed motor.

(C) needs dc excitation.

(D) can not be run in reverse speed.

Ans: B

25.Out of the following methods of heating the one which is independent of

supply frequency is

(A) electric arc heating (B) induction heating (C) electric

resistance heating (D) dielectric heating

Ans: C

26. A balanced three-phase, 50 Hz voltage is applied to a 3 phase, 4 pole,

induction motor. When the motor is delivering rated output, the slip is found to

be 0.05. The speed of the rotor m.m.f. relative to the rotor structure is

(A) 1500 r.p.m.

(B) 1425 r.p.m.

(C) 25 r.p.m.

(D) 75 r.p.m.

Ans: D

27.An alternator is delivering rated current at rated voltage and 0.8 power-

factor lagging case. If it is required to deliver rated current at rated voltage and


19/60

0.8 power-factor leading, the required excitation will be

(A) less.

(B) more.

(C) more or less.

(D) the same.

Ans: B

28.The generation voltage is usually

(A) between 11 KV and 33 KV.

(B) between 132 KV and 400 KV.

(C) between 400 KV and 700 KV.

(D) None of the above.

Ans: A

29. A ceiling fan uses

(A) split-phase motor.

(B) capacitor start and capacitor run motor.

(C) universal motor.

(D) capacitor start motor.

Ans: D


20/60

Electrical Circuits and Networks:

1. The ratio of voltage and electric current in a closed circuit

(a) remains constant (b) varies (c) increases (d) falls

2. The resistance of a wire varies inversely as

(a) area of cross section (b) length (c) resistivity (d) temperature

3. The electrical conductivity of metals is typically of the order of ( in ohm-1 m-1)

(a) 10 to the power of 7 (b) 10 to the power of 5 (c) 10 to the power of -4 (d) 10 to the power

of -6

4. Four resistors, each of resistance R ohms are available. The minimum resistance of the

combination will be

(a) 4R (b) R (c) R/4 (d) R/8

5. The elements which are not capable of delivering energy by its own are known as

(a) unilateral elements (b) non-linear elements (c) passive elements (d) active elements

6. The magentic susceptibility of paramagnetic material is

(a) less than zero (b) less than one but positive (c) greater than one (d) equal to zero

7. The Direction of current in an ac circuit

(a) is from positive to negative (b) is always in one direction (c) varies from instant to instant

(d)Cannot be determined

8. which of the following statements associated with purely resistive circuits is correct?

(a) PF is unity (b) Power consumed is zero (c) Heat produced is zero (d) PF is zero

9. The magnetic field energy in an inductor changes from maximum value to minimum value in

in 5m sec when connected to an ac source. The frequency of the source is(a) 20 Hz (b) 50 Hz (c) 200 Hz (d) 500 Hz

10.

Control Systems:

1. Electronic control systems have the serious draw-backs of

(a) low reliability (b) operational difficulty (c) temperature sensitiveness (d) all of above


21/60

2. The system whose characteristic equation has the following roots is marginally stable

(a) -j, j, -1,1 (b) -3,-2,0 (c) -2+3j, -2-3j, -2 (d) -3,-2,-1

3. A phase log compensation will

(a) improve relative stability

(b)increase the speed of response

(c)increase band-width

(d) increase overshoot

4. For Nyquist plot we use

a. open loop function

b. closed loop function

c. characteristic equation

d. any of the above

A system with gain margin close to unity or a phase margin close to zero is

a. highly stable

b. oscillatory

c. relatively stable

d. none of these

Root locus diagram exhibits the

a. frequency response of a system

b. poles of the transfer function for a set of parameter values

c. bandwidth of system

d. all of the above

Increase in the gain K makes the system

a. more stable

b. unstable

c. none of above

The transfer function of a system is used to determine

a. the output for a given input

b. the type of system


22/60

c. the input for a given output

d. the steady state gain

In a servo system the voltage induced in the control transformer rotor is the

a. error voltage

b. driving voltage

c. opposing voltage

d. none of these

With the feedback system, the transient response

a. decays slowly

b. decays rapidly

c. rises slowly

d. rises quickly

Measurements and Instrumentation

1. Which of the following types of instrument is an integrating instrument?

a. power factor meter

b. energy meter

c. wattmeter

d. frequent meter

Which of the material is used for the ‟swamping‟ resistance that is connected in series with

the working coil of a voltmeter?

a. Constantan

b. Manganin

c. Eureka

d. Nichrome

What are used to increase the range of ammeters.


23/60

a. Multipliers

b. Shunts

c. Control Springs

d. Potential transformers

Which voltmeter do you select for measuring 50KV DC?

a. Moving Coil Voltmeter

b. Hot wire voltmeter

c. Electro Dynamo meter

d. Electrostatic Voltmeter

Which of the following you will prefer to extend the range of an ac voltmeter?

a. Low series resistance

b. high resistance in parallel

c. CT

d. PT

High AC voltages are usually measured with

a. magnetic voltmeter

b. inductive voltmeter

c. potential transformers with voltmeters

d. current transformers and voltmeters

Creeping is the phenomena occurs in

a. voltmeter

b. wattmeter

c. energy meter

d. ammeter


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Q.1 The two windings of a transformer is





Ans : B

Q.2 A salient pole synchronous motor is running at no load. Its field current is switched off.

The motor will

(A) come to stop.(B) continue to run at synchronous speed.



Ans: B

Q.3 The d.c. series motor should always be started with load because




(D) all are true.

Ans: A

Q.4 The frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction motor at full load

speed is about

(A) 50 Hz.

(B) 20 Hz.

(C) 2 Hz.

(D) Zero.

Ans: C

Q.5 In a stepper motor the angular displacement

(A) can be precisely controlled.




Ans: A

Q.6 The power factor of a squirrel cage induction motor is

(A) low at light load only.(B) low at heavy load only.

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Ans: A

Q.7 The generation voltage is usually(A) between 11 KV and 33 KV.




Ans: A

Q.8 When a synchronous motor is running at synchronous speed, the damper winding

produces

(A) damping torque.



(D) no torque.

Ans: D

Q.9 If a transformer primary is energised from a square wave voltage source, its output

voltage will be

(A) A square wave.

(B) A sine wave.


(D) A pulse wave.

Ans: A

Q.10 In a d.c. series motor the electromagnetic torque developed is proportional to

(A) Ia

(B) (Ia)2

(C) 1/Ia

(D) 1/(Ia)2

Ans: B

Q.11 In a 3 – phase induction motor running at slip „s‟ the mechanical power developed in

terms of air gap power

(A) (s-1)Pg

( B) Pg/(1-s)

(C) (1-s)Pg

(D) s.Pg

Ans: C


26/60

Q.12 In a 3 – phase induction motor the maximum torque





Ans: B

Q.13 In a d.c. machine, the armature mmf is





Ans: C

Q.14 In a transformer the voltage regulation will be zero when it operates at

(A) unity p.f.

(B) leading p.f.

(C) lagging p.f.


Ans: B

Q.15 The maximum power in cylindrical and salient pole machines is obtained respectively

at load angles of

(A) 900,900

(B) 900

(D) 900,


27/60

Q.18 The relative speed between the magnetic fields of stator and rotor under steady state

operation is zero for a

(A) dc machine.

(B) 3 phase induction machine.(C) synchronous machine.



Q.19 The current from the stator of an alternator is taken out to the external load circuit

through

(A) slip rings.



(D) carbon brushes.

Ans: C

Q.20 A motor which can conveniently be operated at lagging as well as leading power

factors is the




(D) DC shunt motor.

Ans: C

Q.21 A hysteresis motor





Ans: B

Q.22 The most suitable servomotor for low power applications is(A) a dc series motor.




Ans: B

Q.23 The size of a conductor used in power cables depends on the


(C) current to be carried. (D) type of insulation used. Ans: CQ.24

Out of the following methods of heating the one which is independent of supply frequency is

(A) electric arc heating (B) induction heating


28/60

(C) electric resistance heating (D) dielectric heating

Ans: C

Q.25 A two-winding single phase transformer has a voltage regulation of 4.5% at full-load

and unity power-factor. At full-load and 0.80 power-factor lagging load the voltage regulationwill be

(A) 4.5%. (B) less than 4.5%.

(C) more than 4.5%. (D) 4.5% or more than 4.5%.

Ans: C

Q.26 In a dc shunt motor the terminal voltage is halved while the torque is kept constant.

The resulting approximate variation in speed ” ω” and armature current “Ia„” will be

(A) Both ω and Ia are doubled.




Ans: B

Q.27 A balanced three-phase, 50 Hz voltage is applied to a 3 phase, 4 pole, induction

motor. When the motor is delivering rated output, the slip is found to be 0.05. The speed of

the rotor m.m.f. relative to the rotor structure is

(A) 1500 r.p.m.

(B) 1425 r.p.m.

(C) 25 r.p.m.

(D) 75 r.p.m.

Ans: D

Q.28 An alternator is delivering rated current at rated voltage and 0.8 power-factor lagging

case. If it is required to deliver rated current at rated voltage and 0.8 power-factor leading,

the required excitation will be

(A) less.

(B) more.

(C) more or less.

(D) the same.

Ans: B

Q.29 A ceiling fan uses





Ans: D


29/60

Q.30 A stepper motor is

(A) a dc motor. (B) a single-phase ac motor. (C) a multi-phase

motor. (D) a two phase motor.

Ans: D

Q.31 The „sheath‟ is used in cable to

(A) provide strength to the cable.

(B) provide proper insulation.

(C) prevent the moisture from entering the cable.

(D) avoid chances of rust on strands.

Ans: A

Q.32 The drive motor used in a mixer-grinder is a

(A) dc motor. (B) induction motor. (C) synchronous motor. (D)

universal motor.

Ans: DQ.33 A 1:5 step-up transformer has 120V across the primary and 600 ohms

resistance across the secondary. Assuming 100% efficiency, the primary current equals(A)

0.2 Amp. (B) 5 Amps. (C) 10 Amps. (D) 20 Amps.

Ans: A

Q.34 A dc shunt generator has a speed of 800 rpm when delivering 20 A to the load at the

terminal voltage of 220V. If the same machine is run as a motor it takes a line current of 20A

from 220V supply. The speed of the machine as a motor will be(A) 800 rpm. (B) more than 800 rpm. (C) less than 800 rpm. (D) both

higher or lower than 800 rpm.

Ans: C

Q.35 A 50 Hz, 3-phase induction motor has a full load speed of 1440 r.p.m. The number of

poles of the motor are

(A) 4. (B) 6. (C) 12. (D) 8.

Ans: A

Answer Keys

1 B 2 C 3 A 4 D 5 B 6 D 7 A

8 A 9 B 10 D 11 D 12 B 13 A 14 C

15 B 16 C 17 C 18 D 19 B 20 C 21 D

22 C 23 A 24 A 25 D 26 C 27 D 28 D


30/60

29 B 30 C 31 C 32 A 33 A 34 B 35 B

36 A 37 A 38 C 39 A 40 D 41 D 42 C

43 A 44 C 45 A 46 C 47 B 48 C 49 A

50 A 51 B 52 C 53 D 54 A 55 C 56 B

57 A 58 A 59 B 60 D

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AP GENCO - TECHNICAL PAPER



AP CPDCL ELECTRICAL - TECHNICAL PAPER


BHEL ELECTRICAL - - TECHNICAL PAPER

TEHNICAL PAPER 2010

TEHNICAL PAPER 2009

1. In a dc shunt motor the terminal voltage is halved while the torque is kept

constant. The resulting approximate variation in speed ” ω” and armature

current “Ia„” will be

(A) Both ω and Iaare doubled.




Ans: B

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31/60

2.The current from the stator of an alternator is taken out to the external load

circuit through

(A) slip rings.



(D) carbon brushes.

Ans: C

3.A motor which can conveniently be operated at lagging as well as leading

power factors is the




(D) DC shunt motor.

Ans: C

4 The frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction

motor at full load speed is about

(A) 50 Hz.

(B) 20 Hz.

(C) 2 Hz.

(D) Zero.

Ans: C

5.The size of a conductor used in power cables depends on the


(C) current to be carried. (D) type of insulationused.


32/60

Ans: C

6. The most suitable servomotor for low power applications is

(A) a dc series motor.




Ans: B

7.A two-winding single phase transformer has a voltage regulation of 4.5% at

full-load and unity power-factor. At full-load and 0.80 power-factor lagging

load the voltage regulation will be

(A) 4.5%. (B) less than 4.5%. (C) more than

4.5%. (D) 4.5% or more than 4.5%. Ans: C

8 When a synchronous motor is running at synchronous speed, the damper

winding produces

(A) damping torque.



(D) no torque.

Ans: D

9 If a transformer primary is energised from a square wave voltage source, its

output voltage will be

(A) A square wave.

(B) A sine wave.


(D) A pulse wave.

Ans: A


33/60

10 In a d.c. series motor the electromagnetic torque developed is proportional

to

(A) Ia

(B) (Ia)2

(C) 1/Ia

(D) 1/(Ia)2

Ans: B

11.The two windings of a transformer is





Ans : B

12.In a 3 – phase induction motor running at slip „s‟ the mechanical power

developed in terms of air gap power

(A) (s-1)Pg

( B) Pg/(1-s)

(C) (1-s)Pg

(D) s.Pg

Ans: C

13. In a 3 – phase induction motor the maximum torque






34/60

Ans: B

13 In a d.c. machine, the armature mmf is





Ans: C

14 In a transformer the voltage regulation will be zero when it operates at

(A) unity p.f.

(B) leading p.f.

(C) lagging p.f.


Ans: B

15. A salient pole synchronous motor is running at no load. Its field current is

switched off. The motor will

(A) come to stop.

(B) continue to run at synchronous speed.



Ans: B

16.The maximum power in cylindrical and salient pole machines is obtained

respectively at load angles of

(A) 900,900

(B) 900


35/60

(D) 900,


36/60

21.The d.c. series motor should always be started with load because




(D) all are true.

Ans: A

22.The relative speed between the magnetic fields of stator and rotor under

steady state operation is zero for a

(A) dc machine.

(B) 3 phase induction machine.

(C) synchronous machine.



23.The power factor of a squirrel cage induction motor is

(A) low at light load only.

(B) low at heavy load only.



Ans: A

24. A hysteresis motor





Ans: B


37/60

25.Out of the following methods of heating the one which is independent of

supply frequency is

(A) electric arc heating (B) induction heating (C) electric

resistance heating (D) dielectric heating

Ans: C

26. A balanced three-phase, 50 Hz voltage is applied to a 3 phase, 4 pole,

induction motor. When the motor is delivering rated output, the slip is found to

be 0.05. The speed of the rotor m.m.f. relative to the rotor structure is

(A) 1500 r.p.m.

(B) 1425 r.p.m.

(C) 25 r.p.m.

(D) 75 r.p.m.

Ans: D

27.An alternator is delivering rated current at rated voltage and 0.8 power-

factor lagging case. If it is required to deliver rated current at rated voltage and

0.8 power-factor leading, the required excitation will be

(A) less.

(B) more.

(C) more or less.

(D) the same.

Ans: B

28.The generation voltage is usually

(A) between 11 KV and 33 KV.




38/60


Ans: A

29. A ceiling fan uses





Ans: D


39/60

Electrical Circuits and Networks:

1. The ratio of voltage and electric current in a closed circuit

(a) remains constant (b) varies (c) increases (d) falls

2. The resistance of a wire varies inversely as

(a) area of cross section (b) length (c) resistivity (d) temperature

3. The electrical conductivity of metals is typically of the order of ( in ohm-1 m-1)

(a) 10 to the power of 7 (b) 10 to the power of 5 (c) 10 to the power of -4 (d) 10 to the power

of -6

4. Four resistors, each of resistance R ohms are available. The minimum resistance of the

combination will be

(a) 4R (b) R (c) R/4 (d) R/8

5. The elements which are not capable of delivering energy by its own are known as

(a) unilateral elements (b) non-linear elements (c) passive elements (d) active elements

6. The magentic susceptibility of paramagnetic material is

(a) less than zero (b) less than one but positive (c) greater than one (d) equal to zero

7. The Direction of current in an ac circuit

(a) is from positive to negative (b) is always in one direction (c) varies from instant to instant

(d)Cannot be determined

8. which of the following statements associated with purely resistive circuits is correct?

(a) PF is unity (b) Power consumed is zero (c) Heat produced is zero (d) PF is zero

9. The magnetic field energy in an inductor changes from maximum value to minimum value in

in 5m sec when connected to an ac source. The frequency of the source is(a) 20 Hz (b) 50 Hz (c) 200 Hz (d) 500 Hz

10.

Control Systems:

1. Electronic control systems have the serious draw-backs of

(a) low reliability (b) operational difficulty (c) temperature sensitiveness (d) all of above


40/60

2. The system whose characteristic equation has the following roots is marginally stable

(a) -j, j, -1,1 (b) -3,-2,0 (c) -2+3j, -2-3j, -2 (d) -3,-2,-1

3. A phase log compensation will

(a) improve relative stability

(b)increase the speed of response

(c)increase band-width

(d) increase overshoot

4. For Nyquist plot we use

a. open loop function

b. closed loop function

c. characteristic equation

d. any of the above

A system with gain margin close to unity or a phase margin close to zero is

a. highly stable

b. oscillatory

c. relatively stable

d. none of these

Root locus diagram exhibits the

a. frequency response of a system

b. poles of the transfer function for a set of parameter values

c. bandwidth of system

d. all of the above

Increase in the gain K makes the system

a. more stable

b. unstable

c. none of above

The transfer function of a system is used to determine

a. the output for a given input

b. the type of system


41/60

c. the input for a given output

d. the steady state gain

In a servo system the voltage induced in the control transformer rotor is the

a. error voltage

b. driving voltage

c. opposing voltage

d. none of these

With the feedback system, the transient response

a. decays slowly

b. decays rapidly

c. rises slowly

d. rises quickly

Measurements and Instrumentation

1. Which of the following types of instrument is an integrating instrument?

a. power factor meter

b. energy meter

c. wattmeter

d. frequent meter

Which of the material is used for the ‟swamping‟ resistance that is connected in series with

the working coil of a voltmeter?

a. Constantan

b. Manganin

c. Eureka

d. Nichrome

What are used to increase the range of ammeters.


42/60

a. Multipliers

b. Shunts

c. Control Springs

d. Potential transformers

Which voltmeter do you select for measuring 50KV DC?

a. Moving Coil Voltmeter

b. Hot wire voltmeter

c. Electro Dynamo meter

d. Electrostatic Voltmeter

Which of the following you will prefer to extend the range of an ac voltmeter?

a. Low series resistance

b. high resistance in parallel

c. CT

d. PT

High AC voltages are usually measured with

a. magnetic voltmeter

b. inductive voltmeter

c. potential transformers with voltmeters

d. current transformers and voltmeters

Creeping is the phenomena occurs in

a. voltmeter

b. wattmeter

c. energy meter

d. ammeter


43/60

APGENCO AE Hall Tickets 2012 Downlo ad Click Here new

Q.1 The two windings of a transformer is





Ans : B

Q.2 A salient pole synchronous motor is running at no load. Its field current is switched off.

The motor will

(A) come to stop.(B) continue to run at synchronous speed.



Ans: B

Q.3 The d.c. series motor should always be started with load because




(D) all are true.

Ans: A

Q.4 The frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction motor at full load

speed is about

(A) 50 Hz.

(B) 20 Hz.

(C) 2 Hz.

(D) Zero.

Ans: C

Q.5 In a stepper motor the angular displacement

(A) can be precisely controlled.




Ans: A

Q.6 The power factor of a squirrel cage induction motor is

(A) low at light load only.(B) low at heavy load only.

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44/60



Ans: A

Q.7 The generation voltage is usually(A) between 11 KV and 33 KV.




Ans: A

Q.8 When a synchronous motor is running at synchronous speed, the damper winding

produces

(A) damping torque.



(D) no torque.

Ans: D

Q.9 If a transformer primary is energised from a square wave voltage source, its output

voltage will be

(A) A square wave.

(B) A sine wave.


(D) A pulse wave.

Ans: A

Q.10 In a d.c. series motor the electromagnetic torque developed is proportional to

(A) Ia

(B) (Ia)2

(C) 1/Ia

(D) 1/(Ia)2

Ans: B

Q.11 In a 3 – phase induction motor running at slip „s‟ the mechanical power developed in

terms of air gap power

(A) (s-1)Pg

( B) Pg/(1-s)

(C) (1-s)Pg

(D) s.Pg

Ans: C


45/60

Q.12 In a 3 – phase induction motor the maximum torque





Ans: B

Q.13 In a d.c. machine, the armature mmf is





Ans: C

Q.14 In a transformer the voltage regulation will be zero when it operates at

(A) unity p.f.

(B) leading p.f.

(C) lagging p.f.


Ans: B

Q.15 The maximum power in cylindrical and salient pole machines is obtained respectively

at load angles of

(A) 900,900

(B) 900

(D) 900,


46/60

Q.18 The relative speed between the magnetic fields of stator and rotor under steady state

operation is zero for a

(A) dc machine.

(B) 3 phase induction machine.(C) synchronous machine.



Q.19 The current from the stator of an alternator is taken out to the external load circuit

through

(A) slip rings.



(D) carbon brushes.

Ans: C

Q.20 A motor which can conveniently be operated at lagging as well as leading power

factors is the




(D) DC shunt motor.

Ans: C

Q.21 A hysteresis motor





Ans: B

Q.22 The most suitable servomotor for low power applications is(A) a dc series motor.




Ans: B

Q.23 The size of a conductor used in power cables depends on the


(C) current to be carried. (D) type of insulation used. Ans: CQ.24

Out of the following methods of heating the one which is independent of supply frequency is

(A) electric arc heating (B) induction heating


47/60

(C) electric resistance heating (D) dielectric heating

Ans: C

Q.25 A two-winding single phase transformer has a voltage regulation of 4.5% at full-load

and unity power-factor. At full-load and 0.80 power-factor lagging load the voltage regulationwill be

(A) 4.5%. (B) less than 4.5%.

(C) more than 4.5%. (D) 4.5% or more than 4.5%.

Ans: C

Q.26 In a dc shunt motor the terminal voltage is halved while the torque is kept constant.

The resulting approximate variation in speed ” ω” and armature current “Ia„” will be

(A) Both ω and Ia are doubled.




Ans: B

Q.27 A balanced three-phase, 50 Hz voltage is applied to a 3 phase, 4 pole, induction

motor. When the motor is delivering rated output, the slip is found to be 0.05. The speed of

the rotor m.m.f. relative to the rotor structure is

(A) 1500 r.p.m.

(B) 1425 r.p.m.

(C) 25 r.p.m.

(D) 75 r.p.m.

Ans: D

Q.28 An alternator is delivering rated current at rated voltage and 0.8 power-factor lagging

case. If it is required to deliver rated current at rated voltage and 0.8 power-factor leading,

the required excitation will be

(A) less.

(B) more.

(C) more or less.

(D) the same.

Ans: B

Q.29 A ceiling fan uses





Ans: D


48/60

Q.30 A stepper motor is

(A) a dc motor. (B) a single-phase ac motor. (C) a multi-phase

motor. (D) a two phase motor.

Ans: D

Q.31 The „sheath‟ is used in cable to

(A) provide strength to the cable.

(B) provide proper insulation.

(C) prevent the moisture from entering the cable.

(D) avoid chances of rust on strands.

Ans: A

Q.32 The drive motor used in a mixer-grinder is a

(A) dc motor. (B) induction motor. (C) synchronous motor. (D)

universal motor.

Ans: DQ.33 A 1:5 step-up transformer has 120V across the primary and 600 ohms

resistance across the secondary. Assuming 100% efficiency, the primary current equals(A)

0.2 Amp. (B) 5 Amps. (C) 10 Amps. (D) 20 Amps.

Ans: A

Q.34 A dc shunt generator has a speed of 800 rpm when delivering 20 A to the load at the

terminal voltage of 220V. If the same machine is run as a motor it takes a line current of 20A

from 220V supply. The speed of the machine as a motor will be(A) 800 rpm. (B) more than 800 rpm. (C) less than 800 rpm. (D) both

higher or lower than 800 rpm.

Ans: C

Q.35 A 50 Hz, 3-phase induction motor has a full load speed of 1440 r.p.m. The number of

poles of the motor are

(A) 4. (B) 6. (C) 12. (D) 8.

Ans: A

Answer Keys

1 B 2 C 3 A 4 D 5 B 6 D 7 A

8 A 9 B 10 D 11 D 12 B 13 A 14 C

15 B 16 C 17 C 18 D 19 B 20 C 21 D

22 C 23 A 24 A 25 D 26 C 27 D 28 D


49/60

29 B 30 C 31 C 32 A 33 A 34 B 35 B

36 A 37 A 38 C 39 A 40 D 41 D 42 C

43 A 44 C 45 A 46 C 47 B 48 C 49 A

50 A 51 B 52 C 53 D 54 A 55 C 56 B

57 A 58 A 59 B 60 D

OTHER PAPERS

AP TRANSCO ELECTRICAL - TECHNICAL PAPER

SUB-ENGINEERS TECHNICAL PAPER 2012

ENGINEERS TECHNICAL PAPER 2012

ELECTRICAL PAPER -SOME IMPORTANT QUESTIONS

AP GENCO - TECHNICAL PAPER



AP CPDCL ELECTRICAL - TECHNICAL PAPER


BHEL ELECTRICAL - - TECHNICAL PAPER

TEHNICAL PAPER 2010

TEHNICAL PAPER 2009

APTRANSCO 2012 KEY ELECTRICAL

1.

1. A voltage waveform v(t)= 12 t2 is applied across a 1H inductor for t>=0 withinitial current through it being zero. The current through the inductor for

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50/60

t>=0 is given by-----------(4t3)

2. Two incandescent light bulbs fo 40w and 60w rating

are connected in series across the mains. Then--------(the 40 bulb glows brighter)

3. Given two coupled inductors L1 and L2, their mutual

inductances M satisfies-----(M

4. Consider the star network. The resistance between

terminals A and B with C open 6ohms, between terminals B and C with A open is

11ohms, and between terminals C and A with B open is 9ohms. Then

------------(Ra=2, Rb=4, Rc=7)

5. In a series RLC circuit at resonance, the magnitude

of the voltage developed across the capacitor------( can be greater than the

input voltage, however, it is 900 out of phase with the input voltage)

6. A two port device is defined by the following pair

of quations:

i1=2v1+v2 and i2=v1+v2 its impedance parameters

(z11, z12, z21, z22) are-----(1,-1,-1,2)

7. The impulse response of an initially relaxed linear

system is e-2tu(t).to produce a response of

te-2tu(t), the input must be equal

to--------(e-2t u(t))



9. For a feedback control system of type 2, the steady

state error for a ramp input is-------(zero)

10. The output of a linear time invariant control

system is c(t) for a certain input r(t). if r(t) is modified by passing it

through a block whose transfer function is e-s and then applied to the system,

the modified output of the system would be-----------(c(t-1)u(t-1)



12. Consider two buses connected by an impedance of

(0+j5)ohm. The bus 1 voltage is 100/300 v, and bus 2 voltage is 100/00 v. the real andreactive power supplied by bus 1,


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resp are……….(1000w, 268 VAr)

13. For a fixed value of complex power flow in a

transmission line having a sending end voltage V, the real power loss will be

proportional to-----------(1/V2).

14. During a disturbance on a synchronous machine, the

rotor swings from A to B before finally settling down to a steady state at

point C on the power angle curve. The speed of the machine during oscillation

is synchronous at point(s)--------------------(A and B)

15. A 100 MVA, 11kv, 3 phase 50hz, 8 pole synchronous

generator has an inertia constant H equal to 4 MJ/MVA. The stored energy in the


16. In a biased differential relay the bias is defined

as a ratio of----------(operating coil current and restraining coil current))

17. Resistance switching is normally employed

in------(ABCB)

18. The use of high speed circuit breakers----(improves

system stability)

19. Keeping in view the cost and overall effectiveness,

the following circuit breaker is best suited for capacitor bank

switching---(vacuum)

20. If the reference bus is changed in two load flow

runs with the same system data and power obtained for reference bus taken as

specified P and Q in the latter run----------( the system losses will be

unchanged but complex bus voltages will change.)

21. The gauss seidel load flow method has following

disadvantages. Tick the incorrect statement------( unreliable convergence)

22. The torque speed characteristics of a repulsion

motor resembles which of the following dc motor

characteristic------------(series)

23. Which type of motor is most suitable for computer

printer drive-----(stepper motor)

24. A 4 pole lap wound DC generator has a developed

power of P watts and voltage of E volts. Two adjacent brushes of the machineare removed as they are worn out. If the machine operates with the remaining


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brushes, the developed voltage and power that can be obtained from the machine

are----(E,P/4)

25. A 4 point starter is used to start and control the

speed of a -----------( dc shunt motor with field weakening control)

26. The function of oil in a transformer is-----( to

provide insulation and cooling)

27. The core flux of a practical transformer with a

resistive load------------( is strictly constant with load changes)

28. In a transformer zero voltage regulation at full

load is----(possible at leading pf load)

29. A single phase transformer has a turns ratio of

1:2, and is connected to a purely resistive load. The magnetizing current drawn

is 1 A, and the secondary current is 1A. if core losses and leakage reactance


30. The low voltage winding of a 400/230V, single phase

50hz transformer is to be connected to a 25hz, the supply voltage should

be-------(115V)

31. A 400/100V, 10 KVA two winding transformer is

reconnected as an auto transformer is reconnected as an auto transformer across

a suitable voltage source. The maximum rating of such an arrangement could

be-----(50KVA)

32. When the supply voltage to an induction motor is

reduced by 10%, the maximum torque will decrease by approximately-------(20%)

33. In case of a split phase motor, the phase shift

between currents in the two windings is around------(300)

34. Starting torque can be obtained in the case of a

single phase induction motor with identical main and auxiliary windings by

connecting-----( a capacitor in series with the auxiliary winding)


which of the following statements is valid---( the direction of rotation can be

changed by reversing the main winding terminals)

36. An induction motor having full load torque of 60zNm

when delta connected develops a starting torque of 120Nm. For the same supply voltage, if the motor is changed to star-connection, the starting torque


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developed will be-------(40NM)

37. During hunting of synchronous motor –(damper bar

develops torque)

38. The phase sequence of a three phase alternator will

reverse if -------(the field current remains the same but the direction of


39. The effect of stray magnetic fields on the

actuating torque of a portable instrument is max when the operating filed of

the instrument and the stray fields are-(parallel)


(sinwt+300)A is passed through three

meters. They are a center zero PMMC meter, true rms meter and MI instrument.

The respective reading( in A) will be----(-8,10,10)

41. R1 and R2 are the opposite arms of a wheatstone

bridge as are R3 and R, the source voltage is applied across R1 and R3 under

balanced conditions which one of the following is true---(R1=R2R3/R4)

42. A dc potentiometer is designed to measure up to

about 2v with a slide wire of 800mm. a standard cell of emf 1.18v obtains

balance at 6010mm. a test cell is seen to obtain balance at 680mm. the emf of

the test cell is-(1.34v)

43. The minimum number of wattmeters required to

measure3 phase 3 wire or unbalanced power is—(2)

44. A reading of 120 is obtained when a standard

inductor was connected in the circuit of a Q meter and the variable capacitor

is adjusted to a value of 300pF. A lossless capacitor of unknown value C, is

then connected and the same reading was obtained when the variable capacitor isreadjusted to a value of 200pF. The value of Cx in pF is—(100)

45. The two inputs of a CRO are fed with the two

stationary periodic signals. In the X Y mode, the screen shows a figure which

changes from ellipse to circle and back to ellipse with its major axis changing

orientation slowly and repeatedly. The following inference can be made from

this----------(there is a constant but small phase difference between the

signals)

46. SCR can be turned off —( anode current should beless than holding current)


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47. The no. of pn junctions in SCR-----(3)

48. TRIAC is a—(antiparallel thyristors combination)

49. GTO can be turned off-(by using a negative current

pulse)

50. Which type of control is used for controlling the

ac drive by using thyristors--------(integral cycle)

51. In DC choppers the output voltage can be controlled

by using FM technique varying--------( T , Toff constant)

52. In phase control rectifiers the output voltage

ripple can be controlled by —‘(load inductance)

53. Which is not a current controlled

device-----(MOSFET)

54. Inverter function---------(DC to AC with variable

frequency)

55. In phase controlled rectifires free wheeling diode

makes-(load current continuation)

56. Dielectric heating application----(wood)

57. In induction heating the following is abnormally

high--------(frequency)

58. Tractive effect w.r.t driving wheel

axis--------(tangential*)

59. welding transformer sets have-------------(highcurrent, low voltage)

60. Simplify

x’y’z+x’yz’+xy’z+xyz+xyz’=-------(y’z+yz’+xz)

61. Find out y=-----------------(P+Q+R+S)

OTHER PAPERS

AP TRANSCOELECTRICAL - TECHNICAL PAPER


55/60

SUB-ENGINEERS


ENGINEERS


ELECTRICAL

PAPER -SOME IMPORTANT QUESTIONS

AP GENCO -

TECHNICAL PAPER

APTRANSCO SUB ENGINEERS 2012 KEY

1. The speed torque characteristics of a series motor is a/an--------------

(Hyperbola)

2. In ad dc generator, if the variable loss is equal to constant loss, then

efficiency is-------(Max)

3. The armature of a dc machine is laminated to reduce-----(eddy

current loss)

4. The initial flux in a dc generator is provided by-----(residual magnetism)

5. For the operation of milling machine, which motor is used----( DC shunt

motor)

6. In a series motor, the torque is----( proportional to square of armature

current)

7. By conducting swinburn’s test on a dc machine, the following losses can

be determined-----( constant losses)

8. The series motors have relatively----( High starting torque)

9. In a dc shunt motor, the torque developed is 15Nm at 10A of load

current. If the load current is doubled, the new torque will be----(30Nm).

10. The internal characteristics of s dc shunt generator is a plot between---

-(Eg and Ia)

11. The back emf of motor at the time starting is -----------(zero)

12. At low flux densities, the flux in a dc generator varies----(Linearly with

field current)

13. Three resistances of R ohms each are connected in delta. Its equivalent

resistances in star connection per phase is -----(R/3 each)


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14. The RMS value of a triangular wave of alternating quantity having peak

value 3A is -----(sqrt 3)

15. In as series RL circuit, the voltage across the resistance is 40V and

voltage across inductance is 40v. Then the total voltage across the series

circuit--------(56.56V)

16. A transformer can have regulation closer to zero---( on leading pf)

17. The full load copper loss of a transformer is 1600watts. At half load,

the copper loss----(400watts)

18. A 440/110, 1- phase transformer has a primary resistance of 0.03ohms

and secondary resistance of 0.02ohms. its iron losses at normal input are 150

watts. The secondary current at which the maximum efficiency will occur is ----

---(82.80A)19. Which of the following transformers should never have the secondary

open circuited while primary is energized---------(CT)

20. An isolation transformer has primary to secondary turn’s ratio of -------

(1:1)

21. In a 50 KVA, 1-phase transformer, the iron loss is 500W and full load

copper loss is 800W. The efficiency of the transformer at full load at 0.8 pf

lagging is----(96.85%)

22. A synchronous motor can be used as a synchronous capacitor when it

is---(over excited)

23. The harmonic component of the generated emf will be more in

alternators with-------(Full pitch coils)

24. V-curves for a synchronous motor represent the relation between---(Ia

and If)

25. The crawling in an induction motor is caused by-----(harmonics

developed in the motor)

26. The ratio of starting torque to normal torque in case of a star delta

starter will be---(1/3)

27. A 3-phase, 440v, 50hz induction motor has 4% slip. The frequency

of rotor emf will be----(2Hz)

28. In a tuned line-----------( receiving end voltage and current are

numerically equal to corresponding sending end values)

29. The max torque in an induction motor depends on------(frequency)

30.

which of the following motors will have relatively high power factor---

(capacitor run motor)


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31. which of the following motors can be used for unity pf---(Schrage

motor)

32. which of the following turbines will be used for heads from 500m to

200m--------(Francis)

33. The sudden change of pressure in penstock pipes due to sudden

reaction of load is avoided using-------(surge tank)

34. Which of the following heat exchangers is used to raise the

temperature of steam from normal to super saturation level------(superheater)

35. which of the following treatments for water is used to remove non

carbonate hardness-----(Soda treatment)

36. The hoppers in electrostatic precipitator are generally----------in

shape(pyramidal)37. The purpose of cooling tower is---( to cool the steam in the condenser)

38. which is used to reduce the speed of the neutrons in a nuclear reactor--

---(moderator)

39. which of the following is a cladding material in nuclear reactor---

(Magnesium)

40. In which of the following reactors, reactor control is achieved by

varying moderator level ----------(CANDU)

41. A generating station has a connected load of 450MW and a maximum

demand of 250MW. The units generated are 615*10^6 per annum. The load

factor of the station is -----(0.281)

42. The plant capacity is determined by-------(Plant use factor)

43. A power plant has a maximum demand of 15MW. The load factor is

50% and the plant factor is 40%. The operating reserve is ----(3.75MW)

44. A transformer is rated at 66Kv/4001V, 1000KVA, 5% reactance. The

short circuit MVA of the transformer when connected to infinite bus is-----

(20MVA)

45. The power frequency rms voltage, that appears across the breaker

contacts after the transient oscillations die out and final extinction of arc that

results in all the poles is called-------(recovery voltage)

46. In resistance switching, the function of shunt resistor----------(reduces

the rate of rise of restriking voltage)

47. The no. of poles per phase of breaker is a function of------(Operating

voltage)

48. The capacitor switching is easily done with------(vacuum CB)


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49. A distance relay is inherently directional if its characteristics on R-X

diagram is------( a circle that passes through origin)

50. The most efficient torque producing actuating structure in an induction

relay is ---------(induction cup structure)

51. The line trap unit employed in carrier current relaying----(offers high

impedance to carrier frequency signals)

52. The protection relay used for low fault settings and high operating

speeds in a transformer is -----------(Harmonic restraint relay)

53. The wattmetric relay with directional characteristic is used for

protection of generator against------(failure of prime mover)

54. The best suited relay for 3- zone protection scheme is ----(Mho relay)

55. The rule 77 of Indian electricity rules(1956) for over head lines givesinformation about----(clearance above ground of lowest conductor)

56. The stringing charts are used to calculate-----(Tension and sag at any

temperature)

57. Due to proximity effect, the effective internal reactance of the

conductor---(decrease)

58. The inductance of a single phase two wire transmission line per

kilometer gets doubled when the----------------(distance between the wires is

increased as square of the original distance)

59. a transmission line of 210km length has certain values for A,B,C and D

parameters. If the length of line is made 100km then------(A increases and B

decreases)

60. The surge impedance loading of the line is proportional to—(V^2)

61. Under no load conditions the current in a transmission line is due to-----

-( capacitance of the line)

62. For a transmission line, the no load receiving end voltage is more than

the sending end voltage. This is called---------(Ferranti effect)

63. Corona loss can be reduced by the use of hollow conductor, because----

-( for a given cross section, the radius of the conductor is increased)

64. The non shielding method of over voltage protection is based on the

principle of --------(insulation breakdown)

65. The valve elements of non linear resistance in valve

type lighting arrester are made up of -----------(silicon carbide)

66.

Which of the following lightning arresters, can discharge currents,

between 65000 to 100000A-------(line type)


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67. Which of the following is used to reduce tower footing resistance-------

(ground rods)

68. In substations, the breaker maintenance facility is provided in the----

(main and transfer bus scheme)

69. In case of rigid bus arrangement, the size of aluminum pipe used for

voltage level of 66KV----------------(65mm)

70. For low voltage applications up to 11KV, which of the following

insulators is preferred-------(pin type)

71. In a 5 insulator disc, string capacitance between each unit and earth is

1/6 th of the mutual capacitance. The voltage distribution across the middle

unit as % of voltage applied is------(17.1)

72. An electric train taking of constant current of 600A moves on a sectionof line between two substations 8km apart maintained at 575V and 590V resp.

The track resistance is 0.04ohm per km both go and return. The point

minimum potential along the track is at a distance from 575V substation is----

(3.67Km)

73. which of the following is the most economical ac distribution system----

--( ac 3 phase 3 wire)

74. for a distributor design, if the voltage rating is increased by ‘n’ times,

the conductor size reduces to ----of the original(1/n2)

75. The pointer of an indicating instrument is generally made of ------------

(aluminum)

76. Electrostatic instruments are used as-------------only(voltmeters)

77. In a dynamometer wattmeter, the moving coil is the----(potential coil)

78. A 50V range voltmeter has a sensitivity of 20 k-ohms/volt. The total

resistance of the voltmeter is -----(1MOHM)

79. An RLC series resonant circuit has a Q of 15 and a source voltage of

50V. the voltage across the capacitor at resonance is -----(750V)

80. At parallel resonance conditions the power factor is--------(unity)

81. In AC circuit, V and I are given by: V=100sin(100t) V and

I=100sin(100t+∏/3)mA. The power dissipated in the circuit is------(2.5W)

82. In the measurement of 3-phase power by two wattmeter method, the

two wattmeter’s indicate equal readings if the power factor is----(unity)

83. In a parallel RLC circuit, below resonance frequency, the circuit behaves

as----(inductive)


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84. In a balanced 3-phase star connected system, the phase difference

between line and phase voltages is—(30deg)

85. The electric heater draws 10A from a 230V line. The resistance of the

heater is---(23ohm)

86. A wire has a resistance of 12ohms. It is bent in the form of an

equilateral triangle. The effective resistance between any two corners of the

triangle is---(8/3ohms)

87. ACSR stands for----------( Aluminum Conductor Steel Reinforced)

88. In house wiring, the total connected load per sub circuit can be---

(800W)

89. Which of the following motors is used for intermittent high torque load

and for rolling mills-----(DC cumulative compound wound motor)90. In plugging of dc motors---------(connections to armature are reversed)

91. The motor enclosure used in wood working industry is---(totally

enclosed fan cooled type)

92. The unit of luminous flux is---(lumens)

93. The illumination at a surface due to a source of light placed at

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Transco Papers 123