APTRANSCO SUB ENGINEERS 2012 Previous Paper Electrical

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)
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)
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)
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 gives information 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)
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 section of 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)
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 a distance ‘d’ from the surface varies is ---(1/d^2)
94. Reduction factor is the ration of-----(MSCP/MHSCP)
95.  Power factor is the highest in case of -----(incandescent lamp)
96. In carbon arc welding---(Electrode is positive with respect to work in case of dc supply)
97. Rolling electrodes are specifically used for---( seam welding)
98. In resistance furnace, the atmosphere is----------(oxidizing)
99. Which of the following motors can be used for unity power factor---------(Schrage motor)
100. The least expensive drive is------(belt drive)

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