1) A unity feedback system has open loop transfer function G(S)=K(s+1.1)(s+2.2)/s(s+3.3)(s+4.4). For K=0 the closed loop poles are
(A) All real and distinct
(B) One real and two complex conjugate
(C) All real and repeated
(D) Complex and non repeated
Ans:A
2) A unit impulse input to a linear network has a response R(t) and a unit Step input to the same network has response S(t). The response R(t)
(A) equals to dS(t)/d(t)
(B) equals to integral of S(t)
(C) is the reciprocal of S(t)
(D) has no relation with S(t)
Ans:A
3) Phantom loading for testing of energy meter is used
(A) to isolate the current and potential circuits
(B) to increase power loss during testing
(C) for meters having low current ratings
(D) to test meters having a large current rating for which loads may not be available
Ans:D
4) Ratio of rotor reactance X and rotor resistance R for two phase servo motor
(A) is equal to that of a normal induction motor
(B) is less than that of a normal induction motor
(C) is greater than that of a normal induction motor
(D) may be lesser or greater than that of a normal induction motor
Ans:B
5) A TRIAC in a single phase circuit taking V volts and operating at a firing angle 𝝰 is supplying resistive load, R. The power loss in the load is
(A) 2V^2/𝛱R (sin 2𝛂)/2
(B) V^2/𝛱R (cos 2𝛂)/2
(C) V^2/𝛱R ⦗𝛱- 𝛂+(sin 2𝛂)/2⦘
(D) V^2/𝛱R ⦗𝛱- 𝛂-(sin 2𝛂)/2⦘
Ans:C
6) In a boost chopper circuit if Vs,Vo ,L are input voltage, output voltage and inductance, respectively and when the conducting switch opened the rate of change of inductive current is
(A) Vs/L
(B) Vo/L
(C) Vs-Vo/L
(D) Vs+Vo/L
Ans:C
7) In a 3 phase converter circuit during commutation when one scr in one phase is turned on to turn off an scr in another phase , results in
(A) voltage notching
(B) harmonic distortion
(C) voltage sag
(D) voltage swell
Ans:A
8) A snubber circuit is connected to the power semiconductor device to reduce the
(A) turn on time
(B) turn off time
(C) electrical stresses
(D) thermal resistance
Ans:C
9)Which phenomenon is present in thyristor but absent in BJT, MOSFET, and IGBT?
(A) forward conduction
(B) latching
(C) forward blocking
(D) reverse breakdown
Ans:B
10) The 5th harmonic component of induced voltage in a 3-phase alternator can be completely eliminated by using a winding pitch of
(A) 2/3
(B) 4/5
(C) 5/6
(D) 6/7
Ans:B
11) In an adjustable speed ac drive which quantity gets reduced above rated speed?
(A) developed torque
(B) stator frequency
(C) reduced starting torque
(D) stator current
Ans:A
12) RC triggering is preferred over resistance triggering because
(A) it provides triggering at a precise instant
(B) it gives longer duration gate pulse
(C) it enables triggering at a larger value of firing angle
(D) it protects the SCR against high dv/dt
Ans:C
13) A moving coil meter has a resistance of 3 ohms and gives full scale deflection with 30 mA. To measure voltage upto 300V, the external resistance to be connected in series with the instrument is
(A) 9997 𝛀
(B) 10000 𝛀
(C) 997 𝛀
(D) 10003 𝛀
Ans:A
14) A pmmc instrument has FSD of 100 𝜇A and a coil resistance of 1K𝛀 To convert instrument into a ammeter with full scale deflection of 100 mA, the required shunt resistance
(A) 1 𝛀
(B) 1.001 𝛀
(C) 0.5 𝛀
(D) 10 𝛀
Ans:B
15) When measuring insulating resistance of cables using d.c source, the galvanometer used should be initially short circuited because
(A) Cables have a low value of capacitance which draws a high value of charging current
(B) Cables have a low value of initial resistance
(C) Cables have a high value of capacitance which draws a high value of charging current
(D) Cables have a low value of capacitance and initial resistance
Ans:C
16) The self inductance of a coil can be measured using
(A) Wien's bridge
(B) schering bridge
(C) Anderson's bridge
(D) Wheatstone bridge
Ans:C
17) A 200 V, 5 A d.c energy meter is tested at its marked ratings. The resistance of the pressure circuit is 8000 𝛀 and that of a current coil is 0.1 𝛀. The power consumed when testing the meter with phantom loading with current circuit excited by a 6 V battery is
(A) 2.5 W
(B) 5 W
(C) 32.5 W
(D) 35 W
Ans:D
18) A system shows zero steady state error for step input, finite steady state error for Ramp input and infinite steady state error for parabolic input. Then the system is of
(A) Type-0
(B) Type-1
(C) Type-2
(D) Type-3
Ans:B
19) After drawing the Root Locus, the closed loop poles corresponding to a specified value of gain K can be determined from which of the following criterion?
(A) Magnitude criterion alone
(B) Angle criterion alone
(C) Both Magnitude and Angle criteria
(D) Angle of departure and angle of arrival
Ans:A
20) The open loop transfer function of a unity feed back system is given by
G(S)=K(s+13)/s(s+3)(s+7)
The allowable maximum value of K for the closed loop system to remain stable is
(A) 50
(B) 60
(C) 70
(D) 80
Ans:C
21) The frequencies and voltages used in Dielectric heating are
(A) 0 - 30 MHz, upto 25 KV
(B) 50 - 60 Hz, upto 25 KV
(C) 0 - 30 MHz, upto 100 KV
(D) 50 - 60 Hz, upto 110 V - 230 V
Ans:A
22) Trapezoidal speed-time curve is
(A) an exact representation of the conditions in Main-line traction service.
(B) an exact representation of the conditions in suburban traction service.
(C) a close approximation of the conditions in suburban traction service.
(D) a close approximation of the conditions in Main-line traction service.
Ans:D
23) Pantograph is
(A) a device used to draw Speed-Time characteristics in traction.
(B) used to supply a.c. to transformer in locomotive.
(C) a part of the control devices in locomotives.
(D) used in traction motors for better efficiency.
Ans:B
24) With reference to Fig.1 which of the following is neither ZA nor ZB nor ZC?
(A) 10+j7.5
(B) 30-j40
(C) 20+j15
(D) 10+j15
Ans:D
25) A network is said to be under resonance when the voltages and the current at the network input terminals are
(A) in phase
(B) out of phase
(C) in phase quadrature
(D) in phase, and have equal magnitudes
Ans:A
26) The internal resistance of an ideal voltage source is
(A) Infinity
(B) Zero
(C) Very small approaching zero
(D) Very large approaching infinity
Ans:B
27) The time period of third harmonic of power supply frequency, in milli seconds is
(A) 20
(B) 3.33
(C) 6.66
(D) 60
Ans:C
28) The power consumed by a balanced 3-ph load is measured by two-wattmeter method. The meter readings are 8 KW and 4 KW. The power factor of the load is
(A) zero
(B) 0.5
(C) between zero and 0.5
(D) between 0.5 and unity
Ans:D
29) Which of the following statements is Incorrect?
(A) Superposition theorem is useful for linear and Non-linear circuit analysis when several sources are present in the circuit.
(B) Thevenin's equivalent network consists of one voltage source in series with an impedence.
(C) Norton's equivalent network consists of one current source in parallel with an impedence.
(D) When both the load and source impedences are purely resistive, maximum power transfer is achieved under the condition: Load Resistive = Source Resistance
Ans:A
30) The main purpose of using core in a transformer is to
(A) decrease iron losses
(B) eliminate magnetic hysterisis
(C) reduce reluctance of the common magnetic circuit
(D) prevent eddy current loss
Ans:C
31) A 220V separately excited dc motor takes 20 A and the armature resistance is 1.0 𝛀. If the armature constant Ka𝚽=1.5 rad/sec, the speed of the motor is
(A) 1000 rpm
(B) 2000/𝚷 rpm
(C) 3000/𝚷 rpm
(D) 4000/𝚷 rpm
Ans:D
32) In a 3-phase slip-ring induction motor, the slip at some speed is 0.05. The speed is reduced by inserting an external resistance in the rotor circuit and the slip is 0.15. If the rotor winding resistance per phase is 0.2 𝛀, the external resistance is
(A) 0.2 𝛀
(B) 0.3 𝛀
(C) 0.4 𝛀
(D) 0.5 𝛀
Ans:C
33) When a V-V three phase transformer is converted into a 𝚫-𝚫 system, increase in capacity of the system is
(A) 86.6%
(B) 50%
(C) 57.7%
(D) 73.2%
Ans:D
34) 3KW load is supplied by an autotransformer with 0.7 transformation ratio. Conductively transfered power from primary to secondary is
(A) 2.1 KW
(B) 0.9 KW
(C) 4.29 KW
(D) 3 KW
Ans:A
35) Number of commutator bars for a 4-pole, 2-layer, DC lap winding with 24 slots and one conductor per layer is
(A) 48
(B) 24
(C) 192
(D) 96
Ans:B
36) The torque developed by any 3-phase induction motor at 0.8 p.u slip is
(A) Full-load torque
(B) unstable torque
(C) starting torque
(D) break down
Ans:B
37) The Eb/V ratio of a DC motor is an indication of its--------.(Eb is the back emf and V is the applied voltage across the armature)
(A) Speed regulation
(B) Starting torque
(C) Efficiency
(D) Running torque
Ans:C
38) Which of the following test is usually conducted to determine the efficiency of traction motors?
(A) Field's test
(B) Swinburne's test
(C) Hopkinson's test
(D) Retardation test
Ans:A
39) An 8-pole, 50Hz, three-phase induction motor is running at 705 rpm and has a rotor copper loss of 5 KW. Its rotor input is
(A) 5.06 KW
(B) 0.3 KW
(C) 100 KW
(D) 83.33 KW
Ans:D
40) A 3-phase, 4-pole, 50Hz induction motor runs at a speed of 1440 rpm. The rotating field produced by the rotor rotates at a speed of -------rpm with respect to stator field.
(A) 1500
(B) 0
(C) 1440
(D) 60
Ans:B
41) Generally, Crawling in squirrel cage induction motor is tendency to run stably at speeds as low as
(A) One-third of their synchronous speed
(B) One-fifth of their synchronous speed
(C) One-seventh of their synchronous speed
(D) One-ninth of their synchronous speed
Ans:C
42) The starting torque of a capacitor-start induction-run motor is directly related to the angle 𝚹 between its two winding currents by the relation
(A) cos𝚹
(B) sin𝚹
(C) tan𝚹
(D) sin𝚹 /2
Ans:B
43) The fractional pitch used for eliminating 7th harmonic from the emf wave of an alternator is
(A) 2/3
(B) 5/6
(C) 7/8
(D) 6/7
Ans:D
44) A 2-pole, 50 Hz, 3-phase, 100 MVA, 33KV turbo alternator connected to an infinite bus has a moment of inertia of 10^7 kg-m2 in its rotating parts. Its has a synchronous reactance of 0.5 p.u. The natural time period of oscillations of the machine is
(A) 7.874 sec
(B) 15.748 sec
(C) 23.622 sec
(D) 24.9 sec
Ans:D
45) While keeping the excitation constant, if the steam supply of an alternator running in parallel with another identical alternator is increased, then
(A) It would over-run the other alternator
(B) Its rotor will fall back in phase with respect to the other machine
(C) Its portion of share in load will increase
(D) Its power factor would be decreased.
Ans:C
46) The effect of increasing load on a synchronous motor running with normal excitation is
(A) Increase both its Ia and power factor
(B) Decrease Ia, but increase power factor
(C) Increase Ia, but decrease power factor
(D) Decrease both Ia and power factor.
Ans:C
47)Transmission lines are transposed to reduce
(A) Ferranti effect and voltage level
(B) Skin effect and efficiency
(C) Proximity effect and current density
(D) Interference with neighboring communication lines
Ans:D
48) If the base current and base voltage of a 345 KV system are 3000A and 300 KV respectively, per-unit voltage and base impedence of the system respectively are
(A) 1.15 pu, 115 𝛀
(B) 1.15 pu, 100 𝛀
(C) 0.87 pu, 115 𝛀
(D) 0.87 pu, 100 𝛀
Ans:B
49) The surge impedence of a 60 miles long under ground cable is 50 𝛀. For a 30 miles length it will be
(A) 25 𝛀
(B) 50 𝛀
(C) 100 𝛀
(D) 200 𝛀
Ans:B
50) A single core cable is designed to work for a single phase system with a peak voltage of 220 KV. The maximum permissible stress in the dielectric is not to exceed 20 KV/mm. For economical size, the over all core diameter of the cable is
(A) 28.2 mm
(B) 26.4 mm
(C) 24.4 mm
(D) 22.0 mm
Ans:A
51) Stringing chart is used for
(A) finding the sag in the conductor
(B) the design of towers
(C) the design of insulator string
(D) finding the distance between towers
Ans:A
52) A suspension type insulator has 2 units with self capacitance C and ground capacitance of 0.2 C. Each unit can withstand for a maximum voltage of 11KV. Its string efficiency is
(A) 78%
(B) 82%
(C) 80%
(D) 84%
Ans:B
53) If a 5-bus test system contains 6 transmission lines and one transformer, how many non-zero elements are there in the system Y-bus?
(A) 25
(B) 12
(C) 11
(D) 19
Ans:D
54) The voltages of a generator and an Infinite bus are given as 0.92∠10 and 1.0∠0 respectively. Which of the following statement is correct?
(A) Active power flows from generator to infinite bus and reactive power flows from Infinite bus to generator
(B) Active power and reactive power flows from generator to Infinite bus.
(C) Reactive power flows from generator to Infinite bus and active power flows from Infinite bus to generator
(D)Active power and reactive power flows from Infinite bus to generator.
Ans:A
55) A shunt fault is characterized by
(A) Increase in current, frequency and pf
(B) Increase in current, reduction in frequency and pf
(C) Increase in current and frequency, reduction in pf
(D) Decrease in current and frequency.
Ans:B
56) A reactance relay is
(A) Voltage restrained directional relay
(B) directional restrained over-current relay
(C) Voltage restrained over current relay
(D) Directional restrained over voltage relay
Ans:B
57) In a 132 KV system, the line to ground capacitance is 0.01𝜇F and the inductance is 4 H. what is value of voltage appearing across the CB pole, if the magnetizing current to be interrupted is 5A(instantaneous)?
(A) 132 KV
(B) 10 KV
(C) 220 KV
(D) 100 KV
Ans:D
58) The inertia constants of two groups of machines, which swing together are M1 and M2.
The inertia constant of the system is
(A) M1M2/(M1+M2)
(B) M1-M2, M1>M2
(C) M1+M2
(D) M1+M2/M1M2
Ans:C
59) The per unit synchronous reactance of a machine is 1.6 pu. Its Short Circuit Ratio is
(A) 1.6
(B) 3.2
(C) 0.8
(D) 0.625
Ans:D
60) Precise control of reactive current flow entering the transmission and disturbing systems can be minimized by using
(A) synchronous condenser
(B) static VAR capacitor
(C) capacitor bank
(D) thyristor switched reactor in parallel with capacitor
Ans:B
61) The sending end and receiving end voltages of a three-phase transmission line are 10 KV/ph and 9.5 KV/ph, respectively. If the resistance drop is 150 V/ph and receiving end power factor is 0.8, the sending end power factor is
(A) 0.745 lagging
(B) 0.775 lagging
(C) 0.8 lagging
(D) 0.85 lagging
Ans:B
62) A dc distributor of length, ℓ m and resistance r ohm/m, fed at both ends with equal voltages, is uniformly loaded with i A/m run. The power loss in the distributor is
(A) (𝑖^2r𝑙^3)/3
(B) (𝑖^2r𝑙^3)/4
(C) (𝑖^2r𝑙^3)/8
(D) (𝑖^2r𝑙^3)/12
Ans:D
63) Corona losses in transmission lines can be reduced by
(A) using small diameter conductors
(B) using bundled conductors
(C) using less spacing between conductors
(D) increasing the transmission line voltage
Ans:B
64) A 4000 KVA, 11KV/132 KV delta-star connected 3-phase transformer has reactance, X1=0.12 p.u. The actual value of X1 referred to the low voltage side is
(A) 0.85 𝛀
(B) 3.63 𝛀
(C) 36.3 𝛀
(D) 252 𝛀
Ans:B
65) The number of comparators required in a 4-bit comparator type ADC is
(A) 16
(B) 15
(C) 17
(D) 12
Ans:B
66) In a 5-bit weighted resistor D/A converters, the resistor value corresponding to LSB is 40 K𝛀, the resistor value corresponding to MSB will be
(A) 0.4 K𝛀
(B) 3 K𝛀
(C) 2.8 K𝛀
(D) 2.5 K𝛀
Ans:D
67) A switch tail ring counter is made by using a single D-FF. The resulting circuit is
(A) T-FF
(B) D-FF
(C) SR-FF
(D) JK-FF
Ans:A
68) The ALE line of an 8085 microprocessor is used to
(A) latch the output of an I/O instruction into an external latch.
(B) deactivate the chip-select signal from memory devices
(C) find the interrupt enable states of the TRAP interrupt.
(D) latch the 8 bits of address lines AD7-AD0 into an external latch.
Ans:D
69) Which diode exhibits negative resistance characteristic?
(A) LED
(B) Zener
(C) Tunnel diode
(D) PN diode
Ans:C
70) A closed-loop transfer function of a unity feed back system is given by Y(s)/R(s)=𝛚n^2/(s^2+2𝛏𝛚ns+𝛚n^2)
The System Kv is given by
(A) 𝛚n/2𝛏
(B) 1
(C) infinity
(D) 2𝛏/𝛚n
Ans:A
This is question paper for aptransco assistant engineer 2017 if you found it useful please share and subscribe. If you found mistakes in this post please comment here.
(A) All real and distinct
(B) One real and two complex conjugate
(C) All real and repeated
(D) Complex and non repeated
Ans:A
2) A unit impulse input to a linear network has a response R(t) and a unit Step input to the same network has response S(t). The response R(t)
(A) equals to dS(t)/d(t)
(B) equals to integral of S(t)
(C) is the reciprocal of S(t)
(D) has no relation with S(t)
Ans:A
3) Phantom loading for testing of energy meter is used
(A) to isolate the current and potential circuits
(B) to increase power loss during testing
(C) for meters having low current ratings
(D) to test meters having a large current rating for which loads may not be available
Ans:D
4) Ratio of rotor reactance X and rotor resistance R for two phase servo motor
(A) is equal to that of a normal induction motor
(B) is less than that of a normal induction motor
(C) is greater than that of a normal induction motor
(D) may be lesser or greater than that of a normal induction motor
Ans:B
5) A TRIAC in a single phase circuit taking V volts and operating at a firing angle 𝝰 is supplying resistive load, R. The power loss in the load is
(A) 2V^2/𝛱R (sin 2𝛂)/2
(B) V^2/𝛱R (cos 2𝛂)/2
(C) V^2/𝛱R ⦗𝛱- 𝛂+(sin 2𝛂)/2⦘
(D) V^2/𝛱R ⦗𝛱- 𝛂-(sin 2𝛂)/2⦘
Ans:C
6) In a boost chopper circuit if Vs,Vo ,L are input voltage, output voltage and inductance, respectively and when the conducting switch opened the rate of change of inductive current is
(A) Vs/L
(B) Vo/L
(C) Vs-Vo/L
(D) Vs+Vo/L
Ans:C
7) In a 3 phase converter circuit during commutation when one scr in one phase is turned on to turn off an scr in another phase , results in
(A) voltage notching
(B) harmonic distortion
(C) voltage sag
(D) voltage swell
Ans:A
8) A snubber circuit is connected to the power semiconductor device to reduce the
(A) turn on time
(B) turn off time
(C) electrical stresses
(D) thermal resistance
Ans:C
9)Which phenomenon is present in thyristor but absent in BJT, MOSFET, and IGBT?
(A) forward conduction
(B) latching
(C) forward blocking
(D) reverse breakdown
Ans:B
10) The 5th harmonic component of induced voltage in a 3-phase alternator can be completely eliminated by using a winding pitch of
(A) 2/3
(B) 4/5
(C) 5/6
(D) 6/7
Ans:B
11) In an adjustable speed ac drive which quantity gets reduced above rated speed?
(A) developed torque
(B) stator frequency
(C) reduced starting torque
(D) stator current
Ans:A
12) RC triggering is preferred over resistance triggering because
(A) it provides triggering at a precise instant
(B) it gives longer duration gate pulse
(C) it enables triggering at a larger value of firing angle
(D) it protects the SCR against high dv/dt
Ans:C
13) A moving coil meter has a resistance of 3 ohms and gives full scale deflection with 30 mA. To measure voltage upto 300V, the external resistance to be connected in series with the instrument is
(A) 9997 𝛀
(B) 10000 𝛀
(C) 997 𝛀
(D) 10003 𝛀
Ans:A
14) A pmmc instrument has FSD of 100 𝜇A and a coil resistance of 1K𝛀 To convert instrument into a ammeter with full scale deflection of 100 mA, the required shunt resistance
(A) 1 𝛀
(B) 1.001 𝛀
(C) 0.5 𝛀
(D) 10 𝛀
Ans:B
15) When measuring insulating resistance of cables using d.c source, the galvanometer used should be initially short circuited because
(A) Cables have a low value of capacitance which draws a high value of charging current
(B) Cables have a low value of initial resistance
(C) Cables have a high value of capacitance which draws a high value of charging current
(D) Cables have a low value of capacitance and initial resistance
Ans:C
16) The self inductance of a coil can be measured using
(A) Wien's bridge
(B) schering bridge
(C) Anderson's bridge
(D) Wheatstone bridge
Ans:C
17) A 200 V, 5 A d.c energy meter is tested at its marked ratings. The resistance of the pressure circuit is 8000 𝛀 and that of a current coil is 0.1 𝛀. The power consumed when testing the meter with phantom loading with current circuit excited by a 6 V battery is
(A) 2.5 W
(B) 5 W
(C) 32.5 W
(D) 35 W
Ans:D
18) A system shows zero steady state error for step input, finite steady state error for Ramp input and infinite steady state error for parabolic input. Then the system is of
(A) Type-0
(B) Type-1
(C) Type-2
(D) Type-3
Ans:B
19) After drawing the Root Locus, the closed loop poles corresponding to a specified value of gain K can be determined from which of the following criterion?
(A) Magnitude criterion alone
(B) Angle criterion alone
(C) Both Magnitude and Angle criteria
(D) Angle of departure and angle of arrival
Ans:A
20) The open loop transfer function of a unity feed back system is given by
G(S)=K(s+13)/s(s+3)(s+7)
The allowable maximum value of K for the closed loop system to remain stable is
(A) 50
(B) 60
(C) 70
(D) 80
Ans:C
21) The frequencies and voltages used in Dielectric heating are
(A) 0 - 30 MHz, upto 25 KV
(B) 50 - 60 Hz, upto 25 KV
(C) 0 - 30 MHz, upto 100 KV
(D) 50 - 60 Hz, upto 110 V - 230 V
Ans:A
22) Trapezoidal speed-time curve is
(A) an exact representation of the conditions in Main-line traction service.
(B) an exact representation of the conditions in suburban traction service.
(C) a close approximation of the conditions in suburban traction service.
(D) a close approximation of the conditions in Main-line traction service.
Ans:D
23) Pantograph is
(A) a device used to draw Speed-Time characteristics in traction.
(B) used to supply a.c. to transformer in locomotive.
(C) a part of the control devices in locomotives.
(D) used in traction motors for better efficiency.
Ans:B
24) With reference to Fig.1 which of the following is neither ZA nor ZB nor ZC?
(A) 10+j7.5
(B) 30-j40
(C) 20+j15
Ans:D
25) A network is said to be under resonance when the voltages and the current at the network input terminals are
(A) in phase
(B) out of phase
(C) in phase quadrature
(D) in phase, and have equal magnitudes
Ans:A
26) The internal resistance of an ideal voltage source is
(A) Infinity
(B) Zero
(C) Very small approaching zero
(D) Very large approaching infinity
Ans:B
27) The time period of third harmonic of power supply frequency, in milli seconds is
(A) 20
(B) 3.33
(C) 6.66
(D) 60
Ans:C
28) The power consumed by a balanced 3-ph load is measured by two-wattmeter method. The meter readings are 8 KW and 4 KW. The power factor of the load is
(A) zero
(B) 0.5
(C) between zero and 0.5
(D) between 0.5 and unity
Ans:D
29) Which of the following statements is Incorrect?
(A) Superposition theorem is useful for linear and Non-linear circuit analysis when several sources are present in the circuit.
(B) Thevenin's equivalent network consists of one voltage source in series with an impedence.
(C) Norton's equivalent network consists of one current source in parallel with an impedence.
(D) When both the load and source impedences are purely resistive, maximum power transfer is achieved under the condition: Load Resistive = Source Resistance
Ans:A
30) The main purpose of using core in a transformer is to
(A) decrease iron losses
(B) eliminate magnetic hysterisis
(C) reduce reluctance of the common magnetic circuit
(D) prevent eddy current loss
Ans:C
31) A 220V separately excited dc motor takes 20 A and the armature resistance is 1.0 𝛀. If the armature constant Ka𝚽=1.5 rad/sec, the speed of the motor is
(A) 1000 rpm
(B) 2000/𝚷 rpm
(C) 3000/𝚷 rpm
(D) 4000/𝚷 rpm
Ans:D
32) In a 3-phase slip-ring induction motor, the slip at some speed is 0.05. The speed is reduced by inserting an external resistance in the rotor circuit and the slip is 0.15. If the rotor winding resistance per phase is 0.2 𝛀, the external resistance is
(A) 0.2 𝛀
(B) 0.3 𝛀
(C) 0.4 𝛀
(D) 0.5 𝛀
Ans:C
33) When a V-V three phase transformer is converted into a 𝚫-𝚫 system, increase in capacity of the system is
(A) 86.6%
(B) 50%
(C) 57.7%
(D) 73.2%
Ans:D
34) 3KW load is supplied by an autotransformer with 0.7 transformation ratio. Conductively transfered power from primary to secondary is
(A) 2.1 KW
(B) 0.9 KW
(C) 4.29 KW
(D) 3 KW
Ans:A
35) Number of commutator bars for a 4-pole, 2-layer, DC lap winding with 24 slots and one conductor per layer is
(A) 48
(B) 24
(C) 192
(D) 96
Ans:B
36) The torque developed by any 3-phase induction motor at 0.8 p.u slip is
(A) Full-load torque
(B) unstable torque
(C) starting torque
(D) break down
Ans:B
37) The Eb/V ratio of a DC motor is an indication of its--------.(Eb is the back emf and V is the applied voltage across the armature)
(A) Speed regulation
(B) Starting torque
(C) Efficiency
(D) Running torque
Ans:C
38) Which of the following test is usually conducted to determine the efficiency of traction motors?
(A) Field's test
(B) Swinburne's test
(C) Hopkinson's test
(D) Retardation test
Ans:A
39) An 8-pole, 50Hz, three-phase induction motor is running at 705 rpm and has a rotor copper loss of 5 KW. Its rotor input is
(A) 5.06 KW
(B) 0.3 KW
(C) 100 KW
(D) 83.33 KW
Ans:D
40) A 3-phase, 4-pole, 50Hz induction motor runs at a speed of 1440 rpm. The rotating field produced by the rotor rotates at a speed of -------rpm with respect to stator field.
(A) 1500
(B) 0
(C) 1440
(D) 60
Ans:B
41) Generally, Crawling in squirrel cage induction motor is tendency to run stably at speeds as low as
(A) One-third of their synchronous speed
(B) One-fifth of their synchronous speed
(C) One-seventh of their synchronous speed
(D) One-ninth of their synchronous speed
Ans:C
42) The starting torque of a capacitor-start induction-run motor is directly related to the angle 𝚹 between its two winding currents by the relation
(A) cos𝚹
(B) sin𝚹
(C) tan𝚹
(D) sin𝚹 /2
Ans:B
43) The fractional pitch used for eliminating 7th harmonic from the emf wave of an alternator is
(A) 2/3
(B) 5/6
(C) 7/8
(D) 6/7
Ans:D
44) A 2-pole, 50 Hz, 3-phase, 100 MVA, 33KV turbo alternator connected to an infinite bus has a moment of inertia of 10^7 kg-m2 in its rotating parts. Its has a synchronous reactance of 0.5 p.u. The natural time period of oscillations of the machine is
(A) 7.874 sec
(B) 15.748 sec
(C) 23.622 sec
(D) 24.9 sec
Ans:D
45) While keeping the excitation constant, if the steam supply of an alternator running in parallel with another identical alternator is increased, then
(A) It would over-run the other alternator
(B) Its rotor will fall back in phase with respect to the other machine
(C) Its portion of share in load will increase
(D) Its power factor would be decreased.
Ans:C
46) The effect of increasing load on a synchronous motor running with normal excitation is
(A) Increase both its Ia and power factor
(B) Decrease Ia, but increase power factor
(C) Increase Ia, but decrease power factor
(D) Decrease both Ia and power factor.
Ans:C
47)Transmission lines are transposed to reduce
(A) Ferranti effect and voltage level
(B) Skin effect and efficiency
(C) Proximity effect and current density
(D) Interference with neighboring communication lines
Ans:D
48) If the base current and base voltage of a 345 KV system are 3000A and 300 KV respectively, per-unit voltage and base impedence of the system respectively are
(A) 1.15 pu, 115 𝛀
(B) 1.15 pu, 100 𝛀
(C) 0.87 pu, 115 𝛀
(D) 0.87 pu, 100 𝛀
Ans:B
49) The surge impedence of a 60 miles long under ground cable is 50 𝛀. For a 30 miles length it will be
(A) 25 𝛀
(B) 50 𝛀
(C) 100 𝛀
(D) 200 𝛀
Ans:B
50) A single core cable is designed to work for a single phase system with a peak voltage of 220 KV. The maximum permissible stress in the dielectric is not to exceed 20 KV/mm. For economical size, the over all core diameter of the cable is
(A) 28.2 mm
(B) 26.4 mm
(C) 24.4 mm
(D) 22.0 mm
Ans:A
51) Stringing chart is used for
(A) finding the sag in the conductor
(B) the design of towers
(C) the design of insulator string
(D) finding the distance between towers
Ans:A
52) A suspension type insulator has 2 units with self capacitance C and ground capacitance of 0.2 C. Each unit can withstand for a maximum voltage of 11KV. Its string efficiency is
(A) 78%
(B) 82%
(C) 80%
(D) 84%
Ans:B
53) If a 5-bus test system contains 6 transmission lines and one transformer, how many non-zero elements are there in the system Y-bus?
(A) 25
(B) 12
(C) 11
(D) 19
Ans:D
54) The voltages of a generator and an Infinite bus are given as 0.92∠10 and 1.0∠0 respectively. Which of the following statement is correct?
(A) Active power flows from generator to infinite bus and reactive power flows from Infinite bus to generator
(B) Active power and reactive power flows from generator to Infinite bus.
(C) Reactive power flows from generator to Infinite bus and active power flows from Infinite bus to generator
(D)Active power and reactive power flows from Infinite bus to generator.
Ans:A
55) A shunt fault is characterized by
(A) Increase in current, frequency and pf
(B) Increase in current, reduction in frequency and pf
(C) Increase in current and frequency, reduction in pf
(D) Decrease in current and frequency.
Ans:B
56) A reactance relay is
(A) Voltage restrained directional relay
(B) directional restrained over-current relay
(C) Voltage restrained over current relay
(D) Directional restrained over voltage relay
Ans:B
57) In a 132 KV system, the line to ground capacitance is 0.01𝜇F and the inductance is 4 H. what is value of voltage appearing across the CB pole, if the magnetizing current to be interrupted is 5A(instantaneous)?
(A) 132 KV
(B) 10 KV
(C) 220 KV
(D) 100 KV
Ans:D
58) The inertia constants of two groups of machines, which swing together are M1 and M2.
The inertia constant of the system is
(A) M1M2/(M1+M2)
(B) M1-M2, M1>M2
(C) M1+M2
(D) M1+M2/M1M2
Ans:C
59) The per unit synchronous reactance of a machine is 1.6 pu. Its Short Circuit Ratio is
(A) 1.6
(B) 3.2
(C) 0.8
(D) 0.625
Ans:D
60) Precise control of reactive current flow entering the transmission and disturbing systems can be minimized by using
(A) synchronous condenser
(B) static VAR capacitor
(C) capacitor bank
(D) thyristor switched reactor in parallel with capacitor
Ans:B
61) The sending end and receiving end voltages of a three-phase transmission line are 10 KV/ph and 9.5 KV/ph, respectively. If the resistance drop is 150 V/ph and receiving end power factor is 0.8, the sending end power factor is
(A) 0.745 lagging
(B) 0.775 lagging
(C) 0.8 lagging
(D) 0.85 lagging
Ans:B
62) A dc distributor of length, ℓ m and resistance r ohm/m, fed at both ends with equal voltages, is uniformly loaded with i A/m run. The power loss in the distributor is
(A) (𝑖^2r𝑙^3)/3
(B) (𝑖^2r𝑙^3)/4
(C) (𝑖^2r𝑙^3)/8
(D) (𝑖^2r𝑙^3)/12
Ans:D
63) Corona losses in transmission lines can be reduced by
(A) using small diameter conductors
(B) using bundled conductors
(C) using less spacing between conductors
(D) increasing the transmission line voltage
Ans:B
64) A 4000 KVA, 11KV/132 KV delta-star connected 3-phase transformer has reactance, X1=0.12 p.u. The actual value of X1 referred to the low voltage side is
(A) 0.85 𝛀
(B) 3.63 𝛀
(C) 36.3 𝛀
(D) 252 𝛀
Ans:B
65) The number of comparators required in a 4-bit comparator type ADC is
(A) 16
(B) 15
(C) 17
(D) 12
Ans:B
66) In a 5-bit weighted resistor D/A converters, the resistor value corresponding to LSB is 40 K𝛀, the resistor value corresponding to MSB will be
(A) 0.4 K𝛀
(B) 3 K𝛀
(C) 2.8 K𝛀
(D) 2.5 K𝛀
Ans:D
67) A switch tail ring counter is made by using a single D-FF. The resulting circuit is
(A) T-FF
(B) D-FF
(C) SR-FF
(D) JK-FF
Ans:A
68) The ALE line of an 8085 microprocessor is used to
(A) latch the output of an I/O instruction into an external latch.
(B) deactivate the chip-select signal from memory devices
(C) find the interrupt enable states of the TRAP interrupt.
(D) latch the 8 bits of address lines AD7-AD0 into an external latch.
Ans:D
69) Which diode exhibits negative resistance characteristic?
(A) LED
(B) Zener
(C) Tunnel diode
(D) PN diode
Ans:C
70) A closed-loop transfer function of a unity feed back system is given by Y(s)/R(s)=𝛚n^2/(s^2+2𝛏𝛚ns+𝛚n^2)
The System Kv is given by
(A) 𝛚n/2𝛏
(B) 1
(C) infinity
(D) 2𝛏/𝛚n
Ans:A
This is question paper for aptransco assistant engineer 2017 if you found it useful please share and subscribe. If you found mistakes in this post please comment here.
2 comments
Write commentsQuestion no.64 has no correct answer in that options....the correct answer is 10.89 ohms....
Replythank you for your comment friend, but ans is 3.63 only. they have given x1 in per unit and we have to convert to ohms. thats it... please check out again.
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