This is the question paper of Apgenco conducted in April 2017..check out this questions.
1) The unit time step response of a system is given by c (t)=4+3t-4e^-t. The system has following poles and zeros.
(A) one pole at origin, one pole at -1, and one zero at -3/7
(B) one pole at origin, one pole at -3/7, one zero at -1
(C) one pole at -4, two poles at -3/7 and 4
(D) one zero at 4, two poles at -3/7 and 4
Ans:A
2) A type-2 system has zero steady-state error for
(A) Ramp input
(B) parabolic input
(C) Both Ramp and parabolic inputs
(D) step input only
Ans:A
3) The closed loop transfer function of a system is 10/S ((S+3)(S+4)+K)
The system is stable for
(A) Any value of K
(B) No value of K
(C) K=10
(D) K between 3 and 12.
Ans:B
4) Which statement is Incorrect in relation to NYQUIST and BODE analyses?
(A) Number of closed loop poles in the right half s-plane can be determined using Nyquist Criterion.
(B) BODE analysis uses two plots, one for magnitude and another for phase angle.
(C) Nyquist analysis uses two plots, one for magnitude and another for phase angle.
(D) Relative stability can be assessed from both Nyquist and Bode analyses.
Ans:C
5) Which of the following is CORRECT with respect to a LAG-LEAD compensator?
(A) It is similar to PI-Controller
(B) It acts as Band pass filter
(C) It is second order system with one zero and two poles
(D) It acts as a Band reject filter
Ans:B
6) Whether a given point in the S-plane lies on the root locus of a system can be determined by
(A) Magnitude criterion
(B) Angle criterion
(C) Both Magnitude and Angle criteria
(D) Break-in and Break-away criteria
Ans:B
1) The unit time step response of a system is given by c (t)=4+3t-4e^-t. The system has following poles and zeros.
(A) one pole at origin, one pole at -1, and one zero at -3/7
(B) one pole at origin, one pole at -3/7, one zero at -1
(C) one pole at -4, two poles at -3/7 and 4
(D) one zero at 4, two poles at -3/7 and 4
Ans:A
2) A type-2 system has zero steady-state error for
(A) Ramp input
(B) parabolic input
(C) Both Ramp and parabolic inputs
(D) step input only
Ans:A
3) The closed loop transfer function of a system is 10/S ((S+3)(S+4)+K)
The system is stable for
(A) Any value of K
(B) No value of K
(C) K=10
(D) K between 3 and 12.
Ans:B
4) Which statement is Incorrect in relation to NYQUIST and BODE analyses?
(A) Number of closed loop poles in the right half s-plane can be determined using Nyquist Criterion.
(B) BODE analysis uses two plots, one for magnitude and another for phase angle.
(C) Nyquist analysis uses two plots, one for magnitude and another for phase angle.
(D) Relative stability can be assessed from both Nyquist and Bode analyses.
Ans:C
5) Which of the following is CORRECT with respect to a LAG-LEAD compensator?
(A) It is similar to PI-Controller
(B) It acts as Band pass filter
(C) It is second order system with one zero and two poles
(D) It acts as a Band reject filter
Ans:B
6) Whether a given point in the S-plane lies on the root locus of a system can be determined by
(A) Magnitude criterion
(B) Angle criterion
(C) Both Magnitude and Angle criteria
(D) Break-in and Break-away criteria
Ans:B
7) The state equation of a system is X=AX+BU Where A= 1 0 The state transition matrix is
(A) te^t 0 (B) te^t 0 (C) e^-t 0 (D) e^t 0
e^t e^t e^-t e^-t te^-t e^-t te^t e^t
Ans:D
Ans:D
8)The pointer of a moving coil ammeter deflects from zero and comes to rest at 2A marking.In the steady deflected position
(A) Deflecting torque Td is zero
(B) Control torque Tc is zero
(C) Both Td and Tc are zero. Damping Torque Td is proportional to 2A
(D) Td=0
Ans:D
Ans:D
9)The potential coil of a single phase dynamometer wattmeter has 4840 ohms resistance. Voltage across the load is 220 V. With the Potential coil connected on load side, the meter indicates 100 W. Approximation percentage error due to wattmeter connection is
(A) 11%
(B) 9%
(C) 1.1%
(D) 3%
Ans:A
Ans:A
10) The disc of a single phase Induction-type energy meter makes 60 revolutions in 6 minutes. Meter Constant is 200 rev/KWh. Power consumption in the load is
(A) 1.2 KW
(B) 1 KW
(C) 600 W
(D) 500 W
Ans:D
Ans:D
11) Accurate measurement of very low resistance is possible with
(A) Megger
(B) Wheatstone Bridge
(C) Kelvin's Double Bridge
(D) Wagner's Earthing Device
Ans:C
Ans:C
12) Dielectric loss in a capacitor is best measured by
(A) Wein Bridge
(B) Schering Bridge
(C) Anderson Bridge
(D) Heaviside-Campbell Equal Ratio Bridge
Ans:B
Ans:B
13) The Transducer with negative temperature co-efficient of resistance is
(A) Thermistor
(B) Resistance thermometer
(C) Strain Gauge
(D) Thermocouple
Ans:A
Ans:A
14) D: Distance between Screen and the center of Deflection plates
ld: Distance between the deflection plates
l: Length of Deflection plates
Ea: Accelerating voltage
With the above notation, deflection sensitivity of a CRT using electrostatic method of deflection is given by
(A) 2Eal/Dld (B) Dl/2ldEa (C) Dld/2lEa (D) DEa/2lld
Ans:B
Ans:B
15) The primary turns of a 444V/222V, 50 HZ single phase transformer with a core cross sectional area of 100cm2 and a maximum flux density of 1.0T is
(A) 100 (B) 200 (C) 222 (D) 400
Ans:B
Ans:B
16) The condition for maximum regulation of a single phase transformer with equivalent resistance 𝓡eq, equivalent reactance 𝓧eq and load power factor angle is
(A) cos𝛷 = 𝓧eq/𝓡eq
(B) cos𝜙 = 𝓡eq/𝓧eq
(C) tan𝜙 = -𝓡eq/𝓧eq
(D) tan𝜙 = 𝓧eq/𝓡eq
Ans:D
(A) cos𝛷 = 𝓧eq/𝓡eq
(B) cos𝜙 = 𝓡eq/𝓧eq
(C) tan𝜙 = -𝓡eq/𝓧eq
(D) tan𝜙 = 𝓧eq/𝓡eq
Ans:D
17) The main application of delta/zig-zag connected 3-phase transformer is to supply
(A) balanced loads
(B) unbalanced loads
(C) furnace loads
(D) single-phase loads
Ans:B
18) Two transformers having the same p.u impedence connected in parallel share the connected load
(A) equally
(B) in proportion to the respective ratings
(C) in proportion to the voltage ratio
(D) in proportion to the zero phase displacement
Ans:B
19) A 1100KVA, 11KV/1.1KV conventional two-winding transformer is connected as a 12.1KV/11KV step-down auto-transformer. The rating of the auto-transformer is
(A) 1000 KVA
(B) 1100 KVA
(C) 11000 KVA
(D) 12100 KVA
Ans: D
20) The energy density of magnetic field in a magnetic circuit is
(A) inversely proportional to magnetic flux density
(B) directly proportional to the absolute permeability
(C) directly proportional to the magnetic flux density
(D) directly proportional to the square of magnetic flux density
Ans:D
21) A shunt generator develops stable output voltage if
(A) Magnetization characteristic is linear
(B) Magnetization characteristic is non-linear
(C) the field winding resistance is more than the critical resistance
(D) the residual magnetism is equal to zero
Ans:B
22) In a differentially compounded dc motor
(A) the speed is constant as the torque increases
(B) the speed falls non-linearly as the torque increases
(C) the speed increases non-linearly as the torque increases
(D) the flux increases as the load increases
Ans:C
23) A 3-phase induction motor under locked rotor condition and with stator supply induces
(A) small voltage at slip frequency
(B) large voltage at rotor frequency
(C) zero voltage at zero frequency
(D) large voltage at slip frequency
Ans:B
24) The equivalent rotor resistance, r2' components in the equivalent circuit of a single-phase inducton motor, based on two-revolving field theory, at any slip, s are
(A) r2'/s and r2'/1-s
(B) r2'/s and r2'/2-s
(C) r2'/2s and r2'/2(1-s)
(D) r2'/2s and r2'/2(2-s)
Ans:D
25) For a 210 MW, turbo-alternator in a thermal power plant, the possible specifications of rotor diameter, stator core length, and number of poles, respectively, are
(A) 4.4 m, 1.2 m, 12
(B) 1.2 m, 4.4 m, 2
(C) 4.4 m, 1.2 m, 24
(D) 1.2 m, 4.4 m, 8
Ans:B
26) The reluctance torque of a 3-phase salient pole synchronous generator with direct and quadrature axis reactance, xd and xq, respectively, is proportional to
(A) xd-xq
(B) xd*xq
(C) 1/xd-1/xq
(D) 1/xq-1/xd
Ans: D
27) When two alternators are operating in parallel, the cause for circulating current is
(A) increase in the excitation of one machine
(B) increase in the driving torque of one machine
(C) reduction in angular velocity of one machine
(D) identical speed/load characteristic of both machines
Ans:C
28) The maximum possible power of a 3-phase synchronous motor with synchronous reactance 0.8 p.u connected to a busbar of 1.0 pu and excitation adjusted to 1.2 pu is
(A) 0.5 p.u
(B) 0.96 p.u
(C) 1.5 p.u
(D) 1.8 p.u
Ans:C
29) A synchronous capacitor is
(A) an unloaded and under excited 3-phase synchronous motor
(B) a loaded and over excited 3-phase synchronous generator
(C) an unloaded and over excited 3-phase synchronous motor
(D) a 3-phase synchronous generator loaded with a capacitor bank
Ans:C
30) In the capacitor-start, capacitor-run single-phase induction motor
(A) two capacitors are connected across the main winding
(B) when the centrifugal switch opens, the permanent capacitor is left in the auxiliary winding circuit (C) when the centrifugal switch opens, the permanent capacitor is left in the main winding circuit
(D) two capacitors are connected across the auxiliary winding.
Ans:B
31) The main purpose of permanent magnet motors are
(A) to avoid the need for field supply
(B) to provide high flux density
(C) to provide control over flux level
(D) to faciliate KW rating
Ans:A
32) The average load voltage across a resistive load of a single-phase bride converter connected with two SCRs and two diodes, operating at any firing delay angle, and supplied at 200v, 50 HZ is
(A) 200/√2∏ × cos𝞪
(B) √2×200/∏ × cos𝞪
(C) √2×200/∏ × (1+cos𝞪)
(D) 200/√2∏×(1+sin𝞪)
Ans:C
33) In a dc-ac 3-phase MOSFET bridge inverter circuit, the switches are marked in a sequence as 1,2,3 in the top-half and 4,5,6 in the bottom half of the bridge. The triggering sequence of switches that gives balanced output voltage is
(A) 1,2,3,4,5,6
(B) 1,5,3,4,2,6
(C) 1,6,2,4,3,5
(D) 1,4,2,5,3,6
Ans:C
34) In a dc-dc converter, the switch duty ratio is defined as
(A) turn-off time/time period
(B) sawtooth voltage/control voltage
(C) control voltage/peak value of sawtooth voltage
(D) control voltage/sawtooth voltage
Ans:C
35) In a four-quadrant dc motor drive system controlled by two phase controlled converters, the current and voltage of converter 1 operating in I and IV quadrants, respectively are
(A) Ia -ve, Va +ve and Ia +ve,Va -ve
(B) Ia +ve, Va +ve and Ia +ve,Va -ve
(C) Ia -ve, Va +ve and Ia -ve,Va -ve
(D) Ia +ve, Va +ve and Ia -ve,Va -ve
Ans:B
36) In a 3-phase inverter fed induction motor drive the total harmonic distortion is 4%. If the maximum value of fundamental component of load current is 4A. The rms value of net harmonic current is
(A) 0.08 A
(B) 0.08
(C) 0.16 A
(D) 0.16
Ans:B
37) In a power generation station the Demand factor and Load factor are 0.5 and 0.2, respectively. If the connected load is 400 MW, the average demand is
(A) 40 MW
(B) 100 MW
(C) 140 MW
(D) 280 MW
Ans:A
38) The constants B and C, respectively, of a medium transmission line by nominal T model are
(A) 1+YZ/2 , Z
(B) 1+YZ/2, Y
(C) Z, Y(1+YZ/4)
(D) Z(1+YZ/4), Y
Ans:D
39) The main limitation for power handling capability of short length transmission lines and cables is
(A) power factor
(B) stability
(C) thermal effect limit
(D) conductor size
Ans:C
40) A travelling wave of surge resistance, R0 on a transmission line is terminated by a load resistance, RL. If RL>R0 then there is
(A) no reflected wave
(B) partial reflection of reversal of current only
(C) partial reflection of reversal of voltage only
(D) reflection of reversal of both current and voltage
Ans:B
41) In a 3-phase 4-wire distribution system three unbalanced but equal magnitude impedences are connected between respective lines and neutral. The magnitude of current in the neutral conductor for RYB and RBY phase sequences are
(A) zero
(B) same
(C) different
(D) same in magnitude but differs in phase
Ans:C
42) In a 3-insulator string voltage distribution system the ratio of capacitance between pin and earth to the self capacitance of each unit is 1/4. If the potential across the top unit is 8 KV , the string voltage is
(A) 22.5 KV
(B) 24 KV
(C) 26 KV
(D) 32.5 KV
Ans:D
43) The Geometric Mean Radius of a phase conductor composed of four bundled conductors marked as 1,2,3,4 each of radius,r and spaced at a distance, d from each other is
(A) (rd12d13d14)^1/4
(B) (re^-1/4d12d13d14)
(C) (re^-1/4d12d13d14)^1/2
(D) (re^-1/4d12d13d14)^1/4
Ans:D
44) The corona loss of a 3-phase transmission line is 100KW at 60 KV/phase and 25 KW at 50 KV/phase. The discriptive critical voltage is
(A) 40 KV
(B) 43.6 KV
(C) 49.6 KV
(D) 50 KV
Ans:A
45) A 3-phase star-connected 75 MVA, 25 KV 3-phase synchronous generator has a synchronous reactance of 1.0 p.u. The per unit value to a 90 MVA base and 30 KV is
(A) 2/15 p.u
(B) 5/6 p.u
(C) 1.0 p.u
(D) 1.2 p.u
Ans:B
46) The Geometric Mean Radius of a conductor having 3-strands each of radius, r placed in the form of a triangle is
(A) (r*r*r)^1/3
(B) (e^-0.25*r*2r*2r)^1/3
(C) (e^-0.5*r*2r*2r)^1/3
(D) (e^-1/3*r*2r*2r)^1/3
Ans:B
47) Reactive power compensation in feeders leads to
(A) poor voltage profile
(B) improved voltage profile
(C) negative and zero sequence currents
(D) expensive voltage regulators
Ans:B
48) The system voltage is enhanced during heavy load condition and reduced during light load condition by using
(A) shunt capacitor
(B) shunt reactor
(C) active power filter
(D) static VAR Compensator
Ans:D
49) A balanced star connected load takes 50 A from a balanced 3-phase, 4-wire supply. The zero and positive sequence components, Ia0 and Ia+ of the line current, Ia are
(A) 0,0
(B) 0, 50 A
(C) 50 A, 0
(D) 50 A, 50 A
Ans:B
50) A 3-phase generator with a phase emf of 1.0pu and with positive, negative and zero sequence reactances of 0.25 p.u, 0.25 p.u, and 0.1 p.u, respectively, is grounded through a reactance of 1.0 p.u. For a single-line to ground fault, the fault current is
(A) 1/j0.3
(B) 1/j0.7
(C) 1/j0.9
(D) 3/j0.7
Ans:A
51) In a 3-phase system for a line-to-line fault the positive,negative and zero sequence voltages Va1,Va2,Va0, respectively, for phase voltage, Va are related as
(A) Va1+Va2+Va0=Va
(B) Va1=Va2=Va0
(C) Va1=Va2
(D) Va1+Va2+Va0=0
Ans:C
52) In induction type directonal over current relay the driving torque is due to interaction of magnetic fields derived from
(A) current in the potential coil
(B) both voltage and current in the relay windings
(C) directional element and non directional element
(D) non-directional element and the trip circuit
Ans:C
53) The operating characteristics of a reactance type distance relay
(A) a stepped waveform for increasing reactance
(B) a straight line for a constant reactance
(C) a circle for a constant reactance
(D) a set of circles for variable reactances
Ans:B
54) The prospective voltage across the circuit breaker cntacts for a given series inductance, L and shunt capacitance, C is
(A) directly proportional to (LC)
(B) inversely proportional to (LC)
(C) directly proportional to (L/C)^1/2
(D) inversely proportional to (L/C)^1/2
Ans:C
55) Transient stability studies of a power system are usually carried out over a time period of
(A) two or more seconds
(B) several time swings
(C) time interval of first swing
(D) sustained oscillations
Ans:C
56) The swing equation for a synchronous machine is based on
(A) relative motion between load angle and stator magnetic field
(B) maximum power flow possible through a particular point
(C) net torque and angular displacement
(D) relation between excitation voltage and excitation current
Ans:A
57) The cascade amplifier is a multistage configuration of
(A) CE-CC
(B) CE-CB
(C) CC-CB
(D) CB-CC
Ans:B
58) A 100 pf capacitor has a maximum charging current of 150 uA. what is the slew rate?
(A) 1.5 V/us
(B) 1.05 V/us
(C) 0.15 mV/us
(D) 10.5 mV/s
Ans:A
59) The output frequencies of bridge rectifier and half wave rectifier respectively are (fin is input frequency)
(A) 2fin and fin
(B) 2fin and 2fin
(C) fin and 2fin
(D) 2fin and fin/2
Ans:A
60) An ideal Op-Amp is an ideal
(A) voltage controlled current source
(B) voltage controlled voltage source
(C) current controlled current source
(D) current controlled voltage source
Ans:B
61) While biasing JFET if drain and source are interchanged, then
(A) device will work normally
(B) device will get damaged
(C) device will work but value of drain current will affected
(D) device will not operate at all
Ans:A
62) Two light bulbs are connected in series across a 120V battery. Bulb 1 uses 40 W of power and Bulb 2 uses 20 W of power. If bulb 1 alone is connected to the 120 V source, then it will consume
(A) 90 W
(B) 80 W
(C) 60 W
(D) 180 W
Ans:A
63) A network consists of several inductances connected in parallel. The equivalent inductances of the network is given by
(A) the sum of the individual inductances
(B) the reciprocal of the sum of the individual inductances
(C) the sum of the reciprocals of individual inductances
(D) the reciprocals of the sum of the reciprocals of individual inductances
Ans:D
64) A d.c source has an open circuit voltage of 30 V and an internal resistance of 1.5 ohm. A resistive load is connected to the source. Maximum power dissipated in the load is
(A) 300 W
(B) 150 W
(C) 45 W
(D) 20 W
Ans:C
65) At a particular instant, the R-phase voltage of a balanced 3-phase system is +30 V, and the Y-phase voltage is -90 V. The voltage of B-phase at the instant is
(A) +120 V
(B) -120 V
(C) -60 V
(D) +60 V
Ans:D
66) A coil of inductance 240 mH and resistance 75 ohm is connected in parallel with a capacitor across a 30 V, variable frequency supply. The current drawn by the circuit is found to be minimum when the supply frequency is 1 KHZ. The approximate values of Q-factor and band width are, respectively
(A) 40, 400 HZ
(B) 10, 100 HZ
(C) 20, 50 HZ
(D) 50, 20 HZ
Ans:C
67) A series R-L-C circuit is connected to a d.c source at t=0. The transient voltage response across capacitor C shows no oscillations. Then,
(A) (R/2L)^2 > (1/LC)
(B) (R/2L)^2 = (1/LC)
(C) (R/2L)^2 < (1/LC)
(D) R = 0
Ans:B
68) A Two-port Network is said to be symmetrical when the following equalities hold good
(A) Z11 = Z22 and Z12 = Z21
(B) Z11 = Z22
(C) Y12 = Y21
(D) Y11 = Y22 and Y12 = Y21
Ans:B
69) Referring to the circuits of Fig. 1 and Fig. 2, which of the following statements is correct with respect to V in the figures ?
(A) Circuit 1 is stable and Circuit 2 is unstable
(B) Both circuits are stable
(C) Both circuits are unstable
(D) Circuit 1 is unstable and Circuit 2 is stable.
Ans:A
70) Fig.3 shows a signal flow graph. The transmittance from A to B is
(A) 3
(B) zero
(C) 4/3
(D) 3/4
Ans:D
(C) furnace loads
(D) single-phase loads
Ans:B
18) Two transformers having the same p.u impedence connected in parallel share the connected load
(A) equally
(B) in proportion to the respective ratings
(C) in proportion to the voltage ratio
(D) in proportion to the zero phase displacement
Ans:B
19) A 1100KVA, 11KV/1.1KV conventional two-winding transformer is connected as a 12.1KV/11KV step-down auto-transformer. The rating of the auto-transformer is
(A) 1000 KVA
(B) 1100 KVA
(C) 11000 KVA
(D) 12100 KVA
Ans: D
20) The energy density of magnetic field in a magnetic circuit is
(A) inversely proportional to magnetic flux density
(B) directly proportional to the absolute permeability
(C) directly proportional to the magnetic flux density
(D) directly proportional to the square of magnetic flux density
Ans:D
21) A shunt generator develops stable output voltage if
(A) Magnetization characteristic is linear
(B) Magnetization characteristic is non-linear
(C) the field winding resistance is more than the critical resistance
(D) the residual magnetism is equal to zero
Ans:B
22) In a differentially compounded dc motor
(A) the speed is constant as the torque increases
(B) the speed falls non-linearly as the torque increases
(C) the speed increases non-linearly as the torque increases
(D) the flux increases as the load increases
Ans:C
23) A 3-phase induction motor under locked rotor condition and with stator supply induces
(A) small voltage at slip frequency
(B) large voltage at rotor frequency
(C) zero voltage at zero frequency
(D) large voltage at slip frequency
Ans:B
24) The equivalent rotor resistance, r2' components in the equivalent circuit of a single-phase inducton motor, based on two-revolving field theory, at any slip, s are
(A) r2'/s and r2'/1-s
(B) r2'/s and r2'/2-s
(C) r2'/2s and r2'/2(1-s)
(D) r2'/2s and r2'/2(2-s)
Ans:D
25) For a 210 MW, turbo-alternator in a thermal power plant, the possible specifications of rotor diameter, stator core length, and number of poles, respectively, are
(A) 4.4 m, 1.2 m, 12
(B) 1.2 m, 4.4 m, 2
(C) 4.4 m, 1.2 m, 24
(D) 1.2 m, 4.4 m, 8
Ans:B
26) The reluctance torque of a 3-phase salient pole synchronous generator with direct and quadrature axis reactance, xd and xq, respectively, is proportional to
(A) xd-xq
(B) xd*xq
(C) 1/xd-1/xq
(D) 1/xq-1/xd
Ans: D
27) When two alternators are operating in parallel, the cause for circulating current is
(A) increase in the excitation of one machine
(B) increase in the driving torque of one machine
(C) reduction in angular velocity of one machine
(D) identical speed/load characteristic of both machines
Ans:C
28) The maximum possible power of a 3-phase synchronous motor with synchronous reactance 0.8 p.u connected to a busbar of 1.0 pu and excitation adjusted to 1.2 pu is
(A) 0.5 p.u
(B) 0.96 p.u
(C) 1.5 p.u
(D) 1.8 p.u
Ans:C
29) A synchronous capacitor is
(A) an unloaded and under excited 3-phase synchronous motor
(B) a loaded and over excited 3-phase synchronous generator
(C) an unloaded and over excited 3-phase synchronous motor
(D) a 3-phase synchronous generator loaded with a capacitor bank
Ans:C
30) In the capacitor-start, capacitor-run single-phase induction motor
(A) two capacitors are connected across the main winding
(B) when the centrifugal switch opens, the permanent capacitor is left in the auxiliary winding circuit (C) when the centrifugal switch opens, the permanent capacitor is left in the main winding circuit
(D) two capacitors are connected across the auxiliary winding.
Ans:B
31) The main purpose of permanent magnet motors are
(A) to avoid the need for field supply
(B) to provide high flux density
(C) to provide control over flux level
(D) to faciliate KW rating
Ans:A
32) The average load voltage across a resistive load of a single-phase bride converter connected with two SCRs and two diodes, operating at any firing delay angle, and supplied at 200v, 50 HZ is
(A) 200/√2∏ × cos𝞪
(B) √2×200/∏ × cos𝞪
(C) √2×200/∏ × (1+cos𝞪)
(D) 200/√2∏×(1+sin𝞪)
Ans:C
33) In a dc-ac 3-phase MOSFET bridge inverter circuit, the switches are marked in a sequence as 1,2,3 in the top-half and 4,5,6 in the bottom half of the bridge. The triggering sequence of switches that gives balanced output voltage is
(A) 1,2,3,4,5,6
(B) 1,5,3,4,2,6
(C) 1,6,2,4,3,5
(D) 1,4,2,5,3,6
Ans:C
34) In a dc-dc converter, the switch duty ratio is defined as
(A) turn-off time/time period
(B) sawtooth voltage/control voltage
(C) control voltage/peak value of sawtooth voltage
(D) control voltage/sawtooth voltage
Ans:C
35) In a four-quadrant dc motor drive system controlled by two phase controlled converters, the current and voltage of converter 1 operating in I and IV quadrants, respectively are
(A) Ia -ve, Va +ve and Ia +ve,Va -ve
(B) Ia +ve, Va +ve and Ia +ve,Va -ve
(C) Ia -ve, Va +ve and Ia -ve,Va -ve
(D) Ia +ve, Va +ve and Ia -ve,Va -ve
Ans:B
36) In a 3-phase inverter fed induction motor drive the total harmonic distortion is 4%. If the maximum value of fundamental component of load current is 4A. The rms value of net harmonic current is
(A) 0.08 A
(B) 0.08
(C) 0.16 A
(D) 0.16
Ans:B
37) In a power generation station the Demand factor and Load factor are 0.5 and 0.2, respectively. If the connected load is 400 MW, the average demand is
(A) 40 MW
(B) 100 MW
(C) 140 MW
(D) 280 MW
Ans:A
38) The constants B and C, respectively, of a medium transmission line by nominal T model are
(A) 1+YZ/2 , Z
(B) 1+YZ/2, Y
(C) Z, Y(1+YZ/4)
(D) Z(1+YZ/4), Y
Ans:D
39) The main limitation for power handling capability of short length transmission lines and cables is
(A) power factor
(B) stability
(C) thermal effect limit
(D) conductor size
Ans:C
40) A travelling wave of surge resistance, R0 on a transmission line is terminated by a load resistance, RL. If RL>R0 then there is
(A) no reflected wave
(B) partial reflection of reversal of current only
(C) partial reflection of reversal of voltage only
(D) reflection of reversal of both current and voltage
Ans:B
41) In a 3-phase 4-wire distribution system three unbalanced but equal magnitude impedences are connected between respective lines and neutral. The magnitude of current in the neutral conductor for RYB and RBY phase sequences are
(A) zero
(B) same
(C) different
(D) same in magnitude but differs in phase
Ans:C
42) In a 3-insulator string voltage distribution system the ratio of capacitance between pin and earth to the self capacitance of each unit is 1/4. If the potential across the top unit is 8 KV , the string voltage is
(A) 22.5 KV
(B) 24 KV
(C) 26 KV
(D) 32.5 KV
Ans:D
43) The Geometric Mean Radius of a phase conductor composed of four bundled conductors marked as 1,2,3,4 each of radius,r and spaced at a distance, d from each other is
(A) (rd12d13d14)^1/4
(B) (re^-1/4d12d13d14)
(C) (re^-1/4d12d13d14)^1/2
(D) (re^-1/4d12d13d14)^1/4
Ans:D
44) The corona loss of a 3-phase transmission line is 100KW at 60 KV/phase and 25 KW at 50 KV/phase. The discriptive critical voltage is
(A) 40 KV
(B) 43.6 KV
(C) 49.6 KV
(D) 50 KV
Ans:A
45) A 3-phase star-connected 75 MVA, 25 KV 3-phase synchronous generator has a synchronous reactance of 1.0 p.u. The per unit value to a 90 MVA base and 30 KV is
(A) 2/15 p.u
(B) 5/6 p.u
(C) 1.0 p.u
(D) 1.2 p.u
Ans:B
46) The Geometric Mean Radius of a conductor having 3-strands each of radius, r placed in the form of a triangle is
(A) (r*r*r)^1/3
(B) (e^-0.25*r*2r*2r)^1/3
(C) (e^-0.5*r*2r*2r)^1/3
(D) (e^-1/3*r*2r*2r)^1/3
Ans:B
47) Reactive power compensation in feeders leads to
(A) poor voltage profile
(B) improved voltage profile
(C) negative and zero sequence currents
(D) expensive voltage regulators
Ans:B
48) The system voltage is enhanced during heavy load condition and reduced during light load condition by using
(A) shunt capacitor
(B) shunt reactor
(C) active power filter
(D) static VAR Compensator
Ans:D
49) A balanced star connected load takes 50 A from a balanced 3-phase, 4-wire supply. The zero and positive sequence components, Ia0 and Ia+ of the line current, Ia are
(A) 0,0
(B) 0, 50 A
(C) 50 A, 0
(D) 50 A, 50 A
Ans:B
50) A 3-phase generator with a phase emf of 1.0pu and with positive, negative and zero sequence reactances of 0.25 p.u, 0.25 p.u, and 0.1 p.u, respectively, is grounded through a reactance of 1.0 p.u. For a single-line to ground fault, the fault current is
(A) 1/j0.3
(B) 1/j0.7
(C) 1/j0.9
(D) 3/j0.7
Ans:A
51) In a 3-phase system for a line-to-line fault the positive,negative and zero sequence voltages Va1,Va2,Va0, respectively, for phase voltage, Va are related as
(A) Va1+Va2+Va0=Va
(B) Va1=Va2=Va0
(C) Va1=Va2
(D) Va1+Va2+Va0=0
Ans:C
52) In induction type directonal over current relay the driving torque is due to interaction of magnetic fields derived from
(A) current in the potential coil
(B) both voltage and current in the relay windings
(C) directional element and non directional element
(D) non-directional element and the trip circuit
Ans:C
53) The operating characteristics of a reactance type distance relay
(A) a stepped waveform for increasing reactance
(B) a straight line for a constant reactance
(C) a circle for a constant reactance
(D) a set of circles for variable reactances
Ans:B
54) The prospective voltage across the circuit breaker cntacts for a given series inductance, L and shunt capacitance, C is
(A) directly proportional to (LC)
(B) inversely proportional to (LC)
(C) directly proportional to (L/C)^1/2
(D) inversely proportional to (L/C)^1/2
Ans:C
55) Transient stability studies of a power system are usually carried out over a time period of
(A) two or more seconds
(B) several time swings
(C) time interval of first swing
(D) sustained oscillations
Ans:C
56) The swing equation for a synchronous machine is based on
(A) relative motion between load angle and stator magnetic field
(B) maximum power flow possible through a particular point
(C) net torque and angular displacement
(D) relation between excitation voltage and excitation current
Ans:A
57) The cascade amplifier is a multistage configuration of
(A) CE-CC
(B) CE-CB
(C) CC-CB
(D) CB-CC
Ans:B
58) A 100 pf capacitor has a maximum charging current of 150 uA. what is the slew rate?
(A) 1.5 V/us
(B) 1.05 V/us
(C) 0.15 mV/us
(D) 10.5 mV/s
Ans:A
59) The output frequencies of bridge rectifier and half wave rectifier respectively are (fin is input frequency)
(A) 2fin and fin
(B) 2fin and 2fin
(C) fin and 2fin
(D) 2fin and fin/2
Ans:A
60) An ideal Op-Amp is an ideal
(A) voltage controlled current source
(B) voltage controlled voltage source
(C) current controlled current source
(D) current controlled voltage source
Ans:B
61) While biasing JFET if drain and source are interchanged, then
(A) device will work normally
(B) device will get damaged
(C) device will work but value of drain current will affected
(D) device will not operate at all
Ans:A
62) Two light bulbs are connected in series across a 120V battery. Bulb 1 uses 40 W of power and Bulb 2 uses 20 W of power. If bulb 1 alone is connected to the 120 V source, then it will consume
(A) 90 W
(B) 80 W
(C) 60 W
(D) 180 W
Ans:A
63) A network consists of several inductances connected in parallel. The equivalent inductances of the network is given by
(A) the sum of the individual inductances
(B) the reciprocal of the sum of the individual inductances
(C) the sum of the reciprocals of individual inductances
(D) the reciprocals of the sum of the reciprocals of individual inductances
Ans:D
64) A d.c source has an open circuit voltage of 30 V and an internal resistance of 1.5 ohm. A resistive load is connected to the source. Maximum power dissipated in the load is
(A) 300 W
(B) 150 W
(C) 45 W
(D) 20 W
Ans:C
65) At a particular instant, the R-phase voltage of a balanced 3-phase system is +30 V, and the Y-phase voltage is -90 V. The voltage of B-phase at the instant is
(A) +120 V
(B) -120 V
(C) -60 V
(D) +60 V
Ans:D
66) A coil of inductance 240 mH and resistance 75 ohm is connected in parallel with a capacitor across a 30 V, variable frequency supply. The current drawn by the circuit is found to be minimum when the supply frequency is 1 KHZ. The approximate values of Q-factor and band width are, respectively
(A) 40, 400 HZ
(B) 10, 100 HZ
(C) 20, 50 HZ
(D) 50, 20 HZ
Ans:C
67) A series R-L-C circuit is connected to a d.c source at t=0. The transient voltage response across capacitor C shows no oscillations. Then,
(A) (R/2L)^2 > (1/LC)
(B) (R/2L)^2 = (1/LC)
(C) (R/2L)^2 < (1/LC)
(D) R = 0
Ans:B
68) A Two-port Network is said to be symmetrical when the following equalities hold good
(A) Z11 = Z22 and Z12 = Z21
(B) Z11 = Z22
(C) Y12 = Y21
(D) Y11 = Y22 and Y12 = Y21
Ans:B
69) Referring to the circuits of Fig. 1 and Fig. 2, which of the following statements is correct with respect to V in the figures ?
(A) Circuit 1 is stable and Circuit 2 is unstable
(B) Both circuits are stable
(C) Both circuits are unstable
(D) Circuit 1 is unstable and Circuit 2 is stable.
Ans:A
70) Fig.3 shows a signal flow graph. The transmittance from A to B is
(A) 3
(B) zero
(C) 4/3
(D) 3/4
Ans:D
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