MCQOPTIONS
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MCQOPTIONS
This section includes 151 Mcqs, each offering curated multiple-choice questions to sharpen your Power Electronics knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
For a 10-bit digital ramp ADC using 500kHz clock, the maximum conversion time is |
| A. | 2048 μS |
| B. | 2064 μS |
| C. | 2046 μS |
| D. | 2084 μS |
| Answer» D. 2084 μS | |
| 52. |
An 8-bit, unipolar successive approximation Register type ADC is used to convert 3.5 V to digital equivalent output. The reference voltage is +5V. The output of the ADC at the end of third clock pulse after start of conversion, is |
| A. | 1010 0000 |
| B. | 1000 0000 |
| C. | 0000 0001 |
| D. | 0000 0011 |
| Answer» B. 1000 0000 | |
| 53. |
Match the two lists and choose the correct answer from the code given below:List IList II(a) Flash – ADC(i) Higher resolution and good noise immunity(b) SAC – ADC(ii) Low noise immunity and medium speed(c) RAMP – ADC(iii) Low speed and good noise immunity(d) Dual Slope - ADC(iv) Faster speed and low noise immunity |
| A. | (a)-(i), (b)-(iv), (c)-(iii), (d)-(ii) |
| B. | (a)-(i), (b)-(ii), (c)-(iv), (d)-(iii) |
| C. | (a)-(iv), (b)-(iii), (c)-(i), (d)-(ii) |
| D. | (a)-(iv), (b)-(ii), (c)-(i), (d)-(iii) |
| Answer» E. | |
| 54. |
If the resolution of a digital-to-analogue converter is approximately 0.4% of its full scale range, then it is a/an _______.: |
| A. | 16-bit converter |
| B. | 10-bit converter |
| C. | 8-bit converter |
| D. | 12-bit converter |
| Answer» D. 12-bit converter | |
| 55. |
Minimum number of bits required to represent maximum value of given analogue signal with 0.1% accuracy is: |
| A. | 8 bits |
| B. | 9 bits |
| C. | 10 bits |
| D. | 12 bits |
| Answer» D. 12 bits | |
| 56. |
A 4-bit R-2R digital to analog converter has a reference of 5V. What is the analog output for the input code 1010? |
| A. | 3.125 V |
| B. | 0.78125 V |
| C. | -3.125 V |
| D. | 0.3125 V |
| Answer» D. 0.3125 V | |
| 57. |
A 12-bit ADC is operating with a 1 μs clock period and total conversion time is seen to be 14 μs. The ADC must be of |
| A. | Flash type |
| B. | Counting type |
| C. | Integrating type |
| D. | Successive approximation type |
| Answer» E. | |
| 58. |
A 6-bit ADC has a maximum precision supply voltage of 20 V. What are the voltage changes for each LSB present and voltage to be presented by (100110), respectively? |
| A. | 0.317 V and 12.06 V |
| B. | 3.17 V and 12.06 V |
| C. | 0.317 V and 1.206 V |
| D. | 3.17 V and 1.206 V |
| Answer» B. 3.17 V and 12.06 V | |
| 59. |
For a D/A converter, the resolution required is 50 mV and the total maximum input is 10 V. The number of bits required is |
| A. | 7 |
| B. | 8 |
| C. | 9 |
| D. | 200 |
| Answer» C. 9 | |
| 60. |
A 12-bit A/D converter has a full-scale analog input of 5 V. Its resolution is |
| A. | 1.22 mV |
| B. | 2.44 mV |
| C. | 3.66 mV |
| D. | 4.88 mV |
| Answer» B. 2.44 mV | |
| 61. |
A 5-bit D/A converter has a current output. If an output current Iout = 10 mA is produced for a digital input of 10100, the value of Iout for a digital input of 11101 will be |
| A. | 12.5mA |
| B. | 13.5 mA |
| C. | 15.5mA |
| D. | 14.5mA |
| Answer» E. | |
| 62. |
A single-phase full converter with B-2 type of connection has a continuous load current waveform. The thyristor pairs T3, T4 is triggered at ωt = |
| A. | 0 |
| B. | α |
| C. | π+α |
| D. | π-α |
| Answer» D. π-α | |
| 63. |
In a single phase semi converter with resistive load and a firing angle α, each SCR and freewheeling diode would conduct for |
| A. | α, 0° |
| B. | π-α, α |
| C. | π+α, α |
| D. | π-α, 0° |
| Answer» E. | |
| 64. |
Each SCR of a 3-phase 6-pulse converter conducts for |
| A. | 120 degrees |
| B. | 60 degrees |
| C. | 180 degrees |
| D. | 360 degrees |
| Answer» B. 60 degrees | |
| 65. |
A single-phase semi-converter is connected to a 230 V source and is feeding a load R = 10 Ω in series with a large inductance that makes the load current ripple free. Find the average output current for α = 45°. |
| A. | 14 A |
| B. | 17 A |
| C. | 10 A |
| D. | 0 A |
| Answer» C. 10 A | |
| 66. |
If V1 and V2 are the instantaneous voltages of the two converter circuits in the dual convert, then the output voltage is |
| A. | V1 + V2 |
| B. | (V1 + V2)/2 |
| C. | V1 – V2 |
| D. | 2(V1 + V2) |
| Answer» C. V1 – V2 | |
| 67. |
The below shown rectifier configuration has continues load current, find the expression of the RMS value of output voltage when the supply Vs = Vm sinωt |
| A. | Vs2/2 |
| B. | 2Vs/π |
| C. | Vs |
| D. | √Vs/2 |
| Answer» D. √Vs/2 | |
| 68. |
Which of the below mentioned converter can operate in both 3-pulse and 6-pulse modes? |
| A. | 3-phase half wave controller |
| B. | 3-phase full converter |
| C. | 3-phase semi-converter |
| D. | None of the mentioned |
| Answer» D. None of the mentioned | |
| 69. |
A single phase full controlled bridge converter (B-2) uses |
| A. | 4 SCRs and 2 diodes |
| B. | 4 SCRs |
| C. | 6 SCRs |
| D. | 4 SCRs and 2 diodes |
| Answer» C. 6 SCRs | |
| 70. |
In circulating current type of dual converters, the nature of voltage across the reactor is |
| A. | triangular |
| B. | pulsating |
| C. | constant |
| D. | alternating |
| Answer» E. | |
| 71. |
A single-phase semi-converter circuit is supplying power to a motor load. The average value of load voltage is 176.72 V and the rms value is 219.3 V. Find the VRF (voltage ripple factor). |
| A. | 0 |
| B. | 0.735 |
| C. | 0.569 |
| D. | 2.48 |
| Answer» C. 0.569 | |
| 72. |
A three-phase, three-pulse, M-3 type controlled converter has firing angle for one of the SCRs set as 15°. This SCR would start conducting at |
| A. | 0° |
| B. | 15° |
| C. | 30° |
| D. | 45° |
| Answer» E. | |
| 73. |
A M-6 controlled converter or 6-pulse half-wave controlled converter is obtained by using a transformer having |
| A. | a double delta connected secondary winding |
| B. | a double star connected secondary winding |
| C. | a double delta connected primary winding |
| D. | 6-windings on both primary and secondary sides |
| Answer» C. a double delta connected primary winding | |
| 74. |
Dual converters handle ________ during no load. |
| A. | very high temperature |
| B. | no current |
| C. | only circulating current |
| D. | load current |
| Answer» D. load current | |
| 75. |
The effect of source inductance on the performance of a 3-phase controlled converter is to |
| A. | increase the average load voltage |
| B. | reduce the average load voltage |
| C. | make the load current continuous |
| D. | remove ripples from the load current |
| Answer» C. make the load current continuous | |
| 76. |
A single-phase full controlled converted with RLE load will act like a line-commutated inverter when the firing angle α |
| A. | α > 180° |
| B. | α > 90° |
| C. | α < 90° |
| D. | α = 90° |
| Answer» C. α < 90° | |
| 77. |
For a single phase thyristor circuit with R load & firing angle α, the conduction angle can be given by |
| A. | π+α |
| B. | 2π+α |
| C. | π-α |
| D. | α |
| Answer» D. α | |
| 78. |
Find the average output dc voltage of a single-phase semi-converter with Vs=230 V and firing angle of 30°. The converter is operating under continuous conduction. |
| A. | 193 V |
| B. | 256 V |
| C. | 0 V |
| D. | 230 V |
| Answer» B. 256 V | |
| 79. |
A single-phase HW rectifier with a FD is supplied by Vs = 240 V, 50 Hz, AC with a load R = 10 Ω, L = 0.5 mH and a firing angle α = 30°. Find the average value of the load current. |
| A. | 10 A |
| B. | 0.063 A |
| C. | 6.3 A |
| D. | 0.1 A |
| Answer» B. 0.063 A | |
| 80. |
A 3-phase full converter feeds power to an R load of 10 Ω. For a firing angle delay of 30° the load takes 5 kW. An inductor of large value is also connected to the load to make the current ripple free. Find the value of per phase input voltage. |
| A. | 133 V |
| B. | 230/√3 V |
| C. | 191/√3 V |
| D. | 298/√3 V |
| Answer» D. 298/√3 V | |
| 81. |
In a 3-phase semi-converter, firing angle is less than 60°, as such each SCR and diode conduct respectively for __________ (in degrees) |
| A. | 60, 60 |
| B. | 90, 30 |
| C. | 120, 120 |
| D. | 180, 180 |
| Answer» D. 180, 180 | |
| 82. |
In a 3-phase semi-converter, for firing angle less than 60° the freewheeling diode conducts for |
| A. | 30° |
| B. | 60° |
| C. | 120° |
| D. | 0 |
| Answer» E. | |
| 83. |
A single-phase semi-converter is operated from a 230 V, 60 Hz, AC source. A DMM connected at its output terminals read 219.3 V. Find the value of FF (form factor). |
| A. | 1.24 |
| B. | 0.735 |
| C. | 1.11 |
| D. | 1 |
| Answer» B. 0.735 | |
| 84. |
In a three-phase, three-pulse, M-3 type controlled converter T1 starts to conduct at 30 + n°. At what angles do T2 and T3 start to conduct? Assume that the conduction sequence is T1-T2-T3. |
| A. | 2n° and 3n° |
| B. | 150 + n° and 270 + n° |
| C. | n° each |
| D. | 30 + n° and 60 + n° |
| Answer» C. n° each | |
| 85. |
The reactor is required in a circulating current type dual converter to |
| A. | improve the power factor |
| B. | smooth-en the waveform of circulating current |
| C. | limit the circulating current |
| D. | increase the circulating current |
| Answer» D. increase the circulating current | |
| 86. |
In case of a single-phase half-wave circuit with RL load, with firing angle α and extinction angle β, the conduction angle γ can be written as |
| A. | γ = β+α |
| B. | γ = β-α |
| C. | γ = β/α |
| D. | γ = α/β |
| Answer» C. γ = β/α | |
| 87. |
A 230 V, 50 Hz, one-pulse SCR controlled converter has extinction angle β = 210°. Find the circuit turn-off time |
| A. | 10 m-sec |
| B. | 0 |
| C. | 8.3 m-sec |
| D. | 5.4 m-sec |
| Answer» D. 5.4 m-sec | |
| 88. |
A three-phase M-3 converter is operated from a 3-phase, 230 V, 50 Hz supply with load resistance R = 10 Ω. Find the value of firing angle if an average output voltage of 50% of the maximum possible output voltage is required.Hint: α > 30°. |
| A. | 92.7° |
| B. | 67.7° |
| C. | 45° |
| D. | 75.7° |
| Answer» C. 45° | |
| 89. |
In a single phase half-wave thyristor circuit with R load & Vs=Vm sinωt, the maximum value of the load current can be given by |
| A. | 2Vm/R |
| B. | Vs/R |
| C. | Vm/2 |
| D. | Vs/2 |
| Answer» D. Vs/2 | |
| 90. |
A single phase full controlled bridge converter is connected to load having R = 0.4 Ω, E = 120, L = 0.2 mH, Vs = 230V. The RMS value of load current is 10 A for a firing angle of 53.21°. Find the input power factor. |
| A. | 0.5043 lag |
| B. | 0.5391 lag |
| C. | 0.6120 lag |
| D. | Unity |
| Answer» C. 0.6120 lag | |
| 91. |
The PIV experienced by each SCRs in M-3 converter is __________ times that in a 3-phase full converter having the same output voltage. |
| A. | 0.5 |
| B. | 1 |
| C. | 2 |
| D. | 1.5 |
| Answer» D. 1.5 | |
| 92. |
All the modern AC-DC converters are using GTOs instead of SCRs because |
| A. | Temperature is an issue in SCRs |
| B. | Switching losses are high in SCRs |
| C. | GTOs have reliable commutation |
| D. | GTOs are cheaply available today |
| Answer» D. GTOs are cheaply available today | |
| 93. |
Circulating current flows |
| A. | from load to converters |
| B. | from one converter to another converter |
| C. | in the whole circuit |
| D. | none of the mentioned |
| Answer» C. in the whole circuit | |
| 94. |
The reactor in circulating current type dual converters |
| A. | increases losses |
| B. | reduces power factor |
| C. | increase the weight of the circuit |
| D. | all of the above |
| Answer» E. | |
| 95. |
A three-phase half-wave controlled converter is fed from a 3-phase, 400 V source and is connected to a load which takes a constant current of 36 A. Find,the value of average output voltage and average current rating of SCR for a firing angle of 30°. |
| A. | 234 V, 36 A |
| B. | 234 V, 12 A |
| C. | 135 V, 36 A |
| D. | 135 V, 12 A |
| Answer» C. 135 V, 36 A | |
| 96. |
A single phase half-wave controlled rectifier has 400 sin314t as the input voltage and R as the load. For a firing angle of 60°,the average output voltage is |
| A. | 200/π |
| B. | 300/π |
| C. | 100/π |
| D. | 400/π |
| Answer» C. 100/π | |
| 97. |
A single phase full wave mid-point SCR converter, uses a 230/200 V transformer with the centre tap on the secondary side. The P.I.V. per SCR is |
| A. | 100 V |
| B. | 214V |
| C. | 141V |
| D. | 282V |
| Answer» E. | |
| 98. |
A single phase full converter, feeds power to a RLE load with R = 6 Ω and E = 60 V. The supply voltage is 230 V AC and the firing angle is 50°. Find the power delivered to the battery. |
| A. | 542 W |
| B. | 100 W |
| C. | 960 W |
| D. | 730 W |
| Answer» E. | |
| 99. |
A single phase full-converter using R load is a _________ quadrant converter and that using an RL load without FD is a __________ quadrant converter |
| A. | one, one |
| B. | two, one |
| C. | one, two |
| D. | two, two |
| Answer» D. two, two | |
| 100. |
Find the expression for the average value of the output voltage for the below given circuit. Consider the load current to be continuous, firing angle = α, transformer ration 1:1 and Vs = Vm sinωt. |
| A. | (Vm/π)cosα |
| B. | (Vm/π)(1+cosα) |
| C. | (2Vm/π)cosα |
| D. | (2Vm/π)(1+cosα) |
| Answer» D. (2Vm/π)(1+cosα) | |