250+ TOP MCQs on Solid-State Switching Circuits – Three Phase, Half-Wave, AC/DC Conversion for Resistive Loads and Answers

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Electric Drives Multiple Choice Questions on “Solid-State Switching Circuits – Three Phase, Half-Wave, AC/DC Conversion for Resistive Loads”.

1. Calculate the Vo(avg) for the 3-Φ phase Half-wave uncontrolled rectifier if the supply value is 440 V.
A. 297.25 V
B. 298.15 V
C. 298.11 V
D. 300.15 V
Answer: A
Clarification: The Vo(avg) for the 3-Φ phase Half-wave uncontrolled rectifier is 3Vml÷2π. The value of output voltage is 3Vml÷2π=3×√2×440÷6.28=297.25 V.

2. Calculate the pulse number if the supply frequency is 2π and the output frequency is 2π÷3.
A. 4
B. 5
C. 6
D. 3
Answer: D
Clarification: The pulse number can be calculated using the ratio of input frequency to the output frequency. The value of pulse number (P) is 2π÷(2π÷3)=3. It is a three-pulse converter or 3-Φ phase Half-wave uncontrolled rectifier.

3. Calculate the average value of current for the 3-Φ phase Half-wave uncontrolled rectifier if the supply value is 400 V and resistive load value is 5 Ω.
A. 54.04 A
B. 57.26 A
C. 51.64 A
D. 58.15 A
Answer: A
Clarification: The Io(avg) for the 3-Φ phase Half-wave uncontrolled rectifier is 3Vml÷2πR. The value of output voltage is 3Vml÷2πR=3×√2×440÷6.28×5=54.04 A.

4. In 3-Φ Fully controlled rectifier calculate the average value of the voltage if the supply is 400 V and firing angle is 45°.
A. 381.15 V
B. 382.16 V
C. 383.19 V
D. 384.25 V
Answer: B
Clarification: In 3-Φ Fully controlled rectifier, the average value of the voltage is 3Vml(cos(∝))÷π=3×400×√2(cos(45°))÷3.14=382.16 V.

5. Calculate the Vo(r.m.s) (Highly inductive loaD. for the 3-Φ phase Half-wave uncontrolled rectifier if the supply value is 441 V.
A. 297.25 V
B. 298.15 V
C. 298.11 V
D. 300.15 V
Answer: A
Clarification: The Vo(r.m.s) for the 3-Φ phase Half-wave uncontrolled rectifier is 3Vml÷2π. The value of output voltage is 3Vml÷2π=3×√2×441÷6.28=297.25 V.

6. Calculate the Vo(avg) for the 3-Φ phase Half-wave controlled rectifier if the supply value is 364 V and the value of firing angle is 2°.
A. 247.62 V
B. 245.76 V
C. 214.26 V
D. 233.26 V
Answer: B
Clarification: The Vo(avg) for the 3-Φ phase Half-wave controlled rectifier is 3Vmlcos(α)÷2π. The value of output voltage is 3Vmlcos(α)÷2π=3×√2×364×(.99)÷6.28=245.76 V.

7. Calculate the value of the Input power factor for 3-Φ Fully controlled rectifier if the firing angle value is 16°.
A. .96
B. .91
C. .93
D. .94
Answer: B
Clarification: The value of the input power factor for 3-Φ Fully controlled rectifier is .95cos(16°)=.91. The input power factor is a product of distortion factor and displacement factor.

8. In 3-Φ Semi-controlled rectifier calculate the average value of the voltage if the supply is 299 V and firing angle is 56.15°.
A. 311.26 V
B. 304.26 V
C. 314.51 V
D. 312.45 V
Answer: C
Clarification: In 3-Φ Semi-controlled rectifier, the average value of the voltage is 3Vml(1+cos(∝))÷2π=3×299×√2(1+cos(56.15°))÷6.28=314.51 V.

9. Calculate the circuit turn-off time for 3-Φ Fully controlled rectifier if the firing angle is 13° and supply frequency is 49.5 Hz.
A. 730.2 msec
B. 740.8 msec
C. 754.5 msec
D. 755.1 msec
Answer: A
Clarification: The circuit turn-off time for 3-Φ Fully controlled rectifier is (240°-α)÷ω. The value of circuit turn-off time for ∝ < 60° is (240°-13°)÷6.28×49.5=730.2 msec.

10. Calculate the circuit turn-off time for 3-Φ Fully controlled rectifier if the firing angle is 170° and supply frequency is 50.5 Hz.
A. 32.4 msec
B. 35.2 msec
C. 39.3 msec
D. 31.5 msec
Answer: D
Clarification: The circuit turn-off time for 3-Φ Fully controlled rectifier is (180°-α)÷Ω. The value of circuit turn-off time for ∝ ≥ 60° is (180°-170°)÷6.28×50.5=31.5 msec.

11. Calculate the form factor if V(r.m.s)=45 V, V(avg)=15 V.
A. 2
B. 5
C. 3
D. 8
Answer: C
Clarification: The form factor is defined as the ratio of the Vr.m.s÷Vavg=45÷15=3. The r.m.s value is three times of average value Vavg.

12. Calculate the Vo(avg) for the 3-Φ phase Half-wave controlled rectifier if the supply value is 480 V and the value of firing angle is 92°.
A. 264.02 V
B. 487.26 V
C. 858.26 V
D. 248.25 V
Answer: A
Clarification: The Vo(r.m.s) for the 3-Φ phase Half-wave controlled rectifier is 3Vm(1+cos(α))÷2π. The value of output voltage is 3Vm(1+cos(α+30))÷2π=3×480×√3×√2(1+cos(92))÷2π=264.02 V.

13. Full form of SCR is ____________
A. Silicon controlled rectifier
B. State-controlled rectifier
C. State cover rectifier
D. State-controlled reset
Answer: A
Clarification: SCR stands for silicon controlled rectifier. It is a semi-controlled, bipolar, uni-directional switch. It is a high power rating than other power electronic devices.

14. Full form of TRIAC is __________
A. Triode for Alternating current
B. Tri for Alternating current
C. Triode for Alternating counter
D. Tri for Alternating counters
Answer: A
Clarification: TRIAC stands for Triode for Alternating current. It is a bipolar, bidirectional switch. It is used in fan regulators to control the speed of fans.

15. TRIAC is a unipolar switch.
A. True
B. False
Answer: B
Clarification: TRIAC stands for Triode for Alternating current. It is a bipolar, bidirectional switch. It is used in fan regulators to control the speed of fans.