250+ TOP MCQs on Solid-State Switching Circuits – Single Phase, Half-Wave, AC/DC Conversion for Inductive Loads With Freewheeling Diode and Answers

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Electric Drives MCQs on “State Switching Circuits – Single Phase, Half-Wave, AC/DC Conversion for Inductive Loads With Freewheeling Diode”.

1. Calculate the voltage across the freewheeling diode when the output voltage is 24 V.
A. -15 V
B. -24 V
C. 28 V
D. 39 V
Answer: B
Clarification: The freewheeling diode is used to provide a freewheeling path. It is connected in the anti-parallel direction of the load. The voltage across the diode is -Vo=-24 V.

2. Calculate the value of the conduction angle for SCR for R-L load with a freewheeling diode if the value of β and α are 65° and 12°.
A. 168°
B. 170°
C. 130°
D. 180°
Answer: A
Clarification: The conduction angle for SCR for R-L load with a freewheeling diode is π-α=180°-12°=168°. R-L load is a current stiff type of load. The current in the SCR only flows from α to π.

3. Calculate the value of the conduction angle for diode for R-L load with a freewheeling diode if the value of α is 45°. (Continous conduction mode)
A. 220°
B. 225°
C. 230°
D. 280°
Answer: B
Clarification: The conduction angle for diode for R-L load with a freewheeling diode is π+α=180°+45°=225°. R-L load is a current stiff type of load.

4. Calculate the value of the conduction angle for diode for R-L load with a freewheeling diode if the value of β is 226°. (Discontinuous conduction mode)
A. 40°
B. 45°
C. 50°
D. 46°
Answer: B
Clarification: The conduction angle for diode for R-L load with a freewheeling diode is β-π=226°-180°=45°. R-L load is a current stiff type of load.

5. Calculate the value of the conduction angle for R-L load if the value of β and α are 56° and 18°.
A. 48°
B. 38°
C. 57°
D. 15°
Answer: B
Clarification: The conduction angle for R-L load is β-α=56°-18°=38°. R-L load is a current stiff type of load. The current in the circuit only flows from α to β.

6. Calculate the value of the fundamental displacement factor for 1-Φ Full wave bridge rectifier if the firing α=17°.
A. .98
B. .19
C. .56
D. .95
Answer: D
Clarification: Fundamental displacement factor is the cosine of angle difference between the fundamental voltage and fundamental current. D.F=cos(∝)=cos(17°)=0.95.

7. Calculate the value of the fundamental displacement factor for 1-Φ Full wave semi-converter if the firing angle value is 95o.
A. .60
B. .68
C. .62
D. .67
Answer: D
Clarification: Fundamental displacement factor is the cosine of angle difference between the fundamental voltage and fundamental current. The fundamental displacement factor for 1-Φ Full wave semi-converter is cos(∝÷2)=cos(47.5o)=.67.

8. Which one of the following load is suitable for lagging power factor load in Single phase Half-bridge inverter?
A. C load
B. R-L-C overdamped
C. R-L-C underdamped
D. L-C load
Answer: B
Clarification: R-L-C overdamped loads are generally lagging power factor loads. They require forced commutation. Anti-Parallel diodes do not help in the commutation process.

9. Which one of the following load is suitable for leading power factor load in Single phase Half-bridge inverter?
A. C load
B. R-L-C overdamped
C. R-L-C underdamped
D. L-C load
Answer: C
Clarification: R-L-C underdamped are leading power factor loads. They do not require any forced commutation technique. Anti-Parallel diodes help in the commutation process.

10. A step-down chopper has input voltage .1 V and output voltage .01 V. Calculate the value of the duty cycle.
A. 0.1
B. 0.2
C. 0.3
D. 0.5
Answer: A
Clarification: The output voltage of the step-down chopper is Vo = Vin×(D.. The value of the duty cycle is less than one which makes the Vo < Vin. The step-down chopper is used to step down the voltage. The value of the duty cycle is .01÷.1=.1.

11. Calculate the De-rating factor if the string efficiency is 98%.
A. .04
B. .02
C. .05
D. .03
Answer: B
Clarification: De-rating factor is used to measure the reliability of a string. The value of the De-rating factor is 1-(string efficiency)=1-.98=.02.

12. Calculate the string efficiency if the de-rating factor is .50.
A. 28 %
B. 42 %
C. 80 %
D. 50 %
Answer: D
Clarification: The string efficiency is calculated for series and parallel connection of SCRs. The value of string efficiency is 1-(De-rating factor)=1-.50=50 %.

13. 70 V rated 6 SCRs are connected in series. The operation voltage of the string is 130. Calculate the De-rating factor.
A. .70
B. .73
C. .78
D. .74
Answer: A
Clarification: The string efficiency can be calculated using the formula operation voltage÷(Number of SCRs×Rated voltage)=130÷(70×6)=.30. The De-rating factor value is 1-.30=.70.

14. d(v)÷d(t) is more reliable for SCR triggering.
A. True
B. False
Answer: B
Clarification: Gate triggering is more reliable than any other triggering method. The risk of false triggering of SCR increases in the case of the d(v)÷d(t) triggering.

15. Calculate the output voltage of the Buck converter if the supply voltage is 13 V and duty cycle value is .16.
A. 2.08 V
B. 2.24 V
C. 2.58 V
D. 2.54 V
Answer: A
Clarification: The output voltage of the buck converter is Vo = Vin×(D.=13×.16=2.08 V. The value of the duty cycle is less than one which makes the Vo < Vin. The buck converter is used to step down the voltage.

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