This set of High Voltage Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Voltage Regulation”.

1. The voltage drop is caused due to ______

a) the ripple

b) the capacitors not getting charged to full voltage

c) sudden increase in the current

d) the ripple and the capacitors not getting charged to full voltage

View Answer

Explanation: Most often there occurs a change in voltage which is termed as voltage drop. This happens due to the presence of the ripple voltage. The capacitors not getting charged to the maximum voltage also contributes to the drop in voltage.

2. In each stage of the voltage multiplier circuit, the loss of charge equals a voltage drop of I/fC to the load.

a) True

b) False

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Explanation: The loss of charge from a capacitor in each stage of the circuit equals voltage drop of I/fC to the load. I is the load current, f is the frequency and C is the capacitance in the voltage multiplier circuit.

3. What is the optimum number of stages for minimum voltage drop?

a) \(n_{opt}=\sqrt{\frac{V_{max} f C}{3I}}\)

b) \(n_{opt}=\sqrt{\frac{V_{max} f C}{4I}}\)

c) \(n_{opt}=\sqrt{\frac{V_{max} f C}{I}}\)

d) \(n_{opt}=\sqrt{2\frac{V_{max} f C}{I}}\)

View Answer

Explanation: The optimum number of stages for minimum voltage drop is \(n_{opt}=\sqrt{\frac{V_{max} f C}{I}}\), where V

_{max}is the maximum voltage, f is the frequency and C is the capacitance.

4. Calculate the optimum number of stages for a Cockroft-Walton voltage multiplier circuit such that the voltage drop is minimum. f=60Hz, C=0.1 μF, V_{max}=100Kv and I=6mA.

a) 5

b) 8

c) 10

d) 12

View Answer

Explanation: The optimum number of stages for minimum voltage drop is \(n_{opt}=\sqrt{\frac{V_{max} f C}{I}}\), where V

_{max}is the maximum voltage, f is the frequency and C is the capacitance.

\(n_{opt}=\sqrt{\frac{100*60*0.1}{6}}\)

n

_{opt}=10.

5. Most of the voltage drop is at the uppermost stage capacitors.

a) True

b) False

View Answer

Explanation: Most of the voltage drop is at lowest stage capacitors. Hence, the capacitance value of these capacitors is made high in order to make the circuit advantageous.

6. The regulation and ripples are______ in six-pulse circuit.

a) reduced

b) increased

c) constant

d) fluctuating

View Answer

Explanation: The regulation and ripples are reduced in six-pulse circuit. Since it requires large number of diodes and capacitors, the circuit is costlier than the single-pulse circuit.

7. What is the frequency of the circuit (for minimum voltage drop) if the optimum number of stages is ten. C=0.1 μF, V_{max}=100Kv and I=5mA.

a) 45 Hz

b) 50 Hz

c) 55 Hz

d) 60 Hz

View Answer

Explanation: The equation for the frequency is:

f=\(\frac{n_{opt}^2 I}{CV_{max}}\)

f=\(\frac{100*5}{0.1*100}\)

f=50Hz.

8. The voltage drop under load condition is found by assuming that ______

a) all the capacitors are of equal value C

b) all the capacitors are of unequal value C

c) all the capacitors in one stage are of equal value C

d) all the capacitors in one stage are of unequal value C

View Answer

Explanation: The voltage drop under load condition is found by assuming that all the capacitors are of equal value C. Most of the voltage drop is at lowest stage capacitors. Hence their capacitance is increased.

9. What is meant by voltage regulation?

a) Change of average voltage across the load from the no load theoretical value expressed as a percentage of no load voltage

b) Change of mean voltage across the load from the no load theoretical value expressed as a percentage of no load voltage

c) Change of maximum voltage across the load from the no load theoretical value expressed as a percentage of no load voltage

d) Change of average voltage across the load from the no load theoretical value expressed as a percentage of average voltage

View Answer

Explanation: The change occurred in voltage is referred to as the voltage drop. The ratio of voltage drop to the no load voltage is known as voltage regulation. It is defined as the change of average voltage across the load from the no load theoretical value expressed as a percentage of no load voltage.

10. The regulation can be improved by ______

a) decreasing frequency

b) increasing frequency

c) maintain frequency as a constant

d) either increasing or decreasing frequency

View Answer

Explanation: Increasing the frequency can help to improve the regulation. The upper limit set by the high voltage appearing across the inductances and high capacitors should be taken into consideration while increasing the frequency.

**Sanfoundry Global Education & Learning Series – High Voltage Engineering.**

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