# High Voltage Engineering Questions and Answers – Ripple and Ripple Factor

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

1. What is the equation for the magnitude of ripple voltage δV?
a) $$\delta V=\frac{1}{2}(V_{max} + V_{min})$$
b) $$\delta V=\frac{1}{2}(V_{max} – V_{min})$$
c) $$\delta V=\frac{1}{4}(V_{max} + V_{min})$$
d) $$\delta V=\frac{1}{4}(V_{max} – V_{min})$$

Explanation: Test voltages generated using rectifiers are never constant in magnitude. The voltages deviate from their mean value periodically. This deviation is known as ripple. The magnitude of ripple voltage is defined as half the difference between the maximum and minimum values of voltage.

2. Ripple factor is defined as the ratio of mean value to the ripple magnitude.
a) True
b) False

Explanation: Ripple factor is defined as the ratio of ripple magnitude to the mean value. The test voltages should not have ripple factor more than 5%.

3. Peak to peak ripple is defined as ___________
a) the difference between average dc voltage and mean value
b) the difference between maximum and minimum dc voltage
c) the difference between maximum ac and average dc voltages
d) the difference between ac and average dc voltages

Explanation: Peak to peak ripple is defined as the difference between maximum and minimum dc voltage. It is also defined as the peak AC voltage minus the forward voltage of the rectifier diodes.

4. The ripple in a rectifier output depends upon ___________
b) circuit parameter like f and C
c) circuit parameter like L and C
d) load current and the circuit parameters like f and C

Explanation: The ripple voltage is given by the equation $$\delta V=\frac{I}{2fC}$$, where I is the load current and f and C are the circuit parameters. The higher the frequency of supply and larger the value of filtering capacitor the smaller will be the ripple in the dc output.

5. The ripple voltage is to be kept as low as possible.
a) True
b) False

Explanation: The ripple voltage is to be kept as low as possible. The selection of filter capacitor and the transformer reactance for a given load should be done properly so as to minimize the magnitude of the ripple voltage.

6. For half wave-rectifiers, the ripple frequency is equal to twice the supply frequency.
a) True
b) False

Explanation: For half wave-rectifiers, the ripple frequency is equal to the supply frequency. For full wave-rectifiers, the ripple frequency is equal to twice the supply frequency. The ripple voltage is to be kept as low as possible.

7. Ripple or voltage fluctuation is kept within a reasonable limit by means of ___________
a) inductor
b) resistor
c) filter
d) inductor and resistor

Explanation: The voltage fluctuation is kept within a reasonable limit by means of a filter. The value of C and f should be chosen properly.

8. The total peak to peak ripple for 4 stages is ___________
a) $$\delta V_{total}=\frac{I}{fC}$$
b) $$\delta V_{total}=\frac{10I}{fC}$$
c) $$\delta V_{total}=\frac{5I}{fC}$$
d) $$\delta V_{total}=\frac{13}{2fC}$$

Explanation: The total peak to peak ripple for n stages is given by the equation $$\delta V_{total}=\frac{I}{2fC}$$ n(n+1). Therefore, when n=4,
$$\delta V_{total}=\frac{I}{2fC}$$ 4(4+1)
$$\delta V_{total}=\frac{10I}{fC}$$

9. The average ripple for 4 stages is ___________
a) $$\delta V_{average}=\frac{10I}{fC}$$
b) $$\delta V_{average}=\frac{5I}{2fC}$$
c) $$\delta V_{average}=\frac{11I}{2fC}$$
d) $$\delta V_{average}=\frac{5I}{fC}$$

Explanation: The average ripple for n stages is given by the equation $$\delta V_{total}=\frac{I}{4fC}$$ n(n+1). Therefore, when n=4,
$$\delta V_{total}=\frac{I}{4fC}$$ 4(4+1)
$$\delta V_{total}=\frac{5I}{fC}$$

10. The total ripple for 2 stages is ___________
a) $$\delta V=\frac{I}{fC}$$
b) $$\delta V=\frac{4I}{fC}$$
c) $$\delta V=\frac{6I}{fC}$$
d) $$\delta V=\frac{8I}{fC}$$

Explanation: The total ripple for n stages is given by the equation $$\delta V=\frac{nI}{2fC}$$. Therefore, when n=2, the total ripple voltage is $$\delta V=\frac{I}{fC}$$.

11. The major contribution to the ripple is from ___________
a) uppermost capacitors
b) middle capacitors
c) ground end capacitors
d) second last capacitors

Explanation: The major contribution to the ripple is from ground end capacitors. Ripples can be reduced if the capacitance of these capacitors is increased proportionately.

12. The ripple voltage depends on the __________
a) supply frequency
b) time constant
c) reactance of the supply transformer
d) the supply frequency, the time constant and the reactance of the supply transformer

Explanation: The ripple voltage depends on the supply frequency, the time constant and the reactance of the supply transformer. Since the discharge period in the case of half–wave rectifier is larger, the ripple voltage is larger for a half-wave rectifier than a full-wave rectifier.

13. Identify 1, 2 and 3 in the given waveform of a full-wave rectifier.

a) 1-Vmax, 2-Vmean, 3-δV
b) 1-Vmin, 2-Vmean, 3-δV
c) 1-Vmean, 2-δV, 3-Vmax
d) 1-Vmean, 3-Vmax, 2-δV

Explanation: The given figure shows the output of the full-wave rectifier with a capacitor filter. 1-Vmax, 2-Vmean, 3-δV is the correct answer. Vmax represents the maximum voltage, Vmean represents the mean voltage and δV represents the ripple voltage.

Sanfoundry Global Education & Learning Series – High Voltage Engineering.

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