# FACTS Questions and Answers – Thyristor-Controlled Voltage and Phase Angle Regulators – Set 3

This set of FACTS Multiple Choice Questions & Answers (MCQs) focuses on “Thyristor-Controlled Voltage and Phase Angle Regulators – Set 3”.

1. Voltage and phase angle regulators with fast electronic control exhibit transient stability improvement in the connected system.
a) True
b) False

Explanation: Voltage and phase angle regulators with fast electronic control exhibit transient stability improvement in the connected system.

2. The amplitude of ________ in VSC does not depend upon loading condition.
a) output voltage
b) output current
c) neither output voltage nor output current
d) both output current and output voltage

Explanation: The amplitude of output voltage in VSC does not depend upon loading condition. On the other hand the amplitude of output current in VSC does depend upon load. Also the waveform of output current in VSC depends upon loading condition.

3. The current of power devices incorporating VSC is limited.
a) True
b) False

Explanation: The current of power devices incorporating VSC is NOT limited. This is because the input current is NOT constant. The peak current of power devices is dictated by the load condition.

4. In ________ the misfiring of switching device may pose a serious problem.
a) voltage sourced converter
b) current sourced converter
c) both current sourced converter and voltage sourced converter
d) no converter

Explanation: In voltage sourced converter the misfiring of switching device may pose a serious problem. While in a current sourced converter it will not create such serious problems. This is because the peak current of power devices is NOT dictated by the load condition in CSC.

5. One valve constituting a turn-off device with one parallel diode represents ________
a) voltage sourced converter
b) current sourced converter
c) voltage sourced converter or current sourced converter
d) no converter

Explanation: One valve constituting a turn-off device with one parallel diode represents voltage sourced converter. Some turn-off devices have a parallel reverse diode as its in-built part in an integrated device suitable for voltage-sourced converters. However, separate diodes are provided for high power converters.

6. CCM is an acronym for ________
a) Continuous Conduction Mode
b) Continuous Conduction Method
c) Continuous Convention Mode
d) Continuous Construction Mode

Explanation: CCM is an acronym for continuous conduction mode. This is one of the modes to examine the behavioral analysis of a voltage or current converter. Figures about current ripple, voltage ripple and switch stress are obtained in CCM of a voltage or current converter.

7. DCM is an acronym for ________
a) Discontinuous Conduction Mode
b) Discontinuous Conduction Method
c) Discontinuous Convention Mode
d) Discontinuous Construction Mode

Explanation: DCM is an acronym for continuous conduction mode. This is one of the modes to examine the behavioral analysis of a voltage or current converter. Figures about critical filter inductance, critical filter capacitance are obtained in DCM of a voltage or current converter.

8. Form factor is ________
a) RMS voltage divided by average voltage
b) average voltage divided by RMS voltage
c) average current divided by RMS voltage
d) RMS current divided by average voltage

Explanation: Form factor is RMS value of voltage divided by average value of voltage. Form factor gives an idea about the shape of output voltage. It is an important performance factor.

9. Voltage and phase angle regulators with fast electronic control exhibit power oscillation damping in the connected system.
a) True
b) False

Explanation: Voltage and phase angle regulators with fast electronic control exhibit power oscillation damping in the connected system.

10. QBT inherently always decreases the voltage magnitude with large value of its angular adjustment.
a) True
b) False

Explanation: QBT does not decrease the voltage magnitude with large value of its angular adjustment. Rather it increases the voltage magnitude of the system connected, for large value of its angular adjustment. However, it does maintain constant voltage independent of its angular displacement only for relatively small values of the later.

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