This set of FACTS Multiple Choice Questions & Answers (MCQs) focuses on “Power Semiconductor Devices – Voltage Sourced Converter”.
1. Voltage-sourced converters are characterized by ________
a) unidirectional voltage
b) bidirectional current
c) bidirectional voltage
d) unidirectional current
View Answer
Explanation: Voltage-sourced converters are characterized by unidirectional voltage. They find preferred applications in FACTS. They are, principally, different from current-sourced converters.
2. The reversal of power in voltage sourced converters is achieved by ________
a) reversal of current
b) reversal of voltage
c) reversal of external supply terminals
d) reversal of phase sequence
View Answer
Explanation: The reversal of power in voltage sourced converters is achieved by reversal of current, keeping voltage unidirectional. They find preferred applications in FACTS. Voltage sourced converters are basically unidirectional voltage converters.
3. A voltage source is a passive element.
a) True
b) False
View Answer
Explanation: Any voltage source is NOT a passive element. By definition an element of any circuit which provides or delivers power of its own, is termed as an active element. A voltage source does deliver power of its own and hence is an active element.
4. A voltage source is the _______ of current source.
a) dual
b) relic
c) model
d) folder
View Answer
Explanation: A voltage source is the dual of current source. Voltage sources can be of independent and dependent types. Dependent varieties of voltage sources can be either voltage or current dependent.
5. An ideal current source delivers or absorbs current ________ of voltage across it.
a) independent
b) dependent
c) reluctant
d) hesitant
View Answer
Explanation: An ideal current source delivers or absorbs current independent of voltage across it. An independent current source delivers a constant current. A dependent current source delivers a current which is proportional to some other voltage or current in the circuit.
6. An ideal voltage source can be connected to an ideal short circuit.
a) True
b) False
View Answer
Explanation: Ideal voltage source is characterized by finite non-zero voltage rather constant voltage in the circuit while ideal short circuit is typified with zero voltage across it. This contradiction between the definitions of these two terms ‘ideal current source’ and ‘ideal short circuit’ lead to this conclusion ‘An ideal voltage source can never be connected to an ideal short circuit’.
7. The charging of a capacitor when done by a voltage source exhibits ________ relationship with time.
a) linear
b) constant
c) exponential
d) unknown
View Answer
Explanation: Basically the charging of capacitor by a voltage source exhibits exponential relationship with time. On the other hand the charging of capacitor by a constant current source maintains non-exponential relationship with time. Thus the phenomenon of charging a capacitor by constant current source and that by a voltage source are different.
8. Choose the right option among the alternatives–The current/voltage sourced converter may be represented by a gate turn-off device with a diode in series/anti-parallel to it.
a) Current, anti-parallel
b) Voltage, series
c) Voltage, anti-parallel
d) Current or voltage, series
View Answer
Explanation: The voltage sourced converter may be represented by a gate turn-off device with a diode in anti-parallel to it. It is based on the dc to ac converter. It can exchange active and/or reactive power with the ac system connected.
9. Choose the right option among the alternatives–The current/voltage sourced converter may be represented by a power device with a dc capacitor/inductor as its voltage/current source.
a) Current, capacitor, current
b) Voltage, capacitor, voltage
c) Current, inductor, voltage
d) Voltage, inductor, current
View Answer
Explanation: The voltage sourced converter may be represented by a power device with a dc capacitor as its voltage source. Here the unidirectional dc voltage of the dc capacitor is offered to the ac side as ac voltage through sequential switching of devices. The power reversal involves reversal of current, not the voltage.
10. VSC is a natural ________ converter.
a) boost-type
b) buck-type
c) universal
d) reversal
View Answer
Explanation: VSC is a natural boost-type converter. As a characteristic feature, its output voltage is always greater than the maximum value of instantaneous phase-to-phase voltage of the system connected. So it cannot be a buck-type converter.
Sanfoundry Global Education & Learning Series – Flexible AC Transmission System (FACTS).
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