This set of FACTS Multiple Choice Questions & Answers (MCQs) focuses on “Power Semiconductor Devices – Thyristor Based Converter”.
1. In Thyristor based converters with no gate turn-off capability, how do you achieve the reversal of power?
a) Current reversal
b) Voltage reversal
c) Both current and voltage reversal
d) Reversal of terminals
View Answer
Explanation: In Thyristor based converters with no gate turn-off capability, we can achieve the reversal of power with its voltage reversal keeping the current unidirectional. Hence such Thyristor based converters are called unidirectional current converters or current sourced converters. They can only consume reactive power but cannot supply the same.
2. In Thyristor based converters with gate turn-off capability, how do you achieve the reversal of power?
a) Current reversal
b) Voltage reversal
c) Both current and voltage reversal
d) Reversal of terminals
View Answer
Explanation: In Thyristor based converters with gate turn-off capability, we can achieve the reversal of power with its current reversal keeping the voltage unidirectional. Hence such Thyristor based converters are called unidirectional voltage converters or voltage sourced converters. They can also consume supply reactive power.
3. In FACTS line commutated converters are generally preferred than self-commutated converters.
a) True
b) False
View Answer
Explanation: In FACTS line commutated converters are NOT generally preferred than self-commutated converters. Rather in FACTS self-commutated converters are preferred than line commutated converters. This is because line commutated converters consume reactive power. Also line commutated converter suffers from commutation failures occasionally while operating in the inverter mode.
4. Conventional Thyristor-based converters can be voltage sourced ones.
a) True
b) False
View Answer
Explanation: Conventional Thyristor-based converters CANNOT be voltage sourced ones. This is because conventional Thyristor-based converters are without turn-off capability. They can only be current-sourced converters.
5. Turn-off device-based converters can be current-sourced ones only.
a) True
b) False
View Answer
Explanation: Turn-off device-based converters can be current-sourced ones. They can also be voltage sourced converters. This is because unlike conventional thyristor-based converters they are with turn-off capability.
6. Turn-off device in a voltage-sourced converter valve is of __________
a) asymmetric nature
b) symmetric nature
c) either asymmetric nature or symmetric nature
d) neither asymmetric nature nor symmetric nature
View Answer
Explanation: Turn-off device in a voltage-sourced converter valve is of asymmetric nature. Turn-off devices like GTO, IGBT, IGCT are employed in it. They are of asymmetric nature.
7. Which of the following exhibits controlled turning-on and uncontrolled turning- off characteristics and also pulse gate requirement?
a) BJT
b) MOSFET
c) SCR
d) SIT
View Answer
Explanation: Out of the given options, only SCR exhibits controlled turning-on and uncontrolled turning-off characteristics and also pulse gate requirement. MOSFET does not exhibits controlled turning-on and uncontrolled turning-off characteristics. Also it does not require pulse gate signal.
8. Which of the following exhibits both the bipolar voltage-withstanding capability and unidirectional current capability?
a) BJT
b) MOSFET
c) SCR
d) SIT
View Answer
Explanation: Out of the given options, only SCR exhibits both the bipolar voltage-withstanding capability and unidirectional current capability. BJT exhibits unidirectional current capability. But it does not have bipolar voltage-withstanding capability.
9. Which of the following exhibits both the bipolar voltage-withstanding capability and unidirectional current capability?
a) BJT
b) MOSFET
c) GTO
d) SIT
View Answer
Explanation: Out of the given options, only GTO exhibits both the bipolar voltage-withstanding capability and unidirectional current capability. SIT exhibits unidirectional current capability. But it does not have bipolar voltage-withstanding capability.
10. Which of the following exhibits both unidirectional current capability and unipolar voltage-withstanding capability?
a) BJT
b) SCR
c) SITH
d) SIT
View Answer
Explanation: Out of the given options, only BJT exhibits both unidirectional current capability and unipolar voltage-withstanding capability. SCR exhibits unidirectional current capability. But it does not exhibit unipolar voltage-withstanding capability.
Sanfoundry Global Education & Learning Series – Flexible AC Transmission System (FACTS).
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