This set of Power Electronics Questions & Answers for entrance exams focuses on “SCR Commutation Techniques-2”.
Explanation: It is simply the negative of Vs as it is a series circuit & after turn off the whole voltage appears across the thyristor.
Explanation: I1 = (Vs/R)
T2 = (Vs√C/L).
Explanation: The peak SCR current is Vs/2.
Explanation: The given figure is that of a class B commutation or resonant-pulse commutation, which is a type of forced commutation technique.
Explanation: Io = Vs x [(2/R1)+(1/R2)].
6. Natural commutation of an SCR takes place when
a) voltage across the device becomes negative
b) voltage across the device becomes positive
c) gate current becomes zero
d) anode current becomes zero
Explanation: Anode current (load current) becomes zero and turns off the device, hence the name line commutation.
7. ___________ commutation is usually used in phase-controlled rectifiers
Explanation: Line commuataion is used in converters.
8. Parallel-capacitor commutation is
a) line commutation
b) load commutation
c) forced commutation
d) external-pulse commutation
Explanation: Parallel capacitor is another name for forced commutation.
9. Class E commutation is a/an
a) line commutation technique
b) load commutation technique
c) forced commutation technique
d) external-pulse commutation technique
Explanation: As an external source is used it is a external-pulse commutation technique.
Explanation: The capacitor charges from 0 to Vs with the right side plate positive.
Sanfoundry Global Education & Learning Series – Power Electronics.
To practice all areas of Power Electronics for entrance exams, here is complete set of 1000+ Multiple Choice Questions and Answers.