Q-___________ can be used as a dc static switch.
a) GTO
b) Transistor
c) Both GTO and transistor
d) TRIAC
…………..
Answer: c
Explanation: Both GTO and transistor can be used as a dc static switch.
Q-_______ can be used as a single phase static ac switch.
a) Diode
b) SCR
c) DIAC
d) TRAIC
…………
Answer: d
Explanation: SCR cannot be used, as it is unidirectional. Diode isn’t a switch nor is the DIAC
Q-For high power applications _________ are used as static switches whereas for low power applications __________ are used.
a) Transistors, SCRs
b) SCRs, transistors
c) Diodes, transistors
d) SCRs, diodes
………….
Answer: b
Explanation: As SCR are of higher rating they are preferred in high power applications.
Q-HVDC transmission lines are __________ as compared to HVAC lines.
a) difficult to erect
b) more expensive for long distances
c) more expensive for short distances
d) less expensive for short distances
………….
Answer: c
Explanation: HVDC lines require additional cost of the converting and inverting equipments, hence they are more expensive for short distances as compared to HVAC lines.
Q-A single-phase full bridge diode rectifier delivers power to a constant load current of 10 A. The average and rms values of the source currents will be respectively.
a) 5 A, 10 A
b) 10 A, 10 A
c) 5 A, 5 A
d) 10 A, 5A
………….
Answer: b
Explanation: As the load current is continuous, Iavg = Irms = 10 A.
Q- For a SCR, conduction angle is 120° when average on-state current is 20 A. When the conduction angle is halved the earlier value, the on-state average current will be?
a) 5 A
b) 40 A
c) 10 A
d) 20 A
……….
Answer: b
Explanation: When the conduction angle is halved, the device will conduct twice then it was conducting earlier. Hence, I = 2x 20 = 40 A.
Q-The reverse recovery time of a diode is trr = 3 μs and the rate of fall of the diode current (di/dt) = 30 A/μs. Determine the storage charge.
a) 145 μs
b) 135 μs
c) 0
d) none of the mentioned
…………
Answer: b
Explanation: Storage charge = (1/2) x (di/dt) x (trr)2 = 135 μs.
Q- The converter circuit which employs turn on and turn off when the voltage and/or current through the device is zero at the instant of switching is ____________
a) a conventional converter
b) a resonant converter
c) a zero switching circuit
d) none of the mentioned
………
Answer: b
Explanation: Resonant converters are used to turn on and turn off when the voltage and/or current through the device is zero at the instant of switching.
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