Power electronics MCQ #10

1) In P-type semiconductor, there are

      (a) no majority carriers

      (b) electrons as majority carriers

      (c) immobile positive ions

      (d) immobile negative ions

2) In N-type semiconductor, there are

      (a) no majority carriers

      (b) holes as majority carriers

      (c) immobile positive ions

      (d) immobile negative ions

3) The snubber circuit is used in thyristor circuit for

      (a) triggering

      (b) dv/dt protection

      (c) di/dt protection

      (d) phase shifting

4) Turn ON and turn OFF time of thyristor depend on

      (a) static characteristic

      (b) junction capacitances

      (c) current gain

      (d) none of the above

ANSWER: | 1-d | 2-c | 3-b | 4-b |

5) The heat-sink on which the thyristor is mounted are made of _____, in order to get best results per unit cost.

      (a) aluminum

      (b) copper

      (c) nickel

      (d) stainless steel

6) Which of the following is used as the main switching element in a switched mode power supply (SMPS) operating in 20 kHz to 100 kHz range?

      (a) Thyristor

      (b) MOSFET

      (c) TRIAC

      (d) UJT

7) A three phase fully controlled, converter is feeding power into a DC load at a constant current of 120 A. The RMS current through each thyristor of the converter is

      (a) 50 A

      (b) 100 A

      (c) 120/1.73 A

      (d)  120 A

8) Overlap in a phase-controlled converter, under continuous conduction, does not depends on

      (a) frequency

      (b) applied voltage

      (c) load current

      (d) load inductance

ANSWER: | 5-a | 6-b | 7-c | 8-d |

9) The frequency of the ripple in the output voltage of a three-phase semi converter depends upon

      (a) firing angle and load resistance

      (b) firing angle and load inductance

      (c) the supply frequency

      (d) firing angle and supply frequency

10) HVDC transmission is preferred to EHVAC because

      (a) HVDC terminal equipment are expensive

      (b) VAR compensation is not required for HVDC system

      (c) system stability can be improved

      (d) harmonic problem is avoided

11) A single-phase full bridge inverter can operate in load commutation mode in case load consists of

      (a) RL

      (b) RLC underdamped

      (c) RLC overdamped

      (d) RLC critically damped

12) A single-phase current source inverter has capacitance C as the load. For a constant source current, the voltage across the capacitance is

      (a) square wave

      (b) triangular wave

      (c) step function

      (d) pulsed wave

ANSWER: | 9-d | 10-b | 11-b | 12-b | 

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Power electronics MCQ PDF #10