Power electronics MCQ #7

1) The on – state voltage drop of IGBT consists of drip across__________?

      (a) the drift region

      (b) the collector junction

      (c) MOSFET portion

      (d) All of these

2) In dual converters________________?

      (a) One rectifier provides positive current to the source and the other negative current to the load

      (b) One rectifier provides positive current to the load and the other negative current

      (c) Both rectifiers provide negative current to the load

      (d) Both rectifiers provide positive current to the load

3) Which statement is true for bidirectional operation of converters a _______ combination of controllable switch and _______ is used.

      (a) series, a diode is used

      (b) series, a capacitor is used

      (c) parallel, a diode is used

      (d) parallel, capacitor is used

4) In rectifiers, load current flow is_________?

      (a) Unidirectional

      (b) Bidirectional

      (c) Non-directional

      (d) Either (a) or (b)Non-directional

5) Very large values of modulation index (greater than 3.24) lead to___________?

      (a) Trapezoidal AC output voltage

      (b) Square AC output voltage

      (c) Triangular AC output voltage

      (d) Sine AC output voltage

ANSWER: | 1-d | 2-d | 3-c | 4-a | 5-b |

6) Any electrical signal present in a circuit other than the desired signal is known as______________?

      (a) Interference

      (b) Distortion

      (c) Noise

      (d) All of these

7) ____ harmonic is not present in single phase VSI.

      (a) 2nd

      (b) 3rd

      (c) 5th

      (d) 7^th

8) A capacitive load in voltage source inverters generates __________ current spikes and can be ________.

      (a) Small, reduced by using an inductive filter

      (b) Large, increased by using an inductive filter

      (c) Small, increased by using an inductive filter

      (d) Large, reduced by using an inductive filter

9) The main objective of static power converters is to obtain ____________?

      (a) DC output waveform from a DC power supply

      (b) AC output waveform from a DC power supply

      (c) DC output waveform from a DC power supply

      (d) AC output waveform from an AC power supply

10) The control method used for PWM DC-DC converter is______________?

      (a) Current mode control

      (b) Voltage mode control

      (c) Hysteric control

      (d) All of these

ANSWER: | 6-c | 7-a | 8-d | 9-b | 10-d |

11) Choppers is a_______________?

      (a) AC – DC converters

      (b) DC – DC converters

      (c) DC – AC converters

      (d) AC – AC converters

12) In BJT, switching losses occurs_______?

      (a) Only at turn – on

      (b) Only at turn – off

      (c) Both at turn on and off

      (d) None of these

13) As the breakdown voltage reached, the DIAC exhibits?

      (a) Goes into avalanche condition

      (b) Negative resistance characteristics

      (c) Voltage drop snaps back

      (d) All of these

14) the ripple frequency is _____ times the input frequency in a 3-phase bridge rectifier.

      (a) Six

      (b) Two

      (c) Three

      (d) Four

15) In a load commutated DC – DC chopper, the capacitor has a_____________?

      (a) Symmetric sinusoidal voltage across itself

      (b) Symmetric rectangular voltage across itself

      (c) Symmetric triangular voltage across itself

      (d) Symmetric trapezoidal voltage across itself

ANSWER: | 11-b | 12-c | 13-d | 14-a | 15-d |

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