Power electronics MCQ #6

1) Which combination is used to control the AC power in a load?

      (a) two SCR’s in series

      (b) two SCR’s in parallel opposition 

      (c) three SCR’s in series

      (d) four SCR’s in series

2) The switching function of the semiconductor devices can be characterized with ________?

      (a) Frequency only

      (b) Duty ratio only 

      (c) Duty ratio and frequency

      (d) Duty ratio, frequency and time delay

3) Electrical power output of DC generator is equal to_____________?

      (a) Mechanical power i/p – iron and friction losses – cu losses

      (b) Mechanical power i/p – iron and friction losses

      (c) Electrical power developed in armature – iron and cu losses

      (d) Electrical power developed in armature – cu losses 

4) The opposite of susceptibility is_________?

      (a) Electromagnetic compatibility 

      (b) Immunity

      (c) Emission 

      (d) Interference 

5) A step – down choppers can be used in____?

      (a) Electric traction

      (b) Electric vehicles

      (c) Machine tools

      (d) All of these

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

6) The modulating signal is___________ wave in the SPWM?

      (a) Sinusoidal

      (b) Square 

      (c) Triangular

      (d) Saw – tooth

7) The transfer function of PWM is generally developed in______________?

      (a) Time domain

      (b) Frequency domain

      (c) Either (A) or (B)

      (d) None of these

8) If the firing angle becomes negative, then the rectifier works as_______________?

      (a) A rectifier

      (b) An inverter

      (c) A chopper

      (d) A regulator

9) Ripple factor is the ratio of___________?

      (a) Peak value of the DC component of load voltage to the AC voltage 

      (b) RMS value of the AC component of load voltage to the DC voltage 

      (c) Avg value of the DC component of load voltage to the AC voltage

      (d) Avg value of the AC component of load voltage to the peak value of voltage

10) Form factor of a rectifier is the ratio of ______________?

      (a) Peak value of current and voltage to its RMS value

      (b) Average value of current and voltage to its RMS value

      (c) RMS value of voltage and current to its average value 

      (d) RMS value of voltage and current to its peak value 

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

11) With increase in firing angle,

      (a) Harmonic distortion decreases and quality of input current increases

      (b) Both harmonic distortion and quality of input current decreases

      (c) Both harmonic distortion and quality of input current increases 

      (d) Harmonic distortion increases and quality of input current decreases 

12) The power MOSFET device is a___________?

      (a) Voltage controlled bipolar device

      (b) Voltage controlled unipolar device

      (c) Current controlled bipolar device

      (d) Current controlled unipolar device 

13) The conduction losses in IGBT is____________?

      (a) Equal to that of MOSFET

      (b) Lower than that of MOSFET

      (c) More than that of MOSFET 

      (d) Equal to that of BJT

14) For a buck converter to reduce the conduction losses in diode _______ switch can be added ______.

      (a) A low on – in series

      (b) A low on – in parallel

      (c) A high on – in series

      (d) A high on – in parallel

15) Advantages of HVDC transmission over AC system is / are____________?

      (a) Very good dynamic behavior

      (b) They can link two AC system operating unsynchronized

      (c) Reversal of power can be controlled by firing angle 

      (d) All of these

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

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