Power Electronics MCQ Multiple Choice Questions Answers - Page 2 for Practice
31. In a UJT, the p-type emitter is ........................ doped
Correct Answer is: Heavily
32. In bipolar modulation, the carrier is symmetric about zero with amplitude equal to Cm, the PWM output
Correct Answer is: Switches between -1 / 2 and +1 / 2
33. In current commutated DC - DC choppers, the voltage spike appears across the load when
Correct Answer is: Both (a and b)
34. In EMCsignal, the source delivers maximum power to the input of transmissionline when the transmission line input impedance
Correct Answer is: Is equal to the source resistance
35. In radiative coupling, the emitter radiation field
Correct Answer is: Decays as 1 / 2 R, where R is the separation distance between the emitter and the receptor
36. In single phase VSI, the harmonic which is not present is
Correct Answer is: 2nd
37. LISN is a device used to measure conducted emissions. LISN stands for
Correct Answer is: Line impedance stabilization network
38. Power electronics essentially deals with control of a.c. power at .....................
Correct Answer is: 50 Hz frequency
39. Silicon controlled rectifier can be turned on
Correct Answer is: By applying a gate pulse and turned off only when current becomes zero
40. Single phase VSI are mainly used in
Correct Answer is: All of these
41. The advantage of using free - wheeling diode in half controlled bridge converter is that
Correct Answer is: There is always a path for the dc current independent of the ac line
42. The conduction losses in IGBT is
Correct Answer is: Lower than that of MOSFET
43. The device that does not have the gate terminal is ............................
Correct Answer is: Diac
44. The device that exhibits negative resistance region is .........................
Correct Answer is: UJT
45. The effects of EMI can be reduced by
Correct Answer is: All of these
46. The input current waveform of a bridge controlled rectifier when the load is perfectly filtered is
Correct Answer is: Square wave
47. The most suited gate pulses given to the AC regulator with R - L load can be in the form of
Correct Answer is: A train of pulses
48. The normal way to turn on a diac is by ...........................
Correct Answer is: Breakover voltage
49. The output power of the cascaded amplifier-attenuator system can be determined using
Correct Answer is: Actual gain of amplifier and attenuator
50. The power MOSFET device is a
Correct Answer is: Current controlled unipolar device
51. The square wave operation of 3 phase VSI lines contains the harmonics. The amplitudes are
Correct Answer is: Inversely proportional to their harmonic order
52. The switching function of semiconductor devices can be characterized with
Correct Answer is: Duty ratio, frequency and time delay
53. The triac is .....................
Correct Answer is: Like a bidirectional SCR
54. The UJT may be used as ............................
Correct Answer is: A sawtooth generator
55. The V-I characteristics for a triac in the first and third quadrants are essentially identical to those of ........................ in its first quadrant
Correct Answer is: SCR
56. To turn on UJT, the forward bias on the emitter diode should be ...................... the peak point voltage
Correct Answer is: More than
57. TRIAC is a semiconductor power electronic device which contains
Correct Answer is: Two SCRs connected in reverse parallel
58. Under harmonic free load voltages, the 3 phase VSI
Correct Answer is: Does not contains second harmonic
59. Unipolar modulation is generally used in
Correct Answer is: DC - DC converters
60. Very large values of modulation index (greater than 3.24 lead to)
