Following are some of the multiple choice questions on the Power Electronics with answers that will help the students in developing their knowledge.
Power Electronics MCQ
1. A chopper may be thought as a
2. Which device can be used in a chopper circuit?
3. In AC voltage controllers the
4. In the principle of phase control
5. The shape of the output voltage waveform in a single PWM is
6. A voltage source inverter is normally employed when
7. Dual converters provide
8. What are rheostats used for?
9. What is the purpose of a resistor?
10. Cycloconverter converts
11. In voltage source inverters
12. A PWM switching scheme is used with a three phase inverter to
13. The process of commutating a SCR by applying a reverse voltage to an SCR through a previously charged capacitor is called as
14. How does resistance affect current?
15. AC voltage regulator converts
16. A dual converters has
17. What are power resistors used for?
18. Which resistor will prevent the most current flow?
19. What are the color codes for a 470k ohm resistor?
20. The gate-source voltage at which the ________________ layer in a MOSFET is formed is called the ________________ voltage.
21. The minimum frequency of the output voltage harmonic in a single phase fully controlled bridge converter is _________ the input supply frequency.
22. The Gate-Source capacitance of a MOSFET is the ________________ among all three capacitances.
23. The Gate-Drain transfer capacitance of a MOSFET has large value in the ________________ region and small value in the ________________ region.
24. For the same load resistance as the vgE of an IGBT is increased it enters __________________ region.
25. An IGBT has small __________________ temperature coefficient of on state voltage drop.
26. From the input side the IGBT behaves essentially as a __________________.
27. A single phase half wave controlled converter always operates in the ________ conduction mode.
28. A UJT has ___________.
29. The input displacement factor of a single phase fully controlled bridge converter in the continuous conduction mode is equal to the cosine of the ________ angle.
30. In the discontinuous conduction mode the load current remains __________ for a part of the input cycle.
31. In the continuous conduction mode if the firing angle of the converter is increased beyond _________ degrees the converter operates in the _______ mode.
32. A half controlled converter has better output voltage ___________________ compared to a fully controlled converter.
33. For the same firing angle and input voltage the half controlled converter gives ___________________ output voltage form factor compared to a fully controlled converter.
34. At the boundary between continuous and discontinuous conduction the value of the output current at ωt = α is ___________________.
35. Single phase half controlled converters are most suitable for loads requiring ___________________ voltage and current.
36. In a three phase fully controlled converter each device conducts for an interval of __________ degrees.
37. The input ac current of a three phase fully controlled converter contains only _________ harmonics but no _________ harmonic.
38. In ___________ current dual converter only one converter conducts at any time.
39. The input current of a three phase half controlled converter does not have ________________ cycle symmetry.
40. Length of the overlap period depends on the valve of the source inductance and load ______________
41. The control method used for PWM dc - dc converter is
42. In case of TRC (Time Ratio Control), _________ is varied
43. In pulse width modulation scheme, _________ is kept constant
44. In case of a constant frequency system, Ton = (1/4)T. If the chopping frequency 2 kHz, find the value of Toff.
45. In the current limit control method, the chopper is switched off when
46. Find the output voltage for a step-up chopper when it is operated at a duty cycle of 50 % and Vs = 240 V.
47. In dc choppers, the waveforms for input and output voltages are respectively
48. If the chopper frequency is 200 Hz and on time is 2 ms, then the duty ratio would be
49. In a step down chopper, the ratio Vo/Vs is given by
50. 1. In case of three-phase dual converter, one of the converter circuits is fired at an angle of 60°. For both the converter circuits to have equal average output voltage, what is the value of the firing angle for the other converter circuit?
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