SIDDHARTH INSTITUTE OF ENGINEERING & TECHNOLOGY Dept . of EEE POWER SEMICONDUCTOR DRIVES Objective question bank 1.In ac - dc conversion, when the switch is closed then the sum of voltages around the loop is a. Zero [ ] b. Non zero c. Equal to the sum of voltage when switch is open d. Twice of the voltage when switch is open 2.A 3-ɸ semi controlled converter is ----- pulse converter [ ] A)6 B)3 C) 12 D) 18 3. .A 3-ɸ fully controlled converter is operated at --------------- quadrant [ ] A)single B) two C) four D) three 4. The back emf of a dc series motor is directly proportional to _________ [ ] A) V-I(Ra+Rse) B) V-IRa C) V+I(Ra+Rse) D) V+IRa 5. The thyristors in 3 phase converters are fired in sequence with phase difference of [ ] A) 600 B) 900 C) 1200 D) 1800 6. In 3 phase converters each thyristor pair gate pulse is of ________ duration. [ ] 0 0 0 0 A) 60 B) 90 C) 120 D) 180 7. As the firing angle of three phase semi converter drive connected to dc separately excited motor increases then the input power factor [ ] A)decreases B) increases C) remains same D) can’t say o 8. In three phase converters =0 at t= _______ [ ] o o o o A) 0 B) 60 C) 90 D) 180 9. In a 3- semi converter each thyristor conducts for a period of _________ [ ] o o o o A) 60 B) 90 C) 120 D) 150 10. In braking, motor works as [ ] A) Transformer B) generator C) condenser D) motor itself 11. Which of the following is/are advantages of electric braking [ ] A) less maintenance B) fast operation C) high efficiency D) all the above 12. In the which of the following braking, power is fed back to the supply [ ] A) Regenerative braking B) dynamic braking C) Plugging D) all the above 13. During regenerative braking in a dc shunt motor its [ ] A) Eg > V B) Eg V C) Eg= V D) Eg V 14. In a 3- semi converter each thyristor conducts for a period of _________ [ ] o o o o A) 60 B) 90 C) 120 D) 150 15. In braking, motor works as [ ] A) Transformer B) generator C) condenser D) motor itself 16. Which of the following is/are advantages of electric braking [ ] A) less maintenance B) fast operation C) high efficiency D) all the above 17. In the which of the following braking, power is fed back to the supply [ ] A) Regenerative braking B) dynamic braking C) Plugging D) all the above 18. During regenerative braking in a dc shunt motor its [ ] A) Eg > V B) Eg V C) Eg= V D) Eg V 19. The necessary condition to suppress dc circulating current in circulating method of dual converter is (A and B are firing angler of rectifiers [ ] 0 0 A)A+B = 0 B) A = B C)A+B =180 D)A-B =180 20.A dual converter is a_____ quadrant converter. [ ] A) 1 B) 2 C) 3 D) 4 21.To make dc machine operating in reverse motoring then__________________. [ ] A) V & I should be “-“ B) V & I should be “+” C) V “+” and I “-“ D) V “-“ and I “+” 22.In a fully controlled rectifier dc drive the motoring operation is for _________. [ ] 0 0 0 0 A) α=90 B) α<90 C) α>90 D) α≥90 23.In electrical braking stored energy of rotating part is converted in to electrical energy and dissipated in the form of_________________. [ ] A) voltage B) torque C) vaccum D) heat

24. Write the expression for output voltage of a class ‘B’ chopper [ ] A) ά Vs B) Vs/ ά C) Vs/(1- ά) D) Vs(1- ά) 25. A DC chopper output voltage can be controlled by using [ ] A) Time ratio control B) current limit control C) Both a & b D) none of the above 26.1- half-controlled rectifier operates in ___ quadrant of V a – Ia plane [ ] A) First B) fourth C) both first and fourth D) both second and third 27.1- half-controlled rectifier operates in ___ quadrant of V a – Ia plane [ ] A) First B) fourth C) both first and fourth D) both second and third 28. The expression for terminal voltage of dc motor in continuous conduction of 1Ф fully controlled rectifier is [ ] V 2Vm V 2V A) m cos B) C) m sin  D) m sin  cos     29. How many diodes are required for a single phase semi converter of separately excited D.C motor? [ ] A) 1 B) 2 C) 3 D) 4 30. The back emf of a dc series motor is directly proportional to _________ [ ] A) V-I(Ra+Rse) B) V-IRa C) V+I(Ra+Rse) D) V+IRa 31. Which of the following is/are advantages of electric braking [ ] A) less maintenance B) fast operation C) high efficiency D) all the above 32. In the which of the following braking, power is fed back to the supply [ ] A) Regenerative braking B) dynamic braking C) Plugging D) all the above 33. During regenerative braking in a dc shunt motor its [ ] A) Eg > V B) Eg V C) Eg= V D) Eg V 34. The necessary condition to suppress dc circulating current in circulating method of dual converter is (A and B are firing angler of rectifiers [ ] 0 0 A)A+B = 0 B) A = B C)A+B =180 D)A-B =180 35.A dual converter is a_____ quadrant converter. [ ] A) 1 B) 2 C) 3 D) 4 36.To make dc machine operating in reverse motoring then__________________. [ ] A) V & I should be “-“ B) V & I should be “+” C) V “+” and I “-“ D) V “-“ and I “+” 37.In a fully controlled rectifier dc drive the motoring operation is for _________. [ ] 0 0 0 0 A) α=90 B) α<90 C) α>90 D) α≥90 38.In electrical braking stored energy of rotating part is converted in to electrical energy and dissipated in the form of_________________. [ ] A) Voltage B) torque C) vaccum D) heat 39Forward braking operation achieves in --------------- quadrant [ ] A)1 B)2 C) 3 D) 4 0 40. A firing angle of 1-ɸ full converter is 180 ,the output voltage is ----[ ] A)2Vm/Π B) -2Vm/Π C) Vm/Π D)0 Paper Set By: S.RAMESH 41. Which of the following is/are advantages of electric braking [ ] A) less maintenance B) fast operation C) high efficiency D) all the above 42. In the which of the following braking, power is fed back to the supply [ ] A) Regenerative braking B) dynamic braking C) Plugging D) all the above 43. During regenerative braking in a dc shunt motor its [ ] A) Eg > V B) Eg V C) Eg= V D) Eg V 44. The necessary condition to suppress dc circulating current in circulating method of dual converter is (A and B are firing angler of rectifiers) [ ] 0 0 A)A+B = 0 B) A = B C)A+B =180 D)A-B =180 1 45.A dual converter is a_____ quadrant converter. [ ] A) 1 B) 2 C) 3 D) 4 46.1- half-controlled rectifier operates in ___ quadrant of V a – Ia plane [ ] A) First B) fourth C) both first and fourth D) both second and third 47. The expression for terminal voltage of dc motor in continuous conduction of 1Ф fully controlled rectifier is [ ] V 2Vm V 2V A) m cos B) C) m sin  D) m sin  cos    

48. How many diodes are required for a single phase semi converter of separately excited D.C motor? [ ] A) 1 B) 2 C) 3 D) 4 49. The back emf of a dc series motor is directly proportional to _________ [ ] A) V-I(Ra+Rse) B) V-IRa C) V+I(Ra+Rse) D) V+IRa 50. The thyristors in 3 phase converters are fired in sequence with phase difference of [ 0 0 0 0 A) 60 B) 90 C) 120 D) 180 51. In 3 phase converters each thyristor gate pulse is of ________ duration. [ 0 0 0 0 A) 60 B) 90 C) 120 D) 180 52. As the firing angle of three phase semi converter drive connected to dc separately excited motor increases then the input power factor [ A)decreases B) increases C) remains same D) can’t say o 53. In three phase converters =0 at t= _______ [ o o o o A) 0 B) 60 C) 90 D) 180 54. In a 3- semi converter each thyristor conducts for a period of _________ [ o o o o A) 60 B) 90 C) 120 D) 150 55. In braking, motor works as [ A) Transformer B) generator C) condenser D) motor itself 56.To make dc machine operating in reverse motoring then__________________. [ A) V & I should be “-“ B) V & I should be “+” C) V “+” and I “-“ D) V “-“ and I “+” 57.In a fully controlled rectifier dc drive the motoring operation is for _________. [ 0 0 0 0 A) α=90 B) α<90 C) α>90 D) α≥90 58.In electrical braking stored energy of rotating part is converted in to electrical energy and dissipated in the form of_________________. [ A) voltage B) torque C) vaccum D) heat 59.If the converter operating as an inverter then the firing angle is ----[ 0 0 0 A)<90 B) >90 C) 0 D) 180 60.Which of the following braking method,the armature terminals are reversed [ A)plugging B) dynamic braking C)regenerative braking D) all 61.The thyristors in 3 phase converters are fired in sequence with phase difference of [ 0 0 0 0 A) 60 B) 90 C) 120 D) 180 62. In 3 phase converters each thyristor gate pulse is of ________ duration. [ 0 0 0 0 A) 60 B) 90 C) 120 D) 180 63. As the firing angle of three phase semi converter drive connected to dc separately excited motor increases then the input power factor [ A)decreases B) increases C) remains same D) can’t say o 64. In three phase converters =0 at t= _______ [ o o o o A) 0 B) 60 C) 90 D) 180 65. In a 3- semi converter each thyristor conducts for a period of _________ [ o o o o A) 60 B) 90 C) 120 D) 150 66. In braking, motor works as [ A) Transformer B) generator C) condenser D) motor itself

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67. The expression for terminal voltage of dc motor in continuous conduction of 1Ф fully controlled rectifier is [ ] Vm 2Vm V 2V A) B) C) m sin  D) m sin  cos cos     68. How many diodes are required for a single phase semi converter of separately excited D.C motor? [ ] A) 1 B) 2 C) 3 D) 4 69. The back emf of a dc series motor is directly proportional to _________ [ ] A) V-I(Ra+Rse) B) V-IRa C) V+I(Ra+Rse) D) V+IRa 70. The thyristors in 3 phase converters are fired in sequence with phase difference of A) 600 B) 900 C) 1200 D) 1800 71. In 3 phase converters each thyristor gate pulse is of ________ duration. A) 600 B) 900 C) 1200 D) 1800

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72. As the firing angle of three phase semi converter drive connected to dc separately excited motor increases then the input power factor [ A)decreases B) increases C) remains same D) can’t say o 73. In three phase converters =0 at t= _______ [ o o o o A) 0 B) 60 C) 90 D) 180 74. The necessary condition to suppress dc circulating current in circulating method of dual converter is (A and B are firing angler of rectifiers) [ A)A+B = 0 B) A = B C)A+B =1800 D)A-B =1800

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75.A dual converter is a_____ quadrant converter. [ A) 1 B) 2 C) 3 D) 4 76.To make dc machine operating in reverse motoring then__________________. [ A) V & I should be “-“ B) V & I should be “+” C) V “+” and I “-“ D) V “-“ and I “+” 77.In a fully controlled rectifier dc drive the motoring operation is for _________. [ 0 0 0 0 A) α=90 B) α<90 C) α>90 D) α≥90 78. In electrical braking stored energy of rotating part is converted in to electrical energy and dissipated in the form of_________________. [ A) voltage B) torque C) vaccum D) heat

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79.single phase half-controlled rectifier operates in ___ quadrant of Va – Ia plane [ A) FirstB) fourth C) both first and fourth D) both second and third 80. The expression for terminal voltage of dc motor in continuous conduction of 1Ф fully controlled rectifier is [ ] 81. How many diodes are required for a single phase semi converter of separately excited D.C motor? A) 1 B) 2 C) 3 D) 4 82. How many diodes are required for a single phase semi converter of SEDC motor? [ A) 1 B) 2 C) 3 D) 4 83. The back emf of a dc series motor is directly proportional to _________ [ A) V-I(Ra+Rse) B) V-IRa C) V+I(Ra+Rse) D) V+IRa

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84. Which of the following is/are advantages of electric braking A) less maintenance B) fast operation C) high efficiency

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[ D) all the above

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