AC Drive Machines QB 2022/2023 PDF

‫جامعة المنصورة‬ ‫كلية الهندسة‬ ‫قسم الهندسة الكهربية‬ ‫‪Dr: Eid Abdelbaki Gouda‬‬ ‫‪2022/2023‬‬ 1. High slip means that motor speed is …… a. Low b. Medium c. High d. None of them 2. Low slip means that motor speed is …… a. Low b. Medium c....

‫جامعة المنصورة‬ ‫كلية الهندسة‬ ‫قسم الهندسة الكهربية‬ ‫‪Dr: Eid Abdelbaki Gouda‬‬ ‫‪2022/2023‬‬ 1. High slip means that motor speed is …… a. Low b. Medium c. High d. None of them 2. Low slip means that motor speed is …… a. Low b. Medium c. High d. None of them 3. If the induction motor slip is zero (s = 0), then ……. a. Ns = Nr b. Ns < Nr c. Ns > Nr d. None of them 4. ……. is used to improve starting torque of induction motor. a. Deep bar b. Double cage c. Both d. None 5. ……. means that the rotor bars consist of layers of different resistance. a. Deep bar b. Double cage c. Wound rotor d. Dc motor 6. Working operation of deep bar is like …… a. Double cage induction motor b. Squirrel cage induction motor c. Wound rotor induction motor d. None of them 7. In double cage induction motor, at starting the resistance is ……. a. High b. Low c. Medium d. None of them 8. In case of double cage induction motor, the inner cage has……... a. High inductance and low resistance b. low inductance and high resistance  c. low inductance and low resistance d. High inductance and high resistance 9. In case of double cage induction motor, the outer cage has…... a. High inductance and low resistance b. low inductance and high resistance c. low inductance and low resistance d. High inductance and high resistance 10. When unbalance operation occurs in three phase induction motor, the motor performance becomes like ……. a. DC shunt motor b. Single phase induction motor c. Synchronous motor d. Nothing happens. 11. When unbalance operation occurs in induction motor, …… flux appears. a. Positive sequence b. negative sequence c. zero sequence d. All of them 12. In positive sequence torque, voltage and current is …… a. Forward b. Backword c. Can be both d. None of them 13. In negative sequence torque, voltage and current is …… a. Forward b. Backword c. Can be both d. None of them 14. Slip for negative sequence analysis of induction motors is …. a. s b. 2–s c. -s d. 2+s 15. Positive sequence rotation is ……. and its phase arrangement is …… a. clockwise a,b,c b. clockwise a,c,b c. anticlockwise a,b,c d. anticlockwise a,c,b 16. Negative sequence rotation is ………. and its phase arrangement is …… a. clockwise a,b,c b. clockwise a,c,b c. anticlockwise a,b,c d. anticlockwise a,c,b 17. Zero sequence arrangement is …… a. clockwise a,b,c b. anticlockwise a,c,b c. in phase d. none of them 18. Reason of positive sequence, negative sequence and zero sequence fluxes appearance in induction motors is ………. a. unbalance operation b. one of phases runs out c. harmonics of the source d. all of them 19. Harmonic voltages and currents of order m=6k-1 (where k is an integer) are of…… a. Positive sequence b. Negative sequence c. Zero sequence d. None of the above 20. Harmonic voltages and currents of order m=6k+1 (where k is an integer) are of…… a. Positive sequence b. Negative sequence c. Zero sequence d. None of the above 21. Harmonic voltages and currents of order m=3k (where k is an integer) are of….. a. Positive sequence b. Negative sequence c. Zero sequence d. None of the above 22. 15th harmonic is …… a. positive sequence b. negative sequence c. zero sequence  d. none of them 23. 13th harmonic is …… a. positive sequence b. negative sequence c. zero sequence d. none of them 24. 11th harmonic is …… a. positive sequence b. negative sequence c. zero sequence d. none of them 25. Starting current of IM is about …… times of rated current of the machine. a. 5-7 b. 10-12 c. 2-3 d. 15-18 26. High starting current causes……. a. High losses b. Voltage drops c. Heating d. All of them 27. When don’t you need a starting tool for motors? a. At big load b. At light load c. At medium load d. Always needed starting tool 28. Methods of starting induction motors are …... a. Star delta b. Auto transformer c. Ac voltage controller d. All of them 29. At star delta method of starting IMs, starting phase current decreases to …. % a. 33.33 b. 57.7 c. 60 d. 50 30. At star delta method of starting IMs, starting torque decreases to …. % a. 33.33 b. 57.7 c. 60 d. 50 31. At star delta method of starting IMs, ……. connection is used at the beginning and after time …… connection. a. Star, star b. Delta, delta c. Star, delta d. Delta, star 32. Disadvantage of using autotransformer for starting of IM is …. a. High inrush current b. High starting current c. High starting torque d. High power 33. Autotransformer decreases starting current of IM by …… a. Increasing turns ratio of the secondary b. Decreasing turns ratio of the secondary c. Doesn’t change turns ratio. d. None of them 34. There is …. connections of autotransformer for starting induction motors. a. 3 b. 1 c. 2 d. 4 35. There is …. transition of autotransformer for starting induction motors. a. open circuit b. closed circuit. c. Both d. None 36. …… is an electronic circuit can change the rotor resistance smoothly to decrease starting current of induction motors. a. Star delta starting b. Soft starting c. Autotransformer starting  d. Rotor resistance starting 37. Any of the next methods has the same working of operation. a. Rotor resistance starting b. Soft starting c. Part winding starting d. All of them 38. Methods of braking motors are ….. a. Regenerative braking b. Plugging braking c. Dynamic braking d. All of them 39. When fed from a source of fixed frequency, regenerative braking of induction motors is possible only when the motor speed is.…… synchronous speed. a. greater b. lower c. equal d. none of them 40. In regenerative braking of induction motors the slip will be …… a. positive b. negative c. zero d. none of them 41. ……. is the method of removing the source and replacing it by resistance. a. Regenerative braking b. Plugging braking c. Dynamic braking d. none of them 42. ……. is the method of replacing two phases. a. Regenerative braking b. Plugging braking c. Dynamic braking d. none of them 43. ……. is method that only be used with wound rotor induction motor and not for SCIM. a. regenerative braking b. Plugging braking c. Ac Dynamic braking  d. none of them 44. Types of dynamic braking for IM are …… a. ac dynamic braking b. dc dynamic braking c. self-excited braking by using capacitors. d. all of them 45. The IM motor can be stopped by plugging by …… a. interchanging connections of any two phases of stator b. interchanging connections of any two phases of rotor c. disconnecting stator circuit d. none of them 46. Ac dynamic braking of induction motor is obtained when the motor is run on.…. a. a single phase supply b. there phase supply c. disconnecting the supply d. none of them 47. In Ac dynamic braking of IM, when rotor has a high resistance, the net torque is …… and braking operation is obtained. a. positive b. negative c. zero d. none of them 48. There is …. possible connections of dc dynamic braking of induction motors. a. 3 b. 1 c. 2 d. 4 49. ……….. is from dc dynamic braking connections of induction motors. a. three lead – star connection b. two lead – delta connection c. three lead – delta connection d. All of them 50. When the three phases of the stator of IM are disconnected from the ac 3-ph supply and only two phases of them are connected to a dc source this situation represent……... a. Two lead – Dc dynamic braking  b. Two lead – Ac dynamic braking c. Three lead – Dc dynamic braking d. Three lead – Ac dynamic braking 51. When the three phases of the stator of IM are disconnected from the ac 3-ph supply and two phases of them are connected to a dc source and the third phase is shorted with one of the two phases this situation represent ……. a. Two lead – Dc dynamic braking b. Two lead – Ac dynamic braking c. Three lead – Dc dynamic braking d. Three lead – Ac dynamic braking 52. In Dc dynamic braking of induction motors, the dc source is usually provided from a …………. connected to a transformer. a. full bridge rectifier b. battery c. solar panel d. none of them 53. At Dc dynamic braking of induction motors, the new slip equals to S = ………… a. (2 – s) b. (– s) c. (2s) d. (1 – s) 54. When motor is at no load, its speed can be considered as …………… a. Synchronous speed b. Above Synchronous speed c. Under Synchronous speed d. zero 55. AC Dynamic Braking method of induction motor can be only used with ………. a. WRIM b. SCIM. b. WRIM or SCIM a. None 56. Dc Dynamic Braking method can be used with ………. a. WRIM b. SCIM. c. Both of them d. None 57. ………… braking method can be used with squirrel-cage and wound- rotor induction motors a- Zero Sequence b- Dc Dynamic c- AC Dynamic d- Both of a, b 58. ……….…. braking method of IM put the machine under more balance as no phases are left open. a. DC Dynamic Braking b. Zero Sequence method c. AC Dynamic Braking d. none of them 59. The Zero Sequence Braking method of induction motors can be done using ………. a. DC source. b. AC source. c. either a or b d. None of them 60. At Zero Sequence Braking of induction motors using ……., torque equals zero at (1/3) of Synchronous speed. a. DC source. b. AC source. c. DC or AC d. None of them 61. During Zero Sequence braking of induction motors, speed falls faster in the case of ……. supply a. DC source. b. AC source. c. DC or AC d. None of them 62. Regarding operating states of IM, When the initial slip s1 = 1 and the final slip s2 = 0.05, the state of machine is …… a. starting. b. stop by plugging. c. Speed reversal by plugging. d. None of them 63. Regarding operating states of IM, When the initial slip s1 = 2 and the final slip s2 = 1, the state of machine is ….  a. starting. b. stop by plugging. c. Speed reversal by plugging. d. None of them 64. Regarding operating states of IM, When the initial slip s1 = 2 and the final slip s2 = 0.05, the state of machine is a. starting. b. stop by plugging. c. Speed reversal by plugging. d. None of them 65. Without adding any resistance or reactance to the motor circuit, the slip at which maximum torque occurs has a ………. a. constant value b. variable value c. adjustable value d. none of them 66. Which of the following is considered a speed control method for induction machines ……… a. Pole changing b. Supply frequency control c. Rotor resistance control d. All of them 67. Which of the following is considered a speed control method for induction machines …………. a. Stator voltage control b. Slip power recovery c. Eddy current coupling d. All of them 68. speed control of induction motor depends on ….. a. source frequency b. motor poles c. load torque d. both of a and b 69. ……. Is the method which the control of speed happens because of changing number of poles. a. Stator voltage control b. Supply frequency control c. Pole changing d. Slip power recovery. 70. The synchronous speed of a 4-pole induction motor supplied from a 50 Hz source and a slip equals 0.05 is …… a. 1500 rpm b. 1425 rpm c. 75 rpm d. None of them 71. The speed of a 4-pole induction motor supplied from a 50 Hz source and a slip equals 0.05 is ……… a. 1500 rpm b. 1425 rpm c. 75 rpm d. None of them 72. The slip speed of a 4-pole induction motor supplied from a 50 Hz source and a slip equals 0.05 is ……… a. 1500 rpm b. 1425 rpm c. 75 rpm d. None of them 73. Pole changing method could be applied on …………. a. squirrel cage IM only b. Slip Ring IM only. c. Both types d. Wound-Rotor IM 74. The disadvantage of …………. Speed control method is high cost. a. Stator voltage control b. Supply frequency control c. Pole changing d. Slip power recovery. 75. One way to overcome the problem of high cost in pole changing method is ……… a. Use two separate stator winding. b. Use single stator winding divided into few-coil groups c. Both types d. None of them 76. In practice, for simplicity winding is divided into ………. a. three-coil groups b. two-coil groups c. four-coil groups d. not divided 77. The disadvantage of …………. The speed control method is its low output torque. a. Stator voltage control b. Supply frequency control c. Pole changing d. Slip power recovery. 78. At low speeds, the efficiency of the induction machine …… a. increases b. decreases c. Not affected d. none of them 79. in Stator voltage control method, voltage source can be controlled using …. a. Ac voltage controller b. Cycloconverter c. Rectifier d. None of them 80. Stator voltage control is speed control methods applied on ……. a. squirrel cage IM only b. Slip Ring IM only. c. Both types d. None of them 81. Eddy current coupling is speed control methods applied on ….. a. squirrel cage IM only b. Slip Ring IM only. c. Both types d. None of them 82. Slip power recovery is speed control methods applied on …… a. squirrel cage IM only b. Slip Ring IM only. c. Both types d. None of them 83. Rotor resistance control is speed control methods applied on …… a. squirrel cage IM only b. Slip Ring IM only. c. Both types d. None of them 84. V/f is maintained constant in the following case of speed control of induction motor.  a. Below base speed with voltage control b. above base speed with voltage control c. Below base speed with frequency control d. above base speed with frequency control 85. VSI induction motor drive causes low frequency harmonics which causes ….. a. Motor losses increase only. b. Motor losses decrease only. c. Motor losses increase and derating of the motor. d. derating of the motor. 86. The main principle in v/f control in induction motor speed is …. a. Constant torque b. Constant flux c. Constant power d. Variable flux 87. In v/f control in induction motor speed, after rated frequency the flux of the motor ……… a. Increases b. decreases c. constant d. none of them 88. In v/f control in induction motor speed, after rated frequency the motor torque ……… a. Increases b. decreases c. constant d. none of them 89. In v/f control in induction motor speed, after rated frequency the motor power ……… a. Increases b. decreases c. constant d. none of them 90. In v/f control in induction motor speed, before rated frequency the flux of the motor ……… a. Increases b. decreases c. constant d. none of them 91. In v/f control in induction motor speed, before rated frequency the motor torque ……… a. Increases b. decreases c. constant d. none of them 92. In v/f control in induction motor speed, before rated frequency the motor power ……… a. Increases b. decreases c. constant d. none of them 93. Variable frequency control method, drop in speed from no load to full load is ….. a. Small b. Zero c. High d. None of the above 94. The method which can be used for the speed control of induction motor from stator side is ……… a. V / f control b. Controlling number of stator poles to control ns c. Stator voltage control d. All of these 95. VSI induction motor drive, ……….is used in low voltage and low power inverter. a. Thyristor b. MOSFET c. IGBT d. Diode 96. VSI induction motor drive, ……….is used in medium power inverter. a. Thyristor b. MOSFET c. IGBT d. Transistor 97. VSI induction motor drive, ……. Is used at high power levels. a. Thyristor b. MOSFET c. IGBT  d. Transistor 98. The main drawback of stepped wave inverter is ……. a. High frequency harmonics b. Low frequency harmonics c. No frequency changes. d. No voltage changes. 99. a reduction in the inverter frequency, to make synchronous speed ……than the motor speed. a. Less b. High c. Equal d. None of the above 100. an increase of the inverter frequency, to make synchronous speed ……than the motor speed. a. Less b. High c. Equal d. None of the above 101. the advantages of cycloconverters are ……. a. Creates in any power factor. b. Power transfer in either direction c. Both a and b d. None of the above 102. Cogging is a phenomenon mainly associated with……. a. 3rd harmonic b. 5th harmonic c. 7th harmonic d. 2nd harmonic 103. When an induction motor is loaded from no load to full load, its speed …… and slip ……. a. Increases, decreases b. Decreases, increases c. Both increases d. Both decreases 104. The quality of output ac voltage of a cycloconverter is improved with ….. a. Increase in output voltage at reduced frequency. b. Increase in output voltage at increased frequency. c. Decrease in output voltage at reduced frequency.  d. Decrease in output voltage at increased frequency. 105. Rotor resistance speed control method is not applicable in ……. a. Slip ring induction motor b. Squirrel cage induction motor c. Synchronous motor d. None of them 106. In v/f control in induction motor speed, after rated frequency the flux of the motor ……… and the motor torque …… a. Increases, decreases b. Both increases c. Both decreases d. Both constant 107. In v/f control in induction motor speed, before rated frequency the flux of the machine ……… and the machine torque …… a. Increases, decreases b. Both increases c. Both decreases d. Both constant 108. VFCS refers to …………. a. variable frequency current slip b. variable frequency current source c. variable frequency constant slip d. variable frequency constant source 109. VFVS refers to …………. a. variable frequency current slip b. variable frequency current source c. variable frequency variable source d. variable frequency voltage source 110. In VFCS the inverter behaves as a current source due to …. a. large inductance in DC link b. large capacitance in DC link c. large resistance in DC link d. none of them 111. The major advantage of CSI is ……. a. reliability b. stability c. controllability d. none of them 112. ………. can return power to the source.  a. VSI b. CSI c. Rectifier d. None of them 113. When inverter frequency is reduced to make synchronous speed less than motor speed, machine works as ……. a. generator b. motor c. transformer d. none of them 114. When inverter frequency is reduced to make synchronous speed less than motor speed, machine will stop by …… a. plugging b. regenerative Braking c. Dynamic Braking d. none of them 115. CSI is ………. than VSI a. more reliable b. less reliable c. same reliability d. none of them 116. ……. has inherent protection against a short circuit across motor terminals. a. VSI b. CSI c. Rectifier d. None of them 117. ……. hasn’t protection against a short circuit across motor terminals. a. VSI b. CSI c. Rectifier d. None of them 118. CSI has higher cost weight and volume due to …… a. large inductance in DC link b. large capacitance in DC link c. large resistance in DC link d. a&b 119. The CSI drive is ………. for multimotor drives where the VSI is …… for multimotor. a. not suitable & suitable b. not suitable & not suitable c. both suitable d. both not suitable 120. ………. drive is suitable for multimotor drives where ……. drive isn’t suitable for multimotor. a. VSI & CSI b. CSI & VSI c. Both CSI d. Both VSI 121. current regulated VSI operates as a CSI, it …… a. use large dc inductor and filter capacitors. b. does not use large dc inductor and filter capacitors. c. use large dc inductor. d. not use large dc inductor 122. An eddy-current clutch is identical in principle to ……… a. synchronous generator b. dc motor c. induction motor d. none of them 123. …… is available in different constructions and sizes ranging from fraction of a kW to MW. a. Rotor resistance b. Eddy current clutch c. Voltage source d. None of them 124. Advantages of eddy-current drives is …. a. rugged b. easy to maintain. c. reliable d. all of them 125. For the same torque, speed ……. with an increase in rotor resistance. a. increase b. same c. decrease d. none of them 126. cost of rotor resistance control is………. compared to variable frequency control. a. low b. high c. same d. none of them 127. Major disadvantage of rotor resistance control is …… a. low efficiency b. low reliability c. low retentivity d. none of them 128. in rotor resistance speed control, with adding resistance in rotor circuit, motor speed ……… a. increase b. same c. decrease d. none of them 129. static rotor resistance control have advantages such as ….. a. smooth and stepless control b. fast response c. less maintenance d. all of them 130. In slip power recovery speed control, when the voltage at rotor terminal is negative it will be same as …… a. increase resistance. b. decrease resistance. c. increase torque. d. none of them 131. In slip power recovery speed control, when the voltage at rotor terminal is positive it will be same as …… a. increase resistance. b. decrease resistance. c. increase torque. d. none of them 132. Static Scherbius Drive provides a …….. a. constant torque control b. constant power control c. constant load control d. constant speed control 133. Static Xramer Drive provides a ……. a. constant torque control b. constant power control c. constant load control d. constant speed control 1. The speed of a synchronous motor can be controlled by …… a. varying its frequency. b. adding resistance to rotor c. varying its voltage. d. none of them 2. synchronous motors are mainly used in …… a. constant speed application b. variable speed application c. constant torque application d. variable torque application 3. The speed of a synchronous motor can be controlled by …… a. varying its frequency. b. adding resistance to rotor. c. changing number of poles. d. Both of a & c. 4. commonly synchronous motor is …... a. wound field b. permanent magnet c. hysteresis motor d. all of them. 5. If the rotor of synchronous motor has a salient pole with fed coil it’s called ……... a. wound field synchronous motor. b. synchronous reluctance motor c. PM synchronous motor d. hysteresis motor 6. If the rotor of synchronous motor has a salient pole it’s called ……... a. wound field synchronous motor b. synchronous reluctance motor c. PM synchronous motor d. hysteresis motor 7. If the rotor of synchronous motor has a magnet it’s called ……... a. wound field synchronous motor b. synchronous reluctance motor c. PM synchronous motor d. hysteresis motor 8. wound field synchronous motor are employed in …...  a. high power and high-speed application b. high power and low speed application c. low power and high-speed application d. low power and low speed application 9. PM Synchronous motor used ……... to produce the field. a. ferrite magnet b. rare earth c. both a & b d. none of them 10. The wound field and PM Synchronous motor have ……. Load efficiency and power factor compared to induction motor. a. higher b. lower c. same d. none of them 11. All synchronous motor when design to operate with fixed frequency are provided with ……... a. damper winding b. resistance c. inductance d. capacitance 12. hysteresis motor is employed in …… a. high power application b. medium power application c. low power application b. none of them 13. The air gap in ……. is fixed. a. projecting surface mounting b. Inset magnet. c. Interior magnet d. Both of a & c 14. The air gap in ……. is variable. a. projecting surface mounting b. Inset magnet. c. Interior magnet d. Both of a & c 15. If the load torque is higher than maximum torque of the synchronous machine. What happened? a. the machine will loss synchronism  b. the machine will rotate above synchronous speed. c. the machine will rotate at synchronous speed. d. the machine will rotate below synchronous speed. 16. In synchronous motor, the motoring operation is obtained when 𝜹 is ……... a. positive b. negative c. zero d. none of them 17. In synchronous motor, the maximum torque is obtained when 𝜹 is ……... a. +90 b. -90 c. 180 d. Both of a & b 18. In synchronous motor, when the excitation is small the machine operates with ……. a. lagging power factor b. leading power factor c. unity power factor d. will not operate. 19. In permanent magnet synchronous motor, the power factor can be controlled. This statement is …… a. True b. False 20. In reluctance motor, it has ………. Power factor compared with other synchronous motors. a. highest b. lowest c. same as PM d. dependent on load 21. In synchronous motor, the damper winding provides ………. a. damp oscillation during transient b. used to start the motor as induction motor. c. used to start the motor as DC motor. d. Both of a & b 22. In synchronous motor, the starting current and torque can be reduced and increased respectively by ……... a. increasing rotor resistance  b. increasing damper resistance c. decreasing rotor resistance d. decreasing damper resistance 23. In synchronous motor, for successful pull in, the damper winding …... a. must have resistance as low as possible. b. must have resistance as high as possible. c. must have reactance as low as possible. d. must have reactance as high as possible. 24. In synchronous motor. the regenerative braking can be obtained only …… a. above synchronous speed b. below synchronous speed c. at synchronous speed d. non 25. In synchronous motor, for higher speeds while machine operate at rated terminal voltage and variable frequency, the pull-out torque is ………... as frequency increase. a. increase b. decrease c. zero d. not change. 26. What are the advantages of synchronous reluctance motor? a. Cheaper b. Higher efficiency c. Robust d. All of the above 27. Which one of the following is disadvantage of switched reluctance motor? a. Noisy in the operation b. Has no windings c. Four quadrant operation is possible. d. None of them 28. Which one of the following is an application of synchronous reluctance motor? a. Pumps or conveyers b. Nuclear reactors c. Both a and b d. None of them 29. In a synchronous motor, the starting torque is …………… a. Running torque b. Pull-out torque c. Breakaway torque d. Pull-in torque 30. The speed of a synchronous motor a. increases as the load increases. b. decreases as the load decreases. c. always remains constant. d. none of them 31. In a 3-phase, 4-pole, 50 Hz synchronous motor, the frequency, pole number and load torque all are halved. The motor speed will be ……. a. 3000 r.p.m. b. 1500 r.p.m. c. 750 r.p.m. d. none of the above 32. Synchronous motors are ………. a. not self-starting b. self-starting c. single excited d. none of them 33. The operating speed of a synchronous motor can be changed to a new fixed value by …………. a. changing the load b. changing the supply voltage c. changing frequency d. using brakes 34. For a synchronous motor, if the field excitation is such that Eb < V, then the motor is said to be …………. a. under-excited b. over-excited c. un-excited d. mild-excited 35. In Self-controlled synchronous motor drive. The source side converter is a ……… a. 6-pulse line-commutated thyristor converter b. 4-pulse line-commutated thyristor converter c. 8-pulse line-commutated thyristor converter d. 2-pulse line-commutated thyristor converter 36. In Self-controlled synchronous motor drive. In source side converter for a firing angle range 0 ≤ 𝛼≤ 90°, it works as ……. a. line-commutated fully controlled rectifier b. line-commutated fully controlled inverter c. line-commutated half-controlled rectifier. d. line-commutated half-controlled inverter. 37. In Self-controlled synchronous motor drive. In source side converter for a firing angle range 0 ≤ 𝛼≤ 90°, It deliver ……... a. positive Vds and positive Id b. positive Vds and negative Id c. negative Vds and positive Id d. negative Vds and negative Id 38. In Self-controlled synchronous motor drive. In source side converter for a firing angle range 90° ≤ 𝛼≤ 180°, it works as ……. a. line-commutated fully controlled rectifier b. line-commutated fully controlled inverter c. line-commutated half-controlled rectifier. d. line-commutated half-controlled inverter. 39. In self-controlled synchronous motor drive. For firing angle 0≤ 𝛼s≤ 90° and 90≤ 𝛼𝑙≤ 180° and with Vds> VdL the source side converter works as a/an ……… and load side converter as a/an ………. a. rectifier & inverter b. inverter & rectifier c. rectifier & rectifier d. inverter & inverter 40. In self-controlled synchronous motor drive. For firing angle 90≤ 𝛼s≤ 180° and 0≤ 𝛼𝑙≤ 90° the source side converter works as a/an ……… and load side converter as a/an ………. a. rectifier & inverter b. inverter & rectifier c. rectifier & rectifier d. inverter & inverter 41. Load commutation has several advantages over forced commutation …… a. it does not require commutation circuits. b. frequency of operation can be higher. c. it can operate at power levels beyond the capability of forced commutation. d. all of them 42. In synchronous motor When operating with self-control, the starting current is …... and starting torque is …… a. low & high b. high & low c. high & high d. low & low 43. In synchronous motor with Cycloconverter control has the advantages of …… a. smooth low speed operation b. four-quadrant operation with regenerative braking c. good dynamic response. d. all of them 44. 14- In synchronous motor with Cycloconverter control has low speed range. This statement is ……. a. true b. false 45. The brushless dc motor is dc motor. This statement is …. a. true b. false 46. In brushless dc motor. The stator has three concentrated phase windings, which are displaced by ……. and each phase winding spans ……... on each side. a. 120 & 60 b. 60 & 120 c. 60 & 60 d. 120 & 120 47. The speed of a brushless dc motor can be controlled by ……... a. Changing input DC voltage b. Changing temperature c. Changing wind direction d. Cannot be controlled. 48. Due to low inertia, brushless dc motor motors have …………. a. Faster acceleration b. Slower acceleration c. High cost d. Low cost 49. By electronic circuitry brushless dc motor can be controlled for both constant and variable torque operation.  a. True b. False 50. Is Brushless dc Motor drive in Same Dc Motor? a. True b. False