Tiêu đề MCQ NDUCTION, SYNCHRONOUS AND SPECIAL ELECTRIC MACHINES.pdf ✅

Way to Polytechnic ● Way to Polytechnic INDUCTION, SYNCHRONOUS AND SPECIAL ELECTRIC MACHINES Unit-01 Three Phase Induction Motor 1. What is the principle behind the production of a rotating magnetic field in a three-phase induction motor? a) Commutation b) Capacitance c) Synchronous speed d) Phased windings - **Answer: d) Phased windings** 2. What is the synchronous speed of an induction motor? a) Equal to the rotor speed b) Varies with the load c) Depends on the number of poles and frequency d) Fixed at 3600 rpm - **Answer: c) Depends on the number of poles and frequency** 3. Which type of induction motor does not have external electrical connections to the rotor? a) Slip ring induction motor b) Squirrel cage induction motor c) Phase wound induction motor d) Wound rotor induction motor - **Answer: b) Squirrel cage induction motor** 4. What is the slip in an induction motor? a) The difference between synchronous speed and rotor speed b) The difference between rotor speed and stator speed c) The difference between rotor speed and supply frequency d) The difference between rotor speed and slip ring speed - **Answer: a) The difference between synchronous speed and rotor speed** 5. Which of the following is NOT a characteristic torque of a three-phase induction motor? a) Starting torque b) Full load torque c) Maximum torque d) Zero torque - **Answer: d) Zero torque** 6. Induction motor can be considered as a generalized transformer because of: a) Shared magnetic field b) Similar construction https://sbte.way2poly.in/
Way to Polytechnic ● Way to Polytechnic c) Both have slip rings d) Phasor diagram representation - **Answer: a) Shared magnetic field** 7. Which starter type is commonly used to reduce the starting current in a three-phase induction motor? a) Star-delta starter b) Rotor resistance starter c) Auto transformer starter d) Direct online starter - **Answer: a) Star-delta starter** 8. What is the purpose of using rotor resistance starters? a) To increase the speed of the motor b) To control the torque c) To reduce the starting current d) To decrease the slip - **Answer: c) To reduce the starting current** 9. Which method is NOT used for speed control in three-phase induction motors? a) Stator voltage control b) Pole changing c) Rotor resistance control d) DC injection - **Answer: d) DC injection** 10. Which of the following is NOT a method of motor selection for different applications? a) Stator resistance control b) Pole changing c) VVVF control d) Rotor resistance control - **Answer: a) Stator resistance control** 11. What is the main purpose of maintaining three-phase induction motors? a) To increase slip b) To reduce torque c) To prevent breakdowns and ensure longevity d) To increase the synchronous speed - **Answer: c) To prevent breakdowns and ensure longevity** 12. In a three-phase induction motor, what is the primary reason for using an auto transformer starter? a) To increase efficiency b) To decrease voltage https://sbte.way2poly.in/
Way to Polytechnic ● Way to Polytechnic c) To achieve smooth starting d) To increase power factor - **Answer: c) To achieve smooth starting** 13. What is the main function of slip rings in a slip ring induction motor? a) To regulate the voltage b) To provide mechanical support c) To control the rotor resistance d) To transfer electrical power to the rotor - **Answer: d) To transfer electrical power to the rotor** 14. How does stator resistance starter reduce the starting current? a) By increasing the stator resistance b) By decreasing the stator resistance c) By increasing the stator voltage d) By decreasing the stator voltage - **Answer: b) By decreasing the stator resistance** 15. What is the main advantage of a soft starter in induction motors? a) Increased starting torque b) Reduced mechanical wear c) Decreased power factor d) Increased slip - **Answer: b) Reduced mechanical wear** 16. What is the function of a VVVF control in speed control of induction motors? a) To control the voltage and frequency simultaneously b) To control the voltage and current simultaneously c) To control the slip ratio d) To control the stator resistance - **Answer: a) To control the voltage and frequency simultaneously** 17. Which type of induction motor has the simplest and most rugged construction? a) Slip ring induction motor b) Squirrel cage induction motor c) Wound rotor induction motor d) Single-phase induction motor - **Answer: b) Squirrel cage induction motor** 18. What is the effect of increasing the rotor resistance in an induction motor? a) Increases starting torque b) Decreases slip c) Increases slip d) Decreases starting current https://sbte.way2poly.in/
Way to Polytechnic ● Way to Polytechnic - **Answer: a) Increases starting torque** 19. Which of the following methods does NOT provide smooth acceleration in induction motors? a) Auto transformer starter b) Star-delta starter c) Rotor resistance starter d) Pole changing - **Answer: d) Pole changing** 20. What does the slip represent in an induction motor? a) The difference between synchronous speed and rotor speed b) The difference between stator frequency and rotor frequency c) The difference between rotor speed and slip ring speed d) The difference between rotor speed and supply frequency - **Answer: a) The difference between synchronous speed and rotor speed** Unit-02 Single phase induction motors 1. What is the principle behind the self-starting mechanism of single-phase induction motors? a) Commutation b) Double field revolving theory c) Slip rings d) Synchronous speed - **Answer: b) Double field revolving theory** 2. Which type of single-phase induction motor uses a capacitor to achieve self-starting capability? a) Shaded pole motor b) Repulsion motor c) Series motor d) Universal motor - **Answer: a) Shaded pole motor** 3. What is the purpose of using a capacitor in a capacitor start induction run motor? a) To reduce starting torque b) To improve power factor c) To increase starting torque d) To decrease efficiency - **Answer: c) To increase starting torque** https://sbte.way2poly.in/