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IUQP Important Questions
Anna University Chennai
Department of B.E Mechanical Engineering
Third Semester
EE6351 Electrical Drives and Controls
Nov Dec 2015 Important Questions
(Regulation 2013)
1. i) Half hour rating of a motor is 200 kW. Heating time constant is 80 min and the maximum efficiency occurs at 70% full load. Determine the continuous rating of the motor. (6)
ii) Obtain hating curve of an electric drive. (10)
2. i) Describe the selection of power rating for drive motors with regard to thermal overloading. (12)
ii) Determine the half hour rating of 4okW motor. Assume the constant losses to be 80% of full load copper losses. Thermal time constant for the motor is 2hours. (4)
3. Explain the characteristics of DC motors. (16)
4. i) Derive the Torque equation of DC motor. (8)
ii) State and explain how armature current and speed of a DC Separately excited motor will be affected when halving the armature voltage and field current with load torque remaining constant. (8)
5. i) Explain Primary resistance starter and Rotor Resistance starter. (8)
ii) Explain Two Point starters with a neat diagram. (8)
6. Explain with a neat diagram for the operation of Star Delta and DOL starters. (16)
7. (i) With circuit and waveforms explain the working principle of a three phase fully controlled
rectifier. (16) i) Explain the conventional methods of speed control for DC Shunt motor. (10)
ii) A 500 V DC Shunt motor has armature and field resistances of 1.50 and 4000 respectively. When running on no load the current taken is 5 A and the speed is 1000 rpm. Estimate the speed if the shunt field current is reduced by 15% for 30 A load current. (6)
8. Explain the conventional methods of stator side speed control of Slip ring Induction motor. (16)
9. Explain Slip Power Recovery Scheme with its types. (16)
10. A 100 kW motor having rated temperature rise of 50 deg C, has full-load efficiency of 90% and the maximum efficiency occurs at 92% full load. It has thermal time constants of 57 minutes and 48
minutes. It is cyclically loaded, 105% of full load for 1 hour and 50% of full load for the next
hour. Find the temperature rise after 3 hrs. (16)
11. Establish the heating and cooling time constants with their respective curves. (16)
12. Explain the multi quadrant operation of Electrical drives. (16)
13. Discuss briefly the various methods of electrical braking in Induction motors. (16)
14. Explain Three Point starter and Four Point Starter in detail. (16)
15. i) A squirrel cage induction motor when started by means of a star delta starter takes 200% of
full load line current and develop 40% of full load torque values, if an auto transformer with 75%
tapping were employed. (8)
ii) Explain Rotor Resistance Starter and Primary resistance starter. (8)
16. Explain the methods of speed control of DC Series motors. (16)
17. i) A 220 V, 15 kW, 850 rpm shunt motor draws 72.2 A when operating at rated condition. The
resistances of the armature and shunt field are 0.25 ohm and 1000 ohm respectively. Determine the
percentage reduction in field flux in order to obtain a speed of 1650 rpm when armature current
drawn in 40 A. (8)
ii) Explain the operation of a single phase fully controlled bridge converter with DC motor as load in detail. (8)
18. i) The rotor of a 4 pole, 50 Hz Slip ring Induction motor has a resistance of 0.3 ohm per phase and
runs at 1440 rpm at full load. Calculate the external resistance per phase which must be added
to lower the speed to 1320 rpm, the torque being the same as before. (8)
ii) Explain Cascaded speed control in Slip ring Induction motor. (8)
19. Explain the speed control methods employed to Slip ring Induction motor by using Static Scherbius system. (16)
20. Explain about three phase VSI for both 180 degree and 120 degree mode (16)
IUQP Important Questions
Anna University Chennai
Department of B.E Mechanical Engineering
Third Semester
EE6351 Electrical Drives and Controls
Nov Dec 2015 Important Questions
(Regulation 2013)
1. i) Half hour rating of a motor is 200 kW. Heating time constant is 80 min and the maximum efficiency occurs at 70% full load. Determine the continuous rating of the motor. (6)
ii) Obtain hating curve of an electric drive. (10)
2. i) Describe the selection of power rating for drive motors with regard to thermal overloading. (12)
ii) Determine the half hour rating of 4okW motor. Assume the constant losses to be 80% of full load copper losses. Thermal time constant for the motor is 2hours. (4)
3. Explain the characteristics of DC motors. (16)
4. i) Derive the Torque equation of DC motor. (8)
ii) State and explain how armature current and speed of a DC Separately excited motor will be affected when halving the armature voltage and field current with load torque remaining constant. (8)
5. i) Explain Primary resistance starter and Rotor Resistance starter. (8)
ii) Explain Two Point starters with a neat diagram. (8)
6. Explain with a neat diagram for the operation of Star Delta and DOL starters. (16)
7. (i) With circuit and waveforms explain the working principle of a three phase fully controlled
rectifier. (16) i) Explain the conventional methods of speed control for DC Shunt motor. (10)
ii) A 500 V DC Shunt motor has armature and field resistances of 1.50 and 4000 respectively. When running on no load the current taken is 5 A and the speed is 1000 rpm. Estimate the speed if the shunt field current is reduced by 15% for 30 A load current. (6)
8. Explain the conventional methods of stator side speed control of Slip ring Induction motor. (16)
9. Explain Slip Power Recovery Scheme with its types. (16)
10. A 100 kW motor having rated temperature rise of 50 deg C, has full-load efficiency of 90% and the maximum efficiency occurs at 92% full load. It has thermal time constants of 57 minutes and 48
minutes. It is cyclically loaded, 105% of full load for 1 hour and 50% of full load for the next
hour. Find the temperature rise after 3 hrs. (16)
11. Establish the heating and cooling time constants with their respective curves. (16)
12. Explain the multi quadrant operation of Electrical drives. (16)
13. Discuss briefly the various methods of electrical braking in Induction motors. (16)
14. Explain Three Point starter and Four Point Starter in detail. (16)
15. i) A squirrel cage induction motor when started by means of a star delta starter takes 200% of
full load line current and develop 40% of full load torque values, if an auto transformer with 75%
tapping were employed. (8)
ii) Explain Rotor Resistance Starter and Primary resistance starter. (8)
16. Explain the methods of speed control of DC Series motors. (16)
17. i) A 220 V, 15 kW, 850 rpm shunt motor draws 72.2 A when operating at rated condition. The
resistances of the armature and shunt field are 0.25 ohm and 1000 ohm respectively. Determine the
percentage reduction in field flux in order to obtain a speed of 1650 rpm when armature current
drawn in 40 A. (8)
ii) Explain the operation of a single phase fully controlled bridge converter with DC motor as load in detail. (8)
18. i) The rotor of a 4 pole, 50 Hz Slip ring Induction motor has a resistance of 0.3 ohm per phase and
runs at 1440 rpm at full load. Calculate the external resistance per phase which must be added
to lower the speed to 1320 rpm, the torque being the same as before. (8)
ii) Explain Cascaded speed control in Slip ring Induction motor. (8)
19. Explain the speed control methods employed to Slip ring Induction motor by using Static Scherbius system. (16)
20. Explain about three phase VSI for both 180 degree and 120 degree mode (16)
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