B.E./B.Tech. DEGREE EXAMINATION, APRIL/MAY 2010

Third Semester

Mechanical Engineering

ME2205 — ELECTRICAL DRIVES AND CONTROL

(Common to Chemical Engineering, Production Engineering)

(Regulation 2008)

Time: Three hours Maximum: 100 Marks

Answer ALL Questions

PART A — (10 × 2 = 20 Marks)

Third Semester

Mechanical Engineering

ME2205 — ELECTRICAL DRIVES AND CONTROL

(Common to Chemical Engineering, Production Engineering)

(Regulation 2008)

Time: Three hours Maximum: 100 Marks

Answer ALL Questions

PART A — (10 × 2 = 20 Marks)

1. State the advantages of Electric Drive.

2. Give the formula for computing power requirement for a liner movement.

3. Write down the torque equation of a DC shunt motor and give the significance of flux.

4. A 6-pole, 3-phase induction motor operating on a 50 Hz supply has rotor emf frequency as 2 Hz. Determine

(a) slip and

(b) the rotor speed.

5. Why are centrifugal switches provided on many 1-phase induction motors?

6. Draw the block diagram of soft starter for an induction motor.

7. Compare the chopper control and phase control schemes for DC motor drives.

8. State the different methods of speed control of DC series motor.

9. What is advantage of v/f speed control of Induction Motor?

10. Draw the block diagram of speed control scheme for a slip ring Induction motor.

2. Give the formula for computing power requirement for a liner movement.

3. Write down the torque equation of a DC shunt motor and give the significance of flux.

4. A 6-pole, 3-phase induction motor operating on a 50 Hz supply has rotor emf frequency as 2 Hz. Determine

(a) slip and

(b) the rotor speed.

5. Why are centrifugal switches provided on many 1-phase induction motors?

6. Draw the block diagram of soft starter for an induction motor.

7. Compare the chopper control and phase control schemes for DC motor drives.

8. State the different methods of speed control of DC series motor.

9. What is advantage of v/f speed control of Induction Motor?

10. Draw the block diagram of speed control scheme for a slip ring Induction motor.

PART B — (5 × 16 = 80 Marks)

11. (a) (i) Briefly explain the various factors that will influence the choice of an electrical drive. (Marks 8)

(ii) Explain the method of estimating equivalent continuous power rating of a motor for short time load applications. (Marks 8)

Or

(b) (i) Explain the different classes of motor duty with the equations. (Marks 8)

(ii) The temperature rise of motor after operating for 30 minutes on full load is 20°C and after another 30 minutes it becomes 30°C on the same load. Find the final temperature rise and time constant. (Marks 8)

12. (a) (i) From electrical characteristic, derive the mechanical characteristic of DC series motor. (Marks 8)

(ii) Explain the dynamic braking of DC shunt motor with the required diagram and equations. (Marks 8)

Or

(b) (i) Derive the Speed-Torque characteristic of 3-phase slip ring induction motor. (Marks 8)

(ii) Explain the principle operation of capacitor start and run 1-phase Induction Motor. (Marks 8)

13. (a) (i) With a neat diagram explain the operation of four point starter. Also mention the advantages of this over a three point starter. (Marks 12)

(ii) Draw the control circuit for time limit acceleration of DC shunt motor. (Marks 4)

Or

(b) State the various starting methods of squirrel cage induction motor. Explain any two of them. (Marks 16)

14. (a) (i) Explain the operation of armature control of a DC shunt motor. (Marks 8)

(ii) Draw and explain the four quadrant speed control of DC motor using various choppers. (Marks 8)

Or

(b) (i) With the block diagram explain the operation of armature and field control of DC motor drive using controlled rectifiers. (Marks 12)

(ii) Name the different flux control methods adopted for DC series motor. (Marks 4)

15. (a) Explain the operation of speed control techniques employed for 3-phase squirrel cage induction motor. (Marks 16)

Or

(b) What is meant by slip power recovery scheme? Explain with the necessary diagram. (Marks 16)

(ii) Explain the method of estimating equivalent continuous power rating of a motor for short time load applications. (Marks 8)

Or

(b) (i) Explain the different classes of motor duty with the equations. (Marks 8)

(ii) The temperature rise of motor after operating for 30 minutes on full load is 20°C and after another 30 minutes it becomes 30°C on the same load. Find the final temperature rise and time constant. (Marks 8)

12. (a) (i) From electrical characteristic, derive the mechanical characteristic of DC series motor. (Marks 8)

(ii) Explain the dynamic braking of DC shunt motor with the required diagram and equations. (Marks 8)

Or

(b) (i) Derive the Speed-Torque characteristic of 3-phase slip ring induction motor. (Marks 8)

(ii) Explain the principle operation of capacitor start and run 1-phase Induction Motor. (Marks 8)

13. (a) (i) With a neat diagram explain the operation of four point starter. Also mention the advantages of this over a three point starter. (Marks 12)

(ii) Draw the control circuit for time limit acceleration of DC shunt motor. (Marks 4)

Or

(b) State the various starting methods of squirrel cage induction motor. Explain any two of them. (Marks 16)

14. (a) (i) Explain the operation of armature control of a DC shunt motor. (Marks 8)

(ii) Draw and explain the four quadrant speed control of DC motor using various choppers. (Marks 8)

Or

(b) (i) With the block diagram explain the operation of armature and field control of DC motor drive using controlled rectifiers. (Marks 12)

(ii) Name the different flux control methods adopted for DC series motor. (Marks 4)

15. (a) Explain the operation of speed control techniques employed for 3-phase squirrel cage induction motor. (Marks 16)

Or

(b) What is meant by slip power recovery scheme? Explain with the necessary diagram. (Marks 16)