Power Electronics 2 Question Paper - Dec 18 - Electronics Engineering (Semester 7)

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Power Electronics 2 - Dec 18

Electronics Engineering (Semester 7)

Total marks: 80
Total time: 3 Hours INSTRUCTIONS
(1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Draw neat diagrams wherever necessary.

1.a. Compare fully controlled bridge converter and semi-converter.

(5 marks) 00

1.b. List the factors affecting the speed of an induction motor.

(5 marks) 00

1.c. Explain the principle of operation of DC motors.

(5 marks) 00

1.d. State true or false with justification: The transfer function model of a buck converter is of second-order.

(5 marks) 00

1.e. Give advantage of induction heating when compared to other conventional methods of heating.

(5 marks) 00

2.a. Derive an expression for Overlap angle (

$\mu$ ) and output voltage for a three phase fully controlled bridge rectifier with source inductance.

(10 marks) 00

2.b. Explain the SVM technique for 3-phase voltage source inverters. Draw sector diagram.

(10 marks) 00

3.a. Derive and explain the average state space model of Buck Converter. Use this state space model to derive equation for output voltage of the converter at equilibrium condition(dv/dt=0)

(10 marks) 00

3.b. Explain various feedback control method for DC-DC converters. Which method is best suitable for efficient control? Which method does not require mathematical model of the converter?

(10 marks) 00

4.a. A separately excited DC motor is supplied from 230V, 50Hz.AC source through a single phase half wave controlled converter. Its field is fed through single phase semi-converter with zero degree firing angle delay.

Motor resistance= 0.70 $\Omega$ ; motor constant =0.5Vsec/rad.

For a rated load torque of 15 N-m at 1000 rpm and for continuous ripple free current, determine

a. Firing angle delay of armature converter.

b. RMS value of thyristor current and free-wheeling current.

(10 marks) 00

4.b. Explain the working of single-phase full converter drive for separately excited DC motor.

(10 marks) 00

5.a. Compare the V/f and stator voltage speed control methods for an induction motor. which method is more popular in practice? Justify your answer.

(10 marks) 00

5.b. Draw and explain the torque speed characteristics of an induction motor. Explain which region of the characteristics is most suitable for the stable operation of the motor.

(10 marks) 00

Write short notes on

6.i. Static Scherbius drive.

(5 marks) 00

6.ii. Battery charging system.

(5 marks) 00

6.iii. Role of DC-DC converter in SMPS circuits.

(5 marks) 00

6.iv. Regenerative braking of induction motor.

(5 marks) 00

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