Power Electronics Question Paper - Jun 17 - Electronics Engineering (Semester 7)

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Power Electronics - Jun 17

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. Attempt the following Questions (any4)

1.a. Draw the two transistor model of SCR ? State all the current equation of $IC_1$, $IC_2$, $I_A$

(5 marks) 13301

1.b. Why forced commutation is required in DC to AC converter

(5 marks) 00

1.c. Calculate output voltage for a step down chopper with Vin = 200 V and duty cycle = 0.25

(5 marks) 00

1.d. What is the need of freewheeling diode in rectifiers state with example

(5 marks) 00

1.e. Explain brief why harmonic neutralization is necessary in output of inverter

(5 marks) 00

1.f. Define and explain performance parameter of controlled rectifier

(5 marks) 00

2.a. What do you mean by communication of SCR ? State the various methods of communication of SCR, explain force method in detail

(10 marks) 00

2.b. What is the difference between a cycloconverter and an AC voltage controller, explain single phase converters with waveforms

(10 marks) 00

3.a. Explain the basic structure and static characteristics of IGBT with creation of inversion layer and conductivity modulation

(10 marks) 00

3.b. Draw and explain buck boost converter with the help of circuit diagram and waveforms , Derive the relation for load voltage

(10 marks) 00

4.a.

(10 marks) 00

4.b. Explain the static I-V characteristics of TRIAC ? Straight forward and reverse characteristics compare DIAC - TRIAC

(10 marks) 00

5.a. Why the protection of SCR in necessary? State the various protection of SCR, Explain any one method in detail

(10 marks) 00

5.b. State comparison between control strategies of chopper 1.PWM control 2. Variable frequency control 3. Current limit control. Step down chopper feeds a resistive load of 10 ohms from 100 V DC supply. Calculate duty cycle required to that power dissipation in load is 100watts

(10 marks) 00

6.Write short note on (any 4):

6.a. Half wave controlled rectifier with R load with waveforms

(5 marks) 00

6.b. Full bridge inverter with waveforms

(5 marks) 00

6.c. Cuk regulators

(5 marks) 00

6.d.

(5 marks) 00

6.e. Compare IGBT and power BJT

(5 marks) 00

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