7/30/2019 PE 2010 QP

1/3

Reg. No. :

B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2010

Fifth Semester

Electrical and Electronics Engineering

EE 2301 POWER ELECTRONICS

(Common to Instrumentation and Control Engineering)

(Regulation 2008)

Time : Three hours Maximum : 100 Marks

Answer ALL questions

PART A (10 2 = 20 Marks)

1. Draw the turn-on characteristics of TRIAC and mark the timings td, tr andton.

2. What are the factors that influence the turn-off time of a thyristor?

3.

Draw the circuit diagram of single phase dual converter.

4. Define the term voltage ripple factor, current ripple factor.5. Mention any two disadvantages of frequency modulation control strategy.6. What are the advantages of ZVS when compared to ZCS?7. Differentiate VSI from CSI.8. List various applications of phase controlled converters.9. What is meant by cycloconverter?10. Write the output R.M.S. voltage for single phase AC voltage controller with

resistance load.

Question Paper Code :53141

4

2

1

4

2

1

4

2

1

www.Vidyarthiplus.com

www.Vidyarthiplus.com

7/30/2019 PE 2010 QP

2/3

531412

PART B (5 16 = 80 Marks)

11. (a) Explain the operation of IGBT with the help of neat structural diagramand suitable wave forms. (16)

Or

(b) (i) Draw the turn-off characteristics of an SCR and explain themechanism of turn-off. (8)

(ii) What are the different methods for turning off an SCR? Explain all

methods in detail. (8)

12. (a) (i) Describe the operation of a single phase two pulse bridge converterusing 4 SCR'S with relevant waveforms. (10)

(ii) Discuss the working of above converter in the converter mode with

RLE load. (6)

Or

(b) (i) A single phase semi converter is operated from 120 V 50 Hz ac

supply. The load current with an average value Idc is continuous

and ripple free firing angle 6= . Determine.

(1) Displacement factor

(2) Harmonic factor of input current

(3) Input power factor. (10)

(ii) Write a note on battery charger. (6)

13. (a) (i) Discuss the principle of operation of DC-DC step down chopper withsuitable waveform. Derive an expression for its average DC output

voltage. (8)

(ii) A step-down dc chopper has a resistive load of R = 15 and inputvoltage Edc = 200 V. When the chopper remains ON, its voltage

drop is 2.5 for a duty cycle of 0.5.

Calculate :

(1) Average and r.m.s value of output voltage

(2) Power delivered to the load. (8)

Or

(b) Draw the circuit of CUK regulator and explain its working principle with

necessary waveform in detail. (16)

4

2

1

4

2

1

4

2

1

www.Vidyarthiplus.com

www.Vidyarthiplus.com

7/30/2019 PE 2010 QP

3/3

531413

14. (a) (i) Describe the working of a 1 pull bridge inverter with relevantcircuit and waveforms. (8)

(ii) What is PWM? List the various PWM techniques and explain any

one of them. (8)

Or

(b) Explain the Harmonic reduction by transformer corner lines and stepped

wave inverters. (16)

15. (a) (i) Describe the operation of single phase full wave a.c voltagecontroller with the help of voltage and current waveform. Also

derive the expression for average value of output voltage. (10)

(ii) For a single phase a.c regulator feeding a resistance load, show that

power factor is given by the expression ( )2

1

2

2sin1

+

x . (6)

Or

(b) (i) Describe three-phase to three phase cycloconverter with relevant

circuit arrangement using 18 thyristors. (8)

(ii) Show that the fundamentals RMS value of per phase output voltage

of low frequency for an m-pulse cycloconverter is given by

=

nmEpnEor sin . (8)

4

2

1

4

2

1

4

2

1

www.Vidyarthiplus.com

www.Vidyarthiplus.com