Power Semiconductor Devices M.Tech Question Paper : vardhaman.org

College : Vardhaman College Of Engineering
Degree : M.Tech
Semester : I
Subject : Power Semiconductor Devices
Document type : Question Paper
Website : vardhaman.org

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Vardhaman Power Semiconductor Devices Question Paper

Two Year M. Tech I Semester Regular Examinations,
(Power Electronics and Electric Drives)
Date : 3 February, 2014
Time : 3 Hours
Max. Marks : 60
Answer any FIVE Questions.
All Questions carry equal marks

Related : Vardhaman College Of Engineering Discrete Structures & Automata Theory M.Tech Question Paper : www.pdfquestion.in/6413.html

February – 2014

All parts of the question must be answered in one place only

1. Draw the V-I characteristics of the following devices under ideal conditions and practical conditions. Also, explain why the two characteristics (under ideal and practical conditions) differ from each other.
i. PN junction diode
ii. IGBT
iii. MOSFET 12M

2. a) Sketch the switching characteristics of a power diode and explain. 6M
b) Write short notes on Schottky diode giving emphasis to the ohmic contacts present in it. 6M

3. a) Describe the turn-on process of a BJT with a suitable example. 7M
b) Draw the Eber-Moll’s transistor model and write short notes on the elements used in the model. 5M
4. a) Elaborately explain the turn-on and turn-off process of a power MOSFET with necessary diagrams. 8M
b) What considerations should be kept in mind while paralleling MOSFETs? 4M
5. a) Draw the V-I characteristics of an IGBT and write short notes on it. 6M
b) Discuss about isolated and non-isolated gate drive circuits for IGBT’s. 6M

6. a) Explain the turn-on and turn-off process of a thyristor. 6M
b) Describe the structure of a thyristor with a neat diagram. 6M

7. a) How can the switching losses in a power semiconductor switch be computed? Explain. 6M
b) Write short notes on the necessity of heat sinks and its sizing considerations. 6M
8. Discuss the design procedure of the following magnetic components:
a) line frequency inductors 6M
b) high frequency inductors 6M

July – 2014

M. Tech I Semester Supplementary Examinations
(Regulations: VCE-R11)
POWER SEMICONDUCTOR DEVICES
(Power Electronics and Electric Drives)
Date: 28 July, 2014
Time: 3 hours
Max Marks: 60
Answer any Five Questions.
All Questions carries equal marks.

1. a) Draw the V-I characteristics of the following devices under ideal conditions and practical conditions. Also, explain why the two characteristics (under ideal and practical conditions) differ from each other.
i. BJT
ii. Thyristor 8M
b) Mention the characteristics which are desired in a power switching device. 4M

2. a) Define:
i. Avalanche breakdown,
ii. Punch through voltage,
iii. Zener breakdown. 6M
b) Briefly explain about Fast Recovery Diodes. 6M

3. a) Explain the structure of a power BJT with a neat diagram. 8M
b) Briefly explain secondary breakdown in relation to a power transistor. 4M

4. a) What kind of effect do the parasitic capacitances in a power MOSFET have on the normal operation of the device? Show, in the form diagram, how the structure of power MOSFET differs from that of the signal level MOSFET. 8M
b) A circuit employing MOSFETs consist of resistive load. Suggest a simple drive circuit to drive the power MOSFET and briefly explain the drive circuit operation. 4M

5. a) With a neat diagram explain the structure of an IGBT. 6M
b) What are the causes of latch-up in an IGBT? How it can be avoided? 6M
6. a) Explain the uniqueness of a thyristor using its VI characteristics. 6M
b) Discuss the methods used for improving the di/dt ratings of a thyristor. 6M

7. a) Explain how the conduction and transition losses can be computed in thermal management. 6M
b) Draw the electrical equivalent circuit of the thermal model related to a power semiconducting device and explain. 6M

8. a) Write short notes on the following ferromagnetic materials:
i. Steel
ii. Soft Ferrite 6M
b) An air core inductance of 50 µH is made as wound strip of copper 40mm wide and 1.5mm thick. For cooling purpose, ½ mm spacing is used between each turn with an inner diameter of 60 mm and an outer diameter of 160mm as physical constraints. Is it possible to attain required inductance. 6M