Download GTU B.Tech 2020 Winter 5th Sem 3151106 Power Electronics Question Paper

Download GTU (Gujarat Technological University Ahmedabad) B.Tech/BE (Bachelor of Technology/ Bachelor of Engineering) 2020 Winter 5th Sem 3151106 Power Electronics Previous Question Paper

Seat No.: ________
Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE- SEMESTER?V (NEW) EXAMINATION ? WINTER 2020
Subject Code:3151106 Date:27/01/2021
Subject Name:Power Electronics
Time:10:30 AM TO 12:30 PM Total Marks: 56
Instructions:
1. Attempt any FOUR questions out of EIGHT questions.

2. Make suitable assumptions wherever necessary.

3. Figures to the right indicate full marks.



Marks
Q.1 (a) What is SCR commutation? Explain the self commutation in brief.
03

(b) Make the comparison between Power MOSFET and IGBT.
04

(c) A 100 A SCR is to be used in parallel with 50 A SCR. The on state
07
voltage drops of the SCRs are 2 and 1.5 V, respectively. Calculate the
series resistance that should be connected with each SCR if two SCRs
have to share the total current 150 A in proportion to their rating


Q.2 (a) Explain the di/dt and dv/dt rating of SCR.
03

(b) Explain the resistance triggering circuit for SCR.
04

(c) Explain the operation of single phase fully controlled bridge converter
07
with resistive and inductive load. Draw the associated waveforms.
Q.3 (a) What is the function of Chopper? Explain the working of type D chopper.
03

(b) With help of waveform explain the Time Ratio Control strategy of
04
chopper.

(c) With help of neat circuit diagram and waveforms, explain the operation of
07
PWM inverter with resistive load.




Q.4 (a) What are the applications of chopper? Explain the working of class E
03
chopper.

(b) Compare the step up and step down chopper.
04

(c) With help of neat circuit diagram and waveforms, explain the operation of
07
full bridge square wave inverter.
Q.5 (a) List the types of commutation and explain class c forced commutation.
03

(b) Compare SCR and TRIAC.
04

(c) What are the on conditions for SCR? Explain the RC triggering circuit in
07
detail.



Q.6 (a) Design and explain the operation of current source inverter.
03

(b) Design and explain working of snubber circuit of SCR.
04

(c) Draw and explain the structure of power MOSFET. Also explain principle
07
of operation and V-I characteristics of power MOSFET.
Q.7 (a) Compare Power supply and SMPS.
03

(b) Explain the working of forward converter SMPS.
04

(c) Write short note on On-line UPS.
07



Q.8 (a) Compare EMI and EMC.
03
(b) Explain the working of separately excited DC motor drive.
04
(c) Write short note on series loaded half bridge DC-DC converter.
07

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