Download GTU B.Tech 2020 Summer 6th Sem 2161708 Power Electronics Question Paper

Download GTU (Gujarat Technological University Ahmedabad) B.Tech/BE (Bachelor of Technology/ Bachelor of Engineering) 2020 Summer 6th Sem 2161708 Power Electronics Previous Question Paper

Seat No.: ________
Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER? VI EXAMINATION ? SUMMER 2020
Subject Code: 2161708 Date:28/10/2020
Subject Name: POWER ELECTRONICS
Time: 10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.

2. Make suitable assumptions wherever necessary.

3. Figures to the right indicate full marks.


MARKS
Q.1 (a) What are the requirements for good base drive of transistor?
03

(b) Explain operation of base drive circuit which is useful when
04
capability of base voltage Vb is low.

(c) In a full-wave rectifier, load resistance is 3k. The input
07
voltage is 240sin250t. Calculate the maximum value of the
current, average current, dc power output and ripple factor.


Q.2 (a) Define reverse recovery time of diode.
03

(b) Explain dynamic characteristics of power MOSFET.
04

(c) With waveforms explain single-phase half-wave controlled
07
rectifier.


OR


(c) Explain 3-? half-wave rectifier (Resistive Load) with
07
relevant waveforms.
Q.3 (a) What do you mean by Duty Cycle of Chopper?
03

(b) Explain dynamic characteristics of power BJT.
04

(c) Draw symbols and static characteristics of SCR. In which
07
ways it can be fired?


OR

Q.3 (a) What is meaning of hold time of filter- rectifier?
03

(b) What is freewheeling diode? Explain with an example.
04

(c) Explain operation of step-down converter with waveforms of
07
the various signals of circuit.
Q.4 (a) What are the benefits of isolation between the input and
03
output circuit?

(b) What are the gate drive requirements for a MOSFET?
04

(c) Explain Type E Chopper
07

OR

Q.4 (a) Define Holding current of SCR.
03

(b) How to calculate power dissipation in BJT?
04

(c) If Chopper is having a supply voltage of 100V DC and
07
operating at a frequency of 5KHz with a pulse width of 65?s.
Calculate the duty cycle, average load voltage and RMS load
voltage.
1

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Q.5 (a) Define Latching current of TRIAC.
03

(b) Explain two-level chopper using single pole double throw
04
switch.

(c) Explain the operation of the forward converter with
07
waveforms.


OR
Q.5 (a) Draw and explain Anti saturation circuit for transistor.
03
(b) Write a short note on Boost Converter.
04
(c) Differentiate between self-driven and driven inverter.
07

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2

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