Download GTU B.Tech 2020 Summer 4th Sem 3140915 Power Electronics Question Paper

Download GTU (Gujarat Technological University Ahmedabad) B.Tech/BE (Bachelor of Technology/ Bachelor of Engineering) 2020 Summer 4th Sem 3140915 Power Electronics Previous Question Paper

Seat No.: ________
Enrolment No.___________


GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER? IV EXAMINATION ? SUMMER 2020
Subject Code: 3140915 Date:04/11/2020
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) Explain IGBT with its physical construction diagram
03
and characteristics.

(b) Draw the SCR static V-I characteristics and explain
04
its behavior in forward conduction, forward blocking
and reverse blocking modes.

(c) Explain working of 1- semi converter with the help
07
of voltage and current waveform under resistive load.


Q.2 (a) Compare the RC firing circuit and R firing circuit
03
based on its circuit diagram.

(b) Describe the effect of high switching frequency on
04
harmonics spectrum in single phase full bridge
inverter.

(c) Derive the output voltage equation in case of buck
07
and boost converter and draw the comparison.


OR


(c) Draw the circuit diagram of three-phase full converter
07
connected to RL load with continuous conduction.
Draw the waveforms of output voltage, output current
for firing angle equal to 60?.
Q.3 (a) Write application of cycloconverters.
03

(b) Write advantages and disadvantages of PWM
04
technique to generate gate pulse.

(c) Draw necessary waveforms and explain working of
07
single phase full controlled rectifier circuit with R-L
l
oad.


OR

Q.3 (a) Justify the statement why SCR is not suitable for dc
03
to ac converter for low power applications.




(b) Explain construction of Power MOSFET.
04

(c) Describe the working of a single phase full bridge
07
inverter with relevant circuit and waveforms for R-L
Load.
Q.4 (a) Derive only expression of RMS output voltage of
03
single phase full wave AC voltage controller with R
load.

(b) Write important features of sinusoidal pulse width
04
modulation used in PWM inverters.
1

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(c) Explain working of 3 phase bridge inverter with star
07
connected resistive load with 180? mode using gate
signals, output phase voltage and line v
oltage.

OR

Q.4 (a) Describe the working of freewheeling diode in Phase
03
controlled rectifier.

(b) Write a short note on matrix converter.
04

(c) Explain working of 3 phase bridge inverter with star
07
connected resistive load with 120? mode using gate
signals, output phase voltage and line voltage.
Q.5 (a) List the various voltage control techniques in DC-DC
03
converters.

(b) Give four points of difference between on-off control
04
and phase angle control.

(c) Explain the working principal of buck-boost
07
converter with circuit diagram of different modes of
operation.


OR
Q.5 (a) Draw the output voltage waveform of three-phase
03
half-wave controlled rectifier with the R-load.
(b) State at least two reasons to control or eliminate the
04
harmonics in inverters. List out different techniques
to eliminate harmonics in inverter.
(c) Explain the parallel operation of SCR.
07
2

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