Download GTU BE/B.Tech 2019 Winter 5th Sem Old 150903 Power Electronics I Question Paper

Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2019 Winter 5th Sem Old 150903 Power Electronics I Previous Question Paper

1
Seat No.: ________ Enrolment No.___________

GUJARAT TECHNOLOGICAL UNIVERSITY

BE - SEMESTER ?V (Old) EXAMINATION ? WINTER 2019
Subject Code: 150903 Date: 04/12/2019

Subject Name: Power Electronics - I
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.

Q.1 (a) Define and explain the need of snubber circuit. Draw such circuit for SCR and
give guidelines for selecting its components.
07
(b) Explain voltage ratings of SCR. 07

Q.2 (a) What do you mean by freewheeling action? Explain How diode can provide
freewheeling action?
07
(b) State and explain the various turn-on methods for SCR. 07
OR
(b) Draw and explain two transistor analogy of a Thyristor. 07

Q.3 (a) Draw the circuit of a single phase fully controlled converter with R-L load.
Derive necessary equations and sketch output waveforms.
07
(b) Explain V-I characteristic & working of Triac. 07
OR
Q.3 (a) Using relevant circuit diagram and waveforms, explain Complimentary forced
commutation (class C) method.
07
(b) For a single phase fully controlled converter with RLE load, draw the circuit
diagram and waveforms of input & output voltages and currents, and voltage
across SCR. Derive the mathematical expressions of output voltage.
07

Q.4 (a) Discuss the various techniques of improving power factor in phase controlled
converters. Explain PWM techniques in detail with necessary waveforms.
07
(b) Write a note on single phase dual converter showing the circuit configuration
and details of operation. What are the applications of such a dual converter?
07
OR
Q.4 (a) Explain the operation of three phase half wave controlled converter with RL
load. Sketch the associated waveforms for ? = 60?.
07
(b) With a neat circuit diagram and waveforms describe the Morgan?s Chopper
circuit. State its applications & limitations.
07

Q.5 (a) State the principles of DC motor speed control. Explain the single phase semi-
converter DC motor drive.
07
(b) Explain the working of step-down and step-up chopper. Give the comparison
between step-down and step-up chopper.
07
OR

Q.5 (a) What are the control strategies for chopper? Explain in brief. 07
(b) Discuss constant H.P and constant Torque operation of speed control of motors.
Specify their field of applications.
07

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