GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER- VI EXAMINATION — SUMMER 2020
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Subject Code: 2160902 Date:26/10/2020Subject Name: POWER ELECTRONICS - 11
Time: 10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
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MARKS
Q.1 (a) Classify AC converters. 03
(b) Explain requirement and function of gate driver circuit. 04
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(c) Explain 3-phase inverter operation with 180° conduction period. 07
Draw waveform of gate voltage, phase voltage and line voltage for resistive Y connected load.
Q.2 (a) Explain line commutation with waveforms. 03
(b) Explain concept of Pulse Width Modulation. 04
(c) Discuss effect of modulation index and carrier to modulation 07
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frequency ratio on output of sine PWM technique.OR
(c) Discuss concept of space vectors. How more output voltage can 07
be obtained in SVPWM compared to sine PWM technique.
Q.3 (a) Compare cycloconverter with matrix converter. 03
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(b) Classify AC voltage controller. Draw waveform of single phase 04
full wave AC voltage controller with RL load and firing angle=60°.
(c) With circuit diagram explain basic principle of 3-phase 07
cycloconverter.
OR
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Q.3 (a) Explain integral cycle control technique in brief. 03
(b) Explain selected harmonic-elimination technique in brief. 04
(c) Can we control frequency of AC voltage controller? Justify the 07
answer by explaining operation of 3-phase full wave AC controller.
Q.4 (a) Discuss various types of load that can be connected with power 03
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electronics converters.(b) What is R-L-E load? How is it different than R-L load? 04
(c) How three single phase cycloconverter can be operated as three 07
phase cycloconverter? Explain with necessary diagrams.
OR
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Q.4 (a) Explain principle of current source inverter in brief. 03
(b) Explain single phase cycloconverter in brief. 04
(c) With diagram explain basic principle of matrix converter. 07
Q.5 (a) Explain load commutated cycloconverter in brief. 03
(b) Explain application of load commutated thyristors inverter. 04
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(c) What is static Kramer drive? With circuit diagram explain its 07
operation.
OR
Q.5 (a) Discuss different region of speed torque characteristics of 03
induction motor.
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(b) Explain in brief the self-controlled synchronous motor drive. 04
(c) Discuss V/f control technique of induction motor drive. 07
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