Download GTU BE/B.Tech 2018 Winter 5th Sem Old 150903 Power Electronics I Question Paper

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Subject Code: 150903

GUJARAT TECHNOLOGICAL UNIVERSITY

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BE - SEMESTER-V (OLD) EXAMINATION - WINTER 2018

Subject Name: Power Electronics - I

Date: 16/11/2018

Time: 10:30 AM TO 01:00 PM

Total Marks: 70

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Instructions:

1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

Q.1

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1. Explain construction & working of a SCR. Discuss two transistor analogy. [07]
2. Explain the characteristic, working and construction of IGBT. [07]

Q.2

1. Explain DIAC with its construction and V-I characteristic. [07]
2. Explain pulse transformer and opto-coupler. [07]

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Q.3

1. Write a short note on the current ratings and voltage ratings of thyristor. [07]
2. Explain the resistance triggering and R-C triggering method. What is advantage of RC triggering over resistance triggering? [07]

OR

1. Explain the turn-on and turn-off characteristics of an SCR. [07]

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2. With neat circuit diagram & waveform explain UJT oscillator triggering. [07]

Q.4

1. Write a short note on buck-boost converter. [07]
2. What is chopper? Explain step-up chopper. [07]

OR

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1. With a neat circuit diagram and waveforms describe the Morgan’s Chopper circuit. State its applications & limitations. [07]
2. Describe the working principle of Jones chopper with neat circuit diagram. [07]

Q.5

1. Explain in brief various control strategies of a chopper. [07]
2. Discuss four quadrant operations of DC drives. [07]

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OR

1. Explain phase locked loop (PLL) control of dc motor. [07]
2. Explain how regenerative braking can be achieved for a separately excited DC motor using DC-DC converter. [07]
3. With neat circuit diagram and waveforms, explain the operation of a two-quadrant chopper capable to give forward motoring and forward regenerative operation. [07]

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