Download PTU B.Tech 2020 March Automation-And-Robotics Question Paper 4th Sem BTAR 401 Power Electronics & Motors

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Roll No. HEEEEEEE [ ] Total No. of Pages : 02

Total No. of Questions : 09

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B.Tech.(Automation & Robotics) (2012 & Onward) (Sem.-4)

POWER ELECTRONICS & MOTORS

Subject Code : BTAR-401

M.Code : 63014

Time : 3 Hrs. Max. Marks : 60

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INSTRUCTION TO CANDIDATES :

1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks each.
2. SECTION-B contains FIVE questions carrying FIVE marks each and students have to attempt any FOUR questions.
3. SECTION-C contains THREE questions carrying TEN marks each and students have to attempt any TWO questions.

SECTION-A

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1. Answer briefly :
   1. Draw symbol and V-I characteristics of SCR:
   2. Why TRIAC is preferred over DIAC?
   3. How the inductive load affects the output voltage and current in controlled rectifiers?
   4. List the applications of choppers.
   5. Explain the basic difference between voltage - source inverter and current - source inverter.

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   6. What is snubber circuit?
   7. What are the causes of overvoltages in thyristors circuits?
   8. What is the need of freewheeling diode? Show its effect with the help of waveform.
   9. What is pulse width modulation control method in inverters?
   10. What is duty cycle in choppers?

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SECTION-B

1. Draw and explain the two transistor model of SCR.
2. Why equalizing networks are required in series connection of SCRs?

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3. What do you mean by commutation of SCR? Explain class-A and class-B methods.
4. Explain single-phase to single-phase step-down cycloconverter with discontinuous load current by showing its waveforms.
5. Draw and explain three-phase bridge inverter using 180° mode VSI. Draw its waveforms upto first four steps along with relevant circuits. Also draw waveforms for Vab, Vbc, Vca.

SECTION-C

1. 1. Describe various operating modes of SCR with the help of proper diagrams.

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   2. Explain the method to control the speed of DC motor drives.
2. 1. Why 3-phase to 1-phase cycloconverter requires positive and negative group phase-controlled converters? How should the firing angles of the two converters be controlled?
   2. Discuss the working of a-current-commutated chopper with relevant voltage and current waveforms.

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3. Describe modified McMurray full - bridge single - phase inverter with relevant voltage and current waveforms.

NOTE : Disclosure of Identity by writing Mobile No. or Making of passing request on any page of Answer Sheet will lead to UMC against the Student.

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