GTU B.Tech 2020 Winter Question Papers || Gujarat Technological University
GUJARAT TECHNOLOGICAL UNIVERSITY
BE- SEMESTER-V (NEW) EXAMINATION - WINTER 2020
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Subject Code:3151106 Date:27/01/2021
Subject Name:Power Electronics
Time:10:30 AM TO 12:30 PM Total Marks: 56
Instructions:
- Attempt any FOUR questions out of EIGHT questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
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| Marks | |
| Q.1 (a) What is SCR commutation? Explain the self commutation in brief. | 03 |
| (b) Make the comparison between Power MOSFET and IGBT. | 04 |
| (c) A 100 A SCR is to be used in parallel with 50 A SCR. The on state voltage drops of the SCRs are 2 and 1.5 V, respectively. Calculate the series resistance that should be connected with each SCR if two SCRs have to share the total current 150 A in proportion to their rating | 07 |
| Q.2 (a) Explain the di/dt and dv/dt rating of SCR. | 03 |
| (b) Explain the resistance triggering circuit for SCR. | 04 |
| (c) Explain the operation of single phase fully controlled bridge converter with resistive and inductive load. Draw the associated waveforms. | 07 |
| Q.3 (a) What is the function of Chopper? Explain the working of type D chopper. | 03 |
| (b) With help of waveform explain the Time Ratio Control strategy of chopper. | 04 |
| (c) With help of neat circuit diagram and waveforms, explain the operation of PWM inverter with resistive load. | 07 |
| Q.4 (a) What are the applications of chopper? Explain the working of class E chopper. | 03 |
| (b) Compare the step up and step-down chopper. | 04 |
| (c) With help of neat circuit diagram and waveforms, explain the operation of full bridge square wave inverter. | 07 |
| Q.5 (a) List the types of commutation and explain class C forced commutation. | 03 |
| (b) Compare SCR and TRIAC. | 04 |
| (c) What are the on conditions for SCR? Explain the RC triggering circuit in detail. | 07 |
| Q.6 (a) Design and explain the operation of current source inverter. | 03 |
| (b) Design and explain working of snubber circuit of SCR. | 04 |
| (c) Draw and explain the structure of power MOSFET. Also explain principle of operation and V-I characteristics of power MOSFET. | 07 |
| Q.7 (a) Compare Power supply and SMPS. | 03 |
| (b) Explain the working of forward converter SMPS. | 04 |
| (c) Write short note on On-line UPS. | 07 |
| Q.8 (a) Compare EMI and EMC. | 03 |
| (b) Explain the working of separately excited DC motor drive. | 04 |
| (c) Write short note on series loaded half bridge DC-DC converter. | 07 |
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