GTU BE/B.Tech 2018 Winter Question Papers || Gujarat Technological University
Subject Name: Power Electronics — II
Time: 02:30 PM TO 05:00 PM
Subject Code: 2160902
GUJARAT TECHNOLOGICAL UNIVERSITY
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BE - SEMESTER-VI (NEW) EXAMINATION - WINTER 2018Subject Name: Power Electronics — II
Time: 02:30 PM TO 05:00 PM
Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
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| Q.1 | (a) What is an inverter? List a few industrial applications of inverters. | 03 |
| (b) Describe about PWM control in inverters. | 04 | |
| (c) Discuss the principle of working of a three-phase bridge inverter with an appropriate circuit diagram. Draw gate signal, phase voltage and line voltage waveforms for 180° conduction of SRCs with star connected load. | 07 | |
| OR | ||
| (c) With neat circuit diagram and waveforms explain 3-F ac voltage controller with Y connected load. | 07 | |
| Q.2 | (a) What are the control strategies for the regulation of output voltage in ac voltage controllers? | 03 |
| (b) Explain the concept of ON-OFF or integral cycle control. | 04 | |
| (c) Discuss the principle of phase control in single-phase full-wave ac voltage controller with RL load. Illustrate your answer with relevant circuit diagram and waveforms. Derive expression for rms output voltage. | 07 | |
| OR | ||
| (c) Draw the circuit diagram and waveforms for current source inverter and give the applications of current source inverter. | 07 | |
| Q.3 | (a) A single phase full bridge inverter is connected to a dc source of Vs. Resolve the output voltage wave shape into Fourier series. | 03 |
| (b) Explain the operation of a single phase parallel commutated inverter without freewheeling diode, with the help of voltage and current waveforms. | 04 | |
| (c) Define: (1). Harmonic factor, (2). Total Distortion Factor and (3). Distortion Factor. Compare voltage source inverter and current source inverter in brief. | 07 | |
| OR | ||
| (c) What is space vector modulation? Explain the working principle of SVM(Space Vector Modulation). | 07 | |
| Q.4 | (a) List the speed control methods for synchronous motor. | 03 |
| (b) Enlist advantages and disadvantages of cycloconverter. | 04 | |
| (c) Draw and explain the operation of three phase cycloconverter with relevant waveforms. | 07 | |
| OR | ||
| (c) Draw and Discuss briefly self-controlled synchronous motor drive. Explain operation of single phase to three phase cycloconverter. Derive an emf equation for the line-commutated phase-controlled cycloconverters. | 07 | |
| Q.5 | (a) Draw the equivalent circuit of an induction motor referred to stator side. | 03 |
| (b) Explain the speed-torque characteristic of an induction motor. | 04 | |
| (c) Draw and explain cycloconverter based induction motor drive. | 07 | |
| OR | ||
| (a) Explain in brief the different speed control methods for induction motor. | 03 | |
| (b) Discuss closed loop V/f technique used for induction motor drive. | 07 | |
Date: 27/11/2018
Total Marks: 70
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