1
Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
PDDC SEMESTER-V EXAMINATION WINTER 2018
Subject Code:X50903 Date: 20/11/2018
Subject Name: Power Electronics-II
Time: 10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1

Explain working of three phase 180° mode VSI with necessary waveforms.
07

Explain principle of integral cycle control in case of AC to AC voltage controllers. Draw necessary waveforms and derive the formula for rms output voltage.
07
Q.2

Give classification of inverter circuit on different basis. Compare VSI and CSI.
07

Explain harmonic reduction in inverter by transformer connection and stepped wave inverters.
07
OR

What do you mean by PWM? List the various PWM methods and explain any one of them in brief.
07
Q.3

Explain two stage sequence control of AC voltage controller with transformer connection. List its advantages over single phase full wave voltage controllers.
07

Explain working of three phase to three phase cycloconverter.
07
OR
Q.3

Explain three phase full wave voltage controller with star connected load.
07

Explain working of single phase step down cycloconverter with continuous load current. Draw necessary waveforms.
07
Q.4

Explain v/f control of an induction motor.
07

Explain DC and AC link Scherbius drives for speed control of slip ring induction motor.
07
OR
Q.4

Explain speed control of slip ring induction motor by rotor resistance control with chopper.
07

Explain the operation of a self controlled (closed loop) synchronous motor drive fed from a cycloconverter to control the speed of synchronous motor with necessary schematic diagram.
07
Q.5

Explain basic working principle of HVDC transmission with necessary circuit diagram.
07

Write a short note on active power filters.
07
OR
Q.5

Explain basic working principle of FACTS devices with necessary circuit diagram.
07

Write a short note on AC and DC static switches.
07