important notes in powerelectronics

Important Questions in  Power Electronics  EE2301  EE 2301

subject for NOV/DEC 2011 ANNA UNIVERSITY EXAMINATIONS FOR THIRD YEAR 5th semester EEE Students

EE2301 Power Electronics

UNIT I

1.      Discuss the transfer, output and switching characteristics of MOSFET.

2.      Explain the switching characteristics of IGBT with neat circuit diagram and waveforms.

3.      Write short notes on (i) snubber circuit for BJT and (ii) commutation circuit for SCR

4.      Compare the performance characteristics of MOSFET and BJT.         

UNIT II

1.      Describe the operation of a two pulse bridge converter using 4 SCRs with relevant diagrams and waveforms. Discuss the operation of the above converter in conversion and inversion modes using RLE load.

2.      Explain the principle of operation of dual converter with neat power circuit diagram.

3.      Explain the operation of 3f full converter with neat diagrams and waveforms. Also derive expression for its output voltage equation.

4.      With suitable circuit diagram and waveforms, explain how a converter can act as a rectifier and an inverter

UNIT III

1.      Explain the operation of boost and buck-boost converter with neat circuit diagram and waveforms.

2.      Explain the various modes of operation of boost converter with neat circuit diagram and waveforms.  

3.      A DC chopper has an input voltage of 200V and a load of 15 ohm resistance. When the chopper is ON, its voltage drop is 2.5V for a duty cycle of 0.5. Find (i) average output voltage, (ii) RMS output voltage and (iii) power delivered to the load

4.      Discuss the operating principle of a DC step down chopper with suitable   diagram. Derive an expression for its average output voltage

UNIT IV

1.      Explain different methods of voltage control adopted in an inverter with neat diagrams.

2.      What is PWM? List the various PWM techniques and explain any one of them.

3.      Describe the working of a single phase full bridge inverter with relevant circuit and waveforms.

4.      Explain the operation of a three phase voltage source inverter operating under 180° mode of conduction.  

5.      Describe the working of a single phase auto sequential commutated current source inverter with relevant waveforms.

UNIT V

1.      Describe the principle of 1 phase to 1 phase step down cyclo-converter with neat sketches and waveforms.

2.      Explain the operation of multi-stage sequence control of AC voltage controllers.

3.      Describe the 3 phase to 3 phase cyclo-converters using 18 thyristors. Also derive the expression for fundamental RMS value of per phase output voltage for a low frequency m-pulse cyclo-converter.

4.      Explain the operation of 1 phase full-wave AC voltage controller with neat circuit diagram and waveforms. Also derive an expression for the output voltage.