POWER ELECTRONICS

                               ASSIGNMENT QUESTIONS

          UNIT-1

1)    What are the important applications of power electronics?

2)    Explain peripheral effects of power converter system.

3)    With the circuit diagram, input and output waveforms, explain the control characteristics of SCR and IGBT.

4)    Mention and explain the different types of power electronic converter systems. Draw their circuit diagram, input/output characteristics.

5)    Give symbol, characteristic features of the following devices:

i) GTO    ii) TRIAC    iii) MOSFET      iv) MCT

UNIT-2

1)    Draw the equivalent model of BJT and explain the switching characteristics of power transistor.

2)    Discuss the different methods of providing isolation of gate drive circuits from power circuit.

3)    Compare the BJT and MOSFET.

4)    What is the necessity of base drive control in a power transistor? Explain proportional base control.

5)    With necessary sketches, explain briefly the switching characteristics of an IGBT.

6)    Numerical problems on BJT.

UNIT-3

1)    Using two transistor analogy explain the principle of turn on of an SCR and device an expression for anode current in terms of transistor parameters.

2)    Mention the various types of triggering methods used to turn on SCR.Which is universal method and why?

3)    With the help of circuit diagram and output waveform explain about Resistance triggering circuit to turn on SCR & Mention its drawback.

4)    Briefly explain the construction & operation of SCR.

5)    Sketch V-I characteristics of an SCR and explain latching current,holding current and Break over voltage.

6)    With waveform explain the dynamic characteristics of SCR.

7)    With circuit diagram & output waveform explain UJT firing circuit used to turn on SCR & mention its advantages over firing circuit.

8)    Define dv/dt & di/dt Explain how SCR is protected against dv/dt & di/dt.

9)    With the help of circuit diagram and output waveform explain about RC firing circuit.

10) With figure explain gate characteristics of SCR.

UNIT-6

1)         With The Help Of Circuit Diagram Explain The Operation Of Single Phase Ac Regulator Using On-Off Control.

2)         Derive The Expression For Rms Value Of Load Voltage Of Single Phase Ac Regulator Using Phase Control.

3)         Explain The Single Phase Bidirectional Ac voltage controller with resistive load with waveform.

4)         With necessary waveforms, explain the operation of a Single Phase full wave controller with inductive load. Derive the expression for rms output voltage.

5)    Numerical problems AC-voltage controllers.

UNIT-7

1)    With neat circuit diagram and waveform explain the working principle of step up chopper.Derive the expression for average output voltage of step up chopper.

2)    With the help of circuit and quadrant diagram,explain the working of a class-E chopper.Mention the devices conducting in each quadrants.

3)    With neat circuit diagram and waveform explain the principle of chopper circuit and derive the expression for duty cycle K.

4)    With neat circuit diagram and waveform explain the operation of step down chopper with RL load(for continuous load current).

5)    Mention the various classification of choppers made on the basis of quadrant of operation.With circuit diagram and quadrant diagram explain

i)                   Class-B chopper

ii)                Class-C chopper

6)    Briefly explain the control strategies used to vary output voltage in chopper.

7)    Numerical problems on choppers.