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INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1 (a) Give symbol and characteristics features of the following devices:
(i) SCR
(ii) GTO
(iii) TRIAC
(iv) IGBT
(v) SIT
10 M
1 (b) Briefly explain any five types of power electronic circuits.
10 M

2 (a) What is the need for isolation of gate-drive circuits? Discuss the different methods of providing isolation of gate-drive circuits from power circuit.
10 M
2 (b) Discuss the switching limits of power transistors.
10 M

3 (a) With a neat diagram, explain the two-transistor model of a thyristor. Also derive an expression for the anode current in terms of transistor parameters ?1 and ?2.
8 M
3 (b) what is the need of dv/dt and dv/dt protect on? Explain in how protection is provided.
4 M
3 (c) With a neat circuit diagram and waveforms, explain UJT relaxation oscillator.
8 M

4 (a) With the necessary circuit diagram waveforms and equations, explain the operation of single-phase full converter with R-L load.
10 M
4 (b) Explain single-phase semiconverter with a neat circuit diagram, waveforms and equations.
10 M

5 (a) What is commutation? Explain complementary communication with relevant circuit diagram and waveforms.
10 M
5 (b) For the auxiliary commutation circuit. Calculate the value of the commutation capcitor and inductor for the following data:
Vdc=30V, IL(max)=15A , Ioff of SCRI=20?sec.
4 M
5 (c) With a neat circuit diagram and waveforms, explain the external pulse commutation.
6 M

6 (a) With neat diagrams, waveforms of equations, discuss ON-OFF control and phase control of AC voltage controllers.
12 M
6 (b) A single-phase full-wave AC voltage controller has a resistive load 20? and the input voltage is 100 V (rms), 60 Hz. The delay angles of thyristors T1 and T2 are : ?2=?2=?=?/2,
Determine : (i) The rms outpur voltage : (ii) The input power factor : (iii) The average current of thyristors
(iv) The rms current of thyristors.
8 M

7 (a) What is chopper? How they are classified? Briefly explain
10 M
7 (b) With a neat circuit diagram and waveform explain impulse commulated chopper.
10 M

8 (a) Explain single-phase half -bridge inverter with R load, with necessary circuit diagram and waveforms. Derive the equation for rms output voltage.
12 M
8 (b) Explain the performance of inverters.
8 M

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