STUPIDSID
1 (a)
What is power electronics? Draw a neat block diagram of generalized power converter system. State the applications of power electronics.
6 M
1 (b)
With neat circuit diagram and waveforms, explain the types of power electronics circuits.
12 M
1 (c)
Compare General-purpose, Fast recovery and Schokky diodes.
2 M
2 (a)
The maximum junction temperature of a transistor is T3=150°C and the ambient temperature is TA=25°C, if the thermal impedances are RJC=0.4°C/W, Res=0.1°C/W, and RSA=0.5°C/W. Calculate (i) the maximum power dissipation and (ii) the case temperature.
4 M
2 (b)
With the help of parasitic model and switching model, explain the switching wavefoms of n-type (enhancement) MOSFET.
10 M
2 (c)
Write a note on isolation of grate and base drives.
6 M
3 (a)
Using a two model of thyristor, show that \[ I_A=\dfrac {\alpha I_{C}+I_{CBOI}+I_{CBO2}}{1-(\alpha_{1}+\alpha_2)} \]
6 M
3 (b)
With neat sketch, explain turn-on characteristics of SCR.
6 M
3 (c)
The input voltage of Fig.Q3(b) is Vs=200V with load resistance of R=5?. The load and stray inductance are negligible and the thyristor is operated at frequency of fs=2 kHz. If the required dv/dt is 100 V/?s and the discharge current is limited to 100A. Determine (i) the value of Rs and Cs (ii) the snubber loss, and (iii) the power rating of the snubber resistor.
dv/dt Protection Circuit
8 M
4 (a)
Discuss the effect of inductance using the 1-? full converter.
8 M
4 (b)
What is phase control? Explain the principle of phase control using 1-? half wave controlled rectifier.
8 M
4 (c)
Compare circulating and non-circulating mode of operation of dual converter.
4 M
5 (a)
A thyristor circuit is shown in fig.Q5(a), if thyristor T1 is switched on at t=0, determine the conduction time of thyristor are L=10 ?H, C=50?F and V3=200 V. The inductor carries an intial current of lm=250A.
Self Commulated Circuit
10 M
5 (b)
What is the principle of complementary commutation? Explain the same with the help of suitable circuit and waveforms.
10 M
6 (a)
What is the principle of on off control? Explain the same with a single phase full-wave controller.
6 M
6 (b)
Draw a neat sketch of 1-? AC voltage controller with RL, load and explain its working .
6 M
6 (c)
A single-phase full wave AC voltage controller has a resistive load R=10? and the input votage is V3=120V (rms), 60Hz. The delay angles of thyristor T1 and T2 are equal ?1 - ?2 - ?/2. Determine (i) the rms output voltage V0 (ii) the input power factor PF
(iii) the average current of thyristor IA and (iv) the rms current of thyristor IR.
(iii) the average current of thyristor IA and (iv) the rms current of thyristor IR.
8 M
7 (a)
With a neat circuit diagram, explain the operation of a step down chopper and also explain constant frequency and variable frequency operation. Derive an expression for output voltage incase step down chopper.
10 M
7 (b)
A step-up chopper with a pulse width of 200?s operating on 200V, dc supply. Calculate the output voltage, if the blocking period of the devices is 50?s.
2 M
7 (c)
With a neat mcircuit diagram and quadrant operation, explain class F. chopper.
8 M
8 (a)
With a neat circuit diagram, of 1-0 half bridge inverter, explain the principle of operation of an inverter.
8 M
8 (b)
Write brief note on current source inverter.
6 M
8 (c)
With the help of circuit diagram and waveforms, explain a variable DC-link inverter.
6 M
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