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SUBJECT CODE NO:- P-265
FACULTY OF ENGINEERING AND TECHNOLOGY
T.E. (EC/ECT/IE/E&C) Examination MAY/JUNE-2016
Power Electronics
(Revised)
[Time:Three Hours]
“Please check whether you have got the right question paper.”
i) Q.No.1 and Q.No.6 are compulsory.
ii) Solve any two questions from each section from remaining i.e. from Q.2 to Q.5 and Q.7 to Q.10.
iii) Assume suitable data, if necessary.
Section A
N.B
Q.1
[Max Marks:80]
Solve any two.
I. Step-up cycloconverter
II.
Gate characteristics of SCR
III.
What is commutation? Why it is necessary in SCR?
IV.
Integral cycle control
10
Q.2
a) With the help of near circuit diagram and waveforms, explain V-1 characteristics of power BJT.
08
b) For an SCR, the gate – cathode characteristic has a Vs=15V, a straight line slope of 130 and allowable 07
gate power dissipation of 0.5 watts, compute the gate – source resistance.
Q.3
a) With the help of a neat circuit diagram and waveforms explain line – synchronized VJT triggering
circuit.
b) The trr= 5
and
. If SF=0.5, Determine
i. QRR
ii. IRR
08
Q.4
a) Explain the effect of source inductance “Ls” on performance of 3- converter?
b) Explain
full converter with R – load with neat circuit diagram and waveforms.
08
07
Q.5
a) Explain class-B commutation technique with neat circuit diagram and waveforms.
b) Explain
A.C. voltage controller with RL load.
08
07
07
Section B
Q.6
Solve any two.
I. Series Inverter
II.
Four quadrant chopper
III.
HF heating
IV.
Ring counter circuit
10
a) With the help of neat circuit diagram and waveforms. Explain working of
1800 conduction
mode of bridge inverter.
b) Calculate o/p frequency of series inverter with L=10mH, c=
, RL=500Ω , Toff = 250
,
tq=25
Q.7
P-2016
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08
07
Q.8
a) Explain voltage commutated chopper with neat circuit diagram and waveforms?
b) The dc chopper has a resistive load of R=10Ω, I/P dc voltage is 220V. When the chopper switch
remains on, it’s ON state voltage drop is 2V. Chopper frequency is 1 KHz. If duty cycle is 50%
Determine,
1) Average O/P load voltage
2) RMS O/P Load voltage
3) Effective I/P resistance
08
07
Q.9
a) Explain time delay circuit with neat waveforms and circuit diagram.
b) Explain flasher circuit with neat waveforms.
08
07
Q.10
a) With the help of neat circuit diagram derive the expression for IL(MAX) and IL(MIN) of class – A chopper. 08
b) Explain various voltage control techniques of an Inverter.
07
P-2016
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