Download AKTU (Dr. A.P.J. Abdul Kalam Technical University (AKTU), formerly Uttar Pradesh Technical University (UPTU) B-Tech 6th Semester (Sixth Semester) 2014-2015 Power Electronics Question Paper
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(Following Ppper ID and Roll No. m be filled in your Answer Book)
PAPER ID : 121603- ?
Roll No.
B. Tech.
(SEM VI) THEORY EXAMINATION, 2014- 15
POWER ELECTRONICS
Tune : 3 Hours] [Total Marks : 100
Note: (1) .- Attempt all questions.
(2) All questions carry equal marks.
'1 Attempt any four parts: 5><4=20
(a) What are th? characteristics of an ideal power
switching device?
(b) Explain the switching characteristics of a BIT.
(c) Find the number of thyristors each With a rating of
500V and 75A required?for each branch of a series
parallel combination for a circuit for a total voltage
and current rating of 7 .SKV and 1 KA. Assume
. derating factor of 14%.
(d) EXplain the signi?cance of latching and holding
currents.
(e) EXplain the steady state and switching
characteristics of MOSFET.
(f) Explain working of Triac.
121603] 1 [ Contd...
2. Attempt any two parts E 10><2=20
' (a)
(b)
(C)
(a)
(b)
(C)
121603]
What is a DC chopper? Describe the various
types of chopper con?guration with neat and
appropriate diagrams.
Discuss the two transistor model of a thyristor.
Using this model, describe the various
mechanisms of taming on a thyristor.
Explain the resonant pulse commutation with the
help of circuit diagram and waveforms. Explain
the effect of accelerating diode.
Attempt ant two parts:- ' v lOXZ=20
A single phase half controlled bridge operated from
the 230 V, 50 HZ mains feeds a resistive load of
1009. If the ?ring angle is 600, Calculate,
(i) Average output voltage
(11') rms output voltage
(Iii) total output power
(iv) DC output power
(v) load current at instant of turn on
What do you understand by dual converters? -
Explain the Operation of a 345 dual converter
using circulating current mode of operation. How
are ?ring angles of two converters controlled?
Discuss the working of 1? full wave ae-dc converter
taking into account the effect of source inductance.
Draw the output voltage waveform for ?ring angle
of 300.
2 [ Contd...
Attempt ant two parts:- 10><2=20
(a) Describe the basic principle of working of l? to
la) step down cycloconverter for both continuous
and discontinuous conductions. Make the
conduction of various thyristor also.
(b) Describe 1? ac voltage controller with inductive
and resistive loads. Describe an expression for
output voltage.
(c) Show that the fundamental rms value of per
phase output voltage of low frequency for an m
pulse cycloconverter is given by:
Vov=Vphrmt simcm.
Attempt ant two parts:- 10><2=20
(a) Discuss the working principle of a 145 series
inverter. What are the advantages and
disadvantages of series inverter.
(b) Explain operation of a '3 4) bridge inverter
employing 1200 mode of operation. Draw
waveforms of phase voltages and any one line
voltage assuming star connected resistance load.
(c) The single phase quasi-square wave bridge
inverter operators from a DC supply of 200v at?
a frequency of 100 Hz and feeds a resistive
load of 109 calculate:
(i) Duration of the ON period if the rms value
of the load voltage is 100v.
(1i) Peak supply current
Gin) Average DC supply current.
121503] . 3 [ 8675 1
This post was last modified on 29 January 2020