Download AKTU B-Tech 5th Sem 2016-2017 Power Electronics Nee 502 Question Paper

Download AKTU (Dr. A.P.J. Abdul Kalam Technical University (AKTU), formerly Uttar Pradesh Technical University (UPTU) B-Tech 5th Semester (Fifth Semester) 2016-2017 Power Electronics Nee 502 Question Paper

Printed Pages: 3 NEE-502
(Following Paper ID and Roll No. to be ?lled in your
Answer Books)
Paper ll) : 20l2375 Roll No.
B.TECH
Regular Theory Examination (Odd Sem-V), 2016-17
POWER ELECTRONICS
Time : 3 Hours Max. Marks : 100
Section - A
1. Attempt all parts of the following. (10X2=20)
3)
b)
C)
d)
e)
f)
g)
h)
What is the basic difference between ?freewhealing?
and ?feedback diodes??
State the advantages of power converters.
De?ne SCR ratings.
Why is the reverse breakdown voltage greater than
forward breakdown voltage in SCR?
De?ne ?latching current? and explain how is it
different from ?holding current?.
What is the difference between primary and
secondary breakdown in a power transistor?
What is meant by quasi saturation?
Explain the need for protection of power devices.
502/12/2016/5600 (1) [P.T.O.

NEE-502
i) De?ne string ef?ciency and state its signi?cance
in case of series and parallel connection of power
devices.
j) State and explain the conditions for successful
commutations.
Section - B
Not'e : Attempt any ?ve questions from this section
(5x10=50)
What are the characteristics of an ideal power switching
device? Compare and contrast the characteristics of
IGBT and MOSFET.
Explain two transistor analogy applied to a thyristor with
the help of neat and clean illustrations.
On what factors does the di/dt rating of a thyristor
depend? What device techniques are used to improve the
di/dt rating? ?
Describe with neat diagram the working of a depletion
type p-channel MOSFET. Also draw its transfer
characteristics.
A single phase 230 V, 1 kW heater is connected across a
230 V, 50 Hz supply through a thyristor. Determine the
power absorbed by the heater for the ?ring angle of 45?.
Explain the dynamic equalizing circuit for series
connected SCRs.
Explain the need of commutation in thyristor circuits.
What are the different methods of commutation? Explain
any one of them with the help of neat and clean schematic
and waveforms.
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Note :
10.
ll.
12.
NEE-502
What is dc chopper? Describe the various types of
chopper configurations with appropriate circuit
diagrams.
Section - C
Attempt any two questions from this section.
(2X 15:30)
What is the need for controlling the voltage at the output
terminal of an inverter? Describe brie?y and compare
the various methods employed for the control of output
voltage of an inverter.
What are dual converters? Explain the Operation of three-
phase dual converter using circulating current mode of
operation. How are ?ring angles of two converters
controlled?
Explain the operation of Single?phase fully controlled
bridge converter feeding a highly inductive load and draw
relevant output voltage and current waveforms.
++++
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