This document provides an introduction to the Power Electronics-I course. It discusses the following key points: - Power electronics deals with efficient power conversion using different circuit topologies. The course will cover basic theory of power semiconductor devices, AC-DC, DC-DC, and DC-AC conversion circuits. - The learning outcomes are to introduce power semiconductor devices and components, familiarize students with various conversion circuit operations and applications, and provide a basis for further power electronics study. - The course contents will cover power semiconductor devices and characteristics, triggering circuits, single and three-phase controlled converters, and miscellaneous converters. The document outlines classroom and online learning resources.

1. EE-321 N
POWER ELECTRONICS-I
credits:4
Lecture-1
Introduction

2. About this Course
• Power Electronics deals with efficient power
(energy) conversion using different circuit
topologies.
• Very interesting and useful course but also
needs a bit of hardwork
• Also important for competitive exams (GATE,
IES, PSUs)
2

3. Learning Outcomes
• To introduce the basic theory of power
semiconductor devices and passive
components, their practical application in
power electronics.
• To familiarize the operation principle of AC-
DC, DC-DC, DC-AC conversion circuits and their
applications.
• To provide the basis for further study of power
electronics circuits and systems.
3

4. Interdisciplinary Nature of
Power Electronics
4

5. Brief Contents
Unit 1: Power SC Devices
and their Characteristics
Unit 2: Triggering Circuits
Unit 3: 1-ph Phase Controlled Converters
Unit 4: 3-ph Controlled Converters
Unit 5: Misc. Converters
5
Me
Dr. AT

6. Venue of Classes
• Your Classroom (ML-10) obviously!
• Teaching mainly with the help of slides
• You are requested to arrange for the projector
cord in advance from the principal office and
return the same after the lecture.
6

7. Learning Resources
• Books:
1. M. H. Rashid, “Power Electronics:Circuits,
Devices & Applications”, 3/e, Pearson-PH.
2. M. S. Jamil Asghar, “Power Electronics”, PHI.
3. Ned Mohan et. al., “Power Electronics:
Converters, Applications and Design”, 3/e, John
Wiley and Sons.
4. P. S. Bimbhra, “Power Electronics”, Khanna
Publishers.
5. And many more!!!!
7

8. Learning Resources…contd.
• This was more than enough, but still you can
explore more material
• Browse web and search for lecture notes, other
e-books… also inform me if you find some good
material.
• http://www.nptel.iitm.ac.in
• Relevant Journals: IEEE Transactions on Power
Electronics, Industrial Electronics, Energy
Conversion etc.
8

9. Discipline Issues
1. Attendance:
Not necessary but desirable. Remember
that 75% attendance is essential to
appear in the final exam.
9

10. Issues…contd1
2. Coming late
• Try to come on time
• 5-7 minutes max.
• If you come within this limit …good enough
and come quietly without seeking permission
• Once I start the lecture do not even peep into
the classroom!
10

11. Issues…contd2
3. Mobile Phones
• Use of mobile phones is not expected during
the class. However, emergency calls may be
responded to.
• Kindly turn your mobiles to silent mode before
the lecture begins.
• Students found playing with/or using mobiles
unnecessarily are liable to disciplinary action!
11

12. Issues…contd3
4. Leaving/ Bunking Classes
• Bunking is NOT acceptable
• If for some reason(bored/tired) you don’t
wanna study, grab me in the corridor before
entering the classroom.
• But arrange for the compensating lecture also!
12

13. Issues…contd4
5. Home Assignment
• Make a neat & legible assignment
• Original work is recommended…may work out
in groups of 3-4, try to understand what you are
writing
• I like creativity…but avoid too much of it like
decorating with flower patterns
• Give proper references of books, websites
that helped you, at the end (IMPORTANT)
• Submit the assignment in person on/before
due date
• Submission after due date: PLAIN ZERO
13

14. Lets Begin!
14

15. Introduction
• Electrical Power is a fundamental requirement
for residential and industrial applications
• However, the nature of requirements may be
variable for different consumers or application
• The electric utility supplies at a fixed voltage
and frequency and thus can’t meet the above
requirement
15

16. Introduction
• Hence, a power modulator (Power electronic
converter) is needed which will act as an
interface between the utility system and
consumer load.
16
Electric
Utility
PE
Converter
Load
A General Power Electronic System Configuration

17. Historical Review
• Mercury arc rectifiers in 1900.
• Used up to 1950, limited use
• Silicon transistor in 1948 Bell Labs―First
Electronic Revolution
• The first Thyristor (Silicon Controlled Rectifier)
developed by Bell labs in 1956.
• Commercial grade SCR developed by GE in
1958 ―Second Electronic Revolution
17

18. Applications
• Commercial Applications (AC, UPS, elevators)
• Domestic Applications (Lighting & heating ckts,
cooking equipments)
• Telecommunications (Battery chargers)
• Transportation (Traction control of
• electric vehicles)
• Utility Systems (HVDC, SVC, Renewable Energy)
• See Rashid/Mohan for further listing
18

19. Types of PE Converters
• DC to DC (Choppers, Regulators)
• DC to AC (Inverters)
• AC to DC (Rectifier)
• AC to AC (Cycloconverter, Regulator,
Matrix converter)
19

20. Advantages of PE Converters
• High Efficiency (> 90%, sometimes up to 99%)
• Compactness (Small size and weight)
• Ease and speed (faster response)
• Reliability & long life (lesser failure rates)
20

21. Disadvantages of PE Converters
• Requirement of elaborate control and
protection circuitry
• Generation of unwanted harmonics
• Associated electromagnetic interference (EMI)
and electromagnetic compatibility (EMC)
issues
21

22. Ideal Switch
22

23. Real Switch
23

24. Real Switch
24

25. Real Switch
• However, for most analysis purposes switches
are assumed to be ideal.
• Practical behavior is to be considered while
designing an actual power electronic
converter (You will not face this!!)
25

26. Desirable Characteristics of a Switch
Please see yourself in Rashid/Mohan/JA
26

27. Power Diodes
• A pn junction diode is the most basic type of
power semiconductor device
• A diode acts as a switch to perform various
functions, such as switches in rectifiers and
freewheeling in switching regulators.
• Similar to signal diode but have higher v and i
ratings
• Up to 6000 V and 4500 A !
27

28. Device Structure
28
P+
N- epi
N+ substrate
v
i
Anode
Cathode
N = 10 cm
19
19
250
microns
10
microns
breakdown
voltage
dependent
N = 10 cm
-3
-3
D
14
N = 10 cm
-3
D
A

29. Physical Layout
29
Signal Diode
Device Symbol
Power Diode

30. i-v characteristics
30
Forward
Conduction Region
Breakdown Region
IDEALREAL
/
( 1)D TV nV
D sI I e= −Shockley Diode Equation

31. Reverse Recovery Characteristics
31

32. Reverse Recovery Characteristics
• Current in forward-biased junction diode is due
to the net effect of majority and minority carriers.
• Once its forward current is reduced to zero, the
diode continues to conduct due to minority
carriers that remain stored in pn-junction and the
bulk semiconductor material.
• The minority carriers require a certain time to
recombine with opposite charges and to be
neutralized.
• This time is called reverse recovery time of the
diode.
32

33. Contd...
• The reverse recovery time, trr , is measured from the
initial zero crossing of the diode current to 25% of
the peak reverse current.
• Softness Factor (SF) = tb/ta
• For practical purposes, we need to be concerned
with the total recovery time trr and the peak value of
the reverse current IRR.
33
barr ttt +=
dt
di
tI aRR =

34. • The reverse recovery charge QRR is the amount
of charge carriers that flow across the diode in
the reverse direction due to changeover from
forward conduction to reverse blocking
condition.
• Its value is determined from the area enclosed
by the path of the reverse recovery current.
34

35. • Therefore:
• Equating the two IRR equations will yield:
rr
RR
RR
rrRRbRRaRRRR
t
Q
I
tItItIQ
2
2
1
2
1
2
1
=
=+=
dtdi
Q
tt RR
arr
/
2
=
35

36. • If tb is negligible as compared to ta, which is
usually the case, then the above equation will
be reduced to:
• Finally,
0,
/
2
≈= b
RR
rr t
dtdi
Q
t
0,2 ≈= bRRRR t
dt
di
QI
36

37. • It can be concluded that the reverse recovery
time trr and the peak reverse current IRR depend
on QRR and di/dt.
• The peak reverse recovery current, reverse
charge, and the softness factor are all of interest
to the circuit designer.
• These parameters are commonly included in the
specification sheets of diodes.
37