Power Electronics 2 (H5CPE2)

1
Power Electronics 2 (H5CPE2)

• Dr Christian Klumpner
• Power Electronics, Machines and Control Group
• School of Electrical and Electronic Engineering,
  UoN
• Tower Building, 508
• email christian.klumpner_at_nottingham.ac.uk
• Module webpage www.eee.nott.ac.uk/teaching/h5cpe2

2
Introduction

• Typical AC/DC/AC power conversion (Adjustable
  Speed Drive)
• AC/DC converter (Rectifier) fixed
  voltagefrequency to DC voltage
• DC/AC converter (Inverter) DC voltage to
  variable voltage/variable frequency
• Why AC/DC/AC? Electrolytic capacitors (compact
  and cheap), only unipolar devices available
  (transistors)
• Operation of rectifier, stress on devices (),
  design of filter (), operation of inverter

3
Introduction
Pre requisites  Circuit theory and electronics at
first year undergraduate level, knowledge of
switching regulators and single phase
rectification (controlled and uncontrolled) such
as that provided by module H5BPE1.  Aims and
objectives of the module The aim of this module
is to provide an in depth knowledge of power
electronics at a level suitable for final year
undergraduate students. Since power electronics
is a rapidly growing subject the course tries to
reflect this by covering the well established and
widely used technologies (such as three phase
rectification) as well as more recent
developments such as resonant converters. The
increasing importance of power quality is also
addressed and various high power factor utility
interface circuits are discussed. Inverter
circuits employing pulse width modulation (PWM)
are studied due to their very widespread use in
variable speed drives and power supply systems.
High power (multi-level) converter structures are
then discussed. Throughout the course, emphasis
is placed on circuits and their applications
rather than on the technology of power switching
devices.
4
Lecture course syllabus
5
Recommendations
 Booklist  There are no essential books for this
course. However, the following book is excellent
and covers most of the material in this course
and the second year power electronics
course.   POWER ELECTRONICS Converters,
Applications and Design (2-ed) by Mohan, Undeland
and Robbins, Wiley publishing   Another book
worth looking at for power electronics in
general, rather than specifically this course
is  ELEMENTS OF POWER ELECTRONICS, by Philip T
Krein, Oxford University Press

• familiarize yourself with emergency exits (fire
  alarm) in the building
• dont get late (not more than 5 minutes) into
  the classroom
• switch off mobile phones
• attend to the course equipped with a ruler, 4 or
  more colored pens/markers
• if you have a computer at home, install a
  simulation pack (PSPICE, Simcad)

6
Review of 3-phase supplies (1)
Why sinusoidal voltage?
Behavior of passive components
Inductor
Capacitor
Resistor
Integrative
Derivative
Proportional
Rectangular Voltage
Triangular Current
Rectangular Current
Pulse Current
Production, transport distribution system
Resistors Inductors Capacitors We need to
preserve the voltage waveform
7
Review of 3-phase supplies (2)
We need a supply voltage waveform which preserves
its shape when is derivated or integrated ?
sinusoidal
Inductor
Capacitor
Resistor
Behavior of passive components
Integrative
Derivative
Proportional
Sinusoidal Voltage
Sinusoidal Current
Sinusoidal Current
Sinusoidal Current
8
Review of 3-phase supplies (3)
Assume a STAR connected supply
In practice, the 3 voltage sources represent the
voltages generated by 3 coils (physically
displaced by 120O from each other) in an AC
rotating machine (Alternator)
Phasor diagram
Line to line voltage often called line
voltage
9
Review of 3-phase supplies (4)
Assuming the peak phase voltage is E (a
convention used throughout the course) then
B lags A by 120O, C lags B by 120O etc
This is for phase sequence A-B-C, A-C-B is also
possible we will always assume A-B-C
Drawing a phasor diagram and converting back to
time functions, it is easy to show that the line
voltages are given by
3-phase supplies are specified using the RMS line
voltage. Hence a 415V, 50Hz, 3-phase system
means
10
Review of 3-phase supplies (5)
Why three-phase voltage systems (120O displaced)?
Displacement angle 0O
Displacement angle 90O
Necessity to deliver - smooth power (require less
filtering) -
smooth torque in a motor (less mechanical stress,
noise)
11
(No Transcript)