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EIE315 ELECTRICAL MACHINES I
LECTURERS: PROF
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MUDATHIR FUNSHO AKOREDE

Senior Lecturer & Ag
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E-mail: akorede@unilorin
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ng; makorede@ieee
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Akorede

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Self Introduction
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Full Name
State of origin
Extra-curricular activities
Educational background
Any suggestions or recommendations for the course?

 Class rep to supply the following details:
Full Names, Matric No, Active E-mail Address, Phone Number

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 Ensure you mark attendance for each class but not for
your friend
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 No side talks while lecture is ongoing
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 Prompt submission of assignments, reports, etc
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General energy balance equation
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Double excited system
(electrical energy, induced voltage and torque equations) DC Machines:
principles of operation construction simple armature windings-lap and
wave
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Commutation
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DC Generators:
methods of excitation (separate series, shunt and compound) conditions
for self excitation of shunt generators
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c
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Characteristics of d
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generators
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C
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C
motors
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C motors
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C motor
starters speed control (varying the armature voltage varying the field
magnetic flux, ward Leonard method) variable and constant losses in D
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machines
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5 %
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 Test2 to cover His Aspect
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References
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J
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Gupta, “Theory and Performance of Electrical Machines”, 14th
Edition, Kataria, New Delhi, 2013
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George G
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Holbert , “Electrical Energy Conversion
and Transport: An Interactive Computer-based Transport”, WileyInterscience, 2005
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and Hamilton 111, E
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, “Electromechanical Energy
Conversion”, Macmillan, New York, 1984
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Chapter 1
ELECTROMECHANICAL ENERGY
CONVERSION

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 An electromechanical energy conversion device converts
electrical energy into mechanical energy or vice versa
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 Though the various energy conversion devices may be
different structurally based on their function, they all
operate on similar principles
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Introduction
Generally, three categories of electromechanical energy
conversion devices are:
 Transducers (for measurement and control)- small motion
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Examples are
microphones, pickups, and loudspeakers
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These devices produce forces mostly for linear motion
drives, such as relays, solenoids (actuators), and
electromagnets
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Examples are motors and generators
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Energy Conversion Process
 The principle of conservation of energy:
• Energy can neither be created nor destroyed
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 Therefore the total energy in a system is constant
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The energy transfer equation is as follows:
 Electrical
  Mechanical   Increase in

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 
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  Energy 
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 energy input    energy
   stored energy in   
 from sources   output
  magnetic field   losses 
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 
 

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 During this time, dWf is the differential change in the magnetic stored
energy in the field, and dWm is the differential change in the energy
converted to mech form
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Energy Conversion Process
 Recall that in a coil of N turns, the induced emf can be calculated by
where λ is the flux linkage of the coil and the minus sign
indicates that the induced current opposes the variation
of the field
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 The energy balance equation (on slide 14) together with Faraday’s law
for induced voltage, form the fundamental basis for analysis of energyconversion devices
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Singly Excited Magnetic
Field Systems

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Magnetic circuit equivalent
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Electric circuit analogy
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Analogy between d
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Electric Circuit
and Magnetic Circuit
 The unit for the flux Φ is (weber) and the magnetic flux density B is
given as:
 The magneto-motive force mmf (F) is the ability of a coil to produce
magnetic flux
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
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Magnetization Curve
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Analogy between d
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Electric Circuit
and Magnetic Circuit
Example
The magnetic circuit shown below has the following dimensions: Ac= 16
cm2, l = 40 cm, lg = 0
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The core is made of a
material with the B-H relationship given in the table below
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0 T
in the core, find:
a) The flux φ and the total flux linkage λ, where λ=N φ
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c) The required current with the presence of an air gap
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Analogy between d
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Electric Circuit
and Magnetic Circuit
Solution

In this example, it is clear that the current
needed to set the same flux in case of
magnetic circuits with air gap compared to
those circuits without air-gap is much higher
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What have you learnt
so far?

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