Transcript Theory of Electrical Machines, drives and Control - CFD

Dr. B. Umamaheswari
Professor
Dept of Electrical & Electronics Engineering,
College of Engineering Guindy
Anna University Chennai
Programs linked in the enclosed slides can be run in MATLABSIMULINK platform
The Teaching and Learning Process
An Effective Teaching-Learning Process may require the
following 5-step sequence
OPTRA
O Organising
P Preparation
T Transmission
R Reception
A Assimilation
Let us present this lecture in these 5-steps
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Organizing
The theory of electrical machines is best explained with
analytical models and equivalent circuits. Hence
with the help of software tools these concepts can be
best explained.
Let us start with the following questions
 Why do we need tools like MATLAB?
 How, where and when do we these tools?
 To what level do we use these tools?
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Use of software tools
like
MATLAB & SIMULINK
 Best used when the theory requires support of
analytical expressions i.e. in the form of mathematical
equations
 The equations could be
 static or dynamic
 Linear or non-linear
 Descriptive or symbolic
 Deterministic or stochastic
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Benefits of using software tools
 To have better understanding of the operating
principles
 To visualise the characteristics under various
operating conditions
 To experiment on favourable and non-favourable
conditions
 To design and test the machines for achieving
improved performance
 To create a working platform for pre-determining the
characteristics
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Level of Usage
 Digital simulation for complete functional testing MATLAB/SIMULINK
 Hardware in Loop (HIL) simulation for real time
testing of the controller –RTW and DAQ
 Power Hardware in Loop Simulation (PHIL) for real
time testing of the Power Electronics and Controller RTW and DAQ
 Embedding the control algorithm on a real time
embedded target platform – RT Target link module
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Suitability of the tool for Electrical
Drives and Control
 Fields involved
 Electrical Machines
 Power Electronics
 Control Theory and
 embedded platforms
 Study involves understanding of analytical
expressions .
 Simulation of experimental conditions and research
developments is possible.
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Topics for Presentation
Let us discuss the
following topics using
software tools
1. Electro-Magnetics
2. Electro-mechanics
3. DC Machines
4. AC Machines
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1. Electro-Magnetics
Under Electro-magnetics the following topics are to be
discussed.
 Magnetic circuit – the linear relationship
 Electrical Equivalent
 Inductance
 Rotating magnetic field
 Use software tools for teaching and research
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Magnetic circuit
 H .dl  Ni
 The Amphere’s Law
A current carrying coil
produces magnetic field
whose intensity is decided
by the permeability of the
medium through which
the flux passes through.
 BH-curve describes the
permeability of a medium
 For linear assumption
Permeability is constant
0  4 x107
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r  1000
R  g /  *a
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Electrical equivalent
For the purpose of analysis,
an equivalent electrical
circuit can be drawn.
 Flux => current
 MMF => emf
 Reluctance => Resistance
 Linear BH- relationship Program1
 Non-linear BH relationship
program2
  Ni ( Ri  Rg )
Ni  Bg
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lg
0
 H i ( Bg )li
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Linear case
 Linear BH- relationship
 Air gap reluctance is Rg
 Core Reluctance is Rl << Rg
 Using voltage division rule, the greater Reluctance
part gets the greater MMF sahre
 Hence upon the supplied MMF ‘Ni” most of the
MMF is dropped or available across the air-gap
 Program1 describes the flux variation (equation 1)
as a function of airgap length.
 Program1
  Ni ( Ri  Rg )..(1)
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Non-Linear case
 Non-linear BH relationship
 Core reluctance is a function of flux
 Use equation (3) to get Hl for various values of Bg.
 Superimpose the obtained Hl vs Bg characteristics on
the BH curve to get Hl and Bg of the given circuit.
 Use Program2 to see the results.
program2
  Ni ( Ri ( )  Rg )..(2)
Ni  Bg
lg
0
 H i ( Bg )li ....(3)
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Inductance
 Self Inductance of a coil
describes how much of the flux
links the coil produced by its
own current
 Mutual inductance of a coil
describes how much of the flux
links the coil produced by
current in the other coils.
 Inductance in a salient pole
machine is simulated using the
following program
 MATLAB Program
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N a
L
l ( )
2
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Generation of Sinusoidal MMF
 With two sets of coils of carrying currents in the
opposite directions Square -MMF waveshape can
be produced.
 Using appropriate Fourier relationship the square
wave can be resolved into fundamental and its
harmonic components .

Fa1 x, t   Fa1m  sin x  sin 1t

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Rotating magnetic field
 Rotating magnetic field can
be produced by Two, Three
or more phases equally
placed along the periphery
of a circular path
 Rotating MMF of Two
phase and Two pole
machine is illustrated in the
following program
 MATLAB Program
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Electro-mechanics
 A coil (Armature) placed in the airgap subjected to
time-varying magnetic field experiences an induced
voltage { Faraday’s Law}
 It circulates current to oppose its cause (Lenz aw)
 Interaction of magnetic flux with armature current
produces mechanical force
 Direction of force is given by Fleming’s Left Hand
Rule.
 This is the principle of motoring
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Principle of
Motoring & Generation
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Simulation of DC Machine
characteristics
 Equivalent circuit of DC machine with separate
excitation is illustrated in the figure
 Using software simulation the characteristics can be
studied
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MATLAB
CODING
I. DC MOTOR
II. EQUIVALENT CIRCUIT
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Separately excited
 Torque speed characteristics
 Matlab model
 Matlab code
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Other EXCITATION SCHEMES
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Load Profiles
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Series excited
 Torque speed characteristics
 Matlab model
 Matlab code
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Simulation DC-Chopper
performance
 Program_Chopper
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Chopper fed DC Drive
 MATLAB program
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Closed loop PI Control of Chopper
fed DC motor  Matlab model
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Induction
Machine
 Steady state Equivalent circuit
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Three Phase Induction machine
 Circle diagram can be obtained using the following
program to predetermine the steady stae
characteristics
 Circle diagram
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3ф INDUCTION MOTOR
 Torque speed
characteristics can
be obtained using
the following
program
 MATLAB CODE
 MATLAB MODEL
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SINGLE PHASE IM
 Closed Loop Speed control
 V/F control
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References
 Electric Drives by Ion Boldea and S.A. Nasar
 Electrical Machines by Nagrath and Kothari
 Electrical Machines by Fitzerald and Kingsley
 Power Electronics by B. K. Bose
 Control Systems Engineering by I. J. Nagrath and M.
Gopal
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B. Umamaheswari
Professor
Department of Electrical and Electronics Engineering
Anna University Chennai
[email protected]
This lecture material serves as s a supplement for learning
electrical machines , drives and control for an advanced learner
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