ABSTRACT
The desirability for new induction machines that possess the combined advantages of the well-established wound-rotor and squirrel-cage induction machines have motivated considerable research interests in the development of dual-stator induction machines. Although extensive literature survey has revealed considerable advancements in the design architecture of dual-stator winding induction machine, it is yet to attain maturity from the standpoints of optimized active material utilization, efficiency and harmonic attenuation. In pursuit of some of these critical issues, this research is primarily aimed at developing a pragmatic approach of re-designing a standard three phase induction machine into an improved dual-stator winding induction machine (DSWIM) and of its practical implementation. More specifically, a methodology which encompasses realizing a dual stator winding machine prototype based on hybrid analytical and genetic algorithm (GA) optimization as well as establishing the machine performance characteristic indices, and its experimental validations. A paramount consideration is the comprehensive characterization of such improved dual-stator winding induction machine. The adoption of DSWIM housing similar pole ratios, as opposed to dissimilar pole ratios widely studied in the literature, is to permit full winding utilization and maximization of its output power capability. In this dissertation detailed mathematical modelling, based on Park‘s equations in d-q-0 arbitrary reference frame, to underpin simulation of the dual stator winding in MATLAB environment and application of finite element technique to stator field distribution mapping to enable computation of machine inductances have been developed and successfully implemented. All the leading DSWIM design parameters based on the classical design and GA optimization technique are presented and comprehensively discussed. The proposed theoretical computations of dual stator winding inductances are shown to be superior to the existing technique based winding function approach. As a major goal accomplished, a prototype implementation of the DSWIM equipped with 8/8 similar pole ratio has been satisfactorily realized in the laboratory as a demonstration of the practicability of the proposed design concept. This has enabled an elaborate experimental setup which facilitated accurate measurements of fundamental parameters of the proposed dual stator winding induction machine as well as in-depth operational performance evaluations comprising its steady state and dynamic drive capabilities. Of noteworthy is the GA optimization with respect to the similar pole ratio DSWIM stator winding re-design that revealed its optimum efficiency and power factor (p.f) values respectively to be 93.43% compared with 87% and 88.02% compared with 80% for standard 3-𝛟 induction machine of the same rating. The significance of the improvement in DSWIM efficiency and power factor achieved is central to the actualization of the prime goal of this research work and capable of driving future research directions. The DSWIM housing similar pole ratios has, to the best of our knowledge, remained largely unexplored. The importanceof the proposed DSWIM design consideration has also envisaged its potential application to exploiting maximum power harvest from wind turbines operating in low wind regimes prevalent in the tropical region.
TABLE OF CONTENTS
COVER PAGE i
TITLE PAGE ii
DECLARATION iii
CERTIFICATION iv
DEDICATION v
ACKNOWLEDGEMENT vi
TABLE OF CONTENTS viii
LIST OF FIGURES xvii
LIST OF PLATES xxi
LIST OF TABLES xxii
ABBREVIATION AND DEFINITION xxiii
LIST OF SYMBOLS xxiv
ABSTRACT xxv
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CHAPTER ONE: INTRODUCTION
1.1 Background Information 1
1.2 Motivation 3
1.3 Problem Definition 4
1.4 Aim and Objectives 6
1.5 Overview of Research Methodology 7
1.6 Significance of the Research 10
1.7 Dissertation Organization 11
CHAPTER TWO: THEORETICAL BACKGROUND AND LITERATURE REVIEW
2.1 Introduction 13
2.2 Review of Fundamental Concept 13
2.2.1 Characterizations of physical features and operating modes of IM 14
2.2.2 Development of induction machine speed-torque characteristics 17
2.2.3 Motoring and braking operating regimes 19
2.2.4 Generating mode of operation of induction motor 22
2.2.5 Dual stator winding induction machine theoretical concept 23
2.2.6 Derivation of DSWIM equivalent circuit parameters and torque equation 24
2.2.6.1 Voltage equations in machine variables 25
2.2.7 Derivation of winding inductances 29
2.2.7.1 Generalized flux equation based on winding function theory 29
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2.2.8 Derivation of self-inductances 34
2.2.9 Derivation of mutual inductances 35
2.2.10 Derivation of stator leakage inductance for three special cases 37
2.2.11 Derivation of mutual leakage inductance 42
2.2.12 Transformation of machine variable equations into arbitrary d-q-0 reference frame45
2.2.13 Turns Ratio Scaling Procedure 48
2.2.14 Development of torque equation for DSWIM 50
2.2.15 Overview of multi-phase induction machine design concepts 52
2.2.16 Design optimization of multi-phase induction machine 56
2.2.17 Overview of genetic algorithm 57
2.2.18 Selection of method of field analysis for induction machines 61
2.2.18.1 Finite element method (FEM) 63
2.3 Review of Similar Works 63
2.3.1 Review of historical development of DSWIM 63
2.3.2 Review of recent publications on DSWIM design, modelling and
control techniques 68
2.3.4 Research thrusts pursued in this dissertation 76
2.4 Summary 76
CHAPTER THREE: DSWIM DESIGN METHODOLOGY
3.1 Introduction 78
3.2 Generalized Description of a Dual Stator Winding Induction Machine Design Procedure 79
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3.3 Magnetic Loading Characterization 83
3.3.1 Mathematical description of air-gap flux density for DSWIM 84
3.4 Computation of Total MMF in a Magnetic Circuit of Asynchronous Machine 87
3.4.1 MMF estimation for air gap considering slots on the rotor and stator surfaces88
3.4.2 Derivation of MMF of stator tooth and rotor tooth 92
3.4.3 Derivation of MMF of the stator core 94
3.4.4 Derivation of MMF for rotor core 95
3.4.5 Determination of number of stator turns per phase 97
3.4.6 Computation of magnetising current and inductance per phase 99
3.4.7 Surface current density estimation 99
3. 4.8 Calculation of stator conductor diameter 101
3.4.9 Stator conductor current density calculation 101
3.4.10 Stator winding categorization 101
3.4.11 Outline of stator winding Architecture 103
3.4.12 Quantitative description of winding arrangement in slots 103
3.4.13Winding dimension calculation 104
3.5 Analytical Calculations of DSWIM Steady State Equivalent Circuit
Parameters 105
3.5.1 Stator resistance calculation 106
3.5.2 Stator leakage Inductance (Reactance) 109
3.5.2.1 Slot leakage inductance 110
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3.5.2.2 End winding leakage inductance 111
3.5.2.3 Belt leakage inductance 112
3.5.2.4 Zig-zag leakage inductance 113
3.5.2.5 Skew leakage inductance 114
3.5.2.6 Total stator leakage inductance 114
3.5.3 Determination of rotor parameters 114
3.5.3.1 Rotor parameters referred to stator side 116
3.6 DSWIM Design Framework 117
3.6.1 Functional description of DSWIM design procedure 118
3.7 GA Based Optimization of DSWIM 122
3.8.1 GA solution methodology 123
3.9 Design Calculations for Similar Pole DSWIM 126
3.9.1 Specification of magnetic loading for 8/8 pole DSWIM 126
3.9.2 Calculations of total MMFs in 8/8 pole DSWIM 128
3.9.3 Power, surface current density, number of turns per phase and conductor sizing
3.9.4 Calculations of inductances and resistances for 8/8 DSWIM 129
3.10 Winding Layout Design for 8/8 DSWIM 130
3.10.1 Stator winding dimension calculation 131
3.10.2 Stator ‗a-b-c‘ winding diagram 131
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3.10.3 Stator ‗x-y-z‘ winding diagram 132
3.10.4 Complete stator winding diagram for 8/8 pole DSWIM 133
3.11 Summary 134
CHAPTER FOUR: DSWIM MATHEMATICAL MODELING AND FINITE ELEMENT ANALYSIS
4.1 Introduction 135
4.2 Development of DSWIM Equations in d-q-0 Arbitrary Reference Frame 135
4.2.1 Functional representation of DSWIM mathematical model 139
4.2.2 Description of DSWIM Simulink model 142
4.3 Finite Element Method 146
4.3.1 Description of finite element method magnetics (FEMM) software 147
4.3.1.1 Femme.exe program 147
4.3.1.2 Simulation.exe program 148
4.3.1.3 Femmview.exe program 148
4.4 DWIM Based FEMM Analysis 149
4.4.1 Categorization of DSWIM inductances 150
4.4.2 Procedures for calculating self-inductances 153
4.4.2.1 Stator winding inductance calculation procedure 153
4.4.2.1 Rotor Equivalent winding inductance calculation procedure 154
4.4.3 Procedures for calculating mutual inductances 156
4.4.3.1 Mutual inductances due to stator phases of the same winding procedure 156
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4.4.3.2 Mutual inductances due to stator phases of different winding sets procedure 156
4.4.3.3 Mutual inductances between rotor phases procedure 157
4.4.3.4 Mutual inductances between stator and rotor phases procedure 157
4.5 Determination of DSWIM Equivalent Circuit Parameters Using FEMM 158
4.5.1 No-load test FEMM simulation procedure for magnetizing
inductance calculation 158
4.5.2 FEMM model based locked-rotor test procedure 159
4.5.2.1 Excitation of only stator ‗a-b-c‘ winding set in FEMM model of DSWIM 159
4.5.2.2 Excitation of both stator winding sets (with 300shift) 161
4.5.2.3 Excitation of both stator winding sets (with 00shift) 161
4.6 Determination of Equivalent Resistance and Inductance for DSWIM 162
4.7 Summary 165
CHAPTER FIVE: RESULTS AND DISCUSSIONS
5.1 Introduction 167
5.2 DSWIM Design Consideration Results 167
5.2.1 Results of DSWIM improved classical design (ICD) approach 168
5.2.2 Results of GA optimization of DSWIM power factor and efficiency 171
5.2.3 Results of DSWIM parameter calculations based on winding function
approach 175
5.2.4 Results of FEMM model of DSWIM for parameter estimations 176
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5.2.4.1 Results of self- inductances stator windings 176
5.2.4.2 Results of self- inductances of rotor windings 176
5.2.4.3 Results of mutual inductances of intra-stator windings 177
5.2.4.4 Results of mutual inductances of inter-stator windings 177
5.2.4.5 Results of mutual inductances of rotor windings 178
5.2.4.6 Results of mutual inductances between stator and rotor windings 178
5.2.4.7 Results of equivalent Circuit Parameter Determinations from FEMM Model 179
5.2.4.8 Analysis of FEMM simulation results 180
5.2.5 Comparison of DSWIM Inductance Values Computed Via Three Methods 184
5.3 Results of DSWIM Simulation in MATLAB/Simulink Software 186
5.3.1 Results of Starting process and fixed loading dynamic response of DSWIM 187
5.3.2 Investigation of effects of mutual leakage inductance on the
characteristics of similar pole DSWIM 191
5.3.2.1 Case study I 191
5.3.2.2 Case study II 191
5.3.2.3 Case study III 192
5.3 Discussion of Simulink Model Results 201
5.4 Prototype Realization of DSWIM and Experimental Results 203
5.4.1 Prototype realization of DSWIM 203
5.4.2 Experimental results 206
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5.4.3 Determination of the induction machine parameters 208
5.4.3.1 DC resistance test 208
5.4.3.2 Locked- rotor test 209
5.4.3.3 No- load test 211
5.4.4 Comparison of DSWIM simulation and prototype experimental results 215
5.4.5 Comparison of results for DSWIM and standard 3-𝜙 IM 216
5.4.6 DSWIM circle diagram results 220
5.4.7 DSWIM loss segregation results 221
5.5 Analyses of Experimental Results 222
5.5.1 Rotor starting torque characterization 224
5.5.2 Acceleration of DSWIM from standstill 224
5.5.3 Behavior of DSWIM near synchronous speed 225
5.5.4 DSWIM behavior during loading and breakdown 225
5.6 Summary 226
CHAPTER SIX:SUMMARY, CONCLUSIONS AND RECOMMENDATIONS 227
6.1 Introduction 228
6.2 Summary 228
6.3 Conclusion 230
6.4 Contributions to Knowledge 232
6.5 Recommendations 234
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6.6 Suggestions for further work 235
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CHAPTER ONE
INTRODUCTION
1.1 Background Information
As a critical operational requirement, all modern electric utilities that supply electrical appliances, industrial equipment and drives must operate at constant frequency of choice; and it is either 50 Hz or 60 Hz (chapman, 1998). It is also well known that for any electric utility, different varieties of ac machines which are the workhorses of all motorized loads constitute dominant entities within industrial, commercial and residential load compositions. From the fundamental operating principles of an alternating current (ac) machine, its speed is proportional to the frequency of input voltage and current. Consequently, all ac machines have fixed speeds when supplied from power utilities. However their speeds can be made variable to meet the needs of most industrial processes. For example, a number of modern manufacturing processes, such as machine tools, require variable speed. The expanding applications of variable speed ac motors have remained the driving force for wide range of research activities aimed at improving their operational capabilities and efficiencies. A comprehensive overview of ac machine family is illustrated in Figure 1.1.
As a matter of fact, the introduction of variable-speed drives has increased automation and productivity and, in the process, efficiency. In developed countries typified by USA, nearly 65 % of the total electric energy produced is consumed by electric motors (Krishan, 2001). Variable speed drives in the industry employ electric motors as their drive motors mainly because they enjoy several specific advantages, such as overload capacity, smooth speed control over a wide range, capability of operation in all the four quadrants of the speed-torque plane, etc.
From historical perspectives until the advent of thyristors and power converters, dc motor varieties had been very popular in the area of adjustable speed drives, even though it suffered
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from the disadvantages imposed by the presence of a mechanical commutator. Power converters capable of providing variable voltage, variable frequency supplies have now made ac motors increasingly popular. Among the ac motors used in the industry, induction motor is the most dominant because of its ruggedness as well as much cheaper maintenance and control requirements. Squirrel cage and wound rotor induction motors are most common induction motors found in small to large industrial complexes. The literature is therefore replete with design concepts on the induction machines of different configurations and the emerging design concepts on, and operational characterization of, multi-phase induction machines. The magnetic design, practical realization and characterization of multi-phase induction machine, in which the stator is equipped with two sets of windings of identical number of poles and standard squirrel cage rotor, constitute the core research areas addressed herein. Of prime research interest is the optimum reductions in DSWIM losses so as to maximize efficiency and also improve p.f.
Figure 1.1: Generalized AC Machine Family (Adapted from: Lessons in AC Circuits Vol. II-AC7)
VARIABLE RELUCTANCE AC MAHINES ASYNCHRONOUS MACHINES SYNCHRONOUS MACHINES THREE PHASE SINGLE PHASE AC BRUSHED UNIVERSAL POLYPHASE ( > 3 WINDINGS) OR (DUAL STATOR WINDING SQUIRREL CAGE WOUND ROTOR SYNCHROS & PERMANENT SPLIT CAPACITOR CAPACITOR SPLIT SHADED VARIABLE RELUCTANCE STATOR WOUND WITH DISSIMILAR POLES & SQUIRREL STATOR WOUND WITH SIMILAR POLES SINE WAVE STEPPER BRUSHLESS RELUCTANCE WOUND ROTOR SYNCHRONOUS CONDENSER PERMANENT MAGNET ROTOR PERMANENT MAGNET (PM) HYBRID SYNCHRONOUS RELUCTANCE SWITCHED RELUCTANCE
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1.2 Research Justification
The conventional three phase induction motors have dominated the industrial undertaking as the workhorses of mechanized/automated processes and will continue to remain so into the foreseeable future. However with the demand for high power electric drive systems characterized by ruggedness, high energy-efficiency and reliability gave impetus to multi-phase induction machine development. Specialized applications, such as electric/hybrid vehicles, marine propulsion, aerospace applications, etc. that demand high reliability, are majorly responsible for the aforementioned demand for multi-phase induction motors. Within the last two decades therefore, multi-phase induction machines (machines equipped with phases higher than three) have been investigated by many researchers due to the following operational advantages (Alfredo and Lipo, 1998 ; Djafar et‘al, 2004; Apsley and Steve 2006):
(i) Increased power ratings due to two winding design option;
(ii) Reduction in current per inverter leg ;
(iii) Increased reliability especially its fault tolerance capabilities;
(iv) Reduction in harmonic contents; and
(v) Wider scope of flexibility in the choice of control scheme.
The research effort on a multi-phase induction machine, having generalized representation of n-windings and phase configuration depicted in Figure 1.2 has not attained maturity. Yet some extremely important findings have been reported in literature indicating general feasibility of multi-phase induction machine of profound potentials. As a corollary, the prime focus of this research work is aimed at investigating design philosophy to secure improved multi-phase induction machine. The underlying design architecture and practical realization of the improved multi-phase induction machine as well as mathematical modeling
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and experimental verification of its performance constitute the research thrusts embarked upon in this dissertation.
Figure 1.2: Generalized Representation of Multi-Phase Induction Machine and Phase Arrangement
1.3 Problem Definition
In recent years, multi-phase induction machines have attracted more focused attention from researchers. To date, various researchers have studied the operation of these machines as generators as well as motors with a view to analysing their performance characteristics as compared to standard three phase machines of similar ratings.
However, a comprehensive review of relevant literature: Ojo and Davidson (2000); Alfredo (1998); Munoz and Lipo (2000)) revealed that the machines either suffer from overheating due to excessive copper losses in the windings or incomplete utilization of the machine. Furthermore, the machine core performance indices such as starting torque and magnetizing current are a function of its inductances. There is therefore the need for an accurate method of determining these inductances. The conventional analytical method of determining these parameters (inductances) is anchored on the winding function approach. It assumes sinusoidal distribution of the winding but in the actual machine, the windings are not b) N-winding Phase Arrangement MECHANICAL LOAD TORQUE Stator Winding 1 Stator Winding n a1 b1 c1 an bn cn a) Schematic Representation of N-winding Induction Machine
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sinusoidally distributed. This assumption therefore introduces error into the values of the inductances obtained. Consequently, performance prediction of the machine using the values of the inductances calculated by winding function method would attract appreciable modelling error.
In summary, the major unresolved research problems that have been identified with respect to dual winding induction machine to date are as follows:
excessive copper loss in the windings by optimizing the machine‘s efficiency;
partial utilization of the machine stator dual windings during running mode; and
Inaccurate method of calculating the machine‘s inductances.
Against the backdrop of the foregoing, the concomitant research questions of prime interest are as follows:
Is it possible to evolve dual stator machine re-design approach to minimize excessive copper losses in the windings?
Is full utilization of machine stator dual winding realizable and how does it impact its architectural construction?
Can a pragmatic analytical framework be developed to facilitate calculations of machine‘s inductances as superior alternative to winding function approach from the standpoint of computation accuracy?
These research questions are addressed frontally in this dissertation via specific problem definition. It seeks, in the main, to optimally redesign dual stator windings (a-b-c and x-y-z) spatially displaced by fixed angle (α degrees) and of similar number of poles to replace existing windings of standard three-phase induction machine without altering the original architecture of the squirrel cage rotor. Embedded in the problem definition are the indispensible requirements to improve efficiency and p.f. of DSWIM design, accurately
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determine DSWIM parameters for its steady/dynamic state simulation studies leading finally to construction of DSWIM prototype to enable extensive experimental validations.
1.4 Aim and Objectives
The aim of this research is to design, construct and carry out performance analysis of an improved dual three-phase stator winding electric machines. (using an integrated analytical, meta-heuristic, simulation and experimental framework). Towards the realization of this aim, the following objectives are pursued:
i. Mathematical formulation of the DSWIM design based on analytical approach and GA optimization to facilitate computations of stator winding leading parameters and application of GA to specifically search for optimum DSWIM efficiency and pf.
ii. Development of a hybrid analytical and meta-heuristic framework for the optimal design of an improved dual three-phase stator winding to achieve the following:
Minimization of excessive copper loss; and
Enforcement of full utilization of stator windings during running mode via appropriate choice of n/n stator winding pole ratios.
iii. Derivation of necessary equations to enable accurate computations of the dual stator winding inductances and resistances that rely on the physical configurations of the stator windings and stator slot geometries, stator bore instead of the widely used winding functions in the existing relevant literature. In addition the following derivations are essential to the overall DSWIM modelling
Fundamental derivations of the voltage equations in generalized time dependent variables and subsequent transformation into time invariant variables;
Computations of winding mutual, self and leakage inductances with special attention given to their accurate derivations ;
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Derivation of the equivalent circuit of the dual stator winding induction machine in d-q-0 reference frame; and
Development of software programs for the simulation of DSWIM in MATLAB environment.
Development of finite element method (FEM) modelling of DSWIM to determine its leading inductances.
iv. Development of stator winding diagram leading to construction of a prototype 3-phase dual stator winding induction machine;
v. Setting up an experimental configured test bed rig dedicated specifically for the prototype 3-phase DWSIM to determine its wide range operational characteristics that include efficiency, torque, etc.
1.5 Overview of the Research Methodology
The research methodology roadmap is summarized in the functional flowchart of Fig. 1.3. The methodology roadmap must of necessity conform to the aim and objectives of this dissertation. For the sake of clarity, some critical research issues to be addressed are further re-iterated as follows:
1. Establishment of the current research status and milestone achievements with respect to multi-phase induction machine and therefrom identify the critical research areas deserving priority attention.
2. Derivations of generalized mathematical model and computation of necessary equivalent circuit inductances to underpin performance analyses of dual stator winding induction machine and to serve as benchmark test-bed model.
3. Development and implementation of the proposed induction machine redesign philosophy to facilitate conversion of conventional induction machine into dual stator winding induction machine of identical or dissimilar pole ratio.
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4. Standard experimental test rigs configured around the redesigned dual stator winding induction machine as well as conventional three phase induction machine of the same rating for comparative evaluations of key performance indices.
5. Investigation of redesigned dual stator winding induction machine model via simulations in MATLAB Simulink as conceptualized in Fig. 1.4 and benchmarking such simulation results against equivalent experimental results for accuracy verifications.
6. Finite Element Modelling of DSWIM according to the generalized framework of Fig. 1.5 to enable determination of stator inductances and flux patterns in the machine air gap and compared with the analytical approach for inductance computations.
7. Comparative evaluations of the dual stator winding induction machine based on simulation results and experimental results.
The overall research goal is to achieve improved dual stator winding induction machine performance from standpoints of energy loss minimisation via optimum participation of the dual stator windings at different levels of mechanical loadings.
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Figure 1.3: Overview of Research Methodology
SIMULATION STUDIES a) Modeling IM & DSWIM in MATLAB; b) Finite element method modeling of DSWIM; LITERATURE REVIEW a) Relevant publications in learned journals b) Advanced Textbooks & Postgraduate Theses in subject area; ANALYTICAL FRAMEWORK a) Derivations of fundamental equations; b) Voltage equations in machine & d-q-o variables and reference frame; and RE-DESIGN & CONSTRUCT DSWIM a) Develop DSWIM re-design procedure; b) Select IM rating to be converted to DSWIM EXPERIMENTAL SETUP ON IM & DSWIM a) Standard experimental work with meters; b) Measure performance indices for DSIM & IM;
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Figure 1.4: Block Diagram of DSWIM in MATLAB/ Simulink Simulation Environment
Figure 1.5: Basic Block Diagram of the Finite Element Method.
1.6 Significance of the Research
The research was concerned with design philosophy targeted at achieving improved dual stator winding induction machine in order to attract superior operational performance not attainable by existing design concepts. This is primarily driven by the global trend towards efficient energy utilisation which, in turn, called for the need to look into new design Supply voltage Shaft Torque Inputs Dimensions Material Data Winding Data Other Variables Currents Rotational Speed Fluxes in Coils Forces Losses Outputs FEM model Generalized Maxwell equations couple the inputs and outputs ∇× 1𝜇∇𝐴 +𝜎𝜕𝐴𝜕𝑡 𝑡→∞=𝐽
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techniques/architectures and implementation of induction machines being dominant players in industrial drive systems. For this purpose attention was herein focused more on the new class of induction machines due to some advantages they possess over other machines. Flexibility, ease of control, ruggedness and the possibility of generating voltage at any speed beyond synchronous are but a few of the inherent qualities of the induction machines. Because of the rapidly growing demand for high power drive system and more flexible operation, multiphase machines are attracting serious attention from researchers. Preliminary review of current literature has established that multi-phase induction motor design trend is yet to attain maturity. This research work is therefore an attempt to deepen maturity of multi-phase induction machine via new design concept and improved modelling strategy.
1.7 Dissertation Organization
This dissertation is divided into six chapters and supported by four appendices. Chapter one is a general introduction. In this chapter, the aim and objectives have been articulated in line with the core research problem addressed. An overview of the methodology adopted to meet the research goals is also presented in the chapter.
Chapter two has two main components: detailed review of fundamental concepts and in-depth literature review of similar works. The detailed review of fundamental concepts provide basic theoretical framework for induction machines and derivations of salient equations of relevance to dual stator winding machine design and analytical treatment. The literature review of similar works entail publications supportive of this dissertation to embark on the research direction identified.
Chapter three is dedicated to fairly extensive mathematical modelling of the dual stator winding induction machine using Park‘s transformation applied to its derived differential
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equations in phase variables. Here, the equivalent circuits of the machine are developed and most importantly the torque equation established.
Chapter four is concerned with the design aspect of the machine based on traditional analytical approach and application of GA to optimize DSWIM efficiency. In addition, magnetic field distribution pattern via finite element analysis is set forth to determine DSWIM leading simulation parameters. A generalized winding architecture was also documented in this chapter.
Chapter five includes simulation results carried out in MATLAB/Simulink environment, results of finite element analysis applied to DSWIM, winding diagrams developed for DSWIM and its prototype realization as well as far reaching results of the experimental work done. Furthermore, comprehensive discussions of all the results obtained are contained in this chapter.
Chapter six focuses on general conclusions, and recommendations. All references duly consulted during this research work and four appendices to reinforce critical technical materials of Chapters two to four as well as two computer program listings developed are provided at the end of the dissertation.
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