DESIGN AND OPTIMISATION OF OUTER-ROTOR HYBRID EXCITATION FLUX SWITCHING MOTOR MD. ZARAFI BIN AHMAD UNIVERSITI TUN HUSSEIN ONN MALAYSIA ii DESIGN AND OPTIMISATION OF OUTER-ROTOR HYBRID EXCITATION FLUX SWITCHING MOTOR MD. ZARAFI BIN AHMAD A thesis submitted in fulfillment of the requirement for the award of the Doctor of Philosophy in Electrical Engineering Faculty of Electrical and Electronic Engineering Universiti Tun Hussein Onn Malaysia SEPTEMBER 2016 iv Dedicated to my beloved father, mother, brothers and sisters and to my beloved wife and children and friends. Thank you for your love, prayer, support, and patience. I love you all deeply. DEDICATION v ACKNOWLEDGEMENTS In the name of ALLAH, the most Gracious and the Most Merciful. Alhamdulillah, all praises to Allah Almighty for His grace and His blessings given to me for the completion of my PhD studies successfully. I also wish to express my gratitude to my supervisor, Assoc. Prof. Dr. Zainal Alam bin Haron and co-supervisor Dr. Erwan bin Sulaiman for their guidance, invaluable help, advice, and patience on my project research. Without their constructive and critical comments, continued encouragement, and good humour while facing difficulties, I could have not completed this research. I am also very grateful to them for guiding me to think critically and independently. I acknowledge, with many thanks, to Ministry of Higher Education Malaysia (MOHE) and Universiti Tun Hussein Onn Malaysia (UTHM) for awarding me scholarship for my PhD programme. I’m much honoured to be the recipient for this award and receiving this scholarship has helped to secure my financial position during my studies and further given me the impetus to strive very hard to complete this research on time. My sincere thanks go to Mr. Gadafi M. Romalan, for his hard work in assisting me to ensure the prototype and experiment test are implemented successfully. I also want to thank Mr. Faisal Khan, Mr. Mohd Fairoz Omar, and Mr. Mahyuzie Jenal for their contributions in sharing their knowledge and experience on electrical machine design. Furthermore, I wish to express my sincere gratitude to my mother and father for their moral support and prayers. I would also thank to my wife for her support, endless encouragement, prayers, and love. To my children Nur Alya Md Zarafi, Muhammad Muaz Md Zarafi, and Muhammad Dariel Madinah Md Zarafi, I want to say thanks for your patience throughout my study period. vi ABSTRACT Permanent Magnet Flux Switching Motor (PMFSM) with outer-rotor configuration recently reported in the literature can potentially lead to a very compact in-wheel electric vehicle (EV) drive design and increased cabin space through the elimination of mechanical transmission gears. Nevertheless, the output torque is still insufficient to drive heavier EV especially at starting and climbing conditions. On the other hand, with the permanent magnets placed along the radial V-shaped segmented stator, the PMFSM is prone to excitation flux leakage and demagnetization, making optimisation of the rotor and stator dimensions a difficult objective to achieve, while keeping the PM volume constant. In this thesis, design and optimisation of high torque capability salient stator outer-rotor hybrid excitation flux switching motor (OR-HEFSMs) are investigated. With the additional DC field excitation coil (FEC) as a secondary flux source, the proposed motor offers advantage of flux control capability that is suitable for various operating conditions. The design restrictions and specifications of the proposed motor are kept similar as interior permanent magnet synchronous motor (IPMSM) employed in the existing hybrid electric vehicle (HEV) Toyota Lexus RX400h. The JMAG-Designer ver.14.1 was used as 2D-finite elements analysis (FEA) solver to verify the motor’s operating principle and output torque performance characteristics. The subsequent optimisation work carried out using deterministic optimisation approach (DOA) has produced a very promising 12S-14P OR-HEFSM configuration, where a maximum torque density of 12.4 Nm/kg and power density of 5.97 kW/kg have been obtained. These values are respectively 30% and 68% more than that produced by IPMSM of comparable dimensions. A reduced-scale prototype 12S-14P OR-HEFSM has also been fabricated to minimize the manufacturing cost and no-load laboratory measurements have been carried out to validate the simulation results. The results obtained show that they are in good agreement and has potential to be applied for in-wheel drive EV. vii ABSTRAK Motor Fluks Teralih Magnet Kekal (PMFSM) dengan konfigurasi pemutar di luar berpotensi digunakan untuk pemacuan kereta elektrik di dalam roda dan menyumbang kepada penyediaan ruang kabin yang lebih luas apabila tiada lagi penggunaan gear penghantaran mekanikal. Walaubagaimanapun, daya kilas yang dihasilkan masih tidak mencukupi untuk memacu kenderaan elektrik yang lebih besar terutamanya pada peringkat permulaan gerakan dan keadaan mendaki. Selain itu, dengan magnet kekal diletakkan di sepanjang jejari teras pegun berbentuk-V, ia terdedah kepada kebocoran fluks dan penyah-magnetan magnet kekal menjadikan teras pemutar dan teras pegun sukar dioptimumkan sekiranya isipadu magnet kekal adalah malar. Tesis ini membincangkan kajian dalam merekabentuk dan mengoptimumkan daya kilas motor fluks teralih pengujaan hibrid dengan pemutar di luar (OR-HEFSM). Dengan adanya tambahan gegelung medan pengujaan arus terus (AT) sebagai sumber fluks kedua, motor yang dicadangkan menjanjikan satu lagi kelebihan iaitu pengawalan fluks menjadi lebih mudah di mana ianya sangat berguna dalam pelbagai keadaan pengoperasian. Kekangan rekabentuk dan spefifikasi motor elektrik yang dicadangkan adalah berdasarkan spesifikasi motor segerak magnet kekal (IPMSM) yang digunakan di dalam kereta elektrik hibrid (HEV) Toyota Lexus RX400h. Perisian JMAG- Designer ver.14.1 telah digunakan sebagai penyelesai analisis unsur terhingga (FEA) dua dimensi (2D) untuk mengesahkan prinsip kendalian dan prestasi daya kilas keluaran motor tersebut. Seterusnya, kajian pengoptimuman daya kilas keluaran telah dijalankan menggunakan kaedah penentuan optimasi dan berjaya menghasilkan OR- HEFSM dengan konfigurasi 12S-14P berketumpatan dayakilas sebanyak 12.4 Nm/kg dan ketumpatan kuasa sebanyak 5.93kW/kg. Nilai tersebut adalah masing-masing 30% dan 68% lebih tinggi berbanding prestasi motor IPMSM dengan diameter motor yang sama. Prototaip 12S-14P berskala kecil telah dibangunkan bagi mengurangkan kos pembuatan dan pengukuran tanpa beban telah dijalankan di makmal untuk mengesahkan keputusan yang diperolehi daripada simulasi komputer. Berdasarkan viii keputusan yang diperolehi menunjukkan ciri-ciri prestasi motor tersebut adalah sejajar dengan keputusan yang diperolehi daripada simulasi dan berpotensi digunakan sebagai pemacu kereta elektrik dalam roda. ix TABLE OF CONTENTS DECLARATION iii DEDICATION iv ACKNOWLEDGEMENTS v ABSTRACT vi ABSTRAK vii TABLE OF CONTENTS ix LIST OF TABLES xiii LIST OF FIGURES xiv LIST OF SYMBOLS AND ABBREVIATIONS xx LIST OF APPENDICES xxiv CHAPTER 1 INTRODUCTION 1 1.1 Research background 1 1.2 Problem statement 2 1.3 Objectives of the study 4 1.4 Scope of works 4 1.5 Thesis outline 5 CHAPTER 2 LITERATURE REVIEW 7 2.1 Introduction 7 2.2 Overview of flux switching machines (FSMs) 7 2.3 Classification of flux switching machines (FSMs) 9 x 2.4 Permanent magnet flux switching machines (PMFSMs) 10 2.5 Field excitation flux switching machines (FEFSMs) 12 2.6 Hybrid excitation flux switching machines (HEFSMs) 16 2.6.1 HEFSM Topologies 16 2.6.2 Design of HEFSMs 19 2.6.3 Outer-rotor flux switching machines 20 2.6.4 Operating principle of OR-HEFSM 22 2.7 Dynamic model and equivalent circuit of OR-HEFSM 23 2.8 Cogging torque of OR-HEFSM 27 2.9 Review of optimisation methods 28 2.10 Summary 29 CHAPTER 3 RESEARCH METHODOLOGY 30 3.1 Introduction 30 3.2 Design process and setting conditions of new topology three-phase OR-HEFSM 30 3.2.1 Initial design of OR-HEFSM 31 3.2.2 JMAG-Geometry Editor 35 3.2.3 JMAG-Designer 35 3.2.4 Perform principle operation of OR-HEFSM 40 3.3 Performance investigation of OR-HEFSM at various rotor pole configurations 41 3.3.1 Torque analysis 42 3.3.2 Power analysis 44 3.3.3 Torque and power versus speed characteristics 44 3.3.4 Losses and efficiency 45 3.3.5 Torque and power densities 46 3.4 Design optimisation and mechanical analysis of OR- HEFSM 47 3.4.1 Mechanical analysis 50 3.4.2 Rotor mechanical strength analysis 50 3.4.3 Permanent magnet demagnetisation analysis 51 3.5 Reduced-scale prototype development of OR-HEFSM 51 xi 3.5.1 Reduced-scale prototype design using SolidWorks 52 3.5.2 Experimental setting 53 3.6 Summary 54 CHAPTER 4 INITIAL DESIGN ANALYSIS OR-HEFSM AT VARIOUS ROTOR POLE CONFIGURATION 55 4.1 Introduction 55 4.2 Operating principle investigation of OR-HEFSM 56 4.2.1 Coil test analysis 56 4.2.2 Flux switching concept analysis 59 4.3 Impact of rotor pole numbers on the performances of OR-HEFSM 60 4.3.1 No-load performances OR-HEFSM at various rotor pole numbers 61 4.3.2 Load Analysis of Initial Design OR-HEFSM 67 4.4 Summary 69 CHAPTER 5 DESIGN REFINEMENT AND OPTIMISATION OF OR-HEFSM 70 5.1 Introduction 70 5.2 Results and performances of 12S-10P OR-HEFSM 70 5.2.1 Initial performances of 12S-10P OR-HEFSM 71 5.2.2 Parameter sensitivity on optimisation of 12S- 10P OR-HEFSM 76 5.2.3 Final design performances of 12S-10P OR- HEFSM 81 5.3 Results and performances of 12S-14P OR-HEFSM 88 5.3.1 Initial performances of 12S-14P OR-HEFSM 89 5.3.2 Design optimisation of 12S-14P OR-HEFSM 94 5.3.3 Performance of final design 12S-14P OR- HEFSM 96 5.4 Mechanical analysis of final design OR-HEFSM based on 2D-FEA 109 5.4.1 Rotor mechanical stress prediction 110