APPLICATION OF MAGNETIC HYSTERESIS MODELING TO THE DESIGN AND ANALYSIS OF ELECTRICAL MACHINES Maged Ibrahim A Thesis In the Department of Electrical and Computer Engineering Presented in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy (Electrical and Computer Engineering) at Concordia University Montreal, Quebec, Canada Noverber 2014 © Maged Ibrahim, 2014 CONCORDIA UNIVERSITY SCHOOL OF GRADUATE STUDIES This is to certify that the thesis prepared By: Maged Ibrahim Entitled: Application of Magnetic Hysteresis Modeling to the Design and Analysis of Electrical Machines and submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Electrical and Computer Engineering) complies with the regulations of the University and meets the accepted standards with respect to originality and quality. Signed by the final examining committee: Chair Dr. R. Ganesan External Examiner Dr. J. O. Ojo External to Program Dr. R. Sedaghati Examiner Dr. A. Sebak Examiner Dr. L. A. C. Lopes Thesis Supervisor Dr. P. Pillay Approved by _________________________________ Dr. A. Sebak, Graduate Program Director November 25, 2014 _____________________________________ Dr. A. Asif, Dean Faculty of Engineering and Computer Science ii ABSTRACT Application of Magnetic Hysteresis Modeling to the Design and Analysis of Electrical Machines Maged Ibrahim, Ph.D. Concordia University, 2014 Permanent magnet synchronous machines (PMSMs) with rare-earth magnets are widely used in the traction drives of electrical and hybrid electrical vehicles, as they can provide high efficiency and torque density. Due to the possibility of future shortage of rare-earth materials, it is essential for electric vehicle industry to find alternative magnet technologies that can provide a substitute for rare-earth PMSMs. Permanent magnet machines with Alnico magnets can theoretically provide torque densities comparable to rare-earth PMSMs, due to their high remnant flux density. However, these magnets are rarely used in the conventional designs of PMSMs, as they can be demagnetized by the armature field. The thesis presents a novel design for permanent magnet machines with Alnico magnets. The proposed design can provide high air gap flux density at no-load, and the armature field at full load tends to enhance the magnet flux. Therefore, the machine can operate with high torque density even under severe loading conditions. The demagnetization characteristics of Alnico magnets are also utilized to achieve high efficiency at a wide speed range, as the magnet flux is reduced at high speeds by armature current pulses that iii dissipate negligible losses, thus avoiding the additional copper losses of the continuous flux weakening current in conventional rare-earth PMSMs. The simulation of the demagnetization and magnetization dynamics of the proposed machine design requires considering the hysteresis characteristics of the permanent magnets. Therefore, finite element analysis (FEA) simulations for the designed machine are performed using a linearized hysteresis model for Alnico magnets. The thesis also aims to improve the design and modeling of electrical machines by developing computationally efficient methods for incorporating the hysteresis characteristics of electrical steel into electrical machine models. iv ACKNOWLEDGMENTS I would like to express my deep appreciation to my supervisor Dr. Pragasen Pillay for his invaluable guidance and continuous support throughout my MA.Sc and Ph.D studies. I am really grateful to work with such a visionary professor and such a caring person. Many thanks to all of the other professors and colleagues in the Power Electronics and Energy Research (PEER) group for their help and insightful discussions. I also would like to express my deepest gratitude to my parents for their unconditional support throughout my whole life. My sincere gratitude extends to my beloved fiancée, Rodaina El-Sarraf, for her emotional support and continuous encouragement. v TABLE OF CONTENTS List of Figures ................................................................................................................................ x List of Tables .................................................................................................................... xx Nomenclature .................................................................................................................... xx List of Symbols ........................................................................................................................ xxiii 1. Introduction ............................................................................................................................ 1 1.1 Background .................................................................................................................... 1 1.2 Objective ......................................................................................................................... 3 1.3 Thesis Outline ................................................................................................................ 4 2. Hysteresis of Magnetic Materials ....................................................................................... 5 2.1 Introduction .................................................................................................................. 5 2.2 Modeling of Magnetic Materials .............................................................................. 7 2.2.1 Hard Magnetic Materials...............................................................................7 2.2.2 Soft Magnetic Materials .................................................................................... 12 3. Design of Variable Flux Permanent Magnet Machine Using Alnico Magnets .......... 14 vi 3.1 Review of Variable Flux Machines .......................................................................... 14 3.2 Analytical Machine Design ................................................................................ 17 3.2.1 Magnet Orientation.................................................................................17 3.2.2 Magnet Type.............................................................................................18 3.2.3 Magnet Dimensions..................................................................................20 3.3 Finite Element Based Machine Design .............................................................. 21 3.3.1 Hysteresis Based Finite Element Stimulation..........................................22 3.3.2 Number of Poles.......................................................................................29 3.3.3 Stator Design.............................................................................................31 3.3.4 Rotor Design.............................................................................................44 3.4 Analysis of the Machine Performance ...................................................................... 57 3.4.1 Torque-Speed Characteristics ............................................................................ 57 3.4.2 Efficiency Analysis ............................................................................................. 62 3.5 Experimental Validation .................................................................................... 71 3.6 Summary............................................................................................................75 vii 4. Hysteresis Loss Prediction In Electrical Machines ........................................................ 76 4.1 Introduction .................................................................................................................. 76 4.2 Hysteresis Loss Measurement ................................................................................... 77 4.3 Hysteresis Loss Modeling .......................................................................................... 81 4.3.1 Analytical Model........................................................................................81 4.3.2 Energetic Model.........................................................................................85 4.3.3 Hybrid Model..............................................................................................92 4.4 Prediction of Hysteresis Loss in Switched Reluctance Machines ........................ 95 4.5 Summary .................................................................................................................... 102 5. Hysteresis Dependent Model for the Brushless Exciter of Synchronous Generators......... 103 5.1 Introduction ............................................................................................................... 103 5.2 Hysteresis Effect on the Brushless Exciter Transient Response ........................ 105 5.3 Hysteretic Model ...................................................................................................... 107 5.4 Identification of the Hysteretic Model Parameters .............................................. 108 5.5 Brushless Exciter Model ......................................................................................... 113 viii 5.6 Measurements of the Exciter Parameters........................................................117 5.7 Experimental Validation..................................................................................121 5.8 Summary...........................................................................................................124