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About this book

This book focuses on how to use magnetic material usefully for electrical motor drive system, especially electrical vehicles and power electronics. The contents have been selected in such a way that engineers in other fields might find some of the ideas difficult to grasp, but they can easily acquire a general or basic understanding of related concepts if they acquire even a rudimentary understanding of the selected contents.The cutting-edge technologies of magnetism are also explained. From the fundamental theory of magnetism to material, equipment, and applications, readers can understand the underlying concepts. Therefore, a new electric vehicle from the point of view of magnetic materials or a new magnetic material from the point of a view of electric vehicles can be envisioned: that is, magnetic material for motor drive systems based on fusion technology of an electromagnetic field. Magnetic material alone does not make up an electric vehicle, of course. Other components such as mechanical structure material, semiconductors, fuel cells, and electrically conductive material are important, and they are difficult to achieve. However, magnetic material involves one of the most important key technologies, and there are high expectations for its use in the future. It will be the future standard for motor-drive system researchers and of magneticmaterial researchers as well. This book is a first step in that direction.

Table of Contents

Frontmatter

Motor Drive System and Magnetic Material: Contents of This Book

Abstract
Motor drive system is now widely applied to a transportation system, and its high efficient and downsizing are required more and more. So magnetic material becomes a key technology for power electronics excitation especially. The relation among electrical motor, power electronics, and magnetic material is described in detail. The contents of this book are shown in briefly.
Keisuke Fujisaki

General (Background of New Magnetic Material Requirement for Power Electronics Technology)

Frontmatter

Technical Requirement to Magnetic Material in Motor Drive System

Abstract
Due to an expansion of electrical motor drive system application for transportation means such as a car, a ship, and an airplane, its high efficient and downsizing technology required more and more. Nowadays, when studies of power semiconductor material as GaN and SiC are going ahead, and 80% of electrical energy is expected to be used through power electronics technology in 2030 such as a realization of distributed power supply system from mW level to GW level, it is said to be that the bottleneck technology has become magnetic material in a viewpoint of downsizing, cost, and efficiency. So a new magnetic material for high power and high frequency is required strongly. One of the solutions for the requirement is thought to be a mutual consideration of magnetic material and power semiconductor. Then, future trend of electrical motor is considered to be motor physics as microscopic direction as well as motor integration as macroscopic direction.
Keisuke Fujisaki

Fundamental Concept of Magnetic Material for Electrical Engineer

Abstract
When external magnetic field is applied to magnetic material, a magnetization phenomenon is caused and big magnetic flux density can be obtained. The big magnetic flux density plays an extremely important role in a motor, a generator, a transformer, and a reactor which are the applied apparatus of the magnetic material in electrical engineering. Therefore, a magnetization phenomenon to obtain the big magnetic flux density and an iron loss produced in magnetization process in AC supplied are important material indexes for magnetic material. Here, an outline about the magnetization process and the iron loss is mainly described on an electrical steel sheet.
Keisuke Fujisaki

Fundamental Concept of Electrical Motor for Magnetic Researcher

Abstract
Electrical motor itself is well known for most of the electrical engineers who have already studied in universities or so. However, it is not always well-known topics for researchers or engineers related to magnetic material or so. In order to research or design the magnetic material of an electrical motor or the related technologies, the magnetic researcher or engineer at least should know the fundamental concept of electrical motor. So, the minimum contents of the summary from the fundamental theory of the electric motor, which are considered to be important for magnetic researcher, are extracted and are explained here. Fundamental theory of electrical motor is explained based on Maxwell equations. As a basic concept of electrical engineering, three-phase AC theory and traveling magnetic field are shown. AC motor theory and PM motor characteristics are finally explained since they are mainly used in EV drive system.
Keisuke Fujisaki

Fundamental Concept of Power Electronics for Magnetic Researcher

Abstract
Power electronics technology has been studied in earnest for more than 40 years, and its application was limited to some electric energy. However, the positioning is going to turn big when 80% of the electric energy comes to be used through a power electronics technology from now on in 10–20 years or so. Therefore, the power electronics technology may be said to be the minimum required knowledge to be learned by not only the electric person concerned but also the person concerned with magnetism. The summary of the power electronics technology is described here, and the detailed explanation is carried out about one-phase inverter dynamic behavior which is said to be one of the most important fundamental concepts in power electronics technology.
Keisuke Fujisaki

Fusion Science and Technology of Electromagnetic Field [1]

Abstract
Fusion science and technology of electromagnetic field is proposed here to obtain a higher efficient and downsizing electrical motor drive system for example. Motor drive system does not consist of only one technology such as electrical motor, control, power electronics, material, and production. “Electromagnetic energy apparatus,” “electromagnetic field application,” and “electromagnetic material” are considered to be related by a transfer of “thing.” Each component requires multi-time for power electronics, multi-physics, and multi-scale, respectively. They should be considered to be a fusion science and technology such as electrical engineering, material, electromagnetic field, fluid dynamics, or so. So, they are called first-class fusion. The relation among the apparatus, the application, and the material is considered to be a relation of purpose and means. The purpose introduces what to make, and the means introduces how to make. So, they are called second-class fusion. It is usually difficult and necessary for a lot of time to learn plural department at the same time in the conventional study system. So, some special study system may be required for them.
Keisuke Fujisaki

Magnetic Material Excited by Power Electronics Equipment

Frontmatter

Magnetic Property and Measurement Excited by PWM Inverter

Abstract
A motor drive system is used as a means of transportation such as electric cars, and an electrical steel sheet used as a core of the motor is excited by an inverter for variable velocity operation. Because the electrical steel sheet is usually evaluated under an excitation of a linear amplifier which does not include time-harmonic components, it has a different magnetic property from the one which is excited by the inverter. So, the magnetic property of the electrical steel excited by the inverter is shown in detail. In the inverter excitation, magnetic characteristics of ring core have a lot of minor loops as closed loop and open loop caused by carrier frequency of the inverter and the ON voltage of the power semiconductors. So, the iron loss increases due to the inverter excitation. When the power semiconductor with small ON voltage is used as a switching device in the inverter, the minor loops become small and the iron loss decreases. Higher sampling frequency for AD converter is required to express the pulse-shape voltage of the inverter. The required magnetic characteristics in inverter excitation depend on how to use the magnetic material on the inverter.
Keisuke Fujisaki

Iron Loss Measurement of Interior Permanent Magnet Synchronous Motor

Abstract
The International Electrotechnical Commission (IEC) as well as the Japanese Industrial Standards (JIS) proposes standard methods for the measurement of soft magnetic material iron loss density. Under these measurements, the magnetic field applied to the material is strictly unidirectional and purely sinusoidal. However, in an electrical motor, the magnetic path is not straightforward, and the magnetic field can be largely rotating. Moreover, when the motor is driven by an inverter using power electronic devices switching at high frequency, the magnetic field can have large high order harmonic content thus harmonic distortion. Because of these effects, simply using the iron loss density data obtained by standard measurements, in order to predict the motor total iron losses, can be inaccurate. Accordingly, ways to measure and separate the effect of different parameters on the iron losses of an interior permanent magnet synchronous motor (IPMSM) are described in this chapter. In the following sections, experimental methodology and numerical calculation methods are first explained. Then, the effects of the inverter switching frequency, PWM modulation index, and dead-time, along with the effect of the motor load on the total iron losses, are investigated.
Nicolas Denis

Electrical Motor Applied by Low Iron Loss Magnetic Material

Abstract
To reduce core loss of an electrical motor, I select lower iron loss magnetic material than conventional electrical steel as NO (Non-Oriented) steel, and GO (Grain-Oriented) steel, amorphous steel and nanocrystal material. They are applied to the electrical motor of IPM-SM (interior permanent magnet synchronous motor) and manufactured as GO motor, amorphous motor, and nanocrystal motor. In GO motor, due to the strong magnetic anisotropy, GO steel is divided into some pieces, and they are arranged so as that the main magnetic flux follows the easy magnetization direction of GO steel. The motor core loss is measured in the drag force test where stator core is excited by the permanent magnet of the rotor. The core loss reduces in order of NO motor, GO motor, amorphous motor, and nanocrystal motor. The measured core loss is in good agreement with the calculated core loss of finite element method. Since the core loss includes the stator loss as well as rotor loss and permanent magnet loss of sintered NdFeB, the calculation data show that the stator loss of the nanocrystal motor is about one-twentieth smaller than the one of NO motor.
Keisuke Fujisaki

Magnetism and Its Modelling

Frontmatter

Origin of Magnetism 90 Years of Misunderstanding

Abstract
After Slater published his paper on Hund’s rule, almost all standard textbooks follow his idea of explaining the origin of magnetism (the reason of stabilization of the magnetic ground state) based on electron exchange energy. However, when his theory was invented, computer was not available to numerically solve many-body electron system, and he omitted the most important contribution from the nucleus–electron interaction (nucleus charge has a sharp peak, but he assumed uniform distribution). We have proved that this omission makes a serious problem of violation of virial theorem, which is a necessary condition for any Coulomb system. We have solved the Schrödinger equation numerically satisfying the virial theorem and proved that the contribution of the nucleus–electron interaction is the fundamental part to reduce the energy for magnetic ground state. Based on the virial theorem satisfaction, we can now distinguish correct and incorrect theories. Most striking fact is that the two-level models assuming the same space wavefuntions such as Hubbard model is incorrect and they should be excluded from the theory of magnetism.
Yoshiyuki Kawazoe

Magnetic Domain Structures and Techniques in Micromagnetics Simulation

Abstract
Ferromagnetic materials exhibit spontaneous magnetizations even without an applied magnetic field. Their internal structure contains regions called magnetic domains in which magnetic moments are aligned in the same direction. Magnetic moments in different domains point in different directions. For example, when the total magnetization in a ferromagnetic material is close to zero (magnetically neutral state or demagnetized state), the directions of the magnetic moments are determined so as to minimize magnetic energy of the ferromagnetic material. To understand the magnetic domain structure, the behaviors of magnetic moments and the magnetic energy of the ferromagnetic material need to be analyzed. Techniques in micromagnetics simulation are extremely effective for analyzing them. In this chapter, the basic terminologies concerning magnetic domains of ferromagnetic materials are introduced, techniques in micromagnetics simulation are explained, and calculation examples of the magnetic domain structures for the ferromagnetic materials are presented.
Fumiko Akagi

Polycrystalline Magnetic Calculation

Abstract
To express the polycrystalline characteristics of magnetic material in numerical calculation, three-dimensional polycrystalline magnetic field analysis is proposed here. LLG calculation for magnetic domain structure should be used, but it usually has a mesh explosion issue for a lot of crystal grains magnetic material. A local coordinate system is set in each crystal grain to express the crystal magnetic anisotropy and a whole coordinate system is set in the polycrystalline of magnetic material to express magnetic flux continuity. Coordinate transform is used to express each physical parameter defined in the different for coordinate system. Each crystal is assumed to have the same magnetic characteristics as BH curve of a single crystal. Finite element method is used for its numerical calculation, because magnetic flux density distribution is obtained in the minimum electromagnetic energy condition. Two cases of GO steel sheet of 80 mm square are picked up as 2 crystal grains and 56 crystal grains. Magnetic flux density distribution of the GO steel is measured by needle method for magnetic flux density and H-coil for magnetic field. The proposed calculation result of magnetic flux density distribution expresses well the measured result.
Keisuke Fujisaki

Magnetic Hysteresis Represented by Play Model

Abstract
The play model is a simple and efficient hysteresis model that is mathematically equivalent to the classical Preisach model. The play model requires only one-dimensional integral, whereas the Preisach model is described by a two-dimensional integral basically. The relation between the Preisach distribution function and the shape function of the play model is explained. Based on the Everett integral for the Preisach model, a method for identification of the play model is presented, where the shape function is determined from given symmetric hysteresis loops. For the application to the magnetic field analysis using the magnetic vector potential, B-input play model is also explained. Isotropic and anisotropic vector play models are presented, which are required for 2D and 3D magnetic field analyses.
Tetsuji Matsuo

From a Thermodynamic Model to a Magnetic Hysteresis Model

Abstract
The magnetic characteristics of magnetic materials are determined by various factors such as the type and arrangement of atoms comprising the microstructure, that is, the crystalline structure. This model uses a coarse-grained modeling approach to capture the relationship of this microscale phenomenon as it relates to the macroscale behavior of magnetic materials. One of the methods of coarse-grained modeling is defined according to state variables having no correlation with the history of the material such as temperature and pressure, taking into account thermodynamic state variables such as energy and entropy. However, the phenomenon of hysteresis that appears in magnetism is clearly dependent on the history of the material; therefore, there are various difficulties involved in this sort of thermodynamic approach. At the heart of the phenomenon of hysteresis exists a state variable called free energy, which can be described according to thermodynamics, but it is obfuscated by a phenomenon resembling macroscale friction. Therefore, here we introduce a model to describe the resulting historically dependent magnetic properties.
Fumiaki Ikeda

Equivalent Circuit of AC Magnetic Fields

Abstract
An effective equivalent circuit method suitable for high-frequency usage is explained in this chapter. This equivalent circuit is based on the ladder network originally proposed by Wilhelm Cauer (1900–1945) in the field of network synthesis. This method enables significant reduction of computations and also enables coupled analysis of magnetic field and electric circuit. Models for the magnetic sheet and magnetic wire with cylindrical shape are presented. Moreover, the universal method for modeling of arbitral eddy-current fields is introduced.
Yuji Shindo

Coupled Analysis of Semiconductor Characteristics and Magnetic Properties

Abstract
This chapter presents an analysis with mutual consideration of the characteristics of semiconductor components used as switching devices in a DC–AC inverter and the characteristics of the magnetic material constituting iron core of electric equipment. The on-voltage characteristics of semiconductor components affect the magnetic hysteresis characteristics of the magnetic material considerably. Besides, we introduce a numerical calculation method based on the play model that can take into account the interaction between these characteristics efficiently. The play model is utilized to consider and express the magnetic hysteresis phenomenon; this model can calculate a magnetic flux density waveform (magnetic field strength waveform) from an arbitrary magnetic field strength waveform (magnetic flux density waveform) by preparing several magnetic hysteresis loops for identification process. Because the conventional play model only can express the magnetic hysteresis in the DC field, the classical eddy current theory and the Cauer equivalent circuit theory are additionally applied in this study for considering the eddy currents in the AC field; in detail, the Cauer theory is used to analyze the reaction magnetic field caused by the carrier frequency in the pulse-width modulation (PWM) inverter excitation, where the skin effect cannot be ignored. To validate effectiveness of the designed calculation method, an example of magnetic characteristics under the PWM inverter excitation using two different types of semiconductor components with large and low on-voltages are conducted; finally, magnetic hysteresis loops obtained by the calculation method and experimental measurements are compared and evaluated.
Shunya Odawara, Nguyen Gia Minh Thao

Vector Magnetic Characteristic

Abstract
The vector magnetic characteristic was obtained by reexamining and reconstituting the conventional magnetic characteristic. The fundamental viewpoint grasps the magnetic characteristic in the vector relation. This magnetic characteristic leads to the magnetic characteristic analysis, and it is useful for the design development of electrical machinery and apparatus.
Masato Enokizono

Future Magnetic Material

Frontmatter

History and Future of Soft and Hard Magnetic Materials

Abstract
Magnetic materials are essential in modern daily life as they are used in numerous areas, such as electronics, industrial equipment, and automobiles, as energy conversion materials that drive devices such as generators, which convert kinetic to electrical energy, and motors, which convert electrical to kinetic energy. This chapter introduces the technological history and representative examples of magnetic materials. Further details can be found in Refs. [112].
Satoshi Sugimoto

Low-Loss Soft Magnetic Materials

Abstract
Features of amorphous and nanocrystalline alloys which recently draw attention as low-loss soft magnetic materials for motor cores are presented. As an example, experimental results of an energy-efficient 11-kW axial-gap motor using amorphous alloy stator cores are shown.
Shin Nakajima

Nd–Fe–B-Based Sintered Magnet

Abstract
Sintered magnets based on neodymium (Nd), iron (Fe) and boron (B) were invented in 1982. They exhibit the highest performance among the industrially manufactured magnets. Nd–Fe–B magnets not only show excellent magnetic properties but are suitable for mass production as well. Therefore, they are used for many applications, especially for high-performance motors. This chapter offers basic knowledge for understanding Nd–Fe–B-based sintered magnet, including general features, an Nd2Fe14B compound, phase diagram of Nd–Fe–B magnet, manufacturing process and efforts for realising high performance.
Takeshi Nishiuchi

Bonded Rare Earth Permanent Magnets

Abstract
A bonded magnet is a generic term for composite permanent magnets obtained by solidifying and shaping various magnetic powders with a binder. Plastic magnets or “Pla-Mag” are synonyms. Magnetic properties themselves are inferior to sintered magnets because they contain a binder in addition to the magnet powder and fine pores remain after forming. However, because of its high degree of freedom of shape, it is possible to manufacture various near-net shape magnets with high accuracy such as thin-walled ring. It has also the characteristics that the toughness of the molded body is high, cracking is less likely to occur, and integral molding with a shaft or the like is possible. It is superior to sintered magnets in terms of being able to reduce core wobbling, etc., and many are used for small motors for electronic devices and the like.
Kenji Ohmori

The Rare Earths Problem for Permanent Magnets

Abstract
The rare earths criticality issue in the permanent magnets implies in a narrower sense the sudden inflation of prices of rare earth oxides and alloys that stared in 2011 and ceased in 2012 as a result of mishandling of the market in China, but more generally, it includes the issues concerning the rare earth resources and/or supply risks caused by rapid increase of the market demands coupled with increasing environmental regulations on mining or smelting operations in developing countries. Thus, there has existed R&D efforts for the development of permanent magnets that do not use or significantly reduce the usage of the rare earth metals for more than a decade, and their importance is ever increasing. In this chapter, this issue is briefly overviewed.
Satoshi Hirosawa

High-Frequency Magnetics

Abstract
When the magnetic material is used as the high-frequency devices such as RF inductor, the domain walls do not move; so, a soft magnetic material with an uniaxial magnetic anisotropy is often used in the case. A magnetic field is applied in the direction of the hard axis, and magnetization rotation is used in the soft magnetic material. In the soft magnetic material, not only the higher real part and the lower imaginary part of the complex permeability but also the electrical resistivity should be high. For example, when it is used for the magnetic core of an inductor, eddy current loss increases when the electric resistivity of the material is low. In addition, we also need various resources such as reducing the eddy current loss by putting a slit in the magnetic material in order to apply it in RF devices.
Makoto Sonehara

Magnetic Application

Frontmatter

Iron Loss Analysis of Motors

Abstract
In this chapter, methods to calculate iron losses of motors by using electromagnetic field analysis are presented. First, the components of iron loss, i.e., hysteresis loss, eddy current loss, and excess loss, are explained. Next, the iron loss calculation methods that consider the effects of nonlinear characteristics of the core materials, mechanical stress, and harmonic fields are summarized. Several approximations for the practical loss estimation are introduced. Finally, an application of the iron loss calculation method to motors is indicated.
Katsumi Yamazaki

Iron Loss of the Inductors

Abstract
Since inductors used in power electronics circuits are magnetized under completely different conditions from sinusoidal alternating voltage/current, the manner of occurrence of iron loss is often greatly different. In this chapter, we clarify the difference between the magnetizing modes of the transformer and inductor used in the power electronics circuit and introduce recent research examples on the method of measuring and calculating the iron loss of the inductor.
Toshihisa Shimizu

Application of Magnetism to Automobiles

Abstract
Automobiles are designed to provide safe and comfortable movement to people all over the world. In order to accomplish this mission, car makers have focused on functional development including safety performance, environmental performance, driving performance, and provision of comfortable space. A wide variety of material technologies related to magnetic circuits is applied in the automobiles. These technologies have supported the development of the automobile industry and have become indispensable for high functionality and performance of the automobiles. This section will describe the relation between the basic functions of automobiles, namely, “run,” “turn,” and “stop,” discuss the application of magnetism from the historical point of view, and explain the latest technologies and future prospects.
Tetsuya Aoki

Magnetic Application in Linear Motor

Abstract
In this chapter, small- and medium-sized linear motors used in the industrial field are considered, firstly classified into four types based on their operation principle, and their each features are described. Next, the method of characterizing the linear motor is explained, and some of the characteristic evaluation indexes are shown. Furthermore, in order to evaluate the characteristics of the linear motor, the relation between the thrust and the tangential stress is explained, and the traditional magnet array, the repulsion type array, and the Halbach magnet array are shown as the magnet arrangement in the case of permanent magnet field. In addition, recently developed several high-performance linear synchronous motors are classified into permanent magnet field type and variable reluctance type from the viewpoint of thrust source. Finally, the values of the motor constant square density of those synchronous motors are compared.
Hiroyuki Wakiwaka

Backmatter

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