Rare-earth end magnets of a miniature race-track microtron and their tuning

The design and tuning of end magnets of a compact 12MeV race-track microtron (RTM) which is under construction at the Technical University of Catalonia are described. These magnets are systems composed of four dipoles with a Rare-Earth Permanent Magnet (REPM) material used as a source of the magnetic field. The magnetic field level is adjusted by means of tuning plungers in the steel poles. We discuss the end magnets design and results of simulations of the field distributions and describe the REPM blocks magnetization and magnetic field measurements applied in this work. Also, the techniques used for the field distribution tuning procedure are explained in detail. Finally, we discuss results of simulations of particle trajectories in the measured magnetic field of the assembled and tuned end magnets and show that they can provide a passage of the synchronous particle through all orbits of the RTM and therefore the correct operation of the machine.

As symbolized in many logos, mechanical gears have significant impact on daily life and industrial modern society. By fully utilizing the mechanical gears and gearboxes, torque and speed can be properly varied for various applications. However, they inevitably suffer from the demerits of annoying noise, contact friction and regular maintenance. Magnetic gears are considered as one of the most promising candidate for the traditional mechanical gears because they offer the advantages of physical isolation, maintenance free, silent operation and inherent overload protection. However, a direct replacement of mechanical gears by magnetic gears cannot solve the problems aroused by the mechanical gearboxes. Namely, the gear ratio of magnetic gears cannot be adjusted whereas the gear ratio of mechanical gears can be flexibly varied via the gearboxes for different load requirements.
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\nIt is well known that the renaissance of magnetic gears mainly attributes to the invention of rare-earth permanent magnet (PM) materials which take the definite advantages of high energy and flux density. Although the rare-earth PM materials such as neodymium-iron-born (NdFeB) and samarium-cobalt (SmCo) are widely adopted for magnetic gears, there is an increasing concern on the price and supply of the rare-earth elements. Particularly, the use of non-rare-earth aluminum- nickel-cobalt (Alnico) PM material takes the merit of high Curie temperature which is very acceptable for industrial application. Also, by purposely employing the low coercivity of the Alnico PM material, the memory machines perform controllable magnetization to flexibly vary the air-gap flux density, hence achieving the wide constant-power speed range.
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\nThe purpose of this thesis is to design a new type of magnetic variable gear by combining the concept of magnetic gear and the concept of memory machine. Firstly, the background information and the development of flux-controllable PMs are introduced. Secondly, the previous research worked on magnetic gears is presented. Next, the cost-effectiveness comparison between rare-earth PMs and non-rare-earth PMs is sufficiently conducted. After that, a new magnetic gear with multiple controllable gear ratios is proposed, with emphasis on mathematical deduction of the design principle and operation principle. By using finite element analysis, the electromagnetic performances of proposed magnetic variable gear at different gear ratios are investigated. Then design optimization of coaxial magnetic variable gear is conducted and analyzed. Two kinds of methods aiming to increase the torque capability and reduce the torque ripple are discussed. Furthermore, the concept of coaxial magnetic variable gear is extended to the axial-field counterpart. The electromagnetic performances of proposed axial-field MVG is investigated by finite element method. Furthermore, two kinds of industrial applications of coaxial magnetic gears, including wind power system and hybrid propulsion system, are investigated. Finally, a prototype is built up for the verification of the gear ratio changing concept. Hence the corresponding validities are further verified by experimental results.

NdFeB (Neodymium magnets) rare earth permanent magnet is an advanced magnetic material characterized by a high energy product and excellent magnetic performance, which has broad application prospects. With the rapid development of 3D printing technology, its application in the research and fabrication of rare earth permanent magnet materials has become a research hotspot. This paper reviews the latest research developments of rare earth permanent magnet NdFeB materials in 3D printing. It introduces the basic properties and applications of rare earth permanent magnet materials and highlights the main challenge these materials faced, which is how do we improve their solid content. Additionally, the advantages and challenges of 3D printing technology in preparing rare earth permanent materials are analyzed in this paper. By comparing the variations in magnet properties of ferrite and rare permanent magnet materials with increasing temperature, it is found that the latter have relatively poor magnetic stability at high temperatures. Based on these points, the paper summarizes optimization methods of the current 3D printing process for rare earth permanent magnet materials. Finally, the paper discusses the development prospects of rare earth permanent magnet materials in 3D printing, as well as problems need to be solved and future research directions.

Hybrid and electric vehicle technology has seen rapid development in recent years. The motor and the generator are at the heart of the vehicle drive and energy system and often utilize expensive rare-earth permanent magnet (PM) material. This paper reviews and addresses the research work that has been carried out to reduce the amount of rare-earth material that is used while maintaining the high efficiency and performance that rare-earth PM machines offer. These new machines can use either less rare-earth PM material, weaker ferrite magnets, or no magnets; and they need to meet the high performance that the more usual interior PM synchronous motor with sintered neodymium-iron-boron magnets provides. These machines can take the form of PM-assisted synchronous reluctance machines, induction machines, switched reluctance machines, wound rotor synchronous machines (claw pole or biaxially excited), double-saliency machines with ac or dc stator current control, or brushless dc multiple-phase reluctance machines.

The price fluctuation and the unstable supply chain of rare-earth permanent magnet (PM) have posed potential risks for further application of rare-earth PM motors. To alleviate the consumption of rare-earth PM material, a less-rare-earth PM brushless motor with two types of PM materials is proposed in this paper. The key of this motor is that the rare-earth PM is purposely combined with a non-rare-earth ferrite PM, forming the hybrid PM excitation. To design the proposed motor efficiently, a multi-objective stratified optimization strategy is proposed, where the selected five optimization objectives of output torque, PM cost, cogging torque, torque ripple, and efficiency are divided into two levels. Then, different optimization methods are skillfully combined to meet the specific design requirements. The corresponding electromagnetic performances are analyzed and compared with the baseline rare-earth PM brushless motor. Finally, several experiments of the two motors are carried out for evaluation. Both theoretical analysis and experimental results verify the feasibility and validity of the proposed motor and the optimization method.

This paper proposes a new interior permanent-magnet machine (IPMM) design in which the rotor consists of several rotor segments arranged in the axial direction, aiming to improve the utilization of rare earth permanent-magnet (PM) materials and reduce the torque ripple. The proposed design is optimized to feature a 21% reduction of rare earth PM materials and a 50% reduction of ripple torque ratio compared with the Camry 2007 design, which uses the conventional pole-shaping technique to suppress its torque ripple. Although the torque is reduced by 9%, the torque per magnet weight is improved by 15%, indicating the PMs are more efficiently used in the proposed design. The designs are verified by 3-D finite element. Despite the small torque reduction, the efficiency of the proposed design is still about the same as the Camry design.

Improved Electrical Insulation of Rare Earth Permanent Magnetic Materials With High Magnetic Properties

THE PURPOSE. The use of rare earth permanent magnets in electric motors has become commonplace. The use of rare earth magnets in electric motors, such as neodymium (NdFeB), gives a significant increase in the characteristics of the electric motor. The prices of permanent magnet motors made of rare earth elements are highly dependent on the prices of magnets. So in 2012, prices for rare earth magnets increased sharply, which in turn led to a sharp increase in the cost of electric motors. The difficult situation in the world, as well as a possible new price hike for rare earth magnets, is worrying. Therefore, alternatives to rare earth permanent magnets should be considered. The aim of the study is to study and compare various alternatives to rare earth permanent magnets. Compare different types of electric motors. METHODS. When solving the tasks set, a comparative analysis of magnets made of various materials was carried out, which could replace neodymium magnets, which are most often used in electric motors. A comparison of different types of electric motors was also made. RESULTS. The article describes the relevance of the topic under consideration. The problems associated with the use of rare earth magnets are considered. Alternative options for rare-earth magnets, which are used in electric motors, are considered. Various types of electric motors are considered, the pros and cons of various types of electric motors are given. CONCLUSION. The article describes the reasons why it is necessary to abandon the use of rare earth magnets in electric motors (the most common neodymium magnets). The negative aspects of the use of rare earth magnets in electric motors are described. Alternative applications of rare-earth magnets in electric motors are described. This describes the possibility of restoring rare earth magnets, as well as the possibility of using various materials to create permanent magnets. After studying the problems with the use of rare earth magnets in electric motors, they came to the conclusion that it is necessary to consider various options for electric motors that would use magnets without the use of rare earth elements. Or consider different types of electric motors that do not use permanent magnets. So to replace the widely used neodymium magnets, ferrite magnets can come.

The development of new energy automobile is important for the protection of the environment, solving the energy crisis and enhancing our competitive strength in the automotive industry. At present, the industry has not achieved the scale and industrialization. This paper is to research the impact factors about development of new energy automobile industry. It finds that the development of new energy automobile industry has a great relationship with the engine. Rare earth permanent magnet material is one of the ideal raw materials of the engine motor. Healthy development of rare earth permanent magnet material can promote implementation of new energy automobile industry.

Introduction: The non-renewable nature of rare-earth materials and their increasing demand have led to rising prices for rare-earth Permanent Magnet (PM) materials, thereby increasing the manufacturing costs of the corresponding motors. Reducing reliance on rare-earth materials while ensuring the operating performance of motors has attracted significant research attention, resulting in fewer rare-earth permanent magnet synchronous motors emerging in this context. This paper introduces a less rare-earth Permanent Magnet Synchronous Motor (PMSM) with a novel rotor permanent magnet structure, which has been designed, analyzed, and optimized. The primary feature of this motor is the stepped structure of the rotor, composed of neodymium iron boron, which enhances overall performance. Methods: The proposed motor is designed, simulated and analyzed by using the finite element analysis method using ANSYS Maxwell electromagnetic simulation software. Results: By improving the shape of the rotor neodymium-iron-boron permanent magnets, the motor offers the advantages of low cogging torque, low harmonic reverse Electromotive Force (EMF) at no load, and a more sinusoidal air-gap flux density waveform. This paper provides effective verification through simulation analysis. Discussion: The optimisation results of the motor are analysed in terms of rotor permanent magnet shape, main stage NdFeB angle, air gap length, NdFeB material, and number of motor coil turns. Conclusion: The proposed motor not only reduces the cogging torque and no-load back EMF harmonics, but it also makes the air gap flux density waveform closer to sinusoidal by optimizing the rotor structure while achieving the rated load torque requirement.

First-principles study of structural stability and magnetic properties of Sm2Co17 rare earth permanent magnets doped with transition metal elements☆

This paper analytically derives the optimal permanent magnet (PM) arc ratio of the consequent-pole PM (CPM) machines to improve the utilization of rare earth PM material and maximize the output torque. The relationship between the output torque and the PM-arc ratio is established. Moreover, the optimal PM-arc ratio is analytically derived and confirmed by finite element (FE) analysis. It is found that the optimal PM-arc ratio is determined by the ratio of the airgap length to the PM thickness, and its influence on the optimal PM-arc ratio is investigated as well. The electromagnetic performances of the CPM machine with the optimal PM-arc ratio, including the open-circuit airgap flux density, the back EMFs, the average torque, and the torque ripple, are compared with those of the conventional surface-mounted PM (SPM) machine. It is demonstrated that the CPM machine with optimal PM-arc ratio features 33% reduction of PM volume and its torque ripple is almost unchanged compared with the conventional SPM machine. Although the output torque is decreased by 8%, the torque per PM volume is improved by 38%. Finally, a 12-slot/10-pole CPM machine is prototyped and tested to validate the analyses.

This paper proposes a novel interior permanent magnet machine (IPMM) design in which the rotor employs U-shape magnet cavities filled with both rare earth and ferrite permanent magnets (PMs). The design aims to replace a portion of rare earth PM materials by ferrite magnets in order to minimize the material cost. The proposed design has been developed based on the Camry 2007 V-type IPMM, which serves as the baseline design in the performance comparison. The performance of the proposed design has been verified by the finite element method (FEM). The proposed design uses 20% fewer rare earth materials to achieve a 4% higher torque performance than the baseline design. The demagnetization analysis proves that the ferrite PMs in the proposed design have the same susceptibility as that of the rare earth PMs in the Camry design to the demagnetization field.

For a steady growth of the permanent magnet industry, resilience to the supply chain of raw materials has become one of the primary issues in the materials research. To be resilient, it would be desirable to have a variety in portfolio of materials performing similarly. However, development of permanent magnets has not pursued such a direction. In this presentation, the speaker tries to summarize recent major developments in rare earth permanent magnet materials, paying attention not only to magnetic performance but also to a balanced usage of rare earth elements, and present possible directions of future R&D of permanent magnets. Guided by decades of fundamental studies on coercivity mechanism in REPMs, the basic strategy to save an indispensable magnetic rare earth elements in an REPM is now consisted of; (1) decoupling hard magnetic grains with a thin, non-ferromagnetic, boundary phase, (2) reduction of the grain size to suppress local demagnetization fields, and (3) allocation of the indispensable elements selectively at the most effective position, i.e., the surface atomic layers of the main phase. Grain boundary diffusion (GBD) process has already become a standard process to accomplish this strategy in the Nd-Fe-B sintered magnets with the high-end specifications. The GBD process for hot-deformed Nd-Fe-B, which requires low processing temperatures, has also been realized by introducing low melting-point alloys such as eutectic Nd-Cu. For a balanced usage of other rare earth elements, the Sm-based magnet are attracting revived attentions: The 2-17-type Sm-Co with increased Fe/Co ratio shows an improved magnetic energy density. For bonded magnets, Sm2Fe17N3 single crystalline powders are suitably used. Inducement of a large-enough coercivity in anisotropic bulk magnets with the “1-12” type high-magnetization Sm-Fe-Co compounds remains under struggle. On the other hand, dilution of Nd with Ce and La in the Nd-Fe-B magnets has become a practical solution. It may follow that the highest energy product will be no longer the top priority but the variations in the portfolio will. To strengthen resiliency in permanent magnet industry, it would be necessary to establish methodology to quickly develop alternatives in the materials portfolio. An important ingredient of these research activities would be construction of a multi-component data base for computational thermodynamic assessment of rare earth permanent magnet alloys. Another, probably the most important, would be usage of artificial intelligence to minimize the experimental verification.

China has the world’s largest reserves of rare earth elements. Rare earth permanent magnet material has always been one of the popular industries in the investment market. CAPM is the basic asset-pricing model in financial economics. There are a number of studies conducted to examine the applicability of CAPM to stock markets in different industries and to investigate the modification method to improve the model’s prediction accuracy. In this study, seven leading enterprises in China’s rare earth permanent magnet material industry listed on the A-share market were selected as the research subjects. Based on CAPM, regression analysis was conducted on the monthly data from March 2016 to February 2022. The results demonstrated that using the ? coefficient to explain the risk of China’s rare earth permanent magnet industry is ineffective. The ultimate benefit was less affected by market indexes but mainly by non-systematic risks. CAPM has low applicability to China’s rare earth permanent magnet material industry and requires further improvement. Nevertheless, CAPM still has some guiding significance in making enterprise comparisons and investment decisions.