Ferrite Permanent Magnet Research Articles

Analysis and Optimization of a V-Shape Combined Pole Interior Permanent-Magnet Synchronous Machine With Temperature Rise and Demagnetization Considered

Interior permanent-magnet synchronous machines (IPMSMs) have the advantages of high efficiency, high power density and outstanding flux-weakening ability, which make them widely adopted in electric vehicles (EVs). Conventional IPMSMs using rare-earth permanent magnet (PM) materials face the problems of instable price and irreversible demagnetization under extreme operating conditions. To overcome these shortcomings, a V-shape combined pole IPMSM (VCP-IPMSM) is proposed, in which NdFeB PMs at the outer ends of V-shape pole are replaced by ferrite PMs. The improvement of the magnetic-pole scheme on air-gap flux density is analyzed, and the influences of the magnetic-pole geometries on electromagnetic performance are investigated. The thermal circuit model of VCP-IPMSM is established, and the demagnetization characteristics of the machine at different temperatures are analyzed, by which the thermal and demagnetization constraints of magnetic pole are obtained. The genetic algorithm based on response surface models is applied to optimize the magnetic-pole cost and electromagnetic torque simultaneously. Accordingly, with thermal and demagnetization constraints integrated with the optimization method, an optimum scheme is obtained. In comparison with the conventional IPMSM with single-material pole, the proposed VCP-IPMSM is proved to be able to promote the air-gap flux density quality, improve the anti-demagnetization ability at high temperature, and decrease the rare-earth PM consumption with the output torque remaining unchanged.

Comparison between rare-earth and ferrite permanent magnet flux-switching generators for gearless wind turbines

Flux switching generators with permanent magnets (PMs) on the stator is a good alternative to traditional synchronous generators for gearless wind turbines. This paper is dedicated to the comparison of the 3-phase rare-earth and ferrite PM flux switching generators considered in gearless wind generator application (332 rpm, 1784 W). The machines are designed and optimized using the Nelder–Mead algorithm coupled with 2D FEM model. The objective function is built taking into account the following objectives: the average efficiency of the generators over the wind turbine profile, the required power of the AC–DC converter, the quantity of the magnets and the torque ripple. It is found that the ferrite PM flux switching generator can be an attractive alternative to the rare-earth one. The averaged efficiency of the generator with ferrite PM is higher by 4.1% than that of the rare-earth one. The active power of the ferrite generator is also higher in a wide range of powers. Although the mass of the ferrite PM generator is 2.4 times higher, the costs of the generators are approximately similar since the rare-earth magnets are much more expensive than ferrite ones.

Synchronous reluctance machines: performance evaluation with and without ferrite magnets

Nowadays, a great interest in the efficiency and the cost of electrical machines has been noticed. Therefore, Synchronous Reluctance Motors (SynRMs) have become more attractive alternative for induction and permanent magnet (PM) synchronous machines in several industrial applications. This is because they do not use rare-earth magnets, windings and cages in their rotor. Consequently, the cost and efficiency are improved. Nevertheless, a major problem of the SynRMs is the low power factor. To improve the power factor as well as the torque density and efficiency, the cheap ferrite PM can be inserted in the rotor, resulting in the so called ‘PM assisted SynRM’. The rotor design of SynRMs with and without permanent magnets (PMs) has a huge effect on the motor efficiency, torque density and power factor. This paper introduces an evaluation for the performance of SynRMs with and without PMs in terms of efficiency, torque and power factor maps as a consequence of different rotor designs. Three different rotor designs for the same machine stator have been compared. For one machine, the experimental measurements are obtained and the validation of the simulation results are confirmed. A preprint of this work is available under: https://biblio.ugent.be/publication/8515429.

Design of High-Speed Multilayer IPMSM Using Ferrite PM for EV Traction Considering Mechanical and Electrical Characteristics

This article proposes a design method of the high-speed multilayer interior permanent magnet synchronous motor (HSML IPMSM) employing the ferrite permanent magnet (PM). Since the maximum speed of the traction motor in this article is 15 kr/min, the mechanical stability must be considered. Additionally, in the case of the HSML IPMSM, as the number of the PM layers increases, the thickness of the PMs must be reduced to be mechanically stable. On the other hand, because the ferrite PM has a relatively low coercive force compared with the Nd PM, an irreversible demagnetization of the ferrite PM of the HSML IPMSM is likely to occur. Therefore, the mechanical stability and irreversible demagnetization must be considered at all design steps. As the irreversible demagnetization and mechanical stability can be confirmed only by the finite-element analysis (FEA), the proposed method in this article is a design method that considers the irreversible demagnetization and mechanical characteristics at all design steps using the FEA. After the design of the traction motor is completed using this design method, the designed motor is manufactured. To verify the validity of the design method, experiments are conducted on the manufactured motor, and the test results are compared with FEA results.

Design and Performance Assessment of a Small-Scale Ferrite-PM Flux Reversal Wind Generator

Currently, there is increasing research interest in harnessing wind energy for power generation by means of non-conventional electrical machines e.g., flux-reversal machines. The flux reversal machine is usually designed using scarce rare–earth permanent magnet material which may be unattractive in terms of machine cost. In this study, an attempt is made to re-design the flux reversal machine with non-rare-earth ferrite permanent magnet for wind energy applications. Because these machines possess high cogging torque, which results in vibration and noise, that are detrimental to the machine performance, especially at low speeds, a novel combined skewed and circumferential rotor pole pairing method is developed. The proposed cogging torque reduction method is implemented in 2-dimensional finite element analysis modeling and comparatively analyzed with other existing stand-alone methods viz., skewing, and rotor pole pairing. The results show that the proposed method led to 94.8% and 71% reduction in the cogging torque and torque ripple compared to the reference generator, respectively. However, the calculated torque density is reduced by 13%. Overall, the electromagnetic performance of the proposed ferrite PM machine exhibits desirable qualities as an alternative design for the direct drive wind generator.

Low-cost high-performance ferrite permanent magnet machines in EV applications: A comprehensive review

Abstract Ferrite-based permanent magnet (PM) machines have been developed for many applications due to their highly desirable features such as low costs and stable supply chain. More recently, partly driven by the rapid uptake of the electric vehicle (EV) market, and partly due to the uncertainty of the supply chain of the rare-earth metals that are key components of the EV traction motor, there have been considerable interests in developing alternative solutions to rare-earth based PM motors. Due to their intrinsic low magnetic flux and prone to demagnetization, ferrite PM motors have not been previously considered for the more stringent EV applications. Hence, there is a growing body of research studies in addressing these challenges by deploying novel design strategies with varying proportions of ferrite materials, and with varying degrees of success. To date, there is a lack of comprehensive literature review of this class of evolving and yet highly promising electric machines that will offer a viable and sustainable alternative to EV traction applications. This paper aims to fill this gap and to provide a dedicated overview of these machines with a focus on their credentials as the ‘traction motor of choice’ in future EV markets.

Electromagnetic Characteristic Analysis of High-Speed Motors With Rare-Earth and Ferrite Permanent Magnets Considering Current Harmonics

In general, permanent magnet (PM) motors are driven by a pulsewidth modulation (PWM) voltage source inverter for vector control. The generated PWM signals cause high-frequency voltage components at the carrier frequency. Such components can increase the electromagnetic losses, thereby necessitating the consideration of the phase current corresponding to the carrier harmonics. This study aims to examine the feasibility of high-speed PM motors in which rare-earth magnets are replaced with ferrite magnets, by considering the current harmonics. The electromagnetic characteristics of a high-speed motor with rare-earth and ferrite PMs were analyzed considering the current harmonics. Based on the existing rare-earth magnet model, a ferrite magnet model with the same performance was developed to perform a comparative analysis. The findings were validated via comparison with the experimental results of the manufactured models.

Comparative study of concentrated flux synchronous motor and multi‐layer IPMSM for traction drives using non‐rare earth permanent magnet

The rare earth permanent magnet (PM) is widely used for traction motors of hybrid and electric vehicles. These motors have more torque density compared to any other type of motors. However, these PMs have the problems of limited reserves, unstable supply, and high cost. For solving these problems, concentrated flux synchronous motor (CFSM) and multi-layer interior permanent magnet synchronous motor (IPMSM), using ferrite PMs, are compared in this study. The CFSM and multi-layer IPMSM are introduced and compared with regard to shape, size, electric parameter, and motor characteristics. In addition, two types of motors are fabricated and tested in order to verify their performance and feasibility. Finally, comparing the merits and demerits, the comparative motor types are estimated in this study.

Detection of Partial Demagnetization Faults in Five-Phase Permanent Magnet Assisted Synchronous Reluctance Machines

This paper analyzes partial demagnetization faults in a five-phase permanent magnet assisted synchronous reluctance motor (fPMa-SynRM) incorporating ferrite permanent magnets (PMs). These faults are relevant because of the application of field weakening, or due to high operating temperatures or short circuit currents, the PMs can become irreversibly demagnetized, thus affecting the performance and safe operation of the machine. This paper proposes fault indicators to detect such fault modes with low demagnetization levels between 5.0% to 16.7% relative demagnetization. Four partial demagnetization fault detection methods are tested, which are based on the analysis of the harmonic content of the electromotive force (EMF) under no load conditions, the harmonic content of the line currents, the harmonic content of the zero-sequence voltage component (ZSVC) and the analysis of the power factor (PF). This work also compares the sensitivity and performance of the proposed detection methods. According to the fault indicators proposed in this paper, the results show that the analysis of the EMF, ZSVC and PF are the most sensitive detection methods. Experimental results are presented to validate finite element analysis (FEA) simulations.

3kW급 풍력발전기용 페라이트 스포크 회전자 형상 특성비교

Most of the generators and electric motors developed in recent years are synchronous machines using permanent magnets of rare earth. As the name suggests, rare earth permanent magnets are expensive because they have a small amount distributed on the earth. In addition, the price fluctuation is large because it is concentrated and mined in a specific region. Therefore, in recent years, research has been actively conducted on developing a generator using a low cost ferrite permanent magnet for stable supply and reduction of the price of the generator. Ferrite magnet has a low magnetic flux density compared to a rare earth permanent magnet, so a large amount of permanent magnet must be used. In particular, the generator rotor is made in the form of a spoke to insert a large amount of permanent magnets. There are three typical spoke type types. This paper compare three types of characteristics at the same size and the same output.

A comparative study of BaxSr1−xFe12O19 ferrite permanent magnets prepared by ball milling and sol–gel routes

Given the huge and increasing global demand for permanent magnet supply, even slight improvements of the magnetic properties and cost effectiveness of permanent magnet materials could incur huge energy and money savings. This article is concerned with the optimization of the experimental conditions for the production of pure M-type BaxSr1−xFe12O19 hexaferrites with improved magnetic properties. X-ray diffraction analysis revealed the formation of a single M-type hexaferrite in the ball milling route at a sintering temperature of 1100 °C for the samples with x = 0.0 and 0.5, and at 1200 °C for x = 1.0. In the sol–gel route, however, a single M-type phase was successfully synthesized at a significantly lower temperature of 890 °C. The magnetic parameters of the samples prepared by ball milling exhibited an improvement at lower Ba contents. On the other hand, the samples prepared by sol–gel method exhibited a significant improvement of the intrinsic coercivity (HcM) compared with those prepared by ball milling, with the highest value of 5.9 kOe observed at x= 0.0 and sintering temperature of 1000 °C. The saturation and remnant magnetization, however, were not influenced significantly by the synthesis route, and remained relatively high, comparable with the best parameters for ferrite isotropic magnets. The sample with x = 1.0 prepared by sol–gel method and sintering at 890 °C exhibited the highest residual induction Br = 2509 G, practical coercivity HcB = 1919 Oe, and maximum energy product (BH)max = 9.9 kJ m−3.

Rotor Conductor Arrangement Designs of High-Efficiency Direct-on-Line Synchronous Reluctance Motors for Metal Industry Applications

To meet different loading requirements in the metal industry, special attention must be paid to the operational performances and start-up characteristics of those electric motors implemented for desired driven applications. However, because of the global warming and energy conservation concerns, the enforced operational regulations have increased the complexity of those commonly applied induction motors for supplying the desired equipment driven forces. By adopting the same stator, the synchronous reluctance motor (SynRM) can be achieved with properly redesigned rotor structure of an induction motor. Due to its robust structure and lack of secondary copper loss, it is very competitive for the related hoist, punch, roller, and pump applications. Furthermore, by inserting adequate ferrite permanent magnets and conductors into the rotor barriers, composition designs of the direct-on-line SynRMs (DOL_SynRMs) will also be proposed. The operational characteristics of the DOL_SynRMs for fulfilling different specifications will all be thoroughly investigated and confirmed by experimental measurements. The DOL_SynRM structures that can provide potential alternatives for related high-efficiency metal industry-driven applications can thus be validated.

Magnetic performance enhancement in La-Ca-Co doped SrFe12O19 ferrite permanent magnets via cold isostatic pressing

The crystallographic alignment, microstructure and magnetic properties were studied for La0.6Ca0.6Sr0.1Fe12.4Co0.4O19 ferrite permanent magnets prepared with standard ceramic method. The effect of cold isostatic pressing (CIP) and sintering temperature on the structural and magnetic properties of the magnets were investigated. The CIP significantly improves the density of the green compact and final magnets, but undermines the crystallographic alignment of the magnets simultaneously. As a result, the remanence of the magnet achieves optimal value under the compromise between the increased density and the degraded alignment. Moreover, the coercivity of the magnet increases linearly with the increment of the CIP pressure due the fact that CIP processed samples bear more uniform and finer grains in favor of high coercivity. Under optimal CIP pressure and sintering temperature, the magnet obtains best magnetic properties of Br of 0.439 T, Hcj of 396 kA m−1, Hcb of 311 kA m−1, and (BH)maxof 35.8 kJ m−3.

Outer Ferrite-PM-Rotor BLAC Motor Characterization: FEM-Assisted Optimal Design and Preliminary Experiments

This article is dedicated to design a Ferrite-PM outer rotor-synchronous machine for home appliances. The target requirement is to maximize efficiency at 4500 r/min and 1 kW. A 9 stator teeth/8 rotor poles configuration topology with rotor surface Ferrite PM is chosen for the investigation. To meet this requirement, a novel optimal design procedure employing the Hooke Jeeves algorithm and an analytical model of the BLAC machine is used. The novelty consists in using FEA-based online corrections of the analytical model, embedded in the optimization process to improve accuracy of the analytical model and reduce the computation effort. Further, finite element analysis of the optimization results is presented and compared with experimental results on a built prototype.

Ferrite PM Optimization of SPM BLDC Motor for Oil-Pump Applications According to Magnetization Direction

This paper proposes optimizing the magnetization direction of isotropic ferrite permanent magnets (Fe-PM) to enable the maximization of back-electromotive force (B-EMF), torque density, and minimum torque ripple of surface permanent magnet brushless direct current motor. The concept design is divided into two steps. First, two general Fe-PM electric oil pump motor models with radial and parallel magnetization are selected and compared with the neodymium permanent magnet models. Secondly, a finite element method (FEM) analysis is carried out with two different magnetization directions for each of the models in open-circuit and load operation. For more accurate results, the effects of no-load B-EMF, magnetic field distribution, air-gap flux density, copper loss, and efficiency are investigated. Finally, the validity and superiority of the FEM design results are confirmed by manufacturing the prototype motor and performing an experiment.

Inductance Calculation and Torque Separation of a Unique Multi-Layer Spoke-type Interior Permanent Magnet Motor using the Frozen Permeability Method

Frozen permeability approach (FP) is employed to separate the average torque components (reluctance and permanent magnet torque) and for the inductance calculation for a Unique Ferrite Multi-Layer Spoke-type Interior Permanent Magnet Motor. Finite element analyses (FEA) models are built to provide many results help to offer more insight analysis. Three factors are taking in account to analyse their effects: permanent magnetism, armature currents of stator and angular rotor position. Also, different saturation levels are analysed, to reveal the influence of magnetic saturation and crosscoupling. These detailed analyses are providing valuable insights for permanent machine design and optimization.

Thermal Analysis and Temperature Distribution of Two-Layer and Spoke-Type Ferrite Interior Permanent Magnet Machine

The main requirements for a rotating electric machine are the torque/power density and the energy efficiency. Producing an efficient electric machine required not only studying and analysing the electromagnetic properties but also deeper thermal analysis. It has been found that attention to the thermal design can be improve the total machine performance. In this paper a thermal model of the two-layer and spoke-type ferrite interior permanent magnet (IPM) machines is developed. FEA models are built to run the thermal studies and temperature distribution of the machine under different operating conditions. A prototype machine is built and tested for the experimental validations of the FEA. A prototype machine is tested under various working conditions. The testing results validate analytical model and the FEA methods.

Ferrite Permanent Magnets in Electrical Machines: Opportunities and Challenges of a Non-Rare-Earth Alternative

Rare-earth permanent magnets (RE-PMs) are widely used in high-efficiency and high-torque density electrical machines. However, in recent years, the exclusive and unstable supply of rare-earth elements (REEs) is a major concern to substitute RE-based electrical machines by less or even no RE alternatives. Ferrite (Fe) PMs as the least expensive PMs show promising opportunities for designing low-cost non-RE electrical machines. This article reviews some relevant works on Fe-based machines, which generally have been conducted to replace RE-based machines. Fe-based machines, including PM brushless, PM-assisted synchronous reluctance, PM flux switching, and PM Vernier machines, are introduced and their main design challenges, such as low PM energy product and vulnerability to irreversible demagnetization, are addressed. In addition, a comparison of RE- and Fe-based machines reveals that when both cost and efficiency are the major concerns, Fe-based machines can be a good successor to RE-based machines.

동축 마그네틱 기어의 자석 재질에 따른 최적효율 설계 및 비교

Various studies have been conducted since magnetic gears can replace mechanical gears and the non-contact power transmission characteristics of magnetic gears have emerged. Recent studies use rare earth permanent magnets to represent the high power density of magnetic gears. However, the conductive properties of the rare earth permanent magnets resulted in a decrease in efficiency. Using the ferrite permanent magnets, which have no conductivity, were difficult to compete in size. This paper presents the basic design of magnetic gears using three permanent magnet (NdFeB, Nd-bonded, Ferrite) materials and shows the results of size, efficiency characteristics.

Low-Cost Interior Permanent Magnet Machine With Multiple Magnet Types

This article is a contribution to answer the following question: Is it possible to design a permanent magnet machine with the performance expected from rare-earth magnets but at a lower cost? Performance being understood as torque, size, efficiency, demagnetization, and temperature rise together. The question is addressed with a systematic exploration of different interior permanent magnet machine topologies mixing rare-earth and ferrite permanent magnets. The study starts from a production baseline, the Prius 2010 traction motor, with interior magnets placed in a single V pattern. It investigates various rotor designs, most specifically, single V and double V patterns as well as spoke configurations. The stator cross-section design and winding selection are fixed, providing a solid comparison basis from the point of view of machine cooling. For each rotor design, torque potential and machine material cost are assessed, the latter expressed as torque per dollar. A promising configuration was found based on a spoke pattern for which further modeling was performed to assess efficiency as well as mechanical strength and resistance to short circuits and to demagnetization. It reduces the rare-earth magnet volume by over 60%.