Kinds Of Permanent Magnets Research Articles

Research on Torque Ripple Optimization of Permanent Magnet Synchronous Motor for Electric Vehicle Based on Modular Poles

AbstractAbstract in order to study the torque ripple of permanent magnet synchronous motor for electric vehicle, the method of modular poles instead of single pole is adopted to reduce the torque ripple. The modular poles consist of three kinds of permanent magnets with different remanence and are arranged in a sinusoidal distribution. The pole arc length and position of each magnetic pole are calculated according to the cutting area of sinusoidal air gap flux density wave. By changing the cutting area of sinusoidal air gap flux density wave, the optimal pole arc coefficient of each permanent magnet was determined, and the magnet pole combination with the smallest torque ripple value is obtained. The results show that the sine degree of back electromotive force is improved obviously, the cogging torque is decreased greatly, and the motor with modular poles has obvious effect on torque ripple suppression. The torque of the motor with different kinds of magnetic pole combination is more stable than that of the motor with the same kind of magnetic pole combination. In this paper, the method of using modular poles instead of single pole to reduce torque ripple is of positive significance, which provides a reference for the subsequent performance optimization of electric vehicle motor. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Multi-Objective Optimization Design of a Multi-Permanent-Magnet Motor Considering Magnet Characteristic Variation Effects

In this article, a parallel-series magnetic circuit multi-permanent magnet (M-PM) motor is designed and optimized considering magnet characteristic variation effects, where two kinds of permanent magnets (PMs) are utilized as co-magnetic. Based on the equivalent magnetic circuit method, the detailed design method for the M-PM motor is illustrated. Considering the various operation conditions in potential electric vehicle applications, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B–H</i> curves of two PMs of different typical operation conditions are obtained. Then, a multiobjective optimization method is newly proposed which not only focuses on the magnet characteristics variation effect but also considers output torque, torque ripple as well as antidemagnetization capability under three typical operation conditions. The performances of the initial motor and optimal motor are compared under typical operation conditions. Finally, a prototype machine is built and tested. Both theoretical analysis and experimental results verify the validity of the motor and the proposed design optimization method.

Numerical Simulation and Experimental Validation of a Flux Switching Permanent Magnet Memory Machine

Compared with the traditional flux switching permanent magnet machine, flux switching permanent magnet memory (FSPMM) machine has two kinds of permanent magnets, flux regulating windings and complex flux path. In this article, a three phase FSPMM machine with 12 stator slots and 14 rotor poles is optimized by numerical simulation software. After the pole-arc optimization, there is only one suitable skewed slot degree of rotor that can further increases the sinusoidal degree of back electromotive-force (EMF) of FSPMM machine, and decreases the amplitude of EMF slightly. Besides, the flux regulating of FSPMM machine includes enhance flux is analyzed by numerical simulation software. Lastly, a prototype of FSPMM machine is constructed, and the obtained numerical simulation results are verified by experimental tests. The simulation and experimental results may be benefit for the research of operational control, flux regulation and industry application of FSPMM machine in future.

Comparison of End Effect in Series and Parallel Hybrid Permanent-Magnet Variable-Flux Memory Machines

Hybrid permanent-magnet (PM) variable-flux memory (VFM) machines employ both high coercive force PM, i.e., the constant PM (CPM), and low coercive force PM, i.e., the variable PM (VPM). The high energy-product CPM guarantees the benefits of high torque density of the conventional PM machines, while the PM magnetization state of the VPM is flexibly regulated to match various operation requirements. In fact, the two kinds of PMs can be magnetically connected in either parallel or series, with which the machine characteristics are quite different. In this paper, based on the two-dimensional and three-dimensional finite-element analyses, a pair of VFM machines with parallel and series connections, respectively, are investigated with specific reference to identify their difference in end effects. The comparison results show that the series hybrid PM VFM machine suffers more serious end leakage flux. The prototype machines are manufactured and tested to validate the analyses and predictions.

Comparative Study on Variable Flux Memory Machines With Parallel or Series Hybrid Magnets

Variable flux memory (VFM) permanent magnet (PM) machines exhibit an additional degree of freedom for control, i.e., PM magnetization state, and thus excellent flux controllability. Moreover, the hybrid PM topologies having variable PM (VPM) with low coercive force and constant PM (CPM) with high coercive force at the same time are employed to improve the torque density and the flux controllability. The parallel and series connections between the two different kinds of PMs are both feasible. Based on equivalent magnetic circuits, two-dimensional finite element analyses and experiments, the VFM machines with these two connection types are investigated and compared in this paper. The results reveal that the VPM with series-connected CPM is beneficial for more stable working point and higher torque density. A pair of VFM prototypes with parallel and series hybrid PMs are manufactured and tested to validate the analyses.

Analytical Performance Calculation of Vernier Hybrid Machine with Subdomain Method

The analytical subdomain models of vernier hybrid machines with two kinds of permanent magnet (PM) arrangements are developed, and the magnetic vector potentials are considered unknown variables to obtain the no-load and on-load magnetic field in this article. According to the electromagnetic properties and machine structure, the entire solving region is divided into five subdomains, namely the stator slot, slot opening, PM, air gap, and rotor slot. Using the general solutions of magnetic vector potentials and boundary conditions, the magnetic field distributions of all subdomains are obtained. Then the air gap flux density, flux linkage, back-EMF, cogging torque, electromagnetic torque, unbalanced magnetic pulls, and PM loss are calculated and compared for the two models. With the analytical model, the PM demagnetization withstand capacity, effects of main parameters on the torque ripple and average torque, and combinations of PM and rotor slot numbers are also studied. The 2D finite element method and experimental results of two prototype machines validate the accuracy of the analytical models.

Novel Dual-Stator Switched-Flux Memory Machines With Hybrid Magnets

In this paper, novel dual-stator switched-flux hybrid magnet machines (DS-SF-HMMMs) are proposed. Two sets of armature winding are employed so as to improve the space utilization and torque density. Meanwhile, two kinds of permanent magnets (PMs), i.e., neodymium–iron–boron and low-coercive-force magnets, are placed on either a common stator or separate stators. The proposed machines can provide the merits of high torque density in DS machines, and excellent flux adjusting capability in memory machines. The topologies and operating principle of the DS-SF-HMMMs having different PM arrangements are introduced and highlighted, respectively. In order to overcome the drawbacks of the original “U”-shaped PM type, two alternate designs are presented to increase the copper area in the inner stator and facilitate the manufacturability. In addition, the equivalent magnetic circuits for various machine models are formulated to reveal the field regulation principle. Then, the electromagnetic characteristics of various available DS-SF-HMMMs are evaluated and compared by the finite-element (FE) method. The stator/rotor pole combinations of the selected machine are analytically optimized in order to maximize the torque density. Finally, two prototypes are manufactured and tested to verify the FE analyses.

Analysis and Reduction of Unipolar Leakage Flux in Series Hybrid Permanent-Magnet Variable Flux Memory Machines

A series hybrid variable flux memory (VFM) machine employing two kinds of permanent magnets (PMs) on alternate rotor poles is investigated. This VFM machine features controllable PM flux and thus good flux-weakening capability, as well as improved torque density. However, it is found that the unipolar end leakage flux occurs if the two kinds of PMs are not balanced. According to the analyses of series connection between two PMs based on the fundamental magnetic circuit, the mechanism of the unbalanced rotor poles and the unipolar end leakage flux is revealed. Further, the rule of obtaining balanced poles is identified and the effects of operating conditions are presented. A series hybrid VFM machine prototype is fabricated and tested.

Design and Analysis of the Dimension of the PMs for the DMMSM using EMCM

The Dual-magnet memory synchronous motor (DMMSM) utilize two kinds of permanent magnets (PMs), namely the aluminum-nickel-cobalt (Al-Ni-Co) and neodymium-iron-boron (Nd-Fe-B) materials, to provide effective flux-mnemonic feature. The radially placed Nd-Fe-B PM provides main flux, and the tangentially placed Al-Ni-Co PM provides controllable flux. The tangentially placed Al-Ni-Co PM can be forward or backward magnetized by the d-axis current. The flux-control characteristic of the DMMSM affected by the size of the two kinds of PMs has been studied in-depth using the equivalent magnetic circuit method (EMCM) combined with the parallelogram hysteresis model (PHM). And finally, the finite element method (FEM) simulation is carried out to verify the validity of the proposed EMCM.

Novel High-Performance Switched Flux Hybrid Magnet Memory Machines With Reduced Rare-Earth Magnets

This paper proposes two high-performance switched flux hybrid magnet memory machines (SF-HMMMs) based on the design concepts of E-core and C-core SF permanent magnet (PM) machine topologies. Since two kinds of PMs (i.e., NdFeB and low coercive force magnets) are employed, the proposed machines can offer the merits of high torque capability, excellent flux adjustability, and high efficiency across a wide speed range. In this paper, the PM arrangement and dimensions, stator/rotor pole number combination, as well as the major design parameters are optimized first. Then, the electromagnetic characteristics of the proposed machines are investigated and compared with their conventional 12-stator pole SF-HMMM. It is found that compared with their conventional 12-stator pole counterpart, the proposed machines offer improved torque density and flux adjustability, even with the reduced PM usage. Finally, two machine prototypes are manufactured and tested to validate the analyses.

Performance Improvement of Partitioned Stator Switched Flux Memory Machines With Triple-Magnet Configuration

This paper presents a partitioned stator switched flux memory machine (PS-SFMM) with triple magnets to enable expedient flux control with reduced converter power rating. Meanwhile, the torque/magnet cost ratio of the machine has been significantly improved without much compromise of the torque capability. Three kinds of permanent magnets (PMs), NdFeB, SmCo, and AlNiCo, are hybridized, and hence the irreversible demagnetization of vulnerable AlNiCo PMs can be well prevented by SmCo magnets. The machine configurations with dual PM (DPM) and triple PM (TPM) are described first. Thereafter, the performance improvement mechanism is unveiled and addressed in the perspective of hysteresis curves as well as simplified magnetic circuits. In addition, the electromagnetic characteristics of the proposed machine with triple-magnet design are investigated and compared with those having DPMs. Finally, two PS-SFMM prototypes with DPM and TPM are manufactured and tested to verify the theoretical analyses.

Pole-Changing Flux-Weakening DC-Excited Dual-Memory Machines for Electric Vehicles

The dc-excited dual-memory machine utilizes two different kinds of permanent magnet (PM) materials for each PM pole. By employing a set of separately controlled magnetizing windings, it can easily realize the pole-changing function without affecting or changing the armature winding topology. In this paper, the principle of pole changing of the dc-excited dual-memory machine is analyzed by finite-element method. With the aim of preventing unexpected demagnetization of the low-coercivity PMs, a special scheme, namely the pole-protection scheme, is developed to shield these PMs. Experimental results are given to verify the pole-changing principle of the dc-excited dual-memory machine, and the feasibility of pole-dropping and pole-retrieving operations.

Thermal Analysis of the Permanent-Magnet Spherical Motor

There are many kinds of permanent-magnet (PM) motors, which are widely used in modern industry, but the problem of temperature rise is likely to affect the operation performance and even the life of the motor. The semiclosed structure of the PM spherical motor (PMSM) tends to increase the temperature when it works, so the thermal analysis of the PMSM is considered necessary. Based on double Fourier series decomposition, this paper establishes a three-dimensional (3-D) analytical model of PM eddy current loss in the PMSM, which considers the effect of time and space harmonics. Meanwhile, the heat sources such as hysteresis loss and copper loss are discussed. With those heat sources, a 3-D equivalent thermal network model is established. The thermal resistances are calculated. By applying the thermal network model, the influence of different speed and load on temperature rise is analyzed, and a steady-state thermal analysis of the motor is performed by using finite element analysis. The structure of stator is improved and good heat dissipation effect is achieved. This paper provides the theoretical basis for the design of ventilation and cooling system of the PMSM.

Multiobjective Sequential Design Optimization of PM-SMC Motors for Six Sigma Quality Manufacturing

In our previous work, two kinds of permanent magnet (PM) synchronous motors, transverse flux motor (TFM) and claw pole motor, were designed and fabricated using the soft magnetic composite (SMC) cores. This paper presents multiobjective and robust design optimization for high-quality manufacturing of these PM-SMC motors to improve their industrial applications. Meanwhile, an improved multiobjective sequential optimization method is presented to reduce the computation cost. Thereafter, a PM TFM with SMC core is investigated to illustrate the performance of the proposed method. From the discussion, it can be found that six sigma quality manufacturing was achieved for all Pareto design schemes given by the proposed method. Furthermore, manufacturing cost and computation cost have been reduced a lot.

Robust Design Optimization of PM-SMC Motors for Six Sigma Quality Manufacturing

In our previous work, soft magnetic composite (SMC) material was employed to design cores for two kinds of permanent magnet (PM) motors, namely transverse flux machine (TFM) and claw pole motor. Compared with motors designed by traditional silicon steel sheets, these motors require 3D flux design with new material and new manufacturing method. Meanwhile, the performances of these motors highly depend on the material and manufacturing parameters besides structure parameters. Therefore, we present a robust design optimization method for high quality manufacturing of these PM-SMC motors to improve their industrial applications. Thereafter, from the design analysis of a PM-SMC TFM, it can be found that the proposed method can significantly improve the manufacturing quality and reliability of the motor, and reduce the manufacturing cost.

Analysis of permanent magnet linear motor parameters taking its heating into account

Abstract The calculation results of the static field parameters for permanent magnet linear synchronous motor have been presented in this work. The influence of the construction temperature on the parameters has been analyzed mathematically. Models for magnetic and temperature fields determination have been formulated. Two kinds of permanent magnets (NdFeB and SmCo) have been considered. The distribution of the thermal field has been obtained using the finite element method (FEM).

Design and Analysis of Magnet Proportioning for Dual-Memory Machines

The dual-memory machine utilizes two kinds of permanent magnets (PMs), namely the aluminum-nickel-cobalt (Al-Ni-Co) and neodymium-iron-boron (Nd-Fe-B) materials, to provide effective flux-mnemonic feature. Namely, the Al-Ni-Co PM can be forward or backward magnetized in such a way that it can coordinate with the Nd-Fe-B PM to online tune the air-gap flux density. Based on the proposed DC-excited memory machine structure, the magnet proportioning between the Al-Ni-Co PM and the Nd-Fe-B PM is analysed. Both simulation and experimentation are carried out to verify the validity of the proposed dual-memory machine design.

Effect of γ-ray irradiation on the magnetic properties of NdFeB and Fe–Cr–Co permanent magnets

The effect of γ-ray irradiation on the magnetic properties of NdFeB and Fe–Cr–Co permanent magnets has been investigated. The magnetic flux loss of two kinds of magnets before and after irradiation was measured. Results show that the effect of γ-ray irradiation on the magnetic properties of sintered NdFeB is not so obvious as that on Fe–Cr–Co magnet. Irradiation-induced damage from γ-ray for the Fe–Cr–Co magnets was characterized for the first time. The decline of permanent magnetic properties of Fe–Cr–Co magnet induced by γ-ray irradiation is reversible except for the maximum energy product ( BH) max. The difference of coercivity mechanism between these two kinds of permanent magnets is responsible for the different dependence of magnetic properties loss induced by γ-ray irradiation.

Development of a hybrid helical microwiggler with four poles per period

A compact strong test hybrid helical microwiggler has been designed and developed with ten periods, each with length 10 mm and four poles, and gap diameter of 5 mm. One period is constructed with four segments. Each segment has a thickness of 2.5 mm and consists of pentagonal permanent magnets and permendur poles. Each segment is stacked along the wiggler axis and is rotated by an angle of 90/spl deg/ to the adjacent segment. The outer width is only 72 mm. The wiggler is divided into two sections where two kinds of permanent magnet - one with apex angle of 90/spl deg/ and one with 120/spl deg/ - were installed in order to find out the effect of geometrical size for the field. Peak fields of 0.360 and 0.381 T were achieved with small rms variations of about 1.1% and 0.6%, respectively, depending on the geometrical size of the permanent magnet.

Magnetic characteristics of oxide superconductors for the application of running systems with magnetic levitation

AbstractA model vehicle is constructed which runs without contact to its magnetic rail using oxide superconductors. This paper describes the forces acting between the superconductor and the rail for such a purpose. The attractive and repulsive forces were measured at 77 K as a function of distance between the superconducting pellet and the magnetic rail. As suprconducting pellets, three kinds of materials, i.e., MPMG‐Y123, BiPb2223, and Hg1223, were investigated for three kinds of permanent magnets, i.e., Nd‐Fe‐B, Sm‐Co and ferrite.