An Analytical Determination of Eddy-Current Losses in a Configuration With a Rotating Permanent Magnet

The paper presents a completely analytical method for determining the eddy currents in a cylindrical configuration. The configuration consists of a cylindrical permanent magnet rotating inside a conducting hollow cylinder (stator). The solution is obtained by solving a generalized form of the diffusion equation and applying the modified Bessel functions. The determination of the magnetic field in the air and in the stator, and the losses generated by the eddy currents, is completely analytical. The results are verified by finite-element software.     

Measurement and Modeling of Rotational Core Losses of Soft Magnetic Materials Used in Electrical Machines: A Review

In many situations, for example, in the cores of a rotating electrical machine and the T-joints of multiphase transformers, the magnetic flux varies with time in terms of both magnitude and direction, i.e., the local flux density vector rotates with varying magnitude and varying speed. Therefore, it is important that the magnetic properties of the core materials under various rotational magnetizations be properly investigated, modeled, and applied in the design and analysis of electromagnetic devices with rotational flux. Drawing from the huge amount of papers published by various researchers in the past century, this paper presents an extensive survey on the measurement and modeling of rotational core losses of soft magnetic materials used in electrical machines, particularly from the view of practical engineering application. The paper aims to provide a broad picture of the historical development of measuring techniques, measuring apparatus, and practical models of rotational core losses.     

Analytical Interpretation and Quantification of Rotational Losses in Stator Cores of Induction Motors

We propose an approach to allocate and delimit a region in which the rotational losses are of most importance in the stator core of induction motors. The delimitation is based on the analysis of points at which the minimum flux density is not null. The analysis of flux paths and values of flux density over a number of motors allows a model of flux density to be proposed for the chosen rotational region. We conducted the process by post-processing finite-element results. A comparison with bench test results shows that the approach can confine the effects of rotational losses within a region allocated in the tooth roots without significant loss of accuracy. We give analytical expressions based on geometrical data. The approach provides a quick method to evaluate the rotational losses by analytical means, bypassing the use of numerical methods at those design stages at which is preferable to reduce the accuracy in favor of computational speed.     

Analytical Solution for Rotor Eddy-Current Losses in a Slotless Permanent-Magnet Motor: The Case of Current Sheet Excitation

We present an analytical solution for the magnetic field, induced eddy currents, and the corresponding losses generated in the rotor of a slotless permanent-magnet (PM) motor. The field excitation is a current sheet placed at the stator interior surface. The solution is based on an analytical solution of the diffusion equation using double Fourier series and in the complex domain. The first and the second Fourier series correspond to the time and space harmonics, respectively. We have analyzed the effect of each time harmonic in detail, and verified the results with FEM software.     

Determination of Eddy-Current and Hysteresis Losses in the Magnetic Circuits of Electrical Machines

Measurement Techniques - We consider the problem of separation of the total losses in the electric steel of a magnetic circuit into two components: the losses caused by hysteresis and the losses...     

Effects of Armature Reaction on the Performance of a Claw Pole Motor With Soft Magnetic Composite Stator by Finite-Element Analysis

We investigated the effects of armature reaction on the performance of a three-phase three-stack claw pole motor with soft magnetic composite stator core by using three-dimensional finite-element analysis (FEA), which is an effective approach to accurately compute the parameters and performance such as the back electromotive force (EMF), core losses, and winding inductance at various saturation levels. The motor is rated as 500 W at 1800 rpm when the stator current is 4.1 A, driven by a sensorless brushless DC scheme. Because of the armature reaction, the back EMF produced by the rotor permanent magnets and the developed torque is reduced by about 3.3% at the rated load, and the core losses increase drastically by 41% from no-load to full-load. The winding inductance is computed with different loads at different rotor angles     

Development and Application of Rare Earth Permanent Magnet (REPM) Material in Electric Machines

With the development of permanent materials, the development and application of permanent material electric machine (REPM) have been more mature. At first the state of development and application of REPM electric machine is presented in this paper, many RMEM have been produced in volume such as the pilot exciter used for power set of large-scale thermal power station, the special RMEM synchronous motor for textile, the starter motor for automobile, the brushless permanent magnet DC motor for electric facilities, permanent magnet servomotor for numerical controlled machine tool, rare-earth torque motor, special micro-motor for automobile and so on. Secondly the field of application of REPM electric machine and remaining problems is analyzed, because of the price of the rare-earth permanent magnet materials, the cost of RMEM is currently higher than that of induction machine, on the other side the dispersibility of performance of rare-earth permanent magnet materials and the limitation of technique of integral excitation are also remaining problems, above-mentioned problems handicapped the popularization of REPMEM. At last the developing prospect and trend of REPM electric machines is described, there are four promising types of PMEM: economical type, high performance type, high efficiency and energy-saving type, micromation, intelligibility type. With the appearance of new REPM material and the improvement of its performance and the continuous perfection of performance of electric-power electronic components, the development and the application of REPM electric machines will be further progressed.     

永磁同步电机抗干扰复合滑模控制器的设计

目的 在灌装、封口等包装作业过程中,提高永磁同步电机的快速响应和抗干扰能力,同时减少控制系统的抖振现象。方法 提出一种复合滑模控制策略,设计一种能适应滑模面和系统状态变化的分段速率滑模趋近律,将其与新型积分滑模面结合,设计一种带速度环的滑模控制器。同时,设计一个干扰观测器,用于估计闭环系统的扰动,并将估计后的扰动实时补偿到控制器的输出电流中,构建复合控制器。结果 仿真结果表明,设计的控制器能够显著提高收敛速度,并有效减少了控制系统的抖振,从而提高了动态质量。此外,干扰观测器与控制器结合的复合控制器可以提高系统的抗干扰能力,从而进一步提高了控制性能。结论 文中提出的复合滑模控制策略可以有效提高永磁同步电机调速系统的动态性能,减少控制系统的抖振,为实现高效、稳定的控制提供了有效的解决方案。     

General Properties of Low-frequency Power Losses in. Fe-based Nanocrystalline Soft Magnetic Alloys

1. IotroductlonAs early as 1969, it was reported that the dynamicloss at 50 Hi in the high-grade grain-oriented 3%SiFereaches about 75% of the practical measured total lossP and is much larger than the so--called classical eddycurrent loss Pc,l']; It was also observed that the total loss per cycle p/f nonlinearly increases with increasing frequency f in the low frequency range notmore than 100 Hi[1]. The above mentioned nonlineardependences have early been observed in many crystalline and am…     

氢对稀土-铁基永磁合金制备及性能的影响

本文评述了稀土永磁材料发展过程中，氢作为一种间隙原子在永磁材料的制备工艺上的应用；同时，作者还讨论了氢原子对几种主要稀土－铁基永磁合金磁性能的影响。     

铁砂中Si的含量对永磁铁氧体结晶形貌和磁性能的影响

用不同ＴＦｅ和ＳｉＯ２含量的精铁砂代替Ｆｅ２Ｏ３，制备永磁铁氧体，通过扫描电镜形貌观察和宏观磁性的测量分析，表明：当铁砂中的ＴＦｅ含≥７１．５％，ＳｉＯ２含量≤０．２４％，酸不溶物含量≤０．６％时，可用于生产高性能永磁铁氧体，其性能达Ｂｒ＝０．４２４Ｔ，Ｈｃ＝１９２ｋＡ／ｍ，（ＢＨ）ｍａｘ＝３１．２ｋＪ／ｍ＾３。     

The Systematic Error in Measuring the Normal Magnetic Induction Component at the Poles of a Permanent Magnet in Magnetooptic Topographic Recording

The systematic error is considered in measuring the normal component of the magnetic induction at the pole surfaces of a permanent magnet in the display of the magnetic field distribution by means of a film sensor based on a bismuth-bearing ferrite-garnet. A criterion is proposed for selecting film structures for use in magnetooptic detectors.     

软磁性薄膜微波磁特性的研究进展

概述了软磁性单层膜、多层膜、颗粒膜的微波磁特性研究进展,对这些薄膜的基本磁性和微波磁性进行了总结和讨论,得出软磁纳米晶薄膜可望成为应用于微波领域的主体候选材料,指出了Co(Fe)基软磁性薄膜微波特性的研究方向.     

Analysis of the Methods for Determining Losses in the Transformer Magnetic Core

Measurement Techniques - To effectively minimize magnetic losses and increase the efficiency of machines, particularly transformers, exact separation of total losses in the magnetic cores of...     

ANSYS软件在永磁同步发电机电磁场分析中的应用

本文主要介绍了ANSYS软件在永磁同步发电机电磁场分析中的应用过程并得出磁力线分布、磁感应强度B等结果,其结果有助于提高永磁电机进行性能分析及优化设计。     

Levitation Forces Acting on an HTS Sample in the Field of a Permanent Magnet

Journal of Superconductivity and Novel Magnetism - Using the Monte Carlo method, the vertical z-component of levitation force acting on a thin HTS film in a field simulating the inhomogeneous field...     

Coarsening of the Nanolamellar Structure in a Soft Magnetic Alloy

Crystallization from a cobalt base Co₆₅Si₁₅B ₁₄Fe₄Ni₂ amorphous magnetic alloy yielded an interesting highly modulated nanolamellar structure with lamellar spacing of about 5 nm. Coarsening of this structure was investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), convergent beam electron diffraction (CBED), and X-ray electron dispersive spectrum (XEDS) techniques and was found to initiate at grain boundaries, which provided nucleation sites for equilibrium phases. Rod-shaped Co₂B precipitates were observed along the nanolamellae; such precipitates also played a role in coarsening. A coarse lamellar structure subsequently developed which eventually broke up into equiaxed grains. A metastable Co₃Si phase was also observed to form by an allotropic transformation. The coarsening of the nanolamellar structure was found to occur largely by discontinuous coarsening processes. The crystallographic relationship between the equilibrium and metastable phases was determined     

Magnetic and Thermal Properties of HTS Bulk Magnet in the Pulsed-Field Magnetizing Process

In order to enhance the field-trapping ability of high T _c superconducting melt-textured bulk materials which act as quasi-permanent magnets when they capture the external magnetic fields, it is important to enhance the mechanical toughness of the materials to stand the stress induced by the magnetic repulsive force and thermal expansion. We adopted a dense Dy123-based bulk material with reduced void concentration in the experiment. Since the heat generations due to the flux motions in the samples results in the degradation of J _c, the time evolutions of the trapped magnetic fields and the temperature rises during and after the pulsed-field magnetizing processes were precisely measured at the same time to evaluate the penetrating flux motions and the heat generations in the sample. A single and couple of the magnetic pulsed fields with various intensities were successively applied to the sample at 30 K. The single magnetic field application exhibited a peak effect in the trapped-field behavior and tended to decline due to the heat generation. In the iterative pulsed-field application, the behaviors of the trapped fields and the temperature changes were found to be inverse between the first and the second pulsed-field applications. This implies that the flux penetration behavior into the sample magnet at the second field application is strongly restricted by the presence of former trapped fields which were formed by the first field applications.     

Comparison of the Unbalanced Magnetic Pull Mitigation by the Parallel Paths in the Stator and Rotor Windings

An eccentric rotor creates an electromagnetic force between the rotor and stator of an electrical machine. This force tends to further increase the rotor eccentricity and may severely degrade the performance of the machine, causing acoustic noise, vibration, excessive wear of bearing, rotor and stator rubbing, and so forth. Parallel connections are known to be a simple yet effective remedy for the problems associated with rotor eccentricity. We have investigated two common types of electrical machines running with eccentric rotors. We examined operation over a wide whirling frequency range. We numerically evaluated and compared the effects of parallel connections in the stator and rotor windings on the eccentricity force. We found that the parallel stator windings can be more effective in mitigating the unbalanced magnetic pull than the rotor cage (or damper winding), which normally has many more parallel circuits.