Study on the Effect of Magnetic Pole Clipping Angle on the Eddy Current Loss of Permanent Magnets in the Rotor of Magnetically Levitated Permanent Magnet Synchronous High-Speed Electric Spindles

Aiming at the problem of high temperature and even demagnetization failure of permanent magnet (PM) due to PM eddy current loss in PM synchronous high-speed motors, this paper proposes a technique to lessen PM eddy current loss by cutting the angle of PM poles to change the shape of PM structure. Firstly, an analysis is conducted on the mechanism of PM synchronous high-speed motor eddy current loss production, the theoretical analytical model of PM eddy current loss is deduced, and it is theoretically proved that the magnetic pole shaving angle can reduce PM eddy current loss. Then, a 25 KW surface-type PM synchronous high-speed motor as an object, using two-dimensional time-step finite element method (FEM) to model and analyze PM eddy current loss. The results show that the smaller the PM pole shaving angle, the less its eddy current loss will be, it is possible to minimize the pole shaving angle of eddy current loss by 9.8% compared to the unshaved angle. Finally, the temperature field of the PM is calculated using a finite element method, and the outcomes demonstrate that the maximum temperature of the PM with a magnetic pole shaving angle can be reduced by about 5% compared with the unshaved angle.

Gravity and magnetic anomalies field characteristics in the South China Sea and its application for interpretation of igneous rocks

Igneous rocks in the South China Sea have broad prospects for oil and gas exploration.Integrated geophysical methods are important approaches to study the distribution of igneous rocks and to determine and identify igneous rock bodies.Aimed at the characteristics of gravity and magnetic fields in the South China Sea,several potential field processing methods are preferentially selected.Reduction to the pole by variable inclinations in the area of low magnetic latitudes is used to perform reduction processing on magnetic anomalies.The preferential continuation method is used to separate gravity and magnetic anomalies and extract the gravity and magnetic anomaly information of igneous rocks in the shallow part of the South China Sea.The 3D spatial equivalent distribution of igneous rocks in South China Sea is illustrated by the 3 D correlation imaging of magnetic anomalies.Since the local anomaly boundaries are highlighted gravity and magnetic gradients,the distribution characters of different igneous rocks are roughly outlined by gravity and magnetic correlation analysis weighted by gradient.The results show the distribution of igneous rocks is controlled and influenced by deep crustal structure and faulting.

Non-destructive Measurement of Magnetic Properties of Claw Pole

The magnetic properties of the claw pole have a direct effect on the output power of a generator Many methods can be used to measure these magnetic properties,each with its own advantages,but an important shortcoming is that all are destructive.In this study,a new non-destructive method to measure the magnetic properties of claw pole was proposed and a corresponding testing set-up was designed.A finite-element model was constructed to simulate the measurement process.Results proved that the measured magnetization-like curves had good agreement with the trend of the input magnetic curves and the effect of the positioning error in the measuring process could be neglected.To further validate the new method,seven types of claw poles of different materials subjected to different heat-treatment processes were forged and tested by both the new method and the conventional ring-sample method.Compared with the latter,the new method showed better consistency,relatively higher accuracy,and much stronger stability of measurement results;however,its sensitivity needs to be improved.The effects of material compositions and heat-treatment parameters on the magnetic properties of the claw pole were briefly analyzed.

Vector transformation and reduction to the pole for regional magnetic data with variable field direction

The vector transformation and pole reduction from the total-field anomaly are signifi cant for the interpretation.We examined these industry-standard processing procedures in the Fourier domain.We propose a novel iteration algorithm for regional magnetic anomalies transformations to derive the vertical-component data from the total-field measurements with the variation in the core-fi eld direction over the region.Additionally,we use the same algorithm to convert the calculated vertical-component data into the corresponding data at the pole and realize the processing of diff erential reduction to the pole(DRTP).Unlike Arkani-Hamed’s DRTP method,the two types of iterative algorithms have the same forms,and DRTP is realized by implementing this algorithm twice.The synthetic model’s calculation results show that the method has high accuracy,and the fi eld data processing confi rms its practicality.

Reduction of Cogging Torque and Electromagnetic Vibration Based on Different Combination of Pole Arc Coefficient for Interior Permanent Magnet Synchronous Machine

Cogging torque and electromagnetic vibration are two important factors for evaluating permanent magnet synchronous machine(PMSM)and are key issues that must be considered and resolved in the design and manufacture of high-performance PMSM for electric vehicles.A fast and accurate magnetic field calculation model for interior permanent magnet synchronous machine(IPMSM)is proposed in this article.Based on the traditional magnetic potential permeance method,the stator cogging effect and complex boundary conditions of the IPMSM can be fully considered in this model,so as to realize the rapid calculation of equivalent magnetomotive force(MMF),air gap permeance,and other key electromagnetic properties.In this article,a 6-pole 36-slot IPMSM is taken as an example to establish its equivalent solution model,thereby the cogging torque is accurately calculated.And the validity of this model is verified by a variety of different magnetic pole structures,pole slot combinations machines,and prototype experiments.In addition,the improvement measure of the machine with different combination of pole arc coefficient is also studied based on this model.Cogging torque and electromagnetic vibration can be effectively weakened.Combined with the finite element model and multi-physics coupling model,the electromagnetic characteristics and vibration performance of this machine are comprehensively compared and analyzed.The analysis results have well verified its effectiveness.It can be extended to other structures or types of PMSM and has very important practical value and research significance.

Analytical Signal and Reduction to Pole Interpretation of Total Magnetic Field Data at Eppawala Phosphate Deposit

A magnetic survey was carried out to find out the possibilities of demarcating a phosphate deposit from the surrounding country rocks. It is a well-established fact that the magnetic mapping can be utilised to investigate the subsurface objects, materials or different rock types based on their magnetic properties. Those rocks with ferro-magnetic minerals such as magnetite generate magnetic anomalies which in turn help to investigate the subsurface occurrence of mineral deposits. An economic phosphate deposit in Sri Lanka, known as Eppawala Phosphate deposit was selected for this study. The deposit was formed as an accumulation of secondary products of an apatite-rich carbonatite. Due to weathering of iron-rich carbonatite, magnetite and its derivatives are intimately bound with the said deposit. Therefore, the magnetic signature of the phosphate body is different to that of the surrounding country rocks. Despite some studies on different aspects of the deposit, subsurface extents of the ore body are so far not adequately studied. Therefore, this study was conducted to identify the boundaries of the phosphate body. The study was carried over an area of 12 km2 5 km north from the current mining site and survey was conducted. GSM-19 Overhouser system with integrated GPS was used to collect field data. Magnetic anomalies were plotted using a predefined grid. The maximum positive and negative anomalies encountered in the survey area are 690 nT and 829 nT respectively. This study showed that magnetite is not distributed evenly in the area and the deposit extended along the north south direction. Further, processing of analytical signal using the anomalies showed that the carbonatite occurs as a continuous body trending in North South direction. Low magnetic latitudes magnetic data interpretation is difficult because the vector nature of the magnetic field. Therefore, “reduction to pole” concept and “analytical signal concept” were used for the data analysis. Reduction to pole map and analytical signal map are comparatively similar and the change of declination value has no significant effect on the map of reduction to pole.

SUB-NANOMETER POLISHING OF MAGNETIC RIGID DISK HEADS TO AVOID POLE TIP RECESSION

For the purpose of solving the problem that too large pole tip recession （PTR） is produced in magnetic rigid disk heads by mechanical polishing, a chemical mechanical nano-grinding experiment is performed by using a float-piece polisher with a tin plate to achieve a more plane and smoother surface. A basal solution, addition agents and a range of pH value are suitably selected to find a kind of slurry, with which the PTR can be controlled on sub-nanometer scale and the giant magnetic resistance （GMR） corrosion and electrostatic damage （ESD） can be avoided. Moreover, the cause that TiC protrudes from the substrate surface of the heads is studied. The appropriate shape and size of diamond abrasive are selected according to the chemical activation of A1203 and TiC in the same slurry. In this way, the chemical and mechanical interactions are optimized and the optimal surface that has small PTR and TiC asperity is achieved. Ultimatily, the chemical mechanical nano-grinding in combination with mechanical nano-grinding is adopted. Sub-nanometer PTR is achieved and the TiC asperity is eliminated by the chemical mechanical nano-grinding with large size ofmonocrystalline followed by mechanical nano-grinding with smalle polycrystalline diamonds.

Influence of Inner/Outer Stator Pole Ratio and Relative Position on Electromagnetic Performance of Partitioned Stator Switched Flux Permanent Magnet Machines

Based on the 6-pole outer stator(armature winding-stator),the influence of inner(permanent magnet-stator)/outer stator pole ratio n(n=NIS/NOS),stator relative positions and rotor pole number combinations on electromagnetic performance of partitioned stator switched flux permanent magnet(PM)machines(PS-SFPMMs)is investigated in this paper.Since the armature windings and PMs are located in two separated stators and PMs are stationary,PS-SFPMMs have high fault tolerance capabilities.To maximize the torque performance,the PM of inner stator pole should be aligned with outer stator pole when n is odd while the iron rib of inner stator pole should be aligned with outer stator pole when n is even.No matter what n is selected,the rotor pole number NR can be any integers except the phase number and its multiples.The analysis results indicate that the optimal NR is closed to(NIS+NOS)/2 and it is odd when n is odd while it is even when n is even.Meanwhile,symmetrical phase back-EMF waveform will be obtained when the ratio of Min(NOS,NIS)to the greatest common divisor of Min(NOS,NIS)and NR is even.Based on the optimal rotor pole numbers for 6-pole outer stator with different n and corresponding optimal relative position together with same rated copper loss,the average torque is improved by 18.4%,25.1%and 25.7%respectively in PS-SFPMMs with n equal to 2,3 and 4 when compared with PS-SFPMM with n equal to 1.The analyses are validated by experiment results of the prototype machine.

ANALYSIS ON THERAPEUTIC EFFECTS OF 46 CASES OF PERIARTHRITIS OF SHOULDER TREATED BY NEEDLING JIANSANZHEN WITH MAGNETIC POLE NEEDLE AND MASSAGE

In the present paper,46 cases of periarthritis of shoulder were treated by needlingthe Jiansanzhen with magnetic pole needle and massage. Among them,43 cases were cured, ac-counting for 93. 48% and 46 were effective. The total effective rate was 100%. In control groupI there were 23 cases, who received treatment of acupuncture with traditional stainless-steel fili-form needle and massage, the total effective rate was 91. 3%. Comparison of the therapeutic ef-fects between the two groups showed X^2=4. 12, P【0.05. In control group II there were 23 cas-es, who received needling Tiaokou point (ST 38)-through-Chengshan (BL 57) with the abovementioned stainless-steel filiform, one of ancient and modern experimental methods, the total ef-fecive rate was 82. 6%, which was compared with that in the treatment group, indicating X^2=8.492, P【0. 01. It is suggested that the therapeutic effect in the treatment group was superior tothat in the control group I and significantly superior to that in the control group II.

Magnetic field of mathematical modeling and simulation of 3D magnetic pole array spherical actuator

In this paper a new spherical actuator is designed and its advantages are compared to an existing spherical actuator, which function is limited by several design bottlenecks. First the output torque is too small. Second, the attitude is difficult to be accurately detected. The new three-dimen- sional magnetic pole array can solve these major problems. The new actuator features an outer rotor with multiple permanent magnet （PM） poles. Using an analytical solution and the finite element so- lution simulation, the feasibility of the approach is verified. A prototype was developed, tested, and experiments were conducted to obtain the practical value of the magnetic flux density.

Thermoelectric Currents of Earth’s Core Generate the Earth’s Magnetic Field

The geotemperature gradient is considered as taking main part in generating the Earth’s magnetic field. It is shown that geotemperature gradient functions as a generator of both nuclear and mantle thermoelectrical currents thanks to the great temperature difference between the core and the mantle. The movement of those currents is close to the radial direction towards the Earth’s crust. However, the nuclear thermocurrents movement tends to cyclically change into opposite one. If the mantle and core thermocurrents move oppositely, the Earth’s crust cools down globally and ice age comes, but if they move unidirectionally then global warming comes. The calculation show that the Earth’s surface can warm up to not more than 10°C. The latter, considering how human factor affects the warming of Earth, is incomparably great. There are calculations that show power of the Earth’s thermocurrents being enough to generate and maintain the Earth’s magnetic field, its modern dynamics and the poles inversion.

Development and Analysis of the Magnetic Circuit on Double-Radial Permanent Magnet and Salient-Pole Electromagnetic Hybrid Excitation Generator for Vehicles

With the improvement of vehicles electrical equipment, the existing silicon rectification generator and permanent magnet generator cannot meet the requirement of the electric power consumption of the modern vehicles electrical equipment. It is di cult to adjust the air gap magnetic field of the permanent magnet generator. Consequently, the output voltage is not stable. The silicon rectifying generator has the problems of low e ciency and high failure rate.In order to solve these problems, a new type of hybrid excitation generator is developed in this paper. The developed hybrid excitation generator has a double-radial permanent magnet, a salient-pole electromagnetic combined rotor,and a fractional slot winding stator, where each rotor pole corresponds to 4.5 stator teeth. The equivalent magnetic circuit diagram of permanent magnet rotor and magnetic rotor is established. Magnetic field finite element analysis(FEA) software is used to conduct the modeling and simulation analysis on double-radial permanent magnet magnetic field, salient-pole electro-magnetic magnetic field and hybrid magnetic field. The magnetic flux density mold value diagram and vector diagram are obtained. The diagrams are used to verify the feasibility of this design. The designed electromagnetic coupling regulator controller can ensure the stable voltage export by changing the magnitude and direction of the excitation current to adjust the size of the air gap magnetic field. Therefore, the problem of output voltage instability in the wide speed range and wide load range of the hybrid excitation generator is solved.

基于永磁体间磁力作用的不倒杆

利用永磁体间的同极相斥作用,构造一个磁力势阱,设计制作高度可调、底部防滑的不倒杆装置。该装置抗干扰能力强、稳定性好,结构简单、设计巧妙,永磁体间磁力约束不需要外界提供电源,具有无接触控制、节能低成本等优势。

基于磁热耦合法的非对称混合磁极永磁电机热分析

针对传统内置永磁电机损耗高、发热量大的问题,提出非对称混合磁极永磁电机拓扑结构.介绍非对称混合磁极永磁电机的拓扑结构,对比分析两者的电磁特性与损耗分布特性.针对非对称混合磁极永磁电机分布式绕组的结构特点,对绕组进行等效处理,确定等效导热系数,建立集中参数热网络模型.建立单向磁热耦合模型,计算电机各部件的温度分布,验证了热网络模型的正确性.考虑到温度对永磁材料的影响,建立双向磁热耦合模型,对比分析不同电流密度对电机温升的影响规律.试制一台样机并搭建温升试验平台进行温升试验,验证了新型拓扑结构的有效性与合理性以及磁热双向耦合法计算结果的准确性.

梯形Halbach交替极无铁心永磁同步直线电机特性分析与优化设计

针对无铁心永磁同步直线电机(PMLSM)存在推力波动问题以及磁极结构对永磁体利用率的影响,从结构方面着手,提出一种梯形Halbach交替极磁极结构的无铁心永磁同步直线电机,对Halbach阵列进行优化设计。首先通过有限元法对比在Halbach交替极、双层Halbach磁极与梯形Halbach交替极3种磁极结构中PMLSM的电磁性能,分别对气隙磁场谐波成分、空载反电动势、电磁推力以及推力体积比进行计算与对比。其次,采用等效磁化强度法定性分析磁极结构对电机出力性能的影响,并引入Kriging模型,结合多目标优化算法对关键参数进行优化以提高电机平均推力和推力体积比,降低推力波动,得到3个优化目标的Pareto前沿。最后,通过仿真分析验证设计方法的有效性以及电机性能的改善。结果表明:梯形Halbach交替极磁极结构永磁体利用率更高,具有实用价值;梯形Halbach交替极PMLSM能够有效抑制推力波动并保持在7%左右,适用于高精确度加工设备。

基于磁链相移原理的不对称交替极永磁辅助同步磁阻电机设计与分析

传统永磁辅助同步磁阻电机(PMaSynRM)无法充分利用永磁转矩和磁阻转矩,该文提出一种新型不对称交替极永磁辅助同步磁阻电机(ACP-PMaSynRM)。基于永磁磁链相移原理,将交替极永磁阵列、不对称磁极和磁障相结合,实现永磁转矩和磁阻转矩的最大值在相同电流相位下叠加,不但提高了永磁转矩和磁阻转矩的利用率,增强了电机输出转矩能力,而且减少了永磁体用量。采用有限元法对比分析了传统和新型ACP-PMaSynRM的电磁性能,验证了所提电机拓扑的可行性。最后,制造了一台48槽14极样机并对其进行了实验验证。

四凸极液冷电磁缓速器数值模拟与实验研究

为解决中重型车辆长下坡时因主制动器频繁工作导致其制动效能严重衰退问题,提出一种四凸极液冷电磁缓速器结构。建立车辆下坡动力学模型分析制动需求,采用等效磁路法对其制动力矩进行计算,使用有限元法对其制动特性进行数值分析。利用分级变论域模糊控制策略结合缓速器进行车辆下坡时的制动控制,使用MATLAB/Simulink建立控制器和整车长下坡制动模型并进行联合仿真。设计了2100 N·m样机,通过台架实验和车载道路实验对样机制动特性进行测试,实际测量值与分析计算值基本一致,平均误差在5%内,在转速为1250 r/min时制动力矩可达2200 N·m,满足中重型车辆制动需求。

新型三段Halbach永磁阵列无铁芯AFPMG设计与分析

为解决传统Halbach永磁阵列无铁芯轴向磁通永磁发电机(AFPMG)由于磁极永磁体用量增加而导致功率密度降低的问题,提出了一种变辅助磁极参数(极角和充磁夹角)的新型三段Halbach永磁阵列无铁芯AFPMG.采用三维有限元法,对新型三段Halbach永磁阵列辅助磁极极角和充磁夹角进行了多目标优化设计,从而确定了最佳辅助磁极参数.最后对比了无铁芯AFPMG中采用不同磁极结构对发电机电压波形质量和功率密度的影响.结果表明:新型永磁发电机可以使发电机电压正弦波畸变率由2.40%下降为0.44%;相较传统两段Halbach和传统三段Halbach永磁阵列的无铁芯AFPMG,新型永磁发电机功率密度得到显著提高;新型永磁发电机的永磁体用量减少了16.68%,进而减轻了转子盘质量,使发电机更加适于低风速下稳定发电.

螺杆机用并轴双转子永磁电机齿槽力矩机理分析与抑制

针对并轴双转子永磁电机过大的齿槽力矩以及转矩脉动大等电磁问题,采用传统单个槽齿槽转矩理论以及双转子电机边端力矩波动理论进行分析,计算了并轴双转子电机齿槽力矩的特殊组成成分以及其各部分转矩的谐波阶次。分析改变磁极偏心距和转子斜极对电机齿槽力矩和转矩特性的影响。采用响应面法构建电机的多目标优化模型,通过改变永磁体偏心距和斜极块数来约束电机的优化变量,并采取约束关系以及优化目标求解出最优转子结构参数。构建有限元模型,验证齿槽力矩理论的正确性。对比采用最优转子结构参数下电机的电磁性能与优化前电机的电磁性能,优化后电机的齿槽力矩、转矩脉动等电磁性能进一步提升,验证了采用磁极偏心和转子斜极复合结构的有效性。

一种交替极永磁游标电机设计与分析

提出了一种使用低成本铁氧体磁体的交替极永磁游标电机(CPPMVM).介绍了该电机拓扑结构,提出了基于特定磁导函数的等效磁场模型来推导主磁密、调制磁密和反电动势.通过解析法和有限元法分析该电机电磁性能、气隙磁密和谐波分布.结果表明:与常规表贴式永磁游标电机(SPMVM)相比,所提出的交替极永磁游标电机机械结构简单、成本低、谐波调制作用有效、转矩密度高、抗退磁能力强.