Industrial application of position sensorless active magnetic bearings

Active magnetic bearings (AMBs) are applied to turbomolecular pumps (TMPs) and milling spindles. However, their application areas are limited because they are costlier and require larger space than conventional mechanical bearings. Omitting position sensors from AMBs is one of the promising methods to solve such problems. An additional merit is that rotors can be shortened to have a higher critical speed by removing sensor targets from the rotor. The sensorless operation of AMBs has already been achieved in several instruments developed for experimental study. In this research, the sensorless magnetic suspension method is applied to a TMP manufactured as an industrial product, and it is demonstrated that sensorless AMBs can suspend a high-speed rotor.     

Electromagnetic analysis of inductrack magnetic levitation

A new type of magnetic levitation system called the Inductrack has been proposed by R. F. Post. This system is composed of a special arrangement of permanent magnets on board which is called the Halbach array, and a close‐packed array of shorted coils in the longitudinal direction on the ground. This composition can obtain a large magnetic force, a very low take‐off speed, and a high lift‐to‐drag ratio. This paper describes numerical simulations of the Inductrack magnetic levitation by the Fourier series analysis which is utilized in the analysis of superconducting magnetic levitation. By using numerical examples considering a full‐scale car model, we reveal the features of the Inductrack system in comparison with the superconducting magnetic levitation. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(1): 67–74, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10061     

The development of bi-based high-temperature superconductor and coil

Ag-sheathed Bi-2223 superconducting oxide conductors with a critical current density of 66,000 A/cm² at 77 K and coils that have generated magnetic fields of approximately 1.5 Tesla at 4.2 K have been successfully developed. The conductors consist of piled-up bundles of four to six sheets of element tapes with transport currents of approximately 200 Amps. The core size limit (CSL) prevented the production of single conductors that had the capacity to transport a current as high as 200 Amps at 4.2 K. Until now, it was difficult to develop a conductor having both high critical current density and the capability of transporting a large amount of current simultaneously. The role of CSL in large scale applications of high temperature superconducting oxides is discussed.     

Three‐dimensional array of strong magnetic field by using cubic permanent magnets

The strong magnetic field arrays by using cubic permanent magnets are proposed as a magnetic field source. The magnets used two types of the magnetized directions: 6 and 18 directions. The array is three‐dimensional structure: cube consisting of three, five, seven, and nine cubic magnets on the side. There are two types of the structures: through‐hole and dead end in the center. For each cube magnet, the magnetic flux density of the center was calculated by the derived formulae, which are solved the area integral by the integral formulae. It is a feature that the calculations are fast. The directions in which the magnetic flux density of the z‐axis is maximized were selected, and the sum of their magnetic flux density was obtained. At the same time, each sum of the magnetic flux density of the x‐axis and y‐axis was selected to be zero. It was found that the obtained results are independent of the length of one side. Therefore, the structures can also be combined to cover the structures. Although the operating point of the magnet is not taken into account, it was able to find the arrangements of more than 2 T. It was confirmed that the array of 24 cubes was consistent with the experiment.     

飞轮储能装置用轴向磁轴承及其低功耗策略

针对垂直放置的飞轮储能装置中磁轴承的低功耗要求,研究一种新型结构的永磁偏置轴向磁轴承,分析其结构和工作原理;采用等效磁路法推导出该型磁轴承的承载力、力/位移系数及力/电流系数的数学表达式;给出主要参数的设计方法,并设计原理样机,利用有限元软件对设计结果进行三维仿真分析.在此基础上,研究轴向气隙不对称的低功耗悬浮策略,理...     

采用新型磁性槽楔的永磁同步电机分析

针对磁性槽楔能够改善电机气隙磁导波形,减小气隙磁密谐波,削弱电机齿槽效应,从而减小电机损耗和转矩波动,提高电机效率的优异特性,提出一种新型的叠片式磁性槽楔。该结构能够进一步优化开口槽电机的气隙磁密波形,降低齿槽转矩,减小电机损耗,同时又不会影响电机定子槽漏抗。本文用解析法分析磁性槽楔磁导率对于气隙磁密谐波以及定子槽漏抗的影响,通过一台130kW的永磁同步电机模型,运用有限元仿真分析比较叠片式磁性槽楔与普通磁性槽楔的电气性能。     

Three‐dimensional vibration characteristics of the permanent magnet–HTSC magnetic bearing

The three‐dimensional vibration of the rotor in a permanent magnet– HTSC magnetic bearing system is studied. We have developed a magnetic bearing system which can revolve at up to 12,000 rpm, and three‐dimensional vibration of the rotor is measured with laser displacement sensors. To consider the rotor vibration in a mechanical resonance state, the static lateral and vertical pinning forces of the magnetic bearing are measured. The results are used to obtain the resonant frequency. There are two factors in the mechanical resonance caused by the magnetic bearing. One is the lateral equivalent spring coefficient and the other is the vertical equivalent spring coefficient. The influence of mechanical resonance caused by the lateral spring coefficient is large, and that of the vertical one is small. The three‐dimensional vibration of the rotor position around the mechanical resonant frequency is measured. Because the revolution of the rotor increases the lateral force to the center, the resonant frequency obtained in a free revolution experiment is larger than that obtained from pinning force measurement. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(3): 58–64, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20586     

盘式永磁电机定子固有频率的研究

本文介绍了一种新的解析法来计算盘式永磁电机定子的固有频率,通过实验证明了利用该解析法估算盘式永磁电机定子固有频率的可行性。通过实验,分析了定子开槽、端盖和绕组对定子固有频率的影响。最后得到一些结论,为盘式电机的模态研究打下基础。     

热处理工艺对半硬磁2J85合金结构和磁性能的影响

利用光学显微镜及电子显微镜对不同热处理阶段的磁棒进行金相组织观察,发现经过多级回火,强磁性相α1长大,弱磁性相α2的量相对减少。且两者相对比例不同所表现出的磁性能也不同。同时发现磁性能低的磁棒金相组织中存在白色析出物,推断为合金化学成分不均匀造成的,通过调整回火工艺及固溶处理工艺得出:1200℃保温30min固溶处理且采用5级回火工艺时能够使矫顽力稳定在17.90kA/m附近,完全满足客户的要求。     

径向两自由度永磁偏置磁轴承的研究

设计了一种新型径向两自由度永磁偏置混合磁轴承结构,介绍了这种轴承的结构特点和工作原理,对其磁场形态进行了分析,得出这种轴承的磁路不存在耦合的结论。并简单介绍了这种轴承的参数设计,在此基础上建立了完整的永磁偏置磁轴承系统,并进行了稳定的静态悬浮实验,由实验数据得出这种磁悬浮轴承可以显著降低功率损耗的结论。     

Suspension of soft magnetic materials using high Tc superconductors

This paper describes a novel suspension technique using high T_c superconductors and magnetic materials. It was found for a field-cooled superconductor and an adjacent magnetic material that the usual inverse relationship between the attractive magnetic force and gap distance reverts to a direct relationship for small gap length. Thus, stable, noncontact suspension is possible within a certain gap range. This phenomenon was found for even a soft magnetic material possessing minimal coercive force. Since remarkable reversals were observed for magnetic materials with diameters much smaller than that of the pinned area, it is considered that some of the pinned flux is subject to a gathering effect in the magnetic material. Stable, contactless suspension of a 180 g carbon steel weight under a high T_c superconductor was achieved using this technique.     

基于动态分析的永磁机构最佳设计参数的选择

开发了永磁机构动态分析软件,采用有限元法进行磁场计算,耦合机构运动和电路方程,仿真了机构及开关的动作特性并通过试验验证.提出了永磁机构中非工作气隙δ的概念,研究了δ,电容器容量,线圈参数以及供电方式对开关分合闸电流及速度的影响.本文从节能和缩小开关体积的观点出发,进行参数的优化选择.     

AMS磁体中各磁棒受力的计算

在大型磁体制造中,各单元磁块在磁场中受力的是磁体结构应力分析的基础,对于ＡＭＳ这样将要用于太空、投资巨大、影响深远的项目,为了保证所用磁体在使用及运输中的安全可靠,必须提供磁块受力折数据。本文采用麦克斯韦应力法,对ＡＭＳ磁体各磁棒在磁场中的受力进行了计算,实验结果证明了计算的准确性。     

Characteristics of axial force and rotating torque and their control of permanent magnet type axial gap self‐bearing motor

This paper introduces an axial gap type self‐bearing motor. It is intended for a disk type flat motor to have both functions of rotation and axial position control. This motor is simple in construction and requires a simple control system. A permanent magnet type motor is analyzed theoretically and tested experimentally. The torque characteristics of the tested motor are measured at various values of axial force and air gap. Independent control of the axial force and torque is introduced for the servo motor control and synchronous motor control. The results show the high possibility of the proposed motor and control system. © 2000 Scripta Technica, Electr Eng Jpn, 132(1): 81–91, 2000     

Improvement of sensing characteristics of self‐sensing active magnetic bearings

A winding‐current interference model of self‐sensing magnetic bearings (AMBs) and an improvement technique of position‐sensing characteristics are proposed. In the self‐sensing AMB systems, the electromagnets work not only as actuators suspending the rotor but also as position sensors. The self‐sensing position signal, however, includes errors because of nonlinearity of the magnetic circuits. In the proposed model, the current is directly transmitted to the self‐sensing position signal. This transmission means degradation of the self‐sensing characteristics. This winding‐current interference to the self‐sensing signal is reduced by the proposed compensation method. The characteristics of the proposed self‐sensing method agree well with a reference sensor signal up to over 1 kHz. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(2): 70– 77, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20732 Copyright © 2004 Wiley Periodicals, Inc.     

基于高频电压注入的永磁同步电机参数辨识方法

中大功率工业应用中,变频器到电机之间长电缆分布参数、变频器输出频率限制将直接影响高频注入法对电机参数辨识精度。考虑多种限制条件,提出了一种基于曲线拟合的定子电阻计算方法,研究了基于高频注入的永磁电机电感参数辨识方法,重点分析了不同注入信号选择对参数辨识精度的影响,为注入信号的选择提供了依据。通过实验证明了该方法的实用性与有效性,对工业应用电机参数辨识具有重要指导意义。     

永磁偏置磁轴承在线监测系统的研制

在永磁偏置磁轴承（PMB）电机高速旋转时，为了探测PMB转子的工作状态，并且判断PMB系统的运行是否正常，在线监测系统的研制是非常必要的。住线监测系统的构造是基于一台PC和虚拟仪器技术，由三部分组成：设计一个数据采集平台去采集PMB系统运行时那些必要的和有用的数据；对采集的数据进行时域、频域分析；将采集的数据进行在线存储，以便通过离线分析改进控制器的设计，确保PMB系统工作的可靠性。实验结果表明，系统工作可靠。     

Experimental study of a PM-HTSC hybrid magnetic levitation system

A principle of hybrid magnetic levitation system using permanent magnets (PMs) and high-temperature superconductors (HTSCs) for a linear-motor-type carrier system in a high-quality clean room and a magnetic bearing for the flywheel energy storage system are discussed. A substantial levitation force was generated by the repulsive force between like poles of coupled magnets. However, the repulsion system with magnets is essentially unstable without control. Thus, HTSCs are applied for control elements of the PM-HTSC hybrid magnetic levitation system. In this system, the levitation force becomes stronger than in the system without PM, and we can expect sandwich-type magnetic bearing capable of sustaining greater force.     

磁悬浮支承低功耗储能飞轮

储能飞轮由于其高储能密度、高寿命及高充放电次数而在能量储存系统中得到广泛重视。首先开发了以普通磁悬浮轴承支承、普通永磁无刷直流电机驱动和发电的FW-15A储能飞轮系统,用以验证高速磁悬浮支承系统的功能、制造安装,并分析储能飞轮系统的功耗。在FW-15A的基础上,开发出FW-15B系统,该储能飞轮系统侧重于降低功耗,采用新型永磁偏置径向和轴向磁轴承,采用杯形绕组永磁无刷直流电机。试验表明,在飞轮转子静止时,FW15-B和FW15-A的磁轴承功放输入功率分别为3.59W和29.6W;在25974r/min飞轮转速时,FW15-B和FW15-A的电机功放输入功率分别为10W和20W。     

Analysis and characteristics of a permanent magnet-type bearingless motor

Super-high-speed and high-power electric machines are required for turbomolecular pumps and spindle drives. High rotational speed and high-power drives can be achieved with bearingless motors. In this paper, a bearingless motor with principles of permanent magnet-type synchronous motors is proposed. High-power factor and high efficiency can be expected in permanent magnet-type bearingless motors. The proposed bearingless motor is a 4-pole permanent magnet synchronous motor, in which additional 2-pole windings are wound together with 4-pole motor windings in stator slots. With currents of 2-pole windings, radial magnetic forces are produced to support a rotor shaft. Principles of radial force production of surface-mounted permanent magnet bearingless motors are analyzed mathematically. The relationships between radial forces and the permanent magnet thickness were derived. From these relationships, the optimal permanent magnet thickness to produce radial forces efficiently is found. A test machine was built to confirm the relationships of radial forces, currents and voltages.