永磁同步电动机恒磁链控制特性分析

在永磁同步电机数学模型的基础上,根据电机全磁链ψ0和转子永磁体与定子交链的磁链ψf相等的原则,介绍了恒磁链控制法.并通过推导永磁同步电机电磁转矩与定子电流的数学方程,采用查表法建立电流与转矩的拟合关系,使用MATLAB仿真软件建立电机模型,并将恒磁链控制分别与id=0和最大转矩电流比(MTPA)控制方法做了详细对比.仿真结果表明,恒磁链控制法下系统的稳态误差仅有0.478%,稳定性很优秀,且调整时间分别比id=0控制和MTPA控制要快7.7%和27.6%,且功率因数为0.72,均高于id=0控制的0.62和最大转矩电流比控制的0.67.     

Performance improvement of permanent magnet machines by modular poles

Modular permanent magnet poles have recently been proposed to enhance the performance of permanent magnet machines and improve the exploitation of used magnet materials. An optimisation method for these poles is proposed for use in linear permanent magnet synchronous machines. The main objective of the optimisation is to select proper dimensions and material properties of modular permanent magnet poles to enhance the machine developed thrust. The optimisation is carried out based on a mathematical model of the machine obtained analytically. In particular, the developed thrust of linear permanent synchronous machines with modular poles is given by the model. Genetic algorithm is then employed to optimise pole parameters where the ratio of thrust ripples to average thrust is chosen as an objective function. Extensive investigations carried out by analytical and finite element methods confirm that substantial lower thrust ripples are produced with almost the same average thrust.     

Very low speed performance of active flux based sensorless control: interior permanent magnet synchronous motor vector control versus direct torque and flux control

This study is focused on very low speed performance comparison between two sensorless control systems based on the novel 'active flux' concept, that is, the current/voltage vector control versus direct torque and flux control (DTFC) for interior permanent magnet synchronous motor (IPMSM) drives with space vector modulation (SVM), without signal injection. The active flux, defined as the flux that multiplies iq current in the dq-model torque expression of all ac machines, is easily obtained from the stator-flux vector and has the rotor position orientation. Therefore notable simplification in the rotor position and speed estimation is obtained. For IPMSM, a stator-flux observer is employed based on combined current and voltage models, with speed-dependent smooth transition between them using a PI compensator of flux error. Comparative experimental results using both sensorless control systems are presented to verify the principles and to demonstrate the effectiveness of the active flux observer at very low speeds from 20 to 2 rpm (1-0.1 Hz).     

Determination of winding inductances in ferrite type permanent magnet electric machinery by finite elements

A key design factor in ferrite type permanent magnet machines is the accurate knowledge of the values of machine winding inductances during the design stage. In the present paper, a method which is based on perturbation of the energy stored in the magnetic field, and on numerical models of simulation of such permanent magnets is used in calculating machine inductances. The effect of change in the values of these winding inductances with magnet position throughout the cycle of operation of such machines is given. These inductances also include the apparent and incremental values, whose definition is directly related to the choice of apparent or incremental reluctivities in the energy perturbation process. Results of application of this method to the calculation of inductances in a 15 hp 6-pole ferrite type electronically operated permanent magnet machine are given. These calculated values of inductances are in good agreement with the measured values.     

烧结NdFeB永磁合金的腐蚀行为研究及进展

介绍了烧结NdFeB磁体的腐蚀机理和近年来NdFeB永磁材料防腐蚀研究的进展情况,着重评述了合金化法、防护涂层和放电等离子烧结NdFeB的特点及存在的问题,并提出了改进措施.     

Index of rotor losses in three-phase fractional-slot permanent magnet machines

The aim of here is to define an index of the rotor losses induced by the magnetomotive force (MMF) space harmonics in fractional-slot permanent magnet (PM) machines. Such an index facilitates a rapid discrimination of the various fractional-slot PM machines, based on the numbers of slots and poles. For the sake of generality, a simple model of the rotor losses is adopted to compute such an index of rotor losses. However, the index behaviour follows that of rotor losses computed by means of more complex models.     

Performance of electromagnet and permanent magnet quadrupoles with iron poles

The largest field that can be obtained at the pole tip of an iron core quadrupole is limited by saturation in the iron and by its excitation by either the current density in the coil or the remanent field of the permanent magnet material. An analytical model is used to find the saturation limited performance of quadrupoles with either electromagnet or permanent magnet excitation. The results are presented in a form that can be used to evaluate proposed magnet designs but, more significantly, show that the strength of the excitation has less of an effect on the pole tip field than the size of the magnet needed to achieve it and that saturation has more of an effect on the achievable field strength than excitation strength does.     

Microstructure and magnetic properties of the permanent magnet material FeAIC

The relationship between microstructure and magnetic properties of a series of permanent magnets based on the composition Fe₉₀Al₈C₂ (wt%) has been studied using X-ray diffractometry and transmission electron microscopy. We have used various fabrication methods, heat treatments and alloying elements in order to optimize the magnetic properties of these alloys and the properties obtained were found to compare favourably with commercially available cobalt steels.     

Hysteresis and baseline shift in permanent magnet stabilized MR/SALheads

Hysteresis and baseline shift in shielded permanent magnet stabilized MR/SAL playback heads are studied via a 3D micromagnetic simulation. The hysteretic behavior is examined by calculation of playback voltages and uniform field transfer curves. The overlap region between the MR/SAL layers and the permanent magnet is seen to have a strong effect on the stability of the device. The amount of hysteresis is studied versus the width of the overlap region and the off-track position of the head     

On pinning of superconducting flux lines by grain boundaries

A simple model is developed which describes the reduction of the mean free path of conduction electrons in metals near a grain boundary. This leads to a decrease of the self-energy of flux lines in a layer which is considerably thicker than the perturbed zone of the boundary itself. The model yields pinning forces which agree, within an order of magnitude, with recent measurements on niobium bicrystals, and with observed values of grain boundary pinning in Nb₃Sn.Work supported by FAPESP, proc. no. 78/1230, and by the Niobium Project of FTI, Lorena SP, Brazil.On sabbatical leave from Instituto de Física da Universidade Estadual de Campinas (UNICAMP).     

HDDR技术制备高性能稀土永磁磁粉研究

利用HDDR技术研究了NdFeCoBZrGa合金的磁性能.研究了HD处理温度对合金磁粉磁性能和DOA的影响规律;研究了DR处理温度对合金磁粉磁性能和DOA的影响规律;研究了合金成分对合金磁粉磁性能和DOA的影响规律.结果表明通过适当工艺的调整,成功制备出高性能、高各向异性粘结磁体磁粉.对于成分为Nd13FgbalCo17B6 5Zr01Ga10的合金,其磁性能达到iHc=817.6kA/m,Br=1.18T,(BH)max=244kJ/m3,其取向度DOA达到0.56.     

Statics and dynamics in the system of high-T c superconductor and permanent magnet

Equilibrium and small oscillations in the system of high-T _c superconductor (SC) and permanent magnet (PM) are considered. A phenomenological theory based on the observed magnetization curves for SC is given. The measured forces and oscillation frequencies in the system of YBa₂Cu₃O₇ superconductor and SmCo₅ permanent magnet are compared with the theoretical predictions. Conclusions are made as to the possible applications for studying the SC properties of materials.     

永磁调节式MR阻尼器试验研究及工程应用

设计制作了永磁调节式MR阻尼器，在专用加载试验台上对该阻尼器的力学性能进行了试验研究，分析了影响阻尼力的各种因素，对永磁式MR阻尼器和油阻尼器、橡胶阻尼器进行了拉索减振的现场对比试验研究。结果表明，所设计制作的永磁式MR阻尼器阻尼力可调范围大，比油阻尼器具有更好的温度稳定性和更大的耗能减振能力，能保证每根拉索取得最优的减振效果。该阻尼器巳成功应用于长沙洪山大桥，解决了该桥严重的风致振动问题。     

Selection of the parameters of a permanent magnet synchronous machine by using nonlinear optimisation

The selection of the parameters of a permanent magnet synchronous machine (PMSM) is analysed using nonlinear optimisation. The constraints of the optimisation can be set to take the control principle into account. Compared with previously presented analyses, constant flux-based control as well as an absolute maximum criterion where no constraints are made to the control principle is analysed. Moreover, the requirements of the application are easily incorporated into the presented optimisation as additional constraints. On the basis of the results, the parameters of the PMSM (permanent magnet's flux linkage and the direct and quadrature axis inductances) can be selected. The results show that when using a constant flux linkage-based control principle (e.g. direct-torque control) more torque can be obtained compared with minimum current vector control. After analysing the effect of different parameters, a design procedure is suggested and an interactive design programme is implemented with Matlab     

Fe—Ni—Co—Al—Cu—Ti永磁合金高温下析出行为的X射线小角散射研究

利用小角Ｘ射线散射技术研究了淬火态Ｆｅ－Ｎｉ－Ｃｏ－Ａｌ－Ｃｕ－Ｔｉ永磁合金在８００℃保温不同时间时析出相的尺寸和比表面积的变化。初步分析了固溶淬火中形成的析出相的形状。揭示了析出相保温过程中的长大规律。     

Energy calculation of a permanent magnet system by surface and fluxintegrals (the flux-mmf method)

Formulas are derived for the total magnetic energy of a system with no currents, linear soft magnetic materials, and linear permanent magnets that satisfy a zero curl condition involving their magnetization vector (zero equivalent volume current density). This class of magnets includes common parallel and radially magnetized NdFeB and ferrite magnets above the knee in their demagnetization curves. The formulas express the energy as a constant plus either an integral over the magnet surface of the magnetic vector potential or an integral through the magnet of the magnetic flux. The formulas provide theoretical foundation for the flux-magnetomotive force (mmf) method for calculating cogging torque of permanent magnet motors     

Calculation of metal plate fusion by a concentrated energy flux

A. A. Baikov Metallurgy Institute, Academy of Sciences of the USSR, Moscow. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 62, No. 3, pp. 480–485, March, 1992.