Thermal Simulation of AC Electromagnetic Contactor

Transient magnetic circuit method is adopted to calculate the power loss in winding and shading coil. Based on the analysis of heat transfer process in AC contactor, a thermal model is proposed and the temperature field distribution is simulated with 3-D FEM of ANSYS. Comparison of simulation results with measurements shows that the proposed method is effective.

KEY TECHNOLOGY FOR PRACTICAL 1-mm-DIAMETER ELECTROMAGNETIC MICROMOTOR

A 1 mm diameter electromagnetic micromotor was developed as a crux component for MEMS application. The motor has a novel layer structure with a 1 mm diameter rotor in the middle of two stators with the same size. The stator uses multiple layers, slotless and concentrated planar winding. The rotor adopts multipolar permanent magnet with high performance. Ruby bearing is used to prolong operating lifetime of the micromotor. The stator winding, consisting of 6 layer coils, 42 turns, and 9 pairs, is fabricated with microprocessing techniques. The micromotor has long operation lifetime, its running speed is stable and controllable, and rotational direction can be easily reversed. Maximum achieved rotational speed of 18000 r/min with maximum output torque of 1.5 μ N·m has been obtained. This paper presented the key technology for developing this kind of micromotor including the design of structure, magnetic circuit, heat problem, friction improvement, microprocessing techniques, and so on.

Regulation and Control of Electromagnetic Field in Radio-Frequency Circuits and Systems

Since the first demonstrations of radio-frequency(RF)circuits,the physics of the electromagnetic(EM)field and its regulation and control with codesigned circuits,have become essential competencies of RF circuit designers.Leveraging advanced regulation or control methods,numerous high-performance circuits have been developed at RF and millimeter-wave(mm-wave)frequencies.Three main methods of electromagnetic regulation have been widely utilized,namely,the separation of electric and magnetic coupling paths,the manipulation of electromagnetic energy through the coupling of multiple tanks or multiple resonators,and the regulation of electromagnetic fields in air cavities or meta-substrates.The separated coupling paths of electric and magnetic fields provide guidance for designing a high-performance filter topology with a quasielliptical response through additional zeros.The manipulation of the EM field through electrical and magnetic intercouplings of multitanks or multiresonators,such as are used in oscillators,power amplifiers(PAs),etc.,results in remarkable power efficiency,size reduction,and wide bandwidth.The regulation of electromagnetism through an air cavity,patterned substrate,or metasubstrate reduces dielectric losses and size,especially when using a substrate integrated suspended line(SISL)platform.Many excellent circuits have been reported based on SISL with low loss,high integration,and self-packaging.Here,we present state-of-the-art cases that demonstrate the benefits of EM field regulation and control.

Dynamic characteristics of large permanent magnet direct‐drive generators considering electromagnetic–structural coupling effects

Dynamic characteristics of large permanent magnet direct‐drive generators(PMDGs)considering electromagnetic–structural coupling effects are analyzed in this study.Using the conformal mapping method,the scalar magnetic potential of the air gap magnetic field considering the slot effect is calculated.On the basis of the discrete current element and magnetic equivalent circuit model,the local magnetic saturation effect of the stator and rotor is quantitatively simulated and the air gap magnetic field intensity distribution is obtained via numerical simulation.A series of uniformly distributed equivalent electromagnetic springs are introduced to develop an electromagnetic–structural coupling finite element PMDG model.The proposed air gap field analysis method is verified by the finite element analysis results.On the basis of the test platform for the Goldwind 1.5MW PMDG,both modal and dynamic response tests for the stator/rotor coupling system are conducted,and the results are compared with the natural frequencies,mode shapes,and vibration responses obtained using the numerical model.The effects of the air gap length and rotor speed on the natural frequencies of the coupling system are analyzed.The proposed model has the potential to accurately evaluate the PMDG vibration energy,avoiding resonance points,and maintaining stable operations of the unit.

Numerical Simulation of Level Magnetic Field

According to Maxwell electromagnetic field theory and magnetic vector potential integral equation,a mathematical model of LMF(Level Magnetic Field)for EMBR(Electromagnetic brake)was proposed,and the reliable software for LMF calculation was developed.The distribution of magnetic flux density given by numerical simulation shows that the magnetic flux density is greater in the magnet and magnetic leakage is observed in the gap.The magnetic flux density is uniform in horizontal plane and a peak is observed in vertical plane.Furthermore,the effects of electromagnetic and structural parameters on magnetic flux density were discussed.The relationship between magnetic flux,electromagnetic parameters and structural parameters is obtained by dimensional analysis,simulation experiment and least square method.

Development and study on automatic balancer based on counter weight by magnetic force

Rotating machines are very sensitive to mass unbalance which has a harmful effect on its running accuracy and service life. Therefore,a variety of dynamic balancing methods and devices are studied to reduce the vibration caused by mass unbalance. On-line active balancing is a new balancing procedure which is more convenient and precise than the previous methods. In this paper,an electromagnetic balancer based on ring coils and permanent magnets is presented. The balancer has a simple structure and the self-locking function without clutch,and transfers power by the non-contact electromagnetic field. In order to justify the rationality of its design,a two-dimension(2D) electromagnetic finite element model is conducted to verify that this magnetic circuit has no flux leakage and saturation. A three-dimension (3D) 1/10 model of the balancer is built to obtain the self-locking torque and driving torque. Based on the research work above,an electromagnetic balancer is developed. By testing the balancer using COCO80,it is verified effective to reduce the rotor unbalance at the speed of 1300 r/min.

考虑精确磁通的电磁加载装置等效磁路建模

为提高电磁加载装置在控制应用时的模型预测快速性与精确性,考虑电磁加载装置硅钢片表面涡流磁场生成因素与不同轴偏心下有效气隙长度,采用非线性方程拟合硅钢片磁化曲线,建立包含磁极边缘效应、磁极铁心、转子硅钢片动态磁阻与涡流磁场的电磁加载装置非线性等效磁路模型。研究了硅钢片表面涡流磁场生成因素与气隙磁场分布,并与有限元仿真结果比较分析。应用该模型在水润滑轴承试验台上进行电磁加载力测试试验。研究结果表明:等效磁路法对磁场分布的表征与有限元法一致,且对气隙的计算更为精确;电磁加载力稳态误差小于4%,响应时间低于0.55 s。

开槽盘式磁力耦合器电磁转矩理论分析

对于开槽盘式磁力耦合器输出转矩的求解,提出了一种能够考虑磁路中各支路差异性以及相互作用的等效磁路法。导体转子采用的开槽形式,使得磁路中永磁体对应的气隙、导体和齿槽组成的支路并不相同,各支路的具体形式和内外转子相对位置有关;所提方法考虑各永磁体块所对应不同支路对电磁转矩的影响,并把整个磁路作为一个整体进行求解,考虑了各支路间的相互作用,提高了开槽盘式磁力耦合器输出转矩的计算精度。最后,利用所提方法对磁力耦合器不同滑差率、不同极弧系数和不同开槽比下的输出转矩进行了预测,并通过三维有限元分析和实验进行理论验证。经验证,所提方法能够满足工程应用的准确性要求。

磁路实验深度科教融合教学设计与实践

针对传统的磁路实验,创新设计了以螺线管式直动式电磁系统为核心的磁路实验,课堂中设计了仿真分析环节、网络App反馈与思考环节,搭建了源于实际科研项目的直流磁路系统,测试并验证了磁路系统理论与仿真分析结果;教师引导学生思考反电动势原理,在此基础上学生自主设计启发性实验并思考实践。教学设计加深了学生对磁路的理解,实践中深度融合了航天工程项目,激发了学生科研报国的热情。

磁感定义与复磁路相量分析

该文以变压器为例,分别建立并联和串联两种形式的等效正弦交变复磁路模型,相应地给出两种磁感的不同定义和物理意义,并比较各自的优劣势。首先,以相量图的形式分析不同负载性质等效复磁路中各物理量的相位关系,并在磁感定义的基础上完善磁路与电路的类比关系;其次,推导任意负载下等效电路有功和无功功率与类比复磁路中等效电路中虚拟有功和无功功率的数值关系;然后,以同步发电机为例,利用基于磁感的等效复磁路分析交流电机中定转子磁场的相互作用,分别基于等效复磁路和有限元方法分析一个变压器算例,验证理论分析的正确性;最后,给出研究结论,并据此客观地分析基于磁感的复磁路的作用。

筒式实心磁力耦合器的电磁转矩计算与传动特性

为计算筒式实心磁力耦合器(Drum-typeSolidMagneticCoupler,DSMC)的电磁转矩,研究其传动特性,以一台4对极DSMC为研究对象,建立了引入感应电流的等效磁路模型,结合安培环路定律并考虑三维端部效应,推导出耦合器的电磁转矩计算式;运用有限元仿真软件,得到耦合器的磁场分布和感应电流分布及不同输入转速下的机械特性曲线;通过轴向移动导体转子,改变两个转子的相对位置,得到不同啮合长度对电磁转矩的影响规律。最后,搭建试验平台对电磁转矩的理论计算及有限元仿真结果进行试验验证,所得试验结果与分析结果基本一致。该模型为DSMC的设计与优化提供了指导。

基于永磁直驱用电磁制动器的设计与研究

针对永磁直驱用电磁制动器制动力大、体积大、发热严重等问题,通过场路结合的方法,简化求解电磁吸力,运用Ansys有限元软件对电磁制动器进行场域求解分析,研究电磁制动器结构尺寸、气隙、绕组匝数、高压吸合时间、低压保持电压等参数对其性能的影响,并设计了一台220 kN的电磁制动器,通过样机的试验验证了计算和分析的正确性。

Analytical model and finite element computation of braking torque in electromagnetic retarder

An analytical model has been developed for analyzing the braking torque in electromagnetic retarder by flux tube and armature reaction method. The magnetic field distribution in air gap, the eddy current induced in the rotor and the braking torque are calculated by the developed model. Two-dimensional and three-dimensional finite element models for retarder have also been developed. Results from the analytical model are compared with those from finite element models. The validity of these three models is checked by the comparison of the theoretical predictions and the measurements from an experimental prototype. The influencing factors of braking torque have been studied.

弹射与阻拦一体式电磁弹射装置的电磁特性分析

针对线性弹射装置占地面积大、结构复杂和质量大的固有缺点,提出一种单轴一体式钢索拖动新型电磁弹射和阻拦装置。装置由永磁储能电机、电涡流离合器、电涡流制动器和绕线轮等组成。介绍了装置的结构和工作原理。基于安培环路定理建立电涡流离合器和电涡流制动器的电磁理论模型。通过与三维有限元计算结果对比,分析电涡流离合器和电涡流制动器的电磁特性。通过制作的电涡流制动器的小型试验样机验证电磁理论模型的正确性和有效性,最终进行动力学分析。研究结果表明,该装置可以使30000 kg的飞机在2.1 s内从0 m/s加速到70 m/s,并能够使72 m/s的飞机在2.6 s停下,满足设计指标的要求。

ECRIT等离子体特性数值模拟分析

针对航天器推进系统电子回旋共振离子推力器(ECRIT)电离效率易受放电室结构参数和工作参数影响,主要技术参数之间存在耦合不能单独优化的问题,文章采用多物理场仿真软件开展数值模拟,利用自适应函数细化电子回旋共振(ECR)区网格法提高仿真精度,探究不同磁路结构参数、工质气体、天线构型、微波功率对ECR推力器性能的影响规律,使电子在ECR区能够获得最大能量,经部分试验验证(微波输入功率和工质气体对放电影响),结果表明:磁环间距、内磁环-波导小端面距离和磁体高度对ECR区的分布影响较大,磁体宽度的影响较小;氙气的电子数密度高于氩气;L型天线电子密度和功率沉积高于杆天线;电子数密度和碰撞功率损耗随着入射微波功率增大而增大,可为ECR推力器设计提供参考。

混合励磁式电涡流制退机电磁场与阻力特性分析

电涡流制退机具有无液体泄漏、无需密封、阻力稳定的优势。与目前应用较多的永磁式电涡流制退机相比,混合励磁式电涡流制退机采用线圈替代了一部分永磁体,对阻力特性的调节效果更好。对比了混合励磁式电涡流制退机2种可能的结构形式,然后根据磁路分析与初步计算选择出具有更好阻力性能的结构。针对该结构,利用等效磁路法计算气隙磁场,采用子域模型考虑感生涡流影响,建立了求解混合励磁式电涡流制退机阻力值的等效子域模型。根据某口径火炮反后坐要求,确定了制退机的主要尺寸参数,完成了混合励磁式电涡流制退机结构参数的前期设计,并通过数值计算对解析计算结果进行了验证。接着,针对某口径火炮发射时的工况建立仿真模型,以炮膛合力曲线和复进机力的后坐行程函数曲线作为条件输入,分析强冲击载荷下混合励磁式电涡流制退机的电磁阻尼力、后坐位移和后坐速度规律。最后,分析了不同气隙宽度与内筒的电导率对电磁阻尼力的影响,结果表明气隙宽度越小电磁阻尼力越大,同时过大的内筒电导率会导致电磁阻尼力呈现“马鞍”型。本文研究可为混合励磁式电涡流制退机的工程化应用提供理论基础。

强冲击载荷下电磁阻尼器磁阻尼力影响分析

永磁式电磁阻尼器具有无接触、无污染、结构简单和可靠性高等优点,将其应用在火炮制退机上具有广阔的发展前景,但火炮在发射后产生的强冲击载荷使得电磁阻尼器的加速度最高可达1200 m/s^(2),因此在强冲击载荷下磁阻尼力的影响亟需分析。为确保电磁阻尼器能够满足火炮制退机的使用要求,引入火炮后坐运动方程得到强冲击载荷下磁阻尼力的变化规律,同时利用解析模型和有限元模型对模型进行相互映证。对电磁阻尼器在后坐过程中产生的寄生效应如端部效应、磁性饱和与涡流去磁效应等进行分析,结果表明:在后坐过程中,端部效应使得端部区域磁场强度降低,从而降低磁阻尼力;磁性饱和使得涡流区域的面积增加,导致涡流去磁效应加强,使磁阻尼力曲线产生“马鞍”型效应。通过对磁阻尼力的影响进行分析,为后续电磁阻尼器的设计和优化研究提供参考。

双磁路旋转音圈电机电枢反应的抑制方法

旋转音圈电机具有体积小、精度高等优点,一直广泛运用于精密指向机构中。通电线圈引发电枢反应扰乱电机磁场分布,进而影响电机控制性能。本文研究旋转音圈电机电枢反应及其抑制方法,在电机控制模型中引入电枢反应影响系数,边磁轭开矩形口截断电枢反应干扰磁路,分析电机控制系统动态特性和稳态特性,确定最优开口参数,设计并制造样机。实验结果表明:该方法可将电机控制系统稳态误差降低近50%,有效抑制电枢反应,提高系统稳态性能。

永磁线性涡流制动的性能分析与试验研究

为弥补电磁涡流制动系统在重量和发热方面的不足,文中设计了一种永磁式线性涡流制动装置样机,基于等效磁路法推导制动力及吸力解析公式,并用于指导设计参数初始值的选取。通过有限元仿真,对比分析了永磁涡流制动与电磁涡流制动的制动力及吸力特性。搭建永磁涡流制动试验装置,测试不同速度、不同气隙的涡流制动特性,并与解析法及有限元法的计算结果进行对比和误差分析。结果表明:在与原电磁涡流制动装置长度相同的前提下,设计的永磁涡流制动装置样机可以达到与其相当的制动力水平,且在200~400 km/h区间永磁涡流制动力更稳定,吸力更低;解析计算和有限元仿真结果均与试验曲线变化趋势一致,有限元仿真精度更高;当气隙达到70 mm时,制动力和吸力均趋于0,此缓解高度与原电磁涡流制动装置的缓解高度一致。从制动力及吸力特性的角度分析,永磁线性涡流制动适合高速列车应用。

涡流制动特性试验的纵向端部效应研究

涡流制动台架试验是研究涡流制动特性的重要手段,当试验使用的磁极个数少于设计数量时,纵向端部效应对试验结果有显著影响,故应对纵向端部效应的产生机理及修正方法进行深入研究。文章设计不同磁极个数的试验方案,验证端部效应对制动力和动态吸力的影响。通过2-D有限元电磁仿真,获得涡流制动磁场、涡流密度及洛伦兹力的分布规律,分析端部效应的产生机理。计算不同速度下,各磁极产生的制动力,获得端部磁极对制动力的贡献度,进而推导出端部效应的修正公式。研究结果表明,端部效应对动态吸力的影响较小,对制动力的影响比较显著,因此只需对制动力进行修正;入端磁极的制动力与中间磁极几乎相同,出端磁极的制动力相对较小,且对制动力的贡献与速度近似线性相关;通过出端磁极贡献度函数修正制动力试验数据,修正结果与3-D有限元仿真制动力的相对误差显著减小。研究结果为涡流制动试验设计和试验数据处理提供参考,有利于掌握更准确的涡流制动特性,从而指导产品研究开发。