上期《想想看》答案

3.任何通电导体的周围都会产生磁场,因此将电缆线盘绕在焊机上,实质是给焊机绕组旁增加了一个线圈。当焊接时,这个通电线圈会产生一定强度的磁力线,形成一个磁场。它与焊机内的磁场(特别是感抗线圈产生的磁场)发生互相干扰,因此破坏了焊机原有的稳定特性,使用中会发生电压波动,电流不稳定的现象。另外,电缆线盘绕在焊机外壳上既影响焊机散热也     

能量天平电磁体系统非线性误差研究

在功率天平和能量天平实验中,当磁体由铁磁材料构成时,悬挂线圈通电后产生的磁场会引入非线性误差。功率天平法采用的永磁体系统,磁场较强,引入的非线性误差小于1×10-9。而在能量天平法中,电磁体系统产生的磁场较弱,同时存在闭磁路,磁路模型复杂,其非线性误差需要进一步研究。磁体的非线性误差主要与两个因素有关,一个是悬挂线圈电流大小,一个是磁轭在BH曲线上的工作点。在电磁体系统中,这两个因素都与激励电流有关。通过对电磁体系统磁路模型的分析,得到非线性误差随激励电流的关系曲线,发现磁轭适当的磁饱和可以减小非线性误差。通过调整激励电流,电磁体系统中的非线性误差可基本消除。磁路模型分析与实验结果在10-7量级上相符合。     

基于磁电理论对磁式带式输送机的机理分析

在讨论了三种带式输送机(气垫式、托辊式、磁式)主要优缺点的基础上,根据目前气垫带式输送机(气垫机)以及托辊带式输送机的发展与应用,提出了磁式带式输送机的结构以及运行机理。磁式带式输送机将输送机上的托辊用磁场代替,输送带为磁性输送带,在盘槽处安装矩形线圈,通电后矩形线圈产生磁场,利用磁极相同具有相互排斥的特性支撑输送带及其物料,这样可以使原有的按一定间距布置的托辊支撑或者连续的气垫支撑变为连续的磁场支撑,因为输送带与盘槽的接触是空气接触,减小了运行阻力。该设计的特点是可以通过改变通电线圈电流的大小进而改变磁场大小,从而适用于不同重量物料的运输。     

大间隙磁力传动系统驱动规律的仿真研究

针对已提出的大间隙行波磁场驱动的磁力传动系统,采用现代计算技术和数值计算中的有限元理论,运用ANSYS软件的磁场分析功能,建立了磁力传动系统的实体模型和有限元模型,通过模拟永磁体的角位移和电磁体线圈的通电状态,对系统工作过程进行了仿真;研究了系统永磁体在转动过程中的受力情况和各参数对系统驱动能力的影响规律,并进行了实验验证。研究结果表明:通过增加线圈匝数、线圈通电电流、永磁体外径和永磁体磁化强度,减小电磁体和永磁体间耦合距离,将电磁体和永磁体的相对位置沿x方向两侧(左侧或右侧)置于5 mm～10 mm范围内等方法,可提高系统的驱动力矩。     

基于MATLAB的永磁体直线电机的设计

理想面电流模型建立在充分均匀磁化的单块矩形永磁体上,在MATLAB程序语言中根据毕奥一萨伐尔定律公式进行编程,运用符号运算推导出磁体外一点的磁感应强度的微分符号表达式,然后通过数值积分得到矩形永磁体的空间磁场分布数据,并绘制出曲线图.再进一步利用多块矩形永磁体构成简单的直线电机磁场模型,通过编程对通电线圈的受力情况做分析计算,线圈在磁场中的受力变化曲线图通过数值积分的方法得到.通过线圈受力曲线分析,对直线电机工作原理与设计进行初步探讨.     

EAST液态锂试验测试平台磁体系统的MATLAB辅助设计

为了设计一套液态锂台面试验测试平台磁体系统,并保证磁体线圈的安全稳定运行,采用了MATLAB对其进行辅助设计,并对计算结果进行了校核计算。通过对线圈产生的磁场及其电参数和水参数的计算,可知:线圈的安匝数、线圈半径等对线圈磁场的分布、冷却水的流速及平台的综合成本具有显著的影响。计算结果对于磁体线圈的参数设计,以及冷却水泵和电源的选型具有重要的指导意义。     

大间隙磁力传动系统参数对驱动力矩的影响

根据大间隙磁力传动系统的工作原理及成人生理指标对轴流式血泵的工作要求,设计并搭建了用于系统驱动力矩实验研究的装置。通过改变系统中电磁体和永磁体沿Z轴方向的耦合距离、电磁体和永磁体沿Y轴正、负方向的相对位移,以及电磁体线圈通电电流等参数,进行系统驱动力矩的实验研究,得到各参数对驱动力矩的影响规律,为系统的优化设计提供了依据。     

圆筒式磁流变制动器磁路设计与优化分析

针对传统磁流变器件中励磁线圈长时间通电产生高温致使磁流变液制动效率失效的问题,设计一种利用永磁体代替通电线圈充当磁源的圆筒式磁流变制动器。针对该传动装置,从理论分析了制动器工作原理,建立了磁路模型;应用ANSYS对制动器的磁路模型进行仿真分析,验证了理论模型的正确性。仿真优化结果表明,添加隔磁环可以增大磁场强度,但磁场波动较大;一定范围内的磁偏角可增大磁场强度且不会产生磁饱和现象。     

电磁小冲床

电磁小冲床是利用通电线圈产生的磁场所做成的一种驱动装置,现介绍如下。一、结构与原理(见图):线圈架10是利用现成的漆包线     

我国科学家研制出世界第二高磁场超导磁体

正我国科学家采用自主高温内插磁体技术,研制了超导磁体,于日前成功产生了27.2 T的中心磁场。这是由全超导磁体产生的世界第二高磁场,表明我国高磁场内插磁体技术已达到世界一流水平。一般低温超导磁体产生的磁场相对较低。为了获取高强磁场,科学家在低温超导磁体的同轴结构中插入高温超导磁体,使     

外加磁场对磁流体润滑油膜轴承的影响

为了研究磁流体润滑油膜轴承内磁场的分布情况,分别通过永磁铁、螺线管及亥姆赫兹线圈对其施加3种不同形式的外磁场。通过磁场二维实体有限元模型的数值仿真,分析在3种模型下磁流体润滑油膜轴承的磁场分布特性,并比较磁场在油膜区的分布情况。结果表明,永磁铁模型的磁场主要分布在永磁铁、油膜、轴承座以及靠近磁铁的轧辊部分,螺线管模型的磁场主要分布在油膜、轴承座以及靠近磁铁的轧辊部分,亥姆霍兹线圈模型的磁场主要分布在线圈以及油膜的端部;3种模型在油膜区磁场分布沿轴向均呈现中间小、两端大的不均匀现象,且具有端部效应;永磁铁模型和螺线管模型在油膜区磁场沿径向分布均匀,亥姆霍兹线圈模型沿径向分布不均匀。     

Wearable handwriting input device using magnetic field: Geomagnetism cancellation in position calculation

In this paper an efficient technique using magnetic field is proposed for wearable handwriting input. This device requires mounting a permanent magnet onto fingertip and detecting the magnetic field generated by the magnet through magnetic sensors at the wrist of the other hand. The position of magnet is calculated by the vector of the magnetic field. And a method is proposed to avoid geomagnetic influence, using two magnetic sensors. Numerical methods are used to calculate the position of magnet with geomagnetism cancellation. Two numerical methods have been adopted and compared. A prototype device is made and we succeeded to get the trajectory of handwriting input character.     

Three-dimensional electromagnetic analysis and design of permanent magnet retarder

An eddy current retarder for vehicles generates much heat when it works continuously, which leads to serious decline in braking torque. This paper proposes a novel permanent magnet retarder (PMR) for vehicles, whose cooling system connects with engine cooling-water. A three-dimensional finite element model is developed to model the electromagnetic behavior of a permanent magnet retarder under a constant speed. The magnetic field and eddy current field in PMR are numerically solved by a finite element method. By accounting for the nonlinear permeability of the rotor and the weakened effect in the magnetic field that is generated by the eddy current magnetic field, the calculation accuracy of air-gap magnetic field is enhanced. Experiment shows that the temperature of the retarder is less than 150°C, and the braking torque keeps the hard characteristics curve. The calculated air-gap magnetic flux density is fairly good agreement with the measured one.     

新型肠道胶囊式微型机器人的运动特性

提出一种胶囊微机器人的外旋转磁场驱动方法,原理是以径向磁化瓦状多磁极构成的圆筒形NdFeB永磁体为外驱动器,以胶囊微机器人内嵌同磁极结构NdFeB永磁体为内驱动器,通过外驱动器旋转产生旋转磁场的磁机耦合作用,形成内嵌驱动器对胶囊微机器人的驱动力矩,在胶囊表面螺旋与流体形成的动压力作用下,实现胶囊微机器人在肠道内旋进。首先介绍胶囊微机器人系统的结构,然后根据雷诺和Navier-Stokes方程建立管道环境内胶囊微机器人的运动数学模型,对其螺旋参数与速度的关系进行理论与试验研究,并发现了临界间隙现象。试验表明,该胶囊微机器人具有驱动力矩大、适合大粘度液体封闭管道内行走等特点,在人体肠道和血管内具有很好的应用前景。     

Rotating magnetic beacons magnetic field strength size in SAGD

Rotation magnetic beacons magnetic field strength is very important to drill parallel horizontal twin wells in steam assisted gravity drainage (SAGD). This paper analyzes a small magnet with a diameter of 25.4 mm. At each end, there is a length of 12.6 mm with permanent magnet, and in the middle, there is a length of 78mm with magnetic materials. The magnetic field strength generated by the magnetic material of 1J12, 1J50, and 1J79 is analyzed, respectively. ANSOFT software is used to simulate the magnetic field strength generated by different magnetic materials above, which also be tested through experimental methods. The comparison of the simulation and experimental results show that experimental and simulation results are basically consistent, and the results can meet the specific requirements of engineering applications.     

调磁环材料性能对永磁齿轮损耗的影响研究

磁场调制型永磁齿轮作为一种新型永磁变速装置,易产生较大磁场损耗,降低永磁齿轮工作效率,限制其传递能力的进一步提升。提出整体成型动力传动式调磁环提高了扭矩传动能力,建立调磁环三维模型开展了强度、刚度和损耗计算,并结合永磁齿轮性能测试分析了调磁环骨架材料和调磁极片材料的损耗,研究三种不同调磁环承载骨架材料参数对永磁齿轮损耗和效率的影响,对永磁齿轮参数进行优化并确定最优扭矩骨架承载材料。结果表明,特种工程塑料调磁环骨架材料能大幅降低永磁齿轮损耗,有效提升传动效率,永磁齿轮实测传动效率可达93.8%。     

混合式永磁同步电机弱磁性能的研究

针对传统永磁同步电机弱磁性能不佳的问题,提出了应用混合式结构来改善永磁同步电机弱磁性能。研究了传统永磁同步电机的结构,得出了传统永磁同步电机弱磁困难的原因是电枢磁势和转子励磁磁势的不对等。分析了混合式永磁同步电机的结构,得出了其转子永磁体用量少,励磁磁势较小;气隙很小同步电感大,短路电流与额定电流的比值小。介绍了应用短路电流与额定电流的比值来判断永磁同步电机弱磁性能的方法,分析得出了混合式结构弱磁性能要好于传统永磁同步电机。采用了基于直轴电流负向控制的附加闭环方法进行弱磁控制,对传统永磁同步电机和混合式永磁同步电机的弱磁性能进行了对比实验,混合式结构的弱磁扩速倍数为传统式结构的2.63倍。研究结果表明,混合式结构可以有效提升永磁同步电机弱磁性能。     

Position and orientation detection of capsule endoscopes in spiral motion

In this paper, a position and orientation detection method for the capsule endoscopes devised to move through the human digestive organs in spiral motion, is introduced. The capsule is equipped with internal magnets and flexible threads on their outer shell. It is forced to rotate by an external rotating magnetic field that produces a spiral motion. As the external magnetic field is generated by rotating a permanent magnet, the 3-axes Cartesian coordinate position and 3-axes orientation of the capsule endoscopes can be measured by using only 3 hall-effect sensors orthogonally installed inside the capsule. However, in this study, an additional hall-effect sensor is employed along the rotating axis at a symmetrical position inside the capsule body to enhance measurement accuracy. In this way, the largest position detection error appearing along the rotating axis of the permanent magnet could be reduced to less than 15mm, when the relative position of the capsule endoscope to the permanent magnet is changed from 0mm to 50mm in the X-direction, from −50mm to +50mm in the Y-direction and from 200mm to 300mm in the Z-direction. The maximum error of the orientation detection appearing in the pitching direction ranged between −4° and +15°.     

Development of EMA transducer for inspection of pipelines

Electromagnetic acoustic transducers (EMATs) have potential for In-line inspection (ILI) of pipelines compare to other Nondestructive evaluation (NDE) methods, since EMAT doesn’t need to contact and/or coupling material and can detect defects in outside of pipelines. However, improvement of transduction efficiency of EMATs is needed to secure integrity of the pipelines. To improve performance of EMAT, optimization of major parameters, such as strength of permanent magnet, shape of coil, configuration of static and dynamic magnetic fields is required. Thus, in this paper, investigation of transduction efficiency with variation of major parameters are performed by comparison of generated ultrasonic signals. Based on the investigation results, EMATs for ILI of pipelines are designed and fabricated with optimized Periodic solenoid array (PSA) types of meander-line sensor, static magnetic field, and then, performance of the developed EMATs are evaluated by detecting defects in the gas pipelines mounted in the one-bed testing system.     

永磁体磁场三维模拟及其对粒子作用研究

采用瓦形磁极结构,利用有限元分析软件ANSYS,对多个瓦形永磁体进行磁场感线密度和磁场强度仿真模拟,得到合理的磁极分布,从而得到合理的磁路。对带电粒子在永磁体磁场中的受力和轨迹分析,结果表明:采用4个磁极相隔90°,可以得到比较合理的磁路;带电粒子受到罗仑兹力作用,粒子做回旋运动,运动轨迹为螺旋线。