A Modified Lattice Model of the Reversible Effect of Axial Strain on the Critical Current of Polycrystalline REBa2Cu3O7-δ Films

The strain effect on the critical current is one of the most important properties for polycrystalline YBa2 Cu3O7-δ （REBCO, RE： rare earth） films, in which the reversible effect is intrinsic in the range of strain 0 and the irreversible strain εirr. By introducing the applied strain, a modified grain boundaries （GBs） in the REBCO film is developed. lattice model combining the strain and misorientation of A good agreement of the calculation on the lattice model with the experimental data shows that the lattice model is able to well describe the reversible effect of axial strain on the critical current of the REBCO film, and provides a good understanding of the mechanism of the reversible effect of the strain. Moreover, the effects of the crystallographic texture of the REBCO film and the residual strain εr on the variation of the critical current with the applied strain are extensively investigated. Furthermore by using the developed lattice model, the irreversible strain εirr of the REBCO film can be theoretically determined by comparing the calculation of the critical current-strain curve with the experimental data.

Axial Shock in a Cylindrical Plasma with Current

Hugoniot relations of a two-dimensional axial shock with current and magnetic field in a cylindrical shock tube were investigated by a numerical method. The radial profiles of the magnetic field, electric current, pressures, flow velocities and temperatures between the up- and down-stream radial force-balanced plasma of the shock were revealed by numerical analysis. It is clearly found that the axial shock can lead to two effects： one is an inverse skin effect （i.e., the current density rises towards the center of the conductor）, the another is a reversed current effect which occurs near the edge and about a half radius. It is also found that the radial gradient of pressure, density and temperature all become very large near the center due to the axial shock.

基于轴向电涡流效应的高精度长位移传感器

为了实现大行程精密光学调焦组件的高精度实时检测,研究基于轴向电涡流效应的高精度长位移传感器。建立了长位移电涡流探头仿真模型进行线性度测试,搭建电涡流传感器测试系统进行精度实验,并将长位移电涡流传感器接入精密光学调焦组件。实验结果表明:在可测量位移达到24 mm的同时,线性度优于1%,分辨率优于0.5μm,精度优于1μm,高精度长位移电涡流传感器符合精密光学调焦组件的需求。

大型变压器螺旋绕组扭转电磁力的研究

大型电力变压器螺旋线圈的扭转变形主要是由于轴向电流分量和辐向漏磁场共同作用所产生的.针对DEP-240000 kVA/500 kV型大型电力变压器低压螺旋绕组在轴向电流分量作用下产生的扭转电磁力问题进行了研究,对变压器结构及材料特性等对轴向电流引起的扭转电磁力的影响进行了分析计算,给出了变压器低压螺旋绕组单位长度扭转电磁力沿绕组高度的分布规律及相应抑制大型变压器螺旋绕组扭转变形的措施,为大型变压器的优化设计提供了参考依据.

纵向磁场下中频真空电弧的重燃现象分析

中频供电系统已在航空电源中得到广泛应用。根据实验结果,电流开断能力从360Hz时的22.4kA下降至850Hz时的14.0kA。该文研究纵向磁场下360~850Hz真空电弧开断失败时的重燃现象。由Mayr模型的最小二乘法解可知,发生击穿时电弧能量衰减的时间加长,这是不利于电流开断的。一方面,随着电流频率的增加,相对小的电流值就会使电流过零时的变化率di/dt达到开断阈值;另一方面,频率提高会增强涡流效应,导致纵向磁场过零后的剩余磁感应强度和滞后相位增加,阻碍过零后等离子体扩散。实验中发现,电弧重燃点总出现在触头边缘处,计算表明触头边缘处的电场强度集中、电流密度高,进而导致场致发射的概率增大。此外利用帧差法分析电弧图像,估算得到金属液滴的运动喷射速度为10~20m/s。电流过零后金属液滴的消失时间大于中频电流半个周波时间,金属液滴的存在是引起电弧重燃的因素。

中频条件下真空灭弧室的纵向磁场仿真

该文研究了中频400~800Hz条件下纵磁真空灭弧室内的磁场特性,利用Ansys Maxwell求解了三维瞬态纵向磁场分布。由计算结果可知:在电流变化的过程中,中心区域纵向磁场的变化明显滞后于其他区域。电流峰值时在触头片开槽交错放置的位置有磁场峰值区域,电流过零时中心区域有明显剩磁。当频率增加时,涡流效应更明显,使纵向磁场的磁感应强度值减弱。对中心点,频率提高导致过零时剩磁增加,磁场滞后相位更明显,影响电弧扩散。增加触头片开槽数可以减弱涡流效应,而增加触头杯座槽旋转角,触头中间平面磁感应强度的最大值近似线性增加。文中通过分析电弧形态和电压等实验结果验证了磁场滞后对真空灭弧室的开断能力的影响。

中频真空开关纵向磁场特性分析：实验仿真平台设计

本文研究了400~800Hz条件下纵磁真空灭弧室内的磁场特性。首先根据麦克斯韦方程组和磁场的合成矢量关系,分析了纵向磁场的变化滞后于电流和频率增加时涡流效应更明显的原因,然后利用ANSYSMAXWELL求解了三维瞬态纵向磁场分布。由计算结果可知:在电流变化的过程中,中心区域磁场的变化明显滞后于其他区域。电流峰值时在触头片开槽交错放置的位置有磁场峰值区域,电流过零时中心区域有明显剩磁。当频率增加时,涡流效应更明显,使纵向磁场的磁感应强度值减弱。对中心点,频率提高导致过零时剩磁增加,磁场滞后相位更明显,影响电弧扩散。增加触头片开槽数可以减弱涡流效应,而增加触头杯座槽旋转角,触头中间平面磁感应强度的最大值近似线性增加。并通过实验验证了磁场滞后对真空灭弧室的开断能力的影响。