Energy and density of ions in vacuum arcs between axial and radial magnetic field contacts
Energy and density of ions in vacuum arcs between axial and radial magnetic field contacts
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DOI：
10.1109/27.964464
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发表时间：
2001-10
影响因子：
1.5
通讯作者：
G. Duning;M. Lindmayer
中科院分区：
文献类型：
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作者：
G. Duning;M. Lindmayer
在真空断路器中，使用两种不同的触点类型来克服电弧收缩的后果，当电流超过数千安时，就会出现电弧收缩。径向磁场 (RMF) 迫使收缩的电弧旋转并将其功率更均匀地分布在接触表面上。轴向磁场 (AMF) 触点可防止电弧收缩至更高阈值。为了提高两种类型真空断路器的开断能力，有必要了解零电流附近真空等离子体（“真空电弧”）的过程和特性，例如等离子体密度及其衰变以及等离子体物质的能量。在这项工作中，通过减速场分析仪研究了电流为零之前最后 3 ms 内真空电弧等离子体中离子的能量分布，电弧电流高达 /spl ap/9 kA RMS，并且可以观察到 RMF 和 AMF 接触之间的显着差异。对于 5 kA 以上的电流，两种情况的分布都类似于麦克斯韦分布，这是碰撞确定的等离子体的特征。在较低电流下，即当电流接近零时，RMF 排列显示离子具有强烈的定向运动，而 AMF 接触的能量分布似乎更容易受到碰撞的影响。还有 AMF 场中 v/spl 次/B 离子旋转的迹象。此外，还研究了作为等离子体密度指示的弧后电荷及其在电流为零后的自由衰减。对于 AMF 触点，零电流时的初始密度更高，尤其是在电弧电流较低时。第一衰减时间常数随着电弧电流的增加而略有增长，并且对于较大的屏蔽直径，即等离子体体积与用于复合的屏蔽表面之间的比率较高，第一衰减时间常数较高。
In vacuum circuit breakers, two different contact types are used to overcome the consequences of arc constriction, which sets in when currents of several kiloamperes are exceeded. Radial magnetic fields (RMF) force the constricted arc to rotate and distribute its power more evenly on the contact surface. Axial magnetic field (AMF) contacts prevent the arc from becoming constricted up to higher thresholds. To improve the interruption capability of vacuum circuit breakers of both types, it is essential to know about the processes and properties of the vacuum plasma ("vacuum arc") around current zero, such as plasma density and its decay and the energy of the plasma species. In this work, the energy distribution of ions in the vacuum arc plasma during the last 3 ms before current zero has been investigated by means of a retarding field analyzer up to arc currents of /spl ap/9 kA RMS, and significant differences could be observed between RMF and AMF contacts. For currents above 5 kA the distribution in both cases resembles a Maxwellian distribution, characteristic for a collision-determined plasma. On lower currents, i.e., when current zero is approached, RMF arrangements show ions with strongly directed motion, while the energy distribution for AMF contacts seems to be more influenced by collisions. There are also indications of the v/spl times/B ion rotation in the AMF field. Furthermore the post-arc charge as an indication of the plasma density and its free decay after current zero has been investigated. With AMF contacts, the initial density at current zero lies higher, especially on lower arc currents. The first decay time constant grows slightly with the arc current, and lies higher for larger shield diameter, i.e., higher ratio between plasma volume and shield surface for recombination.