This article deals with the effects of homopolar magnetic fields on the lifetime of low-current dc vacuum arcs. A homopolar magnetic field is a distribution with the axially symmetric radially oriented field in the contact gap. It is produced when two dipole magnets are kept with the same poles facing each other. Switching experiments are conducted using an off-the-shelf ac vacuum contactor, and the ring magnets are used to set up a homopolar magnetic field in the contact gap. The arcing times are measured for currents varying from 1 to 30 A with voltages up to 100 V and magnetic surface strengths from 0.34 to 0.43 T. The tests are performed with the fixed contact of the vacuum contactor connected to positive as well as negative polarity. It is observed that the arcing time values are lesser in the presence of magnetic field with the fixed contact at the negative polarity due to asymmetry in the placement of the ring magnets. Finite element method (FEM) simulations are performed to examine the magnetic field distribution in the contact gap. The ratio of radial-to-axial magnetic field components in the contact gap decreases with increasing strength of magnets in the present experimental arrangement. It correlates well with the observed arcing time trends against the variation in the strength of magnets and the polarity of the fixed contact. The present article shows the potential of homopolar magnetic field in the development of dc vacuum contactors and interrupters without the need to create an artificial current zero using forced commutation.

中文翻译：

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同极磁场对低电流直流真空电弧的影响

本文讨论了单极磁场对低电流直流真空电弧寿命的影响。单极磁场是在接触间隙中具有轴对称径向取向场的分布。当两个偶极磁铁保持相同的磁极彼此面对时，就会产生这种情况。使用现成的交流真空接触器进行开关实验，并使用环形磁铁在接触间隙中建立同极磁场。电弧时间是针对 1 至 30 A 的电流、高达 100 V 的电压和 0.34 至 0.43 T 的磁表面强度进行测量的。测试是在真空接触器的固定触点连接到正极性和负极性的情况下进行的。可以观察到，由于环形磁铁放置的不对称性，在存在磁场且固定触点处于负极性的情况下，电弧时间值较小。执行有限元方法 (FEM) 模拟以检查接触间隙中的磁场分布。在本实验布置中，接触间隙中径向与轴向磁场分量的比率随着磁体强度的增加而降低。它与观察到的电弧时间趋势与磁铁强度和固定触点极性的变化密切相关。本文展示了单极磁场在直流真空接触器和断续器的开发中的潜力，无需使用强制换向创建人工零电流。