Evaluation of DC Interruption Performance of VCB in Various Electrode Materials

Abstract

The purpose of this paper is to clarify the electrode material that is optimum for DC interruption by VCB. Since there is no current zero point in DC, the test was carried out by a method in which high-frequency current is injected into a main current from another circuit to generate a current zero point. The test was performed with changing the main current value, the high-frequency current value, the frequency of the high-frequency current, and the high-frequency injection timing. The electrode was axial magnetic field type, and we tested four types of contact materials such as Cu, CuCr, AgWC. In addition, the behavior of the arc between the electrodes during high-frequency current injection was recorded using a high speed camera in the interruption success and the interruption failure condition. When the interruption was successful, it was observed that the plasma between the electrodes diffuses in a time shorter than 4.8 μs. When the interruption was failed, it was observed that the plasma between the electrodes don't disappear. The high-frequency interruption performance in various electrode materials was evaluated by the index consisting of the product of the residual plasma density between the electrodes and the gradient of the current at the current zero point. It was found that CuCr electrode with Cu weight ratio above 50% is superior for high-frequency interruption performance.