Numerical and Experimental Investigation of the Thermal Conductivity Affecting on Current Chopping and Transient Recovery Voltage in Low Current Vacuum Arc for Ag-Pd Compound Cathode Using Cathode Spot Model

This analysis describes the physical mechanism of the effect of thermal conductivity on instability phenomena using the cathode spot model. An analysis of stable arc current is performed by changing the thermal conductivity of the Silver cathode by compound material. It has been found out that the minimum stability arc is inversely proportionate to the thermal conductivity. These results have confirmed that stable arc current has been approved by the cathode spot model, and it can be used to design an amount of weight percentage of the compound cathode for reducing the chopping current. Moreover, the minimum stable arc current decreases with the decrease of thermal conductivity. These results reflect directly on the current chopping level. These show that if the chopping current is reduced, then the peak of transient recovery voltage will be reduced. It has been found out that the instability arc current is dependent on cathode characteristics. This is a significant result for the development of cathode materials for low-surge vacuum interrupters. Finally, it can be concluded that the results obtained in this study clearly demonstrate the physical mechanism of the current instability and transient recovery voltage occurrence with reducing cathode thermal conductivity.