Properties of Intermediate-frequency Vacuum Arc Influenced by Electrode Diameter and Material in Axial Magnetic Field

With the development of more-electric and all-electric aircraft technology, it is a trend to unify secondary energy sources, such as mechanical energy, pressure energy, hydraulic energy and so on, into electric energy gradually. Obviously the capacity of power system, distribution system and consumer equipment will experience a giant promotion. The variable-frequency power system has become the most important development orientation for the future aircraft. It is the most advanced technology around the world that intermediate-frequency (360Hz similar to 800Hz) electric power is supplied by the variable-frequency generator which is connected to the engine directly. In this paper, intermediate-frequency (400Hz) vacuum arc in the cup-type interrupter with axial magnetic field (AMF) is generated by the oscillating circuit. In the condition of 3mm opening gap, experiments of different current are carried out in interrupters with the diameters being 41mm and 58mm, and the electrode materials being Cu, Cu-W-WC alloy and CuCr50 alloy respectively. The arc voltage and the transformation of arc performance are analyzed contrastively. It is indicated by the experiment results that breaking capacity of vacuum interrupter and properties of intermediate-frequency vacuum arc are closely related to the electrode diameter and material. With the electrode diameter increasing, arc voltage decreases gradually, and diffuse arc tends to be stable, for which the breaking capacity is better. For the same size of electrode diameter, the breaking capacity in CuCr50 is better than that both in Cu and Cu-W-WC.