Three-dimensional Electromagnetic Thermal Fluid Simulation of Cathode Jet Contributing to Motion of Cathode Spots in Vacuum Arc

Vacuum arcs have been applied to circuit breakers, metal processing and other applications. However, its physical phenomena have not been elucidated today, especially the physics of the cathode spots. The mechanism of the motion of the cathode spot under external magnetic field has not been clarified quantitatively. The ions generated from the cathode spots are accelerated by the pressure gradient to generate a cathode jet with high speed. This behavior of the ions is considered to be responsible for the motion of the cathode spots, especially the retrograde motion. In this research, the three-dimensional electromagnetic thermal fluid simulation was developed to clarify the physics and conditions of cathode spot motion under external magnetic field. As a result, it found that the moving direction of cathode spots plasma was determined by electromagnetic force formed by the cathode jet containing ions from cathode spots and external transverse magnetic field.