Micro-particle impact phenomena on contact surface under different applied voltages in vacuum interrupters

Abstract

According to the vacuum breakdown model based on Cranberg “clump” hypothesis, micro-particles on contact surface can be detached from the contact surface and accelerated across the vacuum gap towards to the opposite contact under an applied voltage in vacuum interrupters (VIs). Finally they can impact on the target contact surface with high velocities, which probably triggers a breakdown in the vacuum gap. Thus, the mechanism of the impact phenomena may be the key to understanding the mechanism of the vacuum breakdown initiated by the micro-particles. Moreover, the detailed nature of the dynamic impact process is a subject of the hydro-dynamical theories on the projectile impact. The objective of this paper is to study the micro-particles impact phenomena in VIs by introducing a mesh-free numerical calculation method Smoothed Particle Hydrodynamics (SPH) method which is an efficient method of the projectile impact studies. In this paper, the materials of the micro-particle and the target contact were assumed to be copper and stainless-steel, respectively. The radius of the micro-particle was assumed to be 0.1 µm. The characteristics of the deformations occurring during the high-velocity impact processes are investigated under the different applied voltages (10 to 60 kV). As a result, it is found that the deformations of the micro-particles and the target contacts are severer with the increase of applied voltages, due to the increase of the impact velocities. With the applied voltages 50 kV and even to 60 kV (the impact velocity 526 and 631 m/s), there can be damages generated on the contact surface accompanying by a large number of high-velocity secondary particles. Furthermore, the influencing factors of the micro-particles impact phenomena in VIs, such as the size of the micro-particles, the microscopic electric field distribution, the contact materials and so on, have also be considered. The result of this paper may provide some useful information to understand the vacuum breakdown initiated by the micro-particles.