Electrical contact with dielectric breakdown of interfacial gap

TL;DR

This paper investigates how dielectric breakdown outside the contact area influences electrical contact behavior, developing models that correct classical theories by including discharge effects, with implications for contact resistance and surface damage.

Contribution

It introduces a numerical model and closed-form solutions incorporating dielectric breakdown effects into electrical contact theory, improving understanding of current distribution and resistance.

Findings

Current density is finite at the contact periphery due to discharge effects.

Ignoring discharge leads to overestimated contact resistance.

Current density increases radially and drops within the discharge zone.

Abstract

Electrical contact is fundamental to almost every aspect of modern industry, including the fast-growing electric vehicle industry. In metallic contacts in atmospheric conditions, most of the electrical current passes via the micro-junctions formed between two electrodes. The classic electrical contact theory predicts an infinite current density at the circular contact periphery. In the present work, we explore the influence of the dielectric breakdown of air outside the contact area on the electrical contact interface. Incorporating the discharging boundary condition governed by the modified Paschen law, we develop the numerical model as well as two sets of closed-form solutions for low applied voltage cases where two electrodes are in solid-solid contact and complete separation, respectively. For Hertzian contact, the present work theoretically proves that the ignorance of discharge can lead to a singular current density at the contact periphery and an overestimation of the electrical contact resistance. The current density monotonically increases along the radial direction to a finite value at the contact area periphery, followed by a monotonic drop within the discharge zone. The present study serves as a foundation for the modeling of discharging rough surface electrical contact and sheds light on the machine element surface damages caused by the electrical discharge machining.