Studies of electrodynamic forces occurring at electrical contacts

KNOWLEDGE of the magnitude of the electrodynamic force occurring at closed electric contacts carrying high current is important to the design of reliable contacting devices. Past work in this area by Holm1 has shown that current passing through a contact surface is constricted to flow through very small contacting spots, and that this constricted current flow causes a repulsion force to act on the contacts. Further contributions to the theory and the calculation of this force have been made through studies at the Cutler-Hammer Laboratories in Milwaukee, Wis.,2 the progress of which is reported in this paper.