New contact design concept for low-voltage switches

Abstract

The purpose of this thesis is to find factors and suggest solutions to improve the long-term thermal and electrical stability of ABB’s AC switch-disconnectors. The challenges are found and solution are proposed in the area of the contact design, surface treatment and arc interruption, regarding the switch thermal stability. Tests are made to verify the proposed solutions. In the switches, high temperature rise is caused by the formation of insulating layers on the contacts. It is because of the lubricant burning, the contact’s surface wearing, and arcing near the contacts. It is found out that a high thermally stable lubricant can keep the temperature-rise value low. The wearing of the contacts can be decreased by its design modification. Decreasing the arc energy during the contact breaking would decrease the temperature rise of the contacts. Solid lubricant as a contact plating has shown low temperature-rise by decreasing the wearing of the contact surface.