Abstract
Consecutive stages of contact opening are described by the mathematical model. It includes phenomena in separating contacts before melting point, appearance, evolution and rupture of liquid metal bridge, the arc ignition and spreading in bridge metallic vapours until transformation of the metallic arc phase into a gaseous one. The calculation of lifetime and energy of each stage, contact voltage, temperature and other parameters are compared with experimental data obtained by T. Takagi and R. Haug. It is shown that arc duration depends on opening velocity, contact scale roughness, energy and length of liquid bridge.