Estimation of the velocity of arc motion in vacuum interrupters with radial magnetic field type of contacts

In the vacuum interrupters employing the radial magnetic field (RMF) type of contacts, the constricted arc column is made to move on the surface of the contacts. The motion of the arc ensures that no particular area of the contact surface is overheated thus minimizing the emission of metal vapor and temperature rise of the contact surface and hence enhancing the current interruption performance. The arc motion is the result of the interaction of the arc current and the magnetic field produced by the flow of the current through the contacts. The velocity of the arc motion would thus be governed by the magnitude of arc current and the design of the contact. Higher the velocity of motion of the arc, higher would be the probability of a successful interruption. A wide range of the values of this velocity and the empirical formulae for the velocity have been reported in the literature. This paper reports the results of a research work which aims to arrive at the value of the arc velocity through experimentation and also through a modeling-simulation approach. The research also aims to establish a correlation between the arc velocity, magnitude of current and the contact design. This correlation is also presented in this paper.