Theoretical and Experimental Work on Optimal Contact Geometries on Fast Mechanical Disconnect Switches

Fast mechanical disconnect switches (FMS) are an integral part of hybrid circuit breakers, which are proposed as protection devices to clear faults in medium voltage distribution systems. The proposed FMS is a vacuum switch that is operated by an amplified piezoelectric actuator. Such actuators enable unprecedented speed and contact separation in less than one millisecond. The limitations that come with such designs are the low contact separation of typically less than one millimeter in open position and low contact force in the order of 100 N in closed position. This requires a new design of the contacts to operate under such constraints. The geometry of the contacts must be carefully designed to minimize electrical resistance when closed and minimize electric field enhancement when open. The paper presents finite element analysis and experimental results with the aim of identifying the most suitable contact geometry for FMS. The experiments show that optimized contact geometries have up to 40% less resistance than the initial spherical geometry.