Pot-shaped contact for vacuum switch - keeps arc on contact face of contact ring by magnetic field from radial current components

摘要

The pot-shaped support (4) is connected at its centre to the connection conductor (8) and has a contact ring (12) on its opposite face. The support has inclined slots (10) distributed around its inside face so that the current flowing always has a component moving at an angle to the axis (18) of the contact so that the arc rotates. The contact ring may be made of a sintered material containing copper and chromium or of another material suitable as a contact. The current in the contact is such that base of the rotating arc remains on the contact face. The radial current components produce a magnetic field that keeps the arc on the contact face. The arc is not subjected to forces acting radially inwards and outwards and therefore cannot migrate into the recess in the pot. The sloping edges of the contact ring prevent the arc appearing in regions where it is not subjected to the stabilising magnetic fields produces by the radial currents. (The contact pressure is also increased as result of reducing the contact surface area).