Vacuum interrupter for VXG(151)

The use of a vacuum for switching electrical currents was motivated by the observation that a one-centimeter gap in an X-ray tube could withstand tens of thousands of volts. Although some vacuum switching devices were patented during the 19th century, they were not commercially available.The interrupter's enclosure is made of glass or ceramic. Hermetic seals ensure that the interrupter vacuum is maintained for the life of the device. The enclosure must be impermeable to gas, and must not give off trapped gas. A vacuum interrupter has shields around the contacts and at the ends of the interrupter, preventing any contact material vaporized during an arc from condensing on the inside of the vacuum envelope. This would reduce the insulation strength of the envelope, ultimately resulting in the arcing of the interrupter when open.Although some vacuum-interrupter designs have simple butt contacts, contacts are generally shaped with slots, ridges, or grooves to improve their ability to break high currents.Only few manufacturer of vacuum interrupters worldwide produce the contact material itself. The basic raw materials, copper and chrome, are combined to a powerful contact material by means of the arc-melting procedure.