Vacuum cartridge for an electrical protection apparatus such as a switch or circuit breaker

Vacuum cartridge for an electrical protection apparatus such as a switch or a circuit breaker, said cartridge comprising an enclosure of substantially cylindrical shape closed by two end plates, two contacts extending axially inside the enclosure, at least one whereof, called the movable contact, is connected to an operating mechanism and is mounted sliding between a closed position of the contacts enabling the current to flow and a position wherein the contacts are separated and form an electric arc between them, and a means for producing an axial magnetic field in the arc formation zone, comprising at least one conducting shield fitted around the periphery of at least one of the contacts, said shield being shaped and arranged in such a way as to withstand the electric field arising from the recovery voltage imposed by the power system after breaking and to thus considerably reduce the electric field at the edge of said contact and in that the physical continuity on the contacts in the closed position is achieved by means of a ring, sectors of ring or studs arranged on the contact surface of one of the contacts and situated respectively facing a ring, sectors of ring or studs arranged on the contact surface of the other of the contacts.