Abstract: An improved trip device for an electric switch comprises a yoke, a permanent magnet immovably positioned with respect to the yoke and a movably supported armature forming a first magnetic circuit, in which the armature is able to assume a first position under the influence of the magnetic field of the permanent magnet. A magnet winding and spring are provided for causing the armature to assume a second position in response to the magnetic field generated by an electric current, flowing during operation in the magnet winding. For adjusting the threshold value at which the armature is moved to its second position, a second magnetic circuit in the form of shunt interacting with the yoke and the permanent magnet is provided. The magnetically effective surface area of the shunt is smaller in the vicinity of the section thereof which interacts with the yoke than in the vicinity of the section which interacts with the permanent magnet.

Abstract: A three-phase isolating disconnector for use in a high-voltage switchgear arrangement in two gas-filled chambers, separated by a wall, in said arrangement, comprising for each phase a disconnector member extending through the wall and fastened and movable therein, this disconnector member being provided with a disconnector contact in each chamber, and comprising two fixed counter disconnector contacts which are connected to other parts of the switchgear arrangement and of which one is disposed in one chamber and the other in the other chamber. The movable disconnector member is brought by rotation from a first position, in which it conductively connects together the two fixed counter disconnector contacts, to a second position in which the conductive connection is broken and in which at least one disconnector contact of the movable disconnector member is connected to an earth contact, and vice versa.

Abstract: An electrical vacuum switch is provided with two mutually movable contacts of conductive material, mounted on the ends of a fixed or movable contact rod, with a laminated horseshoe-shaped ferromagnetic element being fitted around each contact rod. The magnetic circuit around the contact rod consists of a section of low magnetic resistance and a section of a high magnetic resistance. The circular base of the U-shaped inner cavity of the horseshoe-shaped element is adjacent to the associated contact rod and the elements are offset through 180.degree. C. with respect to each other, so that the internal magnetic fields generated in the horseshoe-shaped elements when current passes through the switch, to the extent that the section with high magnetic resistance is approached, are mainly oriented axially between the two horseshoe-shaped elements.