Abstract: A three-phase electrical ring main unit comprising a lower chamber module (30) having a wall structure formed from insulating resin material; three input contacts (35), one for each phase, mounted within the lower chamber; three lower switching contacts (37), each mounted within the lower chamber for movement between different switching positions; insulating closure means (55) closing the top of the lower chamber; three output contacts (49), one for each phase, carried by and exposed on a lower face of the closure means; three busbar contacts (59 to 61), each electrically connected to a respective output contact, carried by and exposed on an upper face of the closure member (55); an upper chamber module (31) having a wall structure formed from insulating resin material; means (32) securing the upper chamber above the lower chamber; three tee-off contacts (85), one for each phase, mounted within the upper chamber; and three upper switching contacts (83), each mounted in the upper chamber for movement between d

Abstract: A fuse for an alternating current power circuit. The fuse comprises an input terminal (4), a first contact (5) electrically connected to the input terminal, an output terminal (9) and a second contact (8) electrically connected to the output terminal. A fusible element (11) electrically connects the first and second contacts and completes a normal electrical path between the input and output terminals. An arcing contact (6) is positioned in relation to the first contact (5) so as to form a potential arc path between the first contact and the arcing contact, along which path an arc will become established after the fusible element breaks in response to fault current. The arcing contact (6) is electrically connected to a third terminal (41) and is electrically isolated from the output terminal (9).

Abstract: A fuse for an alternating current power circuit in the medium voltage (3.3 kV to 38 kV) range. The fuse comprises a sealed chamber and a first electrode (41) is mounted within the chamber, the first electrode having a substantially circular periphery (42) and being electrically connected to a first terminal (3) to which a first conductor may be connected. A second electrode (35) is arranged with a conductive surface internally of the chamber, the conductive surface being spaced from the first electrode. A coil (10) is connected in an electrical path between the second electrode (35) and a second terminal (18) to which a second conductor may be connected. An additional electrical contact (44) is mounted within the chamber and in direct electrical connection with the second terminal, and a fusible element (43) directly electrically connects the first electrode (41) and the additional electrical contact (44). An electronegative halogenated medium fills free space within the chamber.

Abstract: A fuse for an alternating current power circuit in the medium voltage (3.3 kV to 38 kV) range. The fuse comprises a sealed chamber and a first electrode (41) is mounted within the chamber, the first electrode having a substantially circular periphery (42) and being electrically connected to a first terminal (3) to which a first conductor may be connected. A second electrode (35) is arranged with a conductive surface internally of the chamber, the conductive surface being spaced from the first electrode. A coil (10) is connected in an electrical path between the second electrode (35) and a second terminal (18) to which a second conductor may be connected. An additional electrical contact (44) is mounted within the chamber and in direct electrical connection with the second terminal, and a fusible element (43) directly electrically connects the first electrode (41) and the additional electrical contact (44). An electronegative halogenated medium fills free space within the chamber.

Abstract: An electrical isolator has an insulated housing with input and output conductors (1, 2) therein. A spring contact (6) is mounted within the housing for movement between open and closed positions. An insulating shroud (15) fully shields that part of the bridging contact accessible through an access opening of the housing. Manually operable pressure applying structure may be operated when the bridging contact is in the closed position to control that contact between a tightened condition applying pressure between the bridging contact and the conductors without the use of springs, and a free condition wherein the contact pressure is reduced. An interlock assembly prevents engagement and disengagement of the operating member with the pressure applying structure unless the bridging contact is located in either the closed or open position.

Abstract: An electrical assembly, for example for use in low voltage supply distribution, comprises a fixed casing (4) for each of three phases. A pair of fixed contacts (e.g. 11, 12) are spaced apart within the casing and set back from an opening into the casing. A fuse carrier (29) is mounted for rectilinear sliding movement within the casing between a first position adjacent to the opening and a second position. In the second position movable contacts (30, 31) on the carrier engage the fixed contacts to close a circuit therebetween. A drive unit (50) is provided for mechanically driving the carrier between the two positions, the drive unit being a self-contained mechanism comprising a housing and a drive member movable relative thereto. The drive member can be detachably coupled to the contact carrier, and means (58, 60) provided for releasably locking the drive housing to the fixed casing.