Patent GB-405769-A (GB)
Title: Improvements relating to alternating current electric switches
IPC: H01H3/26
Filed: 1932-11-11
Abstract: 405,769. High - tension switches. ANDERSON, J., 137, Aldridge Road, Perry Barr, Birmingham. Nov. 11, 1932, No. 31977. [Class 38 (v).] Electric - motor actuation; sparking, preventing.-An arrangement for opening an alternating - current switch at the zero value of the current comprises a series synchronous motor, a tripping or opening device adapted to be actuated by the motor, and means for bringing the said device into its operative position for effecting the opening of the switch for the motor at a predetermined instant in the revolution of the motor armature. In the arrangement shown in Figs. 1 and 2, a pair of synchronous motors a, b is provided, one with a series winding and the other with a shunt winding, the motors being interconnected by a resilient coupling c. A crank e, adjustably mounted on the rotor of one of the motors, carries a projection f which is adapted to engage an arm g pivoted on the switch arm h and to move the latter away from the fixed contact j. The arm g lies normally out of the path of the projection f, but can be brought into said path, when it is desired to open the circuit, by means of a bell crank lever having arms n, o, the arm o being adapted to be brought into the path of the projection f, while the arm n is adapted to move the arm g into its operative position. The lover n, o may be actuated by hand, or by energizing an electromagnet p, the armature q of which is connected by a link s, lever t and link u to a lever v which carries the pivot w of the lever n, o. The rocking of the lever n, o about its pivot is controlled by a spring y engaging an abutment on the link u. When the electromagnet is energized, the arm o is brought into the path of the projection f, which rocks the arm about its pivot and causes the arm n to lift the arm g into the path of the projection. In the next revolution of the rotor, the projection f strikes the arm g and opens the switch, the opening taking place at or about the instant of zero current as a result of the adjustment of the projection. In a modification, Fig. 4, the pivoted switch lever 4, which co-operates with a fixed contact 9, is connected by a link 5 and lever 6, pivoted at 7, to one end of a bar 10 which is pivoted at its other end 11 to a lever 12 having a slot 14 mounted on a pivot 13. When it is desired to open the switch, an electromagnet 16 is energized to attract an armature 17 connected by a link 19 to a lever 20 pivoted at 21. A projection 23 on a lever 22 pivoted on the lever 20 is thereby moved into the path of an adjustable projection 3 carried by the crank disc 2 of the motor. When the part 23 is struck by the projection, a link 29 is moved downwardly and, through the medium of a bellcrank lever 30, rocks the lever 12 into such a position that its upper end lies in the path of the projection 3. During the next revolution of the crank disc, the projection 3 rocks the striking lever about its pivot, and thereby brings the bar 10 into such a position that a gap 15 in the bar is engaged by the projection immediately after the latter leaves the lever 12 ; on continued movement of the projection, the bar 10 is raised to open the switch. The switch is held open by the engagement of a catch lever 8, pivoted to the link 5, with a fixed abutment 32. To reclose the switch, the lever 8 is raised ; it can then be used for moving the switch lever 4 into the closed position or an extra hand lever may be provided for this purpose. The act of reclosing the switch brings the lever 12 and bar 10 back to the position shown, and the lever 22 is then re-set by means of a rod 25 carried by the lever 20.