Patent GB-191004811-A (GB)
Title: Improvements in and relating to the Control of Electrically Operated Switches.
Inventor: WHITE HAROLD ELIJAH
IPC: H02P1/20
Filed: 1910-02-25
Granted: 1911-01-19
Abstract: 4811. White, H. E. Feb. 27, 1909, [Convention date]. Electro - magnetic switches. - In a control system, separately-actuated contactors are mechanically interlocked with current-controlled auxiliary switches each of which controls the actuating-circuit of a succeeding contactor, and the closing of each auxiliary switch is delayed during the time its interlocked contactor is closing and the resulting increase of current is taking place. A contactor is shown in Fig. 2; it has a casting 26 secured by bolts to the board 25. The casting carries the actuating-coil 30 of the contactor and has ears between which works the pivoted armature 32. The contactfingers 39 are pivoted to ears 37 carried by the armature. Contacts 55 of the auxiliary current-controlled switch are arranged below the contactors and may be bridged by a disk 57 on a rod 58 which carries two magnetic cores 59, 60, one fixed and one adjustable. These cores move in the field of an electro-magnet composed of a magnetic framework 62 and a coil which consists of a single turn of a heavy conductor 63. The upper end of the rod 58 carries a disk 65, beneath which extend heels 66 projecting from the armature 32. Instead of the coil 63, the actuating-winding may consist of three-quarters of a turn of the heavy conductor and a coil of finer wire which corresponds to the coils 17, 18, shown in Fig. 1. When the switch S., Fig. 1, is closed and the switch K moved to its first running position, current is supplied to the actuating-coils of the contactors L', L<2>; these contactors are actuated to close the motor circuit through all the resistance and the magnetizing-coils 19, 20, 21, 15 of the auxiliary switches. When the switch K is moved to its second position, the coil of contactor 1 is energized, and the contactor closes to cut out the resistance section R<1> provided that the current in the motor circuit has dropped to a safe value, thus permitting the switch 10 in the circuit of the coil of contactor 1 to close. As the switch K is moved forwards, the successive contactors are operated unless the motor current is sufficiently large to hold up one of the auxiliary switches 12, 13, 14, in which case the actuating-circuit for the next succeeding contactor is incomplete and the progression stops. As each contactor closes, it short-circuits a part of the coil of its auxiliary switch, and the controller K mav be thrown into its full ' on ' position at once, and the contactors will close automatically under the control of the auxiliary switches. If the motor current exceeds a safe value after all the resistance is cut out, the auxiliary switch 21 will rise and break the actuating-circuit of the contactor 4. The contactors then open in reverse order to cut in resistance until the safe value is reached. In the system shown in Fig. 5, a modified form of auxiliary switch is used and a dash-pot is attached. In this switch, as shown in Fig. 7, the core 59 moves in the field of a framework 62, bolted to the contactor frame, which serves to support the conductor 65 that carries the magnetizing - current. The holes in the frame through which the cores 59 and rod 58 pass may be lined with brass tubing to prevent sticking. One part of the dash-pot 73 is attached to the rod 58 to retard the fall of the core when it is released by the closing of the contactor. Removable disks 74 permit adjustments to be made for the switch to open or close at different values of the current in the conductor 65. As the controller K, Fig. 5, is moved through its forward positions the switches L<1>, L<2> connect the motor in circuit, and. if the current is normal, the resistance is cut out by the switches 1, 2, 3, 4, which act at predetermined intervals, as when one contactor closes, its auxiliary switch closes under the restraint of its dash-pot and completes the actuating-circuit of the next contactor. If the current is too high at any time, the last-closed contactor opens to insert resistance, and at the same time opens the shunt round the winding of the auxiliary switch which controls the actuating-winding of the previous contactor.