Patent GB-190727038-A (GB)
Title: Improvements in Electric Motor Starting Devices.
Filed: 1907-12-06
Granted: 1908-12-07
Abstract: 27,038. British Thomson-Houston Co., [General Electric Co.]. Dec. 6. Switches; motor control systems.-An electric motor starting device, enabling automatic starting by means of a single controlling-switch, comprises, in addition to such switch, one or more electromagnetic resistance-controlling switches and an electricallyoperated master controlling element biassed to its 'off' position and arranged, when moved, to energize successively the resistance-controlling switches. Each of these switches after operation short-circuits the controlling-element, and is subsequently. energized independently of this element. The operating-means of the controlling arm and of all the resistance-controlling switches are de-energized by the last-operated electro-magnetic switch, which short-circuits all the resistance. The Figure shows a controlling- element 1 pivoted at 2 and connected to the core 5 of a solenoid 4, whereby it is moved over a series of contacts 3 against the action of a dash-pot 7, but adapted to fall freely to its 'off' position. The controlling-element 1, as it engages the contacts 3, successively energizes the electro-magnetic switches A ... E by completing circuits through the coils 9 between itself and a conductor 32, which is connected to the positive main through contacts 21 and a contactor 19 on the switch E. The controlling-element is connected to the negative main through conductors 35,37. The switches A ... D successively short-circuit sections R ... R<3> of resistance in the circuit of the armature A<1>, and also establish successive short-circuits on the controlling element 1 by connecting their magnet coils directly to the conductor 35 by means of contactors 11 and contacts 12. This avoids sparking at the contacts 3 by shunting current therefrom, and establishes an independent maintaining circuit for the switches A ... D. The controlling-element on its last contact energizes the lifting-coil 15 of the switch E. The resistances R ... R<4> are then short-circuited, and simultaneously the maintaining circuit of the switches A ... D is broken at the contacts 21. The operating-coil 4 of the controlling- element is supplied from the conductor 32, and consequently it also is de-energized by the closing of the switch E, and drops to its 'off' position. The system is set in operation by the closing of a switch 29, which establishes the circuit of a holding- coil 23 for the main switch F, and, through an insulated contactor 27 on the controlling-element 1, closes the circuit of a coil 22, which operates the switch F to close the main circuit through the motor armature A' and resistance R ... R<4> at the contacts 26. The conductor 31<1> is also energized, establishing the circuit of a holding-coil 16 for the switch E, and, through the contacts 21 and conductor 32, operating the solenoid 4. In the running position, the switches E, F alone are closed, being held by the coils 16, 23. The circuits of these coils are opened at the switch 29 to stop the motor. The arrangement of the contactor 27 on the element 1 prevents the closing of the main switch F in any but the 'off' position of the controlling-element.