Patent GB-191007141-A (GB)
Title: Automatic Instantaneous Switches for Alternating and Direct Current Circuits.
Inventor: TAYLOR ALFRED MILLS
IPC: H01H77/06
Filed: 1910-03-22
Granted: 1911-05-22
Abstract: 7141. Taylor, A. M. March 22. [Cognate Applications, 7414/10, 9055/10, 9674/10, 10,728/10, 13,889/10, 14,773/10, 16,211/10, and 21,784/10.] Electro - magnetic switches; oil switches; sparking, preventing. - An automatic instantaneous switch operated by excessive momentary alternating or direct currents, consists of a hinged knife - blade b traversed by the main current and arranged in a powerful magnetic field between two fixed coils a, also traversed by the main current as shown in Fig. 1, or by a shunt current. The reaction of the current in the fixed coils upon that in the blade causes the blade to be repelled rapidly from the magnetic field, which also serves to blow-out the arc produced on opening the circuit. The whole switch is immersed in oil, and the arc is further subdivided and partly dissipated as heat by the provision of radial contacts e<1>, e<2>, &c. separated by insulating- barriers c<1>, c<2>, &c. and connected by strip resistances f<1>, f<2>, &c. These are thrown into the circuit in succession as the blade b opens, and may further divert the current through heatstorage water-tube resistances d', d<2>, &c. connected to further contacts prior to the final interruption of the circuit. A refractory follower g moves into the space vacated by the blade b, preventing the formation of a temporary vacuum between the contacts and crushing out the arc. The blade b, which is made as light as possible, is maintained in its extreme positions by a spring p passing across a dead-centre. If a short-circuit operating the switch passes away before the dead-point is reached, the spring automatically re-cioses the switch. The blade in the closed position is disconnected from all external operating-mechanism and left quite free to open automatically. As shown in Fig. 4, the blade is closed by a slotted link d, which is engaged by a pivoted hook h, k carried by the operating-member g. In the full-on position, a stop l tilts the hook, and a spring f returns the link d to the zero position, leaving the blade free for the automatic opening. The opening force, due to the reacting currents, may be magnified by the employment of transformers or reactances, which may be so arranged as to cause the main line current, under normal conditions, to be deflected out of the blade, or the fixed coils, or both. As shown in Fig. 1, a transformer secondary r is connected across the blade b, the primary s being placed in the main circuit. Upon the occurrence of a short-circuit, the current generated in the secondary r is discharged through the blade in the same direction as the main current, thus magnifying the opening-force. By the addition of a separately-fed compensating or over-compensating winding t upon the transformer r, s, the main line current during normal working can be deflected out of the blade b and through the winding r, thus enabling the mass of the blade to be further reduced. Several other arrangements for this purpose are described and illustrated. When used on direct-current circuits, the switch is provided with several blades connected electrically in parallel, and rigidly carried by a single shaft, as shown in Fig. 12. The magnetic field of the series or shunt deflecting-coils is concentrated by means of magnetic pieces arranged between each pair of blades, and a magnetic loop at the back of the switch panel. A switch for instantaneously closing an alternating or direct current circuit is also described. In this form, the knife-blade, when in the open position, is arranged in the field of a deflecting- coil, and is operated by discharging a large current from a special local circuit through the blade. The switch shown in Fig. 1 may be adapted for limiting the flow of current upon a short-circuit by substituting sections of a choking - coil either for the radial resistances f<1> &c. or the circumferential resistances d<1> &c. The coils are inserted progressively in steps, and the ends are so connected as to leave the mainline current established through them when the switch is in the open position.