Controlled opening and closing switch with automatic opening in

Details Controlled opening and closing switch with automatic opening in Controlled opening and closing switch with automatic opening in

1984-08-14

1986-02-18

Broome, Harold

Electricity: magnetically operated switches, magnets, and electr

Electromagnetically actuated switches

Automatic circuit-interrupting devices

335 6, H01H 7702, H01H 7510

Patent

active

045715653

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to a switch designed to open and close under the control of a device such as an electromagnet and to open automatically in the event of overload current flow through the switch.
2. Description of the Prior Art
Switches such as contactors are already known in which the moving contact is directly connected to the armature of an electromagnet which controls the displacement of the moving contact against the action of restoring means, between a closed position and an open position of the contacts.
In some of these known contactors, means are also provided for initiating automatic opening of the contacts independently of the action of the electromagnet when the intensity of the current flow through the contactor oversteps a predetermined threshold value. These means can consist of a magnetic component which concentrates the field within a current loop in order to increase the intensity of the repulsion forces exerted on the moving contact. Automatic opening of the contacts is thus ensured when the current intensity exceeds a predetermined value which is usually of the order of thirty to forty times the rated value.
This type of switch thus has two different modes of operation as follows: the electromagnet; which opening of the contacts takes place automatically at the time of appearance of short-circuit currents, independently of the action of the electromagnet, even though the electromagnet is located in an active position in which the contacts should be closed.
A device of this type is described for example in French patent application No. 80 120 86 filed on May 30th, 1980 in the name of the present Applicant.
The device described in this patent application comprises a plurality of switches of the type consisting of a rigid contact bridge in cooperating relation with stationary contacts carried respectively by conductors which impart repulsion forces to the contact bridge. In addition, the central region of the bridge cooperates with a magnetic structure for subjecting the bridge to forces which compensate for the contact pressure below a predetermined threshold value. Above this value, the bridge is separated very rapidly from the stationary contacts.
This known device is so designed as to initiate the operation of the aforementioned magnetic structure only in order to produce an additional contact pressure force which is directly opposed to the electrodynamic repulsion forces.
This is subject to a disadvantage insofar as the speed of separation of the contacts (which is necessary when a short-circuit occurs) suffers from a balance of forces which is reduced by reason of the opposite directions in which the aforementioned additional force and the repulsion forces are exerted whereas it would be desirable to utilize all the forces which are present for the purpose of accelerating the speed of opening of the contact bridge and thus limiting the intensity of the short-circuit currents even more effectively.


SUMMARY OF THE INVENTION

The object of the present invention is to overcome the disadvantages of known designs by producing a controlled opening and closing switch with automatic opening so designed as to have a high breaking capacity (a presumed effective value of the order of 100 KA) and to guarantee non-welding of contacts. The magnetic structure of said switch takes part in the generation of forces applied in the direction of opening of the moving contact as soon as the increase in contact pressure is no longer necessary.
The switch contemplated by the invention is capable of opening and closing under the action of a control device such as an electromagnet and of opening automatically in the event of overload current flow through the switch. Provision is made for a stationary contact and for a moving contact subjected to the action of a magnetic component which serves to enhance the pressure applied by the moving contact on the stationary contact below a predetermined threshold value. Said switch further comprises a mechanic

REFERENCES:
patent: 2944129 (1960-07-01), Cole

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