GB2058463A

GB2058463A - Electric switching device with arc blowout means

Info

Publication number: GB2058463A
Application number: GB8029070A
Authority: GB
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1979-09-10
Filing date: 1980-09-09
Publication date: 1981-04-08
Also published as: NZ194794A; JPS6334178Y2; ES494876A0; CA1146199A; JPS5672421U; BE885172A; GB2058463B; KR830003796A; ES8200789A1; BR8005752A; KR830002551B1

Abstract

The invention relates to electric control devices, such as contactors or the like having arc blowout means comprising permanent magnets (17) so arranged on opposite sides of each contact pair as to provide intensified magnetic blowout fields concentrated in the spaces formed between the contacts when opened. In a contactor having the contacts 14, 15 in each pole unit arranged in two spaced- apart pairs, two permanent magnets 17 are disposed on the outside of the two spaced-apart contact pairs, and a third magnet 17 is disposed between the latter and is supported by the contact carrier (5) of the contactor for movement in unison therewith. <IMAGE>

Description

SPECIFICATION Electric control device with improved arc blowout means This invention relates generally to electric control devices, such as contactors or the like, and it relates particularly to an electric control device having improved arc blow out means.

The high-intensity arcs occurring between the contacts of electric control or switching devices during the switching of heavy electric loads have long been recognized as a problem causing pitting and erosion of the contact surfaces, and thus impairing effective circuit interruption and shortening the useful life of the contacts. It is known to combat this problem by means of magnetic fields used to "blow out" the arcs by causing them to move off the contacts and thus become extinguished or quenched.

The invention has for its principal object to provide an electric control device having improved arc blow out means, and the invention accordingly resides in an electric control device including a set of contacts, a movable member operable to open and close said contacts, and operating means for effecting contact opening and closing movements of the movable member, characterized by an array of permanent magnets arranged in such manner as to create magnetic fields which interact to produce blow-out fields of increased intensity at the contacts.

More specifically, theinventibn resides in an electric control device including at least one pair of cooperating contacts, a movable member operable to open and close the cooperating contacts, and means for subjecting electric arcs occurring between the contacts to magnetic blowout fields, characterized in that said means comprise permanent magnets which are disposed at opposite sides of said or each pair of cooperating contacts, and are arranged in such manner that opposite magnetic poles of the permanent magnets face toward, and are substantially aligned with, each other across the space formed between the associated pair of cooperating contacts when opened.

With the permanent mangets thus arranged, the magnetic fields of the individual magnets interact to produce intensified arc blowout fields which are concentrated in the regions where arcing takes place, and which therefore are highly effective in causing the arcs.to become quenched rapidly enough to substantially reduce contact erosion and, hence, increase the useful life of the contacts, and also to improve the current interruption capability of the device.

In a control device having double-break contacts, that is, two contact pairs which are spaced apart, two of the permanent magnets would be disposed on the outside of the two spaced-apart contact pairs, and a third permanent magnet would be disposed on the inside of, i.e.

between, the two contact pairs so as to be common to both.

If the control device with the jouble-break contacts is a contactor including a contact carrier having a contact-carrying portion which extends between the spaced contact pairs and supports the movable contacts thereof, the permanent magnet between the spaced contact pairs preferably is mounted on the contact-carrying portion of the contact carrier so as to be movable therewith, and to be moved into alignment with the two outer permanent magnets upon movement of the contact carrier from a contact closed to a contact open position thereof This movement of the inner permanent magnet relative to the outer ones is believed to cause the flux in the magnetic blowout fields to change in a manner aiding the arc blow-out effect.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an isometric view of an electric control device embodying the invention; Fig. 2 is a sectional view of the device taken generally along line Il-Il of Fig. 1; and Fig. 3 is a sectional view of the device taken generally along line Ill-Ill of Fig. 2.

Referring to the drawings, the electric control device to which the invention is shown applied therein is a contactor of a type such as described in detail in U.S. Patent No. 3,296,567, for example. The contactor, generally designated in the drawings with reference numeral 10, comprises a metallic base plate 2, a lower contactor section including an insulating housing 3, an upper contactor section including an insulating housing 4, and an arc hood 6 likewise made of a suitable insulating material. Seated in a depression formed in the upper side of the base plate 2 is a shock absorbing pad 9 which supports a generally U-shaped magnetic core 7 having a coil structure 1 disposed thereon.The lower contactor section is secured to the base plate 2 by means of screws 26 which extend upwardly through aligned openings in the base plate and in the insulating housing 3, and are threadedly engaged with tapped openings in the short legs of generally L-shaped, upright spring retainers 11 each having a spiral kickout or return spring 22 disposed thereabout. The lower insulating housing 3 has an interior surface portion (not shown) which overlies and cooperates with a lateral projection or projections (not shown) on the bight of the U-shaped core 7 to retain the latter in its proper position while the insulating housing 3 is securely held in place by the screws 26.

The upper contactor section including the housing 4 further includes a movable assembly comprising an insulating contact carrier 5, a magnetic armature 8 retained in a cavity on the lower side of the contact carrier by means of a pin 12 and cushioned by means of a shock absorbing pad 9a, and movable contact structures 13, 14 retained in an upper portion of the contact carrier 5. The movable assembly is guided in the insulating housing 4 for movement to a contact operated position occurring when the armature 8 is magnetically attracted to the magnetic core 7 upon energization of the coil structure 1, and for movement to a contact normal position occurring under the action of the return springs 22 upon deenergization of the coil structure 1.

The contactor 10 shown in the drawings is a three-pole device and, accordingly, has three stationary contact assemblies and three movable contact assemblies. Each stationary contact assembly comprises a pair of spaced stationary contacts 1 5 each secured, e.g. brazed, to a conductor 1 6 which, in turn, is connected to a terminal strap 18, and each movable contact assembly comprises a bridging contact 13 having thereon two contact buttons 14 cooperable with the stationary contacts 1 5. The three stationary contact assemblies are secured to the insulating housing 4 by means of bolts 51, and the three bridging contacts 1 3 are retained in windows formed in the contact carrier 5, and each of which windows contains also a contact-pressure spring 21 biasing the associated bridging contact in a direction toward the associated stationary contact assembly, thereby resiliently maintaining it engaged with the lower ledge of the associated window when the movable assembly is in its contact open position, as shown in Figs. 2 and 3, and yielding to apply contact pressure when the contacts 14 engage the contacts 1 5 during movement of the movable assembly toward its contact closed position and shortly before completion of such movement, there being the usual amount of overtravel of the contact carrier provided for the purpose of assuring proper engagement of the contacts 14 4 and 15 with one another.The upper contactor section comprising the housing 4, the stationary contact assemblies, and the contact carrier together with the armature and the movable contact assemblies thereon is secured to the lower insulating housing 3 by means of screws 27, and the arc hood 6 is removably fastened, e.g. with screws (not shown), to the upper insulating hosuing 4. As described thus far, the contactor 10 is conventional and operates in a manner well known in the art.

Referring to Fig. 2, it will be noted therefrom that the contactor is provided with arc blow out means which comprise permanent magnets 1 7 disposed at opposite sides of each of the two spaced pairs of cooperating contacts 14, 15, and are so arranged that opposite poles of the magnets 17 face toward, and in the open contact position are substantially aligned with, each other across the arc regions between the opened contacts. This arrangement results in intensive magnetic blowout fields which are concentrated in the respective arc or contact regions, with flux lines of the fields directed across the arc regions in directions perpendicular to the arcs occurring therein.

As seen from Fig. 2, two of the permanent magnets 1 7 are disposed on the outside of the two spaced pairs of cooperating contacts 14, 1 5 and supported in and by the arc hood 6, preferably being cemented thereto, and the third permanent magnet 1 7 is disposed on the inside of, that, is between the two spaced contact pairs, and is supported by the contact carrier 5, being mounted within the hollow of its contact-carrying portion which extends upward between the two spaced pairs of cooperating contacts 14, 1 5 so that movement of the contact carrier 5 from its contact closed position to its contact open position brings the inner magnet 1 7 into alignment with the outer magnets 1 7.Since this movement of the inner magnet 17 concurs with the movement of the contacts 14, the intensified magnetic blowout fields provided by the permanent magnets remain concentrated upon the arcing regions from the - moment electric arcs are drawn between the opening contacts until the arcs become quenched under the strong blowout forces to which they are subjected.

It will be appreciated that the above description of the magnetic blowout arrangement shown in Fig. 2 applies similarly to the blowout arrangements associated with the other pole units of the three-pole contactor illustrated, and that even though the invention is shown herein applied to a control device having normally open contacts, it is applicable just as well to control devices having normally closed contacts.

Moreover, it will be understood that the blowout fields of the contacts 14, 1 5 could be further augmented by means of additional permanent magnets suitable placed in, and secured to, the insulating arc hood.

Claims

1. An electric control device including a set of contacts, a movable member operable to open and close said contacts, and operating means for effecting contact opening and closing movements of the movable member, characterized by an array of permanent magnets arranged in such manner as to create magnetic fields which interact to produce blowout fields of increased intensity at the contacts.

2. An electric control device according to claim 1, wherein some of said contacts are movable contacts mounted on said movable member, characterized in that at least one of said permanent magnets is mounted on said movable member so as to move together therewith and thereby cause the blowout fields to intensify upon contact opening movement of the movable member.

3. An electric control device according to claim 1 or 2, characterized in that said permanent magnets are so arranged that the magnetic flux lines of said magnetic arc blowout fields extend perpendicular to the axis of contact movement.

4. An electric control device including at least one pair of cooperating contacts, a movable member operable to open and close the cooperating contacts, and means for subjecting electric arcs occurring between the contacts to magnetic blowout fields, characterized in that said means comprise permanent magnets which are disposed at opposite sides of said or each pair of cooperating contacts, are are arranged in such manner that opposite magnetic poles of the permanent magnets face toward, and are substantially aligned with, each other across the space formed between the associated pair of cooperating contacts when opened.

5. An electric control device according to claim 4, including at least two spaced-apart pairs of contacts, characterized in that two of said permanent magnets are disposed on the outside of the spaced-apart pairs of contacts, and another of said permanent magnets is disposed on the inside of and is common to both of said spacedapart pairs of contacts.

6. An electric control device according to claim 5, wherein each pair of contacts consists of a stationary contact and a movable contact, the movable contact being supported by said movable member on a contact-carrying portion thereof which extends between the spaced pairs of contacts, characterized in that the permanent magnet between the two spaced-apart contact pairs is mounted in said contact-carrying portion so as to move together therewith, the arrangement being such that contact opening movement of the movable member places the permanent magnet in said contact-carrying portion into alignment with the two permanent magnets on the outside of the spaced-apart pairs of contacts.

7. An electric control device according to claim 5 or 6, including an insulating arc hood covering said pairs of contacts, characterized in that the permanent magnets on the outside of the spaced apart pairs of contacts are supported on said insulating arc hood interiorly thereof.

8. An electric control device substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.