US2446859A

US2446859A - Switch

Info

Publication number: US2446859A
Application number: US558666A
Authority: US
Inventors: Oliver C Traver; Ludwig S Walle
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1944-10-14
Filing date: 1944-10-14
Publication date: 1948-08-10
Anticipated expiration: 1965-08-10

Description

S- 1945- 0. c. TRAVER EI'AL 2,446,859

SWITCH Filed Ot. 14, 1944 amapznvwanr Fig 3.

Inventors: Oliver- C. Traver'. Ludwi $.Walle.

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Patented Aug. 10, 1948 SWITCH Oliver 0. Traver,

Drexel Hill, and Ludwig 8.

Walle, Lansdowne, Pa., assignors to General Electric Company, a corporation of New York Application October 14, 1944. Serial No. 558,866 7 Claims. (01. 200-147) Our invention relates to electric switches, more particularly to are extinguishing means for alter-- nating current electric switches, and has for its object simple and reliable arc extinguishing means providing for rapid movement of the arc and for a uniform voltage gradient between the two contacts oi the switch when the switch is being opened.

In the operation oi switches provided with arc runners, restriking of the are often occurs after the alternating voltage has passed through its instantaneous zero value. This restriking oi the arc is aggravated by the fact that the voltage gradient across the arc gap between the separated contacts is not uniform. but is greatest at points adjacent each contact or arcing horn with comparably great electrostatic stress at these points. This voltage gradient decreases toward the central region between the are runners, in which region the gradient is approximately uniform.

In carrying out our invention, we provide arc extinguishing means wherein the voltage gradient across the air path from one are runner to the other is substantially uniform, whereby restriking of the arc is prevented, and also elongation and extinguishment of the are are facilitated. In one form of our invention, we provide two are extinguisher plates made of insulating material, together with two arc runner members which are U-shaped with their sides or flanges extending toward each other on the outside of the plates of insulating material. Thus the inner surfaces of the flanges are covered by layers of electrically insulating material formed by the arc extinguisher plates whereby an are between the contacts is caused to be attached to the base portion of the U-shaped members. The base portions thus constitute arc runners. The are runner members are made of magnetic material and have the effect of transferring the regions of greatest voltage gradient to the edges or ends of the flanges of the arc runners on the outer sides of the arc extinguisher plates whereby the voltage gradient adjacent the arc runners is decreased and a substantially uniform voltage gradient is obtained across the air gap between the two plates from one are runner to the other. The greater voltage gradient at the exterior edges of the arc runner sides is not a disadvantage because of the adjacent plates of electrically insulating material which. in the absence of an arc, effectively electrically insulate the regions of greatest voltage gradient from the arc path between the two plates. It is, of course, obvious the arc runner I.

that additional insulation can be supplied on the sides of the arc chute, ii conditions should require.

For a more complete understanding of our invention, reference should be had to the accompanying drawing in which Fig. l is view in section taken along the line l-l of Fig. 2 looking in the direction of the arrows; Fig. 2 is a plan view of the device shown in Fig. 1; while Fig. 3 is a diagrammatic view illustrating the voltage gradients existing in the device oi Figs. 1 and 2,

Referring to the drawing, in one form of our invention we provide a pair of arc chute plates l and 2 made of a suitable heat refractory electricaily insulating material, such as an asbestos compound or hard fibre, these plates being arranged on opposite sides of the path of movement of a movable switch contact I. We also provide two U-shaped arc runner members I and I made of magnetic material, such as iron, which members embrace opposite sides or edges of the plates i and 2, as shown in Figs. 1 and 2.

It will be seen that the two U-shaped are runners l and 5 are positioned on their sides, with their base portions to and to extending crosswise between the arc chute plates and upward in diverging relation with respect to each other. The arc chute plates I and 2 are correspondingly shaped so that their ends are in abutting engagement with the base portion to and 5a which constitute arc runners. Also, it will be noted that the base portions to and to, because of their upwardly divergent relation, extend at an acute angle with the edges 8 and l of the respective arc runners l and I.

As thus assembled on the plates, the ends or edges of the flanges of the arc runner members are in spaced parallel relation with each other on each side, as indicated in Fig. 1, by the dotted lines 6 and l.

A stationary switch contact 0 is mounted on the lower end of the cross or base portion 8a. of I this lower end being closer to the edges 1 of the flanges of the arc runner. By means of suitable mechanism (not shown) the contact 3 is moved between its closed circuit position in engagement with the contact I and open circuit position 9, as shown in dotted lines in Fig. 1. Preferably, the contact a is mounted on a pivoted arm which is actuated by over-center spring snap means giving the contact a high speed movement from one position to the other. suitable circuit leads I and a are provided. When the movable contact is moved to its open circuit position 8 with current flowing through the switch. an arc is formed between the contacts, the are being prevented from striking to the flanges of the arc runner members by the arc chute plates l and 2. The are moves upward for elongation and extinguishment between the two are chute plates to the flnal elongated shape indicated by the dash-dot line ill, the opposite ends the are moving upward on the arc runners la and Do. This upward movement of the arc is accelerated by the magnetic field produced in the arc runner members I and l by the current in the arc. The are runner members other a path 0! low reluctance for this magnetic flux thereby increasing the amount of the flux. The are is acted upon by a force by reason of this magnetic flux which i'orce tends to move the arc to a position to surround the greatest possible amount oi magnetic flux whereby the arc is forced upward and elongated.

Referring to Fig. 3, in view oi the fact that the arc plays on or is attached to both are runner members at their base portions la and in during the opening of the switch, the two are runner members therefore are at the same potentials as the separated switch contacts and these potentials appear on the opposite edges 8 and 1 of the arc runners on each side of the plates l and 2. Therefore, the conventional voltage gradient conditions appear between these edges 6 and I, as indicated by the lines It. Thus, the voltage gradient is much greater adjacent each edge 0 and 1 than in the middle portion between these edges, as indicated by the greater number of lines at the edges. However, this greater voltage gradient adjacent the edges I and 1 is not disadvantageous because of the insulating arc chute plates I and 2 which electrically insulate the edges from any are in the space between the plates. In the arc space between the plates, however, a high voltage gradient adjacent each arc runner is prevented. By suitably spacing the ends I and 1 or the arc runner members, the voltage gradient in the arc space between the plates can be made substantially uniform throughout, whereby the most effective extingulshment oi the arc is obtained. More particularly, the arc is prevented from restriking after passing through the instantaneous zero value.

It will be understood that the spacing between the opposite edges 6 and I (Fig. 3) of the flanges of the arc runners is great enough to prevent the establishment of an are between these edges on the exterior of the arc extinguisher plates I and 2 even though this spacing between each pair of ends is substantially less than the spacing between the base portions or are runners themselves. In the arc space between the insulating plates the arc is initially established upon the separation oi the contacts and, because of the heated and contaminated condition oi the air between the plates, the arc may restrike across the greater space between the arc runners. whereas it would be impossible for an arc to be formed initially between each pair of edges 8 and I.

As the force urging the are up the runners is increased with an increase of magnetic flux below that arc, and as the magnetic flux is increased as the distance between the flanges oi the U-shaped arc runners l and I is increased, it will be apparent that the maximum emciency will occur when the width oi. the chute, e. g. between insulating plates l and 2, is made as s a as the amount of current to be interrupted will allow.

In the embodiment shown in Figs. 1, 2 and 3, two similar U-shaped arc runners, in accordance with our invention, are used. A single runner of this character can, however, be usefully applied where a lower efliciency is permissible.

It will also be understood that the entire sides and ends oi! the chute may be encased in insulation, if desired, and no live parts left exposed.

While we have shown a particular embodiment of our invention, it will be understood, of course, that we do not wish to be limited thereto since many modifications may be made, and we therefore contemplate by the appended claims to cover any such modifications as tall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent 01' the United States is:

1. In an electric switch, a substantially ushaped electrically conducting member having side flanges made of magnetic material and a base portion extending at an acute angle with the outer edges of the flanges, a stationary contact secured to the end of the base portion closer to the outer edges of said flanges, a movably mounted contact movable between the spaced side flanges oi! said U-shaped member to engage and disengage said stationary contact, and means for causing an arc between said contacts to be attached to the base portion of said U-shaped member and move on said base portion as an arc runner.

2. In an electric switch, a substantially U- shaped electrically conducting member having side flanges made oi magnetic material and a base portion of magnetic material extending at an acute angle with the outer edges 0! the flanges, a stationary contact secured to the end of the base portion closer to the outer edges of said flanges, a movably mounted contact movable between the spaced side flanges of said U-shaped member to engage and disengage said stationary contact, and means for causing the base portion oi said U-shaped member to function as an arc runner for an arc formed between said contacts comprising layers of electrically insulating material on the inner surfaces of said flanges.

3. In an electric switch, a pair of cooperating circuit interrupting contacts at least one of which is movable into an open circuit position, a pair of plates made of electrically insulating material forming arc chute members mounted in spaced parallel relation with each other on opposite sides oi the path of movement of the movable contact. a pair of spaced divergent arc runners positioned adjacent corresponding edges of said plates, a pair or electrically conducting members on the outer side oi each of said plates mounted in spaced relation with each other, the spacing between adjacent edges of said conducting members being sufllcient to prevent arc-over between their edges but substantially less than the spacing between the bases of the arc runner members. and electric connections between each opposite pair of said conducting members and the intermediate arc runner for reducing the voltage gradient in the regions adjacent said are runners in consequence of the region of maximum voltage gradient adjacent said members.

4. In an electric switch, a pair of cooperating circuit interrupting contacts at least one or which is movable into an open circuit position, a pair oi plates made of electrically insulating ma.- terial-i'orming arc chute members mounted in spaced parallel relation with each other on o9- maximum voltage gradient adjacent each of said members. i

5. In an electric switch, a pair of cooperating circuit interrupting contacts at least one of which is movable to an open circuit position, a pair of plates made of electrically insulating material i'orming arc chute members mounted in spaced pareilel relation with each other on opposite sides of the path of movement of the movable contact. and two spaced substantially U-shaped members made oi magnetic material, each of said members having a base portion constituting an arc runner extending across adjacent edges or said plates and having its flanges extending in the direction of the are between said contacts and on the outer sides of said plates the spacing of the adjacent edges of said flanges on the outer sides of the respective plates being such as to reduce the voltage gradient in the regions adjacent the arc runners in consequence of the regions maximum voltage gradient adjacent said edges.

6. In an electric switch, a pair oi cooperating circuit interrupting contacts at least one of which is movable to an open circuit position, a pair of plates made of electrically insulating material forming arc chute members mounted in spaced parallel relation with each other on opposite sides oi'the path of movement of the movable contact. and two substantially U-shaped members made of magnetic material having base portions constituting arc runners extending across opposite edges of said plates and having their flanges extending in the direction of the are between said contacts and on the outer sides 01' said plates, the spacing of the edges of the flanges of said are runner members being such as to reduce the voltage gradients in regions adjacent said arc runners in consequence of the regions of maximum voltage gradient adjacent said edges.

'7. In an electric switch, a pair 01' cooperating circuit interrupting contacts at least one of which is movable to an open circuit position, a pair of plates made of electrically insulating material forming arc chute members mounted in Spaced parallel relation with each other on opposite sides oi the path of movement of the movable contact. and two substantially U-shaped members made 01 magnetic material having base portions constituting arc runners extending across opposite edges of said plates and having their flanges extending in the direction of the are between said contacts and on the outer sides of said plates so as to straddle the arc and increase the magnetic flux moving the are along the arc runner, the spacin of the edges oi the flanges of said are runner members being such as to reduce the voltage gradients in regions adjacent said are runners in consequence oi the regions oi maximum voltage gradient adjacent said edges.

OLIVER C. TRAVER. LUDWIG S. WAILE.

REFERENCES CITED The following references are of record in the file 01' this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain 1911 Great Britain Mar. 10, 1932 Number Number Certificate of Correction Patent No. 2,446,859. August 10, 1948.

OLIVER C. TRAVER ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring eorrectlon as follows:

Column 3, line 72, for increased read decreased; column 4, line 75, before the word "forming strike out the hyphen;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 25th day of January, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.