Field
The disclosed concept relates to vacuum switching apparatus such as, for example, vacuum switches including a vacuum envelope such as, for example, vacuum interrupters. The disclosed concept also pertains to electrical contacts for vacuum interrupters.
Background Information
Vacuum interrupters include separable main contacts located within an insulated and hermetically sealed vacuum chamber. The vacuum chamber typically includes, for example and without limitation, a number of sections of ceramics (e.g., without limitation, a number of tubular ceramic portions) for electrical insulation capped by a number of end members (e.g., without limitation, metal components, such as metal end plates; end caps; seal cups) to form an envelope in which a partial vacuum may be drawn. The example ceramic section is typically cylindrical; however, other suitable cross-sectional shapes may be used. Two end members are typically employed. Where there are multiple ceramic sections, an internal center shield is disposed between the example ceramic sections.
Some known vacuum interrupters include a radial magnetic field generating mechanism such as, for example and without limitation, a spiral electrical contact or a contrate cup, designed to force rotation of the arc column between the pair of electrical contacts interrupting a high current, thereby spreading the arcing duty over a relatively wide area. These vacuum interrupters suffer from a number of disadvantages. For example, as the electrical contacts experience repeated interruption of relatively high fault currents, the individual petals of the electrical contact begin to “bridge.” More specifically, the individual petals of the electrical contact begin their life spaced apart from each other by slots that force the arc column to spread over the contact. As the electrical contact experiences repeated interruption of relatively high fault currents, the heavy columnar arcing causes the metal of the electrical contact to melt such that the spacing between the petals decreases, and is eventually bridged. As a result, the bridged electrical contact is prevented from allowing the arcing duty to spread over a relatively wide area. Thus, the bridged electrical contact results in the arcing being localized in the center of the electrical contact. This undesirably shortens the life of the electrical contact due to the inability to adequately interrupt the relatively high fault currents.
There is thus room for improvement in vacuum switching apparatus and in electrical contacts therefor.
These needs and others are met by embodiments of the disclosed concept, which are directed to a vacuum switching apparatus and electrical contact therefor in which at least one arc spinning portion of the electrical contact narrows from a corresponding pair of adjacent arcing surfaces of the electrical contact to an interior thereof in a direction opposite an opposing electrical contact.
In accordance with one aspect of the disclosed concept, an electrical contact for a vacuum switching apparatus is provided. The vacuum switching apparatus includes a second electrical contact. The electrical contact comprises: a body having a center point and a periphery, the body comprising: a plurality of arcing surfaces structured to face in a first direction toward the second electrical contact and structured to move into and out of engagement with the second electrical contact, and a plurality of arc spinning portions each defining a slot extending inwardly from the periphery generally toward the center point, the plurality of arc spinning portions generally separating the plurality of arcing surfaces from one another. At least one arc spinning portion narrows from a corresponding pair of adjacent arcing surfaces of the body to an interior thereof in a second direction opposite the first direction.
In accordance with another aspect of the disclosed concept, a vacuum switching apparatus comprises: a first electrical contact; and a second electrical contact, wherein at least one of the first electrical contact and the second electrical contact comprises: a body having a center point and a periphery, the body comprising: a plurality of arcing surfaces facing in a first direction toward the other of the first electrical contact and the second electrical contact and being structured to move into and out of engagement therewith, and a plurality of arc spinning portions each defining a slot extending inwardly from the periphery generally toward the center point, the plurality of arc spinning portions generally separating the plurality of arcing surfaces from one another. At least one arc spinning portion narrows from a corresponding pair of adjacent arcing surfaces of the body to an interior thereof in a second direction opposite the first direction.
A full understanding of the disclosed concept can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:
As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality).
As employed herein, the statement that two or more parts are “connected” or “coupled” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts.
As employed herein, the statement that two or more parts or components “engage” one another shall mean that the parts touch and/or exert a force against one another either directly or through one or more intermediate parts or components.
The arc spinning portions 130,140,150 each define a slot extending inwardly from the periphery 106 generally toward the center point 104. When the spiral contacts 100,200 move away from one another to disconnect power in the associated electrical circuit, the arc spinning portions 130,140,150 force the arc that is generated to spread across the first spiral contact 100 so that the arcing energies are not localized near the center point 104 of the spiral contact 100. In this manner, the life of the spiral contact 100 is lengthened. As will be discussed in greater detail hereinbelow, the arc spinning portions 130,140,150 narrow from the arcing surfaces 110,112,114 of the body 102 to an interior thereof in a second direction 122 (
In spiral contacts (not shown) in which the slots have been bridged, extensive post-mortem analysis has found that bridging begins at the corresponding arcing surfaces and progresses toward, but never reaches, the opposite side of the contact. That is, the bridged portions (e.g., the portions across the original slots that have been partially filled with solidified molten metal of the contact material) narrow from the portion of the slots near the arcing surfaces in a direction away from the opposite electrical contact. Accordingly, by having the width of the arc spinning portions 130,140,150 be relatively wide proximate the arcing surfaces 110,112,114 and narrow from the arcing surfaces 110,112,114 of the body 102 to an interior thereof in the direction 122, the onset of bridging is advantageously prolonged, while strength is not significantly compromised.
More specifically, and with reference to
Referring to
Stated differently, the arc spinning portions 130,140,150 each have a first width between the respective arcing surfaces 110,112,114 and a second width in the interior of the body 102 that is less than the first width. For example, in the depicted top plan view of
After repeated interruption of relatively high fault currents, the time until bridging begins in the spiral contact 100 is advantageously lengthened, as compared to spiral contacts (not shown) with arc spinning portions that have consistent, relatively narrow widths. That is, because bridging begins between the arcing surfaces 110,112,114 and as a result of the relatively wide first widths 166 (and the first widths of the arc spinning portions 130,150), the melted portions (i.e., after repeated interruption of relatively high fault current) of the body 102 have a greater distance to bridge across. Furthermore, because the arc spinning portions 130,140,150 narrow from the arcing surfaces 110,112,114 of the body 102 to an interior thereof in the direction 122, bridging in the interior of the body 102 is not significantly affected and mechanical strength of the spiral contact 100 is not significantly compromised. More specifically, because bridging decreases from the arcing surfaces 110,112,114 in the direction 122, the relatively narrow second widths 168 (and the second widths of the arc spinning portions 130,150) do not affect the onset of bridging. Additionally, mechanical strength of the spiral contact 100 is not significantly compromised because the portions of the arc spinning portions 130,140,150 with the relatively narrow second widths 168 (and the second widths of the arc spinning portions 130,150) provide a relatively secure connection to the center of the body 102.
The disclosed concept applies to spiral contacts (i.e., the spiral contacts 300,400 (
Additionally, as seen in the non-limiting example of
More specifically, and with reference to
The disclosed concept is applicable to any suitable alternative spiral contact (i.e., the spiral contacts 500,600 (
Additionally, as seen in the non-limiting example cross-sectional profile of
Accordingly, it will be appreciated that the disclosed concept provides for an improved (e.g., without limitation, longer lasting) vacuum switching apparatus 2 and electrical contact 100,200,300,400,500,600 therefor, which among other benefits, prolongs the life of the electrical contact 100,200,300,400,500,600 by narrowing an arc spinning portion 130,140,150, 330,340,350,360,430,440,450,460,540,640 of the electrical contact 100,200,300,400,500,600 from a corresponding pair of adjacent arcing surfaces 110,112,114,310,312,314,316,410,412, 414,416,512,514,612,614 of the electrical contact 100,200,300,400,500,600 to an interior thereof in a direction opposite an opposing electrical contact.
While specific embodiments of the disclosed concept have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.
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Entry |
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European Patent Office, “International Search Report and Written Opinion”, PCT/US2016/047449, Oct. 26, 2016, 12 pp. |