Maximizing wall thickness of a Cu—Cr floating center shield component by moving contact gap away from center flange axial location

Abstract

The disclosed concept relates to vacuum interrupters having an electrically floating arc-enduring center shield component made out of an alloy of copper (Cu) and chromium (Cr), with or without additional minority alloying element or elements, and contact assemblies positioned in a vacuum envelope. In an open position, the contact assemblies include a contact gap formed there between. In accordance with the invention, contact assemblies are axially positioned such that the axial position of the contact gap aligns with a portion of the wall of the CuCr alloy-based center shield component that has a maximum thickness and outer diameter.

Claims

1. A vacuum interrupter, comprising: an insulating tube having an inner diameter; a vacuum envelope formed by the insulating tube; an arc-enduring floating center shield component comprised of CuCr alloy-based material positioned within the vacuum envelope, the floating center shield component comprising: a first portion of the floating center shield component having a first outer diameter greater than a second outer diameter of a remainder second portion of the floating center shield component; and a shield wall, having a first portion that corresponds to said first portion of the floating center shield component, the first portion of the shield wall having a first thickness greater than a second thickness of a remainder second portion of the shield wall, that corresponds to the remainder second portion of the floating center shield component; a center flange, having an inner diameter, to secure the floating center shield component to the insulating tube, wherein the first outer diameter of said first portion of the floating center shield component and the first thickness of said first portion of the shield wall extend beyond the inner diameter of the center flange toward the inner diameter of the insulating tube; a first contact assembly; a second contact assembly; and a contact gap formed between the first and second contact assemblies when said assemblies are axially in an open position, wherein an entire contact gap is positioned above a corresponding axial position of the center flange, and the entire contact gap is correspondingly aligned within said first portion of the floating center shield component that is located above the center flange, or wherein an entire contact gap is positioned below a corresponding axial position of the center flange, and the entire contact gap is correspondingly aligned within said first portion of the floating center shield component that is located below the center flange.

2. The vacuum interrupter of claim 1, wherein said first portion of the floating center shield component has an outer diameter that extends to or near the inner diameter of the insulating tube.

3. The vacuum interrupter of claim 1, wherein the contact gap is aligned with said first portion of the shield wall, which is located a distance away from where the center flange is attached to the shield wall.

4. The vacuum interrupter of claim 1, wherein the center flange has a ring-shaped opening formed therein.

5. The vacuum interrupter of claim 4, wherein the outer diameter of said first portion floating center shield component is greater than an inner diameter of the opening of the center flange.

6. The vacuum interrupter of claim 1, wherein the insulating tube is composed of ceramic.

7. The vacuum interrupter of claim 1, wherein the floating center shield component has connected thereto opposing ends composed of metal.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) 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 drawing in which:

(2) FIG. 1 is a sectional view of a vacuum interrupter and an arc-enduring CuCr alloy-based center shield component, in accordance with the prior art;

(3) FIG. 1A is a detail view of FIG. 1 of the contact gap portion, in accordance with the prior art;

(4) FIG. 2 is a sectional view of a vacuum interrupter and an arc-enduring CuCr alloy-based center shield component, in accordance with the prior art;

(5) FIG. 2A is a detail view of FIG. 2 of the contact gap portion, in accordance with the prior art;

(6) FIG. 3 is a sectional view of a vacuum interrupter and a non-arc-enduring (i.e., non-CuCr alloy-based) center shield component, in accordance with the prior art;

(7) FIG. 3A is a detail view of FIG. 3 of the contact gap portion, in accordance with the prior art;

(8) FIG. 4 is a sectional view of a vacuum interrupter and an arc-enduring CuCr alloy-based center shield component, in accordance with the disclosed concept;

(9) FIG. 4A is a detail view of FIG. 4 of the contact gap portion, in accordance with the disclosed concept;

(10) FIG. 5 is a sectional view of a vacuum interrupter and an arc-enduring CuCr alloy-based center shield component, in accordance with the disclosed concept; and

(11) FIG. 5A is a detail view of FIG. 5 of the contact gap portion, in accordance with the disclosed concept.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(12) The disclosed concept relates to vacuum interrupters employing a floating center shield assembly and contact assemblies positioned in a vacuum envelope. The center shield assembly includes a center shield component (or middle portion) composed of an arc-enduring CuCr alloy-based material, and opposing ends composed of metal. In an open position, the contact assemblies include an axial contact gap formed there between. In accordance with the invention, contact assemblies are axially positioned such that the axial position of the contact gap aligns with a portion of the wall of the center shield component that has a maximum thickness and outer diameter. In certain embodiments, the contact assemblies are axially positioned such that the contact gap axial position is located outside of or away from, e.g., above or below, the center flange axial position. In these embodiments, the contact gap aligns with a portion of the wall of the center shield component having a maximum thickness and outer diameter. That is, the thickness and outer diameter of the center shield is not limited by the diameter of the center flange or flange opening.

(13) There are various benefits to be derived from positioning the contact gap between the contact assemblies such as to align with a portion of the CuCr alloy-based center shield wall having a maximum thickness and outer diameter. For example, this alignment can prevent the center shield component from being burned through. Additional benefits can include one or more of the following:

(14) Enables the use of a larger diameter of the contact assemblies, thereby increasing the current interruption performance for a given vacuum interrupter size, which is typically defined by the diameter of the ceramic envelope;

(15) Enables, for a given contact diameter, a larger inner diameter of the center shield component, thereby enabling a larger clearance from the contact outer diameter to improve the dielectric (e.g., voltage withstand) performance for a given vacuum interrupter size; and

(16) Maximizes the unique capability of the center shield component in sharing the arcing duty from the contacts, thereby enabling the entire vacuum interrupter to endure more arc erosion by a higher number of shots and/or a longer duration of the shots, which improves the electrical life of the vacuum interrupter.

(17) As previously described, FIGS. 1 and 1A show a vacuum interrupter 10 employing a floating arc-enduring CuCr alloy-based center shield component, in accordance with the prior art, that has a space formed between the outer diameter of the center shield component and the inner diameter of the insulating tube, such that the center shield wall thickness and outer diameter is not maximized. FIGS. 2 and 2A show a vacuum interrupter 10 employing a floating arc-enduring CuCr alloy-based center shield component 24, in accordance with the prior art, that has a portion of the shield wall having a maximum thickness and outer diameter. However, this portion is created as a result of positioning a center flange, and the axial gap between the contact assemblies is not positioned to fully align with the portion of the center shield wall having the maximum thickness and outer diameter. FIGS. 3 and 3A show a vacuum interrupter 10 employing a floating center shield component composed of a non-arc-enduring (i.e., non-CuCr alloy-based) material, in accordance with the prior art, that has a shield wall of uniform thickness and outer diameter due to means of securing the non-arc enduring center shield component to the vacuum envelope.

(18) In accordance with the disclosed concept, there is provided a floating center shield component composed of an arc-enduring CuCr alloy-based material having the axial contact gap formed between the contact assemblies substantially entirely aligned with a portion of the wall of the center shield component that has a maximum thickness and outer diameter. Thus, the disclosed concept relates to eliminating empty space between the outer diameter of the wall of the center shield component and the inner diameter of the insulating tube (as shown in FIG. 1A), for increasing, e.g., maximizing, the thickness and outer diameter of at least a portion the wall of the center shield component; and for aligning the contact gap axial position with the portion of the shield wall having a maximum thickness and outer diameter.

(19) Thus, in accordance with the disclosed concept, the thickness and outer diameter of at least a portion of the wall of the center shield component is increased, e.g., maximized, and the distance or space between the outer diameter of the center shield component and the inner diameter of the insulating tube is decreased, e.g., minimized. In certain embodiments, the outer diameter of the wall of the center shield extends to, and is limited by, the inner diameter of the insulating tube, such that essentially the entire void or space is eliminated.

(20) Further, in accordance with the disclosed concept, the contact assemblies are positioned such that the contact gap axial position (formed between the contact assemblies) is outside of or away from, e.g., above or below, a center flange axial position. That is, the contact gap axial position, e.g., the width thereof, substantially fully aligns with the maximum thickness and outer diameter of the center shield wall.

(21) The center shield component (of the center shield assembly) is typically composed of copper-chromium (CuCr) alloy and has arc-erosion characteristics similar to those of the arcing contacts. In certain embodiments, the CuCr alloy includes additional minority alloying elements. In other embodiments, the CuCr alloy does not include additional minority alloying elements. Thus, as used herein, the term CuCr alloy-based refers to materials that include additional minority alloying elements and also to materials that do not include additional minority alloying elements. The CuCr alloy-based center shield component is positioned in close proximity to the contacts and is capable of participating actively in arcing, such that it shares the arcing mitigating duties with the contacts. Since the center shield component exhibits arc-erosion characteristics, a larger diameter of the contacts can be used within any given diameter of the ceramic envelope, as compared to the diameter of contacts used with a passive center shield component that does not exhibit arc-erosion characteristics, e.g., is composed of a non-arc-enduring CuCr center material, such as copper (in the absence of chromium) or stainless steel.

(22) Generally, an electrically floating CuCr alloy-based center shield component is secured to the vacuum interrupter envelope with a flange. The flange can be more susceptible to being braze-joined (as shown in FIGS. 1 and 1A) or can be of a snap-ring design, for securement to the ceramic insulating casing. A cylindrically-shaped CuCr alloy-based center shield component can be slid into a ring-shaped flange opening. The maximum outer diameter of the CuCr alloy-based center shield component is limited by the internal diameter of the flange. The maximum outer diameter of the CuCr alloy-based shield component may be no more than a few thousands of an inch larger, e.g., for press fitting, than the smallest value of the inner diameter of the flange. Thus, the maximum diameter of the contacts positioned within the CuCr alloy-based center shield component is limited by the diameter that can be fitted inside the CuCr alloy-based center shield component, without risking the wall of the CuCr alloy-based center shield component being burned through after a significantly large number of shots of fault currents of a high amplitude, and/or long arcing time while enduring large asymmetric currents.

(23) FIG. 4 is a schematic that illustrates a vacuum interrupter 100 employing a floating center shield assembly including a center shield component composed of CuCr alloy-based material, in accordance with certain embodiments of the disclosed concept. FIG. 4 includes the insulating tube 12, consisting of two cylindrical pieces, end seals 51 and 52, vacuum envelope 50, arc-enduring CuCr center shield component 24 and opposing metal end components 13, 15 of the center shield assembly, center flange 25, overlaps 37 and 38, first electrode assembly 20, second electrode assembly 22, vacuum envelope 50, bellows 28, bellows shield 48, first electrode contact 30, first terminal post 31, first vapor shield 32, second electrode contact 34, second terminal post 35, second vapor shield 36, end shield 58, and contact gap 14, as shown in FIG. 1. As shown in FIG. 4, the contact gap axial position 14 (formed between the first and second electrode assemblies 20, 22) is located below the center flange axial position 112. As a result, the entire contact gap 14 is in alignment with a portion of the shield wall 29 (shown in FIG. 4A) having a maximum thickness and outer diameter, of the arc-enduring CuCr center shield component 24.

(24) FIG. 4A is a detail view of the contact gap portion of the vacuum interrupter 100 as shown in FIG. 4. FIG. 4A shows that the outer diameter of the arc-enduring CuCr alloy-based center shield component 24 is not limited by the inner diameter of the center flange 25. As a result, the portion of the shield wall 29 having maximum thickness and outer diameter corresponds to, and fully aligns with, the contact gap axial position 14. The maximum thickness and outer diameter of the shield wall 29 is only limited by the inner diameter 23 of the insulating tube 12 and not limited by the opening of the center flange 25.

(25) FIG. 5 is a schematic that illustrates a vacuum interrupter 100 employing a floating center shield assembly including a center shield composed of CuCr alloy-based material, in accordance with certain embodiments of the disclosed concept. FIG. 5 includes the insulating tube 12, consisting of two cylindrical pieces, end seals 51 and 52, vacuum envelope 50, arc-enduring CuCr center shield component 24 and opposing metal end components 13, 15 of the center shield assembly, center flange 25, overlaps 37 and 38, first electrode assembly 20, second electrode assembly 22, vacuum envelope 50, bellows 28, bellows shield 48, first electrode contact 30, first terminal post 31, first vapor shield 32, second electrode contact 34, second terminal post 35, second vapor shield 36, end shield 58, and contact gap 14, as shown in FIG. 1. As shown in FIG. 5, the contact gap axial position 14 (formed between the first and second electrode assemblies 20, 22) is located above the center flange axial position 112. As a result, the entire contact gap 14 is in alignment with a portion of the shield wall 29 (as shown in FIG. 5A) having a maximum thickness and outer diameter, of the arc-enduring CuCr center shield component 24.

(26) FIG. 5A is a detail view of the contact gap portion of the vacuum interrupter 100 as shown in FIG. 5. FIG. 5A shows that the outer diameter of the arc-enduring CuCr alloy-based center shield component 24 is not limited by the inner diameter of the center flange 25. As a result, the portion of the shield wall 29 of the arc-enduring CuCr center shield component 24 that corresponds to the contact gap axial position 14, has a maximum thickness and outer diameter, i.e., only limited by the inner diameter 23 of the insulating tube 12 and not limited by the opening of the center flange 25.

(27) 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.