Patent Application
20160233592
The present invention relates generally to electrical connections and, more particularly, to terminal strips with an improved creepage design.
Electrical connections having multiple electrically-isolated terminals, such as a terminal strip, fail when electric fields transmitted by components within the electrical connection exceed the dielectric strength of the electrically-insulating materials that isolate the terminals. Failure can occur in one or more of three modes; electrical breakdown along the insulating material surfaces between the terminals (creepage), electrical breakdown through the insulating material (bulk), or electrical breakdown across a gap between conductors (gap). Because electrical connections are readily designed to avoid electrical breakdown across a gap between conductors and the bulk dielectric strength of an insulating material is typically greater than the creepage dielectric strength of an insulating material, electrical connections can commonly fail by electrical breakdown along the insulating surfaces. Moreover, contamination (e.g. dirt, grease, oil) within the electrical connection further reduces the creepage dielectric strength, particularly after the electrical connection is placed in service.
Therefore, a need exists to provide an electrical connection such as a terminal strip in which the insulating components are configured to improve the creepage dielectric strength and limit contamination within the electrical connection.
A terminal strip and a method of improving a creepage dielectric strength of the same includes a base plate, a barrier, each constructed from an insulating material, and a plurality of terminals constructed from a conducting material. The terminals are connected to the base plate and spaced along a surface thereof. The barrier is disposed between adjacent terminals and configured such that the creepage dielectric strength of the insulating material between adjacent terminals is equal to or greater than a bulk dielectric strength of the insulating material between adjacent terminals.
Base plate 12 and cover 14 are constructed from an electrically-insulated material suitable for the environmental conditions under which the terminal strip will operate. In some embodiments, base plate 12 and cover 14 can be constructed from an electrically-insulating polymer having a bulk dielectric strength greater than or equal to 300 V/mil (11.8 kV/mm) and less than or equal to 500 V/mil (19.7 kV/mm) and a creepage dielectric strength greater than or equal to 3 V/m (0.1 kV/mm) and less than or equal to 5 V/mil (0.2 kV/mm). Using such a material, base plate 12 and cover 14 can be molded such that each includes a single molded structure that can be adapted, via machining or other post-molding operations, to house terminals 18a and 18b.
Barrier 24 extends from base plate 12 and is positioned between terminals 18a and 18b along base plate 12 to increase the creepage dielectric strength of terminal strip 10 between terminals 18a and 18b. Barrier 24 can be adapted to the geometry of terminal strip 10 by having a variety of shapes so that the distance, defined by line D1, between terminals 18a and 18b along the surfaces of base plate 12 and barrier 24 is greater than the minimum distance between terminals defined by Dm. In some embodiments, barrier 24 has a rectangular cross-section and extends from base plate 12 to form a protrusion (e.g. a fin-like shape). Preferably, barrier 24 includes structures 26a and 26b that have a rectangular cross-section. Structures 26a and 26b are joined to base plate 12 and spaced along base plate 24 such that void 27 is formed between structures 26a and 26b. Edges along line D1, such as the interfaces between structures 26a and 26b and base plate 24 or the exterior edges of structures 26a and 26b that protrude above top wall 19, can have a radius to further improve the creepage dielectric strength between terminals 18a and 18b. Structures 26a and 26b extend through apertures 34a and 34b formed in top wall 19. Apertures 34a and 34b are configured such that there is clearance between cover 14 and barrier 24, the clearance being selected based on the limits of manufacture.
Cover 14 can further include structure 38 that extends from top wall 19 towards base plate 12. Structure 38 is configured to cooperate with barrier 24 to further improve the creepage dielectric strength between terminals 18a and 18b by extending between structures 26a and 26b. Preferably, structure 38 is configured such that the clearance between structure 38 and base plate 12 accounts for manufacturing tolerances but otherwise extends the length of void 27 between structures 26a and 26b. As such, the surface path along which electrical breakdown occurs is defined by line D1.
Barrier 24, including structures 26a and 26b, and structure 38 can be formed from an electrically-insulating material suitable for the environmental conditions under which terminal strip 10 operates. Preferably, barrier 24 and/or structures 26a-b, and structure 38 are integrally constructed from base plate 12 and cover 14, respectively, and therefore, are constructed from the same electrically-insulating material.
Base plate 12 can include passage 40 extending therethrough and positioned relative to barrier 24 to allow contaminants to escape terminal strip 10. Preferably, passage 40 has a circular cross-section extending through base plate 12 at a location between structures 26a and 26b. Although the embodiment shown in
In other embodiments, structures 26a and 26b can be separate from base plate 12 and cover 14. As such, structures 26a and 26b can have a cross-like cross-section. Each leg of the cross-section can extend through one or both of base plate 12 and cover 14 in a manner similar to structures 26a and 26b extending through top wall 19 as depicted in
Seals 50a and 50b are disposed about cables 42a and 42b, respectively, at locations where cables 42a and 42b pass through conductor apertures 22a and 22c, respectively. Seals 50a and 50b can extend a length along conductors 42a and 42b, respectively, which is greater than the depth of conductor apertures 22a and 22b such that a portion of seals 50a and 50b protrude therefrom. Seals 50a and 50b are constructed from an elastomeric material suitable for the environmental conditions within which terminal strip 10 operates. In some embodiments, seals 50a and 50b are configured such that when cover 14 joins to base plate 12, seals 50a and 50b are compressed between respective surfaces of cover 14 and base plate 12 without damaging cables 42a and 42b. Such an arrangement prevents contaminants from entering terminal strip 10 through conductor apertures 22a and 22c.
Although the embodiment of terminal strip 10 shown in
In each embodiment, the creepage dielectric strength between terminals can be improved in the same manner. Referring again to
The following are non-exclusive descriptions of possible embodiments of the present invention.
A terminal strip according to an exemplary embodiment of this disclosure, among other possible things, includes a base plate constructed from an insulating material, a plurality of terminals constructed from a conducting material, and a barrier constructed from an insulating material. The plurality of terminals is attached to the base plate and spaced along a surface thereof. The barrier is disposed between adjacent terminals and configured such that a creepage dielectric strength of the insulating material between adjacent terminals is equal to or greater than a bulk dielectric strength of the insulating material between adjacent terminals.
The terminal strip of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
A further embodiment of the foregoing terminal strip can include a cover constructed from the insulating material. The cover can include a top wall spaced from and disposed opposite the base plate and a plurality of side walls, each side wall extending from the top wall towards the base plate. At least one of the side walls can be mechanically attached to the base plate. The base plate, the top wall, and the plurality of side walls can define a cavity containing the plurality of terminals.
A further embodiment of any of the foregoing terminal strips, wherein the cover can include an aperture extending through and defined by the top wall. The aperture can be adapted to receive the barrier, and the barrier can extend through the top wall at the aperture.
A further embodiment of any of the foregoing terminal strips, wherein the cover can include a cover barrier constructed from an insulating material and extending from the top plate towards the base plate. The cover barrier can be disposed between adjacent terminals.
A further embodiment of any of the foregoing terminal strips can include a plurality of conductor apertures, a plurality of electrical conductors, and a plurality of seals. Each conductor aperture can be defined by one of the side walls of the cover and the base plate. Each conductor can be aligned with one of the terminals. Each seal can surround a portion of one of the electrical conductors. Each conductor can extend through one of the conductor apertures and attach to one of the terminals. The seal can be configured to be received within one of the conductor apertures.
A further embodiment of any of the foregoing terminal strips, wherein the barrier can include a first structure and a second structure spaced from the first structure along the base plate.
A further embodiment of any of the foregoing terminal strips, wherein the cover can include a third structure extending into the cavity from the top wall towards the base plate and is disposed between the first and second structures.
A further embodiment of any of the foregoing terminal strips, wherein the cover can include a plurality of apertures extending through and defined by the top wall. Each aperture can be adapted to receive one of the first and second structures. The first and second structures can extend through the top wall at one of the plurality of apertures.
A further embodiment of any of the foregoing terminal strips, wherein the base plate can define a passage extending therethrough. The passage can be disposed between the first and second structures.
A further embodiment of any of the foregoing terminal strips, wherein the first and second structures can be integral with the base plate and the third structure can be integral with the cover.
A further embodiment of any of the foregoing terminal strips can include a plurality of barriers constructed from the insulating material and extending from the base plate. Each barrier can be disposed between adjacent terminals and can be configured such that the creepage dielectric strength of the insulating material between adjacent terminals is equal to or greater than the bulk dielectric strength of the insulating material between adjacent terminals.
A further embodiment of any of the foregoing terminal strips, wherein each barrier can include a first structure and a second structure spaced from the first structure along the base plate.
A further embodiment of any of the foregoing terminal strips, wherein the cover includes a plurality of third structures extending into the cavity from the top wall towards the base plate. Each third structure can be disposed between the first and second structures of each barrier.
A method of improving the dielectric strength of a terminal strip between adjacent terminals in accordance with an exemplary embodiment of this disclosure, among other possible things, includes providing a terminal strip having a base plate constructed from an insulating material, a plurality of terminals constructed from a conducting material, and a barrier constructed from an insulating material. Each terminal is attached to the base plate space along a surface thereof. The barrier is disposed between adjacent terminals and includes a first structure and a second structure spaced from the first structure along the base plate. The method further includes configuring the barrier such that a creepage dielectric strength of the terminal strip between adjacent terminals is equal to or greater than a bulk dielectric strength of the terminal strip between adjacent terminals.
The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
A further embodiment of the foregoing method can include providing a cover constructed from the insulating material. The cover can include a top wall spaced from and disposed opposite the base plate, a plurality of side walls extending from the top wall, and a plurality of third structures extending into a cavity defined by the base plate, top wall, and the plurality of side walls. At least one of the side walls can be mechanically attached to the base plate. The cavity can contain the plurality of terminals. Each third structure can be disposed between the first and second structures of each barrier.
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
