Heat sink for a thermally efficient busway joint pack

A busway joint pack for joining busway conductor sections has a heat sink assembly with an interstitial heat sink portion sized to fit between its connector plates; an exterior heat sink portion projecting beyond the exterior surface of a side panel of the joint pack; with the interstitial heat sink portion having thermal conduction to the exterior heat sink portion; to attain cooler operation. The heat sink may include thermally conductive dielectric materials or metals, or both, or other thermally conductive materials used with the thermally conductive dielectric materials.

FIELD OF THE INVENTION

The present invention relates generally to electrical distribution equipment and, more particularly, to thermally efficient busway joint packs.

BACKGROUND OF THE INVENTION

A busway system is a prefabricated modular electrical power delivery system which typically includes two or more busways, one or more busway joint packs, and may include a plurality of plug-in units. Each busway includes one or more phase-conductors and a housing. For example, in a three phase system, the busway can include three live phase-conductors or three live phase-conductors and one neutral-conductor, depending on the type of system architecture being employed. If required, various plug-in units or electrical components can be directly connected to one or more plug-in connection sites spaced along the busways to draw power. Each busway joint pack is used to physically and electrically connect two sections of busway together.

A common problem in busway systems is the management of the rise in temperature of the busway system within the busway joint pack. A rise in temperature within the busway joint pack limits the overall thermal performance of the busway system, which directly affects the required size of the busway and/or the size of the phase-conductors. Using larger phase-conductors to accommodate the rise in temperature at the busway joint pack increases the size of, and accordingly the costs of, the materials needed to make the busway system. As phase-conductors are typically made of copper and/or aluminum, which can be expensive, such a solution can be expensive. Another problem caused by the rise in temperature at the busway joint pack is a potential degradation of the busway system due to excessive heat, melting, deformation, etc.

Thus, a need exists for an improved apparatus and system. The present disclosure is directed to satisfying one or more of these needs and solving other problems.

SUMMARY

The present disclosure is directed to providing a heat sink for a thermally efficient busway joint pack. The thermally efficient busway joint pack is configured to passively transfer thermal energy or heat from its core to the outside of an exterior housing of the busway such that the thermal energy is lost or transferred to the surrounding environment, which reduces the internal temperature of the joint pack. The joint pack includes a pair of opposing conductive phase connector plates defining a space therebetween for accepting a busway phase conductor; a first side panel for the joint pack having an interior surface and an exterior surface; and a heat sink assembly for the joint pack having an interstitial heat sink portion sized to fit between the phase connector plates; an exterior heat sink portion projecting beyond the exterior surface of the side panel; with the interstitial heat sink being physically connected and hence thermally conductive to the exterior heat sink portion. The exterior heat sink portion may include cooling fins.

Each of the interstitial portions and the exterior heat sink portions may include metal or thermally conductive dielectric material, or both, with the metal clad in thermally conductive dielectric material where necessary. Other aspects of the invention may use micro heat pipe in place of metal, with similar thermally conductive dielectric material cladding.

The foregoing and additional aspects and embodiments of the present disclosure will be apparent to those of ordinary skill in the art in view of the detailed description of various disclosed examples and/or aspects, which is made with reference to the drawings, a brief description of which is provided next.

DETAILED DESCRIPTION

Although the invention will be described in connection with certain aspects and/or embodiments, it will be understood that the invention is not limited to those particular aspects and/or embodiments. On the contrary, the invention is intended to cover all alternatives, modifications, and equivalent arrangements as may be included within the spirit and scope of the invention as defined by the appended claims.

Referring toFIG. 1, an exemplary known busway system10is shown for general exposition of joint pack parts and the environment of the present invention. The busway system10includes a joint pack100, with its side panels removed for ease of view interior parts, a first busway section20a, and a second busway section20b. The first and the second busway sections20a,bare three pole busways and/or three phase busways. The first busway section20aincludes a busway housing21aand three phase-conductors25a-c. Each of the phase-conductors25a-care electrically insulated from each other and the housing21a. Each of the phase-conductors25a-chave at least one exposed end configured to physically and electrically mate with a first end100aof the joint pack100, as shown inFIG. 1.

Similarly, the second busway section20bincludes a busway housing21band three phase-conductors26a-c. Each of the phase-conductors26a-care electrically insulated from each other and the housing21b. Each of the phase-conductors26a-chave at least one exposed end configured to mate with a second opposing end100bof the joint pack100in the same manner as the three phase conductors25a-cmate with the first end100a. The joint pack100is configured such that when the first busway section20aand the second busway section20bare both physically engaged with the joint pack100, as shown inFIG. 1, the joint pack100electrically couples each of the three phase conductors25a-cwith a respective one of the phase-conductors26a-cof the second busway section20b. For example, the first phase-conductor25aof the first busway section20ais electrically connected with the first phase-conductor26aof the second busway section20b. As known in the art, busway sections will typically accommodate between one and four poles i.e., conductor phases. The joint pack components are coupled and compressed together with a bolt154and a nut155, and often a compression washer (not shown), compressing top and bottom plates151,152, respectively, as typical in the art.

Within the joint pack100there are pairs of opposing connector plates101,102, and103, where each pair corresponds to a particular electrical phase of the joint pack100and electrically joins the phase conductors, collectively25and26, of separate busway sections together. The first pair of opposing connector plates101corresponds to phase A, the second pair of opposing connector plates102corresponds to phase B, and the third pair of opposing connector plates103corresponds to phase C.

Each of the pairs of opposing connector plates101,102, and103defines a respective space therebetween for receiving a phase-conductor of a busway, such as one of the phase-conductors25a-c,26a-cshown inFIG. 1. The first pair of opposing connector plates101includes a first phase connector plate101aand a second phase connector plate101b. Similarly, the second pair of opposing connector plates102includes a first phase connector plate102aand a second phase connector plate102b, and the third pair of opposing connector plates103includes a first phase connector plate103aand a second phase connector plate103b.

Referring generally toFIGS. 2-3, an exterior view of a joint pack200according to one exemplary aspect of the present disclosure is shown. The joint pack200is a multi-phase joint pack, in this case, a three-phase joint pack. The joint pack200is generally cube-shaped having the first end200aand the second opposing end200bfor receiving sections of busway conductors, as is typical. The joint pack200has a first side panel202a(FIGS. 2 and 3), and a second opposing side panel202b(FIG. 2) providing exterior protective surfaces of the joint pack. Extending through the first side wall202ais an exterior heat sink portion204of a heat sink assembly, comprising thermally conductive dielectric material with integral heat sink cooling fins collectively206, as further explained below. Each side panel202aand202bhas an exterior surface213and an interior surface211of the side panels.

It will be appreciated that parts of the joint pack not necessary to an explanation of the present invention may be shown but not discussed herein and the typical function and composition of such parts will be understood by the person having ordinary skill in the art.

FIG. 3is an end view, e.g. end200awith one side panel202b, phantomed for clarity of explanation. At the right side of the drawing is a heat sink assembly214having interstitial portions216a,216b,216cbetween each pair of phase connector plates208a,208b;210a,210b; and212a,212b. Four insulating plates130a-dare placed so as to surround each phase connector plate pair. In this embodiment, the interstitial portions touch only the lower connector plate of the pair208b,210b,212b, respectively. Heat sink pads, collectively218, are compressed between each interstitial portion216and the corresponding top connector plate208a,210a,212a. The heat sink pads218may be thermally conductive dielectric material such as Gap Pad® material 5000S35 or 2200SF of appropriate thickness, such as from Berquist Company of Minnesota, and provide compressibility within the joint pack heat sink system if needed. The heat sink assembly214in this embodiment may be molded from all thermally conductive dielectric material such as CoolPoly® PPS D5108 from Cool Polymers, Inc. of Rhode Island.

By way of example, the cited heat sink pad material can have a thermal conductivity of 2 Watts per Kelvin per meter (W/m-K) at 125 mil thickness. The CoolPoly D5108, a thermally conductive polyphenylene sulfide (PPS) has a thermal conductivity of 10 W/m-K and a dielectric strength twenty nine kilovolt per millimeter (KV/mm). It will be appreciated by the person of skill in the art that various materials might be used as the thermally conductive dielectric material having a range of dielectric strength and thermal conductivity attributes suitable for the intended purpose.

Noting that the left and right sides of the joint pack are mirror images of one another, as seen on the left side ofFIG. 3, the side panel202ais in place and the interstitial portions collectively216of the heat sink assembly are joined to interior extension portions222a,222b, and222c, remaining inside of the side wall202ainterior surface. That is, the heat sink assembly of the present disclosure represents a joined mass where all parts are in contact to achieve thermal distribution conductively, i.e. through conduction, although within some components in some aspects of the heat sink assembly, such as the micro heat pipe aspects described below, convection may take place also. It will be appreciated that, while the present example shows an interstitial portion for each phase, the present invention contemplates that less than every phase may require an interstitial portion for adequate cooling of the joint pack. Reference may also be had toFIG. 4A, where the heat sink assembly214is shown separated from its joint pack. The interior extension portions collectively222may be of a thickness approximately equal to a busway conductor, i.e. the gap between the connector plate pair of the joint pack, for increased thermal and structural mass. The interior extension portions222then pass through an aperture in the side panel202aand broaden into the exterior heat sink portion204, which may be a rectangular plate-like mass, to extend beyond the exterior surface213of the side panels202and into the ambient environment.

As seen inFIG. 4Bthe interior surface227of the exterior heat sink portion204which abuts the exterior surface213of the side panels202(FIGS. 2-3) may have a molded in groove226for a sealing gasket (not shown) and tapped holes228at each corner for receiving mounting screws from inside the side panels202. The front view ofFIG. 4Cshows the exterior heat sink portion204with integrally molded cooling fins206.

As seen inFIG. 5, an alternative version of the heat sink assembly514may have interstitial portions,516a-c, formed of unclad bare metal, here of a uniform thickness to be placed between the connector plate pairs208,210,212(FIG. 3), without additional heat sink pads, and leading into broadened interior extension portions522which are clad in thermally conductive dielectric material and lead into the exterior heat sink portion504which comprises a plate-like mass of thermally conductive dielectric material substantially orthogonal to the interstitial portions516and interior extension portions522. The bare metal forming the interstitial portions continues out beyond the orthogonal plate of the exterior heat sink portion504to form cooling fins526also clad in thermally conductive dielectric material as shown by the cutaway at515. The cooling fins will be considered part of the exterior heat sink portion504. By utilizing bare metal and cladding it with thermally conductive dielectric material only where necessary for the dielectric properties, heat may be quickly conducted from the interior of the joint pack

As seen inFIG. 6, another alternative version of the heat sink assembly614may have interstitial portions,616a-c, formed of metal clad in thermally conductive dielectric material as shown by the cutaway at615, here of a uniform thickness to be placed between the connector plates208,210,212(FIG. 3), without additional heat sink pads, and leading without broadening, into the interior extension portions622which are also clad in thermally conductive dielectric material and lead into the exterior heat sink portion604which comprises a plate-like mass of thermally conductive dielectric material substantially orthogonal to the interstitial portions616and interior extension portions622. The flat metal bars forming the interior of the interstitial portions616continue out beyond the orthogonal plate of the exterior heat sink portion604as bare metal to form cooling fins626not clad in thermally conductive dielectric material. The cooling fins626will be considered part of the exterior heat sink portion626. The cooling fins may extend in various manners and include bends therein to increase thermal transfer. Mounting screws630are shown inserted into tapped holes at the corners of the exterior heat sink portion626for secure mounting to the side panels202(FIG. 2). Again, by utilizing bare metal and cladding it with thermally conductive dielectric material only where necessary for the dielectric properties, heat may be quickly dispersed to the ambient air.

As seen inFIG. 7A, another alternative version of the heat sink assembly714may have interstitial portions,716a-c, formed of unclad micro heat pipe material, here of a uniform thickness but much thinner that the distance between the connector plate pairs208,210,212(FIG. 3) due its superior heat transfer characteristics. An exemplary micro heat pipe material may be e.g., part number: MHP-2550A150A from Amec Thermasol Heat Management and Thermal Control Solutions. An additional heat sink pad, collectively717, is used as a compressible interface with the connector plates on each side of the micro heat pipe material. The interstitial portions716of unclad micro heat pipe material lead, without thickening or broadening, into the interior extension portions722which are clad in thermally conductive dielectric material and lead into the exterior heat sink portion704which comprises a plate-like mass of thermally conductive dielectric material substantially orthogonal to the interstitial portions716and interior extension portions722. Referencing alsoFIG. 7B, the bars of micro heat pipe material forming the interior of the interior extension portions722continue into a recessed area732of the exterior of the orthogonal plate of the exterior heat sink portion704to form short cooling fins collectively726within the recessed area732and still clad in thermally conductive dielectric material for increased protection of the micro heat pipe bars. The short cooling fins726will be considered part of the exterior heat sink portion704. As seen inFIG. 7A, like the disclosed example ofFIG. 4B, on the interior surface there is a molded-in groove727for a sealing gasket (not shown) and tapped holes728at each corner for receiving mounting screws from inside the side panels202(FIG. 2). By utilizing micro heat pipe material and cladding it with thermally conductive dielectric material only where necessary for structural or dielectric properties, or both, heat may be quickly dispersed to the ambient air.

A reduction of internal joint pack temperature is advantageous at least because it improves the thermal performance of the busway system, which directly affects the size of the phase-conductors needed in the busway sections. Thus, an improvement of thermal performance of the busway system allows for the use of phase-conductors having smaller cross-sectional areas and/or an overall smaller busway architecture. Smaller and/or lighter phase-conductors can significantly reduce the cost of fabrication as many phase-conductors are made from relatively expensive metals, such as copper and/or aluminum. As such, even a small reduction in cross-sectional area of a phase-conductor can result in a reduction in cost of a busway system.