Patent Description:
The present invention relates to inductor assemblies and, more particularly, to inductor assemblies including inductor coils and methods for making the same.

Inductors coils are used in the AC power networks for power factor correction, voltage regulation, reduction of di/dt, and protection of downstream equipment. Published patent documents <CIT>, <CIT> and <CIT> each discloses a known inductor assembly.

According to embodiments of the invention, an inductor assembly includes a coil including a spirally wound metal foil.

In some embodiments, the coil has a longitudinal coil axis and a radial coil thickness, the metal foil has a foil width extending substantially parallel to the coil axis, and the foil width is greater than the coil thickness.

In some embodiments, the metal foil has a foil thickness in the range of from about <NUM> to <NUM>.

In some embodiments, the coil includes an electrical insulator layer spirally co-wound with the metal foil.

In some embodiments, the electrical insulator layer has a thickness in the range of from about <NUM> to <NUM>.

In some embodiments, the ratio of the foil width to the foil thickness is in the of from about <NUM> to <NUM>.

According to some embodiments, the metal foil and the electrical insulator layer are not bonded to one another across their widths.

In some embodiments, the coil has a substantially cylindrical outer profile.

According to some embodiments, the inductor assembly includes an electrically insulating epoxy resin surrounding and engaging the coil.

In some embodiments, the inductor assembly further includes a second coil including a second spirally wound metal foil, and the epoxy resin surrounds and engages the second coil, and is interposed between the first and second coils.

According to some embodiments, the inductor assembly includes an enclosure defining an enclosed chamber, wherein the coil is disposed in the chamber.

In some embodiments, the inductor assembly includes at least one mounting bracket supporting the enclosure and the coil.

According to some embodiments, the inductor assembly includes a terminal bus bar electrically connected to the metal foil and including a terminal, and an electrically insulating heat shrunk tube surrounding a portion of the terminal bus bar.

In some embodiments, the coil includes a second metal foil spirally co-wound with the first metal foil to form a multilayer conductor.

In some embodiments, the coil includes an electrical insulator layer spirally co-wound with the first and second metal foils.

According to some embodiments, the first and second metal foils and the electrical insulator layer are not bonded to one another across their widths.

According to some embodiments, the coil has a coil longitudinal axis, the coil has an innermost winding of the metal foil and an outermost winding of the metal foil, the inductor assembly includes a first terminal bus bar connected to the innermost winding and projecting outwardly from an axial end of the inductor assembly, and the inductor assembly includes a second terminal bus bar connected to the outermost winding and projecting outwardly from the axial end of the inductor assembly.

According to embodiments of the invention, a multi-unit inductor system includes first and second inductor assemblies. The first inductor assembly includes a first coil, the first coil including a spirally wound first metal foil. The second inductor assembly includes a second coil, the second coil including a spirally wound second metal foil. The first coil is electrically connected to the second coil.

In some embodiments, the first coil has a first coil longitudinal axis and the second coil has a second coil longitudinal axis. Each of the first and second inductor assemblies includes: a first terminal bus bar connected to the coil thereof and projecting outwardly from an axial end of the inductor assembly; and a second terminal bus bar connected to the coil thereof and projecting outwardly from the axial end of the inductor assembly. The first and second inductor assemblies are positioned side-by-side and the first terminal bus bar of the second inductor assembly is electrically connected to the second terminal bus bar of the first inductor assembly.

According to embodiments of the invention, a method for forming an inductor assembly includes spirally winding a metal foil into the form of a coil.

In some embodiments, the method includes spirally co-winding an electrical insulator sheet with the metal foil.

According to some embodiments, the metal foil and the electrical insulator sheet are not bonded to one another during the step of co-winding the electrical insulator sheet and the metal foil.

Embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:.

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which illustrative embodiments of the invention are shown. In the drawings, the relative sizes of regions or features may be exaggerated for clarity.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.

Spatially relative terms, such as "beneath", "below", "lower", "above", "upper" and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The device may be otherwise oriented (rotated <NUM>° or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms "includes," "comprises," "including" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Typical inductance coil designs use a conductor which is insulated using a varnish and is turned around a spool. However, such designs typically will not be able to withstand significant transient overvoltages between the turns of the coil and will be large in size, as the load current requires a significant cross-section of the conductor. In that case, there is a significant space lost in between the turns of the conductor, as it has a round shape. If an insulation cover were mounted over the coil to ensure that it can withstand very high transient overvoltages, then the overall coil assembly would become even larger in size. Further, vibration might be an issue as there is minimal contact between the turns of the coil, allowing some possible movement.

With reference to <FIG> a dual coil inductor assembly <NUM> according to embodiments of the invention is shown therein. The inductor assembly <NUM> has a longitudinal axis L-L.

The inductor assembly <NUM> includes an enclosure <NUM>, a pair of axially spaced apart support bases <NUM>, a support shaft <NUM>, an electrically insulating fitting <NUM>, a pair of bushings <NUM>, potting <NUM>, insulation sleeves or tubes <NUM>, a first coil assembly <NUM>, and a second coil assembly <NUM>.

The bases <NUM> and shaft <NUM> are metal (in some embodiments, aluminum). The shaft <NUM> is supported by and affixed to the bases <NUM> at either end.

The fitting <NUM> is mounted around the shaft <NUM>. The fitting <NUM> may be formed of a plastic or polymeric material such as Polyethersulfone with a dielectric strength in the range of from about <NUM> to <NUM> kV/mm.

The coil assemblies <NUM>, <NUM> (described in more detail below) are mounted on the fitting <NUM> and the shaft <NUM>. The coil assemblies <NUM>, <NUM> each include a pair of terminal bus bars <NUM>, <NUM>, <NUM>, <NUM>.

The enclosure <NUM> includes a pair of laterally opposed shells <NUM> and a pair of axially opposed end plates <NUM> that are fastened together to form the enclosure <NUM>. The enclosure <NUM> defines an internal cavity or chamber <NUM> within which the support shaft <NUM>, the fitting <NUM>, the potting <NUM>, the insulation tubes <NUM>, the first coil assembly <NUM>, and the second coil assembly <NUM> are disposed and contained. Four terminal openings <NUM> are defined in the enclosure <NUM> and communicate with the chamber <NUM>.

The enclosure components <NUM>, <NUM> may be formed of any suitable material. In some embodiments, the enclosure components <NUM>, <NUM> are formed of an electrically insulating polymeric flame retardant material such as Noryl N190X by SABIC with a dielectric strength of about <NUM> kV/mm.

Each of the four insulation tubes <NUM> surrounds a length of a respective terminal bus bar <NUM>, <NUM>, <NUM>, <NUM> extending through the chamber <NUM>, through a terminal opening <NUM>, and beyond the terminal opening <NUM> a prescribed distance. The tubes <NUM> may be formed of any suitable material. In some embodiments, the tubes <NUM> are formed of an electrically insulating polymeric material. In some embodiments, the tubes <NUM> are formed of an electrically insulating elastomeric material. In some embodiments, the tubes <NUM> are formed of an electrically insulating heat shrinkable polymer (e.g., elastomer) that has been heat shrunk about the corresponding terminal bus bar <NUM>, <NUM>, <NUM>, <NUM>.

The potting <NUM> fills the void space within the chamber <NUM> that is not occupied by the other components. The potting <NUM> may formed of any suitable material. The potting <NUM> is electrically insulating. In some embodiments, the potting <NUM> is formed of a material having a breakdown voltage of at least <NUM> kV/mm. In some embodiments, the potting <NUM> is an epoxy resin or a Polyurethane resin.

Each bushing <NUM> is annular and is sandwiched or interposed between an end plate <NUM> and the adjacent base <NUM> and mounted on the shaft <NUM>. The bushings <NUM> may be formed of any suitable material. In some embodiments, the bushings are formed of a resilient polymeric material. In some embodiments, the bushings <NUM> are formed of an elastomer and, in some embodiments, a silicone elastomer or rubber.

The coil assembly <NUM> includes a multi-layer coil <NUM>, an inner terminal bus bar <NUM>, and an outer terminal bus bar <NUM>.

The coil <NUM> is an air core coil. The coil <NUM> has a coil axis A-A and axially opposed ends 130A, 130B. The coil <NUM> includes an electrically conductive conductor sheet, strip or foil <NUM> and an electrically insulative insulator strip or sheet <NUM>. The foil <NUM> and sheet <NUM> are spirally co-wound or wrapped about the axis A-A to form windings <NUM>. The windings <NUM> extend progressively from an innermost winding 136E of the conductor foil <NUM> in an inner passage <NUM> to an outermost winding 136F of the conductor foil <NUM> on the outer diameter of the coil <NUM>. Each winding <NUM> is radially superimposed on, stacked on, or wrapped around the preceding winding <NUM>.

The conductor foil <NUM> has opposed side edges 132A that are axially spaced apart along the coil axis A-A and extend substantially parallel to one another. The conductor foil <NUM> is spirally wound such that each edge 132A remains substantially in or proximate a single lateral plane E-E (<FIG>) throughout the coil <NUM> from the winding 136E to the winding 136F. That is, the conductor foil <NUM> is maintained in alignment with itself and is spirally, not helically, wound.

According to some embodiments, the coil <NUM> includes at least <NUM> turns or windings from the winding 136E to the winding 136F and, in some embodiments, from about <NUM> to <NUM> turns. It will be appreciated that in the figures the layers <NUM>, <NUM> and turns of the coils <NUM>, <NUM> are not specifically shown or, in <FIG>, are only partially shown. As such, the depictions of the layers <NUM>, <NUM> in the drawings may not be to scale with regard to the number of turns, the thicknesses of the layers, or the spacing between layers.

The conductor foil <NUM> may be formed of any suitable electrically conductive material. In some embodiments, the conductor foil <NUM> is formed of metal. In some embodiments, the conductor foil <NUM> is formed of copper or aluminum.

The insulator sheet <NUM> may be formed of any suitable electrically insulative material. In some embodiments, the insulator sheet <NUM> is formed of a polymeric material. In some embodiments, the insulator sheet <NUM> is formed of polyester film. In some embodiments, the insulator sheet <NUM> is formed of a material having a breakdown voltage of at least <NUM> kV/mm and, in some embodiments, in the range of from about <NUM> kV/mm to <NUM> kV/mm.

The coil <NUM> is generally tubular. In some embodiments, the outer profile of the coil <NUM> is substantially cylindrical and is substantially circular in lateral cross-section.

The coil <NUM> has a thickness CT (<FIG>), a length CL (<FIG>; parallel with the coil axis L-L), and an outer diameter CD (<FIG>). The thickness CT is the radial distance from the innermost conductor winding 136E to the outermost conductor winding 136F in a lateral plane N-N (<FIG>) orthogonal to the coil axis A-A.

According to some embodiments, the coil <NUM> is generally cylindrical with a length CL greater than its outer diameter CD. According to some embodiments, the ratio CL/CD is at least <NUM> and, in some embodiments, is in the range of from about <NUM> to <NUM>.

<FIG> are fragmentary views of the conductor foil <NUM> and the insulator sheet <NUM> laid flat (e.g., prior to winding into the coil <NUM>). The conductor foil <NUM> has a thickness MT, a length ML, and a width MW. The insulator sheet <NUM> has a thickness IT, a length IL, and a width IW.

According to some embodiments, the conductor foil width MW is greater than the coil outer diameter CD. In some embodiments, the ratio MW/CD is at least <NUM> and, in some embodiments, is in the range of from about <NUM> to <NUM>.

According to some embodiments, the conductor foil width MW is greater than the coil thickness CT. In some embodiments, the ratio MW/CT is at least <NUM> and, in some embodiments, is in the range of from about <NUM> to <NUM>.

According to some embodiments, the thickness MT is in the range of from about <NUM> to <NUM> and, in some embodiments, in the range of from about <NUM> to <NUM>. According to some embodiments, the length ML is in the range of from about <NUM> to <NUM>. According to some embodiments, the width MW is in the range of from about <NUM> to <NUM>.

According to some embodiments, the thickness IT is in the range of from about <NUM> to <NUM>. According to some embodiments, the length IL is in the range of from about <NUM> to <NUM>. According to some embodiments, the width IW is in the range of from about <NUM> to <NUM>.

According to some embodiments, the ratio MW/MT is at least <NUM> and, in some embodiments, is in the range of from about <NUM> to <NUM>.

According to some embodiments, the ratio IW/IT is at least <NUM> and, in some embodiments, is in the range of from about <NUM> to <NUM>.

According to some embodiments, edge sections <NUM> of the insulator sheet <NUM> extend axially outwardly beyond the adjacent edges of the conductor foil <NUM> a distance IO (<FIG>). In some embodiments, the distance IO is at least <NUM> and, in some embodiments, is in the range of from about <NUM> to <NUM>.

According to some embodiments, the coil <NUM> is formed by the following method. The conductor foil <NUM> is individually formed as a discrete tape, strip, sheet or foil. The insulator sheet <NUM> is separately individually formed as a discrete tape, strip, sheet or foil. The preformed foil <NUM> and preformed sheet <NUM> are thereafter mated, laminated or layered together and spirally co-wound into the coil configuration to form the coil <NUM>. In some embodiments, the layers <NUM>, <NUM> are co-wound about a cylindrical mandrel, form or support. In some embodiments, the layers <NUM>, <NUM> are co-wound about the fitting <NUM>.

In some embodiments, the foil <NUM> and the sheet <NUM> are not bonded to one another along their lengths prior to winding into the coil. That is, the foil <NUM> and the sheet <NUM> are loosely co-wound and are not bonded or laminated to one another until after formation of the coil <NUM>. In some embodiments, the foil <NUM> and the sheet <NUM> are not bonded to one another in the completed coil <NUM> except by the potting <NUM> at the ends of the coil <NUM>. Thus, in this case, the foil <NUM> and the sheet <NUM> are not bonded to one another across their widths. In some embodiments, the foil <NUM> and the sheet <NUM> are tightly wound so that air gaps between the windings of the conductor foil <NUM> are minimized or eliminated.

The terminal bus bars <NUM>, <NUM> may be formed of any suitable electrically conductive material. In some embodiments, the terminal bus bars <NUM>, <NUM> are formed of metal. In some embodiments, the terminal bus bars <NUM>, <NUM> are formed of copper or tin-plated copper.

The inner terminal bus bar <NUM> (<FIG>) includes a contact leg 140A and a terminal leg T1 joined by a connector leg 140B. The contact leg 140A is secured in mechanical and electrical contact with the innermost winding 136E of the conductor foil <NUM> by screws <NUM>, nuts <NUM>, and a clamping member or plate <NUM> (<FIG>). The conductor foil winding 136E is interposed or sandwiched between the contact leg 140A and the clamping plate <NUM>. The screws <NUM> penetrate through the winding 136E and are secured by the nuts <NUM> such that the contact leg 140A and the clamping plate <NUM> compressively clamp onto the winding 136E therebetween. The terminal leg T1 extends out of the enclosure <NUM> through an opening <NUM>.

The outer terminal bus bar <NUM> (<FIG>) includes a contact leg 142A and a terminal leg T2 joined by a connector leg 142B. The contact leg 142A is secured in mechanical and electrical contact with the outermost winding 136F of the conductor foil <NUM> by screws <NUM>, nuts <NUM>, and a clamping plate <NUM> (<FIG>). The winding 136F is clamped between the contact leg 142A and the clamping plate <NUM> by the screws <NUM> (which penetrate through the winding 136F) and the nuts <NUM> in the same manner as described above for the contact leg 140A, the screws <NUM>, the nuts <NUM>, and the clamping plate <NUM>. The terminal leg T2 extends out of the enclosure <NUM> through an opening <NUM>.

The coil assembly <NUM> is constructed in the same manner as the coil assembly <NUM> and includes a multi-layer coil <NUM>, an inner terminal bus bar <NUM>, and an inner terminal bus bar <NUM> corresponding to the <NUM>, the inner terminal bus bar <NUM>, and the outer terminal bus bar <NUM>. The coil <NUM> has a coil axis B-B.

The terminal leg T3 of the inner terminal bus bar <NUM> is secured in mechanical and electrical contact with the innermost winding 156E of the conductor foil of the coil <NUM> by screws <NUM>, nuts <NUM>, and a clamping plate <NUM> in the same manner as described above for the contact leg 140A, the screws <NUM>, the nuts <NUM>, and the clamping plate <NUM>. The terminal leg T3 extends out of the enclosure <NUM> through an opening <NUM>.

The terminal leg T4 of the outer terminal bus bar <NUM> is secured in mechanical and electrical contact with the outermost winding 156F of the conductor foil of the coil <NUM> by screws <NUM>, nuts <NUM>, and a clamping plate <NUM> in the same manner as described above for the contact leg 140A, the screws <NUM>, the nuts <NUM>, and the clamping plate <NUM>. The terminal leg T4 extends out of the enclosure <NUM> through an opening <NUM>.

Thus, in accordance with some embodiments, the coils <NUM>, <NUM> use a metal foil or conductor that is very thin (e.g., from <NUM> up to <NUM>) and very wide (e.g., from <NUM> up to <NUM>). Then, this conductor in the form of a foil is wrapped around a plastic cylinder (e.g., the fitting <NUM>). In between the turns of the foil, a thin insulating sheet is used that will provide adequate insulation between the turns of the coil (e.g., from 5kV up to 20kV). Bus bars are connected to the inner and outer windings of the conductor foil and project out from the enclosure. The bus bars are further electrically insulated using heat shrinkable electrically insulating sleeves. The heat shrinkable sleeves can prevent flashover between the bus bars and the remainder of the coils. The coils are covered inside a plastic enclosure and then potted with epoxy resin to provide electrical insulation in between the turns of the conductor foil at the two axial ends of the coil. Further, the potting prevents humidity from penetrating inside the coil that might reduce the insulation of the coil or age the insulation properties of the insulation used. Further, the potting will also make the coil more stable in case of vibration and also increase the insulation between the two outputs of the coil.

According to method embodiments, the inductor assembly <NUM> is a two phase coil used in a two phase AC electrical power system <NUM> as illustrated by the diagram in <FIG>. The input of line L1 is connected to the terminal T2 and the output of line L1 is connected to the terminal T1. The input of line L2 is connected to the terminal T3 and the output of line L2 is connected to the terminal T4. In some embodiments, AC power system has a voltage L1-L2 of about 650Vrms and a load current of about 100A. Circuit breakers may be provided between the input terminals T2, T3 of the inductor assembly <NUM> and the power supply. The output terminals T1, T4 of the inductor assemblies <NUM> may be connected to a power distribution panel.

In the event of a surge current (high di/dt) in a line, the insulation tube <NUM> will isolate the covered terminal bus bar and thereby prevent flashover between the coil connected to that line and a terminal bus bar of the other coil. For example, it can be seen in <FIG> that the connecting leg 140B of the bus bar <NUM> extends along the length of the coil <NUM>. When a surge current is applied to the coil <NUM>, the tube <NUM> on the terminal bus bar <NUM> can prevent flashover from the coil <NUM> to the connecting leg 140B of the bus bar <NUM>.

The potting <NUM> (e.g., epoxy resin) covers the ends of the coils <NUM>, <NUM> and thereby stabilizes the coils <NUM>, <NUM> and increases the electrical insulation between the turns of the conductor foil (e.g., the conductor foil <NUM>) within each coil <NUM>, <NUM>. The potting <NUM> also increases the electrical insulation between the adjacent ends of the two coils <NUM>, <NUM>. The potting <NUM> further increases the electrical insulation between the coils <NUM>, <NUM> and the bus bars <NUM>, <NUM>, <NUM>, <NUM>.

The external plastic enclosure <NUM> can take vibrations and provide environmental protection for the coils <NUM>, <NUM>. The enclosure <NUM> also increases electrical insulation for the coils <NUM>, <NUM>. The strong mounting brackets or bases <NUM> and support shaft <NUM> can ensure that the inductor assembly <NUM> can withstand vibration.

The bushings <NUM> can serve to take up manufacturing tolerances in the inductor assembly <NUM>, thereby reducing vibration. The bushings <NUM> can also serve to damp or absorb forces (e.g., vibration) applied to the inductor assembly <NUM>. The bushings <NUM> can also resiliently and temporarily take up expansion of the inductor assembly <NUM> caused by heating of the coils <NUM>, <NUM>.

The potting can also take up manufacturing tolerances in the inductor assembly <NUM>, thereby reducing vibration.

Because screws <NUM> or other fasteners and clamping plates <NUM> are used to secure the bus bars <NUM>, <NUM>, <NUM>, <NUM> to the innermost and outermost windings 136E, 136F, 156E, 156F, it is not necessary to use a welding or soldering technique that may melt the thin coil conductor foil.

<FIG> show an inductor assembly <NUM> according to further embodiments not forming part of the claimed invention. The inductor assembly <NUM> is constructed similarly to the inductor assembly <NUM> but includes only a single coil assembly <NUM>. The coil assembly <NUM> includes a coil <NUM> and terminal bus bars <NUM>, <NUM> corresponding to and constructed in same manner as described for the coil assembly <NUM>, the coil <NUM> and the terminal bus bars <NUM>, <NUM>. The terminal bus bars <NUM>, <NUM> have terminal legs T1 and T2 corresponding to the terminal legs T1 and T2 of the inductor assembly <NUM>.

As schematically illustrated in <FIG>, the inductor assembly <NUM> can be connected in series to the protective earth (PE) of a power system <NUM> with a voltage of 650Vrms between its lines and a load current of 100A. The inductor assembly <NUM> may be rated for half of the actual line currents (i.e., around 50A) according to relevant standards. The output T1 of the inductor assembly <NUM> is connected to the PE terminals inside a distribution panel.

According to some embodiments, an inductor assembly as described herein has a specific load current rating of around 100A, can operate in a normal low voltage (LV) application (up to 1000Vac), is able to sustain very high transient overvoltage events that might be developed across its ends (in the range of 100kV), is able to comply with extreme vibrating conditions, is able to be installed in outside environments, substantially reduces or minimizes the risk of fire under failure, has a small footprint and size (e.g., less than <NUM><NUM>), and is relatively lightweight (e.g., less than <NUM>).

<FIG> show a dual coil inductor assembly <NUM> according to further embodiments not forming part of the claimed invention. The inductor assembly <NUM> is constructed similarly to the inductor assembly <NUM> but is configured such that the terminal legs T1, T2 extend from one axial end 302A of the inductor assembly <NUM>, and the terminal legs T3, T4 extend from the opposite axial end 302B of the inductor assembly <NUM>.

The inductor assembly <NUM> includes an enclosure assembly <NUM>, a pair of axially spaced apart support bases <NUM>, a support shaft <NUM>, an electrically insulating fitting <NUM>, a pair of bushings <NUM>, potting <NUM>, insulation sleeves or tubes <NUM>, a first coil assembly <NUM>, and a second coil assembly <NUM> corresponding to the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively, except as shown and discussed.

The enclosure assembly <NUM> includes a pair of axially opposed, cylindrical, cup shaped shells <NUM> and a pair of axially opposed end plates 312A and 312B. Each shell <NUM> defines a chamber <NUM> to contain a respective one of the assemblies <NUM>, <NUM> and potting <NUM>. Two terminal openings <NUM> are defined in each end plate <NUM> and communicate with the adjacent chamber <NUM>. An electrically insulating partition bushing <NUM> is interposed between the adjacent inner ends of the shells <NUM>. The partition bushing <NUM> may be formed of a material as described above for the bushings <NUM>.

The coil assemblies <NUM>, <NUM> are constructed in the same manner as the coil assemblies <NUM>, <NUM> except in the configuration of their terminal bus bars <NUM>, <NUM>, <NUM>, <NUM>. With reference to <FIG>, the terminal bus bar <NUM> is connected to the innermost winding 336E of the coil <NUM> and has a terminal leg T1 extending through an opening <NUM> in the end plate 312A. With reference to <FIG>, the terminal bus bar <NUM> is connected to the outermost winding 336F of the coil <NUM> and has a terminal leg T2 extending through the other opening <NUM> in the end plate 312A. The terminal bus bar <NUM> is connected to the innermost winding of the coil <NUM> and has a terminal leg T3 extending through an opening <NUM> in the end plate 312B. The terminal bus bar <NUM> is connected to the outermost winding of the coil <NUM> and has a terminal leg T4 extending through the other opening <NUM> in the end plate 312B. Each terminal leg T1, T2, T3, T4 is covered by an insulation tube <NUM> that extends through the respective opening <NUM>. Each terminal leg T1, T2, T3, T4 may further be covered by an inner insulation tube <NUM> within the insulation tube <NUM>. The insulation tube <NUM> may be formed of the same material as described for the insulation tube <NUM>.

<FIG> show the coil assembly <NUM> in more detail. The coil assembly <NUM> is constructed in the same manner as the coil assembly <NUM>. As can be seen in <FIG>, the coil <NUM> includes a foil <NUM>, an insulator sheet <NUM>, clamp plates <NUM>, and fasteners <NUM>, <NUM> corresponding to and assembled in the same manner as the components <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, respectively, of the coil assembly <NUM>. The end of the innermost winding 336E of the foil <NUM> is mechanically secured in electrical contact with the terminal bus bar <NUM> by a clamp plate 341A and fasteners <NUM>, <NUM>. The bus bar <NUM>, clamp plate 341A and winding 336E may be received in a slot in the fitting <NUM> as illustrated. The end of the outermost winding 336F of the foil <NUM> is mechanically secured in electrical contact with the terminal bus bar <NUM> by a clamp plate <NUM> and fasteners <NUM>, <NUM>.

As will be appreciated from <FIG>, the dual coil inductor assembly <NUM> has a longitudinal axis L-L, the coil <NUM> has a coil axis A-A, and the coil <NUM> has a coil axis B-B. The coil axes A-A, B-B are substantially parallel with and, in some embodiments, substantially coaxial with, the axis L-L. In some embodiments, the coil axes A-A, B-B are substantially parallel with one another. The terminal legs T1, T2, T3, T4 each extend or project axially from an end 302A, 302B of the inductor assembly <NUM> in a direction along the axis L-L. In some embodiments, the terminal legs T1, T2, T3, T4 each extend along an axis that is substantially parallel with the axis L-L.

Thus, the input terminal T1 and the output terminal T2 of the coil <NUM> extend from the same end 302A of the unit <NUM>. The input terminal T3 and the output terminal T4 of the coil <NUM> extend from the same opposing end 302B of the unit <NUM>. This construction can enable the coils <NUM>, <NUM> to be better insulated from one another because there is no terminal bus bar from one coil <NUM>, <NUM> extending across the other coil <NUM>, <NUM>.

The terminal configuration of the inductor assembly <NUM> also permits enables the assembly of a multi-unit inductor system <NUM> as shown in <FIG> and <FIG>, for example. The system <NUM> includes a plurality (as shown, four) of dual coil inductor assemblies 300A-D (each constructed as described for the assembly <NUM>) in a relatively compact side-by-side arrangement. The inductor coils <NUM> of the inductor assemblies 300A-D are connected to the line L1 and to one another in series by connecting conductors <NUM> (e.g., metal cables). The inductor coils <NUM> of the inductor assemblies 300A-D are connected to the line L2 and to one another in series by connecting conductors <NUM> (e.g., metal cables).

In the system <NUM>, the longitudinal axes L-L of the inductor assemblies 300A-D extend non-coaxially to one another. That is, the respective longitudinal axes L-L of the inductor assemblies 300A-D extend (as shown) substantially parallel to one another but laterally displaced from one other, or may extend transversely to one another.

The configuration of the system <NUM> avoids a coaxial configuration of inductor assemblies 100A-D as shown in the inductor system <NUM> of <FIG>, for example, wherein a common central metal post <NUM>' supports each of the coils <NUM>, <NUM> of the multiple inductor assemblies 100A-D. In the system <NUM>, the dielectric withstand voltage of the system <NUM> may be limited by the distance D1 between each terminal T1, T2, T3, T4 and the adjacent base <NUM>. In the event of a lightning strike or other surge event, the induced voltage on the coil terminals due to the high di/dt will result into a flashover; as a result the current may flash over from a terminal T1- T4 to the adjacent base <NUM>, and from the base <NUM> the current can conduct through the central metal post <NUM>' to the high voltage HV side of the circuit, thereby short circuiting around the coils <NUM>, <NUM> of the downstream inductor assemblies 100A-D. That is, the overall dielectric withstand voltage of the system <NUM> is reduced because the voltage potential between the ends LV, HV of the circuit are bridged by the central metal post <NUM>'.

By contrast and with reference to <FIG>, in the system <NUM>, current from a lightning surge or other surge event may still flash over, due to induced lightning impulse voltage from the high di/di, from a terminal T1, T2, T3, T4 to the adjacent base <NUM> across a distance D2. However, in order for the current to conduct to the next inductor assembly 300B-D, the current must flash over a distance D3 from the base <NUM> of the first inductor assembly 300A to the base <NUM> of the inductor assembly 300B. The distances between the bases <NUM> of the adjacent inductor assemblies 300A-D can be chosen to provide an increased and sufficient dielectric withstand voltage between the inductor assemblies 300A-D and for the system <NUM> overall. In this way, a high amount of electrical insulation between the inductor assemblies 300A-D is achieved. As a result, the overall lightning impulse overvoltage of the overall system <NUM> from the LV side to the HV side is maintained. For example, if the Lightning Impulse breakdown voltage of each inductor assembly 300A-D is <NUM> kV, then the overall Lightning Impulse breakdown voltage of the system <NUM> will be <NUM> kV. This can be accomplished while retaining an electrically conductive metal support shaft <NUM> in each inductor assembly 300A-D. A metal support shaft <NUM> may be desirable to provide improved strength, thermal conductive, resistance to thermal damage (e.g., melting), and ease and flexibility in fabrication.

The partition bushing <NUM> can electrically insulate the coil assemblies <NUM>, <NUM> from one another. The partition bushing <NUM> can serve to take up manufacturing tolerances in the inductor assembly <NUM>, thereby reducing vibration. The partition bushing <NUM> can also serve to damp or absorb forces (e.g., vibration) applied to the inductor assembly <NUM>. The partition bushing <NUM> can also resiliently and temporarily take up expansion of the inductor assembly <NUM> caused by heating of the coils <NUM>, <NUM>.

The inductor assembly <NUM> has a longitudinal axis L-L and the coil <NUM> has a coil axis A-A. The coil axis A-A is substantially parallel with and, in some embodiments, substantially coaxial with, the axis L-L. The terminal legs T1, T2 each extend or project axially from the end 410A of the inductor assembly <NUM> in a direction along the axis L-L. In some embodiments, the terminal legs T1, T2 each extend along an axis that is substantially parallel with the axis L-L. Thus, the input terminal T1 and the output terminal T2 of the coil <NUM> extend from the same end 402B of the unit <NUM> as discussed above with regard to the inductor assembly <NUM>.

A plurality of the inductor assemblies <NUM> can be assembled into a multi-unit inductor system <NUM> as shown in <FIG>, for example. The system <NUM> includes a plurality (as shown, four) of inductor assemblies 400A-D (each constructed as described for the assembly <NUM>) in a relatively compact side-by-side arrangement. The inductor coils <NUM> of the inductor assemblies 400A-D are connected to the line L1 and to one another in series by connecting conductors <NUM> (e.g., metal cables).

In the system <NUM>, the longitudinal axes L-L of the inductor assemblies 400A-D extend non-coaxially to one another. That is, the respective longitudinal axes L-L of the inductor assemblies 400A-D extend (as shown) substantially parallel to one another but laterally displaced from one other, or may extend transversely to one another. This configuration can thus provide the advantages discussed above with regard to the inductor assembly <NUM>.

With reference to <FIG>, a coil assembly <NUM> according to further embodiments not forming part of the claimed invention is shown therein. The coil assembly <NUM> can be used in place of any of the coil assemblies <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The coil assembly <NUM> is constructed and operates in the same manner as the coil assembly <NUM>, except at follows.

The coil assembly <NUM> includes a coil <NUM> that differs from the coil <NUM> as discussed below. The coil assembly <NUM> also includes terminal busbars <NUM>, <NUM>, clamp plates <NUM>, and fasteners <NUM>, <NUM> corresponding to and assembled in the same manner as the components, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, respectively, of the coil assembly <NUM>.

The coil <NUM> includes a first foil <NUM> and an insulator sheet <NUM> corresponding to the foil <NUM> and the insulator sheet <NUM>. The coil <NUM> further includes a second conductor or foil <NUM>. The first and second foils <NUM>, <NUM> collectively form a multilayer electrical conductor <NUM>. The foils <NUM>, <NUM> may be formed of the same materials and in the same dimensions as described above for the foil <NUM>.

The first foil <NUM>, the second foil <NUM> and the insulator sheet <NUM> are spirally co-wound or wrapped about the coil axis A-A to form windings <NUM> with the second foil <NUM> interposed or sandwiched between the first foil <NUM> and insulator sheet <NUM>. The windings <NUM> extend progressively from an innermost winding 536E of the multilayer conductor <NUM> (i.e., the conductor foils <NUM>, <NUM>) to an outermost winding 536F of the multilayer conductor <NUM> (i.e., the conductor foils <NUM>, <NUM>) on the outer diameter of the coil <NUM>. Each winding <NUM> is radially superimposed on, stacked on, or wrapped around the preceding winding <NUM>. The foils <NUM>, <NUM> may be wound tightly in fact to face electrical contact with one another.

Each of the conductor foils <NUM>, <NUM> has opposed side edges that are axially spaced apart along the coil axis A-A and extend substantially parallel to one another. The conductor foils <NUM>, <NUM> are spirally wound such that each side edge remains substantially in or proximate a single lateral plane (i.e., corresponding to planes E-E of <FIG>) throughout the coil <NUM> from the winding 536E to the winding 536F. That is, the multilayer conductor <NUM> and the conductor foils <NUM>, <NUM> are maintained in alignment with themselves and are spirally, not helically, wound. In some embodiments, the conductor foils <NUM>, <NUM> are substantially coextensive.

The end of the innermost winding 536E of the multilayer conductor (i.e., the ends of the foil <NUM> and the foil <NUM>) is mechanically secured in electrical contact with the terminal bus bar <NUM> by the clamp plate 541A and fasteners <NUM>, <NUM>. The bus bar <NUM>, clamp plate 541A and winding 536E may be received in a slot in the fitting <NUM> as illustrated. The end of the outermost winding 536F of the multilayer conductor (i.e., the ends of the foil <NUM> and the foil <NUM>) is mechanically secured in electrical contact with the terminal bus bar <NUM> by the clamp plate <NUM> and fasteners <NUM>, <NUM>.

The multilayer conductor <NUM> has an increased cross-sectional area as compared to the foil <NUM> and thereby provides less electrical resistance for a conductor of the same length. As a result, the coil <NUM> (and thereby an inductor assembly incorporating the coil assembly <NUM>) can be rated for a greater amperage and power.

For example, the two-phase inductor assembly <NUM> may be rated for 100A for each line L1, L2 (with the load currents through L1 and L2). The PE inductor assembly <NUM> may be rated for 50A (i.e., half the rating of the line inductor). In that case, the coils of the inductor assemblies <NUM>, <NUM> each use a single conductor foil.

The parallel, superimposed conductor foils <NUM>, <NUM> of the multilayer conductor <NUM> double the cross-sectional area of the coil conductor as compared to the single foil conductors of the inductor assemblies <NUM>, <NUM>. As a result, the two-phase inductor assembly incorporating the coil assembly <NUM> may be rated for 150A for each line L1, L2, and the PE inductor assembly incorporating the coil assembly <NUM> may be rated for 75A.

In some embodiments, the foil <NUM>, the foil <NUM>, and the insulator sheet <NUM> are not bonded to one another along their lengths prior to winding into the coil. That is, the foils <NUM>, <NUM> and the sheet <NUM> are loosely co-wound and are not bonded or laminated to one another until after formation of the coil <NUM>. In some embodiments, the foils <NUM>, <NUM> and the insulator sheet <NUM> are not bonded to one another in the completed coil <NUM> except by the potting <NUM> at the ends of the coil <NUM>. In this case, the layers, <NUM>, <NUM>, <NUM> are not bonded to one another across their widths. In some embodiments, the foils <NUM>, <NUM> and the sheet <NUM> are tightly wound so that air gaps between the windings of the conductor foils <NUM>, <NUM> are minimized or eliminated.

The multilayer conductor <NUM> provides advantages over using a thicker single foil for the coil conductor (e.g., two <NUM> foils <NUM>, <NUM> instead of a single <NUM> foil <NUM>) because a thicker single foil may be too thick to make the turns efficiently (i.e., without creating gaps in between the turns of the coil, etc). The outer diameter of the coil <NUM> may be modestly increased as compared to the diameter of the coil <NUM> while maintaining the same coil length. On the other hand, if the conductor cross-section was increased by using the same thickness foil <NUM> (e.g., <NUM>) but doubling the width of the foil <NUM>, then the coil footprint would be substantially double in length, which may require the inductor assembly to have an undesirable footprint.

Claim 1:
A dual coil inductor assembly (<NUM>) comprising:
a first coil (<NUM>) including a spirally wound first metal foil (<NUM>);
a second coil (<NUM>) including a spirally wound second metal foil;
a first terminal (T2) electrically connected to the first metal foil at a first location on the first metal foil;
a second terminal (T1) electrically connected to the first metal foil at a second location on the first metal foil;
a third terminal (T3) electrically connected to the second metal foil at a first location on the second metal foil; and
a fourth terminal (T4) electrically connected to the second metal foil at a second location on the second metal foil;
wherein the dual coil inductor assembly has an inductor assembly longitudinal axis (L-L), a first axial end and an opposing second axial end; characterized in that:
the first terminal (T2) and the third terminal (T3) are located on the first axial end, and the second terminal (T1) and the fourth terminal (T4) are located on the second axial end.