Patent Description:
<CIT> relates to an electrical inductive apparatus comprising first, second and third winding structures disposed in spaced, adjacent, concentric relation, respectively; wherein first and second solid insulating means are disposed between said first and second winding structures, and between said second and third winding structures, respectively; said first and second solid insulating means having inner and outer major surfaces which have an electrically conductive or semiconductive means disposed thereon; wherein means are provided for electrically connecting the electrically conductive means on said inner and outer major surfaces to the winding structure immediately adjacent thereto.

<CIT> relates to a voltage transformer and a manufacturing method thereof, wherein a main insulation device includes a main insulating resin cylinder and a semi-conductive paint layer; the main insulating resin cylinder has a cylindrical shape; the inner surface and the outer surface of the main insulating resin cylinder are semi-conductive paint layers.

<CIT> relates to an insulation arrangement for potential isolation between a high voltage winding and a low voltage winding of a transformer, said insulation arrangement has a layered structure, comprising inner insulation between the high voltage winding and the low voltage winding, which are adjoined by at least one semiconductive layer.

The present invention relates to an apparatus as defined in independent claim <NUM> and to a method of manufacturing such an apparatus as defined in claim <NUM>.

The following summary presents a simplified summary of certain features. The summary is not an extensive overview and is not intended to identify key or critical elements.

Systems, apparatuses, and methods are described for a transformer that includes at least two sets of windings, and at least two semiconductive shields configured and disposed to cause a first electrical field between the two semiconductive shields, a second electrical field between a first of the semiconductive shields and a first set of windings, and a third electrical field between a second of the semiconductive shields and a second set of windings. According to features of the disclosure herein, the second and third electrical fields may be smaller than the first electrical field. Enhancing the first electrical field with respect to the second and third electrical fields may enable disposing the sets of windings using reduced insulation, and may increase cooling efficiency of transformer elements.

These and other features and advantages are described in greater detail below.

Some features are shown by way of example, and not by limitation, in the accompanying drawings. In the drawings, like numerals reference similar elements.

The accompanying drawings, which form a part hereof, show examples of the disclosure. It is to be understood that the examples shown in the drawings and/or discussed herein are non-exclusive and that there are other examples of how the disclosure may be practiced.

Reference is now made to <FIG>, which shows a transformer <NUM> as described herein below. The transformer <NUM> comprises core <NUM>, and is encompassed by case <NUM>. Case <NUM> may be made of, for example, resin, and may be disposed to protect internal components of transformer <NUM> (e.g., from dust, humidity, etc.) and, as shown in <FIG>, may obstruct an external view of the additional internal components, that are shown and discussed in further detail below. Core <NUM> may be made of ferromagnetic material or ferromagnetic compound, and may be designed to cause magnetic flux induced by windings of transformer <NUM> (not depicted in <FIG>) to flow primarily through core <NUM>.

Transformer <NUM> may be placed in a grounded conducting case, or casing (e. g, a box, not depicted) or a grounded conducting frame, to increase safety and reduce electrical field leakage from transformer <NUM>.

Reference is now made to <FIG>, which shows additional elements of transformer <NUM> that are obscured by case <NUM> as depicted in <FIG>. In addition to core <NUM>, transformer <NUM> comprises first windings 210a and 210b, first inner shield lid 211a, second inner shield lid 211b, first outer shield lid 212a, second outer shield lid 212b, first bobbin 213a and second bobbin 213b. Transformer <NUM> may include additional components that are concealed in <FIG> by first windings 210a and 210b, and will be described below.

In the illustrative design shown in <FIG>, core <NUM> is of rectangular shape, having two legs, and two shorter members connecting parallel legs to form a full magnetic path. According to some features, core <NUM> may also include an air gap. First windings 210a and 210b are each wound around one of the parallel legs.

Windings 210a and 210b are shown each having a single winding of conductive material, the conductive material substantially filling the entire space between first outer shield lid 212a and second outer shield lid 212b. According to features of the disclosure herein, each of windings 210a and 210b may comprise more than one winding (e.g., several, tens, hundreds of thousands of windings), and may fill the entire space or part of the space between first outer shield lid 212a and second outer shield lid 212b. Windings 210a and 210b may be formed using single-strand wire, or multi-strand wire (e.g., Litz wire). Winding 210a may be wound around a first leg of core <NUM> (with intermediate elements disposed between winding 210a and the first leg of core <NUM>, as described herein), and winding 210b may be wound around a second leg of core <NUM> (with intermediate elements disposed between winding 210b and the second leg of core <NUM>, as described herein).

Each of first windings 210a and 210b may feature two or more terminals or taps (not explicitly depicted) for connecting to voltage terminals external to the transformer. For example, first winding 210a and first winding 210b may each have two voltage terminals, and may each be connected to a varying [e.g., an alternating current (AC)] voltage having an amplitude of several volts, tens of volts, hundreds of volts or thousands of volts. First windings 210a and 210b may be magnetically coupled to one another via core <NUM>, and may also be magnetically coupled to secondary windings (depicted herein in <FIG>).

First inner shield lid 211a and second inner shield lid 211b may be formed using semiconductive material, for example, semiconductive plastic, isolating plastic with a semiconductive coating, or other semiconductive materials. First inner shield lid 211a and second inner shield lid 211b may be connected to one another by first and second inner shield legs (not shown in <FIG>) to form an inner semiconductive shield having two semiconductive shield legs encompassing the first and second legs of core <NUM>. Similarly, first outer shield lid 212a and second outer shield lid 212b may be connected to one another by first and second outer shield legs (not shown in <FIG>) to form an outer semiconductive shield having two semiconductive shield legs encompassing the first and second legs of core <NUM>. The inner semiconductive shield may be manufactured (e.g., cast) as a single component (e.g., a single mold may be used for manufacturing the inner semiconductive shield, the mold forming the shapes of first inner shield lid 211a, second inner shield lid 211b, and the first and second inner shield legs), or may be formed combining separately-manufactured elements [e.g., first inner shield lid 211a and second inner shield lid 211b may be manufactured (e.g., cast) separately, and may be connected, during construction of transformer <NUM>, to the first and second inner shield legs]. Similarly, the outer semiconductive shield may be manufactured (e.g., cast) as a single component or may be formed combining separately-manufactured elements. The inner and outer shields may be shaped to form Rogowski profiles, or other profiles designed to increase uniformity in an electrical field between the inner and outer shields and to suppress field enhancement at the shield edges.

<FIG> also shows surfaces of first inner bobbin 213a and second inner bobbin 213b. First inner bobbin 213a and second inner bobbin 213b may encompass the first and second legs of core <NUM>, respectively, and may be provided to support mounting of windings (not depicted in <FIG>) magnetically coupled to (and galvanically isolated from) windings 210a and 210b. According to features of the disclosure herein, first inner bobbin 213a and second inner bobbin 213b might not be used, and additional windings may be disposed directly around the first and second legs of core <NUM>.

Reference is now made to <FIG>, which depicts an "exploded" view of various elements of transformer <NUM>. For simplicity and brevity, elements encompassing second leg L2 of core <NUM> are depicted. It is understood that optionally, similar or identical elements may encompass first leg L1 of core <NUM>, in accordance with <FIG>. Dotted lines terminated by arrows indicate order of layering: an arrow pointing at a first element, with a dotted line extending from the arrow to a second element, indicates that the second element may be disposed around (e.g., may partially or completely encompass) the first element.

Inner bobbin 213b may encompass second leg L2. A first surface s1 of inner bobbin 213b may fit around a first corresponding slot slot1 of first inner shield lid 211a (as shown in <FIG>), and a second surface s2 of inner bobbin 213b may fit through a corresponding slot (not depicted in <FIG>) of second inner shield lid 211b.

Windings <NUM> may be wound around inner bobbin 213b. According to another implementation of transformer <NUM> of the disclosure herein, inner bobbin 213b might not be used, and instead, windings <NUM> may be wound directly around second leg L2. Windings <NUM> may be constructed similarly to or the same as windings 210a and 210b, but may feature a different number of windings compared to windings 210a and 210b. Windings <NUM> may feature two or more voltage taps (e.g., voltage terminals) to be connected to voltage terminals of a power circuit (e.g., a full-bridge of transistors or diodes, or a different type of power electronics circuit). Shield leg <NUM> may be disposed around (e.g., may encompass) windings <NUM>. Shield leg <NUM> may be attached to (e.g., manufactured together with, or later connected to) first shield lid 211a and second inner shield lids 211b, for forming an inner shield disposed around (e.g., encompassing) windings <NUM>, and "shielding" windings <NUM> from strong electrical fields. The inner shield (e.g., one of first inner shield lid 211a and second inner shield lid 211b, and/or shield leg <NUM>) may be connected to a first voltage tap of windings <NUM>, and may be referenced to the same electrical potential as the first voltage tap of windings <NUM>.

Shield leg <NUM> may be disposed around (e.g., may encompass) shield leg <NUM>. Shield leg <NUM> may be attached to (e.g., manufactured together with, or later connected to) first and second outer shield lids 212a and 212b, for forming an outer shield disposed around (e.g., encompassing) shield leg <NUM>. Insulating material (not explicitly depicted) may be injected between shield leg <NUM> and shield leg <NUM>, between inner shield lid 211a and outer shield lid 212a, and between inner shield lid 211b and outer shield lid 212b. Shield leg <NUM>, and outer shield lids 212a and 212b may be made of semiconductive material the same as or similar to shield lid <NUM>, and inner shield lids 211a and 211b.

Windings 210b may be wound around shield leg <NUM>. Windings 210b may feature two or more voltage taps (e.g., voltage terminals), with a first one of the voltage taps electrically connected to the outer shield (e.g., one of first and second outer shield lids 212a, 212b and/or shield leg <NUM>) and referencing the outer shield to the same electrical potential as the first one of the voltage taps of windings 210b.

Windings 210b may be referenced (e.g., by direct electrical connection) to a first electrical potential, and windings <NUM> may be referenced to a second electrical potential that is different from the first electrical potential. For example, windings <NUM> may be referenced to ground, and windings 210b may be referenced (e.g., electrically connected) to a potential that is 100V, 1000V, 10kV, 20kV, 50kV, 100kV, or even higher. Windings <NUM> may be referenced to a varying potential reference point. For example, windings <NUM> may be referenced voltage reference point varying (e.g., sinusoidally or as a square-wave) between, for example, -1kV and +1kV, -10kV and +10kV, -20kV and +20kV, -100kV and +100kV, or a varying (e.g., sinusoidal) potential having an amplitude above 100kV or even above 1MV.

As a result of windings 210b and <NUM> being referenced to different potential levels, a voltage drop may exist between windings 210b and <NUM>. In accordance with the numerical examples above, the voltage drop may be large - for example, tens, hundreds or thousands of kilovolts. By electrically connecting windings 210b to the outer shield and electrically connecting windings <NUM> to the inner shield, the voltage drop may exist between the inner shield and the outer shield. By designing the inner shield to be disposed around (e.g., encompass) the inner windings and by designing the outer shield to be disposed around (e.g., encompass) the inner shield, windings 210b and windings <NUM> may be "shielded" and separated from one another by the shields. This may enable reducing the insulation around the wires used for the windings to a rating that may be far less than the potential difference between windings 210b and windings <NUM>. For example, windings 210b may have a voltage drop of up to 1000V between two taps on windings 210b. Similarly, windings <NUM> may have a voltage drop of up to 1000V between two taps on windings <NUM>. Windings 210b may be referenced to 20kV, and windings <NUM> may be referenced to ground (0V). Without shielding, insulation of wires used for windings <NUM> and 210b would be rated to withstand over 20kV. Using inner and outer shields, as disclosed herein, may enable reducing the wire insulation to 100V, and disposing insulating material rated to withstand 20kV between the inner shield and the outer shield, which may provide cost savings and/or may enable more efficient cooling of transformer elements such as core <NUM>, windings 210b and windings 310b, as the transformer elements are not covered by large quantities of insulating material.

Insulating material between the inner and outer shields may be the same as the material used for manufacturing case <NUM>, and may be injected during the formation of case <NUM>. For example, a mold having the shape of case <NUM> may be placed around the elements of transformer <NUM> as depicted in <FIG>, and insulating material (e.g. resin epoxy, silicon, polyurethane) may be injected into the mold, both creating case <NUM> and filling in a gap between the inner and outer shields. The injection may be, for example, vacuum potting, automatic pressure gelation, or other suitable methods of injection.

Bobbin 213b, windings <NUM>, shield leg <NUM>, shield leg <NUM> and windings 310b have been described with respect to leg L2 of core <NUM>. Similar or identical elements (e.g., windings 210a of <FIG>, corresponding to windings 210b; or bobbin 213a of <FIG>, corresponding to bobbin 213b) may be disposed around leg L1 of core <NUM>, to increase efficient use of core <NUM>. For brevity, those elements have not been shown explicitly with respect to <FIG>, but they are included in the scope of the disclosure herein.

Reference is now made to <FIG>, which shows an X-Y cross-section of transformer <NUM>, according to the X-Y-Z axes of <FIG>, in accordance with the disclosure herein. For increased clarity, some reference numbers are shown more than once and indicate different parts of a single element that, due to the cross-section view, does not appear to be contiguous. Arrows indicating electrical field directions and magnitudes as obtained from an electrical simulation are also shown. Dark arrows indicate a weak field, and arrows having a lighter color indicate a stronger field. Windings 310b correspond to windings <NUM> of <FIG>, disposed over leg L2 of core <NUM>. Windings 310a are similar to windings 310b, and are disposed over leg L1 of core <NUM>. Shield leg 311b corresponds to shield leg <NUM> of <FIG>, disposed over leg L2 of core <NUM>; and shield leg 311a corresponds to another shield leg similar to shield leg <NUM> of <FIG>, disposed over leg L1 of core <NUM>. Shield leg 312b corresponds to shield leg <NUM> of <FIG>, disposed over leg L2 of core <NUM>; and shield leg 312a corresponds to another shield leg similar to shield leg <NUM> of <FIG>, disposed over leg L1 of core <NUM>.

The simulation included connecting a first square wave voltage generator producing a square wave varying between -700V and +700V to two terminals of windings 210a (in the simulation, there are no additional voltage taps), a second square wave voltage generator substantially in-phase with the first square wave voltage generators, and producing a square wave varying between -700V and +700V to two terminals of windings 210b. Windings <NUM> have <NUM>% more turns than windings 210a and 210b, resulting in a square wave varying between -840V and +840V across windings 310a and across windings 310b. Windings 210a and 210b are referenced (in this example, directly connected to a potential of about 0V), and windings 310a and 310b are referenced to a voltage of about 10kV. The simulation included placing transformer <NUM> in a grounded, conducting case (e.g., a box) having conducting sides spaced approximately <NUM> from the outer edges of transformer <NUM>.

Area A as depicted in <FIG> refers to the space outside of transformer <NUM> (i.e., outside case <NUM>). Area B is the area within casing <NUM> that is not between the semiconductive shields. Area C is the area between the semiconductive shields (e.g., between a shield leg <NUM> and shield leg <NUM>, or between a shield lid 211a and shield lid 212a, or between a shield lid 211b and shield lid 212b. As shown by the field arrows, in area A, the electric field is of small magnitude, and flows outwards from transformer case <NUM> towards the conductive casing used in the simulation. In area B, the field is also weak, and flows in a somewhat "curved" (due to an "edge effect" present at edges of charged plates) direction from shield lid 212a to shield lid 211a, and from shield lid 212b to shield lid 211b. In area C, between the two shields, the electric field is strong (as indicated by light-colored arrows), and "flows" from the inner shield (formed by shield lids 211a and 211b, and shield legs 311a and 311b) to the outer shield (formed by shield lids 212a and 212b, and shield legs 312a and 312b.

Claim 1:
An apparatus comprising:
a transformer (<NUM>) comprising:
a core (<NUM>) comprising at least a first core leg (L1),
first windings (310a) disposed around the first core leg,
a first inner semiconductive shield manufactured as a single component or formed combining separately-manufactured elements (211a, 211b, 311a, 311b), said first inner semiconductive shield comprising
a first semiconductive shield leg (311a) disposed around the first windings, wherein the first semiconductive shield leg (311a) is formed using semiconductive material and is electrically connected to the first windings,
a second outer semiconductive shield manufactured as a single component or formed combining separately-manufactured elements (212a, 212b, 312a, 312b), said second outer semiconductive shield comprising
a second semiconductive shield leg (312a) disposed around the first semiconductive shield leg (311a), wherein the second semiconductive shield leg (312a) is formed using semiconductive material and
second windings (210a) disposed around the second semiconductive shield leg, wherein the second semiconductive shield leg is electrically connected to the second windings,
wherein the first inner semiconductive shield comprising the first semiconductive shield leg (311a) and second outer semiconductive shield comprising the first semiconductive shield leg (312a) are configured and disposed to form an area (C) there between in which a first electrical field is formed.