Transformer with ferromagnetic foil windings

Abstract

The proposed transformer includes windings made of a multi-layer ferromagnetic foil tape having an even number m of ferromagnetic layers, coated by interlayer insulation. The winding's upper ends are connected through a first yoke, the winding's bottom ends are connected through a second yoke. Each winding is wrapped by a short-circuited coil, and contains a component for transposition of layers connected in a break at the middle of tape. The insulation's thickness is determined by a ratio of d.sub.i>u.sub.n2, pic*/(E.sub.n2, pic.Math.m), where u.sub.n2, pic is a maximum peak voltage between adjacent winding turns, E.sub.n2, pic is a maximum electric field strength of the insulation. The insulation uses either ferroelectric material Fe.sub.2O.sub.3, or multi-layered material with an intensive antiferromagnetic interaction formed as a plurality of pairs of alternating layers of Cu—Fe with a ratio of thicknesses of Cu and Fe ranged from 5:1 to 10:1.

Claims

1. A transformer comprising: a number of windings each having a vertical cross-section, said windings are made of a foil tape having a length, said windings are wound by m layers coated with an interlayer insulation, wherein said m is an even positive number; said layers each is made of ferromagnetic metal; said windings each has—upper ends connected through a first yoke and—bottom ends connected through a second yoke; said windings each, in the vertical cross-section, is wrapped by a short-circuited coil; said windings each contains a transposition component for transposition of said layers, wherein the transposition component is inserted into a break provided in a middle of the length of said foil tape; a number of additional copper windings each wrapped around said windings; wherein: said insulation has an insulation thickness (d.sub.i) determined according to a formula of: d.sub.i>u.sub.n2, pic*/(E.sub.n2, pic.Math.m), where: u.sub.n2, pic is a conventionally predetermined maximum peak voltage between adjacent turns of said windings, E.sub.n2, pic is a conventionally predetermined maximum electric field strength of the insulation; and said insulation is made of ferroelectric material having a chemical formula of Fe.sub.2O.sub.3.

2. The transformer of claim 1, wherein; said transformer is used in an electric power grid; the layer of said foil tape has a layer thickness defined by the following equation: d.sub.Fe≈20.Math.(100/S).sup.1/3.Math.(50/j).sup.1/2, where: S is a power of said transformer, f is a frequency of the electric power grid; and a ratio of said layer thickness to said insulation thickness (d.sub.Fe/d.sub.i) is ranged from 5:1 to 10:1.

3. A transformer comprising: a number of windings each having a vertical cross-section, said windings are made of a foil tape having a length, said windings are wound by m layers coated with an interlayer insulation, wherein said m is an even positive number; said layers each is made of ferromagnetic metal; said windings each has—upper ends connected through a first yoke and—bottom ends connected through a second yoke; said windings each, in the vertical cross-section, is wrapped by a short-circuited coil; said windings each contains a transposition component for transposition said layers, wherein the transposition component is inserted into a break provided in a middle of the length of said foil tape; a number of additional copper windings each wrapped around said windings; wherein: said insulation has an insulation thickness (d.sub.i) determined according to a formula of: d.sub.i>u.sub.n2, pic*/(E.sub.n2, pic.Math.m), where: u.sub.n2, pic is a conventionally predetermined maximum peak voltage between adjacent turns of said windings, E.sub.n2, pic is a conventionally predetermined maximum electric field strength of the insulation; and said insulation has a structure consisting of a plurality of pairs of alternating Cu layers having a Cu thickness, and Fe layers having a Fe thickness, wherein a ratio of the Cu thickness to the Fe thickness is equal to 5:100.

4. An interlayer insulation used for a ferromagnetic winding having an even positive number m of layers; said insulation is coated on the layers: wherein: said insulation has an insulation thickness (d.sub.i) determined according to a formula of: d.sub.i>u.sub.n2, pic*/(E.sub.n2, pic.Math.m), where: u.sub.n2, pic is a conventionally predetermined maximum peak voltage between adjacent turns of said winding, E.sub.n2, pic is a conventionally predetermined maximum electric field strength of the insulation; and either said insulation is made of Fe.sub.2O.sub.3, or said insulation has a structure consisting of a plurality of pairs of alternating Cu layers having a Cu thickness, and Fe layers having a Fe thickness, wherein a ratio of the Cu thickness to the Fe thickness is equal to 5:100.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic cross-sectional view of the transformer comprising the ferromagnetic foil windings and which is taken as the closest related art for this invention.

(2) FIG. 2 shows an isometric view of the ferromagnetic foil windings of the transformer shown on FIG. 1.

(3) FIG. 3 and FIG. 4 show a vertical section (A) of the foil winding, whose turns are numbered as 1, 2, 3, . . . , n, n+1, . . . , N and are made out of a tape which has an even m-number of layers of ferromagnetic metal.

(4) FIGS. 5-9 show graphs of empirical dependences of control of ferromagnetic metal parameters in the foil windings, which have interlayer insulation with improved dielectric constant c, related to different thicknesses d.sub.i of the improved insulation.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

(5) While the invention may be susceptible to embodiment in different forms, there are described in detail herein below, specific embodiments of the present invention, with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as illustrated and described herein.

(6) The inventive object is achieved by the use of special materials for interlayer insulation, which allows increasing the flow of an electric field, therefore, providing an increase of boundaries values of the control range of this field up to the ample values.

(7) The inventive transformer comprises: a number (not limited, for example, 2) of ferromagnetic windings 1 having a vertical cross-section, the ferromagnetic windings 1 are made of a foil tape having a length and wound by an even plurality of layers 6 coated with insulation 7; the layers 6 each is made of ferromagnetic metal 9 wherein, on the external side in relation to the corresponding winding 1, the layer 6 is plated by antiferromagnetic metal 10 and, on the internal side in relation to the corresponding winding 1, the layer 6 is plated by antiferromagnetic metal 11 capable of transferring into a ferromagnetic; the windings 1 each has—upper ends connected through a first yoke 2 and—bottom ends connected through a second yoke 3; the windings 1 each, in the vertical cross-section, is wrapped by a short-circuited coil 4; the windings 1 each contains a component 5 (described in RU2444077) for transposition the layers 6, wherein the component 5 is inserted into a break provided in a middle of the length of the foil tape.

(8) The inventive transformer also comprises: a number of additional copper windings 8 each wrapped around the windings 1.

(9) A distinct feature of the inventive transformer is the material of insulation 7, which is either ferroelectric, or multilayer metallic antiferromagnetic having a plurality of ferromagnetic layers with a strong interaction therebetween, capable of ensuring stability of the ferromagnetic layers against external magnetic and electric fields and insulator properties in the direction of the transition from one of the layers to another such layer.

(10) The transformer's design is similar to the above described related art design, shown on FIG. 1, and has similar windings 1 made of ferromagnetic foil. But, unlike the related art transformer, wherein insulation 7 (shown on FIGS. 3 and 4) is made of a conventional dielectric with relative permittivity ∈*≈3 . . . 6, the insulation 7 in the claimed transformer is made of ferroelectric with a relative permittivity ∈>10.sup.4, or is made of a laminated metallic antiferromagnetic material having anisotropic insulation properties in the direction of the transition from one its layer to another, having an effective relative permittivity ∈>>10.sup.4 and is stable against external magnetic and electric fields at temperature up to +350° C. and more.

(11) The use of ferroelectrics as interlayer insulation in the foil windings of transformers is previously unknown, and therefore the corresponding embodiments of the claimed invention are novel. The application of the laminated metallic antiferromagnetic as anisotropic insulation is also previously unknown, and therefore the corresponding embodiments of the claimed invention are also novel.

(12) Examples of Operation of the Invention

(13) In a preferred embodiment, the inventive transformer operates as follows.

(14) When an alternative voltage u.sub.1(1) is applied to the terminals of a first copper winding 8 (left), which has N.sub.1(1) number of turns, on the terminals of a second copper coil 8 (right), the emf will be induced, which is determined by the classical equation: u.sub.1(2)=u.sub.1(1).Math.[N.sub.1(2)/N.sub.1(1)]=u.sub.1(1).Math.k.sub.tr(1), i.e. in this case differences in work of a transformer with ferromagnetic foil windings and work of a conventional electromagnetic transformer with the same ratio of turns k.sub.tr(1)=N.sub.1(2)/N.sub.1(1) are not observed. However, in this case on the terminals of the ferromagnetic foil winding 1 with a N.sub.2(1) number of turns a voltage u.sub.2(1)=u.sub.1(1).Math.[N.sub.2(2)/N.sub.1(1)].Math.k.sub.U=u.sub.1(1).Math.k.sub.tr.Math.k.sub.U(2) will be induced, where: k.sub.U—a geometry factor of the winding 1, k.sub.U=(r+2r.sub.0)/(3r+3r.sub.0), r.sub.0 and r—its inner and outer radiuses (Reference [22]). This distinguishes the transformers with foil windings made of ferromagnetic metal from conventional electromagnetic transformers.

(15) During operation of the transformer between the adjacent layers 6 relating to the start and finish ends of an every nth turn of the foil winding arises the electrical potential difference u.sub.n2*≈(u.sub.n2.sup.2+i.sub.2.sup.2.Math.R.sub.n2.sup.2).sup.1/2, where: u.sub.n2—the emf of the n-th turn, when it is secondary, or its counter-emf, if it is primary; R.sub.n2—its active resistance; i.sub.2—current flowing through the foil winding. Therefore, between these layers 6, the number of which in this turn is equal to m, arises an electric field with the strength E.sub.n2=u.sub.n2*/(d.sub.i.Math.m), where: d.sub.i—thickness of insulation 7 between the layers 6.

(16) In proportion to the increase of the flux density of electric field between the adjacent layers 6 (which also depends of the relative permittivity c of this insulation, according to the equation: D.sub.n2=∈.sub.0.Math.∈.Math.E.sub.n2), the influence of the electric field on the layers 6 increases as well. Here: ∈.sub.0—electric constant in the SI-system of the measurements.

(17) Under this action of the electric field, a redistribution of conduction electrons in the volumes of adjacent metal layers 6 occurs, which induces the same redistribution in the density of conductivity electrons in other coterminous layers 6 for all N turns of the ferromagnetic foil winding 1, as shown in the vertical section A on FIG. 4. This alters the quantitative contents, sizes and shapes of the magnetic hierarchical associations of conductivity electrons, and therefore, anisotropically changes properties of the magnetically interacting layers 6 of the foil windings 1 (References [9], [10], [22]) as follows: in the direction, parallel to the axis of the foil winding 1, it increases the relative magnetic permeability up to a value μ>100′000 almost without changing in the saturation flux density equal to B.sub.s=23′000 gauss, and decreases the coercive force up to a value H.sub.c<10.sup.−4 Oe and the remanence up to a value B.sub.r<100 gauss; longitudinally to the tape, reduces the resistivity up to value ρ<0.001 μOhm×m. However, in the related art (References [17-21]), the maximum flow density of electrical displacement D.sub.n2 in the interlayer volume between the layers of the winding 1 (against influence of which the ferromagnetic material layer 6 is more sensitive, than to the influence of magnetic fields), is limited by a value of relative insulation permittivity equal merely to ∈*=3 . . . 6.

(18) The reduction in the thickness of insulation 7 in order to increase the flow of electrical displacement D.sub.n2 also has a limit, calculated using the ratio of d.sub.i>u.sub.n2, pic*/(E.sub.n2, pic.Math.m), where: u.sub.n2, pic is a maximum peak voltage between the adjacent turns of the foil winding 1, E.sub.n2, pic is a maximal electric field strength in insulation 7 (i.e. a breakdown electric field for the insulation that could be conventionally determined), m—the number of layers in one turn.

(19) In the related art, this limits the control range of induced properties of the material of ferromagnetic foil winding 1, and therefore does not allow to achieve the best of its parameters (see graphs on FIG. 9).

(20) Unlike in the related art transformers, the interlayer insulation 7 of the claimed transformer is made of ferroelectric or made of multilayer antiferromagnetic with strong interaction between its ferromagnetic layers, the intensity of which is sufficient to ensure an insensitivity of the material against external electric and magnetic fields and creates stable electrical insulating properties in the direction across these layers.

(21) Multilayer material with strong antiferromagnetic interaction between its layers (which does not have structure defects), is usually referred to insensitive materials with anisotropic colossal magneto-resistance (Reference [23]). These types of “insulation” have an equivalent relative permittivity ∈>10.sup.4, which is anisotropic, i.e. directed (measured) across the layers of this material, and thus, during operation of the claimed transformer, the flux density of the electric field displacement between the metal layers 6 of the tape becomes (∈/∈*) times greater and proportionally causes higher volume electric charges, which are shown in FIG. 4.

(22) Design Options

(23) Such changing in the concentration of conductivity electrons in the ferromagnetic metal tape in (∈/∈*) times increases the range of adjustment of its magnetization curve which can be implemented by choosing a ratio of the thickness d.sub.Fe of layer 6 and the thickness d.sub.i of interlayer insulation 7, i.e. by design-adjustment of the material in accordance with the empirical equations for these parameters.

(24) Besides, in addition to the adjustment range of the ferromagnetic parameters μ, H.sub.c, B.sub.r, which occurs at the constant achieved parameter B.sub.s in direction of the tapes width, will be changed also the adjustment range for the resistivity ρ of the ferromagnetic in direction of tapes length. The empirical equations to obtain the best parameters of the ferromagnetic metal in the foil windings with interlayer insulation having the improved dielectric constant can be obtained by applying the magnetization curves shown on FIGS. 5-9.

(25) As a winding model (prototype) for obtaining these curves for the claimed transformers, the ferromagnetic foil winding was designed to operate at the 12V-voltage, which had a power of 100 W, and was suitable for electrical power grids with a frequency of f.sub.0=50 . . . 60 Hz.

(26) Measurements were carrying out at a constant value d.sub.Fe of thickness of the metal layer 6, which was equal to 20 μm and consisted of a 18 μm tape of 99.996%-purity iron (Reference [10]) coated by 1 μm of 99.996% manganese (Reference [10]) on a first side and coated by 1 μm of the 99.996% chromium on a second side.

(27) The adjustments, whose results are illustrated in the graphs on FIGS. 5-9, were carried out by varying the thickness d.sub.i of insulation 7 with a relative permittivity ∈.sub.i≈10.sup.4. When d.sub.i≈5 μm the magnetization curve of metal corresponds to weak ferromagnetic or paramagnetic (FIG. 5); when d.sub.i=0.01 . . . 0.05 μm, there were observed a transition from antiferromagnetic (which doesn't respond to the applied external magnetic field, not shown) to magnetically hard ferromagnetic (FIG. 6); at d.sub.i=0.1 . . . 0.5 μm, the magnetization curve corresponds to different types of meta-magnets (FIG. 7 and FIG. 8).

(28) If d.sub.i≈2 μm, then the obtained curve corresponds to a desired ferromagnetic with a high saturation induction B.sub.s≈23,000 gauss and relative magnetic permeability μ>10.sup.6, small values of remanence B.sub.r<100 gauss and of coercive force H.sub.c<0.017 Oe (FIG. 9), while the foil winding 1 also acquires a low electrical resistivity ρ<<0.001 μOhm×m.

(29) The curve shown on FIG. 9 corresponds to the best parameters of the ferromagnetic foil windings, which are achievable for transformers within a power range of S.sub.0=10 W . . . 1 kW, and it was obtained at a thicknesses d.sub.Fe≈20 μm, d.sub.i≈2 μm.

(30) The optimum ratio range of thicknesses of metal 6 and insulation 7 in every layer of the foil winding 1 has is raged from 5:1 to 10:1.

(31) For large transformers (having a power S>S.sub.0), because of a larger electric voltage between the turns of their windings, the thickness of the interlayer insulation of the tape should be (S/S.sub.0).sup.1/3 times greater.

(32) This increase in the insulation thickness reduces the interaction and mutual magnetizing of the ferromagnetic layers and, therefore, reduces the sensitivity of design-adjustment of the electric field up to acceptable values.

(33) In transformers for electrical power grids with a higher frequency f, to eliminate the skin-effect influence, it is required that the thickness d.sub.Fe of each metallic layer 6 in the tape and correspondingly the thickness d.sub.i of the interlayer insulation 7 be decreased approximately (f/f.sub.0).sup.1/2 times. Therefore, the thickness of the metal layer 6 of the multilayer tape may be determined by the empirical equation: d.sub.Fe≈20.Math.(100/S).sup.1/3.Math.(50/f).sup.1/2, μm, where: S—transformer's power, W; f—grid's frequency, Hz.

(34) The multilayered metallic material with a very strong antiferromagnetic interaction of its ferromagnetic layers, which is claimed herein as the alternative (and is a more promising material for the interlayer insulation 7 in the foil windings 1) operates as follows.

(35) When the thicknesses of interlayers of the non-ferromagnetic metal are lower than 5% against the thickness of ferromagnetic metal layers, separated by these interlayers, the spontaneous counter-magnetizing's mutual influence of these ferromagnetic metal layers becomes ten times larger than the influence of a possible peak value of the magnetic field (H.sub.max≧10 kOe), which may be induced externally on the laminate material through other parts of an electromagnetic device, for example, by the currents flowing through the windings during the transformer operation.

(36) Therefore, the system of interacting ferromagnetic layers of multilayer material is a permanently locked spin valve (Reference [23]) for currents in the direction across these layers. Material with such high-energy magnetic interaction of the layers may be fully non-conductive in the directions crossing these layers, without sensitivity to an external electrical field and an external magnetic field, unlike meta-magnets which react to an applied magnetic field even when their strength is barely above 10 kOe.

(37) As the insulation withstanding a 10 V voltage amplitude, induced between the turns of the ferromagnetic foil windings in the transformers with a power exceeding 1 kW, the material containing more than 5 layers of ultra-pure iron with a thickness of about 90 . . . 100 nm and with copper interlayers having a thickness of 5 nm can be applied. Such system of ferromagnetic layers may be regarded also as electrical capacitor's plates separated by potential barriers at the location of magnetic domain walls, which prevents the passage of current across the layers, wherein the barriers have a thickness no more than a few atoms size.

(38) Therefore, this capacitor's capacitance, owing to its thickness (about 0.5 μm), has a value close to a capacitance value of a capacitor, which would have a 2 μm thickness with insulation interlayers made of ferroelectric with the relative permittivity ∈>>10.sup.4. Consequently, multilayered metallic material with very strong antiferromagnetic interaction between its ferromagnetic layers is suitable for use as insulation material of high dielectric permittivity.

(39) Thus, the claimed transformer is provided with a high range of design-adjustment of characteristics of its ferromagnetic foil windings, which allows reducing its sizes in comparison with the related art in more than two-fold and to increase its efficiency up to 99% and higher.

(40) A preferable choice of interlayer insulation 7 for coating the metal layers 6 is a Fe.sub.2O.sub.3 film with the 2 μm thickness and having the properties of the dielectric and ferroelectric, i.e. material with resistivity ρ>10.sup.16 Ohm×m, with a dielectric strength greater than 60 kV/mm and with ∈>10.sup.4.

(41) Another preferable choice of interlayer insulation 7 for coating the metal layers 6 is the multilayer metal material having the 0.5 μm thickness and formed by alternating Cu—Fe—Cu—Fe—Cu . . . layers of super-pure iron and copper with a ratio of corresponding layer thicknesses of 5:100:5:100:5: . . . .

(42) The claimed transformer can be utilized in magneto-electro-technology (as defined by the instant inventors), i.e. in an industry, which uses the properties of layered ferromagnetics for powerful electrical equipment.

(43) The transformer may be adapted for design of single-phase, three-phase, or other transformers with ferromagnetic foil windings, similar to the related art (References [7], [14]-[17]), and may be used as compact power transformers and instrumental transformers with a high reliability in various industrial sectors.

(44) In two-pole connection circuits (i.e. without loading or only with a regulatory loading), the transformer may be used as a choke or reactor. The transformer may be also manufactured for the use in electrical power grids with reactive power compensation.

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