HK1086941B - Bulk amorphous metal inductive device - Google Patents

Description

Bulk amorphous metal inductive device

Technical Field

The present invention relates to inductive devices, and more particularly, to a high efficiency, low core loss inductive device having a core assembled from a plurality of bulk amorphous metal magnetic components.

Background

Induction devices are a major component of many modern electrical and electronic equipment, and most commonly include transformers and inductors. Most of these devices employ a core comprising a soft ferromagnetic material and one or more electrical windings surrounding the core. Inductors typically employ a single winding having two terminals and act as a filter and energy storage device. Transformers typically have two or more windings. They transform the voltage from one level to at least one other desired level and electrically isolate different parts of the overall circuit. The inductive device may have widely varying dimensions with correspondingly varying power capabilities. Different types of inductive devices are optimized for operation at frequencies over a very wide range from Direct Current (DC) to gigahertz (GHz). In fact, every known type of soft magnetic material finds application in the construction of inductive devices. The selection of a particular soft magnetic material depends on the needThe nature of the material, the availability of the material in a form such that the material itself is efficiently manufactured, and the combination of volume and cost required to service a given market. Generally, it is desirable for the soft ferromagnetic core material to have a high saturation induction B to minimize the core size_satAnd a low coercive force H_eHigh permeability μ, and low core loss to maximize efficiency.

Components such as motors and small to medium sized inductors and transformers for electrical and electronic devices are typically constructed using laminated structures stamped from various grades of magnetic steel supplied in sheet material having a thickness as low as 100 μm. The laminate structure is typically laminated and secured and then wound with the required electrical winding or windings, which typically comprise high conductivity copper or aluminum wire. These laminated structures are typically used in iron cores in various known shapes.

Many shapes for inductors and transformers are assembled from constituent parts that generally have the form of certain printed letters, such as "C", "U", "E" and "I", through which the parts are identified. The assembled shape may further be represented by letters that reflect the constituent parts, e.g., an "E-I" shape is made by assembling an "E" part with an "I" part. Other widely used package shapes include "E-E", "C-I", and "C-C". The constituent components for prior art cores having these shapes have been constructed from both conventional crystalline ferromagnetic metal laminates and machined bulk soft ferrite blocks.

Although many amorphous metals provide superior magnetic properties compared to other common soft ferromagnetic materials, certain of their physical properties make conventional fabrication techniques difficult or impossible. Amorphous metal is typically supplied as a thin, continuous strip of material having a uniform strip width. However, amorphous metals are actually thinner and harder than all conventional metallic soft magnetic alloys, and thus the punching or stamping of conventional laminated structures results in excessive wear of the manufacturing tools and dies, which leads to rapid failure. The resulting increase in processing and manufacturing costs makes the fabrication of bulk amorphous metal magnetic components using such conventional techniques commercially impractical. The thinner nature of amorphous metal also translates to an increase in the number of laminations required to form a component having a given cross-section and thickness, which further increases the overall cost of the amorphous metal magnetic component. The machining techniques used to shape ferrite blocks are also generally not suitable for machining amorphous metals.

The properties of amorphous metals are typically optimized by annealing processes. However, such annealing typically renders the amorphous metal very brittle and also complicates conventional manufacturing processes. As a result of the aforementioned difficulties, techniques that are widely and easily used to form shaped laminations of silicon steel and other similar metallic sheet-form FeNi-and FeCo-based crystalline materials have not been found to be suitable for the manufacture of amorphous metal devices and components. Amorphous metals have therefore not been accepted by the market for many devices; this is the case, although there is a great potential for improvement in size, weight and energy efficiency that should be realized in principle from the use of high magnetic induction, low loss materials.

For electronic applications, such as saturable reactors and some chokes, amorphous metal has been employed in the form of a spirally wound, circular toroidal core. Devices in this form are commercially available, typically in the range of a few millimeters to a few centimeters in diameter and are commonly used in switched mode power supplies supplying up to a few hundred volt-amperes (VA). This core configuration provides a fully closed magnetic circuit with a negligible demagnetization factor. However, to achieve the desired energy storage capacity, many inductors include a magnetic circuit with a discontinuous air gap. The presence of the gap results in a non-negligible demagnetization factor and associated shape anisotropy, which are evident in the sheared magnetization loop. The shape anisotropy can be much higher than the possible induced magnetic anisotropy, which proportionally increases the energy storage capacity. Toroidal cores and conventional materials with discontinuous air gaps have been proposed for such energy storage applications. However, the annular geometry with the gap provides only minimal design flexibility. It is often difficult or impossible for the device user to adjust the gap to select the desired degree of shear and energy storage. Furthermore, the equipment required to apply the windings to the toroidal core is more complex, expensive and difficult to operate than comparable winding equipment for laminated cores. Cores with toroidal geometries are generally not useful in high current applications because the large diameter wires that dictate the rated current cannot be bent to the extent required for toroidal windings. Furthermore, the toroidal design has only a single magnetic circuit. As a result, they are not well adapted and are difficult to adapt to multi-phase transformers and inductors, including particularly common three-phase devices. Other configurations are therefore sought that are more amenable to easy manufacture and application.

Furthermore, the inherent stresses in the band-wound toroidal core cause certain problems. The windings inherently place the outer surface of the strip in tension and the inner surface in compression. The linear tension required to ensure a smooth winding contributes to the creation of additional stress. As a result of magnetostriction, the wound toroidal core typically exhibits a magnetic property that is worse than the magnetic property measured with the same strip in a flat strip configuration. The annealing process is typically only capable of relieving a portion of the stress, thus eliminating only a portion of the degradation. Furthermore, having the wound toroidal core frequently create gaps leads to additional problems. Any residual hoop stress in the wound structure is at least partially removed due to the formation of the gap. In fact, the net hoop stress is unpredictable and either compressive or tensile. The actual gap tends to close or open an unpredictable amount in each case as needed to establish a new stress balance. As a result, the final gap is often different from the expected gap, lacking corrective measures. Since the reluctance of the core is largely determined by the gap, the magnetic properties of the finished core are often difficult to reproduce on a consistent basis in a mass production process.

Amorphous metals have also been used in transformers for much higher power devices, such as distributed transformers with nameplate ratings of 10kVA to 1MVA or more for power networks. The cores for these transformers are typically formed into a step-seam wound, generally rectangular configuration. In one common construction method, a rectangular core is first formed and annealed. The core is then unbounded to allow the preformed windings to slide over the long legs of the core. After the introduction of the preformed windings, the layers are tightened and fastened again. A typical process for constructing a distributed transformer in this manner is set forth in U.S. patent No. 4,734,975 to Ballard. This process understandably requires a significant amount of manual labor and processing steps, including brittle annealed amorphous metal ribbon. These steps are particularly tedious and difficult to accomplish for cores less than 10 kVA. Furthermore, in this configuration, the core is not susceptible to the controlled introduction of air gaps required for many inductor applications.

Another difficulty associated with the use of ferromagnetic amorphous metals arises from the phenomenon of magnetostriction. Some of the magnetic properties of any magnetostrictive material change in response to applied mechanical stress. For example, when a component comprising amorphous material is subjected to stress, its magnetic permeability generally decreases and its core loss increases. Degradation of the soft magnetic properties of amorphous metal devices due to magnetostriction phenomena may be due to stress induced magnetostriction phenomena resulting from any combination of origins including deformation during core fabrication, mechanical stresses resulting from mechanically clamping or otherwise securing the amorphous metal in place, and internal stresses resulting from thermal expansion and/or expansion due to magnetic saturation of the amorphous metal material. As amorphous metal magnetic devices are stressed, the efficiency at which they direct or concentrate magnetic flux is reduced, which results in higher magnetic losses, reduced efficiency, increased heat generation, and reduced power. The extent of this degradation is usually considerable. Depending on the particular amorphous material and the actual strength of the stress, as described in U.S. patent 5,731,649.

Amorphous metals have much lower anisotropy energy than many other conventional soft magnetic materials, including common electrical steels. Stress levels that have a detrimental effect on the magnetic properties of these conventional metals have a severe impact on magnetic properties such as permeability and core loss, which are important for inductive components. For example, the' 649 patent teaches forming an amorphous metal core by winding amorphous metal into a coil, which has a laminate structure using epoxy, which detrimentally limits the thermal and magnetic saturation expansion of the coil of material. High internal stresses and magnetostriction are thus generated, which reduces the efficiency of motors and generators comprising such cores. To avoid stress induced magnetic degradation, the' 649 patent discloses a magnetic component that includes a plurality of stacked or coiled portions of amorphous metal that are carefully mounted or included in a dielectric sleeve without bonding using an adhesive.

A significant trend in recent technology has been the design of power sources, converters and related circuits that utilize switched-mode circuit topologies. The increased capabilities of available power semiconductor switching devices have allowed switch mode devices to operate at increasingly high frequencies. Many devices previously designed with linear regulation and operating at a line frequency (typically 50-60Hz in the grid or 400Hz in military applications) are now based on switch mode regulation at frequencies typically 5-200kHz and sometimes up to 1 MHz. The primary drive power for increasing the frequency is the concomitant reduction in the size of the required magnetic components. However, the increase in frequency also significantly increases the magnetic losses of these components. There is therefore a significant need to reduce these losses.

The limitations of magnetic components impose considerable and undesirable design compromises with existing materials. In many applications, core loss of ordinary electrical steel is prohibitive. In this case, the designer must be forced to use permalloy or ferrite as an option. However, the accompanying decrease in saturation induction (e.g., 0.6-0.9T or less for various permalloys and 0.3-0.4T for ferrites, as opposed to 1.8-2.0T for ordinary electrical steels) makes it necessary to increase the size of the resulting magnetic component. In addition, the desired soft magnetic properties of permalloys are adversely and irreversibly affected by plastic deformation that can occur at relatively low stress levels. Such stresses may occur during the manufacture or operation of the permalloy component. Although soft ferrites generally have an attractive low loss, their low magnetic induction values result in impractical large devices for many applications where space is an important consideration. Furthermore, the increased size of the core undesirably necessitates a longer electrical winding, so ohmic losses increase.

Despite the advances shown in the above disclosure, there remains a need in the art for improved inductive devices that exhibit the combination of superior magnetic and physical properties required by the current demands. Construction methods that efficiently utilize amorphous metals and can be implemented for high volume production of various types of devices are also sought.

Disclosure of Invention

The present invention provides a high efficiency inductive device including a plurality of low loss bulk amorphous metal magnetic components. Such components are assembled in juxtaposed relation to form a magnetic core having at least one magnetic circuit. They are secured in place by fastening means. At least one electrical winding surrounds at least a portion of the magnetic core. Each component comprises a plurality of substantially similarly shaped, planar layers of amorphous metal strip bonded together by an adhesive to form a substantially multi-face shaped portion having a plurality of mating faces. The thickness of each component is substantially equal. The components are assembled by layers of amorphous metal arranged in each component in generally parallel planes. Each mating face is proximate to a mating face of another component of the device.

The device of the invention advantageously has low core losses. More specifically, when the induction device is excited at an excitation frequency "f" of 5kHz and a peak of 0.3TValue of magnetic induction intensity "B_max"run down, it has a core loss of less than 12W/kg. In another aspect, the device has a core loss less than "L", where L is given by the formula L0.0074 f (B)_max)^1.3+0.000282f^1.5(Bmax)^2.4The measurement units of the iron core loss, the excitation frequency and the peak magnetic induction intensity are respectively given as watt/kilogram, hertz and tesla.

The inductive devices of the present invention are used in a variety of circuit applications. It can be used as a transformer, autotransformer, saturable reactor, or inductor. The components are particularly useful in the construction of power conditioning devices using various switch-mode circuit topologies. The present device is useful in single and multiphase applications, particularly in three phase applications.

The bulk amorphous metal magnetic components are advantageously easy to assemble to form one or more magnetic circuits of a completed inductive device. In some aspects, mating faces of the components are brought into intimate contact to create a device having a low reluctance and a relatively square B-H loop. However, by assembling the device using an air gap disposed between the mating surfaces, the magnetic reluctance is increased, which provides a device with enhanced energy storage capacity that is useful in many inductor applications. The air gap is selectively filled with a non-magnetic spacer. Yet another advantage is that the standard size and shape of a limited number of components can be assembled in many different ways to provide a wide range of electrical characteristics for the device.

The components used to construct the present device preferably have shapes that are substantially similar to the shapes of certain typographic letters, such as "C", "U", "E", and "I", by which the components are identified. Each component has at least two mating faces that are brought into proximity and parallel with a similar number of complementary mating faces on other components. In some aspects of the invention, components having mitered mating surfaces are advantageously employed. The flexibility in the size and shape of the components allows the designer wide latitude to properly optimize the entire core and one or more winding windows therein. As a result, the overall size of the device is minimized, along with the volume of core and required winding material. The combination of flexible device design and high saturation induction of the core material is beneficial in designing electronic circuit devices with compact size and high efficiency. Transformers and inductors with given power and energy storage ratings are generally smaller and more efficient than conventional inductive devices using lower saturation induction core materials. As a result of its very low core loss under periodic excitation, the magnetic device of the present invention can operate at frequencies in the range of DC to 200kHz or higher. It exhibits improved performance characteristics compared to conventional silicon steel magnetic devices operating in the same frequency range. These and other desirable attributes make the present device easy to customize for specialized magnetic applications, such as use as a transformer or inductor in a circuit topology employing switching modes and power conditioning electronics circuits with switching frequencies in the range of 1kHz to 200kHz or higher.

The device is susceptible to being provided with one or more electrical windings. Advantageously, the windings may be formed and slid over one or more of the components in a separate operation, wound onto the bobbin during self-supporting assembly or in coil form. The windings may also be wound directly onto one or more of the components. The difficulty and complexity of providing windings on prior art toroidal cores is thus eliminated.

The present invention also provides a method for constructing a high efficiency inductive device comprising a plurality of bulk amorphous metal magnetic components. One embodiment of the method comprises the steps of: (i) surrounding at least one magnetic component by an electrical winding; (ii) placing the components in a juxtaposed relationship to form the core having at least one magnetic circuit, the layers of each component lying in generally parallel planes; and (iii) securing the components in juxtaposed relation. The assembly of the device advantageously does not impose undue stresses that would unacceptably degrade the soft magnetic properties of the component and the device in which it is included.

Drawings

The present invention will be more fully understood and further advantages will be readily appreciated, with reference to the following detailed description of the preferred embodiments of the invention and the accompanying drawings, wherein like reference numerals refer to like elements throughout the several views, and in which:

FIG. 1 is a perspective view showing an inductive device having a "C-I" shape of the present invention assembled with bulk amorphous metal magnetic components having "C" and "I" shapes;

FIG. 2A is a plan view showing an inductive device of the present invention having a "C-I" shape, wherein the "C" and "I" shaped bulk amorphous metal magnetic components are in mating contact and the "C" shaped component carries electrical windings on each of its legs;

FIG. 2B is a plan view showing an inductive device of the present invention having a "C-I" shape, wherein the "C" and "I" shaped bulk amorphous metal magnetic components are separated by spacers and the "I" shaped components carry electrical windings;

FIG. 2C is a plan view showing an inductive device of the present invention having a "C-I" shape and including a bulk amorphous metal magnetic component having mitered mating faces;

FIG. 3 is a perspective view showing a bobbin carrying electrical windings and adapted to be mounted on a bulk amorphous metal magnetic component included in an inductive device of the invention;

FIG. 4 is a perspective view showing an inductive device of the present invention having an "E-I" shape, assembled using a bulk amorphous metal magnetic component having "E" and "I" shapes and windings disposed on each leg of the "E" shaped component;

FIG. 5 is a cross-sectional view showing a portion of the apparatus shown in FIG. 4;

FIG. 6 is a plan view of an inductive device of the present invention showing the "E-I" shape of a bulk amorphous metal magnetic component comprising the "E" and "I" shapes assembled with an air gap and spacer between the mating faces of the respective components;

FIG. 7 is a plan view of an inductive device of the present invention showing an "E-I" shape in which each mating face of the bulk amorphous metal magnetic component is mitered;

FIG. 8 is a plan view showing the device of the present invention having a general "E-I" shape assembled from five "I" shaped bulk amorphous metal magnetic components, three leg components having one dimension and two back components having another dimension;

FIG. 9 is a plan view showing a square inductive device of the invention assembled from four substantially identical "I" shaped bulk amorphous metal magnetic components;

FIG. 10 is a perspective view showing a bulk amorphous metal magnetic component having a generally rectangular prism shape used in the construction of the inductive device of the present invention;

FIG. 11 is a perspective view showing an arcuate bulk amorphous metal magnetic component used in constructing the inductive device of the present invention;

FIG. 12 is a schematic diagram of an apparatus and process for forming a rectangular bar of laminated strip of amorphous metal strip from which one or more bulk amorphous metal magnetic components of the present invention are cut;

FIG. 13 is a perspective view showing a rod of a laminate strip of amorphous metal strip designated to be cut to form a trapezoidal bulk amorphous metal magnetic component for use in constructing an inductive device of the invention;

FIG. 14 is a plan view of an inductive device of the present invention having a quadrilateral shape, assembled from four trapezoidal bulk amorphous metal magnetic components;

FIG. 15 is a schematic illustration of an apparatus and process for forming a rectangular toroidal core of laminated strips of amorphous metal strip from which one or more bulk amorphous metal magnetic components of the present invention are cut; and

fig. 16 is a perspective view of a generally rectangular core of laminated amorphous metal strip designated for cutting to form a bulk amorphous metal magnetic component for use in constructing an inductive device of the invention.

Detailed Description

The present invention is directed to high efficiency inductive devices, such as inductors and transformers. The device employs a magnetic core comprising a plurality of low-loss bulk ferromagnetic amorphous metal components assembled to form at least one magnetic circuit. Generally, the polyhedrally shaped bulk amorphous metal components constructed in accordance with the present invention can have a variety of geometries, including rectangular, square, and trapezoidal prisms, and the like. In addition, any of the aforementioned geometries may comprise at least one arcuate surface, and preferably two oppositely disposed arcuate surfaces, to form a generally curved or arcuate bulk amorphous metal component. The inductive device also includes at least one conductive winding.

The device of the present invention is preferably assembled from constituent parts having an overall shape substantially similar to the shape of certain typographic letters, such as "C", "U", "E" and "I", by which the parts are identified. The finished device is often represented by letters that represent the shape of two or more of the constituent parts. For example, "C-I", "E-E", "C-C" and "C-I-C" devices can be conveniently formed by the components of the present invention. Each component further comprises a plurality of planar layers of amorphous metal having a substantially similar shape. The layers are stacked to substantially the same height and packing density and joined together to form the component. The device is assembled by fastening the components in adjacent relationship using fastening means to form at least one magnetic circuit. In the assembled configuration, the layers of amorphous metal strip in each component lie in generally parallel planes. Each component has at least two mating faces that are close to and parallel with a similar number of complementary mating faces on other components. Some shapes, such as C, U, and E-shapes, terminate in mating faces that are generally substantially coplanar. An "I" (or rectangular prism) may have two parallel mating faces at its opposite ends or one or more mating faces on its long sides. The mating faces are preferably perpendicular to the plane of the constituent strips in the component to minimize core losses. Some embodiments of the invention also include a bulk magnetic component having mating faces that are mitered relative to the elongated direction of the features of the component.

In some aspects of the present invention, when forming an induction device having a single magnetic circuit, two magnetic members each having two mating faces are used. In other aspects, the component has more than two mating faces or the device has more than two components; thus, some of these embodiments also provide more than one magnetic circuit. As used herein, the term magnetic circuit denotes a path along which successive lines of magnetic flux are caused to flow by imposition of a magnetomotive force generated by a current-carrying winding surrounding at least a portion of the magnetic circuit. A closed magnetic circuit is a path in which the magnetic flux is exclusively within the core of magnetic material, while the open part of the flux path is outside the core material, e.g. across an air gap or a non-magnetic spacer between the parts of the core. The magnetic circuit of the device of the invention is preferably relatively closed, the flux path lying predominantly within the magnetic layers of the components of the device but also traversing at least two air gaps between adjacent mating faces of the respective components. The amount of opening of the magnetic circuit can be determined by the fraction of the total reluctance contributed by the air gap and the magnetically permeable core material. The magnetic circuit of the device preferably has a reluctance to which the gap contributes at most ten times the contribution of the magnetically permeable member.

Referring in detail to fig. 1, there is shown primarily one form of the inductive device 1 of the present invention having a "C-I" shape comprising a "C" shaped magnetic component 2 and an "I" shaped magnetic component 3. The "C" -shaped member 2 further includes a first side leg 10 and a second side leg 14, each extending perpendicularly from a common side of the back 4 and terminating distally at a first rectangular mating surface 11 and a second rectangular mating surface 15, respectively. The mating faces are typically substantially coplanar. Side legs 10, 14 depend from opposite ends of one side of the back 4. The "I" component 3 is a rectangular prism having a first rectangular mating face 12 and a second rectangular mating face 16, both on a common side of the component 3. The mating faces 12 and 16 have a size and a spacing therebetween that is complementary to the spacing between the corresponding mating faces 11, 15 at the ends of the legs 10, 14 of the component 2. Each side leg 10, 14, the back 4 between said side legs and the I-part 3 have a cross section of substantially rectangular geometry, all said parts and parts preferably having substantially the same height, width and effective magnetic area. By effective magnetic area is meant the area within the cross-section of the geometric shape occupied by the magnetic material, which is equal to the product of the total geometric area and the lamination factor.

In one aspect of the invention, best shown in fig. 2A, the complementary mating surfaces 11, 12 and 15, 16, respectively, are brought into intimate contact during assembly of the C-I device 1. This arrangement provides a low reluctance of the device 1 and an accompanying relatively square B-H magnetization loop. In another aspect, referring to fig. 2B, optional spacers 13, 17 are inserted between the corresponding mating faces of the components 2, 3 to provide a gap, known as an air gap, between the components in the magnetic circuit. The spacers 13, 17 are preferably constructed of a non-conductive, non-magnetic material having sufficient thermal resistance to resist degradation or deformation due to exposure to temperatures encountered in assembly and operation of the device 1. Suitable spacer materials include ceramic and polymeric materials and plastic materials such as polyimide film and kraft paper. The width of the gap is preferably set by the thickness of the spacers 13, 17 and is selected to achieve the desired reluctance and demagnetization factor and the associated degree of shearing of the B-H line of the device 1 required in a given circuit application.

The "C-I" device 1 further comprises at least one electrical winding. In the aspect shown in fig. 1 and 2A, a first electrical winding 25 and a second electrical winding 27 are provided around the respective leg 10, 14. Current flowing in a positive sense, entering at terminal 25a and exiting at terminal 25b causes magnetic flux to flow substantially along path 22 and have the illustrated sense 23 according to the right hand rule. The "C-I" device 1 may be operated as an inductor using one of the windings 25, 27 or using two windings connected in series which contribute to an increased inductance. Alternatively, the C-I device 1 may be operated as a transformer in a manner known in the art of electrical transformers, for example by means of a winding 25 connected as a primary winding and a winding 27 connected as a secondary winding. The number of turns in each winding is selected according to well known principles in transformer or inductor design. Fig. 2B also shows an alternative embodiment of an inductor configuration with a single winding 28 arranged on the I-component 3.

The at least one electrical winding of the device 1 may be located at any position on either of the components 2, 3, although said winding preferably does not affect any air gap. One convenient way of providing the winding is to wind turns of conductive wire, typically copper or aluminium, on a bobbin having a hollow interior space sized to allow it to slide over one of the legs 10, 14, or onto the I-component 3. Fig. 3 shows one form of bobbin 150 having a body portion 152, an end flange 154 and an internal bore 156 sized to allow bobbin 150 to slide over the desired magnetic component. One or more windings 158 surround the body portion 152. The wire may advantageously be wound on the bobbin 150 in a separate operation using simple winding equipment prior to assembly of the induction device. Bobbin 150, which is preferably composed of a non-conductive plastic such as polyethylene terephthalate resin, provides additional electrical insulation between the windings and the core. In addition, the bobbin provides mechanical protection for the core and windings during manufacture and use of the device. Alternatively, the turns of wire may be wound directly around a portion of one of the components 2, 3. Any known shape of wire may be used, including round, rectangular, and narrow strip shapes.

The assembly of the C-I device 1 is secured to provide mechanical integrity to the finished device and to maintain the relative positioning of the constituent components 2, 3, electrical windings 25, 27, gap spacers 13, 17, if present, and ancillary hardware. The fastening may include any combination of mechanical bonding, clamping, bonding, potting, or the like. The device 1 may also comprise an insulating coating on at least a portion of the outer surface of the components 2, 3. Such a coating is preferably not present on any mating surface 11, 12, 15, 16 in aspects where as low reluctance and intimate contact of the components as possible is desired. The coating is particularly helpful if the windings are applied directly to the components 2, 3, as wear, shortening or other damage to the insulation of the wire windings may otherwise occur. The coating may comprise epoxy or paper or polymer backed tape or other known insulating material wrapped around either component.

Fig. 2C shows another embodiment of the C-I core of the present invention. In this aspect, the iron core 51 includes a C-shaped member 52 and a trapezoidal member 53. The distal ends of legs 10, 14 of C-section 52 are mitered at an inwardly angled angle, preferably 45 °, and terminate at mitered mating surfaces 33, 36. The C-section 52 also has radiused outer and inner vertices 42, 43 at each corner thereof. Such rounded vertices may be present in many of the components used in the described embodiments of the invention. The trapezoidal component 53 terminates in mitered mating faces 34, 37. The mitering of the trapezoidal section 53 is at a complementary angle to the mitering of the C-section 52, preferably also at 45 °. With this mitered angle arrangement, the components 52, 53 can be juxtaposed so that their respective mating faces either come into intimate contact or, as shown in FIG. 2C, are slightly separated to form an air gap into which the spacers 33, 38 can be selectively inserted.

Fig. 4-6 illustrate aspects of the invention that provide an "E-I" device 100 that includes constituent components having "E" and "I" shapes. The E-part 102 comprises a plurality of layers made of ferromagnetic metal strips. Each layer has substantially the same E shape. The layers are joined together to form an E-part 102, the E-part 102 having a substantially uniform thickness and having a back 104 and a middle leg 106, a first side leg 110, and a second side leg 114. Each of the medial 106 and lateral legs 110, 114 extends perpendicularly from a common side of the back 104 and terminates distally in a rectangular face 107, 111, 115, respectively. The middle leg 106 depends from the middle of the back 104, while the side legs 110, 114 depend from opposite ends of the same side of the back 104, respectively. The lengths of the middle leg 106 and the side legs 110, 114 are generally substantially the same such that the respective faces 107, 111, 115 are substantially coplanar. As shown in fig. 5, the cross-section a-a of the back portion 104 between the middle leg portion 104 and either of the side leg portions 110, 114 is generally rectangular, having a thickness defined by the height of the stacked layers and a width defined by the width of each of the layers. The width of section a-a of back 104 is preferably selected to be at least as wide as any of faces 107, 111, 115.

The I-component 101 has a rectangular prism shape and comprises a plurality of layers made of ferromagnetic metal strips, the same as the layers in the E-component 102. The layers are bonded together to form an I-component 101 having a substantially uniform thickness. The I-component 101 has a thickness and width substantially equal to the thickness and width of the section A-A of the back 104 and has a length substantially the same as the length of the E-component 102 measured between the outer surfaces of the side legs 110, 114. A middle mating face 108 is provided in the middle of one side of the I-component 101, while a first end mating face 112 and a second end mating face 116 are located at opposite ends of the same side of the component 101. Each mating face 107, 111, 115 is substantially identical in size to the complementary face 108, 112, 116, respectively.

As also shown in fig. 4 and 6, assembly of the device 100 includes (i) providing one or more electrical windings, such as windings 120, 121, 122, that surround one or more portions of the component 102 or 101; (ii) align and bring the E-component 102 and the I-component 101 close with all layers in them in substantially parallel planes; and (iii) mechanically fastening the components 101 and 102 in juxtaposed relation. The components 102 and 101 are aligned so that the faces 107 and 108, 111 and 112, and 115 and 116, respectively, are in proximity. The spaces between the corresponding faces define three air gaps having substantially the same thickness. Spacers 109, 113 and 117 are selectively placed in these gaps to increase the reluctance and energy storage capacity of each magnetic circuit in device 100. Alternatively, the corresponding faces may be brought into intimate contact to minimize air gaps and increase initial reluctance.

The "E-I" device 100 may be included in a single-phase transformer having a primary winding and a secondary winding. In one such embodiment, winding 122 serves as the primary winding and the series-connected windings 120 and 121 serve as the secondary windings. In this embodiment, the width of each side leg 110 and 114 is preferably at least half the width of the middle leg 106.

The embodiments in fig. 4-6 schematically provide three magnetic circuits having vias 130, 131 and 132 in the "E-I" device 100. As a result, the apparatus 100 can be used as a three-phase inductor with three legs each carrying a winding for one of the three phases. In another embodiment, the "E-I" device 100 may be used as a three-phase transformer, with each leg carrying both primary and secondary windings for one of the multiple phases. In most embodiments of E-I devices intended for three-phase circuits, the legs 106, 110, 114 preferably have equal widths to better balance the three phases. In some particular designs, different legs may have different cross-sections, different gaps, or different numbers of turns. Those of ordinary skill in the art will readily appreciate other forms suitable for various multiphase applications.

Fig. 7 shows another E-I embodiment, in which an E-I device 180 includes a mitered E-section 182 and a mitered I-section 181. The distal ends of the middle leg 106 of the component 182 are mitered with a symmetrical slope on each side of the component to form mating faces 140a and 140b, and have inwardly sloped miters at the distal ends of the outer legs 110, 114 to form mitered mating faces 144, 147. The I-piece 181 is mitered at its ends at angles complementary to the miters of the legs 110, 114 to form mitered end mating faces 145, 148, and at its middle with a generally V-shaped cut-out to form mating faces 141a and 141b complementary to the miters of the legs 106. Each of said faces is preferably mitered at an angle of 45 ° to the longitudinal direction of the respective portion of the component on which said face is located. The length of legs 106, 110, 114 is selected to allow components 181, 182 to be brought into juxtaposition either by close contact or by corresponding mating faces spaced by a gap in which optional spacers 142, 146 and 149 are seated. The mitering of the mating surfaces as shown in fig. 2C and 7 advantageously increases the area of the mating surfaces and reduces leakage flux and localized excessive eddy current losses.

Components having an I-shape are particularly convenient for the practice of the present invention where magnetic devices having a variety of configurations can be assembled from several standard I components. With such components, a designer can readily select a configuration to produce a device having the electrical characteristics required for a given circuit application. For example, many applications for which the E-I device 100 shown in fig. 4 is suitable may also be generally implemented using a device 200 having an arrangement of five rectangular prism magnetic components as shown in fig. 8. The components include a first back component 210 and a second back component 211 having substantially the same dimensions; and a middle leg member 240, a first end leg member 250 and a second end leg member 251 having substantially the same dimensions. Each of the five components 210, 211, 240, 250 and 251 comprises layers of ferromagnetic tape laminated to produce components having substantially the same stack height, but the back and leg components typically have different respective lengths and widths. The component is arranged with all layers of amorphous metal therein lying in parallel planes. Appropriate selection of the dimensions of the components provides windows to accommodate electrical windings that are optimized using principles recognized in the art. The windings are preferably provided on legs 240, 250 and 251 in a similar manner to the configuration in device 100. Alternatively or additionally, the windings may be mounted on either or both of the back members 210, 211 between the legs. Spacers are selectively placed in the gaps between the components of device 200 to adjust the reluctance of the magnetic circuit of device 200 in the manner discussed above in connection with device 100. A beveled engagement similar to that shown in fig. 2C and 7 may be advantageous in some instances.

One embodiment of the present invention is shown in FIG. 9, where four substantially identical rectangular prism components 301 are assembled in a substantially square configuration. The device 300 thus formed may be used in some applications as an alternative to the "C-I" device shown in fig. 1. Other configurations employing rectangular shaped members having one or more dimensions are useful when constructing the inductive device of the present invention. Those skilled in the art will readily appreciate the configurations and means for constructing an inductive device and are within the scope of the present invention.

As previously mentioned, the apparatus of the present invention utilizes a plurality of polyhedrally shaped members. As used herein, the term polyhedron means a solid having multiple faces or sides. Including, but not limited to, three-dimensional rectangular and square prisms with mutually orthogonal sides, and other shapes with some non-orthogonal sides, such as trapezoidal prisms. Furthermore, any of the aforementioned geometries may comprise at least one and preferably two arcuate surfaces or sides disposed opposite one another to form a generally arcuate shaped component. Referring now to fig. 10, there is shown one form of magnetic component 56 used to construct the device of the present invention and having the shape of a rectangular prism. The component 56 comprises a plurality of layers 57 of generally similarly shaped, generally planar, amorphous metal strip material, which are joined together. In one aspect of the invention, the layers are annealed and then laminated by impregnating them with an adhesive 58, preferably a low viscosity epoxy.

Figure 11 shows another form of component 80 useful in the construction of the inductive device of the present invention. The arcuate section 80 comprises a plurality of arcuate shaped laminated structural layers 81, each of which is preferably part of the annulus. The layers 81 are joined together, thereby forming a polyhedron-shaped member having an outer arcuate surface 83, an inner arcuate surface 84, and end mating surfaces 85 and 86. The component 80 is preferably impregnated with an adhesive 82 that is caused to penetrate into the spaces between adjacent layers. The mating surfaces 85 and 86 are preferably of substantially equal size and perpendicular to the plane of the tape layer 81.

The "U" shaped arcuate member 80, wherein surfaces 85 and 86 are coplanar, is particularly preferred. Arcuate sections, in which the surfaces 85, 86 are at an angle of 120 or 90 relative to each other, are also preferred. Two, three or four such components are easy to assemble separately to form an annular core with a substantially closed magnetic circuit.

Inductive devices constructed from bulk amorphous metal magnetic components in accordance with the present invention advantageously exhibit low core losses. As is well known in the art of magnetic materials, the core loss of a device is the excitation frequency "f" and the magnitude of the peak magnetic induction "B" to which the device is excited_max"is used as a function of. In one aspect, a magnetic device has (i) a core loss less than or approximately equal to 1 watt per kilogram of amorphous metal material when operated at a frequency of approximately 60Hz and a flux density of approximately 1.4 tesla (T); (ii) core losses less than or approximately equal to 20 watts per kilogram of amorphous metal material when operated at a frequency of approximately 1000Hz and a flux density of approximately 1.4 tesla (T); or (iii) core losses less than or approximately equal to 70 watts per kilogram of amorphous metal material when operated at a frequency of approximately 20,000Hz and a flux density of approximately 0.30 Tesla (T). According to another aspect, the magnetic induction magnitude "B" is at the excitation frequency "f" and the peak value_maxThe "under-excited device may have a core loss below" L "at room temperatureWherein L is represented by the formula L ═ 0.0074f (B)_max)^1.3+0.000282f^1.5(Bmax)^2.4The measurement units of the iron core loss, the excitation frequency and the peak magnetic induction intensity are respectively given as watt/kilogram, hertz and tesla.

The component of the present invention advantageously exhibits low core losses when the component, or any portion thereof, is excited in substantially any direction within the plane of the amorphous metal sheets included in the component. The low core loss of the constituent magnetic components of the induction device of the present invention further provides high efficiency to the induction device of the present invention. The low core loss values of the resulting device make the device particularly suitable for use as an inductor or transformer intended for high frequency operation, e.g., for excitation at a frequency of at least about 1 kHz. The core loss of conventional steels at high frequencies often makes them unsuitable for use in such inductive devices. These core loss performance values are applicable to the various embodiments of the present invention regardless of the particular dimensions of the bulk amorphous metal components used to construct the inductive device.

A method of constructing a bulk amorphous metal component for use in the apparatus of the invention is also provided. In one embodiment shown in fig. 12, a continuous ribbon 22 of ferromagnetic amorphous metal strip material is fed from a roll 30 through a cutting blade 32 that cuts a plurality of ribbons 92 of identical shape and size. The strips 92 are laminated to form a rod 90 of laminated amorphous metal strip material. The rod 90 is annealed and the layers 92 are bonded to each other by the activated and cured adhesive. The rod 90 is preferably impregnated with a binder, such as a low viscosity, thermally active epoxy. The rod is cut to produce one or more generally three-dimensional components having a desired shape, such as a generally rectangular, square, or trapezoidal prism shape. In one aspect of the invention, the bar 90 is cut along cut lines 98, as shown in FIG. 13, to produce a plurality of trapezoidal shaped members 96 joined by impregnated epoxy 94. The cut lines 98 are preferably oriented at alternating 45 ° angles with respect to the parallel long sides of the bar 90. In one aspect, this cutting process is used to form two pairs of parts, the members of each pair of parts having substantially the same dimensions. The two pairs of components may be assembled as shown in fig. 14 by mating the 45 faces to form a four-sided rectangular configuration 99 having a beveled joint and having the pairs of components on opposite sides of the quadrilateral. The beveled joint enlarges the contact area at the respective joint and reduces the detrimental effects of increased leakage flux and core loss.

In another aspect of the method of the present invention, a rectangular prismatic bulk amorphous metal magnetic component is formed by winding a single ferromagnetic amorphous metal strip 22 or a group of ferromagnetic amorphous metal strips 22 around a generally rectangular mandrel 60 to form a generally rectangular wound core 70, as shown in fig. 15 and 16. The core 70 is annealed and the layers are preferably bonded to each other by impregnating with an activated and cured adhesive. Low viscosity, thermally active epoxy resins are preferred. Two rectangular parts can be formed by cutting the short sides 74, leaving rounded corners 76 connected to the long sides 78a and 78 b. Additional magnetic features may be formed by removing fillets 76 from the long sides 78a and 78b and cutting the long sides 78a and 78b at one or more locations, such as those shown by dashed lines 72. In the example shown in fig. 16, the cutting forms a bulk amorphous metal component having a generally three-dimensional rectangular shape, although other three-dimensional shapes, such as, for example, shapes having at least one trapezoidal or square face, are contemplated by the present invention.

In the practice of the present invention, bonding means are used to bond a plurality of sheets or laminations of amorphous metal strip material in proper alignment with one another to provide a bulk three-dimensional object. The joint provides sufficient structural integrity that allows the present component to be handled and incorporated into larger structures without the attendant excessive stresses that can lead to high core losses or other unacceptable magnetic degradation. A variety of adhesives may be suitable, including those comprising epoxies, varnishes, anaerobic adhesives, cyanoacrylates, and Room Temperature Vulcanizing (RTV) silicone materials. It is desirable for the adhesive to have low viscosity, low shrinkage, low elastic modulus, high tear strength, and high dielectric strength. The adhesive may cover any portion of the surface area of each laminate structure sufficiently to achieve sufficient bonding of adjacent laminate structures to one another and thereby provide sufficient strength to provide mechanical integrity to the finished component. The adhesive may cover substantially all of the surface area. The epoxy may either be multi-component, the cure of which is chemically active, or one-component, the cure of which is thermally active or cured by exposure to ultraviolet radiation. The binder preferably has a viscosity of less than 1000cps and a coefficient of thermal expansion approximately equal to that of the metal or about 10 ppm.

Suitable methods for applying the adhesive include dipping, spraying, brushing, and electrostatic deposition. Amorphous metal in the form of a strip or ribbon may also be coated by passing it over rods or rollers that transfer adhesive to the amorphous metal. Rollers or rods having a textured surface, such as gravure or wire-wound rollers, are particularly effective for transferring a uniform coating of adhesive to the amorphous metal. The adhesive may be applied to the individual amorphous metal layers at a time, either to the strip material before cutting or to the laminate structure after cutting. Alternatively, the adhesive means may be collectively applied to the laminate structure after the laminate structure is laminated. The stack is preferably impregnated by capillary flow of adhesive between the laminated structures. The impregnation step may be carried out at ambient temperature and pressure. Alternatively, the stack is placed in either a vacuum or under clean water pressure to achieve more complete filling while minimizing the total amount of adhesive added. This procedure ensures a high stacking factor and is therefore preferred. Preferably, a low viscosity adhesive is used, such as epoxy or cyanoacrylate. Moderate heating may also be used to reduce the viscosity of the adhesive, thereby enhancing its penetration between the laminate structure layers. The adhesive is activated as needed to promote its bonding properties. After the binder has been subjected to any desired activation and curing, the component may be subjected to final processing to at least one of remove any excess binder, provide the component with a suitable surface finish, and provide the component with final component dimensions. Activation or curing of the binder, if performed at a temperature of at least about 175 deg.c, may also be used to affect magnetic properties, as discussed in more detail below.

One preferred binder is a thermally activated epoxy sold by the company p.d. george under the trade name Epoxylite 8899. The device of the invention is preferably attached by impregnating this epoxy, diluting it to a 1: 5 volume ratio with acetone to reduce its viscosity and enhance its penetration between the layers of the strip. The epoxy may be activated and cured by exposure to elevated temperatures, for example, in the range of about 170 to 180 ° for a time in the range of about 2 to 3 hours. Another binder found to be preferred is methyl cyanoacrylate sold under the trade name Permabond 910FS by National Starch and chemistry. The device of the invention is preferably attached by applying such an adhesive so that it will penetrate between the layers of the strip by capillary action. Permabond 910FS is a one-component, low viscosity liquid that will cure in the presence of moisture at room temperature within 5 seconds.

The present invention also provides a method of assembling a plurality of bulk amorphous metal magnetic components to form an inductive device having a magnetic core. The method comprises the following steps: (i) surrounding at least one component with an electrical winding; (ii) placing the components in a juxtaposed relationship to form a core having at least one magnetic circuit and wherein the layers of each component lie in substantially parallel planes; and (iii) securing the components in juxtaposed relation.

The arrangement of the components assembled in the device of the invention is secured by any suitable fastening means. The fastening means preferably does not provide the constituent parts with high stress that may lead to deterioration of magnetic properties such as magnetic permeability and core loss. The components are preferably bonded by a circumferential band, tape, or plate made of metal, polymer, or fabric. In another embodiment of the invention, the fastening means comprises a relatively rigid housing or frame, preferably made of a plastic or polymer material, having one or more cavities into which the constituent components are fitted. Suitable materials for the housing include nylon and glass-filled nylon. More preferred materials include polyethylene terephthalate and polybutylene terephthalate, which are commercially available from dupont under the trade designation Rynite PET thermoplastic polyester. The shape and placement of the cavities ensures that the components are in the desired alignment. In another embodiment, the fastening means comprises a rigid or semi-rigid outer dielectric coating or potting. The component parts are set in the desired alignment. A coating or potting is then applied to at least a portion of the outer surface of the device and appropriately activated and cured to secure the components. In some embodiments, one or more windings are applied prior to application of the coating or potting. Various coatings and methods are suitable, including epoxies. The finishing operation may include removing any excess coating, if desired. The outer coating advantageously protects the insulation of the electrical windings on the component from wear at sharp metal edges and serves to capture debris or other material that may tend to fall off the component or otherwise be improperly contained in the device or other nearby structure.

The manufacture of the component optionally further comprises the step of preparing a mating surface on the component, the mating surface being substantially planar and perpendicular to the constituent layers. Preparing the face may include a flattening operation to finish the mating face and remove any roughness or non-planarity, if desired. The planarization preferably includes at least one of milling, surface grinding, cutting, polishing, chemical etching and electrochemical etching or similar operations to provide planar mating surfaces. The flattening step is particularly preferred for mating surfaces located at the sides of the component to correct for the effects of any non-ideal alignment of the amorphous metal layer.

Various fastening techniques may be implemented in combination to provide additional strength against externally imposed mechanical and magnetic forces that accompany excitation of the component in operation.

Cutting the bulk amorphous metal magnetic component of the present invention from a laminated rod 50 of amorphous metal strip or a wound core 70 of amorphous metal strip may be accomplished using a number of cutting techniques. Suitable methods include, but are not limited to, the use of abrasive cutting blades or wheels, mechanical grinding, diamond wire cutting, high speed milling in a horizontal or vertical direction, abrasive waterjet milling, electrical discharge machining by wire or immersion, electrochemical grinding, electrochemical machining, and laser cutting. The cutting process preferably does not produce any appreciable damage at or near the cutting surface. Such damage may result, for example, from excessive cutting speeds that locally heat the amorphous metal beyond its crystallization temperature or even melt the material at or near the edges. Adverse results may include increased stress and core loss near the edges, interlayer shortening, or degradation of mechanical properties. A member having a relatively simple shape without an internal apex, such as a rectangular prism shape or a trapezoidal member, is preferably cut from the bar 50 or the iron core 70 by using a cutting blade or wheel. Other shapes having internal vertices, such as C-parts and E-parts, are easier to cut from the rod 50 or core 70 by techniques such as mechanical grinding, diamond wire cutting, high speed milling in a horizontal or vertical direction, abrasive water jet milling, electrical discharge machining by wire or immersion, electrochemical grinding, electrochemical machining, and laser cutting.

Inductive devices including bulk amorphous metal magnetic components constructed in accordance with the present invention are particularly well suited as inductors and transformers for a variety of electronic circuit devices including, notably, power conditioning circuit devices such as power sources, voltage converters, and similar power conditioning devices operating at frequencies of 1kHz or higher using switch-mode technology. The low losses of the present inductive device advantageously improve the efficiency of such electronic circuit device. The manufacture of the magnetic component is simplified and the manufacturing time is reduced. Other stresses encountered during construction of the bulk amorphous metal component are minimized. Magnetic properties of the finished device are optimized.

The bulk amorphous used in the practice of the present invention can be made using a number of amorphous metal alloysA bulk metal magnetic component. Generally, alloys suitable for use in constructing the components of the present invention are of the formula M_70-85Y_5-20Z_0-20Defining, the subscripts are atomic percentages, wherein "M" is at least one of Fe, Ni, and Co, "Y" is at least one of B, C and P, and "Z" is at least one of Si, Al, and Ge; with the proviso that (i) up to ten (10) atomic percent of the component "M" can be replaced by at least one of the metallic species Ti, V, Cr, Mn, Cu, Zr, Nb, Mo, Ta, and W, and (ii) up to ten (10) atomic percent of the component (Y + Z) can be replaced by at least one of the non-metallic species In, Sn, Sb, and Pb. As used herein, the term "amorphous metal alloy" means a metal alloy that substantially lacks any long-range order and is characterized by X-ray diffraction intensity maxima that are similar to those observed from liquid or inorganic oxide glasses.

Amorphous metal alloys suitable as starting materials in the practice of the present invention are generally commercially available in the form of continuous thin strips or ribbons of width up to 20cm or more and thicknesses of about 20-25 μm. These alloys are formed to have a substantially fully glassy microstructure (e.g., at least 80 volume percent of the material has an amorphous structure). The alloy is preferably formed to be substantially 100% of material having an amorphous structure. The volume fraction of the amorphous structure can be determined by methods known in the art, such as X-ray, neutron or electron diffraction, transmission electron microscopy or differential scanning calorimetry. The highest induction values are achieved for the alloy at low cost, where "M", "Y" and "Z" are at least predominantly iron, boron and silicon, respectively. Accordingly, alloys comprising at least 70 atomic percent Fe, at least 5 atomic percent B, and at least 5 atomic percent Si, with the proviso that the total content of B and Si is at least 15 atomic percent, are preferred. Amorphous metal strip comprising iron-boron-silicon is also preferred. Most preferred is amorphous metal strip having a composition consisting essentially of about 11 atomic percent boron and about 9 atomic percent silicon, the balance being iron and incidental impurities. This saturation induction with about 1.56TTapes of strength and resistivity of about 137 μ Ω -cm are sold by honeywell international incAlloy 2605 SA-1. Another suitable amorphous metal strip has a composition consisting essentially of about 13.5 atomic percent boron, about 4.5 atomic percent silicon, and about 2 atomic percent carbon, the balance being iron and incidental impurities. Such a tape having a saturation induction of about 1.59T and a resistivity of about 137 μ Ω -cm is sold by Honeywell International Inc., under the trade name ofAlloy 2605 SC. For applications requiring even higher saturation induction, a band having a composition consisting essentially of iron, along with about 18 atomic percent Co, about 16 atomic percent boron, and about 1 atomic percent silicon, the balance being iron and incidental impurities is suitable. Such a tape is sold by Honeywell International Inc. under the trade name HONEYWELL INTERNATIONAL INCAlloy 2605 CO. However, the losses of components constructed with this material tend to be slightly higher than those constructed with METGLAS 2605 SA-1.

As is known in the art, a ferromagnetic material may be characterized by its saturation induction or, equivalently, its saturation flux density or magnetization. The alloys suitable for use in the present invention preferably have a saturation induction of at least about 1.2 tesla (T) and more preferably have a saturation induction of at least about 1.5T. The alloy also has a high electrical resistivity, preferably at least about 100 μ Ω -cm and most preferably at least about 130 μ Ω -cm.

The mechanical and magnetic properties of amorphous metal strip designated for use in components may be enhanced by heat treatment at a temperature and for a time sufficient to provide the desired enhancement without altering the substantially fully glassy microstructure of the strip. Typically, the temperature is selected to be about 100-. The heat treatment includes a heating section, a selective soaking section, and a cooling section. The magnetic field may be selectively applied to the strip during at least a portion of the heat treatment, such as at least the cooling portion. The application of said field, preferably directed substantially in the direction in which the magnetic flux is located during operation of the component, may in some cases further improve the magnetic properties and reduce the core losses of the component. The heat treatment optionally comprises more than one such thermal cycle. Furthermore, the one or more heat treatment cycles may be performed at different stages of the component fabrication. For example, the discontinuous laminate structure may be treated or the stack of laminate structures may be heat treated before or after adhesive bonding. Since many other attractive adhesives do not withstand the required heat treatment temperatures, it is preferred to perform the heat treatment prior to bonding.

The heat treatment of the amorphous metal may employ any heating means that causes the metal to experience the desired thermal profile. Suitable heating means include infrared heat sources, ovens, fluidized beds, thermal contact with a heat sink maintained at an elevated temperature, resistive heating by passing an electric current through the belt, and inductive (radio frequency (RF)) heating. The choice of heating means may depend on the order of the desired process steps listed above.

The magnetic properties of certain amorphous alloys suitable for use in the present component may be significantly improved by heat treating the alloy to form a nanocrystalline microstructure. The microstructure is characterized by the presence of a high density of grains having an average size of less than about 100nm, preferably less than 50nm, and more preferably from about 10 to 20 nm. The grains preferably comprise at least 50% by volume of the iron-based alloy. These preferred materials have low core loss and low magnetostriction. The latter property also makes the material less susceptible to degradation of magnetic properties caused by stresses resulting from the manufacture and/or operation of the device comprising the component. The heat treatment required to produce a nanocrystalline structure in a given alloy must be carried out at a higher temperature or for a longer period of time than is required for a heat treatment designed to maintain a substantially fully glassy microstructure therein. As used herein, the terms amorphous metal and amorphous alloy also include materials that are initially formed to have a substantially complete glassy microstructure and subsequently transformed by heat treatment or other processes to a material having a nanocrystalline microstructure. Amorphous alloys that can be heat treated to form a nanocrystalline microstructure may also be referred to generally simply as nanocrystalline alloys. The present method allows the nanocrystalline alloy to be formed into the geometry required for the finished bulk magnetic component. The nanocrystalline structure generally makes it more brittle and more difficult to handle before the alloy is heat treated to form the nanocrystalline structure, which formation is advantageously achieved when the alloy is still in an as-cast, ductile, substantially amorphous form. Typically, the nanocrystalline heat treatment is carried out at a temperature in the range of from about 50 ℃ below the crystallization temperature of the alloy to about 50 ℃ above it.

Two preferred grades of alloys with significantly enhanced magnetic properties by forming nanocrystalline microstructures in the alloy are given by the following formula, where the subscripts are atomic percent.

The first preferred grade of nanocrystalline alloy is Fe_{100-u-x-y-z-w}R_uT_xQ_yB_zSi_wWherein R is at least one of Ni and Co, T is at least one of Ti, Zr, Hf, V, Nb, Ta, Mo, and W, Q is at least one of Cu, Ag, Au, Pd, and Pt, u is in the range from 0 to about 10, x is in the range from about 3 to about 12, y is in the range from 0 to about 4, z is in the range from about 5 to about 12, and W is in the range from 0 to less than about 8. After heat treating such an alloy to form a nanocrystalline microstructure therein, it has a high saturation induction (e.g., at least about 1.5T), low core loss, and low saturation magnetostriction (e.g., having an absolute value of less than 4 x 10)^-6Magnetostriction of (1). Such alloys are particularly preferred for applications where devices with minimal dimensions are required.

The second preferred grade of nanocrystalline alloy is Fe_{100-u-x-y-z-w}R_uT_xQ_yB_zSi_wWherein R is at least one of Ni and Co, T is at least one of Ti, Zr, Hf, V, Nb, Ta, Mo, and W, Q is at least one of Cu, Ag, Au, Pd, and Pt, u is in the range from 0 to about 10, x is in the range from about 1 to 5, y is in the range from 0 to about 3, z is in the range from about 5 to 12, and W is in the range from about 8 to 18. After heat treating such alloys to form nanocrystalline microstructures therein, they have a saturation induction of at least about 1.0T, particularly low core loss, and low saturation magnetostriction (e.g., having absolute values less than 4 x 10^-6Magnetostriction of (1). Such alloys are particularly preferred for use in devices requiring operation at particular excitation frequencies, for example 1000Hz or higher.

A bulk amorphous magnetic component will magnetize and demagnetize more efficiently than components made from other iron-based magnetic metals. When incorporated into an inductive device, the bulk amorphous metal component will generate less heat when both components are magnetized at the same magnetic induction and frequency as compared to a comparable component made of another iron-based magnetic metal. Inductive devices using bulk amorphous metal components may therefore be designed to (i) operate at lower operating temperatures; (ii) operating at higher magnetic induction to achieve reduced size and weight and increased energy storage or transfer; or (iii) operate at higher frequencies to achieve reduced size and weight when compared to inductive devices comprising components made from other iron-based magnetic metals.

As is known in the art, core loss is the dissipation of energy that occurs within a ferromagnetic material as the magnetization of the ferromagnetic material changes over time. The core loss of a given magnetic component is typically determined by cyclic excitation of the component. A time-varying magnetic field is applied to the component to produce a corresponding time-varying change in magnetic induction or flux density therein. For normalization of the measurement, excitation is usually chosenSo that the magnetic induction is uniform in the sample and varies sinusoidally with time at a frequency "f" and has a peak amplitude B_max. The core loss is then determined by known electrical measurement instrumentation and techniques. Losses are conventionally reported as watts per unit mass or volume of the magnetic material being excited. Losses are known in the art as f and B_maxMonotonically increasing. The most standard protocol for detecting core loss of soft magnetic materials used in inductive devices { e.g., ASTM standards a912-93 and a927(a927M-94) } requires a sample of such material located within a substantially closed magnetic circuit, i.e., a configuration in which closed magnetic flux lines are substantially contained within the sample volume and the cross-section of the magnetic material is substantially the same throughout the magnetic circuit. On the other hand, the presence of a high reluctance gap through which magnetic flux lines must traverse can cause the magnetic circuit in an actual inductive device, particularly a flyback transformer or an energy storage inductor, to be relatively open. Due to fringing field effects and field inhomogeneity, a given material tested in an open circuit typically exhibits a higher core loss, i.e., a higher value of watts per unit mass or volume, than it has in a closed circuit measurement. The bulk magnetic component of the present invention advantageously exhibits low core losses over a wide range of flux densities and frequencies, even in a relatively open circuit configuration.

The total core loss of the low loss bulk amorphous metal device of the present invention is believed to include contributions from hysteresis losses and eddy current losses without being bound by any theory. Each of these two contributions is a peak magnetic induction B_maxAnd excitation frequency f. Prior art analysis of core loss in amorphous metals (see, e.g., g.e.fish, j.appl.phys.573569(1985) and G.E.Fish et al, J.appl.Phys.645370(1988)) have generally been limited to data obtained from materials in closed magnetic circuits.

Total core loss per unit mass L (B) for the device of the invention_maxAnd f) analysis of the magnetic flux in a cross-sectional plane having a single magnetic path and substantially the same effective magnetic materialThe configuration of the product is the simplest. In that case, the loss may be generally defined by a function having the form:

L(B_max，f)＝c₁f(B_max)ⁿ+c₂f^q(Bmax)^m

wherein the coefficient c₁And c₂And the indices n, m and q must all be determined empirically without known theory that accurately determines their values. Using this formula allows the total core loss of the device of the invention to be determined at any desired operating magnetic induction and excitation frequency. It is sometimes found that in a specific geometry of the induction device the magnetic field therein is spatially inhomogeneous, especially in embodiments with multiple magnetic paths and material cross-sections, such as are commonly used in three-phase devices. Techniques such as finite element modeling are known in the art to provide an estimate of the spatial and temporal variation of the peak flux density that closely approximates the flux density distribution measured in an actual device. Using as input appropriate empirical formulas that give the core loss of a given material at a spatially uniform flux density, these techniques allow the corresponding actual core loss of a given component in its operating configuration to be predicted with reasonable accuracy by numerical integration throughout the volume of the device.

The measurement of the core loss of the magnetic device of the present invention can be accomplished using various methods known in the art. The determination of the losses is particularly simple in the case of a device with a single magnetic circuit and a substantially constant cross section. Suitable methods include providing a device having primary and secondary electrical windings, each electrical winding surrounding one or more components of the device. Magnetomotive force is applied by passing a current through the primary winding. The resulting magnetic flux density is determined from the voltage induced in the secondary winding by faraday's law. The applied magnetic field is determined from the magnetomotive force by ampere's law. The core loss is then calculated from the applied magnetic field and the resulting magnetic flux density using conventional methods.

The following examples are presented to provide a more complete understanding of the invention. The specific techniques, conditions, materials, proportions and reported data set forth to illustrate the principles and practice of the invention are exemplary and should not be construed as limiting the scope of the invention.

Example 1

Preparation and electromagnetic testing of amorphous metal rectangular prisms

Fe about 25mm wide and 0.022mm thick₈₀B₁₁Si₉Ferromagnetic amorphous metal strip is wound around a rectangular mandrel or bobbin having dimensions of about 25mm wide and 60mm long. About 1300 turns of ferromagnetic amorphous metal strip are wound around a mandrel or bobbin, producing a rectangular core form having internal dimensions of about 25mm wide and 60mm long and about 30mm build thickness. The core/bobbin assembly was annealed in a nitrogen atmosphere. The annealing comprises the following steps: 1) heating the assembly to 365 ℃; 2) maintaining the temperature at about 365 ℃ for about 2 hours; and 3) cooling the assembly to ambient temperature. A rectangular, wound, amorphous metal core is removed from the core/bobbin assembly and then immersed in a low viscosity thermally active epoxy such that the epoxy impregnates and penetrates the spaces between adjacent laminations. The epoxy used is Epoxylite^TM8899, the epoxy is diluted to a volume ratio of 1: 5 by acetone to achieve the appropriate viscosity. The bobbin was replaced and the reconstructed impregnated core/bobbin assembly was then exposed to a temperature of about 177 ℃ for about 2.5 hours to activate and cure the epoxy resin solution. When fully cured, the core is again removed from the core/bobbin assembly. The resulting rectangular, wound, epoxy bonded, amorphous metal core weighed approximately 1500 g.

A rectangular prism 30 of 30mm long, 25mm wide and 30mm thick (about 1300 layers) was cut from the approximate center of each long side of the epoxy-bonded amorphous metal core using a 1.5mm thick cutting blade. The cut surfaces of the rectangular prism and the remainder of the core were etched in a nitric acid/water solution and washed in an ammonium hydroxide/water solution. The rectangular prism and the remainder of the core are then reassembled into the form of a complete cut core, with the ribbon layers in the prism in their initial orientation. The primary and secondary electrical windings are secured to the remainder of the core. The cut core structures were electrically tested at 60Hz, 1,000Hz, 5,000Hz and 2,0000Hz and compared to the catalog values for other ferromagnetic materials in a similar test setup (National-Arnold Magnetics, 17030 Muskrat Avenue, Adelanto, CA92301 (1995)). The results are compiled in tables 1, 2, 3 and 4 below.

TABLE 1 core loss at 60Hz (W/kg)

TABLE 2 core loss at 1,000Hz (W/kg)

1.0T	11.51	24	20	31	46
						1.1T	13.46
1.2T	15.77	33	28
						1.3T	17.53
1.4T	19.67	44	35

TABLE 3 core loss at 5,000Hz (W/kg)

TABLE 4 core loss at 20,000Hz (W/kg)

As shown by the data in tables 3 and 4, the core loss at the excitation frequency of 5000Hz or higher is particularly low. The magnetic component of the present invention is therefore particularly suitable for constructing the induction device of the present invention.

Example 2

High frequency behavior of low loss bulk amorphous metal components

The core loss data included in example 1 above was analyzed using conventional non-linear regression methods. Is determined by Fe₈₀B₁₁Si₉The core loss of a bulk amorphous component composed of amorphous metal strips may be defined primarily by a function having the form

L(B_max，f)＝c₁f(B_max)ⁿ+c₂f^q(Bmax)^m

Coefficient c₁And c₂And appropriate values of the indices n, m and q are selected to define an upper limit for the magnetic loss of the bulk amorphous metal component. Table 5 lists the measured losses of the components in example 1 and the losses predicted by the above formula, each measured in watts per kilogram. Using coefficient c₁0.0074 and c₂Calculated as f (hz) and B (q) are 0.000282, 1.3 for the index n, 2.4 for m and 1.5 for q_maxPredicted loss of function of (Tesla). The measured loss of the bulk amorphous metal component of example 1 is less than the corresponding loss predicted by the formula.

TABLE 5

Dot	BTesla (Tesla)	Frequency (Hz)	Measuring core loss (W/kg)	Predicting core loss (W/kg)
					1	0.3	60	0.1	0.10
2	0.7	60	0.33	0.33
					3	1.1	60	0.59	0.67
4	1.3	60	0.75	0.87

Dot	BTesla (Tesla)	Frequency (Hz)	Measuring core loss (W/kg)	Predicting core loss (W/kg)
					5	1.4	60	0.85	0.98
6	0.3	1000	1.92	2.04
					7	0.5	1000	4.27	4.69
8	0.7	1000	6.94	8.44
					9	0.9	1000	9.92	13.38
10	1	1000	11.51	16.32
					11	1.1	1000	13.46	19.59
12	1.2	1000	15.77	23.19
					13	1.3	1000	17.53	27.15
14	1.4	1000	19.67	31.46
					Dot	BTesla (Tesla)	Frequency (Hz)	Measuring core loss (W/kg)	Predicting core loss (W/kg)
15	0.04	5000	0.25	0.61
					16	0.06	5000	0.52	1.07
17	0.08	5000	0.88	1.62
					18	0.1	5000	1.35	2.25
19	0.2	5000	5	6.66
					20	0.3	5000	10	13.28
21	0.04	20000	1.8	2.61

Dot	BTesla (Tesla)	Frequency (Hz)	Measuring core loss (W/kg)	Predicting core loss (W/kg)
					22	0.06	20000	3.7	4.75
23	0.08	20000	6.1	7.41
					24	0.1	20000	9.2	10.59
25	0.2	20000	35	35.02
					26	0.3	20000	70	75.29

Example 3

Preparation of amorphous metal trapezoidal prism and inductor

Fe about 25mm wide and 0.022mm thick₈₀B₁₁Si₉The ferromagnetic amorphous metal strip is cut to a length of about 300 mm. About 1300 layers of cut ferromagnetic amorphous metal strips were laminated to form rods about 25mm wide and 300mm long with a construction thickness of about 30 mm. The rods were annealed in a nitrogen atmosphere. The annealing comprises the following steps: 1) heating the rod to 365 ℃; 2) maintaining the temperature at about 365 ℃ for about 2 hours; and 3) cooling the rod to ambient temperature. The rods were vacuum impregnated with an epoxy resin solution and cured at 120 ℃ for about 4.5 hours. The weight of the resulting laminated, epoxy bonded, amorphous metal rod was about 1300 g.

The bar was cut with a 1.5mm thick cutting blade to form four substantially identical trapezoidal prism sections. The cuts were made with a 1.5mm thick cutting blade at a cross-mitered angle of ± 45 ° to the long axis of the ribbon comprising the initially laminated amorphous metal rod, thereby forming mating faces at each end of each prism. The mating faces are perpendicular to the plane of the ribbon layers in each prism and are about 35mm wide and 30mm thick, corresponding to 1300 layers of ribbon. The unequal sides of each prism are parallel and about 100mm and 150mm long, respectively. The cut surfaces of each trapezoidal prism were etched in a nitric acid/water solution and washed in an ammonium hydroxide/water solution.

An electrical winding is wound on each of four prisms which are then assembled to form a transformer having a square picture frame configuration with a square window. The respective windings on the opposing sections are additively connected in series to form primary and secondary windings.

The core loss of the transformer was tested by driving the primary winding with an alternating current source and detecting the voltage induced in the secondary winding. The core loss of the transformer was determined using a yokogawa model 2532 conventional electron voltmeter connected to the first and secondary windings. Core losses of less than about 12W/kg are observed for cores excited at peak flux magnitudes of 5000Hz to 0.3T.

Example 4

Preparation of nanocrystalline alloy rectangular prism

Using a width of about 25mm and a thickness of 0.018mm and having Fe_73.5Cu₁Nb₃B₉Si_13.5Amorphous metal strips of nominal composition (a) produced rectangular prisms. About 1600 strips of 300mm long tape were cut and stacked in an alignment in the fixture. The stack is heat treated to form a nanocrystalline microstructure in the amorphous metal. Annealing is carried out by performing the following steps: 1) heating the portion to 580 ℃; 2) maintaining the temperature at about 580 ℃ for about 1 hour; and 3) cooling the portion to ambient temperature. After the heat treatment, the stack is impregnated by dipping into a low viscosity epoxy resin. The resin was activated and cured at a temperature of about 177 ℃ for about 2.5 hours to form epoxy impregnated rectangular rods.

Four identical rectangular prisms of 100mm length and having end faces of 25mm width and 30mm height were formed by cutting a rectangular bar with an abrasive saw. The cut ends of two of the prisms were etched in a nitric acid/water solution and cleaned in an ammonium hydroxide/water solution to form mating faces. Mating surfaces are also prepared on the side of each of the remaining two bars. Each face area is lightly lapped to form a flat surface having the desired dimensions. The surface area is subsequently etched in a nitric acid/water solution and cleaned in an ammonium hydroxide/water solution.

The four prisms are then assembled and fastened to form an inductive device having a rectangular picture frame configuration. A primary electrical winding is applied around one of the prisms and a secondary winding is applied to the opposite prism. The windings are connected to a standard electronic wattmeter. The core loss of the device is then tested by passing a current through the primary winding and detecting the induced voltage in the secondary winding. The core loss was determined using a Yokogawa 2532 watt meter.

The nanocrystalline alloy inductive device has a core loss of less than about 12W/Kg at 5000Hz and 0.3T, which makes it suitable for use in high efficiency inductors or transformers.

Having thus described the invention in rather full detail, it is to be understood that such detail need not be strictly adhered to but that various changes and modifications may suggest themselves to one skilled in the art, all falling within the scope of the invention as defined by the subjoined claims.

Claims (41)

1. An inductive device, comprising:

a. a magnetic core comprising a plurality of low-loss bulk ferromagnetic amorphous metal magnetic components assembled in juxtaposed relation as an assembly and forming at least one magnetic circuit;

b. fastening means for fastening said components in said relationship;

c. at least one electrical winding surrounding at least a portion of the magnetic core;

d. each of said components comprising a plurality of planar layers of ferromagnetic amorphous metal strip of substantially similar shape, said layers being joined together by an adhesive to form a polyhedron-shaped section having a thickness and a plurality of mating faces, the thickness of each of said components being substantially equal;

e. the components being arranged in the assembly with the layers of the tape of each component in generally parallel planes and each mating face proximate a mating face of another of the components to form proximate mating faces; and

f. when the induction device reaches the peak value magnetic induction intensity B of 0.3T under the excitation frequency f of 5000Hz_max"has a core loss of less than 12W/Kg.

2. The inductive device of claim 1, said device being a member selected from the group consisting of a transformer, a saturable reactor, and an energy storage inductor.

3. An inductive device as recited by claim 1, said device being an autotransformer.

4. An inductive device as recited by claim 1, including a plurality of electrical windings.

5. The inductive device of claim 1, wherein each of said members has a shape selected from the group consisting of C, E, I, U and trapezoidal.

6. The inductive device of claim 1, wherein at least one of the components has a rectangular prism shape.

7. An inductive device as recited by claim 6, wherein each of said members has a rectangular prism shape.

8. An inductive device as recited by claim 1, wherein at least some of said proximate mating surfaces are mitered.

9. The inductive device of claim 1, having a shape selected from the group consisting of E-I, E-E, C-I, C-C and C-I-C shapes.

10. The inductive device of claim 1, wherein the fastening device comprises a strap comprising at least one of a metal, a polymer.

11. The inductive device of claim 1, wherein the fastening device comprises a strap comprising at least one of metal, fabric.

12. The inductive device of claim 1, wherein the fastening means comprises a strap comprising at least one of metal, pressure sensitive tape.

13. An inductive device as recited by claim 1, wherein said fastening means includes a housing.

14. The inductive device of claim 1, wherein the fastening device comprises potting the magnetic core.

15. An inductive device as recited by claim 1, wherein said electrical winding is disposed on a bobbin that is mounted on a portion of at least one of said components.

16. The inductive device of claim 1, wherein each of the mating faces has a planar mating surface.

17. An inductive device as recited by claim 1, wherein said plurality of low-loss bulk ferromagnetic amorphous metal magnetic components are assembled to form a substantially closed magnetic circuit.

18. An inductive device as recited by claim 1, wherein said plurality of low-loss bulk ferromagnetic amorphous metal magnetic components are assembled by interposing an air gap between said mating faces.

19. An inductive device as recited by claim 18, further comprising spacers in said air gap.

20. An inductive device as recited by claim 1, including a plurality of magnetic circuits.

21. An inductive device as claimed in claim 2 or 3, said device being a single phase device.

22. An inductive device as claimed in claim 2 or 3, said device being a multiphase device.

23. An inductive device as recited by claim 1, wherein said amorphous metal is annealed.

24. An inductive device as recited by claim 1, said device having a core loss less than "L", where L is given by the formula L-0.0074 f (B)_max)^1.3+0.000282f^1.5(B_max)^2.4The measurement units of the iron core loss, the excitation frequency and the peak magnetic induction intensity are respectively given as watt/kilogram, hertz and tesla.

25. An inductive device as recited by claim 1, wherein each said ferromagnetic amorphous metal strip has a composition consisting essentially of the formula M_70-85Y_5-20Z_0-20Defined composition, subscripts are atomic percent, wherein "M" is at least one of Fe, Ni and Co, and "Y" is B, C and PAt least one, and "Z" is at least one of Si, Al, and Ge; with the proviso that (i) up to 10 atomic percent of component "M" is selectively replaced by at least one of the metallic species Ti, V, Cr, Mn, Cu, Zr, Nb, Mo, Ta, Hf, Ag, Au, Pd, Pt, and W, (ii) up to 10 atomic percent of component (Y + Z) is selectively replaced by at least one of the non-metallic species In, Sn, Sb, and Pb, and (iii) up to about one atomic percent of component (M + Y + Z) is an incidental impurity.

26. An inductive device as recited by claim 25, wherein each of said ferromagnetic amorphous metal strips has a composition including at least 70 atomic percent Fe, at least 5 atomic percent B, and at least 5 atomic percent Si, with the proviso that the total content of B and Si is at least 15 atomic percent.

27. An inductive device as recited by claim 26, wherein each said ferromagnetic amorphous metal strip has the formula Fe₈₀B₁₁Si₉The defined composition.

28. An inductive device as recited by claim 1, wherein at least a portion of a surface of said magnetic core is coated with an insulating coating.

29. An inductive device as recited by claim 28, wherein said coating covers substantially the entire surface of said magnetic core.

30. A method of constructing an inductive device having a magnetic core comprising a plurality of bulk ferromagnetic amorphous metal magnetic components, each of said components having a plurality of layers of amorphous metal strip bonded together by an adhesive to form a generally polyhedral segment having a thickness and a plurality of mating faces, said method comprising the steps of:

a. surrounding at least one of said magnetic components with an electrical winding;

b. placing the segments in juxtaposed relation to form the magnetic core having at least one magnetic circuit, the layers of each segment lying in generally parallel planes; and

c. securing said components in said juxtaposed relationship.

31. A method as claimed in claim 30 further comprising the step of inserting a spacer into at least one air gap separating said plurality of bulk ferromagnetic amorphous metal magnetic components.

32. The method of claim 30, wherein the step of securing includes bonding the components using an adhesive.

33. The method of claim 30, wherein the step of securing includes bonding the components with straps.

34. The method of claim 30, wherein the securing step comprises seating the component within a housing.

35. The method of claim 30, further comprising the step of preparing a mating surface on the component.

36. The method of claim 35, wherein the step of preparing the mating surfaces comprises a leveling operation comprising at least one of milling, surface grinding, cutting, polishing, chemical etching, and electrochemical etching.

37. The method of claim 30, wherein the electrical winding is wound on a bobbin having a hollow interior and the bobbin is seated on a portion of the magnetic core.

38. An electronic circuit device having at least one low-loss inductive device selected from the group consisting of a transformer, a saturable reactor, and an energy storage inductor, the device comprising:

a. a magnetic core comprising a plurality of low-loss bulk ferromagnetic amorphous metal magnetic components assembled in juxtaposed relation and forming at least one magnetic circuit, each of said components comprising a plurality of planar layers of substantially similarly shaped amorphous metal strip bonded together by an adhesive to form a polyhedron-shaped section having a thickness and a plurality of mating faces, the thickness of each of said components being substantially equal;

b. fastening means for fastening said components in said relationship wherein said components are arranged with said layers of said tape of each said component in substantially parallel planes and each said mating face proximate a mating face of another said component to form proximate mating faces; and

c. at least one electrical winding surrounding at least a portion of the magnetic core.

39. The electronic circuit device according to claim 38, wherein the low-loss inductive device is an autotransformer.

40. The electronic circuit device of claim 38 or 39, wherein when the induction device reaches a peak magnetic induction magnitude "B" of 0.3T at an excitation frequency "f" of 5000Hz_max"has a core loss of less than 12W/Kg.

41. A power conditioning circuit arrangement selected from the group consisting of a switch mode power source and a switch mode voltage converter, the arrangement comprising:

a. a magnetic core comprising a plurality of low-loss bulk ferromagnetic amorphous metal magnetic components assembled in juxtaposed relation and forming at least one magnetic circuit, each of said components comprising a plurality of planar layers of substantially similarly shaped amorphous metal strip bonded together by an adhesive to form a polyhedron-shaped section having a thickness and a plurality of mating faces, the thickness of each of said components being substantially equal;

b. fastening means for fastening said components in said relationship wherein said components are arranged with said layers of said tape of each said component in substantially parallel planes and each said mating face proximate a mating face of another said component to form proximate mating faces; and

c. at least one electrical winding surrounding at least a portion of the magnetic core.