MXPA06003865A - Efficient axial airgap electric machine having a frontiron - Google Patents

Abstract

A rotating, dynamoelectric machine, such as an electric motor, a generator, or a regenerative motor, comprises a stator assembly that includes a backiron section, a plurality of stator tooth sections, and a frontiron. The dynamoelectric machine has an axial airgap-type configuration. In addition, the electric machine has a high pole count that operates at high commutating frequencies, with high efficiency, high power density and reduced heating in the rotor. Low-loss materials employed in the dynamoelectric machine include amorphous metals, nanocrystalline metals, optimized Fe-based alloys, and optimized grain-oriented Fe-based materials or non-grain-oriented Fe-based materials.

Description

ELECTRICAL MACHINE OF EFFICIENT AXIAL ENTREHIERRO THAT HAS A FRONTAL IRON FIELD OF THE INVENTION The invention relates to a rotating machine dina oelectrica; and more particularly, to a dynamoelectric, axial air gap rotating machine, comprising a rotor assembly and a stator assembly including a front iron section, a rear iron section, and a plurality of stator tooth sections. BACKGROUND OF THE INVENTION The electric motors industry and generators are continually seeking ways to provide dynamo-electric rotating machines with increased energy densities and efficiencies. As used herein, the term "engine" refers to all classes of motor machines and generators that convert electrical energy to rotational movement and vice versa. Such machines include devices that can alternatively operate as motors, generators-and regenerative motors. The term "regenerative motor" is used herein to refer to a device that can be operated either as an electric motor or as a generator. A wide variety of engines are known, including REF.:172206 types of permanent magnet, field winding, induction, variable reluctance, interrupted reluctance and brush and without brush. These can be energized directly from a source of direct or alternating current provided by a distribution network of electrical installation, batteries or other alternative form. Alternatively, these may be supplied by current having the required waveform that is synthesized using the electronic drive circuitry. The rotational energy derived from any mechanical source can drive a generator. The output of the generator can be directly connected to a load or conditioned using the set of electronic energy circuits. Optionally, a given machine is connected to a mechanical source that functions either as a source or mechanical energy dissipator during different periods in its operation. The machine can act in this way, as a regenerative engine, for example, by connecting through the set of power conditioning circuits capable of performing the operation in four quadrants. Rotating machines ordinarily include a stationary component known as a stator and a rotating component known as a rotor. The adjacent faces of the rotor and the stator are separated by a small air gap crossed by magnetic flux that connects the rotor and the stator. It may be understood by those of ordinary skill in the art that a rotating machine may comprise multiple mechanically connected rotors and multiple stators. Virtually all rotary machines are conventionally classifiable either as radial or axial air type. A type of radial air gap is one in which the rotor and the stator are radially separated and the traveling magnetic flux is predominantly directed perpendicular to the axis of rotation of the rotor. In an axial gap device, the axially spaced rotor and stator, and the flow crossing is predominantly parallel to the rotational axis. Except for certain specialized types, motors and generators generally employ soft magnetic materials of one or more types. By "magnetic material" is meant one that is easily and efficiently magnetized and demagnetized. The energy that is inevitably dissipated in a magnetic material during each magnetization cycle is called hysteresis loss or core loss. The magnitude of the hysteresis loss is a function of the excitation amplitude and the frequency. A soft magnetic material also shows high permeability and low magnetic coercivity. Motors and generators also include a magnetomotive force source, which can be provided either by one or more permanent magnets or by additional soft magnetic material, circularly surrounded by windings carrying current. By "permanent magnet material" also called "hard magnetic material" is meant a magnetic material that has a high magnetic co-sensitivity and strongly retains its magnetization and resists being demagnetized. Depending on the type of motor, permanent and soft magnetic materials can be placed either on the rotor or the stator. By far, the preponderance of currently produced engines uses as a soft magnetic material various grades of electric or motor steels, which are iron alloys with one or more alloying elements including especially silicon, phosphorus, carbon, and aluminum. More commonly, silicon is a predominant alloying element. While it is generally believed that motors and generators that have rotors built with advanced permanent magnetic material and stators that have cores made with smooth, low loss, advanced materials, such as amorphous metal, have the potential to provide substantially superior efficiency and Higher energy densities compared to conventional radial air gap motors and generators, there has been little success in the construction of such machines either of axial or radial air gap type. Previous attempts to incorporate amorphous material in conventional radial or axial air gap machines have been largely unsuccessful commercially. The first designs involved mainly the replacement of the stator and / or the rotor with windings and circular amorphous metal laminations, typically cut with teeth through the internal or external surface. Amorphous metal has unique magnetic and mechanical properties that make it difficult or impossible to directly replace ordinary steels in conventionally designed engines. A number of applications in current technology, including widely diverse areas such as high-speed machine tools, aerospace motors and actuators, and compressor drives, require electric motors operable at high speeds (eg, at high rpm), many times higher from 15,000 to 20,000 rpm, and in some cases up to 100,000 rpm. High-speed electric machines are almost always manufactured with low dust counts, for fear that the magnetic materials in electric machines operating at higher frequencies will experience excessive core losses that contribute to inefficient motor design. This is mainly due to the fact that the soft material used in the vast majority of current engines is a silicon-iron alloy (Si-Fe). It is well known that from the losses resulting from the change of a magnetic field to frequencies greater than about 400 Hz in conventional materials based on Si-Fe causes the material to heat up, frequently to a point where the device can not be cooled by any means acceptable. To date, it has proven very difficult to provide easily manufactured electrical devices at low cost, which take advantage of low loss materials. Previous attempts to incorporate low loss materials into conventional machines in general have failed, as early designs typically relied merely on the replacement of new soft magnetic materials, such as amorphous metal, by conventional alloys, such as silicon-iron, in magnetic cores of machines. The resulting electrical machines have sometimes provided increased efficiencies with less loss, but generally suffer from an unacceptable reduction in energy output, and significant increases in cost, associated with the handling of amorphous metal formation. As a result, they have not achieved commercial success or market penetration. However, an additional problem that arises in electrical machines capable of operating at high frequencies and high speeds, is the heating in the rotor. As the rotor rotates relative to the stator, the rotor magnets experience cyclical differences in the permeance coefficient during the course of each rotation, since the rotor magnets alternately pass between the alignment with the teeth of the stator core and the centered positions in the empty spaces between the teeth of the stator. In turn, this variation in the permeance results in flow within the rotor, inducing eddy currents according to Faraday's law. Those currents in some cases are high enough to cause significant heating in the rotor. The heating in turn, is likely to cause irreversible loss of magnetization and decreased performance of the device. In extreme cases, the heating may even be severe enough to reduce the life time of the rotor magnets or destroy them. Accordingly, there remains a need in the art for highly efficient electrical devices, which take full advantage of the specific characteristics associated with the low loss material, thereby eliminating the disadvantages associated with conventional machines. Ideally, an improved machine could provide greater conversion efficiency between mechanical and electrical energy forms. Improved efficiency in generating machines energized by solid fuels could concomitantly reduce air pollution. The machine could be smaller, lighter and satisfy more demanding requirements of torque, power and speed. The cooling requirements could be reduced. Motors that operate from the battery power could operate for a longer time for a given charge cycle. For certain applications, axial air gap machines are best suited because of their size and shape and their particular mechanical attributes. Similar improvements in the properties of the machine are sought for axial and radial air gap devices. BRIEF DESCRIPTION OF THE INVENTION The present invention provides a dynamoelectric electric machine comprising a rotor assembly, and a stator assembly including a front iron section, a rear iron section, and a number of sections of stator teeth. The electrical device can have any dust count in the low to high range. Preferably, the stator comprises a generally toroidal structure employing laminated layers composed of at least one low loss core material selected from the group consisting of amorphous and nanocrystalline metals of optimized iron-based alloy. However, other soft magnetic materials may also be used in the construction of all or part of the stator assembly. The rotor assembly is supported for rotation about an axis and includes a plurality of powders. The assembly is arranged and positioned for magnetic interaction with the stator assembly. The use of advanced soft magnetic materials, low core loss, provides significant design flexibility, making possible a wide range of dust counts and switching frequencies, while also maintaining high operating efficiency, high density energy and a wide range of possible operating speeds. Examples of electrical machines that can be produced and operated in accordance with the invention include, but are not limited to, electric motors, generators and regenerative motors. One or more of the electrical devices could be a component in a composite device or system. An example of such a composite device is a compressor that includes one or more electric motors, where one or more electric motors can be integral with a fan. The invention further provides a method for constructing a dynamoelectric machine comprising: (i) the provision of at least one stator assembly comprising a rear iron section and a plurality of tooth sections, the stator assembly having a slot between each adjacent pair of tooth sections and stator windings wound through the slots; (ii) the provision of a frontal iron section; and (iii) the provision of at least one rotor assembly supported for rotation about an axis and including a plurality of poles, the motor assembly is accommodated and positioned for magnetic interaction with at least one stator assembly. A dynamo-electric machine system comprises a dynamo-electric machine of the aforementioned type and an electronic energy means for interconnecting and controlling the machine. The electronic means of energy are operably connected to the machine. BRIEF DESCRIPTION OF THE FIGURES The invention will be fully understood and the additional advantages will become apparent when reference is made to the following detailed description of the preferred embodiments of the invention and the accompanying drawings, wherein like reference numbers denote elements similar to all throughout the various views, and in which: Figure 1 illustrates a top view of a stator structure according to an aspect of the '094 application, which includes a number of sections of stator teeth, stator windings and a later iron; Figure 2 is a cross-sectional view describing a stator structure of the invention, employing a stator structure of the type described in Figure 1, and also including a front iron, the view being taken in II-II as it is shown in figure 1; Figure 3 is a partial exploded view describing a stator and rotor structure of one of the embodiments of the electric axial air gap device according to the present invention, showing the magnets of the rotor, the front iron, the windings of the stator, the stator cores and the rear iron, with the rotor carrier omitted for clarity; Figure 4 is a graph of the loss of the rotor versus the thickness of the front iron of an electrical device according to the invention under a load (D) or no load (0); Figure 5 is a graph of the operation versus the thickness of the frontal iron of an electrical device according to the invention; Figure 6 is a graph of the maximum flux density of the stator core, versus the thickness of the front iron of an electrical device according to the invention, under a load (?) Or no load (D); Figure 7 is a graph of the back electromotive force (0) and the constancy of the inductance (D) versus the thickness of the frontal iron of an electrical device according to the invention; Figure 8 is a graph of energy loss (?), the parasitic current loss (0) of the rotor, and the low waste dissipation density (D) versus the front iron thickness of a device according to the invention; Figure 9 is a graph of the energy factor (0) and efficiency (?) Versus the thickness of the frontal iron of an electrical device according to the invention; and Figure 10 is a graph of wear (v) versus front iron thickness, and ripple versus front iron thickness at current densities of 10.

A / mm2 (D), 20 A / mm2 (< >), and 30 A / mm2 (D), of an electrical device according to the invention. DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Preferred embodiments of the present invention will be explained in more detail hereafter, with reference to the accompanying drawings. In one aspect of the present invention, there is provided an electric machine including a rotor assembly and a stator assembly, having a front iron section, a rear iron and a plurality of stator tooth sections. As used herein, the term "front iron" means a structure composed of soft magnetic material and located adjacent to a surface of the stator having the tooth sections, and opposite the site of the front iron and close to the rotor. As will be described later in greater detail, the presence of a frontal iron in combination with the use of low core loss stators materials is preferred for the present invention. In preferred embodiments, the permanent magnet, brushless type machine, and the stators and rotors are in an axial air gap type configuration. The present machine may comprise one or more rotor assemblies and one or more stator assemblies. Accordingly, the terms "one rotor" and "one stator" as used herein with reference to electric machines, mean a number of rotor and stator assemblies in the range of one to as many as 1 as three or more. In the construction of axial air gap machines, a configuration having a single rotor between two front stators, beneficially reduces the axial thrust on the rotor, since the traction on the rotor from the respective stators is oppositely directed and substantially displaced. . General Device Structure The United States Provisional Application commonly assigned Serial No. 60 / 444,271 ("upon request? 271") and United States Patent Application Serial No. 10 / 769,094 ("the% 094 application. "), which are both incorporated by reference in their entirety herein, provide an electrical device having a rotor and stator assembly accommodated in an axial air gap configuration, but lacking a front iron. The stator includes a rear iron section and a plurality of sections of the stator tooth, preferably made using high frequency, low loss materials. Figure 1 illustrates a top view of a stator assembly 10 according to an aspect of the application 0 094, showing a unitary structure including sections of stator teeth 12 depending on the rear iron 16 and with windings 14 of stators wound around of the tooth sections 12. The front and tooth iron sections can be formed either as the unitary structure described, in which the tooth sections depend integrally on the posterior iron section, or as separate components, secured together by any appropriate means, such as an adhesive. The stator 10 and its windings 14 can be placed in a stator carrier (not shown) and stored in a container with an appropriate organic dielectric material. An electrical device according to the application 094 further includes a rotor assembly having a plurality of circumferentially spaced permanent magnets, arranged in an axial configuration in relation to the stator assembly. A significant problem that may arise during the operation of a rotating machine, particularly a brushless permanent magnet machine, involves heating the rotor assembly due to the regular variation in the magnetic environment it experiences in the course of a rotation. The concept of a permeance coefficient (Pe) is frequently used to quantify this effect. In particular, the coefficient of permeance is conventionally defined with reference to the magnetization curve of the second quadrant (BH) of a magnet at its point of operation, and is given by the formula Pe = Bd / Hd, where -Hd is the demagnetization field and Bd is the effective magnetic flux density emanating from the magnet, both being taken at the point of operation. Pe changes with the position of the rotor during the operation, and the operating point moves along the curve B-H accordingly, in a way that reflects the flow B that leaves at any given time. The changing magnetic flux continuously induces eddy currents in the rotor as a consequence of Faraday's law. These circulating currents can produce significant heating in the rotor, up to 10 kW or more in a machine estimated at 100 kW, which is severe enough in some cases to cause irreversible losses of magnet, or even destroy the magnets of the rotor. A proposed method to reduce the variation in the permeance coefficient experienced by the rotor magnets is to introduce protruding poles, also referred to as tooth tips, which are formed by a widening of the cross-sectional area of the stator core on the surface presented in the air gap. Almost all conventional radial air gap machines employ poles to increase the magnetic flux directed from the rotor through the stator teeth. The widened pole tips are relatively easy to provide in stamped laminations ordinarily used in radial air gap stators. However, the protruding poles are difficult for machines in the stator of an axial air gap machine, and as a result it is generally prohibitive to add salient poles to an axial air gap machine. The present invention addresses the problem of heating in the motor magnets in a low cost manner and providing a new stator assembly including a front iron. The presence of the frontal iron reduces the variations in the permeance coefficient experienced by the rotor magnets during rotation, and therefore decreases the magnetic flux excursions that produce parasitic currents in the reactor. The amount of heating in the rotor of an electrical device according to the present invention can be greatly reduced for example, from 10 kW to 2 kW or less in a machine rated at 100 kW. As a result, the path of the rotor magnets, and therefore of the electrical device, can be significantly prolonged. While the use of a frontal iron in high-pole electrical machine modalities is especially desirable, low-pole-source devices are also beneficial. As described in Figure 2, a stator mounting form suitable for the present machine is configured by adding a front iron to a stator of the type shown in Figure 1. Initially, a metal core is formed by spirally winding material High frequency low loss strip on a toroid. This toroid has the shape of a generally circular circular cylindrical shell having an initial diameter and an external diameter when viewed in the axial direction. The annular end surface region 22 extending radially from the inner diameter "d" to the outer diameter "D" and circumferentially around the fully formed toroid thus, defines a surface area. The core of the metal has an axial extension that defines a height of the toroid. After winding, the core is machined to provide grooves 16 having outer width "w" which are generally radially directed. The depth of the grooves 24 extends axially only partially through the height of the toroid. The grooves reduce the total surface area of the metal core. The portion of the annular region left after the elimination of the grooves is the total area (TA), also referred to as the amorphous metal area (AMA) for the modalities in which the high frequency, low loss material is a amorphous metal. Because the slots 24 extend completely from the inner diameter d to the outer diameter D, the internal diameters of the stator core in the grooved portion of the toroid are not continuous. Removal of the material from the slot spaces produces a plurality of teeth 14. There is an equal number of teeth and grooves. The continuous circumferential material that remains below the depth of the groove can function as the back iron section 16, which produces closure for flow in the tooth sections 12. In preferred embodiments, the narrowest part of a tooth is not less than 2.5 mm (0.1 inches) for purposes of training capacity and mechanical integrity. The slots 24 are wound with the windings 14 of the stator, conductor, according to a pre-selected winding scheme for a given electrical device design. Ordinarily, a highly conductive, inexpensive wire such as a copper or aluminum wire is preferred, but materials and shapes, including other metals and alloys, and superconductors can also be used. The wire can have any cross section, but round and square wires are the most common. In certain applications of this frequency, threaded wires or wires or Litz wire may be advantageous. A preferred winding scheme involving a winding per tooth 12. Each winding ordinarily comprises multiple turns of conductive wire. However, any winding arrangement known in the art is applicable. The windings can be formed on the site around the teeth, others can be separately prepared as an assembly and slid over the ends of the teeth. The stator assembly 10, together with the stator windings 14, can be placed in a stator carrier (not shown). Preferably, the stator assembly is placed on the carrier or stator using an appropriate organic dielectric material, such as one that does not induce excessive stress in the magnetic material of the stator. While the preferably non-magnetic stator carrier, there is no condition on the conductivity of the stator carrier material. Factors that can influence the choice of stator carrier material include the mechanical strength and thermal properties required. Any suitable material capable of adequately supporting the stator assembly, can be used as a stator carrier. In a preferred embodiment, the stator carrier is formed from aluminum.

The assembly of the stator 10 further comprises the front iron 18. In the embodiment shown in figure 2, the front iron 18 comprises a wound toroid of soft magnetic material of low loss. The frontal iron is independently formed and subsequently coupled to the faces of the teeth. These and other embodiments wherein the stator assembly comprises separate components, can be formed by joining the constituent parts using an adhesive, clamping, welding, and other methods known in the art. For example, a variety of adhesive agents can be used, including those compounds of epoxies, varnishes, anaerobic adhesives, cyanoacrylates, and vulcanized silicone materials at room temperature (RTV). The adhesives desirably have a low viscosity, low shrinkage, low elastic modulus, high peel strength, high operating temperature capacity and high dielectric strength. The stator slots can be wound with stator windings before or after the components are assembled. In some modalities, frontal iron works in other beneficial ways, which may include; (i) the reduction or substantial elimination of the harmonics in the fundamental frequency of the waveform of the voltage or of the current of the device; (ii) improvement of the efficiency of the electrical device; and (iii) the provision of reluctance compensation to reduce the wear of the torque. The front rear iron, the front iron, and the tooth sections are composed of a soft magnetic material. In preferred embodiments, the sections are made of low loss materials such as amorphous metal, nanocrystalline metal, or optimized alloy based on Fe. The same materials do not need to be used in all sections. In preferred embodiments, the front iron is constructed from a coiled toroid of a soft magnetic material. Even in modalities where the rear iron and tooth sections are composed of low loss materials, the front iron can be made from a conventional material. For example, the front iron may employ iron-based, grain-oriented, conventional material, iron-based material, non-grain oriented, or other Si-Fe alloy. The use of bulk material reduces loss of frontal iron while other benefits of the advantages of frontal iron are maximized, as discussed in more detail below. In other embodiments, the front iron comprises an injection molded material, or a powder of a soft magnetic material that is bonded with an adhesive, organic resin and other suitable dielectric.

In the embodiment of a stator assembly 10 shown in Figure 2, the external and internal diameters of the front iron are approximately equal to the external and internal diameters of the stator cores, and the stator windings extend beyond the internal diameter and external of the frontal iron. Preferably, the internal and external diameters of the frontal iron, the rotor assembly and the stator assembly are similar, but need not be identical. In other embodiments, the front iron section is of a different size than the rear iron and the tooth sections of the stator assembly. In particular, one or both of the internal and external diameters of the frontal iron may be larger or smaller than in the corresponding internal and external diameters of the rear iron of the diameter sections. Other forms of stator construction useful in the practice of the present invention are provided by the? 271 and? 094 previously mentioned. Alternatively, a unitary structure provides tooth sections and the front iron. In this implementation of the present method, a relatively larger fraction of the material is removed, in the formation of the grooves, since the frontal iron is ordinarily thinner than the rear iron. A coiled toroidal iron, formed independently, is then coupled to the surface of the stator assembly. The stator slots can be dominated with stator windings before or after the rear iron is engaged. In yet another embodiment, the stator cores, the rear iron and the front iron are all machined as a complete unit assembly from a single coiled toroid of low loss material, and the grooves wound with the stator coil. In another modality, the structures of frontal iron and posterior iron are machined from wound thyroids. Slots and subsections of teeth are provided on one surface of each structure. The structures are assembled in face-to-face relationship with the tooth subsections and each carried in butt engagement. Each tooth section of the stator assembly comprises tooth subsections that depend on the front iron and posterior iron portions. In a further embodiment, the frontal iron and posterior iron sections are formed as cylindrical thyroids and separately formed tooth sections are placed therebetween. In other additional embodiments, the function of the frontal iron is carried out by a smooth iron structure coupled to the rotor in face-to-face relationship with the stator. In axial gap modes, a wound toroid is a suitable form for this frontal iron.

A stator assembly for a radial air gap machine including a front iron provided by a stack of ring laminations is also provided. In an ordinary configuration with an external stator and an internal rotor, the outer diameter of the annular laminations is coupled to the internal diameter formed by the teeth of the stator projecting in an inward direction. Of course, in an internal outward motor, the annular laminations radially and circularly in outer diameter of the stator. The present frontal iron has to be distinguished from a thin shield of conductive material but not magnetically permeable, used to mitigate the magnetic flux variant over time in the rotor structure. However, such a shield can be used in embodiments of the present machine to supplement the benefits of frontal iron. Front Iron Thickness It is preferred that the front iron thickness be selected to optimize the operation of the electrical device. A too thin frontal iron toroid is not effective, for example, in reducing rotor losses. On the other hand, a front iron that is too thick deviates excessively from the magnetic flux path of the rotor and / or the stator to the front iron itself which can significantly reduce the performance of the electrical device. For example, it is preferable that the magnetic flux of the permanent magnets of the rotor be conducted through the axial length of the teeth of the stator and therefore through the stator coils that surround it circularly. Also, the magnetic flux produced by the current flowing through the stator coils is preferably conducted mainly towards the air gap. The optimum thickness for the frontal iron can be in the range of fractions of one millimeter (mm) up to 1 mm, 2 mm, 5 mm, or more. The optimum thickness varies according to the dimensions and operational requirements of the electrical device, the properties of the stator materials, the stator windings, the front iron and the rotor, as well as their intrinsic magnetic properties. In a specific embodiment, for a front iron made from Metglas® 2607SA1 or similar amorphous iron-based alloy, an optimum front iron thickness is in the range of 0.5 to 1 mm, for design of high slot count. High frequency designs, with lower slot count, can benefit from the thicker front iron. The optimum thickness will also vary with the properties of the rotor's permanent magnet materials. Various computer software tools adapted for electromagnetic analysis and available to a person of ordinary skill in the art can be used to co-optimize the thickness of the frontal iron with various parameters that affect the operation of the electrical device. The thickness of the frontal iron is better co-optimized together with other aspects of the structure of the device and the performance characteristics of the device. Examples of important performance characteristics include the selection of a switching frequency (preferably a high frequency), and the maintenance of a low inductance and adequate low speed control. Other structural details such as the optimal balance of the conductor and soft magnetic materials and the dimensions of the tooth and posterior iron sections are influenced by the inclusion of a frontal iron. The incorporation of the iron-based, optimized, nanocrystalline, amorphous, iron-based, grain-oriented material or non-grain-oriented iron-based material in preferred embodiments of the present electrical device makes it possible for the switching frequency of the machine is increased above 400 Hz only with a relatively small increase in core loss, compared to the unacceptably large increase that could be observed in conventional machines. The use of low loss materials in the stator core, consequently allows the development of high frequency, high pole count electrical devices, capable of providing increased energy densities and improved efficiency. In addition, decreases in stator core loss also allow a motor to be operated well beyond a conventional base speed, without the need for declassification of torque and energy or power frequently needed by thermal limits in machines conventionally designed Amorphous Metals Amorphous metals, which are also known as metallic glasses, exist in many different compositions, suitable for use in the present engine. The metallic glasses are typically formed from a molten alloy of the required composition, which is rapidly quenched from the melt, for example, by cooling at a rate of at least about 106oC / second. These no longer show wide-range atomic order and have X-ray diffraction patterns that show only fuzzy haloes, similar to those observed for inorganic oxide glasses. A number of compositions having suitable magnetic properties are described in U.S. Patent No. RE32,925 to Chen et al. An amorphous metal is typically supplied in the form of extended lengths of thin ribbon (e.g., a thickness of at most about 50 μm) in widths of 20 cm or more. A useful process for forming metal strips of indefinite length is described in U.S. Patent No. 4,142,571 to Narasimhan. An exemplary amorphous metal material suitable for use in the present invention is METGLAS® 2605 SAI, sold by Metglas, Inc., Conway, SC in the form of an indefinite length ribbon of up to about 20 cm in width and 20-25 μm. of thickness (see http://www.metglas.com/products/page5 1 2 4.htm). Other amorphous materials with the required properties can also be used. Amorphous metals have a number of characteristics that must be taken into account in the manufacture and use of magnetic implements. Contrary to most soft magnetic materials, amorphous metals (also known as metallic glasses) are hard and brittle, especially after the heat typically used to optimize their soft magnetic properties. As a result, many of the mechanical operations ordinarily used to process soft magnetic conventional materials for engines are difficult or impossible to perform on amorphous metals. The material produced by stamping, punching, or cutting generally results in unacceptable wear of the tools and is virtually impossible on heat-treated, brittle material. Conventional drilling and welding, which are often performed with conventional steels, are also usually excluded. In addition, amorphous metals exhibit a lower saturation flux density (or induction) than conventional Si-Fe alloys. The lower flow density ordinarily results in lower energy densities in engines designed according to conventional methods. Amorphous metals also have lower thermal conductivities than Si-Fe alloys. Since thermal conductivity determines how easily heat can be conducted through a material from a hot location to a cold location, a lower value of thermal conductivity requires careful design of the engine to ensure proper disposal of waste heat. arises from core losses in magnetic materials, ohmic losses in windings, friction, aerodynamic loss and other sources of loss. Improper disposal of waste heat in turn, could cause the motor temperature to rise unacceptably. It is likely that excessive temperature causes premature failure of electrical insulation or other engine components. In some cases, over-temperature could cause a shock hazard or trigger a catastrophic fire or other serious danger to health and safety. Amorphous metals also show a higher magnetostriction coefficient than certain conventional materials. A material with a lower magnetostriction coefficient undergoes smaller dimensional change under the influence of a magnetic field, which in turn could probably reduce the audible noise of a machine, as well as make the material more susceptible to the degradation of its magnetic properties. as the result of the induced stresses during the manufacture or operation of the machine. Despite these challenges, one aspect of the present invention provides an engine that successfully incorporates advanced soft magnetic materials, and allows motor operation with high frequency excitation, for example, a switching frequency greater than about 400 Hz. The construction techniques for the manufacture of the engine are also provided. As a result, of the configuration and use of advanced materials, especially amorphous metals, the present invention successfully provides a motor that operates at high frequencies (defined as switching frequencies greater than about 400 Hz) with a high pole count. Amorphous metals show much higher hysteresis losses at high frequencies, which result in much lower core loss. Compared to Si-Fe alloys, amorphous metals have much lower electrical conductivity and are typically much thinner than ordinary Si-Fe alloys, which are often 200 μm thick or more. These two characteristics promote lower parasitic current core losses. The invention successfully provides an engine that benefits from one or more of these favorable attributes, and thereby operates efficiently at high frequencies, using a configuration that allows the advantageous qualities of the amorphous metal, such as the lower core loss, to be exploited , while avoiding the challenges faced with previous attempts to use advanced materials. Nanocrystalline Metals Nanocrystalline metals are polycrystalline materials with average grain sizes of approximately 100 nanometers or less. Attributes of nanocrystalline metals compared to conventional coarse-grained metals generally include increased strength and hardness, increased diffusibility, improved ductility and firmness, reduced density, reduced modulus, higher electrical resistance, increased specific heat, higher coefficients of thermal expansion, lower thermal conductivity and superior soft magnetic properties. The nanocrystalline metals also have some induction of saturation higher in general than most amorphous metals based on Fe. The nanocrystalline metals can be formed by a number of techniques. A preferred method comprises initially emptying the required composition as a metal glass strip of indefinite length, using techniques such as those shown hereinabove, and forming the ribbon in a desired configuration such as a rolled shape. After this, the initially amorphous material is heat treated to form a nanocrystalline microstructure therein. This microstructure is characterized by the presence of a high density of grains having an average size of less than about 100 nm, preferably less than about 50 nm, and more preferably about 10 to 20 nm. The grains preferably occupy at least 50% of the volume of the iron-based alloy. These preferred materials have low core loss and low magnetrostriction. The latter property also makes the material less vulnerable to the degradation of magnetic properties by stresses resulting from the manufacture and / or operation of a device comprising the component. The heat treatment necessary to produce the nanocrystalline structure in a given alloy, it can be carried out at a lower temperature and finally more prolonged than would be necessary for a heat treatment designed to preserve in it a substantially completely crystalline microstructure. Preferably, the nanocrystalline metal is an iron-based material. However, the nanocrystalline metal could also be based on or include other ferromagnetic materials, such as cobalt or nickel. Representative nanocrystalline alloys suitable for use in the construction of magnetic elements for the present device are known, for example, the alloys described in U.S. Patent No. 4,881,989 to Yoshizawa and U.S. Patent No. 5,935,347 to Suzuki. et al. Such materials are available from Hitachi Metals, Vacuumschmelze GMBH &; Co., and Alps Electric. An exemplary nanocrystalline metal with low loss properties is Hitachi Finemet FT-3M. Another exemplary nanocrystalline metal with low loss properties is Vacuumschmelze Vitroperm 500 Z. Optimized Fe-Based Alloys The present machines can also be constructed with optimized, low loss, iron-based crystalline alloy material. Preferably, such material is in the form of a strip having a thickness of at least about 125 μm, much thinner than conventional steels used in engines, having thicknesses of 200 μm or more, and sometimes as much as 400 μm or more. plus. Grain oriented and non-grain oriented materials can be used. As used herein, an oriented material is one in which the major crystallographic axes of the constituent crystallite grains are not randomly oriented, but are predominantly correlated along one or more preferred directions. As a result of the above microstructure, an oriented strip material responds differently to magnetic excitation along different directions, while a non-oriented material responds isotropically, for example, substantially with the same response to excitation throughout of any direction in the plane of the strip. The grain-enabled material is preferably placed in the present motor with its easy direction of magnetization substantially coincident with the predominant direction of the magnetic flux. As used herein, conventional Si-Fe refers to silicon-iron alloys with a silicon content of about 3.5% or less of silicon, by weight. The limit of 3.5% by weight of silicon is imposed by the industry, due to the poor properties of the metallic work material of the Si-Fe alloys, with higher silicon contents. The core losses of conventional Si-Fe alloy grades resulting from an operation in a magnetic field with frequencies greater than about 400 Hz are substantially higher than those of the low loss material. For example, in some cases, the losses of conventional Si-Fe can be as much as 10 times those of the appropriate amorphous metal, at the frequencies and flow levels found in the machines operating under the frequency and flow levels of the present machines. As a result, in many embodiments, conventional material under high frequency operation could be heated to a point at which a conventional machine could not be cooled by any acceptable means. However, some grades of silicon-iron, referred to herein as optimized Si-Fe, are directly applicable in the direction of a high-frequency machine. The optimized iron-bound alloys useful in the practice of the present invention include silicon-iron alloy grades comprising more than 3.5% silicon by weight, and preferably more than 4%. The iron-based, non-grain-oriented material used in the construction of the machines according to the invention preferably consists essentially of an iron-silicon alloy in an amount in the range of about 4 to 7.5% by weight of silicon . These preferred alloys have more silicon than conventional Si-Fe alloys. Also useful are Fe-Si-Al alloys such as Sendust. The non-oriented, more preferred optimized alloys have a composition consisting essentially of Fe with about 6.5 +/- 1 wt.% Si. More preferably, alloys having approximately 6.5% Si show near zero values of the saturation magnetostriction, making them less susceptible to damaging degradation of the magnetic property, due to the stresses encountered during the construction or operation of a device which contains the material. The objective of the optimization is to obtain an alloy with improved magnetic properties, including reduced magnetostriction and especially, lower core losses. These beneficial qualities are obtainable in certain alloys with increased silicon content elaborated by suitable manufacturing methods. In some cases, these optimized Si-Fe alloy grades are characterized by magnetic core and saturation losses similar to those of the amorphous metal. However, alloys containing more than about 4% Si are difficult to produce by conventional means, due to their fragility due to the short interval ordering. In particular, the conventional lamination techniques used to make conventional Si-Fe are generally incapable of making Si-Fe optimized. However, other known techniques are used to produce optimized Si-Fe. For example, a suitable form of Fe-6.5Si alloy is supplied as magnetic strips of 50 and 100 μm thickness by JFE Steel Corporation, Tokyo, Japan (see also http: //www.jfe-steel .co.jp/ in / products / electrical / supercore / index.html Fe-6.5% If produced by rapid solidification processing, as described in U.S. Patent No. 4, 865, 657 to Das et al., and U.S. Patent No. 4, 265, 682 to Tsuya et al., can also be used.Fast solidification processing is also known to prepare Sendust and the related Fe-Si-Al alloys. of soft magnetic materials can in general be expressed by the following modified Steinmetz equation: L = a • f • Bb + c • fd • Bc, where L is the loss in W / kg, F is the frequency in KHz, B is the magnetic flux density in Tesla peak, ya, b, c, d and e they are all unique loss coefficients for the soft magnetic material.

Each of the above loss coefficients, a, b, c, d and e, can in general be obtained from the manufacturer of a given soft magnetic material.

Especially preferred for use in the present stator structure are magnetic materials of low core loss, characterized by a lower core loss of "L", where L is given by the formula L = 12 • f • B1-5 + 30 • f2.3 # B2.3í where.

L is the loss in W / kg, f is the excitation frequency in KHz, and B is the peak magnetic flux density in Tesla. Rotor Assembly Figure 3 shows a partial exploded view of one embodiment of the electrical device of the invention, including a rear iron 16, a core number 12 of tooth section of the stator, windings 14 of the stator, the front iron 18 and a number of rotor magnets 20. The rotor and stator assemblies are substantially coaxial. In one aspect, the present invention provides a brushless permanent motor with an axial gap, which includes a rotor assembly comprising a plurality of magnets 20 placed in a rotor assembly. The rotor assembly is placed adjacent to the stator assembly and coaxially placed on an axis. The magnets possess alternating plurality and are placed securely circumferentially around the rotor with substantially equal spacing. Different parameters of the rotor magnets, such as size, position, angle, inclination, shape and the like, are selected to achieve the desired operation. The present rotor assembly can take any form that secures the magnets for rotation in proximity to the surface of the front iron of the stator assembly. For example, the rotor magnets 20 can be placed inside or mounted on a rotor carrier. The rotor assembly can include any number of rotor magnets 20. In some embodiments, the rotor magnets extend through the thickness of the rotor, while in others they do not. The magnets can be spaced such that there is little or no circumferential space between the alternating magnets. It is preferable that the spacing between the magnets be selected to have an optimum value which also minimizes the occurrence of torque wear. An optimum spacing is derived by first dividing the area of the low stator loss metal by the stator slot number, to obtain the area of each single metal core tooth. The optimal spacing between the magnets will then be such that the total area of each magnet equals 175 +/- 20% of the area of a core tooth.

Although the rotor magnets 20 have been described as permanent magnets, this is not a requirement. In alternative embodiments, the rotor includes one or more electromagnets or the rotor can be formed from a soft magnetic material for example, in induction motor embodiments of the present electrical device. Rotor Materials Any type of permanent magnet can be used in the present rotor. Rare earth-alloy metal alloy magnets such as samarium-cobalt magnets, other rare cobalt-earth magnets, or rare earth-transition metal-metalloid magnets, eg, NdFeB images, are especially suitable. Alternatively, the structure of the rotor magnet comprises any other sintered permanent magnet material, bonded by plastic or ceramic. Preferably, the magnets have a product of maximum, high BH energy, high coercivity and high saturation magnetization, together with a normal demagnetization curve of the second linear quadrant. More preferably, rare earth-transition, oriented and sintered metal alloy magnets are used, since their higher energy product increases the flow and therefore the torque, while allowing the volume of the permanent magnet material , expensive, be minimized.

Preferably, the rotor arrangement comprises a disc or axial type rotor assembly that includes circumferentially spaced, high energy product permanent magnets, such as rare earth metal-transition (e.g., SmCo) or rare earth-metal magnets. transition-metalloid (for example, NdFeB and NdFeCoB), each having opposite ends that define the north and south poles. The rotor and its magnets 20 are supported for rotation about a motor shaft, for example, on a tree or any other suitable arrangement such that the poles of the magnets are accessible along a predetermined path adjacent to one or more stator mounts, and the frontal iron associated with them. Ordinarily, the shaft is supported by bearings of any suitable type known for rotating machines. The area of the magnet on the rotor has external diameter and internal diameter. In a preferred embodiment, for an axial air gap type rotor, the outer diameter and internal diameter of the magnets 20 are substantially identical to those of the stator assemblies 10. If the outer diameter of the magnets 20 is larger than that of the stator tooth sections 12, then the outer portion of the rotor does not appreciably contribute to the operation. If the outer diameter of the rotor is smaller than that of the stator tooth sections 12, the result is a reduction in the operation of the electrical device. In any case, some of the hard or soft magnetic material present in the machine increases the cost and weight, but without improving the operation. In some cases, the extra material even decreases the operation of the machine. Rotor Losses Preferred embodiments of the present electric machine, including a front iron, provide a number of beneficial attributes, including reduced parasitic current and reduced hysteresis losses in the rotor assembly, and reduction of static crimping (non-regular rotation). of the torque moment and the undulation of the torque moment. In many cases, these benefits displace the added cost and complexity of the addition of the frontal iron, the losses in the frontal iron itself, and the output of the machine slightly diminished. A rotor assembly often includes materials that conduct electricity, such as the permanent magnets themselves or the rotor carrier. As explained above, any conductor in a changing magnetic field will experience an induced voltage, as expressed by Faraday's law. This voltage induced in the conductive material creates circulating currents that are commonly called eddy current. The heat generated by the parasitic currents in the material is given as a function of the current (I) and the resistance (R) by the ordinary expression I2xR. Eddy currents are unwanted sources for losses in any electrical device, since they do not provide useful torque. Therefore, a goal of a device designer is the complete elimination of eddy currents. The dissipation of the parasitic current ordinarily increases with the size of the electrically contiguous blocks, and in proportion to the electrical conductivity of the material. Therefore, the parasitic current dissipation is often reduced by dividing the material into separate laminations by electrically non-conductive material. For this reason, the conventional soft magnetic materials used in transformers and rotary machines are ordinarily formed as thin laminations made by rolling processes. However, the remarkably different mechanical properties of permanent magnet materials make the lamination process much more difficult, if not impractical and cost prohibitive for the construction of rotors. The permanent magnets producing the highest known flow, magnets of the rare earth type are electrically conductive, and are thus prone to exhibit undesirably large parasitic current losses. These losses are theoretically a function of the square of the changing magnetic field, the square of the frequency, and the specific conductivity of the material. In practice, the dimensions of the material (thickness and length of lamination) greatly impact the strength. Non-linear magnetic materials, including hard and soft magnets, show a certain hysteresis in a changing magnetic field, which is a delay in the response of the internal magnetic properties of the materials, as the external conditions vary. The delay can be conceptualized as being caused by internal friction. Hysteresis can be an additional cause of loss due to heating of the material, which varies as a function of the intrinsic magnetic properties of the material. These materials can experience hysteresis in small or "minor" loops, which do not cover the four quadrants of the hysteresis B-H curve and thus represent less than a complete magnetization reversal. For example, in soft magnetic material these minor loops are generally found in the first or third quadrant of curve B-H. Hard magnets, such as those used in the rotor assembly in certain implementations of the present machine, arise such minor loops in the second or fourth quadrant, as a result of the cyclic permeance variation, as described hereinabove. The area of each loop represents losses due to loss of hysteresis to the electrical device.

Variations in the Permeance Coefficient As noted above, the rotor of an electric machine almost invariably experiences a significant cyclic variation in the flux density as the magnetic circuit of the rotor / stator changes with rotation. This change is better understood by reference to the coefficient of permeance. The coefficient of permeance (Pe) can serve as a measure of the ability of the magnetic circuit of the rotor, the stator and the air gap to drive the magnetic flux. As the rotor rotates, the permeance coefficient is maximum at the positions at which the rotor magnet is most closely aligned with a stator core tooth and minimum when the magnet is located at the intermediate position between the teeth. The magnetic flux density, inside and outside the rotor magnet, varies commensurately. This is a periodic variation of the flux density within the rotor magnet, which induces the parasitic currents that give rise to the heating. The frequency at which the parasitic current and the hysteresis loss occur is usually not the expected synchronous frequency of the machine, which is given by the equation: Synchronous sequence = speed x number of permanent magnet pole pairs (rotor) Rather, these losses occur at a frequency with which the rotor magnets are moving in and out of varying conditions of the permeance coefficient, which is given by a function of the number of stator teeth: Rotor loss frequency = speed per number of stator teeth This frequency of rotor loss is three times greater than the synchronous frequency for an electrical device with one slot per phase per pole ratio of 0.5, as discussed below in more detail herein. Impact of Front Iron on Rotor Loss The addition of front iron to the stator assembly greatly modifies the permeance coefficient at all positions for the rotor. The frontal iron reduces the magnitude of the low-high-low flow variations that are inevitably present without the addition of the frontal iron. Beneficially, the front iron provides a low reluctance flow path that partially "bridges" the open slots in the stator with the soft magnetic material. The graph of Figure 4 shows that, as the variations in B in the rotor with the increasing thickness of the front iron decrease, so does the unwanted stray current and the hysteresis losses in the rotor.

Reduction of the static curl of the torsional moment and ripple of the torsional moment An additional benefit observed in some machines that include a frontal iron is a reduction in the ripple of the torsion moment and the static ripple of the torsion moment. Desirably, a machine could operate with a torque that does not vary with the angular position of the rotor. However, as explained above, an electric machine inevitably has some variation in the permeability of its rotor-stator magnetic circuit with the angle of the rotor. Therefore, there is inevitably also some variation of the torque. A designer of electrical machines preferably attempts to eliminate the variations of the torque to produce a smooth output with substantially constant torque. The undulation of the excess torque also gives rise to undesirable acoustic noise. In the technique of dynamo-electric machines, a distinction is often made between the static crimping of the torque and the undulation of the torque. The first one refers to the disturbances or to the variation of the torsional moment with rotational position without input / output of current to the machine, while the latter refers to the variation of the torque during the operation, for example under load of energy. However, undulation and static curling are physically related phenomena, and are sometimes considered interchangeable. The ripple of the torque is affected by the design of the electrical device and by the operation of the electronic energy components. The static ripple of the torque is largely dependent on the design parameters of the machine. Since the present invention is primarily related to the design of the electrical device, however, the static ripple of the torque and the ripple of the torque can be considered together. The addition of the frontal iron reduces the variations in the permeance coefficients for the different positions, causing the absolute value of the magnetic flux crossing the air gap to be more constant. As a result, the static ripple of the torque is reduced. If the thickness of the frontal iron is increased without limit, then the static curling of the torsional moment approaches zero. The static ripple of the torque is affected by variations in the permeance coefficient. As predicted by Gauss's law, at any given moment in time, the net magnetic field that crosses the air gap is zero. However, there are positions of the rotor, in relation to the stator, where the coefficient of permeance is higher than for other positions. In these positions the absolute value of the magnetic flux is higher than for the positions where the coefficient of permeance is lower. The movement of the rotor from the high positions Pe to the low positions Pe results in production at the torque moment. For example, in a device with an SPP value of 0.5, there are six high permeance positions for each rotor pole pair. The static ripple of the torque is observed as a result of the "jump" of the rotor from a position of high permeance coefficient to the next position of high permeance coefficient. Effect of Frontal Iron on Functioning and Losses The addition of frontal iron increases the cost of the device, through the use of additional material and the addition of processing steps, but this cost is ordinarily offset by the many gains in the operation of the device. electrical device. The output of any machine is dependent to a great extent on the interaction of the magnetic flux in the air gap. Unexpectedly, the use of a front iron with a properly chosen thickness, effectively increases the amount of magnetic flux in the stator cores, relative to the conditions without the frontal iron. An increase in the amount of magnetic flux in the stator cores, beneficially increases the output of the electrical device. However, the increase is slight, and generally occurs for front iron stators of the order of 0.25 mm or less, as shown in Figure 5. A front iron that is too thick reduces the amount of stator magnetic flux, produced by the current flowing in the coils of the stator, which reaches the air gap, since the front iron can cause the flow coming from a stator core (including the tooth) to be "derived" to an adjacent stator core or tooth. Therefore, optimization of the thickness of the frontal iron should take into account the impact on the "output of the device." The frontal iron itself undergoes flux change, resulting in loss of hysteresis and eddy current, which can be significantly reduced by the selection of a low loss material and optimizing adequately the thickness of the frontal iron The addition of the frontal iron also results in slightly higher flow densities in the stator core, while not producing greater output from the torsional moment. Flow densities in the core structure will inevitably result in higher core losses, as illustrated in Figure 6. In most cases the aggregate losses in the stator are more than displaced by the decreased losses in the rotor magnets. Accordingly, it is preferred that the stator losses be considered in optimizing the thickness of the front iron, so that the overall operation of the machine is increased. Design of High Frequency, High Pole Count, Using Low Loss Materials The present structure and method are applicable to electrical devices that have a pole count in the low to high range. However, the benefits of including a frontal iron are especially verified in the modalities where the use of materials of low loss in the stator, allows the design of electrical devices with high pole counts operating at high frequencies. In specific embodiments, the present invention provides an electrical device between axial iron, with a high pole count operating at high frequencies, for example, a switching frequency greater than about 400 Hz. In some cases, the device is operable at a communication frequency in the range of approximately 500 Hz to 3 kHz or more. Designers have ordinarily avoided high pole counts for high-speed motors, since conventional stator core materials, such as Si-Fe, can not operate at the proportionally higher frequencies needed by the high pole count. In particular, the known devices using Si -Fe can not be changed at magnetic frequencies significantly above 400 Hz, due to the core losses resulting from the changing magnetic flux within the material. Above that limit, core losses cause the material to heat up to the point where the device can not be sent by any acceptable means. Under certain conditions, the heating of the Si-Fe material can even be severe enough that the machine can not be cooled in any way, and will self-destruct. However, it has been determined that the low loss characteristics of the iron-based, amorphous, nanocrystalline and optimized, suitable metals allow higher switching or switching speeds than those that are possible with conventional Si-Fe materials. While in a preferred embodiment, the choice of the amorphous metal alloy such as the METGLAS® 2605SA1 alloy eliminates system limitation due to heating at high frequency operation, the rotor design and the complete motor configuration are also improved to take better advantage of the beneficial properties of the amorphous material. The ability to use much higher excitation frequencies allows the present machines to be designed with much wider ranges of possible pole counts. The number of poles in the present device is a variable based on the permissible size of the machine (a physical constraint) and the expected operating range. Subject to the permissible excitation frequency limits, the number of poles can be increased until the leakage of the magnetic flux increases to an undesirable value, or the operation begins to decrease. The use of a frontal iron also helps to minimize leakage. There is also a mechanical limit presented by the construction of the stator on the number of poles of the rotor, since the stator slots must coincide with the magnets of the rotor. The mechanical and electromagnetic constraints together limit the number of slots that can be made in the stator. These effects, in turn, are in part a function of the size of the machine structure. Some limits may be established to determine an upper limit on the number of slots for a given stator structure that provides an adequate balance of copper and soft magnetic material. The adjustment of the balance can be used as a parameter in the manufacture of axial air gap machines, that work well. The present invention provides motors that optimally have approximately 4 or 5 times the number of poles typical for current industrial machines. As an example, for a typical industrial motor that has 6 to 8 poles, and operating speeds of approximately 800 to 3600 rpm, the switching frequency is approximately 100 to 400 Hz. The switching frequency (CF) is the rotation speed multiplied by the number of pole pairs, where the pole pairs is the number of poles divided by two, and the rotation speed is in units of revolutions per second (CF = rpm / 60 x pole / 2). Also available in the industry are devices with 16 or more poles, but speeds of less than 1000 rpm, which still correspond to a loss of frequency of 400 Hz. Alternatively, motors with a relatively low pole count (for example less than 6 poles) are also available, and with speeds up to 30,000 rpm, which still have a switching frequency of less than about 400 Hz. In representative embodiments, the present invention provides machines having 96 poles, for 1250 rpm at 1000 Hz, 54 poles for 3600 rpm at 1080 Hz; 4 poles for 30000 to 1000 Hz; and 2 poles for 60000 to 1000 Hz. The high frequency machines of the invention can operate at frequencies of approximately 4 to 5 times higher than known axial air gap motors, made with conventional materials and designs. The machines provided are generally more efficient than the typical engines in the industry, when operated in the same speed range, and as a result provide greater speed options. The present configuration is particularly attractive for the construction of engines having a very wide range of speed, energy and torque ratings, in a way that combines high energy efficiency, high power density, ease of assembly, and Efficient use of hard and expensive soft magnetic materials. Thermal Properties and Efficiency One of the characteristics that limits the achievable efficiency of the output or output of the device in all electric machines, including those that use conventional Si-Fe alloys, and those that use optimized Si-Fe alloy, nanocrystalline, amorphous Iron-based metals oriented in grain or non-grain-oriented iron-based metals, is the loss of energy to discard heat. This waste heat comes from a number of sources, but predominantly from ohmic losses, losses due to film and proximity in the windings, rotor losses from eddy currents in magnets and other rotor components, and loss of the resulting core. of the stator core. The "continuous power limit" of conventional machines is often determined by the maximum speed at which the machine can operate continuously, while still dissipating enough of the waste heat to prevent an unacceptable temperature rise. The limit of continuous energy is a function of the current. In the high-frequency, high-frequency electric pole devices, optimally applicable in the practice of the present invention, less waste heat is generated because the iron-based, amorphous, nanocrystalline and optimized metal alloy has lower losses than the conventional Si-Fe. The designer can exploit the low loss characteristics of these materials by increasing the frequency, speed and energy, and then correctly balance and "exchange" the low core loss versus the ohmic loss. In general, for the same power as conventional machines, the high-count, high-frequency electric devices optimally applicable in the present invention show less loss, and therefore higher torques and speeds, and can thus achieve higher continuous speed limits than conventional machines. One advantage of the preferred machine in practicing one aspect of the present invention is the ability to maximize the efficiency of the device, while maintaining cost effectiveness. As is conventional, the efficiency of the device is defined as the output of useful energy divided by the energy input. The high frequency, high frequency pole counting devices optimally applicable in the present invention simultaneously operate at higher switching frequencies with high pole count, resulting in a more efficient device having low core and high core losses. energy density. These exceed the standard high frequency limit in the industry of 400 Hz, beyond which there have been few, if any, practical applications so far. The operation and increased efficiency of the high-frequency, preferred, high-pole electrical devices applicable to the present invention is not simply an inherent characteristic of conventional Si-Fe replacement., with amorphous metal. A design number has been proposed, but they have met operating failure (including overheating and lower output power). It is believed that this failure has arisen to a large extent as a result of merely applying new materials (eg, amorphous materials) and production methods so that they were designed for and suitable for a conventional material (Si-Fe containing 3.5% or less of silicon by weight). The failure of early operation, combined with the perceived cost of processing amorphous metal in engines, led the industry to abandon research efforts.

The high-frequency, high-frequency, pole-counting electric devices optimally applicable in the present invention overcome the malfunctions of the prior art through the design of a rotating electrical device that exploits the properties of optimized Si-Fe alloy materials , nanocrystalline, amorphous, low Fe materials oriented in grain or non-grain oriented Fe based materials. Construction methods compatible with the physical and mechanical characteristics of the various improved materials have also been provided. These designs and the method provide machines that possess some or all of the various advantageous qualities, including operation at switching frequencies greater than 400 Hz, with a high pole count, at high frequency and with a high energy density. While other conventional methods have been able to provide motors with at most one or two of the four qualities, among the embodiments provided herein are the high-pole, high-frequency electric devices that show some, and preferably the four qualities simultaneously. Compared to machines such as those provided by the application N 094, the present machine provides yet another mechanism by which losses in the rotor can be reduced, namely through the use of a front iron in the stator assembly. .

In many embodiments, the present high frequency pole counting electric machines show good efficiency. A greater contribution to improvement results from significantly reduced hysteresis losses. As is known in the art, the hysteresis losses result from the impeding domain wall motion during the magnetization of all soft magnetic materials. Such losses are generally higher in conventionally used magnetic materials, such as conventional grain oriented Si-Fe alloys, and non-oriented motor steels and electric steels, than in the improved materials preferably used in the present machines. The high losses, in turn, can contribute to the overheating of the core. As a result of the increased efficiency, high frequency pole counting electrical devices, optimally applicable in the present invention, are capable of achieving a greater continuous speed range. Conventional motors are limited in that they can provide either low torque for high speed (low power) intervals, or high torque for low speed intervals. High frequency, high frequency pole counting devices, optimally applicable in the present invention, successfully provide electrical devices with high torque for high speed intervals. Slot Proportions Per Phase by Pole The slot value per phase per pole (SPP) of an electric machine is determined by dividing the number of stator slots by the number of phases in the stator winding and the number of DC poles (SPP). = slots / phases / poles). In the present description, a pole refers to the non-time-varying magnetic field, also referred to herein as a DC field, which interacts with a changing magnetic field, for example, one that varies in magnitude and direction with time and the position. In the preferred embodiments, the permanent magnets mounted on the rotor provide the DC field, and therefore the number of non-time-varying magnetic poles, referred to herein as DC poles. In other embodiments, a DC electromagnet can provide the DC field of the rotor. The electromagnets of the stator windings provide the changing magnetic field. A slot refers to the spacing between the alternating teeth of the stator of the present machine. The techniques of the present invention are applicable to electrical devices with any SPP value. Beneficially, the design of the present machine provides considerable flexibility in the selection of an optimal SPP ratio.

Conventional machines are often designed to have an SPP ratio of 1 to 3, to obtain acceptable functionality and acceptable noise levels, and to provide smoother output due to the better distribution of the winding. However, designs with a lower SPP value, for example 0.5, have been sought to reduce the effect of the final turns. The final turns are the portions of wire in the stator coils that connect the windings between the slots. Although such a connection is required, of course, the final turns do not contribute to the torque and output of the machine. In this sense, these are undesirable, because they increase the amount of wire required and contribute with ohmic losses to the machine while not providing benefits. Therefore, one goal of the engine designer is to minimize the final turns and provide a motor with manageable static noise and curly. On the other hand, preferred implementations of the present engine allow a reduced SPP ratio, together with desirably low static ripple, static undulation, and electronic ripple, described in greater detail hereinafter. Such benefit is obtained through the operation with a high count of poles and slots. These options were not feasible in previous machines, because the required increase in the switching frequency is unacceptable without the use of advanced low loss stator materials. For some applications, it is advantageous to build an engine with a fractional SPP value, since such an engine can employ preformed coils positioned around a single stator tooth. In different embodiments of the present machine, the SPP ratio is an integral ratio, such as 0.25, 0.33 or 0.5. SPP values of 1.0, or even greater than 1.0, are also possible. Preferably, the SPP values are in the range of about 0.25 to 4.0-. However, more preferred embodiments of the present machine are beneficially designed with an SPP ratio of 1 or less, and still more preferably of 0.5 or less. It is possible to wire multiple horseshoes within a common magnetic section, providing an SPP greater than 0.5. This is the result of the existence of a larger number of rotor pole stator slots, resulting in a distributed winding. An SPP value less than or equal to 0.5 indicates that there are no distributed windings. A convention in the industry is to include windings distributed in the stator. Ordinarily, prior art machines designed with distributed windings have many slots per pole, resulting in operation at a lower frequency. As a result, in conventional machines that have SPP of 0.5 or less, and operate at low frequency, there will also be a low pole count, and a high static ripple difficult to control. On the other hand, the use of advanced magnetic materials in the present machine, allows the switching frequency to be high, so that the low values of SPP can be maintained, while at the same time the static ripple is reduced to a minimum and without reduce the speed of the machine. However, while the methods of the present invention are applicable to an electrical device with SPP values below 0.5 (eg 0.25), such configuration is sometimes made less desirable by practical considerations, including machine reactance increased at the higher switching frequency required, increased leakage flow increased from the rotor magnets, and the necessary mechanical support to accommodate rotor magnets that are smaller and numerous. A lower value of SPP is often less advantageous for other important parameters of the electrical device as well. On the other hand, the increase in the value of SPP effectively increases the pole separation of the machine. For example, the multiple stator slots can be wired in a common magnetic section, which corresponds to a slot value per phase per pole (SPP) greater than 0.5.

Although the present machine can be designed and operated as a single-phase device, or a polyphase device with any number of phases and a commensurate number of windings on each of the stators, a three-phase machine with three-phase windings is preferred according to the industry convention, since it provides efficient use of hard and soft magnetic materials, along with good energy density. Modes with SPP ratios of 0.5 are particularly suitable for three phase applications. For example, in a three-phase machine, with a slot / pole / phase ratio = 0.5, the number of rotor poles is two thirds the number of stator slots, with the number of slots being a multiple of the number of phases. While the machine is usually wired in a three-phase star configuration according to the industry convention, a delta configuration can also be employed. In a preferred embodiment provided by the present invention, the front iron is applicable to an electrical device with an SPP value optimally equal to 0.5. Flexibility in Wiring / Winding Design An additional advantage of certain embodiments of the present machine is the flexibility of using different wiring configurations. Traditional stator designs limit the design choices of the winding, due to the aforementioned focus on the use of SPP ratios of 1.0 to 3.0, which require the distribution of the windings over multiple slots. It becomes difficult to have more than two or three winding options with distributed windings. The present invention provides the ability to take advantage of the design of SPP = 0.5, where there is typically a discrete winding per stator core (including the tooth). However, the invention does not exclude other arrangements with SPP = 0.5. The single core coil can be easily modified and reconnected to provide any voltage demanded by a given application. Thus, given an SPP ratio approaching 0.5 as in the device of this invention, there is significant flexibility for configurations of stator windings. For example, the manufacturer can wind each stator separately from each other, or the manufacturer can provide separate stator windings within the same stator. This capability is one of the advantages of a system with an SPP equal to 0.5. Although there have been occasional systems in the industry that employ SPP = 0.5, these are not widespread and have met successfully only in niche applications. The present invention successfully provides a system with SPP equal to 0.5 that allows this flexibility in the winding. In this way, a given hardware (hardware) configuration can provide a wide range of solutions, simply by changing the stator coils or their interconnection. In general, the coil is the easiest component to modify in an electromagnetic circuit. Economies and significant simplification are provided to the manufacturer, who needs fewer standard designs, to the distributor, who can maintain a simpler inventory, and to the user, who can modify a given machine to accommodate changing usage requirements. Machine System and Electronic Power Control In yet another aspect, a dynamo-electric machine system is provided comprising an axially-axial electric-air machine of the aforementioned type, and the electronic power means for interconnecting and controlling the machine. The system can function as a motor or generator or a combination thereof. The motorized machines can be supplied with AC power, either directly or by DC power switching. Although mechanical switching has been widely used with brush-type machines, the availability of high-energy semiconductor devices has enabled the design of electronic switching means without a brush, which are used with many modern permanent magnet motors. In generation mode, a machine (unless mechanically switched) inherently produces AC. It is said that a large proportion of machines operate synchronously, which means that the AC input or output energy has a frequency commensurate with the rotational frequency and the number of poles. Synchronous motors directly connected to a power grid, for example, the 50 or 60 Hz network commonly used by electrical installations, or the 400 Hz network frequently used in aerospace and ship systems, therefore operate at particular speeds , with variations obtainable only when changing the pole account. For synchronous generation, the rotational frequency of the primary source must be controlled to provide a stable frequency. In some cases, the primary source inherently produces a rotational frequency that is too high or too low to be accommodated by motors that have pole counts within practical limits for known machine designs. In such cases, the rotary machine can not be connected directly to a mechanical axis, so that a gearbox must frequently be employed, despite the expected aggre complexity and loss in efficiency. For example, wind turbines rotate so slowly that an excessively large pole count may be required in a conventional motor. On the other hand, to obtain adequate operation with desired mechanical efficiency, typical gas turbine engines rotate so rapidly that even with a low pole count, the generated frequency is unacceptably high. The alternative for applications in engines and in generation is the conversion of active energy. The embodiments of the present electric machine that include a stator assembly with a front iron, are beneficially employed with the conversion of active energy, especially in applications involving a wide range of speeds and / or energy requirements triggered. As used herein, the term "electronic energy component" is understood to mean the set of electronic circuits adapted to convert the electrical energy supplied as direct current (DC) or as alternating current (AC) of a frequency and form of Particular waveforms at the output of electrical energy such as DC or AC, the output and the input differ in at least one of the voltage, frequency and waveform. The conversion is achieved by a set of electronic energy conversion circuits. For a different voltage transformation from a simple, AC power using an ordinary transformer that preserves the frequency, and simple AC bridge rectification to provide DC, the modern energy conversion ordinarily employs non-linear semiconductor devices and other associated components that provide active control. As discussed hereinabove in greater detail, machines constructed in accordance with the present invention are operable as motors or generators over a much wider range of rotational speed than conventional devices. In many cases, the gearboxes required up to now in motor and generator applications can be eliminated. However, the resulting benefits also generally require the use of operable electronic components over a wider electronic frequency range than that used with conventional machines. For motor applications of the dynamo-electric machine system, the machine is interconnected to an electrical source, such as the electric power grid, electrochemical batteries, fuel cells, solar cells or any other suitable source of electrical energy. A mechanical load of any required type can be connected to the shaft or shaft of the machine. In generation mode, the machine shaft is mechanically connected to the main source, and the system is connected to an electrical load, which can include any form of electrical appliance or electrical energy storage. The machine system can also be used as a regenerative engine system, for example as a system connected to the drive wheels of a vehicle, alternatively providing mechanical propulsion to the vehicle and converting the vehicle's kinetic energy back to electrical energy stored in a vehicle. battery, to effect braking. The electronic power means useful in the present axial air gap machine system should ordinarily include active control with sufficient dynamic range to accommodate the expected variations in mechanical and electrical load, while maintaining satisfactory electromechanical operation, regulation and control. satisfactory control. The means must function satisfactorily over the range of phase impedances arising from the aforementioned changing permeance, during each revolution. Any form of energy conversion topology can be used, including reducing regulators, elevators and horizontal sweeping, and pulse width modulation. Preferably, the voltage and current are independently controllable of the phase, and the control of the electronic components of energy can operate with or without direct detection of the position of the axis. In addition, it is preferred that four quadrant control be provided, allowing the machine to operate for clockwise or counterclockwise rotation, and either in the motor or generation mode. The loop loop current loop control circuitry is preferably included, whereby control can be employed in the torque mode and the velocity mode. For stable operation, the electronic energy means should preferably have a frequency range of the control loop at least about 10 times as large as the intended switching frequency. For the present system, the operation of the rotating machine of up to about 2 kHz switching frequency thus requires a control loop frequency range of at least about 20 kHz. The controllers used in monitoring operations typically employ IGBT semiconductor switching elements. These devices show an increase in switching losses with frequency, so that it is ordinarily preferred to operate with switching frequencies of up to about 1000 Hz. The motor systems are thus advantageously designed with a switching frequency in the range of about 600 to 1000 Hz, allowing the use of less expensive IGBTs, while retaining the benefits (e.g., increased energy density) resulting from the highest operating frequencies made possible by low loss materials. For generation applications, suitable rectifier bridges allow operation even at higher switching frequencies.

The following examples are provided to more fully describe the present invention. The techniques, conditions, materials, proportions and specific reported data, described to illustrate the principles and practice of the invention, are exemplary and should not be considered as limiting the scope of the invention. EXAMPLES Optimized Front Iron Thickness for the 15 kRPM Electrical Device An optimized frontal iron thickness analysis is performed for a low-frequency, high-frequency, 15 kRPM electric device with the following specifications: The machine includes a rotor and a stator and is a three-phase, high-frequency electrical device with low pole count, which runs as an actively rectified generator at 15 kRMP. The frontal iron is constructed from the amorphous metal METGLAS 2605SA1 wound as a toroid. The analysis is repeated for similar electrical power output devices of 100 kW, with frontal iron thickness in the range of 1.9 to 6.4 mm, and compared with the properties of a device without such frontal iron. The rotor is made of permanent high-energy FeNdB magnets housed in a carrier made of non-electrically conductive compound, which reduces losses. As shown in Figure 7, the expected EMF of the line falls sharply with the addition of the frontal iron. It is believed that this results from the saturation of the thinner frontal iron. As the thickness of the front iron increases to 4 mm, the on-line EMF reaches a reasonably high, optimum value of 300 V. Figure 7 also shows that the inductance constant (KI) increases gradually with increasing iron thickness frontal . It is believed that this is a consequence of the flow path provided by the front iron joining the stator phase coils to each other. By way of contrast, the "open end" configuration of a device without the front iron provides a greater reluctance for this flow. The inductance is an average inductance calculated by the electromagnetic analysis software for the device under a load (torque). The inductance constant varies as a function of the applied current in the case of the frontal iron. An important motivation to introduce the frontal iron, is the reduction of the total losses of the device. Figure 8 shows a graph of the losses and the loss density of the device, as a function of the thickness of the frontal iron. Surprisingly, the complete losses of the device can be reduced to 40% of the initial, mainly due to a reduction in the losses in the rotor magnets due to parasitic currents. This in turn decreases the dissipation density of the complete waste (W / cm2) of the machine, thereby increasing the available energy, torque and speed, without appreciably increasing the size of the machine. The lower dissipation is achieved despite the impact of the additional frontal iron losses and the increased axial length, and therefore the increased surface area, with the introduction of frontal iron, these factors being included in the loss estimate. As the EMF changes for a constant energy of 100 kW, the current also changes, changing the ohmic losses in turn. Figure 9 shows that the energy factor decreases with the thickness of the frontal iron, as the inductance increases, which represents a penalty in addition to the frontal iron. However, the efficiency increases dramatically, as a result of the savings in the parasitic current losses of the magnet. Figure 10 shows that the static ripple of the torque is reduced as the thickness of the front iron is increased. However, there is an increase in the undulation of the torque with the increase in the thickness of the frontal iron. These are preferably taken into account in optimizing the thickness of the frontal iron and the operation of the device. The optimum thickness of the front iron is found to be in the range of 4 to 5 mm for the 15 kRPM electrical device, high frequency, low pole count. The addition of the front iron results in less heating of the rotor, reducing heating from a high of approximately 16 kW to a low of approximately 2 kW. The addition of the frontal iron also results in greater efficiency. A 4 mm front iron thickness is easily manufactured with the technology currently available. Having thus described the invention in full detail, it will be understood that such details do not need to be strictly complied with, but that various changes and modifications may be suggested to themselves by a person skilled in the art. For example, although electric axial air gap machines have been generally described herein, other types of electrical machines can be designed according to the principles described herein, such as radial air gap machines or linear machines. In addition, electrical machines could include a number of type of electrical machines different from permanent magnet machines, such as induction machines, synchronous machines, synchronous reluctance machines, switch reluctance machines, and direct current electromagnet machines . In addition, other types of rotor and / or stator winding schemes are within the scope of the present invention. It is therefore intended that such modifications be encompassed by the scope of the invention, as defined by the following claims. It is noted that in relation to this date, the best known method for carrying out the aforementioned invention is that which is clear from the present description of the invention.

Claims (19)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A dynamoelectric machine, characterized in that it comprises: (a) at least one stator assembly comprising a rear iron section and a plurality of tooth sections, the stator assembly has a slot between each adjacent pair of the tooth sections and the teeth. stator windings wound through the slots; (b) a frontal iron section; and (c) at least one rotor assembly supported for rotation about an axis, and including a plurality of poles, the rotor assembly is accommodated and positioned for magnetic interaction with at least one stator assembly.

2. The machine according to claim 1, characterized in that the machine is an axial air gap device.

3. The machine according to claim 1, characterized in that the machine is a radial air gap device.

The machine according to claim 1, characterized in that the front iron section is a part of the stator assembly.

The machine according to claim 4, characterized in that at least one of the rear iron section, the plurality of tooth sections, and the front iron section is composed of at least one magnetic material of low core loss, selected from the group consisting of an amorphous metal, a nanocrystalline metal, and an optimized iron-based alloy.

The machine according to claim 5, characterized in that the magnetic material of low core loss is characterized by a lower core loss of "L" when operating at an excitation frequency "f" at a peak induction level. "Bmax" where L is given by the formula L = 12 • f • B1-5 + 30 • f2'3 • B2-3, the core loss, the excitation frequency and the peak induction level that are measured in watts per kilogram, kilohertz and teslas, respectively.

The machine according to claim 4, characterized in that at least one of the front iron section and the rear iron section is formed as a unitary structure comprising the tooth sections.

The machine according to claim 1, characterized in that the rotor assembly comprises a rotor having a plurality of rotor permanent magnets positioned with alternating polarity and placed securely and circumferentially around the rotor, with substantially equal spacing.

The machine according to claim 8, characterized in that the magnets are SmCo or FeNdB magnets.

10. The machine according to claim 1, characterized in that the ratio of groove to phase per pole is in the range of approximately 0.25 to 1.

11. The machine according to claim 10, characterized in that the ratio of slot per phase per pole is 0.50.

12. The machine according to claim 1, characterized in that it has at least 16 poles.

The machine according to claim 1, characterized in that it is adapted to run with a switching frequency in the range of approximately 500 Hz to 3 Hz.

The machine according to claim 2, characterized in that it comprises two stator assemblies and a rotor assembly placed between them.

15. A method for building a dynamoelectric machine, characterized in that it comprises: (a) providing at least one stator assembly comprising a rear iron section and a plurality of tooth sections, the stator assembly has a slot between each adjacent pair of teeth. sections of teeth and stator windings wound through the slots; (b) the provision of a frontal iron section; and (c) the provision of at least one rotor assembly supported for rotation about an axis, and including a plurality of pores, the rotor assembly is accommodated and positioned for magnetic interaction with at least one stator assembly.

The method according to claim 15, characterized in that at least one rear iron section, the plurality of tooth sections, and the front iron section is composed of at least one low core loss magnetic material, selected from the group consisting of an amorphous metal, nanocrystalline metal, and optimized alloy based on iron.

The method according to claim 15, characterized in that at least one of the front iron section and the rear iron section is formed as a unitary structure comprising the tooth sections, the unitary structure is formed by a process that it comprises the steps of: (a) spirally spiraling a toroid from the laminated layers of the low loss core magnetic material, the toroid having an internal diameter, an external diameter, and a height of toroid; and (b) cutting a plurality of grooves extending substantially radially from the inner diameter to the outer diameter, and having a groove depth less than the height of the toroid.

The method according to claim 15, characterized in that the front iron section is formed by spirally coiling a toroid of the laminated layers of the low core loss magnetic material.

19. The dynamoelectric machine according to claim 1, characterized in that it also comprises the electronic energy means for interconnecting and controlling the machine and that are operably connected thereto.