MXPA00009625A - Electrical machine element - Google Patents

Abstract

A stator assembly for an electrical machine comprises a core made of a magnetic material. The core has an annular yoke (2) and a plurality of teeth (3) spaced circumferentially on the annular yoke and extending radially therefrom. The spaces between the teeth define circumferentially spaced winding slots (6). A stator winding is carried by the stator core and has coil turns located around the teeth and in the winding slots. Each tooth and a radially adjoining part (4) of the yoke have varying axial dimensions in order to adjust the magnetic flux to an optimal flux density in each part of the magnetic flux path in the stator. The annular yoke (2) may extend axially past the teeth (3) at least at one of the axial sides thereof.

Description

ELEMENT FOR ELECTRIC MAQUINAS TECHNICAL FIELD The present invention generally relates to electrical machines, especially motors, and is directed more specifically to the structure of the stator or rotor assembly thereof.

BACKGROUND OF THE INVENTION AND PREVIOUS TECHNIQUE Electric machines have a stationary element and a moving element. The mobile element may be a rotating element or a non-mobile element. The interaction between the stationary element and the mobile element is based on the interaction of a magnetic field, generated either by the stationary element or by the mobile element, and the electric currents in a winding in the moving element or the stationary element, respectively . The interaction is such that the direction of the current, the direction of the magnetic field and the direction of the movement are at substantially right angles to each other; for example, along an x direction, an y direction and a z direction of a right angle coordinate system.

The winding consists of a plurality of coils wound around the teeth of a flexible magnetic material usually constituted by steel laminations to reduce leakage currents. Although the winding can be wound on the stationary element or on the movable member, the following description will be limited to the winding as part of a stator assembly. Commonly, the stator assembly of an electrical machine has a stator core formed of a stack of steel laminations. As an alternative to the use of steel laminations, the stator core may be formed of iron powder, as exemplified in the US patent. No. 4,947,065, which describes a stator molded in a single piece, and in the international patent application W095 / 12912, which describes a stator consisting of a plurality of substantially identical and separate parts. By its very nature, any compact material not concreted will not be totally dense. This means that the currently available sweet iron powder will have lower permeabilities than the permeabilities obtainable with the steel laminations. However, mixed materials of magnetic powder could offer advantages such as isotropic magnetic behavior, reduction of iron losses at high frequencies, improved thermal characteristics and flexible design and assembly.

BRIEF DESCRIPTION OF THE INVENTION An object of this invention is to provide an element for electrical machines, specifically a stator assembly, which reduces the cost of the machine without loss of performance. An element for electrical machines according to this invention is characterized by the features specified in appended claim 1. The preferred embodiments of this element for electrical machines are defined In a first embodiment, the core and the winding constitute a stator assembly for a rotating electrical machine. Therefore, the core tends an annular fixed part and a plurality of circumferentially spaced teeth in the annular fixed part, and the spaces between the teeth define the circumferentially spaced winding grooves. In a preferred embodiment, the teeth extend radially from the fixed part, and each tooth and the adjacent part of the fixed part have different axial dimensions. Alternatively, the teeth may extend axially from the fixed part, in which case each tooth and the adjacent part of the fixed part will have different radial dimensions. The teeth of the core can have a rounded profile, in such a way that the sharp bending of the turns of the spirals is eliminated and the risk of penetration of the insulation in the corners is reduced. This allows the lighter insulation to be used resulting in a substantial thermal benefit. In a preferred embodiment of the previous stator assembly, each tooth forms a separate unit or segment with an adjacent part of the fixed part. As a result of the design according to the present invention, the magnetic field of the turn parts of the coils is actively used. In this way, dispersion losses are reduced and a more efficient machine is provided. Also, you get a better heat transfer, specifically by means of the axial extensions of the fixed part that are joined to the return parts of the spirals, external to the winding grooves. In a further embodiment, the core and the winding constitute a stator assembly for a linear electric machine, the core of which has a fixed longitudinal part and a plurality of teeth spaced along the longitudinal fixed part, and whose spaces between the teeth define the grooves of the winding longitudinally spaced. This corresponds to the direction of movement, which goes along a direction x; the direction of the magnetic field along the direction y, and the direction of the different dimensions of each tooth and an adjacent part of the fixed part along a z-direction of a right-angle coordinate system. The improved efficiency can be used to increase the slot area and / or reduce the width of the fixed part. This means a possibility either to reduce the dimensions of the electric machine while maintaining the performance or to improve the performance while maintaining the dimensions.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an axial view of a stator of a servomotor according to the first embodiment of the invention.

Figure 2 is an axial view in sections along the lines ll-ll of Figure 1 and shows the axial profile of the fixed part and a core tooth of the stator according to the first embodiment of the invention. Figure 3 is an axial view of a stator of a universal motor according to the second embodiment of the invention. Figure 4 is an axial view in sections along the lines IV-IV of Figure 2 and shows the axial profile of a pole of the stator according to the second embodiment of the invention.

DESCRIPTION OF THE PREFERRED MODALITIES With reference to figures 1 and 2, a stator (1) of a servomotor is illustrated with a core consisting of a fixed part (2) and nine poles or teeth (3). Each tooth (3) and an adjacent part (4) of the fixed part (2) form a separate unit or segment (5). Each adjacent part (4) projects in the circumferential direction of both sides of its tooth (3), so that a groove (6) is formed on each side of each tooth (3). In addition, the inner end (7) of each tooth (3) widens in the circumferential directions, while the remainder of each tooth (3) has a substantially constant width. Assembling the stator (1) from the separate units (5) allows easy winding of each unit (5) of the stator.

The nine separate units (5) are made of a mixed material of soft magnetic powder, which is placed in a mold, pressed into a desired shape and then treated with heat at a relatively low temperature, so as not to destroy the Insulation layer needed between the dust particles. This means that the mass production of the separate units (5) is possible, which avoids the waste of material and results in a press unit finished with high tolerance and with little need or without the need for machine printing. As shown for a unit (5) in Figure 2, the axial length of each tooth (3) is smaller than the axial length of the adjacent part (4). This extension of the fixed part (2), which axially goes beyond the teeth (3) on both axial sides ther increases the active length of the windings and reduces the losses by dispersion, in such a way that an most efficient machine. In addition, the transfer of heat from the windings to the stator is improved by the axial extensions of the fixed part which are joined to the return parts of the spirals, external to the winding grooves. The design described above can be used to reduce the total winding length and, thus, reduce the dimensions of the electrical machine while maintaining performance. An additional advantage of using powder material is that the sectional profile of the tooth can be rounded or oval, in such a way that the sharp bending of the turns of the spirals is eliminated and the risk of penetration of the insulation in the corners. This allows the lighter insulation to be used, resulting in a substantial thermal benefit. The winding arrangement may consist of a non-superimposed winding on each tooth, which simplifies the winding operation and allows very high packing factors to be achieved. It should be noted that the rotor (not shown in FIGS. 1 and 2) of the servomotor is preferably of common laminate design with surface magnets, preferably with magnet tilt, to reduce roughing. With reference to Figures 3 and 4, a universal motor stator (11) according to the second embodiment of the invention is illustrated with a core consisting of a fixed part (12) and two poles or teeth (13). The rotor is common and is not illustrated. The core is formed from iron powder and molded in one piece. The shape of the core, as seen in Figure 3, is common, while the axial sectional shape (shown in Figure 4) of each of its poles (13) resembles the axial sectional shape of the teeth (3) of the stator of the servomotor exemplified in figure 2, in which the axial length of the fixed part (12) is greater than the axial length of the adjacent part of the poles (13). However, the inner ends (14) of the poles (13) of the stator of the universal motor (11) extend axially and are substantially of the same length as the fixed part (12). Thus, a low density of flow of Air gap is concentrated in a smaller armature winding and the stator iron volume is reduced. While in the preceding paragraphs only two embodiments of this invention are described, it is obvious to those skilled in the art that it is possible to carry out various modifications without departing from the essence of this invention. Therefore, the invention can be applied to other types of motors, for example, induction motors, synchronous reluctance motors, stepper motors and hybrid stepper motors, and to the corresponding types of generators, i.e., generally to machines rotating electric Also, the invention can be used in machines having an outer rotor instead of the exemplified inner rotor.

In addition, the material of the stator can be constituted by a powder material combined with other materials; for example, laminations, or the stator can be fabricated by casting. It should be noted that the teeth could even be axially longer than the ends of the teeth (and / or the fixed part); for example, to decrease the density of flow in the teeth and thus reduce the risk of magnetic saturation in them. Generally, it is intended to use in the invention a material or a combination of materials that allows to change the dimensions of each tooth and of the adjacent part of the fixed part substantially in a direction transverse to the plane of the laminations in an electric machine. common, in order to adjust the magnetic flux to an optimum flux density in each part of the course of the magnetic flux. In other words, each tooth and the adjacent part of the fixed part have different dimensions in said transverse direction; that is, they differ from a constant width. Finally, it should be emphasized that the invention is not limited to the specific embodiments described above, but that it is also applicable to electric machines that have other combinations of stationary and moving elements.

Claims (11)

NOVELTY OF THE INVENTION CLAIMS

1. - In an electric machine, the combination consists of a core made of a magnetic powder material, a fixed part (2, 12) and a plurality of teeth (3, 13) separated in a first direction along the fixed part and extending from there in a second direction substantially transverse to the first, defining the spaces between the teeth, the separate winding grooves (6), and a winding supported by the core, which has turns of coils around the teeth and in the winding slots; further characterized in that each tooth (3, 13) and an adjacent part (4) of the fixed part (2, 12) have different dimensions in a direction transverse to the plane defined by the first and the second direction to adjust the magnetic flux density in each part of the course of the magnetic flux in the nucleus and the fixed part.

2. The combination according to claim 1, further characterized in that the core and the winding constitute a stator assembly for a rotating electric machine, the core having a fixed annular part (2, 12) and a plurality of teeth (3). , 13) circumferentially spaced apart in the annular fixed part, and the spaces between the teeth circumferentially defining the separate winding grooves (6).

3. - The combination according to claim 2, further characterized in that the teeth (3, 13) extend radially from the fixed part (2, 12) and that each tooth and the adjacent part of the fixed part have different axial dimensions.

4. A stator assembly for an electric machine according to claim 3, further characterized in that the fixed annular part (2, 12) extends axially beyond the teeth (3, 13) in at least one of the axial sides thereof.

5. A stator assembly for an electric machine according to claim 3 or 4, further characterized in that the teeth (13) have ends (14) extending axially beyond the main part of the teeth.

6. The combination according to claim 2, further characterized in that the teeth extend axially from the fixed part and that each tooth and the adjacent part of the fixed part have different radial dimensions.

7. A stator assembly for an electric machine according to claim 6, further characterized in that the annular fixed part extends radially beyond the teeth on at least one of the radial sides thereof.

8. A stator assembly for an electric machine according to claim 6 or 7, further characterized in that the teeth have ends that extend radially beyond the main part of the teeth.

9. A stator assembly for an electric machine according to claim 1, further characterized in that the core and the winding constitute a stator assembly for a linear electric machine, wherein the core has a fixed longitudinal part and a plurality of teeth spaced apart along the longitudinal fixed part, and the spaces between the teeth longitudinally define the separate winding grooves.

10. A stator assembly for an electric machine according to any of claims 1 to 9, further characterized in that the teeth (3, 13) of the core have a rounded profile that eliminates the sharp bending of the turns of the spirals and reduces the risk of penetration of the insulation in the corners.

11. A stator assembly for an electric machine according to any of claims 1 to 10, further characterized in that the teeth (3) form a separate segment (5) with the adjacent part (4) of the fixed part (2). ).