MX2008002719A - A device and method to clamp and lock permanent magnets and improve cooling within a rotating electrical machine - Google Patents

Abstract

A device to hold at least one magnetic flux producing permanent magnet onto a surface of an electrical machine comprising at least one slot recessed from the surface and extending from one end of the surface;and at least one gripping bar inserted into an associated at least one slot having a protrusion extending past the surface to engage at least one magnet where at least one slot and at least one gripping bar are shaped to retain the at least one gripping bar within the associated at least one slot to hold the at least one engaged magnet onto the surface.

Description

DEVICE AND METHOD FOR ATTACHING AND LOCKING PERMANENT MAGNETS AND IMPROVING COOLING WITHIN A ROTATING ELECTRICAL MACHINE BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates in general to devices and methods for assembling electric machines of permanent magnets and more particularly to an apparatus and a method for mounting the magnets within the rotor of the machine.

GENERAL BACKGROUND AND PREVIOUS TECHNIQUE Permanent magnets make it reasonable to build electric machines (defined here as motors and generators) using, instead of electromagnets, to generate fields. Typically, the magnets are mounted on an internal rotor, but the assembly on external rotors is also used. In a generator, rotations of the magnetic fields of the magnets on the rotor induce voltages and currents in the stator radially outward. In an engine, the magnets react the voltages and currents applied to the stator and cause the rotation of the rotor.

Permanent magnet electric machines are more compact and simpler and require less maintenance than their electromagnetic companions, because they do not require windings of electromagnets. Modern rare earth magnets provide a much denser source of powerful magnetic flux than windings and have a high flux and are capable of withstanding reasonably high temperatures. The resulting compact machines find application in structures, in which size, weight and efficiency are important, such as generators within the gondolas of wind power generators located above tall towers, or in engines in which the space is a profit Permanent shafts are mounted in the so-called surface mount configuration on the rotor surface, where their poles are radially and axially oriented. One of the manufacturing issues related to permanent magnet machines is the assembly of the magnets in the rotor. Conventionally, the surface mount magnets are mounted by adhering them to the surface of the rotor. Although the adhesive is typically an epoxy, this alone is often inadequate, given the powerful magnetic attraction of the magnets to the stator's pharmaceutical material, which is separated from them only by a tiny air gap. The rotor assembly becomes even more difficult, given the centripetal forces on the magnets, due to the rotation of the rotor; which is true in normal operation, but especially during excessive speed. In the case of manes mounted on the rotor, the crimping is also used with a non-ferrous material (such as fiberglass, carbon fiber or kevlar tape), in which the tape is wound tightly around the circumference of the adhered shapes and then cured by hot. A more reliable means for mounting magnets mounted on surfaces within electrical machines is necessary and is the topic of this invention.

BRIEF DESCRIPTION OF THE INVENTION Accordingly, it is an object of the present invention to provide a method and a device for holding and locking permanent magnets to the rotor surface of an electrical machine. The cooling of electric machines is always a matter of consideration and a further object of the present invention is to provide a means for cooling the rotor. Further objects and advantages of the present invention will become more apparent for the following description of the preferred embodiments, which, taken in conjunction with the adjacent drawings, will illustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing objects, aspects and advantages and others will be better understood with the following detailed description of the preferred embodiments of the invention with reference to the drawings, in which: Figure 1 illustrates the rotor of an electric machine with the magnets adhered to its external surface; Figure 2 illustrates the rotor and stator of an electric machine in cross section, with the magnets adhered to the rotor surface and also locked in place with grab bars in the form of beams? ", mounted in axial grooves in the structure of the rotor, the heat transfer and cooling provided by the grab bar is also illustrated, Figure 3 illustrates the rotor and stator of an electric machine in fragmentary cross section, with the magnets adhered to the rotor surface and also blocked instead, by gripping bars in the form of "I" beams mounted in axial grooves in the rotor structure, using a step on each magnet, the heat transfer and cooling provided by the grab bars is also illustrated; 4 illustrates the rotor of an electric machine in fragmentary cross-section with the magnets adhered to the rotor surface and also locked in place by a rod grip in the form of double dovetail, mounted in an axial groove in the rotor structure, using Manes that have matching surfaces; the heat transfer and cooling provided by the grab bar is also illustrated; Figure 5 illustrates the rotor of an electrical machine in fragmentary cross-section with a grip bar in the form of a "" at the moment of being installed hot and expanded, and then it cools and contracts to block the adjacent magnets; Figure 6 illustrates the application of surface-mounted magnets, showing the use of non-ferromagnetic grip bars, Figure 7 illustrates one of many slots in a cast or machined rotor, Figure 8 illustrates one of many slot delineations perforated on the laminations of a laminated rotor, Fig. 9 illustrates one of many slot delineations perforated on laminated rotor laminations and air gaps between selected laminations at given intervals, Fig. 10 illustrates a fragmentary cross section of a ventilated rotor in an air gap. ventilation, figure 11 illustrates a ventilated rotor with two circular rows of permanent magnets supported by b gripper with ventilation hole sucking cooling air from a central plenum and having the air gaps between the circular rows of the permanent magnets; Y Figure 12 illustrates a ventilated rotor and stator with air gaps at given intervals.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES OF THE INVENTION In the following description of the present invention, reference is made to the accompanying drawings, which form a part thereof and in which exemplary embodiments illustrating the principles of the present invention and how they can be shown are shown by way of illustration. put into practice. It is to be understood that other embodiments may be used to practice the present invention and that structural and functional changes may be made thereto without departing from the scope of the present invention.

General Assembly of the Magnets As illustrated in the figure, the conventional way of fixing the permanent magnets 1 is simply to adhere them to the surface 2 of the rotor 3 using adhesive 4. The shaft 5 that provides the rotation of the rotor 3 is also shown. The best method, the topic of this invention, is illustrated in Figure 2, in which a grip bar 10 is locked inside the rotor core 17 and connected to the magnets 1. The grab bar 10 has, for example, a beam-shaped cross section? "And is as long as the rotor 3 with the lower portion? "sliding into an internal groove 11 of similar shape, formed inside the rotor core 17, from which the rotor core 17 and the other end of the grip bar 10 overlap two adjacent magnets 1 and hold them therein firmly on the rotor surface 2. The magnets 1 adhere to the surface 2 simply as an assembly step to hold them in place for the installation of the gripper bars and the rotor crimping is not required. simple curved shapes conforming to the surface of the rotor 2 and the grip bar 10 simply overlaps the external radial surface of magnet 16. The grip bar 10 is necessarily closer to the stator 13 than the magnets 1 and in the air gap 15 between the rotor 3 and the stator 13. The extension of the gripper rod 10 towards the rotor core 17 provides a cooling path 14, by which it is transferred outwards from the surrounding magnets 1 and the core 17. In an alternative embodiment, illustrated in FIG. 3, the shape of the magnet 1 includes a step 20 for accentuating the grip bar 10 that is farther from the stator 13 than the magnet 1. In a further embodiment, illustrated in Figure 4, the grip bar 10 has a double dovetail cross section 30, in which the magnet 1 and the slot 11 have matching surfaces 31. In a further embodiment, the grip bar 10 has a Cross section in the form of a combination of the? "and the dovetail.

Preferably, the magnets 1 are adhered in place and the gripper rod 10 is heated, and thus expanded, and then inserted into the slot 1, while still hot. As illustrated in Figure 5, the heated grip bar 40 expands and does not hold the magnet 1, but the grip bar 41 contracts and forms a tight grip between the radially outward surface 42 of the slot 11 and the surfaces radially outer magnet 16. As illustrated in Figure 6, the surface-mounted magnets have radial powders 71 and, to maintain the desired radial magnetic flux 70 emanating from the poles 71, a non-ferromagnetic grab bar 72 must be made of non-ferromagnetic material so as not to interfere with the normal 70 magnet flow path. The material is aluminum, stainless steel, carbon fiber, highlighted fiberglass or any other non-magnetic material. The rotor 3 is made of fused ferrous metal or is formed by laminated sections that reduce eddy currents. As illustrated in Figure 7, for a molten rotor 50 the casting mold provides the internal grooves 11 for embedding the gripper 10. Alternatively, the grooves 11 are machined or cut. As illustrated in Figure 8, for a laminated rotor 60 the cross section of the groove 11 is punched on each lamination 61 and the entire groove 11 is formed when the laminations 61 adhere to each other.

As illustrated in Figure 9, for a ventilated rolled rotor 80 with air gaps 73 the cross section of the groove 11 is punched on each lamination 61 and the entire groove 11 is formed when the laminations 61 adhere to each other. At given intervals in the laminations there is a ventilation gap 73 which allows the air to flow from the shaft plenum 74 radially outwardly. The lamination 61 adjacent to each air gap 73 is supported by spacer rods 18 which are mounted radially between the selected laminations. As illustrated in Figure 10, the cooling air 14 flows along the rotor shaft 5 and from the shaft plenum 74 radially outwardly through the rotor core, parallel to the separator rods 18 and through the grip bars 10. As illustrated in Figure 11, with this configuration the gripping rods 10 in rotation protrude towards the air gap between the magnets and act as fans to move air 4 into the air surrounding the rotor (the air gap). 5) and facilitating the cooling of the rotor. The air gaps 73 are typically placed between the gaps between the magnets 1 spaced apart longitudinally to prevent circumferentially spaced gripping bars 10 from blocking the flow entirely. As illustrated in FIG. 12, the rotor is internally vented with the air gaps 73 which conduct the cooling air 14 of the shaft impeller chamber 74 radially outwardly through the air. rotor core 3 to air gap 15. Ventilation air gaps 73 are also made in stator 13 to allow air flow 14 to help remove heat from stator 13 and stator windings 6.

Alternative Modalities Although several illustrative embodiments of the invention have been shown and described, numerous variations and alternative modalities will occur to those skilled in the art. For example, the magnets are mounted to the stator surface instead of the rotor, and the grab bar and slot are applicable to the stator; the rotor may be an external rotor that rotates around an armature; and the grip bar has different forms of "I" dovetail, for example, bar with weights with curved surfaces. Such variations and alternative modalities, as well as others, are contemplated and may be realized without departing from the spirit and scope of the invention, as defined in the appended claims.

Claims (22)

1. NOVELTY OF THE INVENTION CLAIMS 1. - A device for supporting at least one permanent magnetic flux producing magnet on a surface of an electrical machine, comprising: a) at least one slot recessed from the surface and extending from one end of the surface; and b) at least one grip bar inserted into at least one associated slot having a shoulder extending beyond the surface to be joined with at least one magnet, wherein at least one slot and at least one slot The gripper bars are shaped to retain the at least one gripper bar within the at least one associated slot to hold at least one magnet spliced on the surface.
2. 2. The device according to claim 1, further characterized in that the at least one grab bar is inserted into the at least one associated bar, while heating and expanding, and holding at least one bar of gripping within the at least one associated slot and spliced with at least one magnet, when the at least one grip bar cools and contracts.
3. 3. The device according to claim 1, further characterized in that it additionally comprises an adhesive applied between the at least one magnet and the surface to hold more the at least one magnet to the surface.
4. 4. The device according to claim 1, further characterized in that the at least one grip bar is additionally formed of non-ferromagnetic material so as not to interfere with the magnetic flux of the at least one magnet. 5. - The device according to claim 1, further characterized in that the shoulder of the grab bar additionally has beam-like shape? "6. The device according to claim 1, further characterized in that the magnet has additionally shaped of step to be connected to the shoulder of the grab bar 7. - The device according to claim 1, further characterized in that the shoulder of the grab bar additionally has the shape of a dovetail. with claim 7, further characterized in that the magnet is additionally formed with an inclined side for splicing with the grab bar shoulder 9. The device according to claim 1, further characterized in that it additionally provides a heat removal path. of the volume surrounding the gripper 10. - The device according to claim 9, characterized also because that volume is vented to drive air from cooling and said heat removal path comprises the movement of air generated by the rotating grip bar. 11. An electric machine, comprising: a) a rotor and a surrounding stator, the rotor having a central axis; b) at least one permanent magnet that produces a magnetic flux; c) a surface selected from the group consisting of the rotor surface furthest from the axis and the stator surface closest to the axis; d) at least one gripping device for holding at least one magnet on the surface comprising: i) a slot recessed from the surface and extending from one end of the surface; ii) a grip bar inserted into the groove and extending beyond the surface to engage at least one magnet; wherein the grip bar and the slot are shaped such that the grip bar is retained within the slot and the at least one spliced magnet is held on the surface. 12. The machine according to claim 11, further characterized in that it additionally comprises an adhesive applied between the at least one magnet and the surface to additionally support at least one magnet on the surface. 13. The machine according to claim 11, further characterized in that the at least one grip bar is additionally formed of a non-ferromagnetic material so as not to interfere with the magnetic flux of at least one magnet. 14. - The machine according to claim 11, further characterized in that the shoulder of the grab bar additionally has the shape of a beam T. 15. The machine according to claim 11, further characterized in that the magnet has the shape of a step to be joined. with the shoulder of the grab bar. 16. - The machine according to claim 11, further characterized in that the shoulder of the grab bar additionally has the shape of a dovetail. 17. The machine according to claim 16, further characterized in that the magnet is additionally formed by an inclined side to be connected to the gripper bar. 18. - The machine according to claim 11, further characterized in that the gripping shoulder further provides a path of heat removal of the volume surrounding the groove. 19. - The machine according to claim 18, further characterized in that said volume is ventilated with air gaps to conduct cooling air and said heat removal path comprises the movement of air generated by the grab bar in rotation. 20. A method for supporting at least one permanent magnet on a surface of an electric machine, comprising the steps: a) forming a slot recessed from the surface and beginning at one end of the surface; b) forming a shaped grip bar for fit within the groove with the shapes of the grab bar and groove chosen to retain the grab bar within the groove, while the grab bar protrudes beyond the surface, and splices and holds the at least one magnet on the surface; and c) inserting the grip bar into the slot, while splicing with the at least one magnet. 21. The method according to claim 20, further characterized in that the gripping bar is additionally inserted into the groove, while the groove is hot and expanded and, when it cools and contracts, the groove holds the at least one magnet against the surface. 22. The method according to claim 20, further characterized in that the surface is further rotated and ventilated centrally to let in cooling air and the gripper bar acts as a fan to move the air and increase the cooling.