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EP-4738660-A1 - ELECTRICAL MACHINE WITH BRIDGE-FRAMED STRUCTURES

EP4738660A1EP 4738660 A1EP4738660 A1EP 4738660A1EP-4738660-A1

Abstract

An electrical machine operating by switching of magnetic flux comprises a stationary member (10) and a movable member (11), arranged movable with respect of each other along a predetermined motion path (P). The stationary member and the movable member have each at least one side air-gap surface (14). The movable member and/or the stationary member comprises stacks (21) of sheet portions (20) of highly magnetically permeable material (40). Each of the sheet portions of highly magnetically permeable material has a main sheet extension with a normal (N) that is parallel to respective the side air-gap surface and is transverse to a direction of the predetermined motion path. The stacks of sheet portions of highly magnetically permeable material together form cavities extending transverse to the main sheet extension. Thereby a bridging section (23) of said highly magnetically permeable material is formed.

Inventors

  • HAGNESTÅL, Anders
  • ÅSTRÖM, Johan
  • KEIJSER, Mårten

Assignees

  • Hagnesia AB

Dates

Publication Date
20260506
Application Date
20241029

Claims (15)

  1. An electrical machine (1), being a machine operating by switching of magnetic flux (5), comprising: - a stationary member (10) having at least one side air-gap surface (14); wherein said stationary member (10) has at least one stationary member section (12); and - a movable member (11) having at least one side air-gap surface (14); wherein said movable member (11) has at least one movable member section (13); wherein said movable member (11) is movable relative to said stationary member (10) along a predetermined motion path (P), rotational or linear, parallel to said side air-gap surfaces (14) of stationary member (10) and movable member (11); wherein said side air-gap surface (14) of said movable member (11) and said side air-gap surface (14) of said stationary member (10) being separated by an air-gap (15); wherein at least one of said movable member (11) and said stationary member (10) comprises stacks (21) of sheet portions (20) of highly magnetically permeable material (40); wherein each of said sheet portions (21) of highly magnetically permeable material (40) has a main sheet extension with a normal (N) that is parallel to respective said side air-gap surface (14) and is transverse to a direction of said predetermined motion path (P); and wherein each of said sheet portions (20) have cut-out areas (22), wherein said cut-out areas (22) in said stacks (21) of sheet portions (20) of highly magnetically permeable material (40) together form cavities (24) extending transverse to said main sheet extension, forming a bridging section (23) of said highly magnetically permeable material (40) passing said cavities (24) in said direction of said predetermined motion path (P).
  2. The electrical machine according to claim 1, characterized in that said cavities (24) are apertures (25) extending transverse to said main sheet extension, wherein said bridging section (23) of said highly magnetically permeable material (40) separates said aperture (25) and respective said side air-gap surface (14); wherein said electrical machine (1) further comprises permanent magnets (30) inserted into said apertures (25), whereby said electrical machine (1) is a modulated pole machine.
  3. The electrical machine according to claim 2, characterized in that said permanent magnets (30) are electrically insulated with respect to said stacks (21) of sheet portions (20) of said highly magnetically permeable material (40).
  4. The electrical machine according to claim 1, characterized in that said cavities (24) form recesses (26) in said side air-gap surface (14) transverse to said main sheet extension, wherein said bridging section (23) is positioned at a non-zero distance from said side air-gap surface (14), whereby said electrical machine (1) is a switched reluctance machine.
  5. The electrical machine according to claim 4, characterized by having non-magnetic material inserted into said recesses (26).
  6. The electrical machine according to any of the claims 1 to 5, characterized in that said bridging section (23) has a width (W) measured perpendicular to respective said side air-gap surface (14) that is less than 1/10, preferably less than 1/20, of an extension (D; D1,D2) of said cavities (22) perpendicular to respective said side air-gap surface (14).
  7. The electrical machine according to any of the claims 1 to 6, characterized in that said sheet portions (20) of highly magnetically permeable material (40) in said stacks (21) of sheet portions (20) of highly magnetically permeable material (40) are attached to each other by adhesive material (41).
  8. The electrical machine according to any of the claims 1 to 7, characterized in that said movable member (11) has a plurality of movable member sections (13) and said stationary member (10) has a plurality of stationary member sections (12), wherein said plurality of stationary member sections (12) and said plurality of movable member sections (13) are interleaved in a direction perpendicular to side air-gap surfaces (14) with a respective air-gap (15) between pairs of said side air-gap surfaces (14) of said movable member sections (13) and said side air-gap surfaces (14) of said stationary member sections (12).
  9. The electrical machine according to claim 8, characterized in that at least one of said plurality of stationary member sections (12) and said plurality of movable member sections (13) is a disc having air-gaps (15) on both sides, wherein both sides are facing a respective one of said plurality of movable member sections (13) and said plurality of stationary member sections (12), respectively.
  10. The electrical machine according to any of the claims 1 to 9, characterized in that said highly magnetically permeable material (40) being defined as materials having a relative magnetic permeability of more than 50 at a magnetic flux density of more than 0.2 Tesla.
  11. The electrical machine according to any of the claims 1 to 10, characterized in that said stacks (21) of sheet portions (20) of said at least one of said movable member (11) and said stationary member (10) comprising stacks (21) of sheet portions (20) defining at least one recess (45) in said air-gap surface (14), wherein said at least one recess (45) is used as a part of a fluid bearing arrangement.
  12. A method for manufacturing at least one of a movable member (11) and a stationary member (10) of an electrical machine (1), comprising the steps of: - providing (S10) a sheet of a highly magnetically permeable material (40); - creating (S12) cut-out areas (22) in said sheet of said highly magnetically permeable material (40); - separating (S14) said sheet of said highly magnetically permeable material (40) into sheet portions (20); - stacking (S16) said sheet portions (20) in a direction perpendicular to a main sheet extension of respective sheet portions (20), forming a stack (21) of sheet portions (20); wherein said step of stacking (S16) comprises adapting a relative lateral position of said sheet portions (20) for aligning said cut-out areas (22) of respective said sheet portions (20) for forming cavities (24) extending transverse to said main sheet extension; and - adhering (S20) said sheet portions (20) to each other, thereby forming said at least one of a movable member (11) and a stationary member (10) of an electrical machine (1), whereby edges of said sheet portions (20) together form a side air-gap surface (14) that is parallel to a normal (N) of said main sheet extension; wherein said stacks (21) of sheet portions (20) of highly magnetically permeable material (40) forming a bridging section (23) of said highly magnetically permeable material (40) passing said cavities (24) in a direction of a predetermined motion path (P).
  13. The method according to claim 12, characterized in that said highly magnetically permeable material (40) has an adhesive coating (41), whereby said step of adhering (S20) in turn comprises the part steps of: - fixating (S22) said stack (21) of sheet portions (20); and - heating (S24) said stack (21) of sheet portions (20), causing a cross-linking between said adhesive coating (41) of neighbouring sheet portions (20) in said stack (21) of sheet portions (20).
  14. A method for manufacturing an electrical machine (1), comprising the steps of: - providing (S1) a movable member (11); - providing (S2) a stationary member (10); wherein at least one of said steps (S1, S2) of providing a movable member (11) and providing a stationary member (10) is performed (S3) according to any of the claims 11 to 16; - mounting (S4) said movable member (11) movable relative to said stationary member (10) along a predetermined motion path (P), rotational or linear, parallel to said side air-gap surfaces (14) of stationary member (10) and movable member (11); wherein said side air-gap surface (14) of said movable member (11) and said side air-gap surface (14) of said stationary member (10) being separated by an air-gap (15).
  15. The method according to 14, characterized in that said movable member (11) has a plurality of movable member sections (13) and said stationary member (10) has a plurality of stationary member sections (12), wherein said step of mounting (S4) comprises mounting said movable member (10) relative to said stationary member (11) by interleaving said stationary member sections (12) and said movable member sections (13) in a direction perpendicular to side air-gap surfaces (14) with a respective air-gap (15) between pairs of said side air-gap surfaces (14) of said movable member sections (13) and said side air-gap surfaces (14) of said stationary member sections (12).

Description

TECHNICAL FIELD The present technology relates in general to electrical machines, and in particular to electrical machines presenting varying magnetic permeability or permanent magnets along an air-gap surface, and manufacturing methods therefore. BACKGROUND The concept of electrical machines is well known and the first types of electrical machines such as the induction machine and the synchronous machine that were invented in the late 19:th century are still very important in the industry today. Electric machines generally comprise one movable part, typically but not restricted to a rotor or a translator, and a second part, typically but not restricted to a stator. These parts are separated by an airgap, which separates the movable part and the second part. At least one of the parts, typically a stator, also has an electric winding which can carry an electric current. Characterizing for electric machines is that they have low force or torque densities compared to mechanical systems such as gear boxes, hydraulic systems and pneumatic systems, but has high power densities since they can operate at high speed. A power density of 1 kW/kg is a representative number for an electric motor. Characterizing for most electrical machines is also that the resistive power losses, which often constitute the majority of the losses in the electric machine, are independent on the airgap speed v if the eddy currents in the winding are neglected. However, counted in percent of the total power, the resistive power losses become proportional to 1/v since the total power is proportional to v. Thereby, general electric machines typically have high efficiencies at high speeds at the airgap in the range 10-100 m/s, where efficiencies in the range of 90-98% are common. At low speeds at the airgap, e.g. below 5 m/s, electrical machines typically have lower efficiencies. Also, the resistive losses typically create a thermal problem in the electric machine, and limit the torque and force density as well as the power density for operations longer than a few seconds. To get around the low speed efficiency problem and the low force density problem, a number of different machine types belonging to the family of machines known as variable reluctance machines (VRM) and especially variable reluctance permanent magnet machines (VRPM) has been proposed and developed. These machine types have different and overlapping designations, for example the Vernier machine (VM), the Vernier hybrid machine (VHM), modulated pole machines (MPM) and different variants of transverse flux machines (TFM). Generally, they implement a geometrical effect known as magnetic gearing, which lowers the winding resistance grossly by making the winding shorter and thicker. This is accomplished by arranging the geometry so that the flux from several adjacent poles goes in the same direction and so that the flux from these poles switches direction when the movable part, i.e. translator or rotor, is moved one pole length. These machines also typically develop a higher shear stress than other machines, where shear stress is defined as the useful shear force per unit airgap area. They, however, do not in general increase the amount of airgap area packed in per unit volume much compared to standard machines, so although the force density of these machines is increased, it is only moderately. A well-known problem with these machine types is that the leakage magnetic flux becomes large, and that the power factor becomes low at full load. Thereby, they cannot both have a high power factor and a very high shear stress. Although they have been proposed for e.g. wind power, they have not reached a wide-spread market penetration due to these drawbacks. A specialized type of VRM is presented in the published US patent US 11,728,717 B2 and a specialized type of VRPM machine which is now called the poloidal or tangential flux machine (PTF) machine is presented in the published US patent applications US 2023/0353025 A1, US 2023/0268815 A1 and US 2023/0275481 A1. These machine types have the advantage that they do pack in considerable airgap area per unit volume and thereby accomplishes a very high force or torque density. However, they are very difficult to build, and both the specialized type of VRM and the PTF are double-sided in design with airgaps on both sides of thin sections and have many small blocks of permeable material interleaved with other materials along the movement direction. For the PTF, the preferred double-sided flux-concentrating structure that contain the permanent magnets is built up from interleaved sections of permanent magnets and permeable material, typically electrical steel, along the movement direction. Such a construction does not become robust and mechanically reliable. For the specialized VRM, it is also difficult to find a robust and reliable construction. The machine types also have small airgaps and require precise manufacturing and assembly tolerances i