Magnetic core of end-face electric machine

Abstract

FIELD: electrical engineering.SUBSTANCE: magnetic circuit of the end electric machine comprises a ferromagnetic yoke and teeth. The magnetic circuit plates are circular in shape and cut from electrical steel. Three-sided notches were made on the magnetic circuit plates and the cut teeth were bent at an angle of 90 degrees to the plate surface, forming the toothed zone of the magnetic system. Said plates are annealed and then assembled into a laminated magnetic core package, in which the function of the yoke is performed by the flat sections of the plate located on both sides of the teeth.EFFECT: increase in the energy efficiency of end-face electric machines.2 cl, 4 dwg

Description

[0001] The invention relates to the field of electrical engineering, namely to the technology of manufacturing laminated magnetic cores of end-face electric machines, and can be used in electrical engineering.

[0002] Currently, the development of electric end-milling machines has seen significant advances. Compared to cylindrical machines, end-milling machines can be used in a wide range of applications due to their easy integration and the required size ratios for certain designs, such as electric pumping equipment, space technology, and alternative energy. Research conducted in the development of end-milling machines has shown that the specific material consumption and energy performance of end-milling and axial machines are roughly equivalent.

[0003] When creating end-milling machines, one of the key elements is the development of a design and a corresponding manufacturing technology for the magnetic core. Currently, the following main designs of end-milling machine magnetic cores are known: wound, solid, and composite.

[0004] Twisted magnetic cores are structures using flat-wound electrical steel tape, in which slots for winding placement are cut beforehand or during the winding process. The twisted magnetic core design provides a magnetic system consisting of insulated turns, which facilitates the implementation of a method for reducing eddy current losses in a laminated core. The invention "Magnetic Core of an End-Facing Electrical Machine" [1] can be noted as an analog. A disadvantage of the twisted design is the difficulty of cutting slots on each turn of the twisted magnetic core, since it is necessary to account for the change in the circumference diameter on each turn.

[0005] A known design of magnetic core for an end-face electric machine involves initially winding a ferromagnetic tape flat. Slots for the winding are formed by removing sections of the wound magnetic core [2]. Milling or electrical discharge machining is used for this purpose. A disadvantage of this design is the deterioration of the magnetic properties of the tape as a result of the mechanical processing of the tape during slot formation, as well as the need for specialized tooling and equipment for the slot formation process. This leads to an increase in the cost of the electric machine using this magnetic core design.

[0006] A design for a magnetic core for an end-face electric machine based on powder technology is known [3]. Ferromagnetic powders with fillers are used as materials. The tooth-slot zone is formed using special technological molds. The use of powder technology allows for a reduction in material consumption and the use of powders with improved material properties. However, the design development and organization of production of powder cores requires significant material costs. The designs of massive magnetic cores are homogeneous, unlaminated packages obtained by machining blanks from ferromagnetic alloys, or magnetic cores in which ferromagnetic powders are used. The designs of massive magnetic cores are characterized by increased eddy current and hysteresis losses compared to twisted magnetic cores.The effect of increasing magnetic losses is significantly manifested in high-speed electric machines.

[0007] A magnetic core design is known that is quite close to the design of a powder magnetic core, developed using additive technologies [4]. The use of 3D metal printers allows for the production of fairly complex magnetic core designs based on the geometry of the magnetic system.

[0008] A disadvantage of this design is the need for post-processing of 3D-printed parts. The magnetic core is unlaminated, which reduces the magnetic properties of the core. Using this magnetic core design necessitates the use of expensive 3D printers and materials.

[0009] Composite magnetic core designs for end-face machines are prefabricated structures in which the yoke is a flat-wound ferromagnetic strip, and the teeth are formed by laminating rectangular ferromagnetic plates. The design involves connecting the yoke and teeth using adhesive or screws.

[0010] The closest invention to the claimed invention in its technical essence and achievable technical result, and adopted by the author as a prototype, is the invention of a laminated magnetic core for an end-face electric machine, consisting of a twisted yoke and a corrugated tooth-and-slot zone [5]. The presence of a laminated magnetic system allows for a significant reduction in magnetic losses due to eddy currents. Flat winding of the tape to form the core yoke and the manufacture of teeth from a corrugated ferromagnetic sheet ensures significant steel savings in the proposed, virtually waste-free magnetic core design.

[0011] The invention considered as a prototype solves the problems of ensuring:

[0012] - high energy performance of the end electric machine due to the production of a laminated core from electrical steel with restored magnetic properties, the reduction of which occurs as a result of mechanical processing of the steel;

[0013] - implementation of a low-waste and waste-free technological process in relation to the proposed design of the magnetic system.

[0014] However, the use of a composite core structure consisting of a twisted yoke and a corrugated tooth zone results in the formation of an air gap, which reduces the magnetic properties of the magnetic circuit. Ensuring reliable attachment of the teeth to the yoke is also quite difficult, which complicates the manufacturing process and increases production costs.

[0015] The technical result of the invention proposed by the author consists in the creation of a new design of a laminated magnetic circuit of an end machine assembled from plates of electrical steel.

[0016] The technical result is achieved by assembling the core stack from electrical steel plates cut from coiled or sheet electrical steel. Three-sided notches are made on the ferromagnetic sheet before (or simultaneously with) cutting the plate into a circular shape, and the notched sections are bent at a 90-degree angle to the plate surface (Fig. 1). The assembled stack of plates forms the laminated magnetic circuit of an end-face electric machine (Fig. 2).

[0017] Magnetic flux closure occurs along the laminated sections of the core's magnetic system without overcoming parasitic gaps, as occurs in a composite core design. Flux lines are closed along the laminated teeth (Фz), formed by the bent sections and two laminated yokes located on either side of the teeth (Fig. 3). The magnetic flux in the yoke is formed by fluxes (1 / 2 Фя), closure on both sides relative to the teeth. This core design allows for a significant reduction in overall size (core thickness) compared to a twisted design, which is in demand in a number of technical devices.

[0018] Compared with the existing designs of general industrial machines of cylindrical and end designs, the proposed design of the magnetic circuit does not cut out grooves, but rather teeth, which are formed as a result of bending the cut out sections.

[0019] The bend line of the cut-out sections can be directed along the radius of the circle. In this case, after lamination, the teeth will be straight, i.e., the core design will be without slot beveling (Fig. 4a). If the bend line is offset relative to the radius, the teeth will be beveled after lamination (Fig. 4b). Thus, the proposed invention implements slot beveling. The laminated magnetic circuit design, in which slot beveling is used, reduces higher harmonics in the electromagnetic field and improves the energy performance of the end-face electric machine compared to a design without slot beveling. Moreover, unlike a cylindrical design, beveling is achieved without complicating the technological process of implementing the bevel.

[0020] The punched magnetic core laminations are annealed. Note that this design eliminates the need for specially manufactured furnaces, which would require additional costs during the production setup, as is necessary for twisted core designs when winding long strips with pre-punched grooves.

[0021] After annealing, the plates are assembled into a stack. To increase the fill factor of the stack with steel, the assembled plates are pressed. To prevent fluffing, the stack is secured using welding along the outside diameter, clamps, or screws with holes cut into the plates.

[0022] When using a single die for punching notches, after stack lamination, the core's tooth area consists of bent sections that differ in height by the thickness of the ferromagnetic sheet. Therefore, grinding the surface of the laminated magnetic core's teeth is necessary to ensure a uniform air gap in the end-face machine. Grinding can be eliminated by using multiple dies of different geometries, ensuring that the notches are punched so that the heights of the plates forming the tooth are consistent.

[0023] A key feature of the proposed magnetic circuit design is that the formation of rectangular or trapezoidal holes in the core (Fig. 2), created by bending sections, effectively cools the winding during operation of the end-milling machine. The shape of the holes is determined by the chamfering or non-chamfering of the slots in the laminated magnetic circuit.

[0024] BIBLIOGRAPHY

[0025] 1. A.s. 788224 Magnetic circuit of an end-face electric machine. / A.A. Stavinsky, V.A. Grishin, et al. - 3 p.

[0026] 2. Ignatov V.A., Vildanov K.Ya. End-face asynchronous electric motors of integral manufacture. Moscow: Energoatomizdat 1988, 304 p.

[0027] 3. A.s. 485524 Magnetic circuit of the stator of an end-face electric micromachine made of a hardenable magnetodielectric material. / Koritsky A.V., Ignatov V.A. et al. - 3 p.

[0028] 4. Lamichhane T.N., Sethuraman L., Dalagan A., Wang H., Keller J., Paranthaman MP, Additive manufacturing of soft magnets for electrical machines - a review, Materials Today Physics 15 (2020).

[0029] 5. Ac 855864 Magnetic circuit of the stator of an end electric machine. / Khait Ya.M., Petrov V.M. et al. - 3 p.

Claims

1. A magnetic circuit for an end-face electric machine containing a ferromagnetic yoke and teeth, characterized in that the plates of the magnetic circuit are cut out of electrical steel in the shape of a circle, three-sided notches are made on the plates, and the cut out teeth are bent at an angle of 90 degrees to the surface of the plate, forming the tooth zone of the magnetic system, wherein said plates are subjected to annealing and then assembled into a laminated magnetic circuit package, in which the function of the yoke is performed by flat sections of the plate, located on both sides of the teeth.

2. The magnetic circuit of an end-face electric machine according to paragraph 1, characterized in that the bending line is shifted relative to the radius to ensure beveling of the grooves.

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