Permanent excitation electric machine, simulation method, computer system and computer program product

Abstract

The invention relates to a permanently excited electric machine (PDM) having a stator (STT) and a rotor (RTR) mounted so as to be rotatable about a longitudinal axis (X), the stator (STT) having a winding system (WND), a permanent magnet (PMG) being arranged on the rotor (RTR), the magnetic material of the permanent magnet (PMG) having a preferential direction (PFD) for magnetization, the rotor (RTR) and the stator (STT) are arranged such that paths through the permanent magnets (PMG) can be defined in the direction of a local priority direction (PFD), a magnet dimension (MTH) in the priority direction (PFD) associated with a point on the pole face (PAR) being defined as a path length from the point along the priority direction (PFD) through the permanent magnets (PMG) to a corresponding point on the further pole face, a gap (RGP) being formed between the rotor (RTR) and the stator (STT), the winding system (WND) is designed and arranged in such a way that the winding system interacts electromagnetically with the permanent magnets (PMG) of the rotor (RTR) via the gaps (RGP). In order to increase the dynamic performance while saving rare magnetic materials, it is proposed that the permanent magnets (PMG) are designed as CeFeB-based magnets, the permanent magnets extending at least partially along the longitudinal axis (X) being designed and arranged in such a way that the permanent magnets (PMG) have a north pole and a south pole on the side facing the gap (RGP), the magnet size (MTH) in the preferential direction (PFD) is between 1 / 10 and 1 / 3 of the rotor diameter there starting from the center of area of the north pole.

Description

Technical Field

[0001] The invention relates to a permanently excited electric machine, in particular a motor, having a stator and a rotor mounted so as to be rotatable about a longitudinal axis, wherein the stator has a winding system, wherein permanent magnets are arranged on the rotor, wherein the magnetic material of the permanent magnets has a preferred direction for magnetization, so that the path through the permanent magnets can be defined in the direction of the local preferred direction, wherein the magnet size in the preferred direction associated with a point on a pole face is defined as the path length from this point through the permanent magnet in the preferred direction to a corresponding point on another pole face, wherein a gap is formed between the rotor and the stator, wherein the winding system is designed and arranged so that it interacts electromagnetically with the permanent magnets of the rotor via the gap. Background Art

[0002] From US 2004 / 150283 A1 a permanent magnet electric motor is known having a stator and a rotor, a winding system and permanent magnets on the rotor, wherein the permanent magnets on the rotor have a north pole and a south pole on the side facing the air gap.

[0003] A permanently excited electric machine of the aforementioned type is known from WO 2006 / 064589 A1.

[0004] It is already known from DE 10 2012 211960 A1 to form permanent magnets based on CeFeB. In the same case, this is also known from the publication of Siemens AG: "Particularly fine-grained, sustainable permanent magnets for motor and generator applications, PRIOR ART PUBLISHING GMBH, PRIOR ART PUBLISHING GMBH, MANFRED-VON-RICHTHOFEN-STR. 9, 12101 BERLIN GERMANY, Journal of Prior Art, Vol. 2022, No. 12, June 15, 2022 (2022-06-15), pp. 41-43, XP007024723."

[0005] From JP 5 860654 B2 it is already known to provide an electric machine having a rotor with permanent magnets which each have a north pole and a south pole on the side facing the gap.

[0006] Background knowledge about electric machines with permanent magnet rotors can be extracted from JP 2018 038162A.

[0007] In the case of permanently excited electric machines or PM motors, the dynamics are influenced by many factors. In addition to the actual polar moment of inertia, the thermally permissible torque, the electrical time constant, the torque limitation caused by the motor voltage and the saturation behavior of the magnetic circuit also have a limiting effect.

[0008] The resulting dynamics are usually a design compromise between small magnet volume and material cost. The dynamic behavior of the motor can be achieved by using expensive neodymium iron boron magnets (NdFeB magnets), which are characterized by their small size. Summary of the invention

[0009] Based on the problems and disadvantages of the prior art, the object of the present invention is to create a more cost-effective and highly dynamic solution.

[0010] To achieve the object according to the invention, a permanently excited electric machine of the type defined at the outset is proposed, having the additional features of the characterizing part of independent claim 1. Furthermore, the invention proposes a simulation method, a system and a corresponding computer program product. The respective dependent claims contain advantageous developments of the invention.

[0011] In the context of the present invention, magnetic anisotropy describes the fact that a magnetic material can have a preferred direction or preferred plane for magnetization. A measure of magnetic anisotropy is the magnetic anisotropy energy, ie the work required to rotate the magnetization out of a preferred direction.

[0012] According to the present invention, magnetic remanence (remanence for short) describes the residual magnetism retained by a permanent magnet after the external magnetic field is removed. In the present invention, remanence accurately describes the residual magnetism if the permanent magnet is exposed to the saturation flux density.

[0013] In the terminology of the present invention, magnetic coercivity refers to the magnetic field strength required to completely and permanently demagnetize a ferromagnetic material previously charged to saturation flux density, so that the total magnetic flux or local magnetic flux density generated is zero. This field strength is usually abbreviated as jHc.

[0014] The present invention solves the stated problem by using CeFeB magnets in combination with a special motor structure.

[0015] In detail, according to the present invention, it is proposed to design the permanent magnet as a CeFeB-based magnet, wherein the permanent magnet extending at least in sections along the longitudinal axis is designed and arranged so that the permanent magnet has a north pole and a south pole on the side facing the gap, respectively, and the magnet size in the preferred direction, starting from the area center of gravity of the north pole, is between 1 / 10 and 1 / 3 of the rotor diameter there.

[0016] A preferred embodiment provides that the diameter of the rotor in the magnet region including the magnets is, for example, 45 mm (+ / -10%). This results in a magnet size in the preferred direction from the center of gravity of the North Pole of between 4.5 mm and 15 mm. With a diameter of 90 mm (+ / -10%), this results in a magnet thickness from the center of gravity of the North Pole of between 9 mm and 30 mm.

[0017] Mixed metal, also called cerium mixed metal, is a metal alloy made from rare earths. Standard quality typically consists of at least 98% rare earth metals, 1% iron and 0.8% magnesium. Due to the great chemical similarity of the metals of the rare earths, the separation of the metals of the rare earths is very difficult, so it is more economical to use mixed metals.

[0018] Iron mixed metal alloys with an iron content of 15% to 50% are known as ferrocerium or under the trade name Auermetall.

[0019] The percentage distribution of rare earth metals in classic mischmetal comes directly from that of the starting mineral monazite: it contains approximately 45% to 52% cerium, 20% to 27% lanthanum, 15% to 18% neodymium, 3% to 5% praseodymium, 1% to 3% samarium, terbium, and yttrium, plus trace amounts of other rare earth metals.

[0020] The preferred improvement of the present invention stipulates that, in addition to technically unavoidable impurities, the permanent magnet also has a material composition according to the mode of the basic composition CeFeB+X+Z. The material contains 20 weight percent to 35 weight percent of cerium. The content of Nd, Pr, La, Y, Dy, Tb, Gd, Ho elements is less than 10 weight percent each, and the total content is less than 15 weight percent. In addition, it is applicable that the sum of Nd, Pr, La, Y, Dy, Tb, Gd, Ho and Ce components is between 25 weight percent and 35 weight percent. The content of component Z is at most 6 weight percent and represents at least one element in Al, Co, Cu, Ga, Si, Ge, and has a content of at most 3 weight percent each. The content of boron element is 0.85 weight percent to 1.1 weight percent. The content of iron element is between 59 weight percent and 75 weight percent or constitutes the rest of the composition.

[0021] Advantageous developments of the invention provide essentially two variants for producing the magnet.

[0022] The first variant (production via the "powder metallurgy route" or "sintered magnet") provides the following method steps:

[0023] - molten alloy,

[0024] - pouring and solidifying the melt to form a solid, preferably during strip casting (or thin strip casting),

[0025] So that the solid is made into the shape of a belt,

[0026] - granulating the solid to a particle size of less than 10 μm, preferably less than 5 μm,

[0027] - aligning particles in a magnetic field to set a preferred direction or magnetic anisotropy,

[0028] - pressing, preferably forming a shell or lens with magnetic anisotropy,

[0029] -sintering,

[0030] -Heat treatment.

[0031] The second variant is the production by a "rapid solidification route" or "hot pressed magnets", providing the following method steps:

[0032] - molten alloy,

[0033] - Rapid solidification to form a solid by means of melt spinning,

[0034] - hot pressed solid,

[0035] - Thermally reshape the raw material to set the preferred direction.

[0036] Rapid solidification is best accomplished with the aid of a rapidly rotating copper wheel ("melt spinning") to rapidly dissipate the heat.

[0037] Optionally, both variants are each post-treated with at least one element from the group Nd, Pr, La, Y, Dy, Tb, Gd, Ho, Bo or alloys thereof via grain boundary diffusion.

[0038] Hot pressing or hot isostatic pressing (HIP) is a development of manufacturing technology in which powders and possibly other solid materials are simultaneously hot pressed and sintered. It involves shaping by pressing and sintering of ceramics in one working sequence.

[0039] In the case of the second variant, the hot reshaping is a forming step above the recrystallization temperature of the metal involved. The hardening that occurs during the forming process can be accompanied by recovery processes and softening processes that occur during and after the forming step. In particular, it involves rolling or pressing of the workpiece.

[0040] It is particularly expedient for the winding system of the machine to be at least partially embedded in the material forming the magnetic circuit.

[0041] According to an advantageous development of the invention, the rotor can be designed as an inner rotor and the permanent magnets can be attached radially to the outside of the rotor.

[0042] According to a further advantageous development of the invention, the rotor can be designed as an outer rotor and the permanent magnets can be arranged on an inner surface of the rotor facing the gap.

[0043] The advantages of the invention are particularly evident when the number of poles of the rotor magnet is less than or equal to 16. The invention is particularly preferred when the number of poles is less than or equal to 8. This can be demonstrated by simulations.

[0044] An advantageous development of the invention provides that the permanent magnet has at least one of the following features:

[0045] - At room temperature, the remanence is between 0.7T and 1.0T.

[0046] - The magnetic coercivity (jHC) at room temperature is between -450 kA / m and -750 kA / m.

[0047] An advantageous development of the invention provides that the machine is designed and the permanent magnets are dimensioned and arranged such that, during operation of the machine, the B-field amplitude of the fundamental wave in the gap is between 0.7T and 0.85T.

[0048] Another advantageous improvement of the invention provides that the permanent magnets each have a north pole and a south pole on the side facing the gap, and the permanent magnets have a horseshoe-shaped, trapezoidal or lens-shaped cross-sectional shape. If the permanent magnets are embodied in a lens-shaped or bowl-shaped manner, it can be ensured that, regardless of the number of poles of the rotor, the section of the permanent magnet facing away from the gap essentially follows the preferred magnetic direction. With the aid of the lens shape, a constant cross section of the permanent magnet for the field line direction is achieved without using excess magnet material. On the one hand, this helps to save mass to reduce inertia and improve dynamics, and on the other hand to maintain the low cost of the magnet.

[0049] An advantageous improvement of the invention further provides that the magnets are designed axially and / or radially and / or circumferentially in a segmented or assembled manner, preferably at least partially glued together. This feasibility opens up good design flexibility due to modularity and makes production easy. Alternatively, the permanent magnets can be designed as one piece at least radially and / or in the circumferential direction, so that improved magnet characteristics can be achieved and the reduced joints do not become mechanical weaknesses.

[0050] In the case where this feasibility provides that the permanent magnets each have a north pole and a south pole on the side facing the gap, it is purposeful, i.e. if the permanent magnets are each designed and attached to the rotor so that the magnet lines enter the rotor from one side of the gap at a first circumferential position, so that they extend tangentially in sections and the magnet lines leave the rotor at a second circumferential position.

[0051] A preferred embodiment of the motor provides a magnet,

[0052] The magnets are preferably divided into axial segments of 3 mm to 5 mm and / or

[0053] - The magnet size in the preferred direction at the center of the pole is between 5 mm and 12 mm in the case of bowl-shaped magnets, and lens-shaped, horseshoe-shaped (see Figure 2 )'s magnets are located between 10 mm and 25 mm.

[0054] Furthermore, a preferred embodiment of the motor provides a motor design, namely:

[0055] - the number of poles is at most 16, particularly preferably 8, and / or

[0056] - the distance between the stator core teeth and the rotor is 0.6 mm to 1 mm and / or

[0057] The stator laminations preferably have a lamination thickness of less than 150 μm and / or

[0058] In all laminations there are slots between the teeth.

[0059] As a result of the invention and the further improvements described, a permanently excited electric machine with lower inductance is obtained. As a result, the current can be built up quickly, which results in high dynamics. In addition, the voltage limit characteristic curve is also shifted to high torques, which also increases the dynamics of the motor. With the help of a thermally permissible stator current, the selected air gap induction enables high torques to be achieved. Therefore, it is also possible to use high dynamics over a long period of time. The stator current produces a low armature reaction, so that the relationship between current and torque is linear at high torques. This improves the power of the engine. The structure according to the invention results in a motor that increases the production efficiency of the application machine. This is particularly suitable for machine tools, robots and production machines.

[0060] An advantageous development provides a computer-implemented method for simulating a machine according to the invention or according to one of its developments. For this purpose, at least one computer including a computer system is preferably designed and prepared for simulation according to the method. Advantageously, a computer or a computer system can be prepared by means of a corresponding computer program product to perform a method according to the invention or one of its developments therefor. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] For the sake of clarity, the present invention will be described in more detail below with reference to specific embodiments. In the drawings:

[0062] Figure 1A schematic, simplified cross-sectional view of a permanently excited electric machine is shown, wherein Figure 1 It is only used to facilitate the understanding of the present invention.

[0063] Figure 2 shows a schematic, simplified cross-sectional view of a first variant of a permanently excited electric machine according to the invention,

[0064] Figure 3 shows a schematic diagram of a first method for manufacturing a permanent magnet,

[0065] Figure 4 shows a schematic diagram of a second method for manufacturing a permanent magnet,

[0066] Figure 5 A schematic diagram of a simulation of the operation of a machine according to the invention running on a computer with a computer program product is shown. DETAILED DESCRIPTION

[0067] Figure 1 and Figure 2 Schematic cross-sectional views of a permanently excited electric machine PDM are shown respectively, which has a stator STT and a rotor RTR mounted so as to be rotatable about a longitudinal axis X. The stator STT has a winding system WND. Permanent magnets PMG are arranged on the rotor RTR. A gap RGP is formed between the rotor RTR and the stator STT. The winding system WND is designed and arranged so that it interacts electromagnetically with the permanent magnets PMG of the rotor RTR via the gap RGP.

[0068] The permanent magnet PMG is designed as a magnet based on CeFeB and extends at least in sections along a longitudinal axis X. In the invention, the permanent magnet PMG has a substantially constant cross section along its axial extension.

[0069] The magnetic material of the permanent magnet PMG has a preferred direction PFD for magnetization, so that the path through the permanent magnet PMG can be respectively limited in the direction of the local preferred direction PFD. The magnet thickness MTH associated with a point on the pole surface PAR is thus defined as the path length from the point along the preferred direction PFD through the permanent magnet PMG to the corresponding point on the other pole surface.

[0070] The winding system WND is embedded in the material MTR forming the magnetic back iron.

[0071] The rotor RTR is designed as an inner rotor, and the permanent magnets PMG are radially mounted on the outer side of the rotor RTR. Alternatively, the rotor RTR can also be designed as an outer rotor, wherein the permanent magnets PMG are arranged on the inner surface of the rotor RTR facing the gap.

[0072] exist Figure 1In the example shown only for facilitating the understanding of the present invention, the permanent magnet PMG covers the rotor RTR in a shell-like manner, leaving a gap RGP. The magnet thickness MTH in the preferred direction starting from the area center of gravity of the north pole NPL is between 1 / 10 and 1 / 5 of the rotor diameter there.

[0073] exist Figure 2 In the embodiment, the permanent magnet PMG has a north pole NPL and a south pole SPL on the side facing the gap RGP, respectively. The magnet thickness MTH in the preferred direction is between 1 / 10 and 1 / 3 of the rotor diameter there, starting from the area center of the north pole NPL.

[0074] Permanent magnet PMG has the following characteristics:

[0075] - At room temperature, the remanence is between 0.7T and 1.0T.

[0076] -At room temperature, the magnetic coercivity jHC is between -450 kA / m and -750 kA / m.

[0077] exist Figure 1 and Figure 2 In the embodiment of the present invention, the number of poles of the permanent magnets PMG on the rotor RTR facing the gap RGP is 8. Each north pole NPL or south pole SPL arranged there is defined by another pole. Figure 2 In the rotor, each pole is formed by two adjacent permanent magnets, which are arranged adjacent to each other in a mirror-inverted manner. There are 8 permanent magnets PMG on each rotor.

[0078] During operation of the machine PDM, the B-field amplitude of the fundamental wave in the gap RGP is between 0.7T and 0.85T.

[0079] In addition to technically unavoidable impurities, permanent magnets PMG are composed of material compositions according to the pattern CeFeB+X+Z, specifically consisting of the following components:

[0080]

[0081]

[0082] exist Figure 3 The schematically illustrated first method for producing a permanent magnet PMG provides the following method steps:

[0083] S1 molten alloy,

[0084] S2 preferably pours and solidifies the melt to form a solid during strip continuous casting, so that the solid is manufactured into the shape of a strip,

[0085] S3 granulating the solid to a particle size of less than 10 μm, preferably less than 5 μm,

[0086] S4 aligns particles in a magnetic field to set a preferred orientation,

[0087] S5 suppression,

[0088] S6 sintering,

[0089] S7 heat treatment,

[0090] S8 utilizes Nd, Pr, La, Y, Dy,

[0091] At least one element of Tb, Gd, Ho, B or their alloys is post-treated.

[0092] exist Figure 4 The schematically illustrated alternative second method for manufacturing a permanent magnet PMG provides the method steps:

[0093] S1 molten alloy,

[0094] S2 is rapidly solidified by melt spinning to form a solid.

[0095] S3 hot pressed solid,

[0096] S4 performs thermal reshaping of the raw material to set the priority direction.

[0097] S5 utilizes Nd, Pr, La, Y, Dy,

[0098] At least one element of Tb, Gd, Ho, B or their alloys is post-treated.

[0099] Figure 5 A schematic diagram of a simulation SIM of a permanently excited electric machine PDM according to the invention is shown, the simulation being run on a computer CMP (here on a plurality of computers CMP of a network WWB including a cloud CLD). The software installed on the computer CMP is a computer program product CPP which, when executed on at least one computer CMP, enables the user to influence or modify the configuration by means of an interface, for example by means of a screen and a keyboard, and to gain knowledge on the basis of the simulation SIM being performed, thus enabling specific technical design decisions to be supported and verified by means of simulation.

[0100] Although the invention has been described and illustrated in more detail by means of preferred embodiments, the invention is not limited to the disclosed examples. A person skilled in the art will be able to derive variations thereof without departing from the scope of protection of the invention defined by the claims.

Claims

1. A permanently excited electric machine (PDM) comprising a stator (STT) and a rotor (RTR) mounted so as to be rotatable about a longitudinal axis (X), in, The stator (STT) has a winding system (WND), wherein permanent magnets (PMG) are arranged on the rotor (RTR), wherein the magnetic material of the permanent magnets (PMG) has a preferred direction (PFD) for magnetization such that a path through the permanent magnets (PMG) can be defined respectively in the direction of the local preferred direction (PFD), wherein a magnet size (MTH) in the preferred direction (PFD) associated with a point on a pole face (PAR) is defined as the path length from the point along the preferred direction (PFD) through the permanent magnet (PMG) to a corresponding point on a further pole face, wherein a gap (RGP) is formed between the rotor (RTR) and the stator (STT), wherein the winding system (WND) is designed and arranged such that it interacts electromagnetically with the permanent magnets (PMG) of the rotor (RTR) via the gap (RGP), It is characterized in that The permanent magnet (PMG) is designed as a magnet based on CeFeB, wherein the permanent magnet (PMG) extending at least partially along the longitudinal axis (X) is designed and arranged such that (a) The permanent magnet (PMG) has a north pole (NPL) and a south pole (SPL) on the side facing the gap (RGP), and the magnet size (MTH) in the preferred direction (PFD) is between 1 / 10 and 1 / 3 of the rotor diameter there, starting from the area center of gravity of the north pole.

2. The machine (PDM) according to claim 1, wherein: The permanent magnet (PMG) has at least one of the following features: -The remanence at room temperature is between 0.7T and 1.0T, -The magnetic coercivity (jHC) at room temperature is between -450 kA / m and -850 kA / m.

3. A machine (PDM) according to claim 1 or 2, wherein: During operation of the machine (PDM), the B-field amplitude of the fundamental in the gap (RGP) is between 0.7T and 0.85T.

4. Machine (PDM) according to at least one of the preceding claims, wherein: The number of poles of the permanent magnets (PMG) on the rotor (RTR) on one side of the gap (RGP) is less than or equal to 16.

5. Machine (PDM) according to at least one of the preceding claims, wherein: The permanent magnet (PMG) has a horseshoe-shaped, trapezoidal-shaped, or lens-shaped cross-sectional shape, and has a north pole and a south pole on a side facing the gap (RGP), respectively.

6. Machine (PDM) according to at least one of the preceding claims, wherein: In addition to technically unavoidable impurities, the permanent magnet (PMG) has a material composition according to the pattern CeFeB+X+Z, which includes:

7. Machine (PDM) according to at least one of the preceding claims, wherein: The permanent magnet (PMG) is produced by means of the following method steps: - molten alloy, - preferably during strip casting, pouring and solidifying the melt to form a solid, so that the solid is produced in the shape of a strip, - granulating the solid to a particle size of less than 10 μm, preferably less than 5 μm, - aligning particles in a magnetic field to set a preferred orientation, -suppress, -sintering, -Heat treatment.

8. Machine (PDM) according to at least one of the preceding claims 1 to 6, wherein: The permanent magnet (PMG) is manufactured by: - molten alloy, - Rapid solidification to form a solid by means of melt spinning, - hot pressing of said solid, - Thermally reshape the material to set the preferred direction.

9. Machine (PDM) according to claim 7 or 8, wherein The permanent magnet (PMG) is produced by means of additional subsequent method steps: - post-treatment with at least one element from the group Nd, Pr, La, Y, Dy, Tb, Gd, Ho, B or alloys thereof via grain boundary diffusion.

10. A computer-implemented method for the simulation (SIM) of a machine (PDM) according to at least one of the preceding claims.

11. A computer system (CPS) comprising at least one computer (CMP) designed and prepared for simulation according to the method according to claim 10.

12. A computer program product for executing the method according to claim 10 by means of a computer system (CPS) according to claim 11.

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