Permanent magnet motor rotor magnetic steel with low eddy current loss

Abstract

A permanent magnet motor rotor magnetic steel with low eddy current loss comprises a permanent magnet of a square structure, the upper and lower edges of the permanent magnet are long edges, the left and right edges of the permanent magnet are short edges, the upper and lower ends of the front and rear side surfaces of the permanent magnet are provided with a plurality of vertical grooves, and the vertical grooves are arranged perpendicular to the long edges. A plurality of transverse grooves are formed in the left end and the right end of the front side surface and the rear side surface of the permanent magnet, and the transverse grooves are perpendicular to the short edges; the length of the vertical groove is 1 / 5-1 / 10 of the length of the long side; and the length of the transverse groove is 1 / 3-1 / 7 of the length of the short side. According to the utility model, the eddy-current loss of the magnet is effectively reduced by identifying an eddy-current loss concentrated area and using the lowest cost in a targeted manner, so that the requirements of low cost and high performance are met, the demagnetization risk of the motor is reduced, and the operation reliability of an electric driving system is improved.

Description

Technical Field

[0001] The utility model relates to the field of electricity, in particular to a permanent magnet motor, in particular to a permanent magnet motor rotor magnetic steel with low eddy current loss. Background Art

[0002] NdFeB permanent magnets are the most widely used magnet materials in the current drive motor field, and their composition contains a high content of iron. As a good conductor of electricity, NdFeB permanent magnets rich in iron are in a high-intensity rotating alternating magnetic field when working inside a permanent magnet motor, which will induce large eddy current losses. The rotor, as a rotating component of the motor, has difficulty dissipating heat when the motor is working, and a large amount of eddy current losses will cause the operating temperature of the permanent magnet to rise. The physical properties of NdFeB permanent magnets determine that their Curie temperature is low. At high operating temperatures, the magnets will experience irreversible magnetic losses. Once irreversible demagnetization occurs in a permanent magnet motor, it will cause major safety risks to the system and even endanger the lives of personnel.

[0003] In the prior art, in order to ensure the anti-demagnetization ability of permanent magnets at high temperatures, heavy rare earth elements need to be added to the magnets, but this will greatly increase the raw material cost of the permanent magnets. In addition, due to the high price of NdFeB permanent magnet materials, processing and bonding them will increase product costs. Utility Model Content

[0004] In view of the shortcomings of the prior art, the utility model provides a permanent magnet motor rotor magnet with low eddy current loss, which overcomes the shortcomings of the prior art. By identifying the area where eddy current loss is concentrated, the eddy current loss of the magnet is effectively reduced at the lowest cost in a targeted manner to meet the requirements of low cost and high performance, reduce the risk of demagnetization of the motor, and provide operational reliability of the electric drive system.

[0005] In order to achieve the above objectives, the present invention is implemented through the following technical solutions:

[0006] A permanent magnet motor rotor magnetic steel with low eddy current loss, comprising a square-structured permanent magnet, wherein the upper and lower sides of the permanent magnet are long sides, the left and right sides of the permanent magnet are short sides, the upper and lower ends of the front and rear side surfaces of the permanent magnet are both provided with a plurality of vertical grooves, the vertical grooves are arranged perpendicular to the long sides, the left and right ends of the front and rear side surfaces of the permanent magnet are both provided with a plurality of transverse grooves, the transverse grooves are arranged perpendicular to the short sides;

[0007] The length of the vertical groove is 1 / 5-1 / 10 of the length of the long side; the length of the transverse groove is 1 / 3-1 / 7 of the length of the short side.

[0008] Preferably, the length of the vertical groove is greater than 5 mm, and the length of the transverse groove is greater than 3 mm.

[0009] Preferably, the depth of the vertical groove and the transverse groove is 0.1-0.3 of the thickness of the permanent magnet.

[0010] Preferably, the depth of the vertical groove and the transverse groove is 0.5-0.75 of the eddy current penetration depth of the permanent magnet.

[0011] Preferably, the upper side surface and the lower side surface of the permanent magnet are both provided with a plurality of end surface grooves, and the two ends of the end surface grooves are respectively connected to the vertical grooves on the front and rear side surfaces of the permanent magnet in a one-to-one correspondence.

[0012] The utility model provides a permanent magnet motor rotor magnet with low eddy current loss. It has the following beneficial effects: on the basis of identifying the concentrated area of ​​eddy current loss of permanent magnets, combined with the difference in the spatial heat dissipation capacity of motors, the vertical grooves and the horizontal grooves are processed at the lowest processing cost, so that the vertical grooves and the horizontal grooves are perpendicular to the flow path of the eddy current of the permanent magnets, so that the eddy current generation path can be effectively destroyed by the vertical grooves and the horizontal grooves, so as to effectively reduce the eddy current loss of the permanent magnets, thereby reducing the working temperature of the permanent magnets, improving the magnetic properties and anti-demagnetization ability of the permanent magnets in the working state, and achieving low cost and high reliability of the permanent magnets of the motors. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the present invention or the prior art, the drawings required for describing the prior art are briefly introduced below.

[0014] Figure 1 It is a schematic diagram of the structure of the utility model;

[0015] Figure 2 It is a schematic diagram of the flow path of the eddy current of the permanent magnet in the utility model;

[0016] Figure 3 It is a schematic diagram of the partitioning of the permanent magnet in the utility model;

[0017] Figure 4 is the permanent magnet distribution diagram of the motor;

[0018] Figure 5 This is a permanent magnet distribution diagram of the motor in the fourth embodiment of the utility model;

[0019] Description of the numbers in the figure:

[0020] 1. Permanent magnet; 2. Vertical groove; 3. Horizontal groove; 4. End face groove. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the present invention.

[0022] Embodiment 1, as Figures 1 to 4 As shown, a permanent magnet motor rotor magnet with low eddy current loss includes a square-structured permanent magnet 1, wherein the upper and lower sides of the permanent magnet 1 are long sides, and the left and right sides of the permanent magnet 1 are short sides. The upper and lower ends of the front and rear side surfaces of the permanent magnet 1 are both provided with a plurality of vertical grooves 2, and the vertical grooves 2 are arranged perpendicular to the long sides. The left and right ends of the front and rear side surfaces of the permanent magnet 1 are both provided with a plurality of transverse grooves 3, and the transverse grooves 3 are arranged perpendicular to the short sides.

[0023] The length of the vertical groove 2 is 1 / 5-1 / 10 of the length of the long side; the length of the transverse groove 3 is 1 / 3-1 / 7 of the length of the short side. In this embodiment, the length of the vertical groove 2 is greater than 5 mm, and the length of the transverse groove 3 is greater than 3 mm.

[0024] Working principle:

[0025] First, according to the law of electromagnetic induction, the induced eddy currents in each permanent magnet will be distributed in a vortex shape around the geometric center of the permanent magnet. The eddy currents in the edge area of ​​the permanent magnet are the largest, and the losses caused are also the largest. Figure 2 As shown. Therefore, in this embodiment, partitions are made along the long side direction of the permanent magnet 1, and the number of partitions is 5-10, and then partitions are made along the short side direction of the permanent magnet 1, and the number of partitions is 3-7, and then the area closest to the outer edge of the permanent magnet 1 is selected as the processing area for reducing eddy current loss, and the middle area of ​​the permanent magnet 1 is not processed; and then the selected processing area is processed into vertical grooves 2 and horizontal grooves 3 by cutting and other means, so that the vertical grooves 2 and the horizontal grooves 3 are perpendicular to the flow path of the eddy current of the permanent magnet 1, so that the eddy current generation path can be effectively destroyed by the vertical grooves 2 and the horizontal grooves 3, which is equivalent to increasing the resistance on the eddy current formation path of the permanent magnet 1, and then effectively achieving the purpose of reducing the eddy current loss of the permanent magnet 1.

[0026] Specifically, taking an electric vehicle drive motor as an example, the permanent magnet distribution of the motor is as follows: Figure 4 As shown. The eddy current loss reduction of permanent magnets is carried out with a single magnet. The size of a single magnet is 33mm*24mm. The single magnet is divided into 6 sub-areas in the length L direction, and the length b of each sub-area is 5.5mm; it is divided into 6 sub-areas in the width W direction, and the width a of each sub-area is 4mm. Then the first circle area on the outermost edge of the magnet is selected as the eddy current reduction area, as shown Figure 3As shown. After calculation, the eddy current loss in this area is 7.779678mW, while the total eddy current loss in other areas is 0.641504mW, that is, the eddy current loss in the selected area accounts for 91.8%. It can meet the goal of reducing eddy current losses in engineering. The outermost first circle area of ​​the magnet can be processed into vertical grooves 2 and horizontal grooves 3 to destroy the eddy current generation path, thereby effectively achieving the purpose of reducing the eddy current loss of the permanent magnet 1.

[0027] Through the above scheme, it is possible to identify the eddy current loss concentration area of ​​the permanent magnet 1, combine the difference in the spatial heat dissipation capacity of the motor, use the lowest processing cost, and effectively reduce the eddy current loss of the permanent magnet, thereby reducing the operating temperature of the permanent magnet, improving the magnetic properties and anti-demagnetization ability of the permanent magnet under working conditions, and achieving low cost and high reliability of the motor permanent magnet.

[0028] Embodiment 2, as a further preferred embodiment of embodiment 1, the depth of the vertical groove 2 and the horizontal groove 3 is 0.1-0.3 of the thickness of the permanent magnet 1. This is to avoid the vertical groove 2 and the horizontal groove 3 being too deep, which would have a significant impact on the structural strength of the permanent magnet 1, thereby ensuring the overall structural strength of the permanent magnet 1.

[0029] Embodiment 3, as a further preferred solution of embodiment 1, the thickness of the vertical groove 2 and the transverse groove 3 is 0.5-0.75 of the eddy current penetration depth of the permanent magnet 1, thereby ensuring that the eddy current flow path of the permanent magnet 1 is effectively blocked.

[0030] In this embodiment, the calculation formula for the eddy current penetration depth of the permanent magnet 1 is:

[0031] △=sqrt(2 / ωμσ)

[0032] Where, σ: permanent magnet conductivity, ω: magnetic field frequency, △: penetration depth, μ: vacuum permeability.

[0033] Embodiment 4, as Figure 5 As shown, as a further preferred embodiment of the first embodiment, a plurality of end face grooves 4 are provided on the upper side and the lower side of the permanent magnet 1, and the two ends of the end face grooves 4 are respectively connected to the vertical grooves 2 on the front and rear sides of the permanent magnet 1 in a one-to-one correspondence. The two groups of vertical grooves 2 located on the front and rear sides of the permanent magnet 1 can be connected in a one-to-one correspondence to form an integral groove structure through the end face grooves 4, so that the eddy current flow path at the outermost edge position of the permanent magnet 1 can be destroyed, thereby further reducing the eddy current loss of the permanent magnet 1.

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A permanent magnet motor rotor magnetic steel with low eddy current loss, characterized in that: The invention comprises a permanent magnet (1) of a square structure, wherein the upper and lower sides of the permanent magnet (1) are long sides, and the left and right sides of the permanent magnet (1) are short sides. The upper and lower ends of the front and rear side surfaces of the permanent magnet (1) are both provided with a plurality of vertical grooves (2), and the vertical grooves (2) are arranged perpendicular to the long sides. The left and right ends of the front and rear side surfaces of the permanent magnet (1) are both provided with a plurality of transverse grooves (3), and the transverse grooves (3) are arranged perpendicular to the short sides. The length of the vertical groove (2) is 1 / 5-1 / 10 of the length of the long side; the length of the transverse groove (3) is 1 / 3-1 / 7 of the length of the short side.

2. The low eddy current loss permanent magnet motor rotor magnetic steel according to claim 1, characterized in that: The length of the vertical groove (2) is greater than 5 mm, and the length of the transverse groove (3) is greater than 3 mm.

3. The low eddy current loss permanent magnet motor rotor magnetic steel according to claim 1, characterized in that: The depth of the vertical groove (2) and the transverse groove (3) is 0.1-0.3 of the thickness of the permanent magnet (1).

4. The low eddy current loss permanent magnet motor rotor magnetic steel according to claim 1, characterized in that: The depth of the vertical groove (2) and the transverse groove (3) is 0.5-0.75 of the eddy current penetration depth of the permanent magnet (1).

5. The low eddy current loss permanent magnet motor rotor magnetic steel according to claim 1, characterized in that: The upper side and the lower side of the permanent magnet (1) are both provided with a plurality of end surface grooves (4), and the two ends of the end surface grooves (4) are respectively connected to the vertical grooves (2) on the front and rear side surfaces of the permanent magnet (1) in a one-to-one correspondence.

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