A General Modeling Method for Reducing Stress Concentration in Embedded Permanent Magnet Motor Rotors

Abstract

This invention discloses a general modeling method for magnet slots in embedded permanent magnet motors to reduce stress concentration in the rotor, belonging to the field of motor rotor design. The magnet slots are circumferentially distributed within the rotor body, and each slot includes six sequentially connected side segments. The curved side segments are smoothly connected by several interpolation function curves. The smooth transition between the side segments effectively reduces the mechanical stress at the connection points of the magnet slots, thus facilitating further increases in rotational speed. A shoulder constructed using interpolation functions is provided near the inner side of the rotor body to support the magnets in the direction of centrifugal force during high-speed motor rotation, further reducing the significant stress on the side segments of the magnet slots under centrifugal force. A slot is also provided near the shoulder to alleviate stress concentration caused by the thermal expansion and contraction of the material. Results show that this magnet slot modeling method is easy to implement and significantly alleviates the mechanical stress concentration in the rotor body during high-speed rotation, thereby ensuring its safe and reliable operation.

Description

Technical Field

[0001] This invention relates to the field of motor rotor design technology, and in particular to a general modeling method for magnet slots that reduces stress concentration in embedded permanent magnet motor rotors. Background Technology

[0002] The performance of the drive motor in new energy vehicles directly affects the overall performance of the vehicle. Increasing the maximum speed of the motor can improve the power density of the drive motor, thereby enhancing the market competitiveness of the drive motor product. As the maximum speed of the motor increases, the maximum mechanical stress borne by the motor rotor laminations will also increase accordingly. Especially under high-speed rotation conditions, stress concentration occurs in some areas of the rotor laminations. Once the stress value exceeds the yield strength of the rotor material, the rotor may undergo plastic deformation or even fracture, posing a serious threat to the safe operation of the motor.

[0003] Embedded permanent magnet synchronous motors (PMSMs) have become the mainstream choice for new energy vehicle motors both domestically and internationally due to their high power density and efficiency. Reducing rotor mechanical stress concentration has become a key issue in improving the performance of new energy vehicle drive motors. Methods to address rotor mechanical stress concentration encompass multiple aspects, including structural design, loading methods, material selection, surface strengthening treatment, and process improvement. Among these, structural design of the rotor laminations can effectively mitigate stress concentration, improve rotor strength, and thus ensure the safe and stable operation of the motor under high-speed rotation conditions. Existing magnet slot modeling methods are limited by their simplistic approach, typically relying on rounded corners for smooth transitions between connecting sections, which has limited effectiveness in improving stress concentration in the rotor laminations. Considering the rapid development of electric vehicle drive motor technology, many high-end models now exceed 20,000 rpm. This high speed directly presents a significant challenge: a substantial increase in the mechanical stress borne by the rotor. Therefore, exploring methods to reduce rotor mechanical stress through structural design and improving the reliability and durability of rotor laminations is crucial for ensuring the safe and stable operation of new energy vehicle drive motors. Summary of the Invention

[0004] This invention provides a general modeling method for magnet slots to reduce stress concentration in the rotor of an embedded permanent magnet motor, which can reduce the mechanical stress concentration in the rotor of a high-speed drive motor, thereby ensuring the safe operation of the motor at high speed.

[0005] A first aspect of the present invention provides a general modeling method for magnet slots to reduce stress concentration in the rotor of an embedded permanent magnet motor, comprising the following steps:

[0006] Step 1: Parameterize the geometric dimensions of the motor rotor plate and determine the coordinates of the key nodes on the magnet and magnet slots used to establish the interpolation function;

[0007] Step 2: Determine the parameterized equation form of the basis function of the interpolation modeling method and perform preliminary segmentation of the magnetic steel trough;

[0008] Step 3: Based on the positional characteristics of different parts of the magnetic steel channel, determine the interpolation nodes of each segment of the magnetic steel channel, define the modeling function, and perform segmented modeling of the magnetic steel channel.

[0009] Step 4: Import the three-dimensional structural model of the rotor into the stress analysis module of the structural finite element software to perform stress verification of the rotor plates and obtain the stress cloud diagram of the rotor plates.

[0010] Step 5: Based on the stress cloud diagram of the rotor lamination, obtain the maximum rotor mechanical stress of the lamination model after segmented modeling in Step 3. Determine whether the obtained maximum rotor mechanical stress is greater than the yield strength of the rotor silicon steel lamination. If so, the current rotor lamination is at risk of structural failure, and proceed to Step 6; otherwise, the magnet slot model is established.

[0011] Step 6: Establish new interpolation nodes for each segment of the magnet slot and return to Step 3 until the risk of rotor plate structure failure is eliminated.

[0012] Optionally, in one embodiment of the present invention, the parametric model of the motor rotor lamination geometry in step 1 includes V-shaped embedded, Delta-shaped embedded, and double-layer V-shaped embedded rotor laminations.

[0013] Optionally, in one embodiment of the present invention, the rotor lamination includes a lamination body and multiple pairs of magnet slots formed on the lamination body. Each magnet slot is formed by several side segments connected in sequence. Except for the side segments that are in close contact with the magnets, the remaining side segments are all composed of different interpolation function curves. The magnet slots are drawn using interpolation functions, which makes each side segment of the magnet slot smooth while also ensuring a smooth transition between adjacent side segments at the connection point.

[0014] Optionally, in one embodiment of the present invention, each side segment of the magnetic steel groove has no less than two interpolation nodes. At the same time, the connection points of adjacent side segments are all used as nodes of the interpolation function, so that the function trajectory of adjacent side segments maintains at least first-order continuity at each connection point, thereby ensuring a smooth transition between adjacent side segments at the connection points.

[0015] Optionally, in one embodiment of the present invention, there is a shoulder protruding towards the inside of the magnet on both sides near and away from the outer edge of the sheet. The shoulder near the outer edge of the sheet supports the magnet in the direction of centrifugal force when rotating at high speed, and the shoulder away from the outer edge of the sheet assists in the positioning of the magnet. The supporting sections of the shoulders are all straight sections in contact with the magnet, while the transition sections connecting with other side sections are all modeled using the interpolation function method.

[0016] Optionally, in one embodiment of the present invention, the two segments of the magnet groove closest to and furthest from the outer edge of the sheet are each composed of six interpolation function curves. The curve segments are smoothly connected, and the tangent angle between adjacent segments at the connection point is an obtuse angle. At the same time, the two curve segments closest to the outer edge of the sheet gradually bend towards the inner side of the sheet, that is, the thickness of the magnetic bridge formed by the two curve segments closest to the outer edge of the sheet and the outer edge of the sheet gradually increases. The side segments of each segment of the magnet groove that are close to the two shoulder segments are also drawn using interpolation function curves, forming the connecting segment of the shoulder segment, and also forming the connecting segment of the side segment where the magnet is located.

[0017] Optionally, in one embodiment of the present invention, each segment of the magnet slot constitutes two interpolation nodes of the interpolation function, and the updated interpolation node positions are adjusted according to the stress distribution of the rotor laminations.

[0018] Optionally, in one embodiment of the present invention, specific interpolation nodes are selected in each side segment of the magnetic steel groove of the sheet body, so that the two side segments near the shoulder are not in contact with the magnet, and the curved segments located at the left and right ends of the magnet near the edge of the sheet body are not in contact with the magnet, but arch towards the outer edge of the sheet body.

[0019] A second aspect of the present invention provides a rotor plate, which is designed by the general modeling method for reducing stress concentration in the rotor of an embedded permanent magnet motor as described in the above embodiments.

[0020] The general modeling method for reducing stress concentration in the rotor of an embedded permanent magnet motor according to embodiments of the present invention has the following characteristics:

[0021] Beneficial effects:

[0022] 1. The magnetic slot modeling method of the present invention has the characteristics of universality, which reduces the concentration of mechanical stress in the rotor from the rotor structure design, making the development of embedded permanent magnet motor rotors more efficient.

[0023] 2. The rotor blades obtained using the magnetic slots designed in this invention significantly alleviate stress concentration under high-speed motor conditions, further ensuring the improvement of motor power density.

[0024] 3. The optimization design method of this invention is intuitive and easy to implement.

[0025] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0026] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0027] Figure 1 A flowchart of a general modeling method for reducing stress concentration in the rotor of an embedded permanent magnet motor according to an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram illustrating the execution process of the general modeling method for reducing stress concentration in the rotor of an embedded permanent magnet motor according to an embodiment of the present invention.

[0029] Figure 3 This is the rotor plate topology of the dual-V-shaped embedded permanent magnet drive motor involved in the embodiments of the present invention;

[0030] Figure 4 This is a partial structural diagram of a rotor lamination provided with magnets according to an embodiment of the present invention;

[0031] Figure 5 for Figure 4 Enlarged view of part A;

[0032] Figure 6 for Figure 4 Enlarged view of part B;

[0033] Figure 7 This is a stress distribution cloud diagram of the rotor lamination in an embodiment of the present invention.

[0034] Reference numerals: 00-Sheet body, 01-Outer edge of sheet body, 10-Magnet groove, 11-First section, 111-First curved section, 112-Second curved section, 113-Third curved section, 114-Fourth curved section, 12-Second section, 13-Third section, 14-Fourth section, 15-Fifth section, 155-Fifth curved section, 156-Sixth curved section, 16-Sixth section, 17-Shoulder section, 171-Shoulder support section, 18-Shoulder section, 181-Shoulder support section, 20-Magnet. Detailed Implementation

[0035] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0036] Figure 1 This is a flowchart of a general modeling method for reducing stress concentration in the rotor of an embedded permanent magnet motor, according to an embodiment of the present invention.

[0037] like Figure 1 As shown, the general modeling method for reducing stress concentration in the rotor of an embedded permanent magnet motor, specifically the magnet slot, includes the following steps:

[0038] Step 1: Parameterize the geometric dimensions of the motor rotor plate and determine the coordinates of the key nodes on the magnet and magnet slots used to establish the interpolation function;

[0039] Step 2: Determine the parameterized equation form of the basis function of the interpolation modeling method and perform preliminary segmentation of the magnetic steel trough;

[0040] Step 3: Based on the positional characteristics of different parts of the magnetic steel channel, determine the interpolation nodes of each segment of the magnetic steel channel, define the modeling function, and perform segmented modeling of the magnetic steel channel.

[0041] Step 4: Import the three-dimensional structural model of the rotor into the stress analysis module of the structural finite element software to perform stress verification of the rotor plates and obtain the stress cloud diagram of the rotor plates.

[0042] Step 5: Based on the stress cloud diagram of the rotor lamination, obtain the maximum rotor mechanical stress of the lamination model after segmented modeling in Step 3. Determine whether the obtained maximum rotor mechanical stress is greater than the yield strength of the rotor silicon steel lamination. If so, the current rotor lamination is at risk of structural failure, and proceed to Step 6; otherwise, the magnet slot model is established.

[0043] Step 6: Establish new interpolation nodes for each segment of the magnet slot and return to Step 3 until the risk of rotor plate structure failure is eliminated.

[0044] In one embodiment of the present invention, the parametric model of the geometric surface of the motor rotor plate in step 1 includes, but is not limited to, V-shaped embedded, Delta-shaped embedded, and double-layer V-shaped embedded rotor plates.

[0045] In one embodiment of the present invention, each magnet slot is formed by connecting several edge segments sequentially. Except for the edge segments directly adjacent to the magnet, the remaining edge segments are all composed of different interpolation function curves. The parametric equation of the interpolation function for each minimum edge segment is shown below. Equations (1) to (4) are the interpolation harmonic basis functions, and equations (5) and (6) are the interpolation function equation trajectories of each curved edge segment of the magnet slot based on two nodes in a unified coordinate system. By using this function equation to draw the magnet slot while balancing the ease of processing, the edge segments of the magnet slot are made smooth to avoid stress concentration caused by sharp edges. This also allows for a smooth transition between adjacent edge segments at the connection point, further reducing transition stress and ensuring the safe and stable operation of the motor at high speeds. Based on this idea, relevant programming languages ​​such as Python can be used to automatically model each layer of magnet slots in the sheet, thus developing a general modeling method to reduce rotor stress concentration.

[0046] h 00 =2t 3 -3t 2 +1 (1)

[0047] h 01 =t 3 -2t 2 +t (2)

[0048] h 10 =-2t 3 +3t 2 (3)

[0049] h 11 =t 3 -t 2 (4)

[0050] x(t)=h 00 *x1+h 01 *x′1+h 10 *x2+h 11 *x′2 (5)

[0051] y(t)=h 00 *y1+h 01 *y′1+h 10 *y2+h 11 *y′2 (6)

[0052] t = ∈ [0, 1] (7)

[0053] In step 2, the interpolation function basis functions used in this embodiment of the invention include, but are not limited to, the forms proposed in this invention, and the number of segments in the magnet slot includes, but is not limited to, the forms adopted in this invention. In step 3, different interpolation functions are used to model the permanent magnet slot in segments, and different interpolation nodes are used for different parts of the magnet slot to draw the edge segments. While ensuring that each edge segment of the magnet slot is smooth, adjacent edge segments can also transition smoothly, thereby reducing transition stress and further improving the strength of the rotor plate.

[0054] Optionally, in one embodiment of the present invention, the rotor lamination includes a lamination body and multiple pairs of magnet slots formed on the lamination body. Each magnet slot is formed by several side segments connected in sequence. Except for the side segments that are in close contact with the magnets, the remaining side segments are all composed of different interpolation function curves. The magnet slots are drawn using interpolation functions, which makes each side segment of the magnet slot smooth while also ensuring a smooth transition between adjacent side segments at the connection point.

[0055] Optionally, in one embodiment of the present invention, the specific interpolation basis functions for each side segment of the magnetic steel groove are given in the invention description section of the specification. Each side segment of the magnetic steel groove has at least two interpolation nodes, which largely avoids stress concentration caused by sharp edges. Simultaneously, the connection points of adjacent side segments are all used as nodes of the interpolation function, ensuring that the function trajectories of adjacent side segments maintain first-order continuity at the connection points, thereby guaranteeing a smooth transition between adjacent side segments at the connection points.

[0056] Optionally, in one embodiment of the present invention, each magnet groove is formed by a number of side segments that are smoothly connected in sequence, and the curved sections of each side segment are drawn by a specific interpolation function curve. There is a shoulder protruding towards the inside of the magnet on both sides near and away from the outer edge of the sheet. The shoulder near the outer edge of the sheet supports the magnet in the direction of centrifugal force when rotating at high speed, and the shoulder away from the outer edge of the sheet assists in the positioning of the magnet. The supporting sections of the shoulders are all straight sections in contact with the magnet, and the transition sections connecting with other side segments are all modeled using the above-mentioned interpolation function method.

[0057] Optionally, in one embodiment of the present invention, the two segments of the magnet groove closest to and furthest from the outer edge of the sheet are each composed of six interpolation function curves. The curve segments are smoothly connected, and the tangent angle between adjacent segments at the connection point is obtuse, effectively reducing the transition stress at the connection point. At the same time, the two curve segments closest to the outer edge of the sheet gradually bend towards the inner side of the sheet, that is, the thickness of the magnetic bridge formed by the two curve segments closest to the outer edge of the sheet and the outer edge of the sheet gradually increases. The edge segments of each segment of the magnet groove that are close to the two shoulder segments are also drawn using interpolation function curves. These edge segments form the connecting segments of the shoulder segments and also form the connecting segments of the edge segments where the magnet is located.

[0058] Specifically, the section of the magnet groove near the outer edge of the sheet is made to gradually bend inwards towards the inner edge of the sheet using appropriate interpolation nodes, thus gradually increasing the thickness of the magnetic bridge formed with the outer edge of the sheet. The magnet groove employs a suitable segmentation method and corresponding interpolation nodes so that the long end of the magnet is not completely flush with the sheet.

[0059] Optionally, in one embodiment of the present invention, each segment of the magnet slot constitutes two interpolation nodes of the interpolation function, and the updated interpolation node positions are adjusted according to the stress distribution of the rotor laminations.

[0060] Optionally, in one embodiment of the present invention, specific interpolation nodes are selected in each side segment of the magnetic steel groove of the sheet body, so that the two side segments near the shoulder are not in contact with the magnet, and the curved segments located at the left and right ends of the magnet near the edge of the sheet body are not in contact with the magnet, but arch towards the outer edge of the sheet body. This can effectively reduce the stress concentration caused by the thermal expansion and contraction characteristics of the material.

[0061] The following describes the general modeling method for reducing stress concentration in the rotor of an embedded permanent magnet motor according to the present invention, using a specific embodiment and accompanying drawings.

[0062] like Figure 2 As shown, the general modeling method for reducing stress concentration in the rotor of an embedded permanent magnet motor includes:

[0063] S1. Parameterize the geometric dimensions of the motor rotor to determine the coordinates of key nodes on the magnet slots used to establish the interpolation function. This geometric surface can be a rotor plate of types such as V-shaped embedded, Delta-shaped embedded, and double-layer V-shaped embedded.

[0064] S2. Call the modeling and simulation interface of the finite element software, use the interpolation basis functions of equations (1) to (4) to model the magnetic steel groove in segments, and use appropriate interpolation nodes for different positions of the magnetic steel groove to obtain different interpolation function curves.

[0065] S3. Use structural finite element software to simulate and obtain the mechanical stress cloud diagram of the rotor plate, and examine the relationship between the maximum mechanical stress of the rotor and the yield strength of the silicon steel sheet to ensure the safe and stable operation of the constructed rotor plate.

[0066] S4. If the maximum mechanical stress of the rotor laminations under high-speed conditions exceeds the yield strength of the silicon steel laminations, there is a risk of structural failure. Therefore, for the portion of the magnet slot with high stress concentration, re-select interpolation nodes to model that portion until the motor rotor can operate safely and stably.

[0067] Example:

[0068] S1. First, parametric modeling of the motor rotor geometry is performed, mainly to determine the coordinates of each node of the magnet and the interpolation node corresponding to the magnet slot.

[0069] S2. Using the interpolation basis functions and interpolation curve drawing methods shown in formulas (1) to (7), different interpolation function curves are flexibly selected to draw the magnetic steel grooves, ensuring that each side segment is smoothly curved while making the connection of each side segment smooth. Multiple sets of magnetic steel grooves 10 are distributed on the sheet body 00. Figure 3 As shown, the magnet slots are double-layered and consist of eight sets circumferentially. Each pair of magnets is arranged in a V-shape, with the opening facing outwards from the plate. The size of the V-angle of the magnet slots is not limited, and the V-angle of each layer of magnet slots can be different. The magnet slots 10 of this invention, based on a double-layered V-shaped arrangement in the plate 00, can effectively improve the problem of mechanical stress concentration in the motor rotor, thereby further increasing the motor speed.

[0070] like Figure 4As shown, the magnet groove 10 is composed of six segments connected sequentially: segment 11, segment 12, segment 13, segment 14, segment 15, and segment 16. The curved sections of these six segments are drawn using interpolation function curves, which significantly reduces stress concentration. Furthermore, the smooth connection between adjacent segments increases the stress-bearing area, further avoiding stress concentration problems caused by sharp transitions and improving the strength of the sheet. Additionally, a shoulder segment 17 facing inwards is provided on the side of the magnet groove 10 near the outer edge of the sheet, used to support the magnet 20 in the direction of centrifugal force during sheet rotation. Correspondingly, another shoulder segment 18 is provided on the side near the center of the sheet to assist the shoulder segment 17 in limiting the movement of the magnet 20.

[0071] In this invention, the adjacent curved segments of the magnet groove 10 drawn using interpolation functions can transition smoothly. For example, the third curved segment 113 and the fourth curved segment 114 of the first segment 11 of the magnet groove 10 transition naturally and smoothly using interpolation functions, and the connection points are all arched outwards. This is more effective than simple chamfering in reducing the transition stress in this area and avoiding stress concentration, thereby further increasing the upper limit of the motor speed. Furthermore, using interpolation functions to draw the curved segments of the magnet groove 10 can simply and effectively ensure the smooth transition at the connection points of each segment, thus forming a general modeling method for magnet grooves that reduces stress concentration and reduces the difficulty of sheet design. At the same time, one end of the fourth curved segment 114 of the magnet groove 10 is smoothly connected to the third curved segment 113 using an interpolation function curve, while its other end is smoothly connected to the fifth curved segment 115. At the same time, the tangent at the endpoint forms an obtuse angle with the shoulder support segment 171, which can reduce the stress concentration caused by the shoulder segment 17 at this point.

[0072] like Figure 5As shown, in this invention, the first curved section 111 of the first segment 11 of the magnetic groove 10 does not adhere to the side of the magnet 20 near the outer edge of the sheet, and part of the curved section of the fifth segment 15 also does not adhere to the magnet 20. That is, the magnet 20 can partially adhere to the sixth segment 16 when subjected to centrifugal force. The first segment 11 of the magnetic groove 10 gradually bends towards the inner side of the sheet from the second curved section 112 to the third curved section 113. The thickness of the magnetic bridge formed by the latter half of the second curved section 112 and the third curved section 113 with the outer edge 01 of the sheet gradually increases, that is, the second curved section 112 and the third curved section 113 gradually move away from the corresponding outer edge 01 of the sheet and are not parallel to the outer edge 01. The area between the second curved section 112, the third curved section 113 and the outer edge 01 of the sheet is called the magnetic bridge. Due to the positional limitations of the magnet 20 and the consideration of the influence of magnetic leakage, the magnetic bridge is usually not set very large, and since this area is close to the outer edge 01 of the sheet, it will result in a large stress in this area. Therefore, setting the interpolation function curves of the second bending segment 112 and the third bending segment 113 to gradually bend inward can increase the interval between the bending segment and the outer edge 01 of the sheet, thereby effectively alleviating the stress concentration in this area.

[0073] like Figure 5 , Figure 6 As shown, in this invention, the second segment 12 and the fourth segment 14 of the magnet groove 10 are smoothly connected to the shoulder support segments 171 and 181 and the third segment 13, respectively. The two curved segments constituting the second segment 12 and the fourth segment 14 are smoothly connected using interpolation functions, and neither the second segment 12 nor the fourth segment 14 is in contact with the magnet 20. This reduces the transition stress at the connection point and alleviates stress concentration caused by the material's thermal expansion and contraction, further ensuring the safe and stable operation of the motor.

[0074] like Figure 6 As shown, the fifth segment 15 of the magnet groove 10 is also composed of six side segments, each drawn by an interpolation function curve. Adjacent side segments transition smoothly at the connection points, which, compared to simple chamfering, effectively reduces stress concentration in the transition section. Furthermore, this magnet groove drawing method is easy to parameterize, thus forming a general modeling method for magnet grooves that reduces stress concentration. It is worth emphasizing that the shoulder support segment 181 is smaller than 171. During sheet rotation, the shoulder segment 17 mainly supports the magnet 20 in the centrifugal force direction, while the shoulder segment 18 primarily serves to limit the movement of the magnet 20. The fifth curved segment 155 and the sixth curved segment 156 of the fifth segment 15 of the magnet groove 10 do not adhere to the magnet but arch towards the outer edge of the sheet. This effectively reduces stress concentration caused by the material's thermal expansion and contraction properties.

[0075] S3. The rotor topology drawn based on the magnet slot modeling method proposed in this invention is subjected to stress calculation using structural finite element software at a motor speed of 20000 rpm. Figure 7 The diagram shows the mechanical stress contour of the rotor laminations. It indicates that the maximum mechanical stress of the rotor laminations is 328.44 MPa, which is less than the yield strength of the silicon steel laminations (370 MPa). Furthermore, compared to traditional magnetic slots, the magnetic slots established using this method significantly reduce the concentration of mechanical stress in the rotor, further ensuring the safe and stable operation of the motor at high speeds.

[0076] The embodiments of the present invention also propose a rotor plate body, which is designed using the general modeling method for reducing stress concentration in embedded permanent magnet motor rotors described in the above embodiments.

[0077] According to an embodiment of the present invention, a general modeling method for reducing stress concentration in the rotor of an embedded permanent magnet motor is proposed for magnet slots. The magnet slots are circumferentially distributed within the rotor body, and each magnet slot includes six sequentially connected side segments. The curved side segments are smoothly connected by several interpolation function curves. Furthermore, the smooth transition between the side segments effectively reduces the mechanical stress at the magnet slot connections, thereby facilitating further increases in rotational speed. A shoulder constructed using interpolation functions is provided near the inner side of the rotor body to support the magnets in the centrifugal force direction during high-speed motor rotation, further reducing the significant stress on the side segments of the magnet slots under centrifugal force. A slot is also provided near the shoulder to alleviate stress concentration caused by the thermal expansion and contraction of the material. Results show that this magnet slot modeling method is easy to implement and significantly alleviates the mechanical stress concentration in the rotor body during high-speed rotation, thus ensuring its safe and reliable operation.

[0078] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0079] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0080] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or N executable instructions for implementing custom logic functions or processes, and the scope of preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

Claims

1. A general modeling method for magnet slots to reduce stress concentration in the rotor of an embedded permanent magnet motor, characterized in that, Includes the following steps: Step 1: Parameterize the geometric dimensions of the motor rotor plate and determine the coordinates of the key nodes on the magnet and magnet slots used to establish the interpolation function; Step 2: Determine the parameterized equation form of the basis function of the interpolation modeling method and perform preliminary segmentation of the magnetic steel trough; Step 3: Based on the positional characteristics of different parts of the magnetic steel channel, determine the interpolation nodes of each segment of the magnetic steel channel, define the modeling function, and perform segmented modeling of the magnetic steel channel. Step 4: Import the three-dimensional structural model of the rotor into the stress analysis module of the structural finite element software to perform stress verification of the rotor plates and obtain the stress cloud diagram of the rotor plates. Step 5: Based on the stress cloud diagram of the rotor lamination, obtain the maximum rotor mechanical stress of the lamination model after segmented modeling in Step 3. Determine whether the obtained maximum rotor mechanical stress is greater than the yield strength of the rotor silicon steel lamination. If so, the current rotor lamination is at risk of structural failure, and proceed to Step 6; otherwise, the magnet slot model is established. Step 6: Establish new interpolation nodes for each segment of the magnet slot and return to Step 3 until the risk of rotor plate structure failure is eliminated.

2. The method according to claim 1, characterized in that, The parametric model of the motor rotor blade geometry in step 1 includes V-shaped embedded, Delta-shaped embedded, and double-layer V-shaped embedded rotor blades.

3. The method according to claim 1, characterized in that, The rotor lamination includes a lamination body and multiple pairs of magnet slots formed on the lamination body. Each magnet slot is composed of several side segments connected in sequence. Except for the side segments that are in close contact with the magnets, the remaining side segments are all composed of different interpolation function curves. The magnet slots are drawn using interpolation functions, which makes each side segment of the magnet slot smooth while also ensuring a smooth transition between adjacent side segments at the connection point.

4. The method according to claim 1, characterized in that, Each side segment of the magnetic steel groove has no fewer than two interpolation nodes. At the same time, the connection points of adjacent side segments are all used as nodes of the interpolation function, so that the function trajectory of adjacent side segments maintains at least first-order continuity at each connection point, thus ensuring a smooth transition between adjacent side segments at the connection points.

5. The method according to claim 4, characterized in that, There is a shoulder protruding inward on both sides of the outer edge of the sheet and the outer edge of the sheet. The shoulder closer to the outer edge of the sheet supports the magnet in the direction of centrifugal force when rotating at high speed, while the shoulder further away from the outer edge of the sheet assists in the positioning of the magnet. The supporting sections of the shoulders are all straight sections in contact with the magnet, while the transition sections connecting with other side sections are modeled using the interpolation function method.

6. The method according to claim 5, characterized in that, The two segments of the magnet groove closest to and furthest from the outer edge of the sheet are each composed of six interpolation function curves. The curve segments are smoothly connected, and the tangent angle between adjacent segments at the connection point is an obtuse angle. At the same time, the two curve segments closest to the outer edge of the sheet gradually bend towards the inner side of the sheet, that is, the thickness of the magnetic bridge formed by the two curve segments closest to the outer edge of the sheet and the outer edge of the sheet gradually increases. The edge segments of each segment of the magnet groove that are closest to the two shoulder segments are also drawn using interpolation function curves, forming the connecting segments of the shoulder segments, and also forming the connecting segments of the edge segments where the magnet is located.

7. The method according to claim 5, characterized in that, Each segment of the magnet slot forms an interpolation function with two interpolation nodes, and the updated interpolation node positions are adjusted according to the stress distribution of the rotor laminations.

8. The method according to claim 5, characterized in that, In each side segment of the magnetic steel groove of the sheet body, specific interpolation nodes are selected so that the two side segments near the shoulder are not in contact with the magnet, and the curved segments located at the left and right ends of the magnet near the edge of the sheet body are not in contact with the magnet, but arch towards the outer edge of the sheet body.

9. A rotor plate body, characterized in that, The rotor plate is designed using the general modeling method for reducing stress concentration in embedded permanent magnet motor rotors as described in any one of claims 1-8.

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