Permanent magnet synchronous motor rotor core, optimization method and permanent magnet synchronous motor

Abstract

The invention discloses a permanent magnet synchronous motor rotor core, an optimization method and a permanent magnet synchronous motor, a magnetic isolation bridge with built-in trapezoidal grooves is arranged between adjacent grooves of circumferential permanent magnet grooves, and the magnetic isolation bridge forms a narrow neck part close to the center of a rotor and a wide base part close to the outer circle of the rotor by utilizing the inclined design of at least one side wall of each trapezoidal groove; when the motor works, the magnetic flux density of the narrow neck part is higher than that of the wide base part, and the narrow neck part is in a local magnetic saturation state. Only by optimizing the structure of the rotor iron core, the manufacturing process can be simplified, the material and assembly cost can be reduced, and the large-scale mass production requirement can be met; meanwhile, the core advantages of magnetic flux leakage suppression, high rotating speed and large reluctance torque are considered, and the contradiction between magnetic flux leakage control and power density is solved; effective magnetic flux loss can be reduced, more magnetic flux can enter a stator and rotor air gap, the magnetic flux density is improved, the back electromotive force sine property is optimized, the magnetic steel utilization rate and the motor operation efficiency are remarkably improved, and resource waste and performance loss caused by magnetic leakage are avoided.

Description

Technical Field

[0001] This application relates to the field of motor rotor core technology, and more specifically, to a permanent magnet synchronous motor rotor core, an optimization method, and a permanent magnet synchronous motor. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs), with their core advantages of high power density and high efficiency, have become key drive components in industrial control, electric vehicles, and other fields, especially in applications with strict requirements on equipment size and output torque. Among them, built-in PMSMs, compared to surface-mounted PMSMs, offer higher rated speeds and additional reluctance torque, allowing for greater torque output while reducing motor size. This better meets the current technological demands for high power density and miniaturization, making them the mainstream choice in the market. The rotor core, as the core structure of a built-in PMSM, directly affects the motor's leakage flux control and performance. Constructing a reasonable rotor core structure to balance torque output and leakage flux suppression is a necessary direction for promoting motor performance upgrades.

[0003] Currently, most commercially available built-in permanent magnet synchronous motors adopt a tangential rotor core structure. This structure presents a core technical contradiction: it is difficult to simultaneously improve motor output torque and reduce leakage flux. This structure is prone to forming leakage flux paths, leading to effective magnetic flux loss and affecting motor efficiency and magnet utilization. To address this issue, existing technologies have proposed several improvement schemes: First, using a non-magnetic shaft structure to block shaft leakage flux through non-magnetic materials. However, non-magnetic materials are difficult to process and have high production costs, hindering large-scale mass production. Second, introducing additional coils to suppress leakage flux through the magnetic isolation bridge can increase the air gap magnetic field strength, but these additional coils occupy internal space, increasing motor size and reducing power density. Third, filling the magnetic isolation area with non-magnetic materials requires additional material filling and curing processes, which not only complicates the rotor core structure but may also affect the long-term operational stability of the motor due to differences in the thermal expansion coefficients of the materials.

[0004] These existing solutions are either too expensive, sacrifice motor size and power density, or increase structural complexity. None of them can solve the leakage flux problem simply and efficiently while ensuring the core performance of the motor. There is an urgent need for a rotor core design solution that is simple in structure, low in cost, and compatible with built-in tangential structure. Summary of the Invention

[0005] This application provides a permanent magnet synchronous motor rotor core, an optimization method, and a permanent magnet synchronous motor. By setting a magnetic isolation bridge with a built-in trapezoidal slot between adjacent slots of the circumferential permanent magnet slots, it can simplify processing, reduce costs to adapt to mass production, maintain structural compactness, and take into account leakage flux suppression and the advantages of high speed and large reluctance torque. It can also reduce leakage flux to increase air gap magnetic flux density and optimize the sinusoidal nature of back electromotive force, ultimately improving the utilization rate of magnets and the operating efficiency of the motor.

[0006] A permanent magnet synchronous motor rotor core, comprising:

[0007] The rotor core has multiple permanent magnet slots arranged circumferentially to accommodate permanent magnets.

[0008] A magnetic isolation bridge structure is provided between adjacent permanent magnet slots, and the magnetic isolation bridge structure includes a built-in trapezoidal slot.

[0009] At least one side wall of the built-in trapezoidal groove is inclined, so that the magnetic bridge forms a narrow neck on the side near the center of the rotor and a wide base on the side near the outer circle of the rotor.

[0010] The narrow neck is configured such that the magnetic flux density is higher than that of the wide base when the motor is operating, thereby causing the magnetic isolation bridge to be in a state of local magnetic saturation during operation, so as to block the leakage magnetic path.

[0011] Optionally, the sidewall inclination angle of the built-in trapezoidal groove is configured such that the magnetic reluctance of the magnetic isolation bridge changes non-linearly in the radial direction, so as to guide the magnetic lines of force to converge toward the air gap direction.

[0012] Optionally, the bottom of the built-in trapezoidal groove is provided with an arc transition structure for dispersing stress.

[0013] Optionally, the ratio of the width of the magnetic isolation bridge to the width of the permanent magnet groove decreases radially.

[0014] Optionally, the magnetic bridge has a minimum cross-sectional area portion, the size of which is configured to enter a magnetic saturation state when the motor is running under no-load.

[0015] Optionally, the permanent magnet slots are arranged tangentially, and the built-in trapezoidal slots are located between two adjacent tangential magnets to block magnetic short circuits.

[0016] Optionally, the rotor core is formed by stacking multiple layers of laminations, each layer of laminations having the permanent magnet slot and the built-in trapezoidal slot, and the corresponding positions of each layer are consistent.

[0017] A method for optimizing the rotor core of a permanent magnet synchronous motor, applied to the rotor core of a permanent magnet synchronous motor as described in any of the above claims, comprising:

[0018] An electromagnetic field finite element model of the rotor core is established, and the geometric parameters of the built-in trapezoidal slot are set as variables;

[0019] The parameters were iteratively simulated with the optimization objectives of minimizing the leakage magnetic coefficient of the magnetic isolation bridge and optimizing the sinusoidal waveform of the no-load back electromotive force.

[0020] The final geometric parameters of the built-in trapezoidal slot are determined based on the simulation results, so that the narrow neck enters a magnetic saturation state at the target operating point.

[0021] A permanent magnet synchronous motor includes a permanent magnet synchronous motor rotor core as described in any of the preceding claims.

[0022] As can be seen from the above technical solutions, the permanent magnet synchronous motor rotor core, optimization method and permanent magnet synchronous motor provided in this application embodiment are based on the core of having multiple permanent magnet slots in the circumferential direction of the rotor core. The magnetic isolation bridge structure between adjacent permanent magnet slots includes a built-in trapezoidal slot. At least one side wall of the trapezoidal slot is inclined, so that the magnetic isolation bridge forms a narrow neck near the center of the rotor and a wide base near the outer circle of the rotor. When the motor is working, the magnetic flux density of the narrow neck is higher than that of the wide base and is in a local magnetic saturation state, thereby blocking the leakage magnetic path.

[0023] This application addresses the shortcomings of existing technologies in several ways: First, it eliminates the need for non-magnetic shafts, additional coils, or non-magnetic materials. By optimizing the rotor core's magnetic isolation bridge and built-in trapezoidal slot structure, leakage flux suppression is achieved, simplifying the rotor core manufacturing process and reducing the cost and assembly difficulty associated with non-magnetic materials and additional coils. This makes it more suitable for large-scale mass production. Second, the narrow neck formed by the built-in trapezoidal slot blocks leakage flux paths through local magnetic saturation, preventing effective magnetic flux loss. Simultaneously, the rotor core maintains the compactness of its built-in tangential structure, preventing damage caused by additional components. The space occupied by the components ensures the advantages of high speed and large reluctance torque of the motor, while taking into account leakage flux control and power density, and solving the contradiction between leakage flux suppression and motor size and power density. Thirdly, the narrow neck magnetic saturation of this application effectively blocks leakage flux, allowing more magnetic flux generated by the magnets to enter the stator and rotor air gap, increasing the air gap magnetic flux density, while reducing the interference of leakage flux on the back EMF waveform, optimizing the sinusoidal nature of the back EMF, thereby improving the energy utilization rate of the magnets and the operating efficiency of the motor, avoiding the problems of magnet waste and efficiency loss caused by leakage flux in the prior art, and giving full play to the performance advantages of the built-in permanent magnet synchronous motor. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1 This is a structural diagram of a permanent magnet synchronous motor rotor core disclosed in an embodiment of this application;

[0026] Figure 2 This is a structural diagram of a permanent magnet synchronous motor rotor core with an internal trapezoidal slot, as disclosed in an embodiment of this application.

[0027] Figure 3This is a cloud map showing the magnetic flux density distribution of the motor under no-load conditions, as disclosed in an embodiment of this application.

[0028] Figure 4 This is a flowchart of a method for optimizing the rotor core of a permanent magnet synchronous motor disclosed in an embodiment of this application;

[0029] Figure 5 The image shows the no-load back EMF simulation curves of the motor before and after optimization as disclosed in the embodiments of this application. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] The following section introduces the solution proposed in this application. The technical solution is as follows, and details are provided below.

[0032] Figure 1 This is a structural diagram of a permanent magnet synchronous motor rotor core disclosed in an embodiment of this application.

[0033] Figure 2 This is a structural diagram of a permanent magnet synchronous motor rotor core with a built-in trapezoidal slot, as disclosed in an embodiment of this application.

[0034] like Figure 1 and Figure 2 As shown, the specific structure of the rotor core of this permanent magnet synchronous motor is as follows:

[0035] The rotor core has multiple permanent magnet slots arranged circumferentially to accommodate permanent magnets.

[0036] A magnetic isolation bridge structure is provided between adjacent permanent magnet slots, and the magnetic isolation bridge structure includes a built-in trapezoidal slot.

[0037] At least one side wall of the built-in trapezoidal groove is inclined, so that the magnetic bridge forms a narrow neck on the side near the center of the rotor and a wide base on the side near the outer circle of the rotor.

[0038] The narrow neck is configured such that the magnetic flux density is higher than that of the wide base when the motor is operating, thereby causing the magnetic isolation bridge to be in a state of local magnetic saturation during operation, so as to block the leakage magnetic path.

[0039] Specifically, the rotor core of the permanent magnet synchronous motor adopts a modular structure design to achieve magnet leakage flux suppression and magnetic circuit optimization. Its core structure and functions are as follows:

[0040] The rotor core has a cylindrical structure with multiple permanent magnet slots evenly arranged along its circumference. The number of permanent magnet slots is adapted to the number of poles of the motor (e.g., 6 pole motors correspond to 6 or 12 permanent magnet slots). The shape of the slot cavity matches the shape of the permanent magnet (e.g., rectangular or arc-shaped) to stably accommodate and fix the permanent magnet, ensuring that the permanent magnet does not shift when the motor operates at high speed. Between two adjacent permanent magnet slots, an integrally formed magnetic isolation bridge structure is formed. The magnetic isolation bridge structure is the solid part of the core connecting adjacent permanent magnet slots, and its core feature is the integration of... An internal trapezoidal slot is a groove structure formed inside the magnetic isolation bridge. The slot cavity outline includes at least one inclined sidewall (which can be unilaterally inclined or symmetrically inclined on both sides). Through the design of this inclined sidewall, the magnetic isolation bridge forms two functional sections distributed radially along the rotor: a narrow neck near the rotor center (shaft side) and a wide base near the rotor outer circle (air gap side). The cross-sectional area of ​​the narrow neck is smaller than that of the wide base, and the difference in size between the two is determined by the inclination angle and the depth of the internal trapezoidal slot.

[0041] During motor operation, when the magnetic flux generated by the permanent magnet is transmitted from the rotor core to the stator air gap, the magnetic flux is more concentrated in the narrow neck due to its smaller cross-sectional area. This results in a significantly higher magnetic flux density in the narrow neck compared to the wide base (finite element simulations have verified that the magnetic flux density in the narrow neck can reach 2.5T, while the magnetic flux density in the wide base is usually below 1.8T). When the magnetic flux density in the narrow neck reaches the magnetic saturation limit of the silicon steel sheets used in the rotor core, the magnetic isolation bridge enters a local magnetic saturation state. At this time, the magnetic resistance in the saturation region increases sharply, which can effectively block the leakage magnetic path formed by the magnetic flux along the magnetic isolation bridge (such as leakage of magnetic flux to the rotor center shaft side), forcing more magnetic flux to be transmitted towards the stator air gap, ensuring sufficient magnetic flux in the main magnetic circuit.

[0042] The slot width of the permanent magnet groove is adapted to the thickness of the permanent magnet. The distance between the bottom of the groove and the center of the rotor is determined according to the magnetic circuit design to ensure that the center of the magnetic pole of the permanent magnet corresponds to the center of the stator tooth after installation, so as to optimize the air gap magnetic flux distribution. The angle between the inclined sidewall of the built-in trapezoidal groove and the radial direction of the rotor can be determined by iterative optimization through finite element simulation. The preferred range is 15°-18°. At this angle, a balance can be achieved between the magnetic flux density saturation of the narrow neck and the strength of the magnetic bridge structure. This ensures that the narrow neck can stably enter the magnetic saturation state to block leakage magnetic flux, while avoiding excessive weakness of the narrow neck due to excessive inclination angle, which could cause centrifugal force damage when the motor is running at high speed. The minimum cross-sectional area of ​​the narrow neck is set according to the rated magnetic flux requirement of the motor. It is usually 1 / 3-1 / 2 of the cross-sectional area of ​​the wide base. For example, when the cross-sectional area of ​​the wide base is 6mm², the cross-sectional area of ​​the narrow neck is set to 2-3mm² to ensure that the difference in magnetic flux density meets the magnetic saturation triggering condition.

[0043] based on Figure 3The magnetic flux density distribution cloud diagram of the motor under no-load conditions shown directly demonstrates the core technical effect of the rotor core structure of this application:

[0044] As can be seen, the area around the built-in trapezoidal slot magnetic bridge is a deep red region, where the magnetic field can reach a saturation state of up to 2.5T. By setting a magnetic bridge near the inner circle of the shaft, the magnetic resistance of the magnetic circuit at the bottom of the magnet is increased, the direction of the magnetic lines of force is guided, the leakage magnetic path is blocked, the leakage magnetic field of the rotor magnetic circuit is reduced, and the magnetic lines of force of the magnet are maximized to enter the main magnetic circuit of the armature, providing more magnetomotive force to the stator. Ultimately, this effectively reduces the leakage magnetic field of the permanent magnet motor and improves the utilization rate of the magnet.

[0045] The embodiments of this application also provide further structural optimizations to the rotor core of the permanent magnet synchronous motor, as detailed below:

[0046] 1. Built-in trapezoidal groove sidewall tilt angle design

[0047] The sidewall inclination angle of the built-in trapezoidal groove is configured such that the magnetic resistance of the magnetic isolation bridge changes non-linearly in the radial direction, so as to guide the magnetic lines of force to converge toward the air gap direction.

[0048] Specifically, the inclination angle of the sidewall of the built-in trapezoidal slot is not a fixed value, but is adjusted in a gradient according to the radial position of the rotor. This causes the magnetic reluctance of the magnetic isolation bridge to change non-linearly in the radial direction. In the narrow neck region near the rotor center, the magnetic reluctance is significantly higher than that in the wide base region near the outer circumference of the rotor due to the larger inclination angle of the sidewall. This non-linear magnetic reluctance distribution can form a magnetic reluctance gradient: the high magnetic reluctance on the rotor center side hinders magnetic flux leakage to the shaft, while the low magnetic reluctance on the rotor outer circumference side guides magnetic flux to accumulate in the stator air gap, thereby further improving the magnetic flux utilization rate of the main magnetic circuit and reducing the ineffective loss of magnetic flux inside the rotor.

[0049] 2. Built-in trapezoidal groove with rounded bottom transition structure

[0050] The bottom of the built-in trapezoidal groove is provided with a circular arc transition structure for dispersing stress.

[0051] Specifically, the bottom of the built-in trapezoidal slot (i.e., the end of the slot cavity away from the outer circle of the rotor) is provided with an arc transition structure, the radius of which ranges from 0.3 to 0.8 mm. The function of this structure is to disperse the stress concentration of the magnetic isolation bridge during processing and operation. Since the rotor core is formed by lamination, if the bottom of the built-in trapezoidal slot is a right-angle structure, stress cracks are easily generated during stamping. Centrifugal force and magnetostrictive force during motor operation will also accumulate here, leading to structural damage. The arc transition structure can disperse stress over a larger area, ensuring the structural strength of the magnetic isolation bridge and extending the service life of the rotor core.

[0052] 3. Design of the width ratio between the magnetic bridge and the permanent magnet slot

[0053] The ratio of the width of the magnetic isolation bridge to the width of the permanent magnet groove decreases radially.

[0054] Specifically, the ratio of the width of the magnetic isolation bridge to the width of the permanent magnet slot decreases radially. In the wide base region near the outer circumference of the rotor, the ratio is 0.4-0.6; in the narrow neck region near the center of the rotor, this ratio drops to 0.1-0.2. This decreasing ratio design is adapted to the magnetic reluctance requirements of the magnetic isolation bridge: the wide base on the outer circumference side needs to have a certain width to ensure the overall rigidity of the core, while reducing magnetic reluctance through a larger width to guide magnetic flux; the narrow neck on the center side increases magnetic reluctance by reducing its width, and achieves leakage flux blocking in conjunction with magnetic saturation. The two work together to optimize the magnetic circuit and structural performance.

[0055] 4. Design of the minimum cross-sectional area of ​​the magnetic bridge

[0056] The magnetic isolation bridge has a minimum cross-sectional area portion, the size of which is configured to enter a magnetic saturation state when the motor is running under no-load conditions.

[0057] Specifically, the narrow neck of the magnetic isolation bridge is provided with a minimum cross-sectional area section, the size of which is configured to achieve magnetic saturation when the motor is running under no-load conditions. Specifically, the cross-sectional area of ​​the minimum cross-sectional area section is calculated and determined based on the saturation magnetic flux density of the rotor core silicon steel sheets (typically 2.0-2.5T) and the magnitude of the no-load magnetic flux. For example, when the no-load magnetic flux is 0.003Wb, if the saturation magnetic flux density of the silicon steel sheets is 2.3T, the area of ​​the minimum cross-sectional area section can be set to 1.3-1.5mm². This ensures that the motor can block leakage flux when no-loaded, avoiding magnetic flux waste under no-load conditions, and laying the foundation for magnetic circuit stability during load operation.

[0058] 5. The permanent magnet slot and the built-in trapezoidal slot are matched in position.

[0059] The permanent magnet slots are arranged tangentially, and the built-in trapezoidal slots are located between two adjacent tangential magnets to prevent magnetic short circuits.

[0060] Specifically, the permanent magnet slots are arranged tangentially, meaning that the extension direction of each permanent magnet slot is distributed along the tangential direction of the rotor circumference, so that the permanent magnets form a tangential magnetization mode. In this mode, the magnetic flux of adjacent permanent magnets can be superimposed in parallel, increasing the air gap magnetic flux density. The built-in trapezoidal slot is precisely located between two adjacent tangentially arranged permanent magnets, and its slot cavity centerline is aligned with the magnetic pole boundary line of the adjacent permanent magnets. This can directly block the magnetic short-circuit path between two tangential magnets (i.e., prevent magnetic flux from flowing directly from the N pole of one magnet to the S pole of the adjacent magnet), ensuring that the magnetic flux preferentially forms the main magnetic circuit through the stator air gap, further enhancing the leakage flux suppression effect.

[0061] 6. The stacked structure of the rotor core

[0062] The rotor core is made of multiple layers of laminations, each layer of laminations is provided with the permanent magnet slot and the built-in trapezoidal slot, and the corresponding positions of each layer are consistent.

[0063] Specifically, the rotor core is formed by stacking multiple layers of silicon steel laminations. Each lamination is integrally formed with the permanent magnet slot and the built-in trapezoidal slot through a stamping process. The position, shape, and size of the permanent magnet slot and the built-in trapezoidal slot on each lamination are completely consistent. During stacking, the core is positioned and fixed by pre-set core fasteners on the edge of the laminations. This stacking structure ensures that the magnetic circuit of the rotor core is continuous and uninterrupted along the axial direction, avoiding increased magnetic resistance or magnetic flux leakage caused by misalignment of the layers. At the same time, the multi-layer stacking design reduces eddy current losses in the rotor core, improves motor operating efficiency, and meets the design requirements of high power density and low loss for permanent magnet synchronous motors.

[0064] Assuming the permeability of the silicon steel sheets used in the stator and rotor cores of the motor is infinite (compared to the vacuum permeability of the air gap), according to the definition of leakage permeability and the energy method theory, we can obtain:

[0065]

[0066] In the formula: Represents leakage permeability; Represents vacuum permeability; This represents the magnetic shielding cross-sectional area and the magnetic shielding length. Theoretical analysis shows that the design selection of the magnetic shielding cross-sectional area and the magnetic shielding length are key factors affecting magnetic leakage of the magnet. Therefore, there exists a certain... The value is related to making the leakage flux of the permanent magnet motor's magnets zero or nearly zero, but it is necessary to comprehensively consider and verify the reliability and stability of the rotor core structure of the motor at its limit speed.

[0067] Based on this, this application sets multiple permanent magnet slots on the rotor core for fixing magnets, and sets an internal trapezoidal slot structure (i.e., a magnetic isolation bridge) between adjacent permanent magnet slots to prevent magnetic leakage. This magnetic isolation bridge can increase the magnetic flux saturation of the magnetic circuit at the bottom of the magnet, thereby blocking magnetic flux backflow, reducing bottom magnetic leakage, and maximizing the entry of the magnetic lines of force into the main magnetic circuit of the motor, providing more magnetomotive force to the main magnetic circuit and increasing the power density of the motor. When the number and width of the magnets are fixed, the geometry of the magnetic isolation bridge is key to improving the utilization rate of the magnets. Therefore, this application proposes an internal trapezoidal slot structure design for the rotor core of a permanent magnet synchronous motor: each internal trapezoidal slot consists of four geometric lines: two straight segments on the side, upper and lower straight segments, and an arc segment. Multiple core laminations are riveted together at core fasteners to form the rotor core. Figure 1 , 2 As shown; at the same time, the angle between the straight line segment H1 and the line connecting the rotor center point is defined as Ø, the arc segment of the built-in trapezoidal slot is defined as R1, the outer circle of the rotor core is defined as R0, and the break width of the outer circle of the core is defined as H2.

[0068] like Figure 1 As shown, the rotor core of the permanent magnet synchronous motor is symmetrically distributed in a circle with center O as the center, and is composed of multiple layers of silicon steel laminations stacked together (the laminations are positioned by a core snap-fit ​​structure to ensure axial alignment of corresponding structures in each layer). Multiple permanent magnet slots are evenly arranged along the circumference of the rotor core. The shape of the slot cavity is adapted to the shape of the permanent magnet (magnetic steel) to stably accommodate the permanent magnet, allowing the permanent magnets to be arranged tangentially or otherwise, achieving parallel magnetic flux connection between adjacent magnets to enhance the air gap magnetic flux density. The dimension H0 defines the radial distance from the key position of the permanent magnet slot to the rotor center O. This distance determines the radial depth of the permanent magnet slot on the rotor, directly affecting the magnetic circuit length between the permanent magnet and the rotor center and outer circle, providing a basic geometric constraint for the magnetic flux transmission path.

[0069] Between two adjacent permanent magnet slots, an integrally formed magnetic isolation bridge structure is provided; the magnetic isolation bridge has an integrated built-in trapezoidal slot (the structural feature clearly marked in the figure), and at least one side wall of the built-in trapezoidal slot is inclined. At the same time, the value of H2 directly determines the cross-sectional area of ​​the narrow neck (the smaller H2 is, the smaller the cross-sectional area of ​​the narrow neck), so that the magnetic isolation bridge forms a functional partition along the rotor radial direction (from the center 0 to the outer circle R0): the narrow neck near the rotor center (constrained by H2, with a smaller cross-sectional area), and the wide base near the outer circle of the rotor (with a larger cross-sectional area).

[0070] When the motor is running, the magnetic flux generated by the permanent magnet is transmitted at the magnetic isolation bridge. Because the cross-sectional area of ​​the narrow neck is smaller due to the restriction of H2, its magnetic flux density will be significantly higher than that of the wide base. This causes the narrow neck to enter the local magnetic saturation state first, thereby blocking the leakage magnetic path of the magnetic flux to the rotor center and forcing more magnetic flux to gather towards the stator air gap (the gap between the outer circle of the rotor and the stator), ensuring the effective utilization of the magnetic flux in the main magnetic circuit.

[0071] As can be seen from the above technical solutions, the permanent magnet synchronous motor rotor core, optimization method and permanent magnet synchronous motor provided in this application embodiment are based on the core of having multiple permanent magnet slots in the circumferential direction of the rotor core. The magnetic isolation bridge structure between adjacent permanent magnet slots includes a built-in trapezoidal slot. At least one side wall of the trapezoidal slot is inclined, so that the magnetic isolation bridge forms a narrow neck near the center of the rotor and a wide base near the outer circle of the rotor. When the motor is working, the magnetic flux density of the narrow neck is higher than that of the wide base and is in a local magnetic saturation state, thereby blocking the leakage magnetic path.

[0072] This application addresses the shortcomings of existing technologies in several ways: First, it eliminates the need for non-magnetic shafts, additional coils, or non-magnetic materials. By optimizing the rotor core's magnetic isolation bridge and built-in trapezoidal slot structure, leakage flux suppression is achieved, simplifying the rotor core manufacturing process and reducing the cost and assembly difficulty associated with non-magnetic materials and additional coils. This makes it more suitable for large-scale mass production. Second, the narrow neck formed by the built-in trapezoidal slot blocks leakage flux paths through local magnetic saturation, preventing effective magnetic flux loss. Simultaneously, the rotor core maintains the compactness of its built-in tangential structure, preventing damage caused by additional components. The space occupied by the components ensures the advantages of high speed and large reluctance torque of the motor, while taking into account leakage flux control and power density, and solving the contradiction between leakage flux suppression and motor size and power density. Thirdly, the narrow neck magnetic saturation of this application effectively blocks leakage flux, allowing more magnetic flux generated by the magnets to enter the stator and rotor air gap, increasing the air gap magnetic flux density, while reducing the interference of leakage flux on the back EMF waveform, optimizing the sinusoidal nature of the back EMF, thereby improving the energy utilization rate of the magnets and the operating efficiency of the motor, avoiding the problems of magnet waste and efficiency loss caused by leakage flux in the prior art, and giving full play to the performance advantages of the built-in permanent magnet synchronous motor.

[0073] The following describes a method for optimizing the rotor core of a permanent magnet synchronous motor provided in an embodiment of this application. The method described below is applied to the rotor core of a permanent magnet synchronous motor described above to optimize the rotor core of the permanent magnet synchronous motor described above. They can be referred to each other accordingly.

[0074] See Figure 4 , Figure 4 This is a flowchart of a method for optimizing the rotor core of a permanent magnet synchronous motor disclosed in an embodiment of this application.

[0075] like Figure 4 As shown, the method for optimizing the rotor core of a permanent magnet synchronous motor may include:

[0076] Step S1: Establish the electromagnetic field finite element model of the rotor core, and set the geometric parameters of the built-in trapezoidal slot as variables.

[0077] Specifically, based on the actual structural characteristics and material properties of the rotor core, an electromagnetic field finite element model is constructed. The material parameters of the rotor core in the model are set according to the actual silicon steel sheets used. The air gap lengths of the stator and rotor are set according to the optimization range and constraints of this embodiment. The air gap length ∂ of the motor is selected within the range of 0.25-0.5 mm. The size of the air gap length has a significant impact on the performance and operational reliability of the motor. If the air gap is too large, the air reluctance will increase significantly. To achieve the same air gap magnetic flux density, the excitation current needs to be increased substantially, leading to increased excitation losses and a significant decrease in the motor's power factor, resulting in increased motor temperature and performance degradation. To reduce the excitation current and improve the power factor, the air gap length should be minimized. However, if the air gap is too small, the air gap harmonic magnetic field and cogging torque will increase, leading to increased stray losses and noise in the motor. In this embodiment, the air gap length ∂ is selected as 0.3 mm.

[0078] Secondly, the core geometric parameters of the built-in trapezoidal slot were defined and set as simulation variables. The selection and definition of variables refer to the design of the rotor core structure in this application: First, the angle Ø between the straight segment H1 and the center point of the rotor core (the variable value range is set to 12°-20° based on the requirements of subsequent iterations); second, the ratio R1 / R0 of the radius R1 of the arc segment of the built-in trapezoidal slot to the radius R0 of the outer circle of the rotor core (the variable value range is set to 0.3-0.5); third, the ratio H1 / H0 of the straight segment H1 and the radial distance H0 from the key position of the permanent magnet slot to the rotor center (the variable value range is set to 0.5-0.7); fourth, the width H2 of the outer circle of the core (the variable value needs to meet the basic constraint of being greater than 1.5 times the air gap between the stator and rotor, so the value range is set to 0.45-0.8mm). The model simultaneously defines the collection areas of leakage flux and main flux (the leakage flux collection area is the side of the magnetic isolation bridge near the rotor center, and the main flux collection area is the air gap between the stator and rotor) to provide a data collection basis for subsequent optimization target calculations.

[0079] Step S2: With the optimization objectives of minimizing the leakage magnetic coefficient of the magnetic isolation bridge and optimizing the sinusoidal waveform of the no-load back electromotive force, parameter iterative simulation is performed.

[0080] Specifically, the quantitative evaluation criteria for the dual optimization objectives are first determined: for minimizing the leakage flux coefficient of the magnetic isolation bridge, the leakage flux coefficient is calculated as the ratio of the leakage flux at the magnetic isolation bridge to the total magnetic flux of the magnet. The objective is to reduce the leakage flux coefficient to the minimum, ensuring that more magnetic lines of force of the magnet enter the main magnetic circuit. For optimizing the sinusoidal waveform of the no-load back EMF, it is measured by the total harmonic distortion rate of the no-load back EMF. The total harmonic distortion rate is calculated as the ratio of the square root of the sum of the squares of the effective values ​​of each harmonic component to the effective value of the fundamental wave. The objective is to minimize the total harmonic distortion rate, ensuring the smooth operation of the motor.

[0081] Subsequently, finite element simulation software was used to perform parameter iterative simulation based on the model constructed in step S1. In the first round of simulation, sample points were selected evenly according to the value range of each variable (e.g., the included angle Ø was selected as 12°, 16°, and 20°, and the ratio R1 / R0 was selected as 0.3, 0.4, and 0.5, etc.). The leakage magnetic coefficient of the magnetic isolation bridge and the total harmonic distortion rate of the no-load back EMF were calculated for each sample point. In subsequent iterations, based on the simulation results of the previous round, the parameter range that makes the optimization objective better (e.g., the range with smaller leakage magnetic coefficient and lower total harmonic distortion rate) was further subdivided and sampled. At the same time, parameters that exceed the strength constraints of the rotor core structure were removed (e.g., H2 being too small, causing the magnetic isolation bridge stress to exceed the limit at the motor's limit speed). The iteration termination condition was set as "the change in leakage magnetic coefficient in two consecutive simulations is less than 0.5% and the change in the total harmonic distortion rate of the no-load back EMF is less than 0.3%", to ensure that the parameter optimization converges to a stable state and to avoid invalid iterations.

[0082] Step S3: Determine the final geometric parameters of the built-in trapezoidal slot based on the simulation results, so that the narrow neck enters the magnetic saturation state at the target operating point.

[0083] Specifically, candidate parameter groups are first selected from the simulation results after convergence in step S2: the selection criteria are that the leakage flux coefficient of the magnetic isolation bridge meets the leakage flux suppression requirements and the total harmonic distortion rate of the no-load back electromotive force meets the waveform sinusoidal requirements. At the same time, the rotor core magnetic flux density distribution corresponding to each candidate parameter group is viewed through the finite element model. The parameter group that the magnetic flux density of the narrow neck of the magnetic isolation bridge reaches the magnetic saturation pole of the silicon steel sheet of the rotor core is selected first to ensure that the narrow neck enters a local magnetic saturation state at the target operating point of the motor (such as rated speed, rated load condition), and the leakage flux path is blocked by the characteristic of the dramatic increase in magnetic reluctance in the saturation region.

[0084] Secondly, the rotor core structure strength of the candidate parameter group is verified: the motor is simulated to operate at its maximum speed, and the centrifugal stress of the magnetic bridge corresponding to the candidate parameter group is calculated to ensure that the stress value is less than the allowable stress of the silicon steel sheet, so as to avoid structural damage to the magnetic bridge when the motor is running at high speed.

[0085] Finally, combining simulation results and strength verification, the final geometric parameters of the built-in trapezoidal slot were determined: In this embodiment, the preferred included angle Ø = 16.8°, the ratio range 0.37 ≤ R1 / R0 ≤ 0.44, the ratio range 0.55 ≤ H1 / H0 ≤ 0.61, and the outer circle cut-off width H2 of the iron core satisfies greater than 1.5 times the air gap between the stator and rotor; under this parameter set, the magnetic flux emitted by the magnet can flow back to the magnet through the rotor iron core and stator iron core, forming an effective magnetic flux coupling with the stator winding, and the no-load air gap magnetic flux and back electromotive force of the motor both increase significantly. Figure 5As shown, compared to before optimization, the effective value of the no-load back EMF (rms) increases by about 12.9%, which can maintain the same output torque with a smaller input current, reduce winding copper losses and motor temperature rise, and the no-load back EMF waveform is smoother and has better sinusoidal characteristics, which helps to reduce cogging torque and air gap magnetic field harmonic distortion rate, improve motor control accuracy and positioning accuracy, and at the same time, while ensuring the structural strength of the rotor core, minimize magnet leakage, improve magnet utilization and motor efficiency.

[0086] As can be seen from the above technical solutions, the permanent magnet synchronous motor rotor core, optimization method and permanent magnet synchronous motor provided in this application embodiment are based on the core of having multiple permanent magnet slots in the circumferential direction of the rotor core. The magnetic isolation bridge structure between adjacent permanent magnet slots includes a built-in trapezoidal slot. At least one side wall of the trapezoidal slot is inclined, so that the magnetic isolation bridge forms a narrow neck near the center of the rotor and a wide base near the outer circle of the rotor. When the motor is working, the magnetic flux density of the narrow neck is higher than that of the wide base and is in a local magnetic saturation state, thereby blocking the leakage magnetic path.

[0087] This application addresses the shortcomings of existing technologies in several ways: First, it eliminates the need for non-magnetic shafts, additional coils, or non-magnetic materials. By optimizing the rotor core's magnetic isolation bridge and built-in trapezoidal slot structure, leakage flux suppression is achieved, simplifying the rotor core manufacturing process and reducing the cost and assembly difficulty associated with non-magnetic materials and additional coils. This makes it more suitable for large-scale mass production. Second, the narrow neck formed by the built-in trapezoidal slot blocks leakage flux paths through local magnetic saturation, preventing effective magnetic flux loss. Simultaneously, the rotor core maintains the compactness of its built-in tangential structure, preventing damage caused by additional components. The space occupied by the components ensures the advantages of high speed and large reluctance torque of the motor, while taking into account leakage flux control and power density, and solving the contradiction between leakage flux suppression and motor size and power density. Thirdly, the narrow neck magnetic saturation of this application effectively blocks leakage flux, allowing more magnetic flux generated by the magnets to enter the stator and rotor air gap, increasing the air gap magnetic flux density, while reducing the interference of leakage flux on the back EMF waveform, optimizing the sinusoidal nature of the back EMF, thereby improving the energy utilization rate of the magnets and the operating efficiency of the motor, avoiding the problems of magnet waste and efficiency loss caused by leakage flux in the prior art, and giving full play to the performance advantages of the built-in permanent magnet synchronous motor.

[0088] This application embodiment also provides a permanent magnet synchronous motor, wherein the permanent magnet synchronous motor rotor core structure is as follows:

[0089] The rotor core has multiple permanent magnet slots arranged circumferentially to accommodate permanent magnets.

[0090] A magnetic isolation bridge structure is provided between adjacent permanent magnet slots, and the magnetic isolation bridge structure includes a built-in trapezoidal slot.

[0091] At least one side wall of the built-in trapezoidal groove is inclined, so that the magnetic bridge forms a narrow neck on the side near the center of the rotor and a wide base on the side near the outer circle of the rotor.

[0092] The narrow neck is configured such that the magnetic flux density is higher than that of the wide base when the motor is operating, thereby causing the magnetic isolation bridge to be in a state of local magnetic saturation during operation, so as to block the leakage magnetic path.

[0093] Optionally, the refined structure of the permanent magnet synchronous motor rotor core can be described above.

[0094] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, structure, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, structure, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, structure, article, or apparatus that includes said element.

[0095] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0096] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A rotor core for a permanent magnet synchronous motor, characterized in that, include: The rotor core has multiple permanent magnet slots arranged circumferentially to accommodate permanent magnets. A magnetic isolation bridge structure is provided between adjacent permanent magnet slots, and the magnetic isolation bridge structure includes a built-in trapezoidal slot. At least one side wall of the built-in trapezoidal groove is inclined, so that the magnetic bridge forms a narrow neck on the side near the center of the rotor and a wide base on the side near the outer circle of the rotor. The narrow neck is configured such that the magnetic flux density is higher than that of the wide base when the motor is operating, thereby causing the magnetic isolation bridge to be in a state of local magnetic saturation during operation, so as to block the leakage magnetic path.

2. The rotor core according to claim 1, characterized in that, The sidewall inclination angle of the built-in trapezoidal groove is configured such that the magnetic resistance of the magnetic isolation bridge changes non-linearly in the radial direction, so as to guide the magnetic lines of force to converge toward the air gap direction.

3. The rotor core according to claim 1 or 2, characterized in that, The bottom of the built-in trapezoidal groove is provided with a circular arc transition structure for dispersing stress.

4. The rotor core according to claim 1, characterized in that, The ratio of the width of the magnetic isolation bridge to the width of the permanent magnet groove decreases radially.

5. The rotor core according to claim 1, characterized in that, The magnetic isolation bridge has a minimum cross-sectional area portion, the size of which is configured to enter a magnetic saturation state when the motor is running under no-load conditions.

6. The rotor core according to claim 1, characterized in that, The permanent magnet slots are arranged tangentially, and the built-in trapezoidal slots are located between two adjacent tangential magnets to prevent magnetic short circuits.

7. The rotor core according to claim 1, characterized in that, The rotor core is made of multiple layers of laminations, each layer of laminations is provided with the permanent magnet slot and the built-in trapezoidal slot, and the corresponding positions of each layer are consistent.

8. A method for optimizing the rotor core of a permanent magnet synchronous motor, applied to optimizing the rotor core of a permanent magnet synchronous motor as described in any one of claims 1 to 7, characterized in that, include: An electromagnetic field finite element model of the rotor core is established, and the geometric parameters of the built-in trapezoidal slot are set as variables; The parameters were iteratively simulated with the optimization objectives of minimizing the leakage magnetic coefficient of the magnetic isolation bridge and optimizing the sinusoidal waveform of the no-load back electromotive force. The final geometric parameters of the built-in trapezoidal slot are determined based on the simulation results, so that the narrow neck enters a magnetic saturation state at the target operating point.

9. A permanent magnet synchronous motor, characterized in that, Includes the rotor core of a permanent magnet synchronous motor as described in any one of claims 1 to 7.

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