Permanent magnet synchronous motor and optimization method of length of stator core thereof, and electronic device

Abstract

The present disclosure provides a permanent magnet synchronous motor, an optimization method of a stator core length thereof, and an electronic device. The method comprises: determining a target structure parameter of the permanent magnet synchronous motor; determining an initial length of a stator core of the permanent magnet synchronous motor according to an optimization model; and determining a value range of a final stator core length according to an experience coefficient range and the initial length. The experience coefficient range represents the influence degree of non-ideal influencing factors of a motor magnetic circuit on the performance of the permanent magnet synchronous motor. The optimization model comprises a target function and a constraint condition. The target function represents the corresponding relationship between the structure parameter of the permanent magnet synchronous motor and the tooth magnetic density of the stator core, and the optimization target of the target function is to make the tooth magnetic density of the stator core reach a specified maximum value. The constraint condition comprises that the length of the stator core is less than the length of a rotor core. The present disclosure can take into account the dual objectives of high efficiency characteristics and cost optimization of the motor.

Description

Technical Field

[0001] This disclosure relates to the field of motor technology, and in particular to a permanent magnet synchronous motor and a method for optimizing the length of its stator core, as well as electronic equipment. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) are widely used in electrical appliances, such as household refrigerator compressors, due to their advantages of high efficiency, high power factor, wide speed range, and strong resistance to demagnetization. In terms of permanent magnet material selection, to control material costs, motors typically use ferrite materials with low remanence (generally not exceeding 0.5T) as permanent magnets. Furthermore, to reduce the cost of the motor core material, motors often employ a rotor overhang structure (also known as a rotor cantilever structure or rotor axial extension structure). This involves reducing the stator core length while maintaining a stator and rotor of equal length, thus creating a rotor overhang structure motor. However, the selection of the stator core length lacks theoretical design guidance and relies on finite element simulation for optimization. Because the stator and rotor cores are of unequal length, predicting the electromagnetic performance of such motors requires 3D finite element simulation analysis, which in turn requires significant computational resources and time. Summary of the Invention

[0003] The technical problem to be solved by this disclosure is to overcome the above-mentioned defects in the prior art and to provide a permanent magnet synchronous motor and an optimization method and electronic device for the stator core length, so that the stator core length can meet both the high efficiency of the motor and achieve optimal cost-effectiveness.

[0004] This disclosure solves the above-mentioned technical problems through the following technical solution:

[0005] In a first aspect, a method for optimizing the stator core length is provided for optimizing the stator core length of a permanent magnet synchronous motor with the rotor core extending axially. The optimization method includes:

[0006] Determine the target structural parameters of the permanent magnet synchronous motor; the target structural parameters include: rotor core length;

[0007] The initial length of the stator core of the permanent magnet synchronous motor is determined according to the optimization model. The optimization model includes an objective function and constraints. The objective function characterizes the correspondence between the structural parameters of the permanent magnet synchronous motor and the magnetic flux density of the stator core teeth. The optimization objective of the objective function is to make the magnetic flux density of the stator core teeth reach the specified maximum value. The constraints include that the length of the stator core is less than the length of the rotor core.

[0008] The final range of values ​​for the stator core length is determined based on the empirical coefficient range and the initial length; wherein, the empirical coefficient range characterizes the degree of influence of non-ideal factors of the motor magnetic circuit on the performance of the permanent magnet synchronous motor, and the empirical coefficient range is determined by performing finite element simulation on the permanent magnet synchronous motor.

[0009] Optionally, the empirical coefficient ranges from 0.4 to 0.7;

[0010] And / or, the non-ideal influencing factors of the motor magnetic circuit include at least one of the following: magnetic leakage at the end of the permanent magnet, magnetic leakage of the rotor magnetic isolation bridge, magnetic reluctance within the permanent magnet, stator slotting effect, and end effect.

[0011] Optionally, the target structural parameters further include: permanent magnet remanence, stator slot pitch, and stator tooth width, and the objective function is:

[0012] ;

[0013] in, Indicates the length of the stator core. B represents the length of the rotor core. r τ represents the remanence of a permanent magnet. s t represents the stator slot pitch. w Indicates the stator tooth width. This indicates the magnetic flux density of the teeth in the stator core.

[0014] Optionally, the constraint conditions further include at least one of the following:

[0015] The slot opening of the permanent magnet synchronous motor is a semi-open slot, and the minimum thickness of the stator yoke of the permanent magnet synchronous motor is more than half the thickness of the stator teeth.

[0016] The ratio of permanent magnet thickness to radial air gap length is greater than or equal to 7;

[0017] The thickness of the rotor magnetic isolation bridge is less than or equal to 1 mm;

[0018] The minimum radial air gap length is less than or equal to 1 mm;

[0019] The difference between the length of the rotor core and the axial length of the permanent magnet is less than the difference threshold.

[0020] Secondly, a permanent magnet synchronous motor is provided, wherein the permanent magnet synchronous motor is a rotor core axially extended motor, including a permanent magnet, a rotor core and a stator core;

[0021] The range of values ​​for the stator core length of the permanent magnet synchronous motor is determined based on an empirical coefficient range and an initial length. The initial length is the stator core length determined according to the target structural parameters and optimization model of the permanent magnet synchronous motor. The target structural parameters include the rotor core length. The optimization model includes an objective function and constraints. The objective function characterizes the correspondence between the structural parameters of the permanent magnet synchronous motor and the magnetic flux density of the stator core teeth. The optimization objective of the objective function is to achieve a specified maximum value for the magnetic flux density of the stator core teeth. The constraints include that the stator core length is less than the rotor core length. The empirical coefficient range characterizes the degree of influence of non-ideal magnetic circuit factors on the performance of the permanent magnet synchronous motor, as determined by finite element simulation.

[0022] Optionally, the target structural parameters further include: permanent magnet remanence, stator slot pitch, and stator tooth width, and the objective function is:

[0023] ;

[0024] in, Indicates the length of the stator core. B represents the length of the rotor core. r τ represents the remanence of a permanent magnet. s t represents the stator slot pitch. w Indicates the stator tooth width. This indicates the magnetic flux density of the teeth in the stator core.

[0025] Optionally, the slot opening of the permanent magnet synchronous motor is a semi-open slot, and the minimum thickness of the stator yoke of the permanent magnet synchronous motor is more than half the thickness of the stator teeth.

[0026] And / or, the ratio of permanent magnet thickness to radial air gap length is greater than or equal to 7;

[0027] And / or, the thickness of the rotor magnetic bridge is less than or equal to 1 mm;

[0028] And / or, the minimum radial air gap length is less than or equal to 1 mm;

[0029] And / or, the difference between the length of the rotor core and the axial length of the permanent magnet is less than a difference threshold.

[0030] Thirdly, an electronic device is provided, including a memory, a processor, and a computer program stored in the memory and for running on the processor, wherein the processor executes the computer program to implement the method for optimizing the stator core length as described in the first aspect.

[0031] Fourthly, a computer-readable storage medium is provided, on which a computer program is stored, characterized in that, when the computer program is executed by a processor, it implements the method for optimizing the stator core length as described in the first aspect.

[0032] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of this disclosure.

[0033] The positive progress of this disclosure is that it provides a simple and effective method for optimizing the stator core length of a permanent magnet synchronous motor with an axially extended rotor core. The stator core length range determined by this method can achieve the dual goals of high motor efficiency and cost-effectiveness optimization. Attached Figure Description

[0034] Figure 1a A cross-sectional view of a permanent magnet synchronous motor provided as an exemplary embodiment of this disclosure;

[0035] Figure 1b A schematic diagram of the stator core of a permanent magnet synchronous motor provided as an exemplary embodiment of this disclosure;

[0036] Figure 1c A schematic diagram of the rotor core of a permanent magnet synchronous motor provided as an exemplary embodiment of this disclosure;

[0037] Figure 2 A flowchart illustrating a method for optimizing the length of a stator core, provided as an exemplary embodiment of this disclosure;

[0038] Figure 3a A schematic diagram of a simulation model of a permanent magnet synchronous motor provided for an exemplary embodiment of this disclosure;

[0039] Figure 3b for Figure 3a The BH curve of the simulation model of the permanent magnet synchronous motor is shown.

[0040] Figure 3c for Figure 3a A schematic diagram of the stator tooth section of the simulation model of the permanent magnet synchronous motor is shown.

[0041] Figure 3d for Figure 3a The stator tooth magnetic flux density of the simulation model of the permanent magnet synchronous motor shown is as l s Simulation results of the / α variation curve;

[0042] Figure 3e for Figure 3a The phase resistance and wire diameter of the simulation model of the permanent magnet synchronous motor shown are related to l. s Simulation results of the / α variation curve;

[0043] Figure 3f for Figure 3a The loss of the simulation model of the permanent magnet synchronous motor shown varies with l s Simulation results of the / α variation curve;

[0044] Figure 3g for Figure 3a The simulation model of the permanent magnet synchronous motor shown has a motor efficiency that varies with l s Simulation results of the / α variation curve;

[0045] Figure 3h for Figure 3a The simulation model of the permanent magnet synchronous motor shown is in different l s Simulation effect diagram of stator tooth magnetic flux density under / α;

[0046] Figure 3i for Figure 3a The simulation model of the permanent magnet synchronous motor shown is in different l s Simulation results of phase resistance at / α;

[0047] Figure 3j for Figure 3a The simulation model of the permanent magnet synchronous motor shown is in different l s Simulation effect diagram of wire diameter under / α;

[0048] Figure 3k for Figure 3a The simulation model of the permanent magnet synchronous motor shown is in different l s Simulation results of loss at / α;

[0049] Figure 3l for Figure 3a The simulation model of the permanent magnet synchronous motor shown is in different l s Simulation results of motor efficiency at / α;

[0050] Figure 4 This is a schematic diagram of the structure of an electronic device provided as an exemplary embodiment of the present disclosure. Detailed Implementation

[0051] The present disclosure is further illustrated below by way of embodiments, but the present disclosure is not limited to the scope of the embodiments described herein.

[0052] The prefixes such as "first" and "second" used in this disclosure are merely for distinguishing different descriptive objects and do not limit the position, order, priority, quantity, or content of the described objects. The use of ordinal numbers and other prefixes used to distinguish descriptive objects in this disclosure does not constitute a limitation on the described objects. The description of the described objects is given in the claims or the context of the embodiments, and should not be construed as an unnecessary limitation. Furthermore, in the description of this embodiment, unless otherwise stated, "multiple" means two or more.

[0053] Permanent magnet synchronous motors employing an axially extended rotor core (overhang structure), see [link / reference]. Figures 1a-1c The system comprises a permanent magnet 11, a rotor core 12, and a stator core 13. Under ideal assumptions of no magnetic leakage, uniform magnetic reluctance, and unsaturated magnetic materials, the magnetic flux lines 14 (red lines in the figure) are continuously distributed axially and pass radially perpendicularly through the air gap, with no end flux divergence. The ratio of the rotor core length to the stator core length in an Overhang structure permanent magnet synchronous motor is typically between 1.3 and 1.6, and the operating point of the stator core magnetic flux density is in the linear region of the BH curve. With the rotor remaining constant, the difference in motor material cost depends on the stator material cost, primarily the stator core material cost, which is directly proportional to the stator core length. Therefore, selecting the optimal stator core length can reduce the motor's material cost.

[0054] Research shows that continuously reducing the stator core length leads to a continued increase in the air gap magnetic flux density of the motor due to the magnetic concentration effect. This gradually increases the operating point of the stator core magnetic flux density, and the no-load back EMF of the motor decreases slowly. When the operating point of the stator core magnetic flux density exceeds the specified maximum value, the no-load back EMF of the motor decreases rapidly. Under constant load conditions, the phase current and the no-load back EMF of the motor are inversely proportional. Therefore, as the phase current of the motor first increases slowly and then rapidly, the copper loss of the motor first increases slowly and then rapidly. Regarding the variation law of the motor iron loss: when the operating point of the stator core magnetic flux density does not exceed its maximum operating magnetic flux density, the change in the motor iron loss is not significant. This is because: increasing the operating point of the stator core magnetic flux density within the range less than or equal to the maximum magnetic flux density will increase the iron loss density per unit volume of the stator core, but the volume of the stator core decreases accordingly. The effects of the two cancel each other out, and the impact on the motor efficiency is minimal. When the stator core's magnetic flux density operating point exceeds the maximum magnetic flux density, the change in stator core magnetic flux density slows down. Due to the reduction in the stator volume, the motor's iron losses gradually decrease. Therefore, when the stator core's magnetic flux density operating point does not exceed the specified maximum magnetic flux density, the motor's efficiency does not change significantly. However, when the stator core's magnetic flux density operating point exceeds the specified maximum magnetic flux density, the motor's efficiency gradually decreases because the change in copper losses is greater than that of iron losses. The specified maximum magnetic flux density is located near the knee point of the BH curve of the silicon steel sheet. In conclusion, under the condition of comparable motor efficiency, there is still room for reduction in the length of the stator core in existing technologies, which can further reduce costs and thus improve product competitiveness.

[0055] Based on this, embodiments of this disclosure provide a method for optimizing the stator core length, which is used to optimize the stator core length of a permanent magnet synchronous motor with an axially extending rotor core. See also Figure 2 The optimization method includes the following steps:

[0056] Step 201: Determine the target structural parameters of the permanent magnet synchronous motor.

[0057] The target structural parameters include at least one of the following: rotor core length, permanent magnet remanence, stator slot pitch, and stator tooth width.

[0058] Step 202: Determine the initial length of the stator core of the permanent magnet synchronous motor based on the optimization model.

[0059] The optimization model includes an objective function and constraints. The objective function characterizes the correspondence between the structural parameters of the permanent magnet synchronous motor and the magnetic flux density of the stator core teeth. The optimization objective of the objective function is to achieve the maximum value of the magnetic flux density of the stator core teeth. The constraints include that the length of the stator core is less than the length of the rotor core.

[0060] Step 203: Determine the range of values ​​for the final stator core length based on the empirical coefficient range and the initial length.

[0061] Among them, the empirical coefficient range characterizes the degree of influence of non-ideal factors in the motor magnetic circuit on the performance of the permanent magnet synchronous motor. The empirical coefficient range can be determined by finite element simulation of the permanent magnet synchronous motor.

[0062] In one embodiment, an empirical coefficient range is determined through extensive finite element simulations. This empirical coefficient range is applicable to motors of any size. Based on this empirical coefficient range, the optimal range of values ​​for the stator core length of a motor of any size can be obtained.

[0063] In practical applications, for motors of any size, a value can be selected from the empirical coefficient range as an empirical coefficient, and the product of the empirical coefficient and the initial length determines the optimal value of the stator core length. Alternatively, the value within the empirical coefficient range can be multiplied by the initial length to determine the range of values ​​for the stator core length, and a value within this range can be selected as the optimal value for the stator core length.

[0064] The value of the empirical coefficient is less than 1, so the final stator core length is less than the output result of the optimization model, which can reduce the material cost of the motor.

[0065] In this embodiment, a simple and effective method for optimizing the stator core length of a permanent magnet synchronous motor with an axially extended rotor core is provided. The stator core length range determined by this method can take into account both the high efficiency characteristics of the motor and the optimal cost-effectiveness.

[0066] In one embodiment, the objective function is:

[0067] ;or ;

[0068] in, Indicates the length of the stator core. B represents the length of the rotor core. r τ represents the remanence of a permanent magnet. s t represents the stator slot pitch. w Indicates the stator tooth width. This represents the magnetic flux density of the stator core teeth. The structural optimization coefficient is determined based on the magnetic flux density of the stator core teeth and the target structural parameters of the permanent magnet synchronous motor.

[0069] The remanence of a permanent magnet is determined based on the material properties of the permanent magnet.

[0070] The magnetic flux density of the stator core teeth can be determined by the following formula:

[0071] Magnetic flux of stator teeth / cross-sectional area of ​​stator teeth.

[0072] Reducing the stator core length is equivalent to increasing the cross-sectional area of ​​the stator teeth, thus increasing the magnetic flux density of the teeth. In this embodiment, the magnetic flux density of the teeth is adjusted to achieve the specified / target value by controlling the stator core length.

[0073] The principles of the embodiments of this disclosure are described below:

[0074] In this embodiment, based on the flux continuity theorem and Ampere's circuital law, and combined with the given structural parameters of the Overhang structure permanent magnet synchronous motor, the required stator core length to achieve the target value of the stator core tooth magnetic flux density is calculated. The target value is the stator core magnetic flux density reaching the specified / target maximum magnetic flux density value B. max .

[0075] In the magnetic circuit calculation of a permanent magnet motor, the permanent magnet can be equivalently represented as a constant magnetic flux source and a constant internal reluctance magnetic flux source connected in parallel. The magnetic flux source can be expressed as:

[0076] ;

[0077] The internal magnetic reluctance is:

[0078] ;

[0079] in, B is a magnetic flux source. r For the remanence of a permanent magnet, A m w is the cross-sectional area of ​​the magnetic flux per pole of the permanent magnet. m l is the width of the permanent magnet. r h is the length of the rotor core. m The thickness of the permanent magnet is μ. m Let be the permeability of the permanent magnet. For a permanent magnet synchronous motor, the leakage flux through the rotor magnetic isolation bridge on both sides of a single permanent magnet can be expressed as:

[0080] ;

[0081] in, B is the leakage flux of the rotor magnetic bridge. sat The saturation magnetic flux density of the core material is typically 2T, w b The thickness of the rotor magnetic isolation bridge.

[0082] Ignoring stator slotting and end effects, and assuming that the magnetic flux generated by the permanent magnet enters the stator core entirely through the air gap between the stator and rotor, the magnetic reluctance of the air gap can be expressed as:

[0083] ;

[0084] in, For the magnetic reluctance of the air gap, A gh is the cross-sectional area of ​​the air gap magnetic surface. g r is the radial length of the air gap. g Let α be the radius corresponding to the air gap, p be the pole pair, and α be the radius. p denoted as the polar arc coefficient of the permanent magnet. Stator core length, is the vacuum permeability.

[0085] Neglecting the magnetic reluctance of the stator and rotor cores, the leakage flux of the rotor magnetic isolation bridge, and the internal resistance of the permanent magnet, the air gap flux under ideal conditions It can be represented as:

[0086] .

[0087] When the number of pole pairs in the motor is small, the magnetic focusing effect of the built-in permanent magnet synchronous motor is not significant in the xoy plane. That is, the width of the permanent magnet within one pole pitch range is equivalent to the length of the air gap arc within one pole pitch range. Therefore, neglecting the end effect, the air gap magnetic flux density can be expressed as:

[0088] .

[0089] When the centerline of the permanent magnet is aligned with the centerline of a stator tooth, the air gap magnetic flux within one slot pitch is:

[0090] ;

[0091] ;

[0092] in, τ is the air gap magnetic flux within one slot pitch. s N is the stator slot pitch. s This represents the number of stator slots.

[0093] The magnetic flux entering the stator teeth is Ignoring stator slot leakage flux, meaning that all the air gap magnetic flux within one slot pitch enters the stator teeth, i.e. , can be obtained or To ensure the stator tooth magnetic flux density B t Reaching B max The stator core length satisfies:

[0094] .

[0095] The above formula does not take into account the leakage flux at the end of the permanent magnet, the leakage flux of the rotor magnetic bridge, the magnetic reluctance inside the permanent magnet, the stator slotting effect and the end effect, etc., in the derivation process, thus enabling a rapid estimation of the stator core length.

[0096] In one embodiment,

[0097] Non-ideal factors affecting the magnetic circuit of a motor include at least one of the following: magnetic leakage at the end of the permanent magnet, magnetic leakage from the rotor magnetic bridge, magnetic reluctance within the permanent magnet, stator slotting effect, and end effect.

[0098] In this embodiment, the leakage flux at the end of the permanent magnet, the leakage flux of the rotor magnetic bridge, the magnetic reluctance inside the permanent magnet, the stator slotting effect, and the end effect are considered, so that the optimized stator core length is more in line with the actual application scenario.

[0099] In one embodiment, the range of the empirical coefficient k is determined to be 0.4 to 0.7 through finite element simulation.

[0100] In one embodiment, the constraint also includes at least one of the following:

[0101] The slot opening of the permanent magnet synchronous motor is a semi-open slot, and the minimum thickness of the stator yoke of the permanent magnet synchronous motor is more than half the thickness of the stator teeth.

[0102] The ratio of the thickness of the permanent magnet to the radial air gap length is greater than or equal to 7.

[0103] The thickness of the rotor magnetic isolation bridge is less than or equal to 1 mm;

[0104] The minimum radial air gap length is less than or equal to 1 mm;

[0105] The difference between the rotor core length and the axial length of the permanent magnet is less than the difference threshold.

[0106] The difference threshold can be set according to the actual situation, for example, 0.2m. The difference between the rotor core length and the axial length of the permanent magnet is less than the difference threshold, that is, the rotor core length is equal to or slightly greater than the axial length of the permanent magnet.

[0107] The following is based on Figure 3a Taking the 6-pole 9-slot permanent magnet synchronous motor with an overhang rotor structure as an example, the optimization method of this embodiment will be further explained.

[0108] See Figure 3a The original design parameters of the permanent magnet synchronous motor included: the permanent magnet was an internal crescent shape, and the stator core length l. s The rotor core length is 26mm. r The axial length of the permanent magnet is 36mm. m It is 36mm, which meets the requirements of l r =l m The thickness h of the permanent magnet m The air gap radial length is 5mm, and the air gap radial length is h. g It is 0.5mm, which satisfies h m / h g≥7, the thickness w of the rotor magnetic bridge b The thickness is 0.6 mm, the air gap radius is 30.83 mm, and the stator tooth width is t. w The stator slot pitch is 7.55mm. s The diameter is 21.52 mm. The stator slot is a semi-open slot with a slot width of 2.5 mm. The number of coil turns is 245, and the phase resistance is 10.57 Ω. The stator and rotor cores are made of 50JN800, and their BH curves are as follows. Figure 3b As shown, its saturation magnetic flux density is B. sat The maximum design magnetic flux density B of the stator core tooth section is 2T. max It is 1.7T.

[0109] Example 1: Remanence B of a permanent magnet r It is 0.39T.

[0110] k is taken as 0.4~0.7, according to the formula provided in this embodiment. The calculated value of the stator core length is 9.4 mm to 16.5 mm.

[0111] A three-dimensional finite element simulation model of a permanent magnet synchronous motor with different stator core lengths was established, with the stator core length varying from 6 to 26 mm in 1 mm increments. s The value of / α ranges from 0.25 to 1.10. Among them, A cross-section is drawn at half the height of the stator teeth in the finite element simulation model. The magnetic flux through this cross-section is divided by the cross-sectional area to obtain the magnetic flux density of the stator teeth. See [link to relevant documentation]. Figure 3c In the diagram, region A represents the cross-section of the stator core teeth. For the no-load condition, see [reference needed]. Figure 3d The figure shows the magnetic flux density of the stator teeth as a function of l. s The curve showing the change in / α. From... Figure 3d As can be seen from l s / α is 0.47 (stator core length is 11mm), the maximum magnetic flux density of the stator teeth reaches approximately 1.7T, while l s / α is 1.1 (the original stator core length was 26mm), corresponding to a maximum stator tooth magnetic flux density of approximately 1.1T. s With α = 0.85 (stator core length = 20mm), the maximum magnetic flux density of the stator teeth is approximately 1.3T.

[0112] When the stator core length decreases, the no-load back EMF of the motor also decreases. Based on the original design, the number of coil turns is adjusted to keep the fundamental amplitude of the no-load back EMF constant under different stator core lengths. With the stator slot fill factor unchanged, increasing the number of coil turns reduces the wire diameter and increases the phase resistance. The wire diameter and phase resistance increase with increasing length. s The curve of / α variation is as follows Figure 3e As shown, it can be seen that l s When / α is less than 0.47, the phase resistance begins to increase rapidly.

[0113] Under a load of 0.23 Nm, the motor loss increases with l s The curve of / α variation is as follows Figure 3f As shown, it can be seen that with l s As / α decreases, copper loss initially increases slowly and then rapidly, with the inflection point appearing at l. s / α is 0.47; the iron loss of the motor changes slowly at first, then decreases rapidly. Under loads of 0.17 Nm and 0.23 Nm, the efficiency of the motor increases with l s The curve of / α variation is as follows Figure 3g As shown, under a load of 0.23 Nm, the motor efficiency of the model with a stator core length of 26 mm and 20 mm is comparable within the stator core range (11~16.5 mm) determined in this embodiment; under a load of 0.17 Nm, the motor efficiency of the model with a stator core length of 26 mm and 20 mm is comparable within the stator core range (9~16.5 mm) determined in this embodiment.

[0114] When l s When / α is less than 0.4 (stator core length less than 9mm), although the cost of the stator core decreases, the efficiency of the motor decreases by more than 2%; when l s When / α is greater than 0.7 (stator core length is greater than 16.5mm), although the motor efficiency is comparable, the stator core cost is higher.

[0115] With identical rotors, the difference in motor material costs depends on the stator core material cost and winding cost, both of which are proportional to the stator core length. Through the aforementioned finite element simulation and analysis of the simulation data, it is evident that the stator core length determined by the method in this embodiment is shorter than that determined by the traditional design method. Therefore, the motor material cost corresponding to the method in this embodiment is lower than that corresponding to the motor material cost using the traditional design method. In summary, the stator core length range determined by the method in this embodiment satisfies both high motor efficiency and optimal cost-effectiveness.

[0116] Example 2: Remanence B of a permanent magnet r It is 0.46T.

[0117] k takes values ​​between 0.4 and 0.7, according to the above formula. The calculated value of the stator core length is 11 mm to 19 mm.

[0118] A three-dimensional finite element simulation model of a permanent magnet synchronous motor with different stator core lengths was established, with the stator core lengths being 9mm, 11mm, 13mm, 16mm, 20mm, and 26mm respectively. s The values ​​of / α are 0.32, 0.4, 0.47, 0.58, 0.72, and 0.94. A cross-section is drawn at 1 / 2 height of the stator teeth in the finite element simulation model. The magnetic flux through this cross-section is divided by the cross-sectional area to obtain the magnetic flux density of the stator teeth. Under no-load conditions, different l s / α lower stator tooth magnetic flux density value as follows Figure 3h As shown in the figure, it can be seen that in l s / α is 0.58 (stator core length is 16mm), the stator tooth magnetic flux density reaches 1.72T, while l s / α is 0.94 (the original stator core length was 26mm), corresponding to a maximum stator tooth magnetic flux density of approximately 1.37T; when l s With a value of α = 0.72 (stator core length = 20 mm), the maximum value of the stator tooth magnetic flux density is approximately 1.56 T.

[0119] When the stator core length decreases, the no-load back EMF of the motor also decreases. Based on the original design, the number of coil turns is adjusted to keep the fundamental amplitude of the no-load back EMF constant under different stator core lengths. With the stator slot fill factor unchanged, increasing the number of coil turns and decreasing the wire diameter increases the phase resistance. Different l s The phase resistance and wire diameter of / α are respectively as follows: Figure 3i , Figure 3j As shown.

[0120] Under a load of 0.23 Nm, different l s Motor losses at / α are as follows Figure 3k As shown, it can be seen that due to the high remanence of permanent magnets, in l s When / α is large, the iron loss of the motor is higher than the copper loss. As l s As / α decreases, the iron loss of the motor decreases, while the copper loss increases. Under a load of 0.23 Nm, different l s Motor efficiency at / α is as follows Figure 3l As shown, it can be seen that the motor efficiencies within the stator core range (11mm, 13mm, 16mm) determined by the method of this embodiment are all higher than the motor efficiencies of the models with stator core lengths of 26mm and 20mm.

[0121] Since the rotors are identical, the material cost difference in the motors depends on the stator core material cost and winding cost, both of which are proportional to the stator core length. The stator core length determined by the method in this embodiment is shorter than that determined by traditional design methods. Therefore, the material cost of the motor based on the method in this embodiment is lower than that based on traditional design methods. In summary, the stator core length range determined by the method in this embodiment satisfies both high motor efficiency and optimal cost-effectiveness.

[0122] This disclosure also provides a permanent magnet synchronous motor, which is a rotor core axially extended motor, including a permanent magnet, a rotor core and a stator core;

[0123] The range of values ​​for the stator core length of the permanent magnet synchronous motor is determined based on an empirical coefficient range and an initial length, where the initial length is the stator core length determined according to the target structural parameters and optimization model of the permanent magnet synchronous motor. The specific process for determining the stator core length can be found in any of the above embodiments and will not be repeated here.

[0124] The target structural parameters include the rotor core length; the optimization model includes an objective function and constraints. The objective function characterizes the correspondence between the structural parameters of the permanent magnet synchronous motor and the magnetic flux density of the stator core teeth, and the optimization objective of the objective function is to make the magnetic flux density of the stator core teeth reach a specified maximum value. The constraints include that the stator core length is less than the rotor core length; the empirical coefficient range characterizes the degree of influence of non-ideal factors of the motor magnetic circuit on the performance of the permanent magnet synchronous motor, as determined by finite element simulation.

[0125] Optionally, the objective function is:

[0126] ;

[0127] in, Indicates the length of the stator core. B represents the length of the rotor core. r τ represents the remanence of a permanent magnet. s t represents the stator slot pitch. w Indicates the stator tooth width. The value represents the magnetic flux density of the stator core teeth, and k is an empirical coefficient representing the influence of non-ideal factors in the motor's magnetic circuit on the permanent magnet synchronous motor.

[0128] Optionally, the empirical coefficient ranges from 0.4 to 0.7.

[0129] Optionally, the slot opening of the permanent magnet synchronous motor is a semi-open slot, and the minimum thickness of the stator yoke of the permanent magnet synchronous motor is more than half the thickness of the stator teeth.

[0130] And / or, the ratio of permanent magnet thickness to radial air gap length is greater than or equal to 7;

[0131] And / or, the thickness of the rotor magnetic bridge is less than or equal to 1 mm;

[0132] And / or, the minimum radial air gap length is less than or equal to 1 mm;

[0133] And / or, the difference between the length of the rotor core and the axial length of the permanent magnet is less than a difference threshold.

[0134] Corresponding to the aforementioned embodiments of the method for optimizing stator core length, this disclosure also provides embodiments of a system for optimizing stator core length.

[0135] This stator core length optimization system is used to optimize the stator core length of a permanent magnet synchronous motor with an axially extended rotor core. The optimization system includes:

[0136] The first determining module is used to determine the target structural parameters of the permanent magnet synchronous motor; the target structural parameters include: rotor core length;

[0137] An optimization module is used to determine the initial length of the stator core of the permanent magnet synchronous motor according to an optimization model. The optimization model includes an objective function and constraints. The objective function characterizes the correspondence between the structural parameters of the permanent magnet synchronous motor and the magnetic flux density of the stator core teeth. The optimization objective of the objective function is to make the magnetic flux density of the stator core teeth reach a specified maximum value. The constraints include that the length of the stator core is less than the length of the rotor core.

[0138] The optimization module is further configured to determine the final range of values ​​for the stator core length based on the empirical coefficient range and the initial length; wherein the empirical coefficient range characterizes the degree of influence of non-ideal magnetic circuit factors on the performance of the permanent magnet synchronous motor, as determined by finite element simulation of the permanent magnet synchronous motor.

[0139] Optionally, the empirical coefficient ranges from 0.4 to 0.7;

[0140] And / or, the non-ideal influencing factors of the motor magnetic circuit include at least one of the following: magnetic leakage at the end of the permanent magnet, magnetic leakage of the rotor magnetic isolation bridge, magnetic reluctance within the permanent magnet, stator slotting effect, and end effect.

[0141] Optionally, the target structural parameters further include: permanent magnet remanence, stator slot pitch, and stator tooth width, and the objective function is:

[0142] ;

[0143] in, Indicates the length of the stator core. B represents the length of the rotor core. r τ represents the remanence of a permanent magnet. s t represents the stator slot pitch. w Indicates the stator tooth width. This indicates the magnetic flux density of the teeth in the stator core.

[0144] Optionally, the constraint conditions further include at least one of the following:

[0145] The slot opening of the permanent magnet synchronous motor is a semi-open slot, and the minimum thickness of the stator yoke of the permanent magnet synchronous motor is more than half the thickness of the stator teeth.

[0146] The ratio of permanent magnet thickness to radial air gap length is greater than or equal to 7;

[0147] The thickness of the rotor magnetic isolation bridge is less than or equal to 1 mm;

[0148] The minimum radial air gap length is less than or equal to 1 mm;

[0149] The difference between the length of the rotor core and the axial length of the permanent magnet is less than the difference threshold.

[0150] For the system embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to in the description of the method embodiments. The system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this disclosure according to actual needs.

[0151] Figure 4 This is a schematic diagram of the structure of an electronic device according to an example embodiment of the present disclosure. The electronic device includes a memory, a processor, and a computer program stored in the memory and used to run on the processor. When the processor executes the computer program, it implements the method described in any of the above embodiments. Figure 4 The electronic device 40 shown is merely an example and should not impose any limitation on the functionality and scope of use of the embodiments disclosed herein.

[0152] like Figure 4 As shown, the electronic device 40 can be manifested as a general-purpose computing device, such as a server device. The components of the electronic device 40 may include, but are not limited to: at least one processor 41, at least one memory 42, and a bus 43 connecting different system components (including memory 42 and processor 41).

[0153] Bus 43 includes a data bus, an address bus, and a control bus.

[0154] The memory 42 may include volatile memory, such as random access memory (RAM) 421 and / or cache memory 422, and may further include read-only memory (ROM) 423.

[0155] The memory 42 may also include a program tool 425 (or utility) having a set (at least one) program module 424, such program module 424 including but not limited to: an operating system, one or more application programs, other program modules, and program data, each or some combination of these examples may include an implementation of a network environment.

[0156] The processor 41 performs various functional applications and data processing, such as the methods provided in any of the above embodiments, by running computer programs stored in the memory 42.

[0157] Electronic device 40 can also communicate with one or more external devices 44 (e.g., keyboard, pointing device, etc.). This communication can be performed via input / output (I / O) interface 45. Furthermore, electronic device 40 can also communicate with one or more networks (e.g., local area network (LAN), wide area network (WAN), and / or public network, such as the Internet) via network adapter 46. As shown, network adapter 46 communicates with other modules of electronic device 40 via bus 43. It should be understood that, although not shown in the figure, other hardware and / or software modules can be used in conjunction with electronic device 40, including but not limited to: microcode, device drivers, redundant processors, external disk drive arrays, RAID (disk array) systems, tape drives, and data backup storage systems.

[0158] It should be noted that although several units / modules or sub-units / modules of the electronic device have been mentioned in the detailed description above, this division is merely exemplary and not mandatory. In fact, according to embodiments of this disclosure, the features and functions of two or more units / modules described above can be embodied in one unit / module. Conversely, the features and functions of one unit / module described above can be further divided and embodied by multiple units / modules.

[0159] This disclosure also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method provided in any of the above embodiments.

[0160] The readable storage medium may be more specifically adopted, including but not limited to: portable disk, hard disk, random access memory, read-only memory, erasable programmable read-only memory, optical storage device, magnetic storage device, or any suitable combination thereof.

[0161] This disclosure also provides a computer program product, including a computer program that, when executed by a processor, implements the method described in any of the above embodiments.

[0162] The program code for executing the computer program product of this disclosure can be written in any combination of one or more programming languages, and the program code can be executed entirely on a user device, partially on a user device, as a stand-alone software package, partially on a user device and partially on a remote device, or entirely on a remote device.

[0163] While specific embodiments of this disclosure have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of this disclosure is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of this disclosure, but all such changes and modifications fall within the scope of protection of this disclosure.

Claims

1. A method for optimizing the length of a stator core, characterized in that, The method for optimizing the stator core length of a permanent magnet synchronous motor with axial extension of the rotor core includes: Determine the target structural parameters of the permanent magnet synchronous motor; the target structural parameters include: rotor core length, permanent magnet remanence, stator slot pitch, and stator tooth width; The initial length of the stator core of the permanent magnet synchronous motor is determined according to the optimization model. The optimization model includes an objective function and constraints. The objective function characterizes the correspondence between the structural parameters of the permanent magnet synchronous motor and the magnetic flux density of the stator core teeth. The optimization objective of the objective function is to achieve a specified maximum value for the magnetic flux density of the stator core teeth. The constraints include that the stator core length is less than the rotor core length. The objective function is: ;in, Indicates the length of the stator core. B represents the length of the rotor core. r τ represents the remanence of a permanent magnet. s t represents the stator slot pitch. w Indicates the stator tooth width. Indicates the magnetic flux density of the teeth in the stator core; Based on the range of empirical coefficients and the initial length, the range of values ​​for the final stator core length is determined; wherein, the range of empirical coefficients characterizes the degree of influence of non-ideal magnetic circuit factors on the performance of the permanent magnet synchronous motor, as determined by finite element simulation of the permanent magnet synchronous motor.

2. The method for optimizing the length of the stator core according to claim 1, characterized in that, The empirical coefficient ranges from 0.4 to 0.

7.

3. The method for optimizing the length of the stator core according to claim 1, characterized in that, The non-ideal factors affecting the motor magnetic circuit include at least one of the following: magnetic leakage at the end of the permanent magnet, magnetic leakage from the rotor magnetic bridge, magnetic reluctance within the permanent magnet, stator slotting effect, and end effect.

4. The method for optimizing the length of the stator core according to claim 1, characterized in that, The constraints also include at least one of the following: The slot opening of the permanent magnet synchronous motor is a semi-open slot, and the minimum thickness of the stator yoke of the permanent magnet synchronous motor is more than half the thickness of the stator teeth. The ratio of permanent magnet thickness to radial air gap length is greater than or equal to 7; The thickness of the rotor magnetic isolation bridge is less than or equal to 1 mm; The minimum radial air gap length is less than or equal to 1 mm; The difference between the length of the rotor core and the axial length of the permanent magnet is less than the difference threshold.

5. A permanent magnet synchronous motor, characterized in that, The permanent magnet synchronous motor is a rotor core axially extended motor, including permanent magnets, rotor core and stator core; The range of values ​​for the stator core length of the permanent magnet synchronous motor is determined based on an empirical coefficient range and an initial length. The initial length is the stator core length determined according to the target structural parameters and optimization model of the permanent magnet synchronous motor. The target structural parameters include: rotor core length, permanent magnet remanence, stator slot pitch, and stator tooth width. The optimization model includes an objective function and constraints. The objective function characterizes the correspondence between the structural parameters of the permanent magnet synchronous motor and the magnetic flux density of the stator core teeth. The optimization objective of the objective function is to achieve a specified maximum value for the magnetic flux density of the stator core teeth. The constraints include that the stator core length is less than the rotor core length. The empirical coefficient range characterizes the degree of influence of non-ideal magnetic circuit factors on the performance of the permanent magnet synchronous motor, determined through finite element simulation. The objective function is: ;in, Indicates the length of the stator core. B represents the length of the rotor core. r τ represents the remanence of a permanent magnet. s t represents the stator slot pitch. w Indicates the stator tooth width. This indicates the magnetic flux density of the teeth in the stator core.

6. The permanent magnet synchronous motor according to claim 5, characterized in that, The empirical coefficient ranges from 0.4 to 0.

7.

7. The permanent magnet synchronous motor according to claim 5 or 6, characterized in that, The slot opening of the permanent magnet synchronous motor is a semi-open slot, and the minimum thickness of the stator yoke of the permanent magnet synchronous motor is more than half the thickness of the stator teeth. And / or, the ratio of permanent magnet thickness to radial air gap length is greater than or equal to 7; And / or, the thickness of the rotor magnetic bridge is less than or equal to 1 mm; And / or, the minimum radial air gap length is less than or equal to 1 mm; And / or, the difference between the length of the rotor core and the axial length of the permanent magnet is less than a difference threshold.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and for running on the processor, characterized in that, When the processor executes the computer program, it implements the method for optimizing the stator core length as described in any one of claims 1 to 4.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the method for optimizing the stator core length as described in any one of claims 1 to 4.

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