Flat wire winding permanent magnet synchronous motor hybrid thermal network modeling method

Abstract

The application discloses a kind of flat wire winding permanent magnet synchronous motor hybrid thermal network modeling method, belong to the temperature field analysis design technical field of permanent magnet synchronous motor.Utilize two-dimensional finite element analysis software FEMM to calculate the detailed temperature distribution in the radial direction of motor, again in combination with thermal resistance network method to winding end space area and motor axial heat dissipation are modeled, on the basis of guaranteeing calculation precision, reduce model calculation time.The application has the advantages of high calculation precision, high calculation efficiency, compared with three-dimensional transient field finite element analysis, the model has faster calculation speed.On the other hand, compared with the traditional lumped parameter network model, the model can show more abundant permanent magnet motor temperature field results.

Description

Technical Field

[0001] This invention relates to a hybrid thermal network modeling method for a flat wire winding permanent magnet synchronous motor, belonging to the field of temperature field analysis and design technology for permanent magnet synchronous motors. Background Technology

[0002] Permanent magnet motors (PMMs) have been widely used in industrial fields, such as home appliances and electric vehicles, due to their advantages of high power density, high efficiency, and high power factor. However, the performance of PMMs is often limited by thermal constraints because the properties of the materials (copper, insulation, and soft / hard magnetic materials) are affected by temperature. For example, excessive temperature rise can damage the wire insulation and cause irreversible demagnetization of the permanent magnets, leading to severe degradation of motor performance. Therefore, accurate and detailed thermal analysis of PMMs is crucial for their design optimization and safe operation.

[0003] For thermal analysis of permanent magnet motors, three-dimensional modeling is unavoidable because heat conduction within a permanent magnet motor occurs in both axial and radial directions. Traditional simulations of permanent magnet motor temperature rise often employ three-dimensional thermal finite element models and computational fluid dynamics (CFD). However, while these two methods offer high accuracy, they are computationally expensive. Other methods for motor thermal analysis include lumped parameter thermal network methods and analytical methods, which offer shorter computation times but require improvement in accuracy. Summary of the Invention

[0004] This invention proposes a hybrid thermal network modeling method for a flat wire winding permanent magnet synchronous motor. The method uses the two-dimensional finite element analysis software FEMM to calculate the detailed temperature distribution in the radial direction of the motor, and combines the thermal resistance network method to model the spatial region at the winding end and the axial heat dissipation of the motor. This reduces the model calculation time while ensuring calculation accuracy, and solves the problems existing in the prior art.

[0005] A method for modeling the hybrid thermal network of a flat-wire winding permanent magnet synchronous motor includes the following steps:

[0006] Step 1: Based on the structure, materials and geometric parameters of the motor, establish a radial 2D electromagnetic field simulation model of the motor, obtain the losses of each component of the motor, and use them as heat sources in the motor temperature field analysis.

[0007] Step 2: Establish a 2D radial temperature simulation model and design the material properties of each component;

[0008] Step 3: Set the boundary conditions for the 2D radial temperature simulation model;

[0009] Step 4: Based on the axial geometry of the motor, establish a heat transfer model in the axial direction of the motor using the thermal network method;

[0010] Step 5: Connect the 2D radial temperature field simulation model with the heat transfer model in the axial direction of the motor using nodes to establish a hybrid thermal analysis model of the electric motor and its circuit.

[0011] Step 6: Based on the hybrid thermal analysis model of the electric airport road, the nodal temperatures of the 2D radial temperature field and the nodal temperatures of the axial thermal network model are repeatedly calculated using an iterative method until the simulation results of the nodal temperatures converge.

[0012] Furthermore, in step two, the material properties include the material's thermal conductivity and heat dissipation coefficient.

[0013] Furthermore, step two also includes an equivalent simplification of heat dissipation and heat transfer in complex regions. Specifically, the derivation of the equivalent boundary heat dissipation coefficient is as follows:

[0014] First, the heat transferred via convection is calculated as follows:

[0015] q c =h c (TT f A

[0016] In the formula, q c For heat transferred by convection, h c Where A is the thermal convection coefficient, A is the cross-sectional area of ​​thermal convection, and T is the temperature. f For ambient temperature,

[0017] Secondly, the heat conducted through thermal radiation is expressed as:

[0018]

[0019] In the formula, ε em Let ε be the relative emissivity. em It is 0.9, σ SB Let be the Stefan-Boltzmann coefficient, assumed to be 5.67e. -8 W / m 2 K 4 Ambient temperature T f Set to 20℃, outer boundary temperature rise dT to 100, and relative emissivity to 9.9487.

[0020] The equivalent boundary heat dissipation coefficient is expressed as:

[0021] h = h + h

[0022] crcr

[0023] The air gap of a flat-wire wound permanent magnet synchronous motor is considered equivalent to a uniform object. Its thermal conductivity is affected by the rotor speed and the air gap structure. The heat transfer coefficient in the air gap is estimated using the Reynolds number and the Nusselt number, which can be expressed as follows:

[0024]

[0025]

[0026] In the formula, R eynold Let δ be the Reynolds number. air w is the air gap length. r r is the rotor angular velocity. o v is the inner diameter of the air gap. air N is the kinematic viscosity of air. u R is a Nusselt number. e1 R is the critical Reynolds number for laminar flow. e2 T is the critical Reynolds number for turbulence. a Let P be a Taylor number. r For Prandtl numbers,

[0027] Finally, the equivalent heat transfer coefficient in the air gap is calculated as follows:

[0028]

[0029] In the formula, λ air The heat transfer coefficient of air at 20℃ is taken as 0.023.

[0030] Using the equivalent modeling method, the thermal conductivity of the equivalent region is calculated as follows:

[0031]

[0032] In the formula, λ xye λ is the equivalent thermal conductivity in the xy direction of the groove region. z Let λ be the equivalent thermal conductivity in the z-direction of the groove region. c , λ i , λ p and a c ,a i ,a p These are the thermal conductivity and area of ​​copper, insulation, and impregnation, respectively.

[0033] Based on the axial topology and geometry of the motor, a thermal network model of the motor end is established, wherein the node temperature T of the end winding section is... e The loss P of the slot conductor flowing to the end winding e The calculation is as follows:

[0034] T e =(P eR1R2+T0R1+T a R2) / (R1+R2)

[0035] P e =(T e -T a ) / R1

[0036] In the formula, R1 is the thermal resistance between the end cap and the end winding, and R2 is the thermal resistance between the effective part of the winding and the end winding.

[0037] Furthermore, in step five, specifically, a hybrid thermal analysis model of the electric airport roadway is established by connecting the temperature node to the 2D radial temperature simulation model.

[0038] Furthermore, in step six, specifically,

[0039] After establishing the mixed thermal analysis model of the electric motor and its roadway, the temperature calculations for each node of the motor are as follows:

[0040] First, the node temperature T of the effective part of the winding is obtained by solving the 2D radial temperature simulation model in the electric arc circuit hybrid thermal analysis model. a ,

[0041] Then calculate the node temperature T of the end winding section. e The loss P of the slot conductor flowing to the end winding e ,

[0042] Finally, the loss P of the end winding e The node temperature T is recalculated by adding it to the total loss of the effective part of the winding and then using the 2D radial temperature simulation model in the electric field circuit hybrid thermal analysis model. e By iterating repeatedly, the accurate temperature of the motor can be obtained.

[0043] Furthermore, to prevent iteration from entering an infinite loop, an iteration termination condition is added during the iteration process:

[0044] To account for the effect of temperature on electromagnetic properties, an iterative coupled electromagnetic-thermal model is established to achieve multiphysics analysis. During the iteration process, the change in wire resistance with temperature rise is considered. The AC resistance calculation considering the temperature effect is as follows:

[0045]

[0046] In the formula, ρ is the conductivity of the copper wire, and l ef and l ed This refers to the effective winding length and the end winding length.

[0047] The beneficial effects of this invention are as follows: The hybrid thermal network modeling method for a flat-wire winding permanent magnet synchronous motor of this invention establishes a hybrid thermal analysis model for the electric motor and its track, which combines a two-dimensional finite element model with a lumped parameter network model, offering advantages such as high computational accuracy and efficiency. Compared with three-dimensional transient field finite element analysis, this model has a faster computation speed. Furthermore, compared with traditional lumped parameter network models, this model can display richer temperature field results for the permanent magnet motor. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the radial structure of the flat wire winding permanent magnet synchronous motor of the present invention;

[0049] Figure 2 This is a schematic diagram of the axial structure of the flat wire winding permanent magnet synchronous motor of the present invention;

[0050] Figure 3 This is a schematic diagram of the radial 2D temperature field of the flat wire winding permanent magnet synchronous motor of the present invention;

[0051] Figure 4 This is an equivalent schematic diagram of the flat wire winding permanent magnet synchronous motor winding of the present invention;

[0052] Figure 5 This is a simplified equivalent thermal network structure at the axial end of the flat wire winding permanent magnet synchronous motor of the present invention.

[0053] Figure 6 This is a schematic diagram of the hybrid thermal model of the flat wire winding permanent magnet synchronous motor on the runway of the present invention;

[0054] Figure 7 This is a schematic diagram of electromagnetic thermal coupling calculation for the flat wire winding permanent magnet synchronous motor of the present invention;

[0055] Figure 8 This is a schematic diagram showing the temperature rise calculation results of the flat wire winding permanent magnet synchronous motor of the present invention.

[0056] Among them, 1 is the housing, 2 is the stator core, 3 is the winding copper wire, 4 is the stator slot, 5 is the rotor core, 6 is the permanent magnet, 7 is the permanent magnet slot, 8 is the shaft, 9 is the winding end, 10 is the winding end cavity, 11 is the end cover, and 12 is the bearing. Detailed Implementation

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] In the accompanying drawings of specific embodiments of the present invention, in order to better and more clearly describe the working principle of each component in the system and show the connection relationship of each part in the device, only the relative positional relationship between each component is clearly distinguished. It does not constitute a limitation on the signal transmission direction, connection sequence, or size, dimension, and shape of each part within the component or structure.

[0059] like Figure 1 and Figure 2 As shown, the flat wire winding permanent magnet synchronous motor of the present invention consists of a housing 1, a stator core 2, winding copper wire 3, a stator slot 4, a rotor core 5, a permanent magnet 6, a permanent magnet slot 7, a shaft 8, winding ends 9, winding end cavities 10, end covers 11, and bearings 12.

[0060] The stator core 2 has winding slots 4 to house the stator windings 3. The rotor core 5 has permanent magnet slots 7 to house the permanent magnets 6. The permanent magnets 6 are neodymium iron boron permanent magnets and are arranged at intervals.

[0061] Based on the motor's dimensional parameters in Table 1, a finite element simulation model of the motor can be established using finite element software.

[0062]

[0063]

[0064] Table 1

[0065] Based on the electromagnetic finite element model of the motor, the motor losses under different speeds and currents can be simulated. The motor losses are input into the thermal model as a heat source. The total copper loss, stator and rotor iron loss, and permanent magnet eddy current loss in the motor can be calculated as follows:

[0066] P = 3I 2 R

[0067] Copperrmsac

[0068]

[0069]

[0070] In the formula, P copper For total copper loss, P Fe For stator and rotor iron losses, P mag For permanent magnet eddy current losses, k h k c k exe Here, f represents the coefficients for hysteresis loss, eddy current loss, and stray loss, respectively, and f is the fundamental frequency. kr B kt P represents the radial and tangential components of the magnetic flux density obtained from Fourier decomposition.h For hysteresis loss, P e For eddy current losses, P ec This represents additional losses. σ is the conductivity of the permanent magnet, J m dv is the current density, dv is the cell volume, and A is the magnetomotive force.

[0071] Based on the radial structural and dimensional parameters of the motor, a 2D radial temperature field model of the motor is established, and the material properties of each region are set, such as... Figure 3 As shown.

[0072] For 2D radial temperature field thermal analysis, the Navier-Stokes equations and the heat conduction equations can be used for solution. Based on the principle of energy conservation and the fundamental laws of heat transfer, the two-dimensional steady-state temperature field equations within the region are solved as follows:

[0073]

[0074] In the formula, λ is the thermal conductivity coefficient, T is the temperature, and q is the thermal conductivity coefficient. v For thermal density, T f Let q0 be the ambient temperature, h be the heat flux density through the boundary, and q0 be the heat flux density through the boundary. ca The heat dissipation coefficient is the boundary value.

[0075] Generally, heat transfer at the boundary occurs in two ways: convection and radiation. However, in the finite element model, the boundary can only be defined as one of these two modes. Therefore, in this invention, the radiation and convection parameters are added together and set as the heat transfer coefficient at the boundary.

[0076] The derivation of the equivalent boundary heat dissipation coefficient is as follows:

[0077] First, the heat transferred via convection can be calculated as follows:

[0078] q c =h c (TT f A

[0079] In the formula, q c For heat transferred by convection, h c Let be the thermal convection coefficient, and A be the cross-sectional area for thermal convection.

[0080] Secondly, the heat conducted through thermal radiation can be expressed as:

[0081]

[0082] In the formula, ε em For relative emissivity, ε is set in the example of this invention. em It is 0.9, σ SB The Stefan-Boltzmann coefficient has a value of 5.67e.-8 W / m 2 K 4 Ambient temperature T f Set to 20℃, outer boundary temperature rise dT is set to 100, and relative emissivity is 9.9487.

[0083] Therefore, the equivalent boundary heat dissipation coefficient can be expressed as:

[0084] h = h + h

[0085] crcr

[0086] During the operation of a flat-wire wound permanent magnet synchronous motor, the airflow in the air gap is the primary pathway for heat exchange between the stator and rotor. Generally, the airflow in the air gap rotates with the rotor, transferring heat in different ways at different speeds. At low speeds, the airflow is laminar, and heat transfer occurs through conduction. At high speeds, the airflow becomes turbulent, and the heat transfer mechanism is highly complex. To simplify analysis and modeling, the air gap of the flat-wire wound permanent magnet synchronous motor is treated as a uniform object, whose thermal conductivity is affected by the rotor speed and the air gap structure. The heat transfer coefficient in the air gap can be estimated using the Reynolds number and the Nusselt number, which can be expressed as:

[0087]

[0088]

[0089] In the formula, R eynold Let δ be the Reynolds number. air w is the air gap length. r r is the rotor angular velocity. o v is the inner diameter of the air gap. air N is the kinematic viscosity of air. u R is a Nusselt number. e1 R is the critical Reynolds number for laminar flow. e2 T is the critical Reynolds number for turbulence. a Let P be a Taylor number. r It is a Prandtl number.

[0090] Finally, the equivalent heat transfer coefficient in the air gap can be calculated as follows:

[0091]

[0092] In the formula, λ air The heat transfer coefficient of air at 20℃ is 0.023.

[0093] Although flat-wire winding permanent magnet synchronous motors employ rectangular hairpin windings, detailed modeling of the copper wires, insulation layers, and impregnation varnishes of each conductor remains highly complex and time-consuming. Therefore, this invention employs an equivalent modeling method, such as... Figure 4As shown. The thermal conductivity of the equivalent region can be calculated as:

[0094]

[0095] In the formula, λ xye λ is the equivalent thermal conductivity in the xy direction of the groove region. z Let λ be the equivalent thermal conductivity in the z-direction of the groove region. c , λ i , λ p and a c ,a i ,a p These are the thermal conductivity and area of ​​copper, insulation, and impregnation, respectively.

[0096] Based on the axial topology and geometry of the motor, a thermal network model of the motor end can be established, such as... Figure 5 As shown. The node temperature T of the end winding section... e The loss P of the slot conductor flowing to the end winding e It can be calculated as follows:

[0097] T e =(P e R1R2+T0R1+T a R2)(R1+R2)

[0098] P e =(T e -T a R1

[0099] In the formula, R1 is the thermal resistance between the end cap and the end winding, and R2 is the thermal resistance between the effective part of the winding and the end winding.

[0100] Then, by connecting the temperature nodes to the 2D radial temperature field model, a hybrid thermal model of the flat wire winding permanent magnet synchronous motor is established, as shown below. Figure 6 As shown.

[0101] After establishing the mixed thermal model of the motor, the temperature of each node of the motor can be calculated as follows:

[0102] First, the node temperature T of the effective part of the winding is obtained by solving the two-dimensional finite element model. a ,

[0103] Then calculate the node temperature T of the end winding section. e The loss P of the slot conductor flowing to the end winding e .

[0104] Finally, the loss P of the end winding e Adding this to the total loss of the effective portion of the winding, the node temperature T is recalculated again using a two-dimensional finite element model.e By iterating repeatedly, the accurate temperature of the motor can be obtained.

[0105] To prevent iteration from entering an infinite loop, an iteration termination condition can be added during the iteration process.

[0106] The heat source in the thermal model of the flat-wire winding permanent magnet synchronous motor is the loss calculated from the electromagnetic model. To account for the influence of temperature on electromagnetic characteristics, this invention also establishes an iteratively coupled electromagnetic-thermal model to achieve multi-physics analysis, such as... Figure 7 As shown. The iteration process mainly considers the change in wire resistance with temperature rise. The AC resistance calculation considering the effect of temperature is as follows:

[0107]

[0108] In the formula, ρ is the conductivity of the copper wire, and l ef and l ed This refers to the effective winding length and the end winding length.

[0109] Based on the field-circuit hybrid thermal model proposed in this invention, and the motor studied in this case, the two-dimensional finite element thermal results at a speed of 3000 rpm are as follows: Figure 8 As shown in the figure, the computation time of the hybrid model is 5 minutes, which is almost a quarter of that of the 3D finite element model with a coarse mesh. Furthermore, Table 2 summarizes the average temperature results of various components of the motor, including the permanent magnet, stator teeth, stator yoke, and housing. The results are compared with those calculated by the commercial software MotorCAD, verifying the accuracy of the hybrid thermal model. It can be seen that the hybrid thermal model and coupled electromagnetic thermal method proposed in this invention can accurately and effectively predict the thermal characteristics of a flat wire winding permanent magnet motor.

[0110]

[0111]

[0112] Table 2

[0113] The method for modeling and solving motor temperature rise proposed in this invention can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated.

[0114] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for modeling a hybrid thermal network of a flat wire winding permanent magnet synchronous motor, characterized in that, The method for modeling the hybrid thermal network of a flat wire winding permanent magnet synchronous motor includes the following steps: Step 1: Based on the structure, materials and geometric parameters of the motor, establish a radial 2D electromagnetic field simulation model of the motor, obtain the losses of each component of the motor, and use them as heat sources in the motor temperature field analysis. Step 2: Establish a 2D radial temperature field simulation model and design the material properties of each component; Step 3: Set the boundary conditions for the 2D radial temperature field simulation model; Step 4: Based on the axial geometry of the motor, establish a heat transfer model in the axial direction of the motor using the thermal network method; Step 5: Connect the 2D radial temperature field simulation model with the heat transfer model in the axial direction of the motor in a node manner to establish a hybrid thermal analysis model of the electric motor and its circuit. Step Six: Based on the hybrid thermal analysis model of the electric motor and its running track, the nodal temperatures of the 2D radial temperature field and the nodal temperatures of the axial thermal network model are repeatedly calculated using an iterative method until the simulation results of the nodal temperatures converge. In Step Six, after establishing the hybrid thermal analysis model of the electric motor and its running track, the temperatures of each node of the motor are calculated as follows: First, the node temperature of the effective part of the winding is obtained by solving the 2D radial temperature field simulation model in the hybrid thermal analysis model of the electric arc circuit. T a , Then calculate the node temperature of the end winding section. T e And the loss of the slot conductor flowing to the end winding P e , Finally, the losses of the end windings P e The node temperature is then recalculated using the 2D radial temperature field simulation model in the electric arc circuit hybrid thermal analysis model, after being added to the total loss of the effective portion of the winding. T e By iterating repeatedly, the accurate temperature of the motor can be obtained. To prevent iteration from entering an infinite loop, an iteration termination condition is added during the iteration process: To account for the effect of temperature on electromagnetic properties, an iterative coupled electromagnetic-thermal model is established to achieve multiphysics analysis. During the iteration process, the change in wire resistance with temperature rise is considered. The AC resistance calculation considering the temperature effect is as follows: In the formula, ρ The conductivity of copper wire, l ef and l ed This refers to the effective winding length and the end winding length.

2. The method for modeling a hybrid thermal network of a flat wire winding permanent magnet synchronous motor according to claim 1, characterized in that, In step two, the material properties include the material's thermal conductivity and heat dissipation coefficient.

3. The method for modeling a hybrid thermal network of a flat wire winding permanent magnet synchronous motor according to claim 2, characterized in that, Step two also includes an equivalent simplification of heat dissipation and heat transfer in complex areas. Specifically, the derivation of the equivalent boundary heat dissipation coefficient is as follows: First, the heat transferred via convection is calculated as follows: In the formula, q c Heat transferred by convection h c The thermal convection coefficient, A For the cross-sectional area of ​​heat convection, T For temperature, T f For ambient temperature, Secondly, the heat conducted through thermal radiation is expressed as: In the formula, ε em For relative emissivity, set ε em It is 0.

9. σ SB The Stefan-Boltzmann coefficient is set to a value of 5.67e. -8 W / m 2 K 4 Ambient temperature T f Set at 20℃, outer boundary temperature rise dT Set to 100, the relative emissivity is 9.9487. The equivalent boundary heat dissipation coefficient is expressed as: The air gap of a flat-wire wound permanent magnet synchronous motor is considered equivalent to a uniform object. Its thermal conductivity is affected by the rotor speed and the air gap structure. The heat transfer coefficient in the air gap is estimated using the Reynolds number and the Nusselt number, which can be expressed as follows: In the formula, R eynold The Reynolds number is... δ air The length of the air gap. w r The rotor angular velocity, r o The inner diameter of the air gap. v air The viscosity of air motion. N u For Nusselt numbers, R e1 For laminar critical Reynolds number, R e2 For turbulent critical Reynolds number, T a It is a Taylor number. P r For Prandtl numbers, Finally, the equivalent heat transfer coefficient in the air gap is calculated as follows: In the formula, λ air The heat transfer coefficient of air at 20℃ is taken as 0.

023. Using the equivalent modeling method, the thermal conductivity of the equivalent region is calculated as follows: In the formula, λ xye Let be the equivalent thermal conductivity in the xy direction of the groove region. λ z For the groove area z Equivalent thermal conductivity in the direction, λ c , λ i , λ p and a c , a i , a p These are the thermal conductivity and area of ​​copper, insulation, and impregnation, respectively. Based on the axial topology and geometry of the motor, a thermal network model of the motor end is established, wherein the node temperature of the end winding section is... T e And the loss of the slot conductor flowing to the end winding P e The calculation is as follows: In the formula, R 1 represents the thermal resistance between the end cap and the end winding. R 2 represents the thermal resistance between the effective portion of the winding and the end winding.

4. The method for modeling a hybrid thermal network of a flat wire winding permanent magnet synchronous motor according to claim 3, characterized in that, In step five, specifically, a hybrid thermal analysis model of the electric airport roadway is established by connecting the temperature node with the 2D radial temperature field simulation model.

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