A thermal network modeling method for permanent magnet synchronous linear motor rotor

Abstract

The present invention is applicable to the field of electrical inductance technology and provides a permanent magnet synchronous linear motor rotor thermal network modeling method, the method comprising the following steps: calibrating the size and material of each component of the motor rotor, as well as the natural convection coefficient and the thermal conductivity of each component; establishing two different equivalent thermal network models according to the different boundary conditions of the coils in the motor rotor; calculating the total calorific value of the heat source in one of the equivalent thermal network models; calculating the equivalent thermal resistance value of each node in one of the equivalent thermal network models according to the equivalent thermal resistance calculation formula under different heat transfer modes; outputting the final average temperature of the medium in the cooling structure according to the characteristics of the cooling structure in the motor rotor; and then determining the temperature rise of each node; the present invention establishes two equivalent thermal network models according to the different boundary conditions of different coils in the motor rotor to calculate the temperature of each coil and the temperature rise of each node, which can truly reflect the temperature of the motor operation.

Description

Technical Field

[0001] The invention belongs to the technical field of electrical inductance and provides a method for modeling a thermal network of a permanent magnet synchronous linear motor rotor. Background Art

[0002] Coreless permanent magnet synchronous linear motors are widely used in laser cutting machines and 3D printers due to their simple structure, fast dynamic response, and lack of cogging. To increase thrust, the coreless double-layer coil structure has a smaller air gap than a single-layer coil, making convection heat transfer with the air more difficult. This also causes the winding temperature to rise rapidly during continuous operation with high thrust and long stroke, as well as during high-load positioning, due to the high electrical load, which can easily cause the winding insulation layer to burn out. To increase the heat transfer efficiency of the motor, a cooling solution with a double-layer winding embedded water-cooling structure was designed. This water-cooling structure consists of a double-channel water-cooling plate. As water flows through the cooling structure, heat is transferred through the temperature difference between the inlet and outlet. This improves heat transfer efficiency but sacrifices heat transfer uniformity, which can easily lead to local overheating of the motor, structural deformation, and control parameter mismatch.

[0003] In order to accurately evaluate the heat transfer effect of the water-cooling structure, it is necessary to comprehensively evaluate its heat transfer efficiency and heat transfer uniformity through the motor thermal network modeling method.

[0004] Traditional motor thermal network modeling methods model the coils, which serve as heat sources, as a whole without considering the different boundary conditions of the coils. As a result, the calculated temperatures of each coil are the same, which differs significantly from the actual temperatures of each coil. In addition, there is a lack of existing technology for thermal network modeling of water-cooled linear motors on the market. Therefore, there is an urgent need to design a new motor thermal network modeling method. Summary of the Invention

[0005] The purpose of an embodiment of the present invention is to provide a method for modeling the thermal network of a permanent magnet synchronous linear motor rotor, aiming to solve the problem in the prior art that the coil serving as a heat source is modeled as a whole without considering the different boundary conditions of the coils, so that the calculated temperatures of the coils are the same, which is greatly different from the actual temperatures of the coils.

[0006] The embodiment of the present invention is implemented as follows: a method for modeling a thermal network of a permanent magnet synchronous linear motor rotor, the method comprising the following steps:

[0007] Calibrate the size and material of each component of the motor rotor, as well as the natural convection coefficient and thermal conductivity of each component;

[0008] The structure of the motor rotor is simplified based on the principle of symmetry, and two different equivalent thermal network models are established according to different boundary conditions of the coils in the motor rotor;

[0009] Calculate the total heat output of the heat source in one of the equivalent thermal network models;

[0010] Calculate the equivalent thermal resistance value of each node in one of the above equivalent thermal network models according to the equivalent thermal resistance calculation formula under different heat transfer modes;

[0011] An iterative model is constructed based on the characteristics of the cooling structure in the motor rotor. The total heat output of the heat source is used as a constraint for energy conservation. The temperature of the medium before and after refrigeration of the cooling structure is input into the iterative model. The final average temperature of the medium in the cooling structure is output using an iterative method based on energy conservation.

[0012] Determining the temperature rise of each node according to the final average temperature of the medium, the equivalent thermal resistance value of each node, and the ambient temperature;

[0013] Follow the above steps to calculate the temperature rise of the heat sources in the remaining equivalent thermal network models.

[0014] An embodiment of the present invention provides a method for modeling a thermal network of a permanent magnet synchronous linear motor rotor. Two different equivalent thermal network models are established according to the different boundary conditions of the coils in the motor rotor, which solves the problem in the prior art that the coils serving as the heat source are modeled as a whole without considering the different boundary conditions of the coils. As a result, the calculated temperatures of the coils are the same, which differ greatly from the actual temperatures of the coils. At the same time, when calculating the average fluid temperature of the cooling mechanism in the equivalent thermal network model, the final average fluid (water) temperature is determined by an iterative method to adapt to different equivalent thermal network models, so that the obtained temperatures of the coils at each position are more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A flow chart of a method for modeling a thermal network of a permanent magnet synchronous linear motor rotor provided in an embodiment of the present invention;

[0016] Figure 2 A block diagram of the arrangement of the mover and permanent magnets in the permanent magnet synchronous linear motor provided in an embodiment of the present invention;

[0017] Figure 3 This is the thermal network model of the edge coil in the embodiment of the present invention;

[0018] Figure 4 1 is a flow chart of the principle of the iterative model in an embodiment of the present invention;

[0019] Figure 5 This is the thermal network model of the middle coil in the embodiment of the present invention;

[0020] Figure 6 A schematic diagram of the structure of a permanent magnet synchronous linear motor provided in an embodiment of the present invention;

[0021] Figure 7A diagram of a dual-waterway topology provided in an embodiment of the present invention;

[0022] Figure 8 A schematic diagram of the division of coils and water-cooling plates provided in an embodiment of the present invention;

[0023] Figure 9 This is a primary temperature rise diagram under the condition of current I of 4.5A and water flow velocity of 0.1m / s in the embodiment of the present invention;

[0024] Figure 10 Graph showing the change of coil temperature rise over time in an embodiment of the present invention;

[0025] Figure 11 This is a diagram of the primary instantaneous temperature rise under different currents without a water cooling structure in an embodiment of the present invention;

[0026] Figure 12 1 is a temperature rise diagram of the coil without a water cooling structure when the current I is 4.5A in an embodiment of the present invention.

[0027] In the figure: 1- back iron; 2- permanent magnet; 3- coil; 4- water cooling plate; 401- first water channel; 402- second water channel; 5- guide rail; 6- mover. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] It should be understood that the terms "first," "second," and so forth, as used herein, may be used to describe various elements herein, but unless otherwise specified, these elements are not limited by these terms. These terms are used solely to distinguish a first element from another element. For example, a first xx water channel could be referred to as a second xx water channel, and similarly, a second xx water channel could be referred to as a first xx water channel without departing from the scope of this application.

[0030] like Figure 1 As shown, in one embodiment, a method for modeling a thermal network of a permanent magnet synchronous linear motor rotor is proposed, which may specifically include the following steps S101 to S111;

[0031] SI01: Calibrate the dimensions and materials of each component of the motor rotor, as well as the natural convection coefficient and thermal conductivity of each component;

[0032] In this step, the number of coils in the motor rotor, the volume occupied by a single coil, the coil resistance, and the effective phase current through the coil for stable motor operation can be determined. In addition, the thermal conductivity corresponding to each material can be queried from the determined material, as well as some other common parameters or coefficients, such as: T is the solid temperature, α is the convective heat transfer coefficient, T f is the fluid temperature, etc.

[0033] S103: simplifying the structure of the motor mover based on the principle of symmetry, and establishing two different equivalent thermal network models according to different boundary conditions of the coils in the motor mover;

[0034] S105: Calculate the total heat generation of the heat source in one of the equivalent thermal network models;

[0035] In this step, the heat source is the coil or winding in the equivalent thermal network model.

[0036] The copper loss and heat source density of the winding can be calculated using the following formula:

[0037] p cu =∑I 2 R (1)

[0038]

[0039] The copper loss of the winding is P cu It represents the total calorific value of the heat source; I is the effective phase current, R is the coil resistance, k is the number of coils, and V is the volume occupied by a single coil.

[0040] Under natural convection conditions, the convective heat transfer between the edge coil and the air satisfies the following formula:

[0041]

[0042] where λ is the thermal conductivity, T is the solid temperature, α is the convective heat transfer coefficient, and T f is the fluid temperature.

[0043] S107: Calculating the equivalent thermal resistance value of each node in one of the equivalent thermal network models according to the equivalent thermal resistance calculation formula under different heat transfer modes;

[0044] S109: constructing an iterative model based on the characteristics of the cooling structure in the motor rotor, using the total heat output of the heat source as a constraint for energy conservation, inputting the medium temperature before and after refrigeration of the cooling structure into the iterative model, and outputting the final average temperature of the medium in the cooling structure using an iterative method based on energy conservation;

[0045] S111: determining the temperature rise of each node according to the final average temperature of the medium, the equivalent thermal resistance value of each node, and the ambient temperature;

[0046] Follow the above steps to calculate the temperature rise of the heat sources in the remaining equivalent thermal network models.

[0047] In this embodiment, different equivalent thermal network models are established according to different boundary conditions of the motor rotor, replacing the existing modeling of the coil as a heat source as a whole without considering the different boundary conditions of the coil. As a result, the calculated temperatures of each coil are the same, which is greatly different from the actual temperature of each coil. At the same time, when calculating the average fluid temperature of the cooling mechanism in the equivalent thermal network model, the final average fluid (water) temperature is determined by an iterative method to adapt to different equivalent thermal network models, so that the obtained temperature of the coil at each position is more accurate.

[0048] In an application scenario of this embodiment, Figures 6 to 8 As shown, the permanent magnet synchronous linear motor can be a water-cooled ironless double-layer winding permanent magnet synchronous linear motor, or other linear motors; take the water-cooled ironless double-layer winding permanent magnet synchronous linear motor as an example; the secondary of the motor is a double-secondary structure with upper and lower permanent magnets (i.e., the permanent magnet 2 shown in the figure) arranged in the same manner, and the mover 6 is mainly composed of a winding (i.e., a coil 3), a winding support structure, and a water-cooled plate 4; the mover 6 is slidingly set on the guide rail 5, and the guide rail 5 and the stator are arranged on the back iron 1; the cooling structure of the motor adopts a water-cooling structure, and the water-cooling structure is embedded in the middle of the double-layer winding. The use of an embedded heat exchange method can make the heat dissipation of each coil more uniform; the topological structure of the double water channel in the water-cooling structure, such as Figure 2 shown.

[0049] In an application scenario of this embodiment, the different boundary conditions specifically include:

[0050] First boundary condition: the side of the motor rotor is in contact with the air;

[0051] The second boundary condition: the side of the motor rotor does not come into contact with the air.

[0052] Therefore, in step S103, when simplifying the structure of the motor rotor, the motor rotor and the stator are arranged in a regular pattern, which not only simplifies the motor structure but also simplifies the double water channel. Specifically, when establishing the equivalent thermal network model, the coil and the water-cooling plate are divided into six parts from the center line of the adjacent coils. The coils of each part are named from the inlet of the water channel to coil C1 to coil C6, as shown in FIG. Figure 8As shown; according to the boundary condition definition, coil C1 and coil C6 meet the first boundary condition, and the equivalent thermal network models of coil C1 and coil C6 are the same; coils C2 to coil C5 meet the second boundary condition, and the equivalent thermal network models of coils C2 to coil C5 are the same; and since the upper and lower permanent magnets of the secondary are arranged in the same manner, it can be seen that when establishing the equivalent thermal network model, further simplification can be performed based on the principle of symmetry.

[0053] The equivalent thermal network models of the coils C1, C6, C2 to C5 are different. The specific difference is caused by the different contact conditions between the edge of the mover and the air. The equivalent thermal network model of the coil C1 is as follows: Figure 3 As shown, the equivalent thermal network model of coil C2 is as follows Figure 5 As shown;

[0054] Figure 3 In this thermal network model, the heat source is the winding (also called coil) and is represented by P cu It indicates that there are four paths for heat transfer; Figure 5 In this thermal network model, the heat source is the winding with P cu It indicates that there are also four paths for heat transfer; however, the equivalent thermal resistance corresponding to the outer edge of the mover is different, and it can be flexibly modified and adjusted according to actual conditions during calculation.

[0055] The motor's coreless double-layer coil structure has a smaller air gap than a single-layer coil, making convection heat transfer with the air more difficult. This also leads to a rapid rise in winding temperature during continuous operation with high thrust and long stroke, as well as high-load positioning, due to the high electrical load, which can easily cause the winding insulation layer to burn out. To improve the motor's heat transfer efficiency, a cooling solution with a double-layer winding embedded water-cooling structure was designed. This water-cooling structure uses a dual-channel water-cooling plate. Because water transfers heat through the water-cooling structure through the temperature difference between the inlet and outlet, the water-cooling structure improves heat transfer efficiency but sacrifices heat transfer uniformity. This can easily lead to local overheating, structural deformation, and control parameter mismatch. To accurately evaluate the heat transfer effect of the water-cooling structure, a comprehensive evaluation of its heat transfer efficiency and heat transfer uniformity is required. The heat transfer uniformity of the water-cooling structure can be reflected by the temperature of each coil in the rotor. Therefore, this embodiment establishes two equivalent thermal network models based on the characteristics of the cooling structure and the different boundary conditions of different coils. This can accurately calculate the temperature of each coil, providing a more accurate theoretical basis for the design and use of the above-mentioned motor.

[0056] In another implementation scenario of this embodiment, step S107: the equivalent thermal resistance value of each node in one of the above equivalent thermal network models is calculated according to the equivalent thermal resistance calculation formula under different heat transfer modes, taking coil C6 as an example:

[0057] The solid thermal conduction path is calculated according to the solid thermal resistance calculation formula; the solid thermal resistance calculation formula is as follows:

[0058] R s =m / λA (4)

[0059] where R s is the solid thermal resistance, λ is the thermal conductivity, m is the heat transfer length, and A is the heat transfer area.

[0060] The fluid thermal conduction path is calculated according to the fluid thermal resistance calculation formula; the fluid thermal conduction resistance can be expressed as:

[0061] R f =1 / hA (5)

[0062] where R f is the convective heat transfer thermal resistance, h is the convective heat transfer coefficient, and A is the heat transfer area.

[0063] For a cooling mechanism with a double-channel structure, the average temperature of the water channel is calculated as follows:

[0064]

[0065] where t a is the average water temperature of the two water channels, l1 and l2 are the lengths of the first water channel 401 and the second water channel 402, t a1 With t a2 are the average temperatures at the inlet and outlet of the first water channel 401 and the second water channel 402, respectively;

[0066] In heat transfer, the flow of incompressible viscous fluids can be described using governing equations, which include the mass conservation equation, the momentum conservation equation, and the energy conservation equation. These equations are applicable to both laminar and turbulent flows. The Nusselt number for laminar or turbulent flows is as follows:

[0067]

[0068] where N u is the Nusselt number, R e is the Reynolds number, P r is the Prandtl number, l is the channel length, d is the channel diameter, η f is the dynamic viscosity of the fluid at the average temperature, η w is the dynamic viscosity of the fluid at the wall temperature.

[0069] Reynolds number R e The calculation formula of the flow heat transfer coefficient h is as follows:

[0070]

[0071]

[0072] where v f is the fluid viscosity coefficient, and λ is the fluid thermal conductivity.

[0073] In another embodiment, the water channel inlet is applied at a temperature of T in The cooling water, after knowing the effective value of the current I, can calculate the heat loss of the coil to be approximately p cu .

[0074] When the flow rate at the water channel inlet is u, the outlet temperature of the double water channel can be assumed first, and then the coil temperature rise T can be calculated. c , and the temperature T of PLA (insulation layer) P ; Figure 4 Medium P a The calculation is shown in formula (10), where T w Refers to the wall temperature in contact with the fluid, T f Refers to the temperature of the air, ρ, c, u, d are the density, specific heat capacity, flow rate and diameter of the water channel respectively, T out With T in Refers to the outlet and inlet temperatures of the water channel. The average temperature of the two water channels is finally calculated.

[0075]

[0076] for Figure 3 The calculation formula of the thermal resistance of each node is as follows:

[0077]

[0078] The heat source and heat network distribution are obtained, and the heat loop Q1 can be expressed as:

[0079]

[0080] where p cu is the copper loss in the calculation area.

[0081] Coil temperature rise T c The calculation formula is as follows:

[0082] T c =T e +Q1R1 (13-1)

[0083] T p =T c -Q1(R c1 -R re1 ) (13-2)

[0084] Where T e is the ambient temperature, T Pis the insulation layer temperature, and finally the coil temperature T of coil C6 can be calculated c6 .

[0085] Similarly, when calculating coil C2, coil C3, coil C4 or coil C5, the above steps can also be used, such as Figure 5 As shown, due to different boundary conditions, only the formula of R1 needs to be modified, and the parameters of R2, R3, and R4 need to be modified;

[0086]

[0087] Substituting the modified parameters into the above formula (11), the thermal resistance of each node of coil C5 can be calculated, and then the coil temperature T of coil C5 can be calculated. C5 .

[0088] In the above embodiment, the coil temperature T of coil C6 is obtained. c6 , coil temperature T of coil C5 C5 , the coil temperature of each coil of the entire motor rotor can be obtained. Since two equivalent thermal network models are established based on the different boundary conditions of different coils in the rotor to calculate the temperature of each coil, the result is closer to the actual situation when the motor is running.

[0089] In one embodiment, when calculating the coil temperature of each coil, heat transfer between windings (coils) is ignored, and the average temperature of the coil is represented by the temperature at the equivalent thermal resistance.

[0090] Specifically, taking coil C6 as an example, T c6 The temperature at represents the average temperature of coil C6. Similarly, when calculating the temperature of the remaining coils, the heat transfer between the windings can also be ignored.

[0091] In one embodiment, the method further includes: ignoring heat conduction in the longitudinal direction of the motor rotor and between coils when establishing the equivalent thermal network model.

[0092] In one embodiment, in step S111, a mathematical model of the equivalent thermal network can be established based on the established equivalent thermal network model, Kirchhoff's heat flow law can be derived based on Kirchhoff's law in the circuit, the average temperature of the heat source can be calculated based on the thermal loop, and the temperature of each node can be calculated.

[0093] In one embodiment, when the cooling structure is configured as a dual-water channel structure, the coils of the motor rotor and the water cooling plate of the dual-water channel structure are divided in the same manner.

[0094] Specifically, if Figure 8As shown, the number of coils set in the electric mover is 6, and the coils and the water-cooling plate with a double-water channel structure can be divided into 6 groups, respectively named coil C1 (Coil1), coil C2 (Coil2) to coil C6 (Coil6);

[0095] In one embodiment, when the cooling structure is configured as a single-channel structure, the coils of the motor rotor and the water-cooling plate of the single-channel structure are divided in the same manner.

[0096] In this embodiment, a single-channel cooling mechanism is used. When cooling the motor, the temperature difference range at the inlet and outlet of the channel is greater than that of a dual-channel structure. This single channel can be divided into multiple sections equal to the number of coils. The temperature difference at the inlet and outlet of each section of the single channel is then calculated, and the average temperature of each section is then calculated. This reduces the impact of temperature differences between the motor's rotor coils on the single channel temperature, which can lead to failure or inaccuracy of the equivalent thermal network model.

[0097] In one embodiment, when the cooling structure is configured as a non-water-cooling structure, the coils of the motor rotor and the heat exchange surface of the non-water-cooling structure are divided in the same manner.

[0098] In this embodiment, the non-water-cooling structure can be an air-cooling mechanism, a nitrogen cooler or a semiconductor cooler, etc. The length of the position where the non-water-cooling structure contacts the edge coil and the position where it contacts the middle coil are quite different. In order to accurately calculate the temperature rise of each coil, the non-water-cooling structure is also divided into equal parts to achieve accurate calculation of the temperature rise of each coil.

[0099] In one embodiment, Figure 4 As shown, the final average temperature is calculated by the iterative model, specifically including:

[0100] Set the inlet and outlet temperatures of the double-channel structure, as well as the wall temperature where the channel contacts the water flow, and substitute them into the following formula:

[0101]

[0102] Calculate the average temperature P of the two water channels a ; Among them, T w Refers to the wall temperature where the water channel contacts the fluid, T f Refers to the temperature of the air, ρ, c, u, d are the density, specific heat capacity, water flow rate and diameter of the water channel respectively, T out With T in Refers to the outlet and inlet temperatures of the water channel, h is the convective heat transfer coefficient, and A is the heat transfer area;

[0103] If P a ≈p cu Established, p cuRepresents the total calorific value of the heat source, which determines the final water channel inlet and outlet temperatures of the double-water channel structure;

[0104] If P a ≈p cu If it is not established, then modify the water channel inlet and outlet temperatures and water channel wall temperature of the set double water channel structure, and recalculate the double water channel average temperature P a , until P a ≈p cu Established.

[0105] In this embodiment, when the water channel inlet and outlet temperatures of the dual-water channel structure are calculated by the iterative method, since the Prandtl number Pr, fluid kinematic viscosity d and fluid thermal conductivity h in the above formulas change with the fluid temperature, when calculating the temperature of each node in different equivalent thermal network models, it corresponds to the fluid temperature corresponding to each node, which can better represent the temperature rise of each node.

[0106] In order to better implement the above-mentioned method for modeling a thermal network of a permanent magnet synchronous linear motor rotor, in one embodiment, the method includes the following steps:

[0107] Based on the assumed outlet temperature and water cooling plate temperature, the Nusselt number is calculated using formula (7) and the convective heat transfer coefficient, T c With T P The calculation is obtained according to formulas (13-1) and (13-2) after calculating the thermal resistance and thermal circuit. P In formula (10), the temperature of the PLA (insulation layer) is the wall temperature, so T P The value of is T in formula (10) w The heat of the coil in steady state is only transferred by the heat transfer of water flow and the convection of air. The two parts in formula (10) refer to these two types of heat transfer respectively. Therefore, the heat conducted by the coil in steady state is obtained according to formula (10). It is compared with the heat generated by the coil P cu After comparison, determine whether the assumed value is accurate. If the error meets the requirements, it is determined that the assumed value is accurate.

[0108] In one embodiment, a multi-turn winding is equivalent to a heat conductor with uniformly distributed material properties using an equivalent method. The parameters of the winding and other parts after the equivalent method are shown in Table 1.

[0109] Table 1 is the primary material properties table

[0110]

[0111] The above heat conductor is tested experimentally. Taking the double-channel water cooling structure as an example, cooling water with a temperature of 24°C is applied to the water channel inlet of the water cooling structure. The effective value of the current is 4.5A and the water channel flow rate is 0.1m / s. According to the following Figure 4 For the process shown, the calculated waterway outlet temperature is 27°C.

[0112] At the same time, the calculation results of thermal network model 1 (equivalent thermal network model corresponding to coil C1 or C6) are shown in Table 2 below:

[0113] Table 2 shows the structural dimensions and thermal conductivity parameters of thermal network model 1

[0114]

[0115]

[0116] Where T e is the ambient temperature, which is 27°C, and the coil temperature T of C6 is finally calculated. c6 It is 56.3℃.

[0117] As mentioned above, some parameters of thermal network model 1 are modified. According to formula (14), thermal network model 2 (equivalent thermal network model corresponding to coil C2) is obtained. The heat conduction parameters of thermal network model 2 are shown in Table 3:

[0118] Table 3 shows the structural dimensions and thermal conductivity parameters of thermal network model 2

[0119]

[0120] According to the coil temperature rise calculation formula, T c5 The temperature is 57.5℃, and the temperatures of coils C1 to C4 are calculated based on the two thermal network models. The comparison between the calculated results and the simulation results is shown in Table 4.

[0121] Table 4 shows the calculation and simulation results of coil temperature rise

[0122]

[0123] Therefore, the coil temperature calculated by the existing single thermal network model is the average temperature of each coil, and it is impossible to distinguish the difference in the temperature of each coil, and it is impossible to reflect the difference in coil temperature rise under different boundary conditions and different water channel structures through this temperature; in this embodiment, two different equivalent thermal network models can be established according to the different boundary conditions of the coils in the motor rotor, reflecting the coil temperature rise under different boundary conditions and different water cooling structures, providing technical support for the design and improvement of the motor.

[0124] In one embodiment, Figures 9 to 12As shown in the figure, the temperature rise of the motor rotor with a double-water-channel water-cooling structure is simulated and compared with that of the motor rotor without a water-cooling structure. Figure 9 This is a primary temperature rise diagram under the conditions of a current I of 4.5A and a waterway flow rate of 0.1m / s in an embodiment of the present invention; Figure 10 Graph showing the change of coil temperature rise over time in an embodiment of the present invention; Figure 11 This is a diagram of the primary instantaneous temperature rise under different currents without a water cooling structure in an embodiment of the present invention; Figure 12 This is the temperature rise diagram of the coil without water cooling structure under the current I of 4.5A in the embodiment of the present invention. Figure 9 and Figure 12 It is easy to see that compared with the water-cooling structure with dual water channels in this embodiment, the motor rotor without water-cooling structure only takes 29 seconds to reach the limited temperature rise of 120°C of the coil under a large current of 4.5A; Figure 10 and Figure 11 For the motor rotor without water cooling structure, after 75 seconds of power-on, the corresponding temperature rises when the currents are 3A, 3.5A, 4A and 4.5A are: 115℃, 150℃, 185℃ and 220℃. It can be seen that the primary instantaneous temperature rise of the motor without water cooling structure changes greatly under different currents; while the motor with water cooling structure has a small difference in the change of coil temperature rise over time under different currents.

[0125] An embodiment of the present invention provides a method for modeling the thermal network of a permanent magnet synchronous linear motor rotor. Two different equivalent thermal network models are established according to the different boundary conditions of the coils in the motor rotor, which solves the problem in the prior art that the coils serving as the heat source are modeled as a whole without considering the different boundary conditions of the coils. As a result, the calculated temperatures of the coils are the same, which differ greatly from the actual temperatures of the coils. At the same time, when calculating the average fluid temperature of the cooling mechanism in the equivalent thermal network model, the final average fluid temperature is determined by an iterative method, which is adapted to different equivalent thermal network models, so that the obtained temperatures of the coils at each position are more accurate.

[0126] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0127] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0128] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for modeling a thermal network of a permanent magnet synchronous linear motor rotor, characterized in that: The method comprises the following steps: Calibrate the size and material of each component of the motor rotor, as well as the natural convection coefficient and thermal conductivity of each component; The structure of the motor rotor is simplified based on the principle of symmetry, and two different equivalent thermal network models are established according to different boundary conditions of the coils in the motor rotor; Calculate the total heat output of the heat source in one of the equivalent thermal network models; Calculate the equivalent thermal resistance value of each node in one of the above equivalent thermal network models according to the equivalent thermal resistance calculation formula under different heat transfer modes; An iterative model is constructed based on the characteristics of the cooling structure in the motor rotor. The total heat output of the heat source is used as a constraint for energy conservation. The temperature of the medium before and after refrigeration of the cooling structure is input into the iterative model. The final average temperature of the medium in the cooling structure is output using an iterative method based on energy conservation. The final average temperature is calculated using the iterative model, specifically including: Set the inlet and outlet temperatures of the double-channel structure, as well as the wall temperature where the channel contacts the water flow, and substitute them into the following formula: ， Calculate the average temperature of the two waterways ;in, Refers to the wall temperature where the water channel contacts the fluid. The temperature of the air, 、 、 、 They are the density of water, specific heat capacity, water flow rate and the diameter of the water channel, and refers to the outlet and inlet temperatures of the waterway, is the convective heat transfer coefficient, is the heat exchange area; like ≈ Established, Represents the total calorific value of the heat source, which determines the final water channel inlet and outlet temperatures of the double-water channel structure; like ≈ If it is not true, then modify the water channel inlet and outlet temperatures and water channel wall temperature of the set double water channel structure and recalculate the average temperature of the double water channel. , until ≈ Established; Determining the temperature rise of each node according to the final average temperature of the medium, the equivalent thermal resistance value of each node, and the ambient temperature; Follow the above steps to calculate the temperature rise of the heat sources in the remaining equivalent thermal network models.

2. The method for modeling a thermal network of a permanent magnet synchronous linear motor rotor according to claim 1, characterized in that: The method further includes: when establishing the equivalent thermal network model, ignoring the heat conduction in the longitudinal direction of the motor rotor and between the coils.

3. The method for modeling a thermal network of a permanent magnet synchronous linear motor rotor according to claim 1, characterized in that: When the cooling structure is set as a double-water-channel structure, the coil of the motor rotor and the water-cooling plate of the double-water-channel structure are divided in the same manner.

4. The method for modeling a thermal network of a permanent magnet synchronous linear motor rotor according to claim 1, characterized in that: When the cooling structure is set as a single-channel structure, the coil of the motor rotor and the water-cooling plate of the single-channel structure are divided in the same way.

5. The method for modeling a thermal network of a permanent magnet synchronous linear motor rotor according to claim 1, characterized in that: When the cooling structure is set to a non-water-cooling structure, the coil of the motor rotor and the heat exchange surface of the non-water-cooling structure are divided in the same way.

6. The method for modeling a thermal network of a permanent magnet synchronous linear motor rotor according to claim 1, characterized in that: The different boundary conditions specifically include: First boundary condition: the side of the motor rotor is in contact with the air; The second boundary condition: the side of the motor rotor does not come into contact with the air.

7. The method for modeling a thermal network of a permanent magnet synchronous linear motor rotor according to claim 1, characterized in that: The convective heat transfer coefficient ,satisfy: ， ； ， in is the Nusselt number, is the Reynolds number, is the Prandtl number, is the length of the waterway, is the waterway diameter, is the dynamic viscosity of the fluid in the water channel at the average temperature, is the dynamic viscosity of the fluid at the channel wall temperature; is the fluid viscosity coefficient, is the thermal conductivity of the fluid.

8. The method for modeling a thermal network of a permanent magnet synchronous linear motor rotor according to claim 1 or 7, characterized in that: The total calorific value of the heat source in the equivalent thermal network model satisfies: ， in, is the effective phase current, is the coil resistance of the motor rotor.

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