A compensation thermal resistance regulation method applied to relay thermal network modeling

Abstract

The application relates to a compensation thermal resistance regulation method applied to relay thermal network modeling, and belongs to the technical field of thermal modeling in an electromagnetic and thermal coupling system. The method is used for solving the problems that a traditional thermal network model is inaccurate in predicting a local temperature field and is difficult to identify a hot spot in relay thermal analysis. The method comprises the following steps: S1, establishing a thermal network model of a relay structure; S2, inserting a compensation thermal resistance unit to establish a T-shaped network; S3, solving a two-dimensional Poisson equation to obtain an average temperature; S4, comparing the average temperature with a node temperature in the thermal resistance network; and S5, iteratively adjusting the compensation thermal resistance unit until the temperature error of the two is within an acceptable range; and S6, running the calibrated model to output a steady-state temperature. The introduction of the compensation thermal resistance is equivalent to adding a “reverse heat flux regulator” in mathematics, so that the node temperature can be approximately equal to the two-dimensional integral average temperature, thereby effectively correcting the distortion of the thermal network in a local two-dimensional area and significantly improving the reflection ability of the model to a local hot spot and a temperature gradient.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of thermal modeling in electromagnetic and thermal coupling systems, and particularly relates to a compensation thermal resistance regulation method applied to relay thermal network modeling. BACKGROUND

[0002] As a key actuator in electromagnetic control systems, the working process of a relay is often accompanied by significant current on-off behavior, which causes complex heat distribution in its coil, core, contact and other parts. Especially under high-frequency high-load or continuous energization state, the internal heat accumulation effect of the relay is significant, which not only causes aging of the coil insulation material and degradation of the magnetic performance, but also accelerates the ablation and welding of the contact, thereby causing serious consequences of reliability decline and even failure. Therefore, accurately grasping the temperature rise distribution and hot spot position inside the relay is of great significance for optimizing the structural design and service life prediction of the relay.

[0003] At present, in the thermal analysis of a relay, although finite element thermal simulation can provide high-precision temperature field distribution results, its high calculation cost and complex modeling limit its popularization and application in the early design stage of products. Compared with the above, the thermal network model based on one-dimensional heat transfer theory is widely used in the modeling of internal thermal paths of relays due to its simplicity and efficiency. However, the core assumption of the thermal network model is that the heat flow is transmitted in a single direction, ignoring the multidimensional temperature gradient caused by heat conduction, convection and local heat sources in the actual structure, which leads to large deviation in the estimation of local hot spots and average temperature, especially in the coil winding. SUMMARY

[0004] In order to solve the problem that the traditional thermal network model is inaccurate in predicting the local temperature field and difficult to identify the hot spot in the thermal analysis of a relay, the application provides a compensation thermal resistance regulation method applied to relay thermal network modeling.

[0005] The technical scheme adopted by the application is as follows:

[0006] A compensation thermal resistance regulation method applied to relay thermal network modeling, comprising the following steps:

[0007] S1. establishing a thermal network model of the structure of the relay;

[0008] S2. inserting a compensation thermal resistance unit to establish a T-type network;

[0009] S3. solving a two-dimensional Poisson equation to obtain an average temperature;

[0010] S4. comparing the average temperature obtained by the Poisson equation with the node temperature in the thermal resistance network; iteratively adjusting the compensation thermal resistance unit until the temperature error of the two is within an acceptable range.

[0011] S5. Run the calibrated model, output the steady-state temperature.

[0012] The present application has the following beneficial effects compared with the prior art:

[0013] 1. The general thermal network model is based on one-dimensional heat conduction equation, and the heat flow is assumed to be uniform along a certain main direction (such as axial or radial direction). The introduction of compensation thermal resistance is mathematically equivalent to adding a "reverse heat flux regulator", which enables the node temperature to approximate the two-dimensional integral average temperature, thereby effectively correcting the distortion of the thermal network in the local two-dimensional area and significantly improving the reflection ability of the model to local hot spots and temperature gradient.

[0014] 2. Compared with directly introducing finite element method to solve the thermal field, the compensation thermal resistance model does not need to change the topology structure of the original thermal network, nor does it need to construct complex geometry or grid. By adjusting a certain thermal resistance value through numerical iteration, the order of magnitude of the model precision can be improved, and the calculation efficiency is almost unchanged. This method is especially suitable for the initial stage of relay design and parameter optimization stage, which can obtain approximate precision to the output of finite element method while ensuring the simulation speed.

[0015] 3. The compensation thermal resistance can be automatically adjusted by numerical comparison with the two-dimensional analytical solution, enabling the thermal network model to achieve "semi-self-learning" capability. Even under different working conditions (such as different current density, heat dissipation boundary change, etc.), the compensation thermal resistance value can be quickly reset according to the temperature error, realizing the dynamic correction and reuse of the model. Once the thermal resistance parameter is set in the traditional thermal network model, it cannot be adjusted according to the real thermal field feedback error, and the compensation thermal resistance mechanism compensates for this "rigid modeling" defect.

[0016] 4. The general thermal network can only provide the average temperature of the node, and cannot reflect the local maximum temperature, which is a fatal defect for high-power density devices such as relays, because many thermal failure behaviors (such as insulation breakdown, contact ablation) occur at the instantaneous hot spot. Through the compensation thermal resistance combined with the hot spot position and maximum temperature derived by the analytical model, the precise definition of key parameters such as temperature control strategy, thermal protection threshold, and life evaluation curve can be realized, providing strong support for practical application. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is the flowchart of the present application;

[0018] Figure 2 is the structure diagram of the electromagnetic system of the relay;

[0019] Figure 3 is the structure diagram of the contact system without shell;

[0020] Figure 4 is the overall structure diagram of the relay with shell;

[0021] Figure 5 is a thermal network model diagram of a relay structure;

[0022] Figure 6 is a schematic diagram of a relay coil cross section;

[0023] 1, coil; 2, coil holder; 3, magnetic conductor; 4, short yoke iron; 5, shaft holder; 6, magnetic steel; 7, outer yoke iron; 8, washer; 9, small shaft; 10, moving contact; 11, moving contact; 12, moving contact; 13, moving contact; 14, moving contact; 15, moving contact; 16, armature; 17, insulating block; 18, bottom plate; 19, damping piece; 20, fixed piece; 21, fixed piece; 22, support; 23, support; 24, support; 25, stationary contact; 26, stationary contact; 27, stationary contact; 28, stationary contact; 29, stationary contact; 30, stationary contact; 31, housing; 32, lead rod; 33, lead rod; 34, lead rod; 35, lead rod; 36, lead rod; 37, lead rod. DETAILED DESCRIPTION

[0024] In order to better understand the purpose, structure and function of the present application, the present application will be described in further detail below in conjunction with the accompanying drawings.

[0025] The present application is suitable for relay thermal analysis.

[0026] The present application provides a compensation thermal resistance regulation method applied to relay thermal network modeling, which adopts a hybrid modeling scheme combining a compensation thermal resistance structure and a numerical calibration method.

[0027] As shown in Figure 1 , the present application provides a compensation thermal resistance regulation method applied to relay thermal network modeling, which comprises the following steps:

[0028] S1. Establish a thermal network model of a relay structure, as shown in Figure 5 ; simplify the key heat flow paths in the relay, including the coil 1, the moving contacts 10-15, the stationary contacts 25-30, the armature 16, the yoke iron (short yoke iron 4, outer yoke iron 7), the insulating block 17, the coil holder 2, the magnetic steel, the frame, the damping piece 19, the bottom plate 18, etc., into a plurality of thermal resistance thermal networks. Each node represents the average temperature of a certain structure of the relay, and the thermal resistance elements between the nodes represent conduction or convection. The heat sources mainly come from the coil resistance loss, the contact arc heating, etc., which are distributed in the corresponding nodes as internal heat input;

[0029] The specific process is as follows:

[0030] Collect the geometric dimensions, material parameters and thermal coupling relationships of the key components of the relay, such as Figure 2 , Figure 3 , Figure 4The components include coil 1, moving contact 10-15, stationary contact 25-30, armature 16, yoke (short yoke 4, outer yoke 7), insulating block 17, coil holder 2, magnetic steel, frame, damping sheet 19 and bottom plate 18; the conduction thermal resistance and the convection thermal resistance are arranged between the structures; the coil resistance loss and the contact arc heat are arranged as distributed heat sources, a multi-directionally coupled thermal resistance network system is constructed, and R k , R μ are convection thermal resistances, and the others are conduction thermal resistances.

[0031] The heat sources are distributed in the model according to working characteristics, such as the coil resistance loss and the arc heat generated by contact operation, are arranged as heat flow sources, and a multi-directionally coupled thermal resistance network system is constructed.

[0032] S2. Inserting a compensation thermal resistance unit to establish a T-shaped network;

[0033] Based on the thermal network of the network relay obtained in S1 and based on the heat conduction theory, the regions of the thermal components involved in two-dimensional heat transfer in the thermal network are modeled in a polar coordinate system. The heat transfer paths in the circumferential direction (θ) and the radial direction (r) are represented by one-dimensional thermal resistance units respectively.

[0034] The Joule heat generated by the coil is embedded in the model as an internal heat source, and each node represents a local average temperature.

[0035] For the regions described in S2, a compensation thermal resistance unit is inserted in the thermal network in the corresponding direction of the thermal network model, that is, a compensation thermal resistance unit is inserted in the heat transfer paths in the circumferential direction (θ) and the radial direction (r) respectively, and R 1,θ and R 1,r are the compensation thermal resistances in the circumferential direction and the radial direction respectively, and the thermal resistance values are negative, which are used to correct the node temperature error in a mathematical sense, so as to construct a two-dimensional “T-shaped” thermal resistance network. The compensation thermal resistance makes the node temperature closer to the actual average temperature in the region, reflecting the local two-dimensional heat conduction effect. The initial compensation thermal resistance can be an empirical value or zero;

[0036] S3. Solving a two-dimensional Poisson equation to obtain an average temperature;

[0037] The two-dimensional Poisson equation is solved for the cross section of the thermal resistance network of the region involved in two-dimensional heat transfer in S2, and the boundary conditions are obtained from the output of the thermal network model. The average temperature of the region is solved in the form of Fourier series, which is taken as a reference of the actual thermal field;

[0038] The two-dimensional Poisson equation is solved as follows:

[0039]

[0040] In the formula, λ is the thermal conductivity of the coil.

[0041] r is the radial length; θ is the circumferential angle; Tw is the coil temperature;

[0042] where is the internal source density, calculated as:

[0043]

[0044] where I is the coil current; R0 is the coil resistance at a reference temperature; a is the resistance temperature coefficient; T is the operating temperature; T0 is the reference temperature.

[0045] r out is the coil outer diameter; r in is the coil inner diameter;

[0046] Boundary conditions are taken from the thermal network model output, as shown in Figure 6 , calculated as:

[0047]

[0048]

[0049] The average temperature is solved by Fourier series form.

[0050] S4. Compare the average temperature from the Poisson equation with the node temperature in the thermal resistance network; iteratively adjust the compensation thermal resistance unit until the temperature error of the two is within an acceptable range.

[0051] Compare the average temperature from the thermal network model output with the average temperature from the analytical model. If there is a positive deviation, i.e. the thermal network model result is higher than the analytical result, decrease the compensation thermal resistance value; otherwise, increase it appropriately. Through iterative adjustment of the compensation thermal resistance value, until the average temperature error of the two is within the set threshold, at which point the thermal network is calibrated;

[0052] The specific calculation is:

[0053] Compare the average temperature obtained in S3 with the thermal network model, and calculate the average temperature deviation between the two:

[0054]

[0055] where T w,L is the thermal network average temperature, T w,A is the average temperature solved by the Poisson equation

[0056] The update strategy for the compensation thermal resistance value according to the error direction is:

[0057] If ε > 0, i.e. the thermal network model prediction temperature is higher than the Poisson equation result, indicating that the thermal resistance model is too conservative (thermal resistance is too large), the compensation thermal resistance Rr,m the value of the number of iterations;

[0058] If ε < 0, i.e. the temperature of the hot network is too low, it means that the heat flux is overestimated, and R should be increased r,m value;

[0059] In each iteration, R r,m Adjust by 5% proportion.

[0060] S5. Run the calibrated model to output the steady-state temperature.

[0061] After completing the compensation thermal resistance calibration, re-run the thermal network model to obtain the steady-state temperature distribution of each thermal node inside the relay. This distribution takes into account both the efficiency of the model and the true characteristics of the two-dimensional thermal field, and can be used for subsequent analysis such as engineering thermal design, overheat protection criterion formulation, or thermal life evaluation.

[0062] Embodiment:

[0063] Taking a balanced force type sealed electromagnetic relay with three sets of conversion contacts as an example, this type of relay is composed of an electromagnetic system and a contact system, and the specific implementation steps are as follows:

[0064] STEP 1: Collect the required data such as size and material of the relay, and obtain the actual thermal coupling relationship between the main components inside the relay such as coil, moving and stationary contacts, armature, yoke, insulating block, coil holder, magnetic steel, frame, damping sheet and bottom plate, set the corresponding conduction and convection thermal resistance, and distribute the heat sources in the model according to the working characteristics, such as the resistance loss of the coil and the arc heat generated by the contact operation, set them as heat sources, to form a multi-directional coupling thermal resistance network system.

[0065] STEP 2: Based on the theory of heat conduction, for the thermal components involved in two-dimensional heat transfer in the thermal network, insert a compensation thermal resistance unit in the circumferential (θ) and radial (r) heat transfer path, and the thermal resistance value is negative, which is used to correct the node temperature error in the mathematical sense, and a two-dimensional "T-type" thermal resistance network is constructed. The initial compensation thermal resistance can be taken as an empirical value or set to zero.

[0066] STEP 3: Solve the two-dimensional Poisson equation for the cross section of the two-dimensional heat transfer area described in step two, and solve the average temperature by Fourier series.

[0067] STEP 4: Compare the average temperature obtained by solving the Poisson equation with the thermal network, and iterate the compensation thermal resistance in the thermal network until the error is within 5%.

[0068] STEP 5: After completing the compensation thermal resistance calibration, re-run the thermal network model to obtain the steady-state temperature distribution of each thermal node.

[0069] It is to be understood that the present application is described by way of example only, and that modifications or alterations can be made to the features and embodiments described without departing from the spirit and scope of the application. In addition, modifications can be made to the features and embodiments described to accommodate specific situations and materials without departing from the spirit and scope of the application. Accordingly, the application is not limited to the specific embodiments disclosed herein, but rather, the scope of the application includes all embodiments falling within the scope of the claims.

Claims

1. A compensation thermal resistance regulation method applied to a relay thermal network modeling, characterized in that: The method comprises the following steps: S1. Establish a thermal network model of the relay structure; The specific process is: collecting the geometric dimensions, material parameters and thermal coupling relationships of key components of the relay, including the coil, moving contact, static contact, armature, yoke, insulating block, coil holder, magnetic steel, frame, damping sheet and bottom plate; Conductive thermal resistance and convective thermal resistance are set between structures; the coil resistance loss and contact arc heat are set as distributed heat sources, and a multi-directionally coupled thermal resistance network system is constructed, wherein the heat sources are distributed in the model according to the working characteristics and are set as heat flow sources to form the multi-directionally coupled thermal resistance network system; S2. Insert a compensation thermal resistance unit to establish a T-shaped network; The specific process is: on the basis of the network relay thermal network obtained in S1, the regions of thermal components involving two-dimensional heat transfer are modeled in a polar coordinate system, wherein the heat transfer paths in the circumferential direction θ and the radial direction r are represented by one-dimensional thermal resistance units, The Joule heat generated by the coil is embedded in the model as an internal heat source, and each node represents a local average temperature; For the regions of thermal components involving two-dimensional heat transfer, a compensation thermal resistance unit is inserted in the heat transfer paths in the circumferential direction θ and the radial direction r, and the thermal resistance value is negative, which is used to correct the node temperature error in a mathematical sense, so as to construct a two-dimensional "T-shaped" thermal resistance network; S3. Solve the two-dimensional Poisson equation to obtain the average temperature; The specific process is: solving the two-dimensional Poisson equation for the thermal resistance network section involving two-dimensional heat transfer in S2, and the boundary conditions are taken from the output of the thermal network model, and the average temperature of the region is solved in the form of Fourier series, which is taken as the reference of the actual thermal field; S4. Compare the average temperature obtained by the Poisson equation with the node temperature in the thermal resistance network; iteratively adjust the compensation thermal resistance unit until the temperature error of the two is within an acceptable range; S5. Run the calibrated model to output the steady-state temperature.

2. The compensation thermal resistance regulating method applied to the thermal network modeling of a relay according to claim 1, characterized in that: In S3, the process of solving the two-dimensional Poisson equation is: wherein K is the coil thermal conductivity, r is the radial length; θ is the circumferential angle; T w is the coil temperature; wherein is the internal source density, calculated by the formula: where I is the coil current; R0 is the coil resistance at a reference temperature; a is the resistance temperature coefficient; T is the operating temperature; T0 is the reference temperature; r out is the coil outer diameter; r in is the coil inner diameter; The boundary conditions are taken from the output of the thermal network model, and the calculation formula is as follows: The average temperature is solved in the form of Fourier series.

3. The compensation thermal resistance regulating method applied to the thermal network modeling of a relay according to claim 1, characterized in that: In S4, the average temperature deviation between the average temperature obtained in S3 and the thermal network model is calculated: where T w,L is the average temperature of the thermal network, T w,A is the average temperature of the Poisson equation solution; The error direction is used to update the compensation thermal resistance value: If ε > 0, i.e. the thermal network model predicts a higher temperature than the Poisson equation, it indicates that the thermal resistance model is too conservative and the value of the compensation thermal resistance R r,m should be reduced. If ε < 0, i.e. the temperature of the hot network is too low, it means that the heat flux is overestimated and R should be increased r,m value. In each iteration, R r,m Adjustment is made in 5% increments.

4. The compensation thermal resistance regulating method applied to the thermal network modeling of a relay according to claim 3, characterized in that: The specific process of S5 is: after the compensation thermal resistance is calibrated, the thermal network model is run again to obtain the steady-state temperature distribution of each thermal node inside the relay.

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