Compensation thermal resistance regulation and control method applied to relay thermal network modeling

Abstract

The invention discloses a compensation thermal resistance regulation and control 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 local temperature field prediction and difficult in hot spot recognition in relay thermal analysis. Comprising the steps of S1, establishing a thermal network model of a relay structure; s2, a compensation thermal resistance unit is inserted, and a T-type network is established; s3, solving a two-dimensional Poisson equation to obtain an average temperature; s4, comparing the average temperature with the node temperature in the thermal resistance network; iteratively adjusting the compensation thermal resistance unit until the temperature error of the compensation thermal resistance unit and the compensation thermal resistance unit is within an acceptable range; and S5, the calibrated model is operated, and the steady-state temperature is output. The introduction of the compensation thermal resistance is mathematically equivalent to the addition of a reverse heat flux regulator, so that the node temperature can be approximate to the two-dimensional integral average temperature, the distortion of the thermal network in a local two-dimensional region is effectively corrected, and the reflection capability of the model to local hot spots and temperature gradients is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal modeling in electromagnetic and thermal coupling systems, and particularly relates to a compensating thermal resistance control method applied to relay thermal network modeling. Background Art

[0002] As a key actuator in electromagnetic control systems, relays often operate with significant current switching, generating complex heat distribution within their coils, cores, and contacts. Especially under high-frequency, high-load conditions or continuous power-on conditions, the internal heat accumulation effect is significant. This not only causes aging of the coil insulation and degradation of magnetic properties, but also accelerates contact erosion and welding, leading to a decrease in reliability or even failure. Therefore, accurately understanding the temperature rise distribution and hotspot locations within relays is crucial for optimizing their structural design and predicting their service life.

[0003] While finite element thermal simulation can currently provide highly accurate temperature field distribution results in relay thermal analysis, its high computational cost and complex modeling limit its widespread application in the early stages of product design. In contrast, thermal network models based on one-dimensional heat transfer theory are widely used for modeling internal thermal paths in relays due to their simplicity and efficiency. However, the core assumption of thermal network models is that heat flow proceeds in a single direction, ignoring the multidimensional temperature gradients caused by heat conduction, convection, and local heat sources in actual structures. This leads to significant deviations in the estimated local hotspots and average temperatures, particularly in coil windings. Summary of the Invention

[0004] In order to solve the problems of inaccurate prediction of local temperature fields and difficulty in identifying hot spots in traditional thermal network models in relay thermal analysis, the present invention provides a compensating thermal resistance control method applied to relay thermal network modeling.

[0005] The technical solution adopted by the present invention is:

[0006] A compensation thermal resistance control method applied to relay thermal network modeling includes the following steps:

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

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

[0009] S3. Solve the two-dimensional Poisson equation to obtain the average temperature;

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

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

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] 1. Conventional thermal network models are based on one-dimensional heat conduction equations, which assume uniform heat flow along a primary direction (such as the axial or radial direction). The introduction of compensating thermal resistance is mathematically equivalent to adding a "reverse heat flux regulator," allowing node temperatures to approximate the two-dimensional integrated average temperature. This effectively corrects thermal network distortion in local two-dimensional regions and significantly improves the model's ability to reflect local hot spots and temperature gradients.

[0014] 2. Compared to directly implementing the finite element method to solve the thermal field, the compensated thermal resistance model does not require changing the original thermal network topology or constructing complex geometry or meshes. Simply by numerically iteratively adjusting a specific thermal resistance value, the model accuracy can be improved by orders of magnitude, with virtually no change in computational efficiency. This method is particularly suitable for the early stages of relay design and parameter optimization, achieving output accuracy similar to that of the finite element method while maintaining simulation speed.

[0015] 3. The compensating thermal resistance can be automatically adjusted by comparing the values ​​with the two-dimensional analytical solution, enabling the thermal network model to achieve "semi-self-learning" capabilities. Even under different operating conditions (such as varying current densities, changes in the heat dissipation boundary, etc.), the compensating thermal resistance value can be quickly reset based on temperature errors, enabling dynamic model correction and reuse. Traditional thermal network models, once the thermal resistance parameters are set, cannot adjust the error based on actual thermal field feedback. The compensating thermal resistance mechanism overcomes this "rigid modeling" shortcoming.

[0016] 4. Conventional thermal networks only provide average node temperatures and fail to reflect local maximum temperatures. This is a critical flaw for high-power density devices like relays, as many thermal failures (such as insulation breakdown and contact erosion) occur at transient hotspots. By combining thermal resistance compensation with the hotspot locations and maximum temperatures derived from analytical models, key parameters such as temperature control strategies, thermal protection thresholds, and life assessment curves can be precisely defined, providing strong support for practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of the present invention;

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

[0019] Figure 3 This is a structural diagram of the contact system without a housing;

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

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

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

[0023] Among them: 1. Coil; 2. Coil frame; 3. Magnetizer; 4. Short yoke; 5. Shaft frame; 6. Magnet; 7. Outer yoke; 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 plate; 20. Fixed plate; 21. Fixed plate; 22. Support; 23. Support; 24. Support; 25. Static contact; 26. Static contact; 27. Static contact; 28. Static contact; 29. ​​Static contact; 30. Static 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 invention, the present invention is further described in detail below with reference to the accompanying drawings.

[0025] The present invention is applicable to relay thermal analysis.

[0026] The present invention provides a compensation thermal resistance control method applied to relay thermal network modeling, which adopts a hybrid modeling scheme based on the combination of a compensation thermal resistance structure and a numerical calibration method.

[0027] like Figure 1 As shown, the present invention provides a compensation thermal resistance control method applied to relay thermal network modeling, comprising the following steps:

[0028] S1. Establish a thermal network model of the relay structure, such as Figure 5 As shown in the figure, the key heat flow paths within the relay—including the coil 1, movable contacts 10-15, stationary contacts 25-30, armature 16, yokes (short yoke 4, outer yoke 7), insulating block 17, coil former 2, magnet, frame, damping plate 19, base plate 18, etc.—are simplified into multiple thermal resistance networks. Each node represents the average temperature of a certain structure in the relay, and the thermal resistance elements between nodes represent conduction or convection. The heat sources mainly come from coil resistance losses, contact arc heating, etc., which are distributed in the corresponding nodes as internal heat input.

[0029] The specific process is:

[0030] Collect the geometric dimensions, material parameters and thermal coupling relationships of key relay components (such as Figure 2 、 Figure 3 、 Figure 4As shown in the figure), the components include coil 1, moving contacts 10-15, static contacts 25-30, armature 16, yoke (short yoke 4, outer yoke 7), insulating block 17, coil frame 2, magnetic steel, frame, damping plate 19 and bottom plate 18; conduction thermal resistance and convection thermal resistance are set between each structure; the coil resistance loss and contact arc heat are set as distributed heat sources to construct a multi-directional coupled thermal resistance network system. k 、R μ is the convection thermal resistance, and the rest are conduction thermal resistance.

[0031] Among them, the heat sources are distributed in the model according to the working characteristics, such as the resistance loss of the coil, the arc heat generated by the contact operation, etc., which are set as heat flow sources to form a multi-directional coupled thermal resistance network system.

[0032] S2. Insert the compensation thermal resistance unit to establish a T-type network;

[0033] Based on the network relay thermal network obtained in S1 and heat conduction theory, the thermal component regions involved in two-dimensional heat transfer in the thermal network were modeled using a polar coordinate system. The circumferential (θ) and radial (r) heat transfer paths were each represented by a one-dimensional thermal resistance unit.

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

[0035] For the area described in S2, a compensation thermal resistance unit is inserted into the thermal network in the corresponding direction of the thermal network model, that is, a compensation thermal resistance unit is inserted into the circumferential (θ) and radial (r) heat transfer paths respectively. 1,θ With R 1,r The circumferential and radial compensation thermal resistances are negative, mathematically correcting for node temperature errors and thus constructing a two-dimensional "T-shaped" thermal resistance network. The compensation thermal resistances bring the node temperature closer to the actual average temperature within the region, reflecting the local two-dimensional heat conduction effect. The initial compensation thermal resistance can be an empirical value or set to zero.

[0036] S3. Solve the two-dimensional Poisson equation to obtain the average temperature;

[0037] Solve the 2D Poisson equation for the thermal resistance network section in S2 involving the 2D heat transfer region, with boundary conditions taken from the thermal network model output. Obtain the average temperature of this region using the Fourier series form and use it as a reference for the actual thermal field.

[0038] Solve the Poisson equation in two dimensions:

[0039]

[0040] Where 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] in is the internal source density, and the calculation formula is:

[0043]

[0044] Where I is the coil current; R0 is the coil resistance at the reference temperature; α is the resistance temperature coefficient; T is the operating temperature; and T0 is the reference temperature.

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

[0046] The boundary conditions are taken from the thermal network model output, such as Figure 6 As shown, the calculation formula is as follows:

[0047]

[0048]

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

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

[0051] Compare the average temperature output by the thermal network model with the average temperature of the analytical model. If there is a positive deviation, that is, the thermal network model output is higher than the analytical output, reduce the compensation thermal resistance value; otherwise, increase it appropriately. Adjust the compensation thermal resistance value through iterative cycles until the average temperature error between the two is within the set threshold. At this 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 average temperature of the thermal network, T w,A Average temperature for solving Poisson's equation

[0056] Update strategy for compensating thermal resistance value according to error direction:

[0057] If ε > 0, the temperature predicted by the thermal network model is higher than the Poisson equation result, indicating that the thermal resistance model is too conservative (the thermal resistance is too large), and the compensation thermal resistance R should be appropriately reduced.r,m The value of

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

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

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

[0061] After calibrating the compensated thermal resistance, rerun the thermal network model to obtain the steady-state temperature distribution of each thermal node within the relay. This distribution balances model efficiency with the realistic characteristics of the two-dimensional thermal field and can be used for subsequent analysis such as engineering thermal design, overheat protection criteria development, and thermal life assessment.

[0062] Example:

[0063] Taking a balanced force sealed electromagnetic relay with three sets of switching contacts as an example, this type of relay consists of two parts: the electromagnetic system and the contact system. The specific implementation steps are as follows:

[0064] STEP 1: Collect the required data on relay dimensions, materials, and so on. Based on the main internal components of the relay—such as the coil, moving and static contacts, armature, yoke, insulating block, coil frame, magnet, frame, damping plate, and base plate—obtain the actual thermal coupling relationship between each structure and set the corresponding conduction and convection thermal resistances. Heat sources are distributed in the model based on the operating characteristics, such as the coil resistance loss and the arc heat generated by contact operation. These are set as heat flow sources to form a multi-directional coupled thermal resistance network system.

[0065] STEP 2: Based on heat conduction theory, for thermal components involved in two-dimensional heat transfer in the thermal network, insert a compensating thermal resistance element in the circumferential (θ) and radial (r) heat transfer paths. This element's thermal resistance is negative, mathematically correcting for node temperature errors. This constructs a two-dimensional "T-shaped" thermal resistance network. The initial compensating thermal resistance can be 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 region described in step 2, and solve the average temperature using the Fourier series form.

[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 between the two is within 5%.

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

[0069] It will be understood that the present invention is described by way of some embodiments, and it will be appreciated by those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by the present invention.

Claims

1. A method for controlling thermal resistance compensation applied to relay thermal network modeling, characterized by: The following steps are involved: S1. Establish a thermal network model of the relay structure; S2. Insert the compensation thermal resistance unit to establish a T-type network; S3. Solve the two-dimensional Poisson equation to obtain the average temperature; S4. Compare the average temperature obtained from the Poisson equation with the node temperatures in the thermal resistance network; Iteratively adjust the compensation thermal resistance unit until the temperature error between the two is within an acceptable range; S5. Run the calibrated model and output the steady-state temperature.

2. The method for controlling the compensating thermal resistance applied to relay thermal network modeling according to claim 1, characterized in that: The S1 establishes a thermal network model of the relay structure, specifically by collecting geometric dimensions, material parameters, and thermal coupling relationships of key relay components, including coils, moving contacts, static contacts, armatures, yokes, insulating blocks, coil frames, magnets, frames, damping plates, and base plates; Conduction thermal resistance and convection thermal resistance are set between each structure; the coil resistance loss and contact arc heat are set as distributed heat sources to construct a multi-directional coupled thermal resistance network system, in which the heat sources are distributed in the model according to the working characteristics and set as heat flow sources to form a multi-directional coupled thermal resistance network system.

3. The method for controlling the compensating thermal resistance applied to relay thermal network modeling according to claim 2, characterized in that: The specific process of S2 is: Based on the network relay thermal network obtained by S1, the thermal component area involving two-dimensional heat transfer in the thermal network is modeled in a polar coordinate system, where the heat transfer paths in the circumferential direction θ and radial direction r are represented by one-dimensional thermal resistance units respectively. The Joule heat generated by the coil is embedded in the model as an internal heat source, and each node represents the local average temperature; For the hot component area with two-dimensional heat transfer, a compensating thermal resistance unit with a negative thermal resistance value is inserted in the heat transfer path in the circumferential direction θ and the radial direction r respectively. This is used to mathematically correct the node temperature error, thereby constructing a two-dimensional "T-shaped" thermal resistance network.

4. The method for controlling the compensating thermal resistance applied to relay thermal network modeling according to claim 3, characterized in that: The specific process of S3 is: solving the two-dimensional Poisson equation for the thermal resistance network section involving the two-dimensional heat transfer area in S2, the boundary conditions are taken from the output of the thermal network model, and the average temperature of the area is solved in the form of Fourier series, which is used as a reference for the actual thermal field.

5. The method for controlling the compensating thermal resistance applied to relay thermal network modeling according to claim 4, characterized in that: In S3, the process of solving the two-dimensional Poisson equation is: Where λ is the coil thermal conductivity, r is the radial length, θ is the circumferential angle, and Tw is the coil temperature. in is the internal source density, and the calculation formula is: Where, I is the coil current; R0 is the coil resistance at the reference temperature; α is the resistance temperature coefficient; T is the operating temperature; T0 is the reference temperature; r out is the outer diameter of the coil; r in is the inner diameter of the coil; The boundary conditions are taken from the thermal network model output and are calculated as follows: The average temperature is solved using the Fourier series form.

6. The method for controlling the compensating thermal resistance applied to relay thermal network modeling according to claim 4, characterized in that: In S4, the average temperature obtained in S3 is compared with the thermal network model, and the average temperature deviation between the two is calculated: Where, T w,L is the average temperature of the thermal network, T w,A The average temperature for which Poisson's equation is solved; Update strategy for compensating thermal resistance value according to error direction: If ε > 0, the temperature predicted by the thermal network model is higher than the Poisson equation result, indicating that the thermal resistance model is too conservative and the compensation thermal resistance R should be appropriately reduced. r,m The numerical value of If ε < 0, the heat network temperature is too low, indicating that the heat flux is overestimated, and R should be increased. r,m value; In each iteration, R r,m Adjust by 5%.

7. The method for controlling the compensating thermal resistance applied to relay thermal network modeling according to claim 6, characterized in that: The specific process of S5 is: after completing the compensation thermal resistance calibration, re-running the thermal network model to obtain the steady-state temperature distribution of each thermal node inside the relay.

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