A life determination method and system for high-voltage direct-current contactors

Abstract

This invention relates to the field of electronic device condition assessment technology, and particularly to a method and system for determining the lifespan of high-voltage DC contactors. The method includes the following steps: during each switching operation of the DC contactor, the arc duration, peak current, contact temperature rise, and pull-in delay time are simultaneously collected to form a set of physical quantity data for a single operation; a thermal damage component is calculated based on the contact temperature rise and arc duration; an electrical damage component is obtained by multiplying the square of the peak current by the contact resistance measured in real time; and a mechanical damage component is determined based on the pull-in delay time; a weighted sum of the thermal damage component, electrical damage component, and mechanical damage component is calculated and recorded as the base damage value. This invention performs calculations based on real-time field data, accurately reflecting the actual degradation process under different operating currents, operating frequencies, and temperature rise conditions, thus improving the accuracy of lifespan prediction.

Description

Technical Field

[0001] This invention relates to the field of electronic device condition assessment technology, and in particular to a method and system for determining the lifespan of a high-voltage DC contactor. Background Technology

[0002] DC contactors are critical electrical control units widely used in high-voltage DC power distribution environments. They are responsible for frequently breaking and closing high-voltage, high-current circuits. Their contacts are susceptible to degradation under the combined effects of arcing, temperature cycling, and mechanical wear, including contact erosion, increased resistance, metal migration, and welding risks. These degradation processes are highly random and irreversible, resulting in a significant difference between the actual service life and the nominal life of the contactor. Failure to accurately assess the contactor's health status can lead to unexpected equipment failures during operation, potentially causing system malfunctions or even major safety accidents.

[0003] In existing technologies, the assessment of the lifespan of high-voltage DC contactors is mainly achieved through the following methods: first, relying on laboratory type tests and using standardized accelerated aging tests to extrapolate lifespan models; second, performing maintenance at the equipment operating site based on a fixed-cycle replacement strategy. Both of these methods have significant limitations. Laboratory accelerated tests differ greatly from actual operating conditions, making it difficult to reflect the true degradation path of the contactor in complex environments; fixed-cycle replacement strategies cannot be dynamically adjusted according to the actual load of the equipment, easily leading to two extreme situations: premature replacement resulting in resource waste, and delayed replacement leading to the risk of sudden failure. Furthermore, traditional testing methods mostly use single indicators (such as resistance, temperature rise, or number of operations) for judgment, without considering the comprehensive damage accumulation process under multi-physics coupling, resulting in low accuracy in lifespan prediction. Summary of the Invention

[0004] Therefore, it is necessary for the present invention to provide a method and system for determining the lifespan of a high-voltage DC contactor, in order to solve at least one of the above-mentioned technical problems.

[0005] To achieve the above objectives, a method for determining the lifespan of a high-voltage DC contactor includes the following steps: Step S1: During each switching operation of the DC contactor, the arc duration, peak current, contact temperature rise, and engagement delay time are collected synchronously to form a set of physical quantity data for a single operation. Step S2: Calculate the thermal damage component based on the contact temperature rise and arc duration, multiply the square of the peak current by the contact resistance measured in real time to obtain the electrical damage component, and determine the mechanical damage component based on the pull-in delay time. Step S3: Calculate the weighted sum of the thermal damage component, electrical damage component, and mechanical damage component, and record it as the basic damage value; determine the coupling amplification factor through the numerical relationship of the three damage components, and multiply the basic damage value by the coupling amplification factor to obtain the equivalent damage value; Step S4: The equivalent damage value of continuous operation is used as the cumulative damage index. The ratio of the real-time cumulative damage index to the pre-acquired damage threshold is calculated, and the remaining life prediction value of the contactor is output.

[0006] The present invention also provides a life determination system for a high-voltage DC contactor, used to execute the above-described life determination method for a high-voltage DC contactor, wherein the life determination system for a high-voltage DC contactor includes: The physical quantity acquisition module is used to synchronously acquire the arc duration, peak current, contact temperature rise and closing delay time during each switching operation of the DC contactor, forming a set of physical quantity data for a single operation. The damage component calculation module is used to calculate the thermal damage component based on the contact temperature rise and arc duration, multiply the square of the peak current by the contact resistance measured in real time to obtain the electrical damage component, and determine the mechanical damage component based on the pull-in delay time. The equivalent damage quantification module is used to calculate the weighted sum of thermal damage components, electrical damage components, and mechanical damage components, which is recorded as the base damage value. The coupling amplification factor is determined by the numerical relationship of the three damage components, and the equivalent damage value is obtained by multiplying the base damage value by the coupling amplification factor. The life prediction output module is used to accumulate the equivalent damage value of continuous operation as the cumulative damage index. It calculates the ratio between the real-time cumulative damage index and the pre-acquired damage threshold, and outputs the predicted value of the remaining life of the contactor.

[0007] The high-voltage DC contactor life determination method provided by this invention synchronously collects key physical quantities such as arc duration, peak current, contact temperature rise, and pull-in delay time during each switching operation. This allows for precise quantification of thermal, electrical, and mechanical damage to the contactor during each operation, thus generating comprehensive single-operation damage data. The method analyzes the temperature rise changes caused by the arc in stages, weighting the contributions of temperature rise in the rapid heating, high-temperature maintenance, and slow cooling stages to make the thermal damage assessment more scientific and reasonable. Simultaneously, it combines real-time measurements of peak current and contact resistance to calculate electrical damage, considering resistive losses and arc energy consumption, accurately reflecting the degree of contact wear caused by electrical load. The mechanical damage component is quantified by comprehensively analyzing the pull-in delay time offset and operating frequency, and applying linear or exponential amplification factors respectively.

[0008] Furthermore, through coupled analysis of the thermal, electrical, and mechanical damage components, this method can identify thermo-electrical and mechanical-thermal synergistic damage states, and dynamically adjust the coupling amplification coefficient according to different damage states, thereby enabling the equivalent damage value to more comprehensively reflect the actual loss of the contactor. During continuous operation, this method, through the accumulation and weighting of the equivalent damage value, can give higher weight to recent high-load operations, reasonably reflect the combined impact of historical and current operations on accumulated damage, and respond promptly to abnormal load conditions through an accelerated accumulation mode.

[0009] By calculating a threshold using cumulative damage data obtained from accelerated aging tests and comparing the real-time cumulative damage index with the threshold, the remaining lifespan of the contactor can be dynamically quantified, enabling accurate prediction of the remaining number of operations. Overall, this method, through multi-dimensional physical quantity acquisition, phased and categorized damage quantification, dynamic coupling analysis, and real-time accumulation compared with the threshold, can comprehensively, accurately, and dynamically assess the operating status and lifespan of high-voltage DC contactors. This provides a scientific basis for equipment maintenance decisions and preventative replacement, improves equipment reliability, reduces failure risks, and minimizes unnecessary maintenance costs, ultimately achieving efficient and safe power system management. Attached Figure Description

[0010] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the steps in the life determination method for a high-voltage DC contactor according to the present invention. Figure 2 This is a schematic diagram illustrating the calculation of thermal damage components according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the electrical damage component calculation process according to an embodiment of the present invention; Figure 4 This is a schematic diagram of a module for determining the lifespan of a high-voltage DC contactor according to the present invention. Detailed Implementation

[0011] The technical method of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0012] Furthermore, the accompanying drawings are merely illustrative of the invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor methods and / or microcontroller methods.

[0013] It should be understood that although the terms "first," "second," etc., may be used herein to describe various units, these units should not be limited by these terms. These terms are used merely to distinguish one unit from another. For example, without departing from the scope of the exemplary embodiments, a first unit may be referred to as a second unit, and similarly, a second unit may be referred to as a first unit. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0014] To achieve the above objectives, please refer to Figures 1 to 4 This invention provides a method for determining the lifespan of a high-voltage DC contactor, the method comprising the following steps: Step S1: During each switching operation of the DC contactor, the arc duration, peak current, contact temperature rise, and engagement delay time are collected synchronously to form a set of physical quantity data for a single operation. Step S2: Calculate the thermal damage component based on the contact temperature rise and arc duration, multiply the square of the peak current by the contact resistance measured in real time to obtain the electrical damage component, and determine the mechanical damage component based on the pull-in delay time. Step S3: Calculate the weighted sum of the thermal damage component, electrical damage component, and mechanical damage component, and record it as the basic damage value; determine the coupling amplification factor through the numerical relationship of the three damage components, and multiply the basic damage value by the coupling amplification factor to obtain the equivalent damage value; Step S4: The equivalent damage value of continuous operation is used as the cumulative damage index. The ratio of the real-time cumulative damage index to the pre-acquired damage threshold is calculated, and the remaining life prediction value of the contactor is output.

[0015] Furthermore, step S2, which calculates the thermal damage component based on the contact temperature rise and arc duration, includes: The duration of the electric arc is divided into three periods according to the characteristics of temperature rise: rapid heating stage, high temperature maintenance stage, and slow cooling stage. In one embodiment, the temperature rise-time curve acquired during the switching process is smoothed, and then the instantaneous rate of change of temperature rise is calculated. When the rate of change is greater than a preset rise threshold, the interval is divided into a rapid heating stage; when the rate of change of temperature rise is within a set small fluctuation range, the interval is marked as a high temperature maintenance stage; when the rate of change is less than a preset fall threshold, it is identified as a slow cooling stage.

[0016] For example, for an electric arc process lasting 20ms, if the temperature rises from 30°C to 120°C in the first 6ms, this segment is identified as the rapid heating phase; if the temperature rise fluctuates around 120°C in the following 10ms, it is identified as the high temperature maintenance phase; and if the temperature rise drops from 120°C to 70°C in the last 4ms, it is marked as the slow cooling phase.

[0017] It should be noted that the division of the three stages is not a fixed duration, but is based entirely on dynamic identification of temperature rise change characteristics, thereby ensuring adaptability to arcs under different operating conditions.

[0018] The average temperature rise values ​​of the rapid heating phase, the high temperature maintenance phase, and the slow cooling phase were extracted separately. In one embodiment, after dividing the arc duration into stages, all temperature rise sampling points within the rapid heating stage, the high-temperature maintenance stage, and the slow cooling stage are statistically analyzed, and the average temperature rise value of each stage is calculated using an arithmetic mean method. For the time boundary of each stage, it can be automatically extracted based on the segmentation results obtained in the previous step, and then the temperature rise data within the time period is averaged.

[0019] For example, if 30 temperature rise data points are collected during the rapid heating phase, and the temperature rise values ​​are between 30℃ and 120℃, then averaging these 30 data points will give the average temperature rise during the rapid heating phase. Similarly, the average temperature rise during the high-temperature maintenance phase and the slow cooling phase can be obtained using the same method.

[0020] The average temperature rise during the high-temperature maintenance phase is multiplied by the corresponding time length to obtain the main thermal damage contribution. The average temperature rise during the rapid heating phase and the slow cooling phase are multiplied by the corresponding time length and the preset phase weighting coefficient, respectively, and then added together to obtain the secondary thermal damage contribution. In one embodiment, the contribution of the high-temperature maintenance phase to thermal damage can be considered as the primary source of thermal damage. Therefore, the average temperature rise during the high-temperature maintenance phase is directly multiplied by the duration of that phase to obtain the primary thermal damage contribution. Meanwhile, for the rapid heating phase and the slow cooling phase, since the temperature rise fluctuations are large and their impact on the thermal damage to the contact material is relatively secondary, the average temperature rise during these two phases can be multiplied by the corresponding duration, then multiplied by their respective preset phase weighting coefficients, and finally the two secondary contributions are added together to obtain the secondary thermal damage contribution.

[0021] For example, if the average temperature rise during the high-temperature maintenance phase is 120°C and the duration is 10ms, the primary contribution is 120 × 10; if the average temperature rise during the rapid heating phase is 75°C and the duration is 6ms with a weighting coefficient of 0.6, the contribution is 75 × 6 × 0.6; and if the average temperature rise during the slow cooling phase is 70°C and the duration is 4ms with a weighting of 0.5, the contribution is 70 × 4 × 0.5. The sum of the two secondary contributions is the secondary thermal damage contribution.

[0022] The thermal damage component for a single operation is obtained by summing the contributions of primary and secondary thermal damage.

[0023] In one embodiment, after obtaining the primary and secondary thermal damage contributions, these two parts can be summed to obtain the thermal damage component of a single on / off operation. This summation process uses a linear superposition method, without introducing any additional nonlinear coefficients, ensuring the interpretability of the computational model.

[0024] For example, in the aforementioned numerical example, the primary thermal damage contribution is 120 × 10, and its value is assumed to be 1200; the secondary thermal damage contribution (the sum of the contributions of rapid heating and slow cooling) is assumed to be 420. The sum of the two is 1620, which can be used as the thermal damage component of this on / off operation.

[0025] See Figure 2 In the thermal damage component calculation diagram provided by this invention, the temperature rise at the contact point over time is divided into three time periods: a rapid heating phase, a high-temperature maintenance phase, and a slow cooling phase. Specifically, during the rapid heating phase, the temperature rise increases from T1 to T3, corresponding to a time interval of [missing information]. During the high-temperature maintenance phase, the temperature rise remained around T2, corresponding to a time of... During the slow cooling phase, the temperature rise decreases from T2 to ambient temperature, corresponding to a time interval of [time period missing]. The calculation of thermal damage components includes the primary thermal damage contribution and the secondary thermal damage contribution. The primary thermal damage contribution is calculated by multiplying the average temperature rise T2 during the high-temperature maintenance phase by its duration. The contribution of secondary thermal damage is calculated by multiplying the average temperature rise T1 during the rapid heating phase and the average temperature rise T3 during the slow cooling phase by the corresponding time lengths. After weighting and summing, the thermal damage component for a single operation is obtained by adding the primary thermal damage contribution and the secondary thermal damage contribution, i.e., T2× .

[0026] For example, in a certain operation If the stage weights w1=0.8 and w3=0.6, the thermal damage components of this operation can be calculated by substituting them into the formula. During the calculation of the thermal damage components, the time length and temperature rise of each stage should be determined based on the actual sampling data, and the stage weight coefficients can be preset based on material properties and empirical data.

[0027] Furthermore, in step S2, multiplying the square of the peak current by the contact resistance measured in real time to obtain the electrical damage component includes: The contact resistance value is measured in real time before and after the switching action, and the difference between the resistance value after the action and the resistance value before the action is used as the resistance increment. In one embodiment, before each switching operation of the DC contactor, a weak test current is applied and the corresponding voltage drop is collected to measure the resistance value of the contacts before the operation, thus obtaining the reference contact resistance at the beginning of the operation. After the switching operation is completed, the system applies the same amplitude test current again and collects a new voltage drop to obtain the contact resistance value after the operation. After completing the two measurements, the contact resistance value after the operation is subtracted from the contact resistance value before the operation to obtain the contact resistance increment caused by the operation.

[0028] For example, if the contact resistance is measured to be 2.5mΩ before operation. The measured length after the movement was 3.0m. Then the resistance increment is 0.5m. .

[0029] Multiplying the square of the peak current by the resistance increment yields the resistive power loss, and multiplying the resistive power loss by the arc duration yields the resistive energy loss. In one embodiment, after obtaining the resistance increment, the resistive loss is calculated by combining it with the peak current generated by the current switching action. First, the square of the peak current is multiplied by the resistance increment to obtain the resistive loss power. Then, the resistive loss power is multiplied by the arc duration to obtain the resistive loss energy.

[0030] For example, if the peak current is 150A and the resistance increment is... Then the resistive power loss is ×0.0005=11.25W; if the arc duration is 20ms, then the resistive energy loss is 11.25×0.02=0.225J.

[0031] The arc power is obtained by measuring the product of the arc voltage and the peak current, and then multiplied by the arc duration to obtain the arc energy consumption. In one embodiment, the arc power can be obtained by simultaneously measuring the arc voltage and peak current during the arc generation process. The arc voltage can be detected in real time by a voltage acquisition module during the arc switching phase, while the peak current can be accurately recorded by a current sensor. Once the two measurements are obtained, the arc power can be obtained by multiplying them; multiplying the arc power by the arc duration yields the energy consumed by the arc during this operation.

[0032] For example, if the arc voltage is 45V and the peak current is 150A, then the arc power is 45×150=6750W; if the arc duration is still 20ms, then the energy consumed by the arc is 6750×0.02=135J.

[0033] The electrical damage component of a single operation is obtained by adding the resistive energy loss to the arc energy consumption.

[0034] In one embodiment, after obtaining the resistive energy loss and the arc energy consumption, the two are added together linearly to obtain the electrical damage component of a single operation. Since both resistive energy loss and arc energy directly affect the contact material, their summation can effectively reflect the comprehensive impact of electrical factors on contact life.

[0035] For example, if the resistive energy loss is 0.225J and the arc energy consumption is 135J, then the electrical damage component of a single operation is 135.225J.

[0036] See Figure 3 In the schematic diagram of the electrical damage component calculation process provided by this invention, the resistance value of the DC contactor contacts is first measured, and the resistance R1 before operation and the resistance R2 after operation are obtained respectively. Then, the resistance increment is calculated. Based on this, by using peak current Multiplying the square of the resistance increment by the resistive power loss yields the resistive power loss, which is then multiplied by the arc duration to obtain the resistive energy loss. Simultaneously, the arc power is obtained by measuring the product of the arc voltage and peak current, and then multiplied by the arc duration to obtain the arc energy consumption. Finally, the resistive energy loss and arc energy consumption are added together to obtain the electrical damage component of a single operation. For example, if the contact resistance of a DC contactor is 0.5mΩ before operation and 0.55mΩ after operation, with a peak current of 1000A and an arc duration of 5ms, the electrical damage component of that operation can be obtained using the above calculation method.

[0037] Furthermore, in step S2, multiplying the pull-in delay time offset by the operating frequency to obtain the mechanical damage component includes: Calculate the difference between the current pull-in delay time and the standard pull-in time of the DC contactor to obtain the pull-in delay time offset; In one embodiment, the time between the start of the engagement command and the completion of contact engagement is recorded using a high-precision timestamp during each on / off operation, thus obtaining the actual engagement delay time for this operation; the standard engagement time of the DC contactor is obtained and stored in advance from the factory calibration data or field calibration test of the DC contactor as a reference value; the difference between the actual engagement delay time and the standard engagement time is used to obtain the engagement delay time offset (which can be positive or negative).

[0038] For example, if the standard pull-in time of a certain type of contactor is 0.010 seconds (10 milliseconds), and the actual pull-in delay measured in this study is 0.012 seconds (12 milliseconds), then the pull-in delay time offset is 0.002 seconds (2 milliseconds).

[0039] The total number of on / off operations within a preset time window is divided by the length of the time window to obtain the current operation frequency. In one embodiment, a time window length (e.g., 60 seconds, 300 seconds, etc.) is set in the system for counting the number of operations. The total number of on / off actions is counted within the time window. The current operation frequency is obtained by dividing the total number of operations counted by the time window length. This frequency can be updated in real time using a sliding window to reflect the instantaneous workload.

[0040] For example, if a time window of 60 seconds is used, and 100 on / off actions are counted within this window, then the current operation frequency is approximately 100 / 60 / 1.67 times / second (Hz).

[0041] When the pull-in delay time offset is positive, a linear amplification factor is used; when the pull-in delay time offset is negative, an exponential amplification factor is used. The pull-in delay time offset is multiplied by the corresponding amplification factor and then multiplied by the current operating frequency to obtain the mechanical damage component of a single operation.

[0042] In one embodiment, the amplification factor is selected according to the sign of the offset—when the offset is positive (slower than the standard), a linear amplification factor is used; when the offset is negative (faster than the standard), an exponential amplification factor is used. The linear amplification factor can be calculated as "1 plus the product of the offset and a preset proportional coefficient" (i.e., coefficient = 1 + offset × preset proportional coefficient), and the exponential amplification factor can be calculated as "the absolute value of the offset as a natural constant multiplied by a preset exponential coefficient raised to the power of" (i.e., coefficient = ...). offset Preset exponent coefficient Then, the pull-in delay time offset is multiplied by the corresponding amplification factor, and then multiplied by the current operating frequency to obtain the mechanical damage component of a single operation.

[0043] For example, suppose the preset proportional coefficient is 50 (unit: 1 / second), the preset exponential coefficient is 50 (unit: 1 / second), and the current operating frequency is 1.67Hz: If the offset is +0.002 seconds, the linear amplification factor is 1 + 0.002 × 50 = 1.1, then the mechanical damage component is 0.002 × 1.1 × 1.67 ≈ 0.00367 (relative quantity); if the offset is -0.001 seconds, the exponential amplification factor is e^(0.001 × 50) ≈ e^0.05 ≈ 1.0513, then the mechanical damage component is (-0.001) × 1.0513 × 1.67 ≈ -0.00175 (relative quantity).

[0044] In another embodiment, to improve the robustness and applicability of the above calculation, preprocessing and anomaly handling methods for offset and frequency are also included: moving average or median filtering can be used for continuously measured pull-in delay time offset to suppress instantaneous pulse interference; the calculation of operating frequency can be combined with threshold judgment (for example, when the frequency is lower than a certain extremely low threshold, the lowest frequency value is used to avoid division by zero or numerical instability); upper and lower limit constraints can be set for the amplification factor calculation results to avoid unreasonable impact of extreme outliers on cumulative damage.

[0045] For example, if the calculated linear amplification factor exceeds 3.0, it can be truncated to 3.0 to prevent over-amplification caused by a single abnormal delay.

[0046] Furthermore, the use of a linear amplification factor when the pull-in delay time offset is positive and an exponential amplification factor when the pull-in delay time offset is negative includes: When the pull-in delay time offset is positive, a linear amplification factor of 1 is used, plus the product of the offset and the preset scaling factor. In one embodiment, if the currently measured pull-in delay time offset is confirmed to be positive, it indicates that the DC contactor's pull-in action is slower than the standard pull-in time, and the mechanical condition may exhibit slight wear or degradation. In this case, the system follows the formula... Calculate the linear amplification factor, where This indicates the pull-in delay time offset. This represents a preset scaling factor used to adjust the amplification of damage caused by the offset. This design ensures that a larger offset results in a higher amplification factor, making the device more sensitive to abnormally increased engagement time.

[0047] For example, if the current offset is 2ms, the scaling factor is... If the linear amplification factor is 0.1, then the linear amplification factor is 1 + 2 × 0.1 = 1.2. Substitute this factor into the subsequent mechanical damage component calculation to truly reflect the accelerated wear trend of the equipment as the operating frequency increases.

[0048] When the pull-in delay time offset is negative, the absolute value of the offset is multiplied by the preset exponential coefficient to the power of the natural constant using the exponential amplification factor.

[0049] In one embodiment, a negative engagement delay time offset is detected, meaning the current engagement action is faster than the standard engagement time. This situation may typically be caused by problems such as increased spring reaction force, excessive magnetization of the iron core, abnormal lubrication of the mechanism, or increased impact. To avoid ignoring such risks, the system exponentially amplifies the offset. The system follows... Calculate the exponential amplification factor, where It is a natural constant. It is the absolute value of the pull-in delay time offset. This is a preset exponential coefficient used to control the amplification rate.

[0050] For example, if the current offset is -1ms and the exponential coefficient is... If we set it to 0.5, then the magnification factor is... This can significantly enhance the effect of abnormally increased adsorption speed, enabling subsequent damage models to accurately identify potential impact failures.

[0051] Furthermore, in step S3, determining the coupling amplification factor through the numerical relationship of the three damage components includes: When both thermal damage and electrical damage components exceed their respective historical average values, it is identified as a thermo-electric synergistic damage state. In this embodiment, the controller compares the current thermal damage component with the historical average thermal damage, and simultaneously compares the current electrical damage component with the historical average electrical damage. When both current damage components exceed their corresponding long-term average levels, it is identified as a thermo-electrical synergistic damage state. This judgment logic indicates that significant anomalies have occurred simultaneously in both thermal and electrical stresses during the current operating cycle. The system uses this method to capture the synergistic aggravation phenomenon of equipment under combined pressures such as high temperature and current fluctuations.

[0052] For example, if the historical average thermal damage is 0.4 and the historical average electrical damage is 0.5, and the current period shows thermal damage of 0.7 and electrical damage of 0.8, both significantly higher than the average, then the system marks this period as a "thermoelectric synergistic damage state".

[0053] Calculate the product of the mechanical damage component and the thermal damage component. When the product exceeds a preset synergistic threshold, it is determined to be a mechanical-thermal synergistic damage state. In another embodiment, the mechanical damage component and the thermal damage component of the current cycle are obtained, and then their product is directly calculated as a coordination index. This product is then compared with a preset coordination threshold. When the index value is greater than the coordination threshold, the system determines that the current cycle is in a state of combined mechanical and thermal damage. This product-based approach achieves coupled identification of phenomena such as accumulated mechanical wear and temperature rise leading to lubrication degradation and increased friction, enabling the model to capture the rapid damage growth that may occur under the combined effects of mechanical and thermal factors.

[0054] For example, if the mechanical damage component is 0.6 and the thermal damage component is 0.7, their product is 0.42. If the preset collaborative threshold is 0.4, the system determines that a mechanical-thermal collaborative damage state has occurred.

[0055] When no synergistic damage state is detected, the coupling amplification factor is set to the first value; when only thermoelectric synergistic damage state is detected, the coupling amplification factor is set to the second value; when only mechanical-thermal synergistic damage state is detected, the coupling amplification factor is set to the third value; and when both synergistic damage states are detected simultaneously, the coupling amplification factor is set to the fourth value.

[0056] In another embodiment, the controller first confirms the determination results of the above two types of cooperative states, and then selects the corresponding coupling amplification coefficient according to a preset strategy.

[0057] If no collaborative damage is detected, it indicates that the current operating conditions of the equipment are relatively stable, and the system will set the coupling amplification factor to the first value (e.g., 1.0).

[0058] If only thermoelectric synergistic damage is detected, the system sets the coupling amplification factor to a second value (e.g., 1.2) to moderately increase the damage weight caused by thermoelectric synergy.

[0059] If only mechanical-thermal combined damage is detected, the system will set the coupling amplification factor to the third value (e.g., 1.3) to reflect the stronger accelerated damage effect caused by the superposition of mechanical and thermal factors.

[0060] When both cooperative states are detected, the system sets the coupling amplification factor to the fourth value (e.g., 1.5) to enable the integrated damage model to more accurately respond to the severe losses caused by the superposition of multi-source stresses.

[0061] For example, if the thermal damage in the current cycle significantly exceeds the average value, the electrical damage also exceeds the average value, and the product of mechanical damage and thermal damage also exceeds the synergistic threshold, then the system determines that both types of synergistic damage exist, and therefore sets the coupling amplification factor to the fourth value of 1.5.

[0062] Of particular importance is the establishment of a window adaptive adjustment mechanism for continuously triggered thermoelectric synergistic damage states: Record the operation sequence number of each trigger of thermoelectric synergistic damage state in real time and count the number of consecutive triggers; When the number of consecutive triggers reaches five, the window length adjustment is initiated, and the historical data sliding window is reduced to two-thirds of the original value. Based on the reduced window, the historical average values ​​of the thermal damage component and the electrical damage component are recalculated. The updated historical average values ​​are used to continue to determine the thermoelectric synergistic damage status, thereby enabling sensitive identification of the accelerated degradation trend of the equipment.

[0063] Furthermore, the condition of thermoelectric synergistic damage when both the thermal damage component and the electrical damage component exceed their respective historical average values ​​includes: Establish a sliding window for historical data of thermal damage components and electrical damage components, wherein the historical data sliding window is set to a preset multiple of the most recent consecutive operation count; In this embodiment, the controller sets the length of the historical data sliding window to a preset multiple of the number of most recent consecutive operations, such as twice the number of the most recent 20 operations, meaning the window covers the thermal and electrical damage data of the most recent 40 operations. After each new operation is completed, the controller adds the latest thermal and electrical damage components to the sliding window while removing the oldest data, thus achieving dynamic data updates and rolling storage.

[0064] For example, if the sliding window length is set to 40 operations, and 41 operations have been completed so far, the system will remove the data from the first operation from the window and only retain the data from the second to the 41st operation for subsequent average calculations.

[0065] The arithmetic mean of the thermal damage component and the electrical damage component within the sliding window of historical data are calculated separately as their respective historical averages. In one embodiment, the historical average value of thermal damage is obtained by summing all thermal damage components within the sliding window and dividing by the window length. Similarly, the historical average value of electrical damage is obtained by summing all electrical damage components and dividing by the window length. This average value reflects the typical levels of thermal and electrical stress during the recent operating cycle of the equipment and can be used as a benchmark for determining abnormal conditions.

[0066] For example, if the sum of the thermal damage components of the most recent 40 operations within the sliding window is 18, then the historical average thermal damage is 18 / 40 = 0.45; similarly, if the sum of the electrical damage components is 20, then the historical average electrical damage is 20 / 40 = 0.5.

[0067] When the thermal damage component of a single operation exceeds its historical average and the electrical damage component of a single operation also exceeds its historical average, the current operation is determined to have triggered a thermo-electric synergistic damage state.

[0068] In one embodiment, the controller extracts thermal damage components and electrical damage components for each operation and compares them one by one with the historical average values. When the thermal damage component is greater than the historical average value of thermal damage and the electrical damage component is greater than the historical average value of electrical damage, the operation is identified as being in a state of thermo-electrical combined damage.

[0069] For example, if the current operation has a thermal damage component of 0.6 and an electrical damage component of 0.7, while the historical averages are 0.45 and 0.5 respectively, the system determines that the current operation triggers a thermo-electric synergistic damage state and records the state for subsequent calculation of the coupling amplification factor.

[0070] Furthermore, the equivalent damage value of the cumulative continuous operations in step S4, as a cumulative damage indicator, includes: Calculate the ratio of the average equivalent damage value of the most recent ten operations to the average equivalent damage value of the previous ten operations. When the ratio is greater than 1.3, activate the accelerated accumulation mode. In one embodiment, the controller acquires the equivalent damage values ​​of the previous 10 operations and the equivalent damage values ​​of the 10 earlier operations, calculates the average of the two sets, and then calculates the ratio. When the ratio is greater than a preset threshold of 1.3, it indicates that the recent damage level is significantly higher than the previous trend. The system determines that the equipment may be under abnormal stress or high load, and thus activates the accelerated accumulation mode.

[0071] For example, assuming the average equivalent damage of the first ten operations is 0.4 and the average equivalent damage of the most recent ten operations is 0.55, the ratio is 0.55 / 0.4 = 1.375, which is greater than 1.3, and the controller will switch to the accelerated accumulation mode.

[0072] In normal accumulation mode, the equivalent damage value is accumulated with equal weight. In accelerated accumulation mode, the equivalent damage value of the most recent ten operations is multiplied by a weighting factor of 1.2, and the equivalent damage value of previous operations is multiplied by a weighting factor of 0.9. In one embodiment, in normal accumulation mode, the controller uses equal weighting to accumulate the equivalent damage value of each operation, that is, the equivalent damage value of each operation is directly added to the cumulative damage index; while in accelerated accumulation mode, in order to emphasize the impact of recent high-damage operations, the equivalent damage value of the most recent ten operations is multiplied by a weighting coefficient of 1.2, and the equivalent damage value of previous operations is multiplied by a weighting coefficient of 0.9, so that the cumulative damage caused by recent abnormal loads accounts for a larger proportion.

[0073] For example, if the equivalent damage values ​​of the most recent ten operations are 0.5, 0.6, 0.55, etc., multiplied by 1.2, they become 0.6, 0.72, 0.66 respectively; while the equivalent damage values ​​of the previous ten operations are 0.4, 0.45, etc., multiplied by 0.9, they become 0.36, 0.405. Then, the values ​​are accumulated in chronological order to obtain a new cumulative damage index.

[0074] The weighted equivalent damage values ​​are accumulated in chronological order to obtain the cumulative damage index at the current moment.

[0075] In one embodiment, the controller accumulates the equivalent damage value of each weighted operation in the order in which the operations occur, forming a continuous cumulative damage index sequence. This index can reflect the current cumulative wear level of the equipment in real time and serve as the basis for life prediction and maintenance decisions.

[0076] For example, assuming the weighted equivalent damage values ​​for the first three operations are 0.36, 0.405, and 0.6 respectively, the cumulative damage indices are 0.36, 0.765 (0.36+0.405), and 1.365 (0.765+0.6) respectively, and so on, until the latest operation.

[0077] Furthermore, step S4 involves calculating the ratio between the real-time cumulative damage index and the pre-acquired damage threshold, including: Accelerated aging tests were conducted on at least five samples of the same model of DC contactor to obtain cumulative damage data for failure, and the arithmetic mean and standard deviation were calculated. In one embodiment, at least five DC contactor samples of the same model are selected and subjected to accelerated aging. The cumulative damage value of each sample when it reaches a failure state is recorded. Subsequently, the controller or data processing module performs statistical analysis on the cumulative damage data of all samples, calculates the arithmetic mean as a representative of the overall failure level, and calculates the standard deviation to reflect the differences between samples.

[0078] For example, if the cumulative damage values ​​of the five samples are 2.1, 2.3, 2.0, 2.4 and 2.2 respectively, then the arithmetic mean is (2.1+2.3+2.0+2.4+2.2) / 5=2.2, and the standard deviation is approximately 0.15.

[0079] The damage threshold is calculated by subtracting 1.5 times the standard deviation from the arithmetic mean. In one embodiment, the controller sets a damage threshold by subtracting the standard deviation from the arithmetic mean and multiplying by 1.5 based on statistical results, so as to ensure that the threshold is slightly lower than the typical failure level, thereby providing an early warning of the remaining lifespan.

[0080] For example, if the arithmetic mean above is 2.2 and the standard deviation is 0.15, then the damage threshold = 2.2. 1.5 × 0.15 = 1.975.

[0081] Divide the current cumulative damage index by the damage threshold to obtain the damage progress ratio, and take the complement of the damage progress ratio as the remaining lifespan ratio. In one embodiment, the ratio of the real-time cumulative damage index to the preset damage threshold is calculated to obtain the proportion of damage progress consumed by the current operation. Then, the ratio is subtracted from 1 to obtain the remaining lifespan ratio, which reflects the remaining operating capacity that the equipment can still withstand.

[0082] For example, if the current cumulative damage index is 0.8 and the damage threshold is 1.975, then the damage progress ratio is 0.8 / 1.975 ≈ 0.405, and the remaining lifespan ratio is 1. 0.405≈0.595.

[0083] Multiply the remaining lifespan percentage by the total number of designed operations of the contactor to obtain the expected number of remaining operations, and output the expected number of remaining operations as the predicted value of the contactor's remaining lifespan.

[0084] For example, if the contactor is designed for a total of 50,000 operations and the remaining lifespan is 0.595, then the expected remaining operations = 50,000 × 0.595 ≈ 29,750 operations.

[0085] The present invention also provides a life determination system 100 for a high-voltage DC contactor, for executing the above-described life determination method for a high-voltage DC contactor, wherein the life determination system 100 for a high-voltage DC contactor includes: The physical quantity acquisition module 101 is used to synchronously acquire the arc duration, peak current, contact temperature rise and pull-in delay time during each switching operation of the DC contactor, forming a physical quantity data set for a single operation. The damage component calculation module 102 is used to calculate the thermal damage component based on the contact temperature rise and arc duration, multiply the square of the peak current by the contact resistance measured in real time to obtain the electrical damage component, and determine the mechanical damage component based on the pull-in delay time. The equivalent damage quantification module 103 is used to calculate the weighted sum of the thermal damage component, electrical damage component and mechanical damage component, which is recorded as the basic damage value; the coupling amplification factor is determined by the numerical relationship of the three damage components, and the equivalent damage value is obtained by multiplying the basic damage value by the coupling amplification factor. The life prediction output module 104 is used to accumulate the equivalent damage value of continuous operation as the cumulative damage index. It calculates the ratio between the real-time cumulative damage index and the pre-acquired damage threshold, and outputs the predicted value of the remaining life of the contactor.

[0086] Therefore, the embodiments should be considered as exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalents of the application are intended to be included within the invention.

[0087] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A method for determining the lifespan of a high-voltage DC contactor, characterized in that, Includes the following steps: Step S1: During each switching operation of the DC contactor, the arc duration, peak current, contact temperature rise, and engagement delay time are collected synchronously to form a set of physical quantity data for a single operation. Step S2: Calculate the thermal damage component based on the contact temperature rise and arc duration, measure the contact resistance value before and after the switching action in real time, and take the difference between the resistance value after the action and the resistance value before the action as the resistance increment. Multiplying the square of the peak current by the resistance increment yields the resistive power loss, and multiplying the resistive power loss by the arc duration yields the resistive energy loss. The arc power is obtained by measuring the product of the arc voltage and the peak current, and then multiplied by the arc duration to obtain the arc energy consumption. The electrical damage component of a single operation is obtained by adding the resistive energy loss to the arc energy loss. Calculate the difference between the current pull-in delay time and the standard pull-in time of the DC contactor to obtain the pull-in delay time offset; The total number of on / off operations within a preset time window is divided by the length of the time window to obtain the current operation frequency. When the pull-in delay time offset is positive, a linear amplification factor is used; when the pull-in delay time offset is negative, an exponential amplification factor is used. The pull-in delay time offset is multiplied by the corresponding amplification factor and then multiplied by the current operating frequency to obtain the mechanical damage component of a single operation. Step S3: Calculate the weighted sum of the thermal damage component, electrical damage component, and mechanical damage component, and record it as the basic damage value; The coupling amplification factor is determined by the numerical relationship between the three damage components, and the equivalent damage value is obtained by multiplying the basic damage value by the coupling amplification factor. Step S4: The equivalent damage value of continuous operation is used as the cumulative damage index. The ratio of the real-time cumulative damage index to the pre-acquired damage threshold is calculated, and the remaining life prediction value of the contactor is output.

2. The life determination method for high-voltage DC contactors according to claim 1, characterized in that, Step S2, which calculates the thermal damage component based on the contact temperature rise and arc duration, includes: The duration of the electric arc is divided into three periods according to the characteristics of temperature rise: rapid heating stage, high temperature maintenance stage, and slow cooling stage. The average temperature rise values ​​of the rapid heating phase, the high temperature maintenance phase, and the slow cooling phase were extracted separately. The average temperature rise during the high-temperature maintenance phase is multiplied by the corresponding time length to obtain the main thermal damage contribution. The average temperature rise during the rapid heating phase and the slow cooling phase are multiplied by the corresponding time length and the preset phase weighting coefficient, respectively, and then added together to obtain the secondary thermal damage contribution. The thermal damage component for a single operation is obtained by summing the contributions of primary and secondary thermal damage.

3. The life determination method for high-voltage DC contactors according to claim 1, characterized in that, The use of a linear amplification factor when the pull-in delay time offset is positive and an exponential amplification factor when the pull-in delay time offset is negative includes: When the pull-in delay time offset is positive, a linear amplification factor of 1 is used, plus the product of the offset and the preset scaling factor. When the pull-in delay time offset is negative, the absolute value of the offset is multiplied by the preset exponential coefficient to the power of the natural constant using the exponential amplification factor.

4. The life determination method for high-voltage DC contactors according to claim 3, characterized in that, Step S3 involves determining the coupling amplification factor based on the numerical relationship between the three damage components, including: When both thermal damage and electrical damage components exceed their respective historical average values, it is identified as a thermo-electric synergistic damage state. Calculate the product of the mechanical damage component and the thermal damage component. When the product exceeds a preset synergistic threshold, it is determined to be a mechanical-thermal synergistic damage state. When no synergistic damage state is detected, the coupling amplification factor is set to the first value; when only thermoelectric synergistic damage state is detected, the coupling amplification factor is set to the second value; when only mechanical-thermal synergistic damage state is detected, the coupling amplification factor is set to the third value; and when both synergistic damage states are detected simultaneously, the coupling amplification factor is set to the fourth value.

5. The life determination method for high-voltage DC contactors according to claim 4, characterized in that, The condition where both thermal damage and electrical damage components exceed their respective historical averages is considered a thermoelectric synergistic damage state, including: Establish a sliding window for historical data of thermal damage components and electrical damage components, wherein the historical data sliding window is set to a preset multiple of the most recent consecutive operation count; The arithmetic mean of the thermal damage component and the electrical damage component within the sliding window of historical data are calculated separately as their respective historical averages. When the thermal damage component of a single operation exceeds its historical average and the electrical damage component of a single operation also exceeds its historical average, the current operation is determined to have triggered a thermo-electric synergistic damage state.

6. The life determination method for high-voltage DC contactors according to claim 5, characterized in that, The equivalent damage value of the cumulative continuous operations in step S4, used as a cumulative damage index, includes: Calculate the ratio of the average equivalent damage value of the most recent ten operations to the average equivalent damage value of the previous ten operations. When the ratio is greater than 1.3, activate the accelerated accumulation mode. In normal accumulation mode, the equivalent damage value is accumulated with equal weight. In accelerated accumulation mode, the equivalent damage value of the most recent ten operations is multiplied by a weighting factor of 1.2, and the equivalent damage value of previous operations is multiplied by a weighting factor of 0.

9. The weighted equivalent damage values ​​are accumulated in chronological order to obtain the cumulative damage index at the current moment.

7. The life determination method for high-voltage DC contactors according to claim 6, characterized in that, Step S4 involves calculating the ratio between the real-time cumulative damage index and the pre-acquired damage threshold, including: Accelerated aging tests were conducted on at least five samples of the same model of DC contactor to obtain cumulative damage data for failure, and the arithmetic mean and standard deviation were calculated. The damage threshold is calculated by subtracting 1.5 times the standard deviation from the arithmetic mean. Divide the current cumulative damage index by the damage threshold to obtain the damage progress ratio, and take the complement of the damage progress ratio as the remaining lifespan ratio. Multiply the remaining lifespan percentage by the total number of designed operations of the contactor to obtain the expected number of remaining operations, and output the expected number of remaining operations as the predicted value of the contactor's remaining lifespan.

8. A life determination system for high-voltage DC contactors, characterized in that, For performing the life determination method for a high-voltage DC contactor as described in claim 1, the life determination system for the high-voltage DC contactor includes: The physical quantity acquisition module is used to synchronously acquire the arc duration, peak current, contact temperature rise and closing delay time during each switching operation of the DC contactor, forming a set of physical quantity data for a single operation. The damage component calculation module is used to calculate the thermal damage component based on the contact temperature rise and arc duration, multiply the square of the peak current by the contact resistance measured in real time to obtain the electrical damage component, and determine the mechanical damage component based on the pull-in delay time. The equivalent damage quantification module is used to calculate the weighted sum of thermal damage components, electrical damage components, and mechanical damage components, which is recorded as the base damage value. The coupling amplification factor is determined by the numerical relationship of the three damage components, and the equivalent damage value is obtained by multiplying the base damage value by the coupling amplification factor. The life prediction output module is used to accumulate the equivalent damage value of continuous operation as the cumulative damage index. It calculates the ratio between the real-time cumulative damage index and the pre-acquired damage threshold, and outputs the predicted value of the remaining life of the contactor.

Images