Method and system for controlling bimetallic strip to disconnect circuit

Abstract

The invention provides a bimetallic strip disconnection circuit control method and system, relates to the technical field of circuit protection, and realizes accurate tripping and early warning by obtaining a bimetallic strip deformation signal, calculating a difference value and combining different threshold values and duration to judge and distinguish instantaneous large fluctuation and continuous small faults. The circuit protection circuit has the advantages that normal instantaneous fluctuation and continuous electrical faults can be effectively distinguished, false tripping is avoided, early warning is provided, and therefore the accuracy and reliability of circuit protection are improved.

Description

Technical Field

[0001] The present application relates to the field of circuit protection technology, and in particular to bimetallic strip control technology in thermal overload relays. Specifically, it relates to a bimetallic strip disconnect circuit control method and system for motor protection in multi-phase circuits. Background Art

[0002] In industrial production environments, the safe and stable operation of multiphase circuit systems, particularly those used to power large motors, is crucial. To prevent motor damage due to abnormal conditions such as overload, short circuit, or phase current imbalance, a thermal overload relay is often connected in series. The core protection element of this type of relay is often a bimetallic strip. Its operating principle is based on the thermal effect (Joule heating) generated by current flow, which causes the bimetallic strip to deform. When the deformation reaches a preset mechanical threshold, a trip mechanism is triggered, disconnecting the main circuit and thus protecting the protected equipment. However, in practical applications, traditional bimetallic strip-controlled protection devices face complex interference, resulting in malfunctions in their protection function, such as misjudgment or ignoring real faults. Specifically, existing technologies suffer from the following problems: On the one hand, external environmental factors can passively affect the bimetallic strip's operating state. For example, when the local ambient temperature of the protection device fluctuates periodically due to an external heat source (such as a nearby high-frequency induction heat treatment furnace), the bimetallic strip absorbs additional heat that is not generated by the current. On the other hand, the protected equipment itself may also generate transient but large-amplitude current imbalance signals during normal operation. More seriously, when the insulation layer of the motor windings experiences actual physical failure due to cumulative damage (such as the formation of a weak but persistent leakage path), the resulting current imbalance may be very small initially, far smaller than the transient current imbalance generated by normal operating fluctuations. Traditional bimetallic control systems, as analog devices based on total heat accumulation, are unable to distinguish the nature of the signal; they can only sense the heat but cannot identify its source.

[0003] In view of the above problems, the existing technology still needs to be improved. Summary of the Invention

[0004] In order to address the shortcomings of the existing technology, the present application provides a bimetallic strip disconnect circuit control method and system, which has the advantages of being able to effectively distinguish normal instantaneous fluctuations from continuous electrical faults, avoid false tripping, and provide early warning, thereby improving the accuracy and reliability of circuit protection.

[0005] This application provides a bimetallic strip disconnect circuit control method, the technical points of which are: A bimetallic strip disconnect circuit control method is applied to a thermal overload relay device including three-phase current, wherein each phase of current has a corresponding bimetallic strip and a sensor for sensing the deformation and displacement of the bimetallic strip. The method includes: Obtain deformation signals of multiple bimetallic strips, determine one deformation signal as a reference signal, and the rest as observation signals; Calculating the difference between each observation signal and the reference signal to obtain a first difference and a second difference; If the first difference or the second difference exceeds the first preset threshold, the control triggers the tripping and disconnecting circuit; if it is monitored that the first difference or the second difference continues to exceed the second preset threshold but is less than the first preset threshold, and the duration is greater than a preset time length, the control triggers the early warning signal.

[0006] Furthermore, the present application also proposes that a thermal overload relay device is used to protect a motor; If it is monitored that the first difference or the second difference continuously exceeds the second preset threshold but is less than the first preset threshold, and the duration is greater than a preset time length, the control triggers the early warning signal, including: judging that there is a persistent electrical fault in the motor based on the duration of the first difference or the second difference and the amplitude characteristics of the first difference or the second difference.

[0007] Furthermore, based on the duration of the first difference or the second difference and the amplitude characteristics of the first difference or the second difference, it is judged that the motor has a persistent electrical fault, including: obtaining the operating mode of the motor; the operating modes include high-load operation, light-load operation, and shutdown; determining corresponding judgment parameters according to the operating mode; the judgment parameters include a first amplitude threshold, a second amplitude threshold, and a preset duration; comparing the duration of the first difference or the second difference being monitored to continuously exceed the second preset threshold but be less than the first preset threshold with the preset duration, and comparing the amplitude characteristics of the first difference and the amplitude characteristics of the second difference with the first amplitude threshold and the second amplitude threshold, respectively, to determine that the motor has a persistent electrical fault.

[0008] Furthermore, the present application also proposes to determine corresponding judgment parameters according to the operating mode, including: Monitor the peak amplitude of the first difference, the peak amplitude of the second difference and the duration in the operating mode that does not trigger tripping; obtain the first initial threshold, the second initial threshold and the initial duration from the judgment parameters corresponding to the preset different operating modes according to the operating mode; determine the deviation of the peak amplitude of the first difference from the first initial threshold, the deviation of the peak amplitude of the second difference from the second initial threshold, and the deviation of the duration from the initial duration respectively, adjust the first initial threshold, the second initial threshold and the initial duration to obtain the adjusted first amplitude threshold, the second amplitude threshold and the preset duration.

[0009] Furthermore, the present application also proposes that the corresponding judgment parameters are determined according to the operating mode, and also includes: in response to the operating mode not being any of high-load operation, light-load operation, and shutdown, generating a first initial threshold, a second initial threshold, and an initial duration based on the peak amplitude of the monitored first difference, the peak amplitude of the second difference, and the duration; and using the first initial threshold, the second initial threshold, and the initial duration as judgment parameters.

[0010] Furthermore, the present application also proposes to adjust the first initial threshold, the second initial threshold and the initial duration to obtain the adjusted first amplitude threshold, the second amplitude threshold and the preset duration, including: obtaining the degree of deviation of the peak amplitude of the first difference from the first initial threshold and the duration of deviation, the degree of deviation of the peak amplitude of the second difference from the second initial threshold and the duration of deviation, and the degree of deviation of the duration from the initial duration and the duration of deviation; according to the degree of deviation and the duration of deviation, the preset adjustment rules are used to increase or decrease the first initial threshold, the second initial threshold and the initial duration to obtain the adjusted first amplitude threshold, the second amplitude threshold and the preset duration.

[0011] Furthermore, the present application also proposes that the preset adjustment rules include: for deviations with a small degree of deviation but a long duration, setting it to an incremental adjustment with a small step size; for deviations with a large degree of deviation and a long duration, setting it to an incremental adjustment with a large step size; and for deviations with a large amplitude but a short duration, setting it to zero adjustment or a very small adjustment.

[0012] Furthermore, in response to the operating mode not being any of high-load operation, light-load operation, and shutdown, a first initial threshold, a second initial threshold, and an initial duration are generated based on the peak amplitude of the monitored first difference, the peak amplitude of the second difference, and the duration, including: performing statistical analysis on the peak amplitude of the monitored first difference, the peak amplitude of the second difference, and the duration within a preset observation period; and determining the first initial threshold, the second initial threshold, and the initial duration based on the statistical analysis results and a preset safety margin.

[0013] Furthermore, statistical analysis is performed on the monitored peak amplitude of the first difference, the peak amplitude of the second difference and the duration, including: respectively calculating the mean and standard deviation of the peak amplitude of the first difference, the peak amplitude of the second difference and the duration.

[0014] Furthermore, the present application also proposes a bimetallic strip disconnect circuit control system, which is applied to a thermal overload relay device including three-phase current, each phase current has a corresponding bimetallic strip and a sensor for sensing the deformation and displacement of the bimetallic strip. The system includes: a deformation acquisition module, which is used to obtain the deformation signals of multiple bimetallic strips, determine one deformation signal as a reference signal, and the rest as observation signals; a difference calculation module, which is used to calculate the difference between each observation signal and the reference signal respectively to obtain a first difference and a second difference; a circuit control module, which is used to control the triggering of the tripping and disconnecting circuit if the first difference or the second difference exceeds a first preset threshold; if it is monitored that the first difference or the second difference continues to exceed the second preset threshold but is less than the first preset threshold, and the duration is greater than a preset time length, then the control triggers the early warning signal.

[0015] In summary, the bimetallic strip disconnect circuit control method and system provided in the present application obtains the bimetallic strip deformation signal and calculates the difference, combines different thresholds and duration judgments, distinguishes between instantaneous large fluctuations and continuous small faults, and achieves precise tripping and early warning. It has the advantages of being able to effectively distinguish normal instantaneous fluctuations from continuous electrical faults, avoid false tripping, and provide early warning, thereby improving the accuracy and reliability of circuit protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flow chart of the steps of the bimetallic strip disconnect circuit control method disclosed in an embodiment of the present invention; Figure 2 It is a schematic structural diagram of a bimetallic strip disconnect circuit control system disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The following describes in detail the implementation details of the technical solution of this embodiment: Traditional multiphase circuit protection devices, particularly those that rely on the thermal deformation of bimetallic strips for control, struggle to accurately distinguish between different heat sources and current imbalance signals in complex industrial environments. For example, in an automated stamping shop, the core power unit of a production line is a three-phase asynchronous motor that drives a high-precision stamping press. To ensure safe operation of the motor, a standard thermal overload relay is connected in series to its power supply circuit. The relay's core protection element consists of three independent bimetallic strips, one for each of the three phases A, B, and C.

[0018] Under normal operating conditions, the three-phase current load is balanced, and the three sets of bimetallic strips generate equal heat due to the thermal effect of the current. Their physical form remains stable, and the relay does not operate. However, if the current in any phase is abnormally high or low, resulting in an imbalance in the three-phase current, the corresponding bimetallic strips are heated unevenly, resulting in differential deformation. When this deformation accumulates to a preset mechanical threshold, a trip mechanism is activated, disconnecting the motor's main circuit, thus achieving imbalance protection.

[0019] A high-frequency induction heat treatment furnace was installed approximately two meters from the press control cabinet. It operated intermittently at a fixed cycle and radiated heat into the surrounding area, causing periodic fluctuations in the local ambient temperature in the control cabinet area. This externally introduced ambient heat was passively transferred to the bimetallic strip within the relay, causing its physical temperature to exceed the average workshop ambient temperature even when the motor was not running. Simultaneously, the press operated a combined "deep draw-fast retraction" cycle. During the "deep draw" phase, the motor experienced a brief, high load lasting approximately 1.5 seconds, resulting in a transient phase current imbalance of approximately 12%. When the heat treatment furnace was at its peak heat dissipation and the press entered the "deep draw" cycle, the combined heat caused the total heat absorbed by the bimetallic strip on one phase to exceed the set trip threshold, triggering the relay to trip and shutting down the press. However, on-site measurements showed normal motor operating parameters. After multiple unexpected shutdowns, a weak but persistent leakage path began to develop in the motor winding insulation, causing a true current imbalance of only about 3%. The bimetallic control system was unable to distinguish the nature of the signal. It responded to the larger amplitude fluctuations of normal operation but ignored the smaller but persistent true fault signal.

[0020] In this regard, the present application proposes a bimetallic strip disconnect circuit control method, which is applied to a thermal overload relay device including three-phase current, wherein each phase current has a corresponding bimetallic strip and a sensor for sensing the deformation displacement of the bimetallic strip, such as Figure 1 As shown, the method includes: S101, obtaining deformation signals of multiple bimetallic strips, determining one deformation signal as a reference signal, and the rest as observation signals; S102, respectively calculating the difference between each observation signal and the reference signal to obtain a first difference and a second difference; S103, if the first difference or the second difference exceeds the first preset threshold, the control triggers the tripping and disconnecting circuit; if it is monitored that the first difference or the second difference continues to exceed the second preset threshold but is less than the first preset threshold, and the duration is greater than a preset time length, the control triggers the early warning signal.

[0021] Among them, the bimetallic strip refers to an element composed of two metal layers with different thermal expansion coefficients. When heated, it will bend and deform due to the expansion difference of the different metal layers. Its purpose is to convert the thermal effect generated by the current into a measurable mechanical displacement; the deformation signal refers to the signal output by the sensor that characterizes the deformation displacement of the bimetallic strip. It can be a voltage signal, current signal or digital signal. Its purpose is to provide quantitative data on the current deformation state of the bimetallic strip; the reference signal refers to a signal selected from the deformation signals of multiple bimetallic strips as a reference, and the rest are observation signals. This setting is mainly to establish a relative comparison benchmark, thereby eliminating the synchronous impact of common factors such as ambient temperature fluctuations on all bimetallic strips.

[0022] The solution of the present application realizes the judgment of abnormal circuit status by monitoring and analyzing the deformation of the bimetallic strips of each phase in the thermal overload relay device. First, the system continuously obtains the deformation signals of multiple bimetallic strips corresponding to the three-phase current. Since external factors such as ambient temperature fluctuations may have a synchronous impact on all bimetallic strips, in order to eliminate this common-mode interference, the system will determine a deformation signal from these deformation signals as a reference signal, and the remaining deformation signals are designated as observation signals. This reference-observation setting enables subsequent analysis to focus on the relative differences in deformation between phases rather than absolute deformation values, thereby removing the interference of environmental factors.

[0023] For example, by connecting a miniature linear displacement sensor (such as a non-contact displacement sensor based on the Hall effect or capacitance principle), the deformation is converted into an electrical signal. This electrical signal is then fed into a microcontroller unit (such as an STM32 series microcontroller). The program logic within the microcontroller interprets the deformation signal from the C-phase bimetallic strip as a real-time reference for the current ambient temperature fluctuations within the control cabinet. Because the heat radiated from the stamping shop's heat treatment furnace affects all bimetallic strips within the relay uniformly, the deformation of the C-phase, acting as a detector for the ambient thermal reference, accurately reflects these external heat fluctuations.

[0024] The bimetallic strips for phases A and B (e.g., Bimetal-A and Bimetal-B) are also equipped with identical miniature linear displacement sensors. Their respective deformations (H_A and H_B) are converted into electrical signals and input into the same STM32 microcontroller. The microcontroller samples the digital values ​​of H_A, H_B, and H_C in real time, with a sampling period of 50 milliseconds. During each sampling period, the microcontroller performs the following calculations: ΔH_AC=H_A-H_C; ΔH_BC = H_B - H_C; these calculated results represent the "additional" deformation of phases A and B relative to the ambient thermal baseline. This differential calculation directly utilizes the uniformity of heat radiation from the heat treatment furnace, ensuring that the common deformation caused by ambient temperature fluctuations is effectively offset in the calculation.

[0025] The physical basis for the above differential deformation calculation is that when the high-frequency induction heat treatment furnace in the stamping shop reaches its peak heat dissipation, the excess heat radiated into the surrounding space is evenly transferred to all bimetallic strips in the control cabinet. Assuming the deformation caused by the ambient heat is H_env, the total deformation of the bimetallic strips in phases A, B, and C is: H_A_total=H_A_current+H_env, H_B_total=H_B_current+H_env, H_C_total=H_C_current+H_env. Since phase C is set to have no current flowing through it, H_C_current is 0, that is, H_C_total=H_env. By calculation: ;as well as This mathematical offset enables the calculated differential deformations ΔH_AC and ΔH_BC to accurately reflect the thermal deformation caused solely by the current imbalance between phases A and B, thereby completely eliminating the periodic thermal interference from the heat treatment furnace environment.

[0026] Based on this, the system calculates the deformation difference between each observed signal and the reference signal, generating a first difference (ΔH_AC) and a second difference (ΔH_BC). These differences directly quantify the degree of variation in bimetallic deformation caused by current imbalance between phases. This difference calculation enables the solution to detect changes in interphase imbalance while remaining insensitive to overall ambient temperature variations. The system then implements different protection strategies based on the magnitude and duration of these differences. If either difference, the first or the second, exceeds a pre-set threshold—typically indicating an overload, short circuit, or imbalance—the system immediately triggers the trip mechanism, disconnecting the circuit and providing rapid protection for the protected equipment. This rapid response ensures timely power interruption in the event of a sudden fault, preventing equipment damage.

[0027] Specifically, after obtaining ΔH_AC and ΔH_BC, the microcontroller compares them to a preset differential deformation threshold (for example, 80% of the deformation level caused by a 12% instantaneous phase current imbalance generated during the motor's deep drawing process). This threshold was determined before system operation by simulating the deep drawing process at standard ambient temperature, measuring the peak values ​​of ΔH_AC and ΔH_BC, and adjusting it downward accordingly. Only when either ΔH_AC or ΔH_BC exceeds this calibrated differential deformation threshold for a sustained period does the microcontroller issue a command to the trip actuator. For example, this command could be to supply a 24V DC voltage to an electromagnetic trip coil, generating sufficient magnetic force to push a mechanical trip lever, shutting off the main circuit. This reconfigured judgment criteria specifically targets the high-amplitude, short-duration, benign current imbalances generated during the deep drawing process of a stamping press, ensuring that it will not falsely trigger even when subjected to the effects of ambient heat.

[0028] Furthermore, to identify potential faults with smaller amplitudes but persist, such as the slow deterioration of motor winding insulation, the system also introduces an early warning mechanism. When the first or second difference value is detected to continuously exceed the second preset threshold but remain below the first preset threshold, and this state persists for longer than the preset duration, the system triggers a warning signal. This hierarchical judgment mechanism, particularly the comprehensive consideration of duration and amplitude characteristics, enables the solution to distinguish between transient normal operating fluctuations and progressive real faults. Early warnings provide maintenance personnel with the opportunity to intervene in advance, preventing minor faults from escalating into major accidents, thereby improving the reliability and predictive maintenance capabilities of the entire system.

[0029] In some preferred embodiments, the present application is implemented as follows. The bimetallic strip in the thermal overload relay device can adopt a common bimetallic strip structure, such as a composite of invar and brass, to ensure stable deformation characteristics. The sensor for sensing the deformation displacement of the bimetallic strip can be a laser displacement sensor. This sensor measures the bending displacement of the bimetallic strip by emitting a laser beam and receiving reflected light, converting the displacement into a digital signal output. These digital deformation signals are then fed into a microcontroller unit. The microcontroller unit first receives deformation signals from three sensors corresponding to the three-phase bimetallic strips. During the initial setup or calibration phase, the bimetallic strip deformation signal of one phase (for example, phase A) can be designated as the reference signal, while the deformation signals of phases B and C are designated as the observation signals. The microcontroller unit then calculates the difference between the phase B observation signal and the phase A reference signal in real time to obtain a first difference; simultaneously, it calculates the difference between the phase C observation signal and the phase A reference signal to obtain a second difference.

[0030] The microcontroller unit has two preset thresholds: a first preset threshold and a second preset threshold, as well as a preset duration. When the absolute value of the calculated first or second difference exceeds the first preset threshold, the microcontroller immediately outputs a high-level signal, which drives a relay coil, opening the relay contacts and thus cutting off power to the main circuit.

[0031] The microcontroller unit, on the other hand, continuously monitors the first or second difference. If the absolute value of either difference continuously exceeds the second preset threshold but does not reach the first preset threshold, the microcontroller starts an internal timer. Once the duration recorded by the timer exceeds a preset duration, the microcontroller triggers a warning output, such as lighting an LED indicator, driving a buzzer to sound an alarm, or sending a warning message to a host computer via a communication interface. This specific implementation enables the system to implement a graded response based on the magnitude and duration of the deformation difference, thereby improving the level of protection.

[0032] Furthermore, in the present application, a thermal overload relay device is used to protect a motor; if it is monitored that the first difference or the second difference continuously exceeds the second preset threshold but is less than the first preset threshold, and the duration is greater than a preset time length, the control triggers an early warning signal, including: judging that there is a persistent electrical fault in the motor based on the duration of the first difference or the second difference and the amplitude characteristics of the first difference or the second difference.

[0033] Among them, the amplitude feature refers to the quantitative representation of the strength or size of the signal within a specific time period. Specifically, it can be the peak value, root mean square value, average value or its rate of change, etc. Its purpose is to reflect the strength or severity of the signal; persistent electrical fault refers to the abnormal fluctuation of the current or voltage signal during the operation of the motor due to insulation aging, local short circuit of the winding, loose wiring or phase imbalance, and this abnormal fluctuation has a certain duration. Its purpose is to distinguish instantaneous interference or normal operation fluctuations from real potential faults.

[0034] The solution of this application utilizes a thermal overload relay device to protect motors and, based on this, refines the triggering logic for the early warning signal. Specifically, when a first or second difference value is detected to continuously exceed a second preset threshold value but be less than the first preset threshold value, and for a duration greater than a preset time, the early warning is triggered, no longer relying solely on the duration and threshold range. Instead, the system further considers the amplitude characteristics of the first or second difference value. This means that when determining a potential anomaly, the system not only considers the persistence of the abnormal signal but also analyzes its intensity or severity. By comprehensively analyzing the duration and amplitude characteristics of the first or second difference value, the system can more accurately determine whether the motor has a persistent electrical fault. This approach effectively distinguishes deformation differences caused by normal operating fluctuations, transient interference, or external environmental factors from actual abnormal signals, which may be smaller in amplitude but persist, indicating internal insulation degradation or localized faults. For example, a slight leakage in the motor winding may result in a small but persistent deformation difference in the bimetallic strip. If the signal duration alone is used as the basis for judgment, it may be overlooked due to its small amplitude; if the signal amplitude alone is used, it may be confused with normal transient high load. This solution combines the two, enabling the system to identify these types of hidden, progressive faults, thereby avoiding misjudgments or omissions and improving the accuracy and reliability of motor protection. This comprehensive assessment of signal duration and amplitude characteristics enables the thermal overload relay device to detect potential motor faults earlier, buying time for preventive maintenance measures, preventing the fault from escalating, and reducing equipment damage and downtime.

[0035] In some preferred embodiments, the thermal overload relay device may be integrated with a microcontroller or a dedicated digital signal processor to execute the above-mentioned judgment logic.

[0036] The present application further proposes that the steps for determining whether a motor has a persistent electrical fault include: obtaining the operating mode of the motor; the operating modes include high-load operation, light-load operation, and shutdown; determining corresponding judgment parameters based on the operating mode; the judgment parameters include a first amplitude threshold, a second amplitude threshold, and a preset duration; comparing the duration of the first difference or the second difference being monitored to continuously exceed the second preset threshold but be less than the first preset threshold with the preset duration, and comparing the amplitude characteristics of the first difference and the amplitude characteristics of the second difference with the first amplitude threshold and the second amplitude threshold, respectively, to determine whether the motor has a persistent electrical fault.

[0037] Among them, the operating mode refers to the working state of the motor under specific working conditions, which can be specifically identified by monitoring physical quantities such as the motor's current, voltage, speed, load rate or ambient temperature. Its purpose is to reflect the inherent electrical characteristics and thermal deformation laws of the motor under different working loads and environmental conditions; the judgment parameter refers to the critical value used to evaluate whether the first difference and the second difference indicate that the motor has a persistent electrical fault. Specifically, it can be obtained through pre-calibration, historical data analysis or adaptive learning. Its purpose is to dynamically adjust the sensitivity and accuracy of fault judgment according to the motor's operating mode.

[0038] The solution of this application addresses the issue of accurate motor electrical fault diagnosis under different operating modes by incorporating awareness of the motor's operating mode and dynamically adjusting fault diagnosis parameters accordingly. Specifically, the system first determines the motor's operating mode, such as high-load operation, light-load operation, or shutdown. This is because the motor's internal electrical parameters and the deformation characteristics of the bimetallic strip under the influence of the external environment vary significantly under different operating modes. For example, under high load, even normal current fluctuations can cause large bimetallic deformation differences; while in the shutdown state, any minor deformation difference may indicate an abnormality. Therefore, accurately identifying the current operating mode is essential for accurate fault diagnosis. Based on this acquired operating mode, the system determines a set of corresponding judgment parameters, including a first amplitude threshold, a second amplitude threshold, and a preset duration. These parameters are optimized for a specific operating mode and are designed to reflect the normal fluctuation range and duration characteristics of the bimetallic strip's deformation difference under that mode. For example, for high-load operating mode, a relatively high amplitude threshold and a long preset duration can be set to avoid misidentifying normal, transient, high current fluctuations as faults. For shutdown mode, a lower amplitude threshold and a shorter preset duration can be set to promptly detect even minor, persistent anomalies. The system then compares the duration of the monitored first or second difference with the preset duration determined for the current operating mode, and simultaneously compares the amplitude characteristics of the first and second differences with the corresponding first and second amplitude thresholds, respectively. Through this mode-adaptive comparison mechanism, the system can more accurately determine whether the motor has a persistent electrical fault. This approach avoids the potential for misjudgments or missed detections that can occur with fixed thresholds, enabling the early warning mechanism to effectively distinguish between normal operating fluctuations and true fault signals. Thus, this solution combines the prior art approach of determining the presence of a persistent electrical fault in the motor based on the duration and amplitude characteristics of the difference. By incorporating the operating mode into the system, the early warning judgment is no longer a single, static one, but rather dynamically adapts to the actual operating conditions of the motor. This dynamic adaptability improves the accuracy and reliability of early warnings, enabling the system to effectively filter out "false alarms" caused by changes in normal operating conditions or external environmental interference, while more sensitively capturing real, continuous electrical fault signals, thereby avoiding unexpected downtime due to misjudgment and ensuring that early warnings can be issued in the early stages of real faults to prevent further deterioration of the fault.

[0039] In some preferred embodiments, the present application is implemented as follows. To determine the motor's operating mode, existing sensor data in the motor control unit or programmable logic controller can be utilized. For example, by reading real-time current, voltage, speed, or load sensor data from the motor, a determination can be made based on a preset operating state model. For example, when both the motor's current and speed are above a certain value, the motor can be determined to be in high-load operating mode; when both the current and speed are below another certain value, the motor can be determined to be in light-load operating mode; and when the current is close to zero and the speed is zero, the motor can be determined to be in shutdown mode. Specifically, when determining the corresponding judgment parameters, a parameter lookup table can be pre-established in the system's storage unit. This lookup table can store pre-calibrated or empirically set first amplitude thresholds, second amplitude thresholds, and preset durations for different operating modes (e.g., high-load operation, light-load operation, and shutdown). Once the system identifies the current motor operating mode, it can retrieve the judgment parameters corresponding to the current mode from the lookup table. For example, if the current mode is identified as high-load operation, the system will load a relatively relaxed set of thresholds and durations; if it is identified as shutdown mode, a more stringent set of thresholds and durations will be loaded. The system then continuously monitors real-time data for the first and second differences. If either difference is detected to consistently exceed the second preset threshold but remain below the first preset threshold, the system begins counting and recording the amplitude characteristics of that difference. Once the duration reaches or exceeds the preset duration obtained from the lookup table, and the amplitude characteristics of the difference also meet the comparison criteria for the first and second amplitude thresholds obtained from the lookup table, the system determines that the motor has a persistent electrical fault and triggers a corresponding warning signal. For example, if the motor is in light-load operation, the system uses the judgment parameters for light-load mode for comparison. If the duration of the first difference exceeds the preset duration for light-load mode and its amplitude characteristics also exceed the amplitude threshold range for light-load mode, the system issues a warning. This approach ensures accurate fault diagnosis and avoids unnecessary warnings when the motor's normal operation fluctuates.

[0040] Furthermore, the present application proposes that the steps of determining the corresponding judgment parameters according to the operating mode include: monitoring the peak amplitude of the first difference, the peak amplitude of the second difference and the duration in the operating mode that does not trigger tripping; according to the operating mode, obtaining the first initial threshold, the second initial threshold and the initial duration from the judgment parameters corresponding to the preset different operating modes; respectively determining the deviation of the peak amplitude of the first difference from the first initial threshold, the deviation of the peak amplitude of the second difference from the second initial threshold, and the deviation of the duration from the initial duration, and adjusting the first initial threshold, the second initial threshold and the initial duration to obtain the adjusted first amplitude threshold, the second amplitude threshold and the preset duration.

[0041] Among them, the peak amplitude of the first difference, the peak amplitude of the second difference and the duration in the monitoring operation mode that has not triggered the trip refer to the maximum instantaneous amplitude reached by the system for the first difference and the second difference signal, as well as the duration of these difference signals within a specific range during the normal or quasi-normal state when the motor is in a specific operation mode and has not yet triggered the tripping action. The system collects and records in real time or periodically. This can be achieved by using a data acquisition unit, a signal processing unit or a storage unit. Its purpose is to obtain the actual electrical characteristic fluctuation data of the motor in this operation mode to provide a basic basis for subsequent parameter adjustment. In addition, the first initial threshold, the second initial threshold and the initial duration refer to a set of benchmark judgment parameters pre-set for different motor operation modes before the system is put into operation. It can be determined based on the motor's design specifications, historical operation data analysis, expert experience or simulation model. Its purpose is to provide a starting point or reference benchmark for dynamic adjustment. Furthermore, deviation refers to the difference or deviation between the peak amplitude of the first difference value, the peak amplitude of the second difference value, and the duration actually monitored and the corresponding first initial threshold value, second initial threshold value, and initial duration. It can be quantified by numerical comparison, percentage calculation, or difference calculation, and its purpose is to evaluate the degree of match between the current initial judgment parameters and the actual operating state of the motor. At the same time, adjustment refers to the correction or optimization of the first initial threshold value, the second initial threshold value, and the initial duration based on the deviation between the actual monitoring data and the initial parameters, so that they are closer to the actual operating characteristics of the motor. It can be achieved by rule-based adjustment, adaptive algorithm, or machine learning model, and its purpose is to improve the accuracy and reliability of fault judgment.

[0042] The solution of this application addresses the problem that traditional fixed parameters cannot adapt to dynamic changes in the motor's operating state by introducing a mechanism for dynamically adjusting judgment parameters. Specifically, during normal operation of the motor in a specific operating mode and without triggering a trip, the system continuously monitors the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration. These monitoring data reflect the actual electrical fluctuation characteristics of the motor in that operating mode. Simultaneously, based on the current operating mode, the system obtains a first initial threshold, a second initial threshold, and an initial duration from pre-set initial judgment parameters corresponding to different operating modes as a reference. The system then calculates the deviation of the monitored peak amplitude of the first difference from the first initial threshold, the deviation of the peak amplitude of the second difference from the second initial threshold, and the deviation of the duration from the initial duration. These deviations quantify the difference between the current initial judgment parameters and the actual operating state of the motor. Based on these deviations, the system adjusts the first initial threshold, the second initial threshold, and the initial duration to obtain the adjusted first amplitude threshold, the second amplitude threshold, and the preset duration. It is through this cyclic process of monitoring, comparison and dynamic adjustment that the parameters used to determine whether the motor has a persistent electrical fault can adapt to the actual operating conditions, aging level and environmental changes of the motor in real time. For example, when the motor operates stably for a long time in a certain operating mode, its electrical characteristics may drift slightly. By continuously monitoring and adjusting the judgment parameters, these parameters can always be kept consistent with the actual "healthy" state of the motor. When the motor enters a new operating mode or its electrical characteristics change, the adjusted parameters can more accurately reflect its current state, avoiding misjudgment or missed judgment caused by the use of unmatched fixed parameters. This dynamic adaptability makes subsequent fault judgments based on these adjusted parameters more accurate and reliable, thereby effectively avoiding the situation where the protection system malfunctions or "turns a blind eye" to real faults under complex working conditions, such as when the external heat source interference described in the background technology and the instantaneous imbalance of normal operation are superimposed.

[0043] In some preferred embodiments, the present application is implemented as follows. To dynamically adjust the judgment parameters, a data acquisition and processing unit can be configured. The unit is connected to the sensor of the thermal overload relay device and is used to acquire deformation signals of multiple bimetallic strips in real time and calculate a first difference and a second difference. The processing unit can continuously monitor the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration when the motor is in operation mode and the trip state is not triggered. For example, the processing unit can sample and record these amplitudes and durations at preset time intervals and store them in a temporary buffer. Furthermore, the system can preset a parameter database that stores first initial thresholds, second initial thresholds, and initial durations for different operating modes, such as high-load operation, light-load operation, and shutdown. When the system identifies the current motor operation mode, the processing unit can retrieve and obtain the first initial threshold, second initial threshold, and initial duration for the corresponding mode from the parameter database. The processing unit can then calculate the difference between the peak amplitude of the monitored first difference and the obtained first initial threshold, the difference between the peak amplitude of the second difference and the second initial threshold, and the difference between the monitored duration and the initial duration. These differences can be used as deviations. For example, if the monitored peak amplitude is higher than the initial threshold, the deviation is positive; if it is lower, the deviation is negative. Based on these deviations, the processing unit can use an adaptive adjustment algorithm to adjust the initial threshold. For example, an adjustment factor can be set. When the monitored peak amplitude is continuously higher than the first initial threshold to a certain extent, the first initial threshold can be increased slightly according to a preset step size; conversely, when it is continuously lower than the first initial threshold, it can be reduced slightly. A similar approach can also be used for the adjustment of duration. In this way, the adjusted first amplitude threshold, second amplitude threshold and preset duration can be obtained. These adjusted parameters can then be used in subsequent motor continuous electrical fault judgments, so that the judgment logic can better adapt to the actual operating conditions of the motor.

[0044] The present application further proposes to determine the corresponding judgment parameters according to the operating mode, and also includes: in response to the operating mode not being any of high-load operation, light-load operation, and shutdown, generating a first initial threshold, a second initial threshold, and an initial duration based on the peak amplitude of the monitored first difference, the peak amplitude of the second difference, and the duration; and using the first initial threshold, the second initial threshold, and the initial duration as judgment parameters.

[0045] Among them, generating the first initial threshold, the second initial threshold and the initial duration means calculating and determining the benchmark parameters for subsequent fault judgment based on the currently monitored electrical characteristic data through a specific algorithm or model. It can be achieved by data analysis, machine learning or rule-based deduction. Its purpose is to provide a set of dynamically generated judgment criteria that conform to the current actual operating status for non-preset operating modes, so as to ensure the accuracy of fault judgment.

[0046] The solution of this application effectively addresses the limitations of traditional fixed or preset mode-based judgment parameter adjustments under complex and variable operating conditions by introducing an adaptive processing mechanism for undefined operating modes. Specifically, when determining whether a motor has a persistent electrical fault, the system first obtains the motor's operating mode. If the operating mode falls into one of the preset modes, such as high-load operation, light-load operation, or shutdown, the system, following the logic of the previous solution, monitors the electrical characteristics of the operating mode and performs deviation analysis and adjustment based on the preset parameters to obtain the adjusted first amplitude threshold, second amplitude threshold, and preset duration as judgment parameters. However, if the system detects that the operating mode does not fall into any of the preset modes, the present solution no longer forcibly applies or adjusts the preset parameters. Instead, in response to this undefined state, a new judgment parameter generation process is immediately initiated. At this point, the system monitors the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration in real time under the current operating mode. This real-time monitoring data directly reflects the electrical characteristics under the current undefined operating condition. Based on this real-time monitoring data, the system dynamically generates a new set of first initial thresholds, second initial thresholds, and initial durations. These newly generated initial thresholds and durations are calculated based on the current actual operating data, so they can more accurately reflect the normal electrical fluctuation range under the current undefined operating mode. Subsequently, these newly generated initial thresholds and durations will be directly adopted and used as judgment parameters for subsequent fault judgment. In this way, this solution enables the thermal overload relay to intelligently identify and adapt to various complex, non-preset operating environments. It avoids misjudgments or missed judgments due to parameter mismatches under unknown working conditions, and ensures that even in operating modes that the system has not foreseen, a set of reasonable judgment criteria can be established based on actual electrical characteristics. This complements the solution that relies only on preset modes for adjustment, and together improves the robustness and accuracy of the entire bimetallic strip disconnect circuit control method under various operating modes, thereby effectively avoiding unexpected downtime and improving the ability to identify real faults.

[0047] In some preferred embodiments, when the system detects that the operating mode is not high-load operation, light-load operation, or shutdown, a self-learning or calibration process can be initiated. Specifically, the system can enter a preset observation period, such as a few minutes or hours, during which it continuously collects data on the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration. After the observation period, the collected data can be statistically analyzed. For example, the mean and standard deviation of the peak amplitude of the first difference, the mean and standard deviation of the peak amplitude of the second difference, and the mean and standard deviation of the duration can be calculated. Based on these statistical analysis results and in combination with a preset safety margin, the first initial threshold, the second initial threshold, and the initial duration can be dynamically determined. For example, the first initial threshold can be set to the mean of the peak amplitudes of the first difference plus a preset safety margin multiplier multiplied by its standard deviation; the second initial threshold can be set to the mean of the peak amplitudes of the second difference plus a preset safety margin multiplier multiplied by its standard deviation; and the initial duration can be set to the mean of the duration plus a preset safety margin multiplier multiplied by its standard deviation. Once these first and second initial thresholds, as well as the initial duration, are calculated, they can be immediately adopted by the system as judgment parameters for the currently undefined operating mode and used in subsequent fault judgment logic. In this way, the system can establish a reasonable and adaptive judgment standard for unknown operating modes based on actual operating data.

[0048] Furthermore, the present application adjusts the first initial threshold, the second initial threshold and the initial duration to obtain the adjusted first amplitude threshold, the second amplitude threshold and the preset duration, including: obtaining the degree of deviation of the peak amplitude of the first difference from the first initial threshold and the duration of deviation, the degree of deviation of the peak amplitude of the second difference from the second initial threshold and the duration of deviation, and the degree of deviation of the duration from the initial duration and the duration of deviation; according to the degree of deviation and the duration of deviation, the preset adjustment rules are used to incrementally or decrementally adjust the first initial threshold, the second initial threshold and the initial duration to obtain the adjusted first amplitude threshold, the second amplitude threshold and the preset duration.

[0049] Among them, the degree of deviation refers to the difference between the monitored peak amplitude or duration and the corresponding initial threshold or initial duration, which can be quantified by calculating the absolute difference, relative percentage difference or standardized difference. Its purpose is to quantify the deviation between the abnormal signal and the normal benchmark; the deviation duration refers to the length of time the monitored peak amplitude or duration remains in a deviation state, which can be determined by a timer, counter or timestamp record. Its purpose is to reflect the persistence of the abnormal signal; the preset adjustment rule refers to the logic or algorithm used to guide how to adjust the judgment parameters according to the degree of deviation and the duration of deviation. It can be a lookup table, a piecewise function or a model based on machine learning. Its purpose is to achieve adaptive adjustment of the judgment parameters; incremental or decremental adjustment refers to the operation of increasing or decreasing the initial threshold or initial duration. It can be adjusted through a fixed step size, a dynamic step size or a feedback-based step size. Its purpose is to make the judgment parameters more in line with the actual operating conditions.

[0050] The solution of this application optimizes the adjustment mechanism for judgment parameters by considering both the degree of deviation and the duration of the deviation. Specifically, after monitoring the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the deviation during operation, the system obtains information on the deviation between these monitored values ​​and the preset first initial threshold, second initial threshold, and initial duration. Based on this, the solution further analyzes the deviation, not only identifying the presence of a deviation but, more importantly, determining the specific degree of the deviation and the duration of the deviation. For example, for the peak amplitude of the first difference, the system calculates the deviation from the first initial threshold and records the duration of the deviation. Similarly, for the peak amplitude and duration of the second difference, the system obtains the degree of deviation and the duration of the deviation. By simultaneously capturing both the degree of deviation and the duration of the deviation, the system can obtain more comprehensive dynamic information about the bimetallic deformation anomaly. A small, long-lasting deviation may indicate a slow but persistent fault accumulation, while a significant, momentary deviation may be a brief disturbance. Based on this refined deviation information, the system applies pre-set adjustment rules. This rule is an intelligent decision-making logic that determines whether to make incremental or decremental adjustments to the first initial threshold, second initial threshold, and initial duration based on the combination of the degree of deviation and the duration of the deviation. For example, when the degree of deviation is large and the duration is long, the rule may indicate a larger incremental adjustment to increase the sensitivity of the warning; when the degree of deviation is small but the duration is short, the rule may indicate a zero adjustment or a very small adjustment to avoid false alarms. In this way, the adjustment of the judgment parameters is no longer a simple linear response, but can be adaptively and finely optimized based on the nature and persistence of the abnormal signal. This allows the adjusted first amplitude threshold, second amplitude threshold, and preset duration to more accurately reflect the actual state of the bimetallic strip deformation under the current operating conditions, thereby significantly improving the accuracy and reliability of the thermal overload relay warning and effectively avoiding false alarms or missed alarms caused by simple deviation judgments.

[0051] In some preferred embodiments, the present application is implemented as follows. Assume that a thermal overload relay device is protecting a motor in a high-load operating mode. The system will first continuously monitor the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration. At the same time, the system will obtain the first initial threshold, the second initial threshold, and the initial duration corresponding to the current high-load operating mode from the preset parameters. When a deviation is detected in the peak amplitude of the first difference, the system will calculate the specific degree of deviation of the peak amplitude from the first initial threshold. For example, if the first initial threshold is 10mV and the monitored peak amplitude is 12mV, the degree of deviation is 2mV. At the same time, the system will record how long the 2mV deviation state lasts, for example, for 5 seconds. Similar deviation degree and deviation duration are also obtained for the peak amplitude and duration of the second difference. Once these refined deviation data are obtained, the system will call the preset adjustment rule. The rule can be a lookup table stored in a microcontroller or a dedicated processing chip. For example, a lookup table might define the following: If the deviation is less than 1mV and persists for more than 30 seconds, the corresponding initial threshold is adjusted incrementally by small steps (e.g., 0.1mV); if the deviation is greater than 5mV and persists for more than 10 seconds, the corresponding initial threshold is adjusted incrementally by larger steps (e.g., 0.5mV); and if the deviation is greater than 3mV but persists for less than 2 seconds, the corresponding initial threshold is adjusted to zero. Based on these rules, the system makes corresponding incremental or decremental adjustments to the first and second initial thresholds, as well as the initial duration. For example, if the peak amplitude deviation of the monitored first difference is 2mV and persists for 5 seconds, the preset adjustment rule might dictate an incremental adjustment of 0.2mV to the first initial threshold. In this way, the system can adaptively optimize the judgment parameters based on the dynamic characteristics of the bimetallic deformation signal during actual operation, enabling the thermal overload relay to provide accurate warnings even under complex operating conditions, avoiding false or missed alarms.

[0052] Furthermore, in the present application, the preset adjustment rules include: for deviations with a small degree of deviation but a long duration, setting it to an incremental adjustment with a small step size; for deviations with a large degree of deviation and a long duration, setting it to an incremental adjustment with a large step size; and for deviations with a large amplitude but a short duration, setting it to zero adjustment or a very small adjustment.

[0053] A small but long-lasting deviation refers to a situation where the peak amplitude of the monitored first or second difference value differs slightly from the corresponding first or second initial threshold value, but this discrepancy persists for a long time. This can be achieved by dually assessing both the deviation amplitude and duration. Small-step incremental adjustment refers to a small increase in the judgment parameters (first initial threshold value, second initial threshold value, and initial duration). This can be achieved by presetting a small fixed value or calculating a small incremental value based on the deviation amplitude and duration. A large and long-lasting deviation refers to a significant difference between the peak amplitude of the monitored first or second difference value and the corresponding first or second initial threshold value, and this discrepancy persists for a long time. This can be achieved by dually assessing both the deviation amplitude and duration. Large-step incremental adjustment refers to a large increase in the judgment parameters (first initial threshold value, second initial threshold value, and initial duration). This can be achieved by presetting a large fixed value or calculating a large incremental value based on the deviation amplitude and duration. A large-amplitude, short-duration deviation refers to a situation where the peak amplitude of the monitored first or second difference differs significantly from the corresponding first or second initial threshold, but this discrepancy only lasts for a short time. This can be achieved by performing a dual assessment of both the deviation amplitude and duration. Zero adjustment or minimal adjustment refers to making no adjustment to the judgment parameters (first initial threshold, second initial threshold, and initial duration) or making only negligible, minor adjustments. This can be achieved by setting the adjustment step size to zero or a value close to zero.

[0054] The solution of this application optimizes the adjustment mechanism for judgment parameters by introducing refined preset adjustment rules. Assume that a thermal overload relay device is protecting a motor, and the system has already acquired the degree of deviation of the peak amplitudes of the first and second difference values ​​from the corresponding first and second initial thresholds, as well as the degree of deviation and duration of the deviation from the initial duration. For example, if the deviation of the peak amplitude of the first difference value from the first initial threshold is small, for example, only 2% of the initial threshold, but this deviation persists for a long time, for example, more than 5 minutes, this is identified as a small but long-lasting deviation. In this case, the system performs incremental adjustments in small steps, for example, increasing the first initial threshold by 0.5% and the initial duration by 10 seconds. This fine-tuning is intended to gradually adapt to subtle changes in the motor's operating environment or the slow development of early-stage faults. As a specific embodiment, if the deviation of the peak amplitude of the second difference value from the second initial threshold is large, for example, reaching 15% of the initial threshold, and this deviation persists for a long time, for example, more than 1 minute, this is identified as a large and long-lasting deviation. At this time, the system will perform incremental adjustments with large steps, for example, increasing the second initial threshold by 5% and the initial duration by 30 seconds. This large-scale adjustment is intended to quickly respond to serious and persistent abnormal conditions and ensure that the protection parameters can be tightened in time to deal with imminent risks. Specifically, if the peak amplitude of the first difference is monitored to deviate greatly from the first initial threshold, for example, it reaches 20% of the initial threshold, but this deviation state only lasts for a very short time, such as less than 0.5 seconds, this is identified as a deviation with a large amplitude but short duration. At this time, the system will be set to zero adjustment or very small adjustment, for example, no adjustment will be made to the first initial threshold and initial duration, or only a negligible small adjustment will be made. This can effectively avoid misjudgments and unnecessary parameter adjustments caused by transient interference or normal working fluctuations, thereby improving the system's anti-interference ability and stability.

[0055] Through the above technical solution, the present application can make refined adaptive adjustments to the judgment parameters based on different types of deviation characteristics. For slowly accumulating potential faults, the system can gradually increase sensitivity to achieve early warning; for severe persistent anomalies, the system can quickly tighten the protection parameters to ensure timely action; and for transient interference, the system can effectively suppress its impact on the judgment parameters to avoid misjudgment. This significantly improves the accuracy and reliability of the thermal overload relay device's judgment of motor abnormal conditions, thereby enhancing the equipment's protection performance, reducing unexpected downtime, and effectively preventing the masking of real faults.

[0056] Furthermore, in the present application, in response to the operating mode not being any of high-load operation, light-load operation, and shutdown, the step of generating a first initial threshold, a second initial threshold, and an initial duration based on the peak amplitude of the monitored first difference, the peak amplitude of the second difference, and the duration includes: performing a statistical analysis on the peak amplitude of the monitored first difference, the peak amplitude of the second difference, and the duration within a preset observation period; and determining the first initial threshold, the second initial threshold, and the initial duration based on the statistical analysis results and a preset safety margin.

[0057] The preset observation period refers to the time period during which the system continuously monitors and collects relevant data in an unknown operating mode. It can be a fixed period of time, such as hours, days, or weeks, or a dynamic period triggered by a specific event. Its purpose is to accumulate sufficient data samples to effectively evaluate the signal characteristics under the current operating mode. Statistical analysis refers to the mathematical processing and summarization of data such as the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration collected within the preset observation period. It can be performed by calculating statistical quantities such as the mean, median, mode, variance, standard deviation, and percentile of these data, or performing frequency distribution and trend analysis. Its purpose is to reveal the inherent regularity, fluctuation range, and typical characteristics of the data, and provide a quantitative basis for subsequent threshold setting. Among them, the preset safety margin refers to an additional buffer amount or adjustment factor when determining the initial threshold and initial duration based on the results of statistical analysis. It can be a fixed value, a percentage, or a function determined based on experience or simulation. Its purpose is to ensure that the set threshold and duration can effectively distinguish between normal fluctuations and potential faults, avoid misjudgments caused by system noise, measurement errors or occasional transient events, and thus improve the robustness and reliability of the judgment.

[0058] The solution of the present application eliminates the need for pre-set fixed parameters or manual experience when the operating mode is not high-load, light-load, or shutdown. Instead, it proactively generates judgment parameters based on the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the monitored signal. Specifically, the system performs statistical analysis on these key data within a preset observation period to determine the true characteristics and fluctuation range of the difference signal under the current unknown operating mode. For example, this analysis can reveal the typical peak amplitude and duration of normal fluctuations under this mode. Based on this, combined with a preset safety margin, the system intelligently determines the first initial threshold, the second initial threshold, and the initial duration. The safety margin is introduced to provide a buffer based on the statistical results, ensuring that the set thresholds and durations can effectively distinguish normal fluctuations from actual faults, avoiding misclassification of transient signals during normal operation as abnormalities and preventing the omission of real, ongoing faults due to excessively low thresholds or short durations. This adaptive parameter generation mechanism enables the thermal overload relay to automatically learn and adjust its judgment criteria when faced with new, unpredictable operating modes. This is in stark contrast to previous solutions, which may face the problem of missing or inapplicable parameters when the operating mode does not belong to a known type. In this way, the solution of this application can ensure that the thermal overload relay can still accurately and reliably perform fault diagnosis in any operating mode, especially those operating conditions that are not clearly classified. This significantly improves the robustness and applicability of the protection system, effectively avoids misjudgments and missed judgments, and thus ensures the safe operation of the protected equipment.

[0059] In some preferred embodiments, when the motor protected by the thermal overload relay device enters an unknown operating mode that is not a high-load operation, light-load operation, or shutdown state, the system can initiate an adaptive learning process. Specifically, the system can set a preset observation period, for example, lasting 24 hours. During this period, the system will continuously monitor and record the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of these peaks. For example, whenever a peak is detected in the difference signal, regardless of whether it triggers an early warning or trips, its amplitude and duration will be recorded. After the preset observation period ends, the system can perform statistical analysis on all collected first difference peak amplitude data, second difference peak amplitude data, and duration data. For example, the mean and standard deviation of these data sets can be calculated respectively. Subsequently, the system can determine the first initial threshold, the second initial threshold, and the initial duration based on these statistical analysis results and the preset safety margin. For example, the first initial threshold can be determined as the mean of the first difference peak amplitude plus a certain multiple of its standard deviation (e.g., the mean plus three times the standard deviation), with an additional preset safety margin added, such as a 5% increase on top of the calculated result. Similarly, the second initial threshold and initial duration can be determined using similar methods. For example, the initial duration can be determined as the mean of the duration plus a certain multiple of its standard deviation, with a time safety margin added, such as a 0.5 second increase on top of the calculated result. These parameters can fully reflect the actual signal characteristics of the current unknown operating mode and provide sufficient margin to avoid misjudgment, allowing the thermal overload relay to continue accurately performing its protection function in this new mode.

[0060] Through the above technical solution, when the equipment protected by the thermal overload relay is in an unknown operating mode, the system no longer needs to rely on fixed or manually set parameters, but can adaptively generate the first initial threshold, the second initial threshold and the initial duration based on the actual monitored signal characteristics. This parameter generation method based on statistical analysis and safety margin ensures that the determined judgment parameters can accurately reflect the normal fluctuation range under the current operating mode and effectively avoids the risk of misjudgment. Therefore, even when the operating mode changes or new working conditions arise, the thermal overload relay can still maintain the accuracy and reliability of its fault judgment, significantly improving the adaptability and robustness of the protection system, thereby effectively avoiding false tripping or missed judgment of real faults due to parameter mismatch, and ensuring the continued safe operation of the equipment.

[0061] Furthermore, the step of statistically analyzing the monitored peak amplitude of the first difference, the peak amplitude of the second difference and the duration in the present application includes: respectively calculating the mean and standard deviation of the peak amplitude of the first difference, the peak amplitude of the second difference and the duration.

[0062] Specifically, this embodiment performs statistical analysis on the peak amplitudes of the monitored first and second differences, as well as their durations. Specifically, a data acquisition module can be provided to continuously monitor and record the peak amplitudes of the first and second differences, as well as their corresponding durations, over a preset observation period, such as several hours or days of continuous operation. This raw data is transmitted to a data processing unit, which can be a microcontroller or dedicated processor. Upon receiving this data, the data processing unit executes a preset statistical algorithm. For the peak amplitude data set of the first difference, its arithmetic mean is calculated as the mean, and its standard deviation is calculated. Similarly, for the peak amplitude data set of the second difference and the duration data set, their means and standard deviations are calculated, respectively. These calculation results, namely the means and standard deviations of each parameter, are used in the subsequent process of determining initial thresholds and initial durations. For example, a baseline value can be set based on the mean, and the baseline value can be adjusted based on the standard deviation to incorporate a safety margin or accommodate data volatility.

[0063] In some embodiments, the step of statistically analyzing the peak amplitude of the monitored first difference, the peak amplitude of the second difference, and the duration further includes calculating specific percentiles for the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration, respectively. In actual industrial data, there may be a small number of transient outliers or noise, which can affect the mean and standard deviation, causing the statistical results to deviate from the true normal fluctuation characteristics. Specific percentiles can effectively eliminate the influence of these extreme outliers, capture the upper limit of most normal fluctuations, and provide a reliable boundary for threshold setting. By calculating specific percentiles of peak amplitudes, the system can obtain the data distribution boundary of peak amplitudes and eliminate the influence of transient outliers on peak amplitudes. This ensures that the statistical results capture the majority of normal fluctuations and provides a reference point for subsequent amplitude threshold determination, ensuring that the threshold generated is consistent with actual conditions. For duration data, specific percentiles can effectively eliminate transient short or abnormally long fluctuations and capture the upper limit of the duration of most normal fluctuations. By calculating specific percentiles of durations, the system can obtain the data distribution boundary of durations and eliminate the influence of transient outliers on durations. This ensures that the statistical results can capture the vast majority of normal fluctuations and provides a reference point for subsequent duration threshold determination, so that the results generated by the threshold are consistent with actual conditions.

[0064] In addition, the present application further proposes a bimetallic strip disconnect circuit control system, which is applied to a thermal overload relay device including three-phase current, wherein each phase current has a corresponding bimetallic strip and a sensor for sensing the deformation displacement of the bimetallic strip, such as Figure 2 As shown, the system includes: The deformation acquisition module 201 is used to acquire deformation signals of multiple bimetallic strips, determine one deformation signal as a reference signal, and the rest as observation signals; The difference calculation module 202 is used to calculate the difference between each observation signal and the reference signal to obtain a first difference and a second difference; The circuit control module 203 is used to control the triggering of tripping and disconnecting the circuit if the first difference or the second difference exceeds the first preset threshold; if it is monitored that the first difference or the second difference continuously exceeds the second preset threshold but is less than the first preset threshold, and the duration is greater than a preset time length, then control the triggering of an early warning signal.

[0065] The above description is merely an embodiment of the present application and is not intended to limit the scope of protection of the present application. For those skilled in the art, various modifications and variations of the present application are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A bimetallic strip disconnect circuit control method, applied to a thermal overload relay device including three-phase current, each phase of current having a corresponding bimetallic strip and a sensor for sensing the deformation and displacement of the bimetallic strip, characterized in that: The method comprises: Obtain deformation signals of multiple bimetallic strips, determine one deformation signal as a reference signal, and the rest as observation signals; Calculating the difference between each observation signal and the reference signal to obtain a first difference and a second difference; If the first difference or the second difference exceeds the first preset threshold, the control triggers the tripping and disconnecting circuit; if it is monitored that the first difference or the second difference continues to exceed the second preset threshold but is less than the first preset threshold, and the duration is greater than a preset time length, the control triggers the early warning signal.

2. A bimetallic circuit breaking control method according to claim 1, characterized in that: The thermal overload relay device is used to protect a motor; If it is monitored that the first difference or the second difference continuously exceeds the second preset threshold but is less than the first preset threshold, and the duration is greater than a preset time, then controlling to trigger an early warning signal includes: According to the duration of the first difference or the second difference and the amplitude characteristics of the first difference or the second difference, it is determined that a persistent electrical fault exists in the motor.

3. A bimetallic circuit breaking control method according to claim 2, characterized in that: Determining, based on a duration of the first difference or the second difference and an amplitude characteristic of the first difference or the second difference, whether a persistent electrical fault exists in the motor includes: Obtaining an operating mode of the motor; the operating mode includes high-load operation, light-load operation, and shutdown; Determine corresponding judgment parameters according to the operating mode; the judgment parameters include a first amplitude threshold, a second amplitude threshold, and a preset time length; The duration during which the first difference or the second difference is monitored to exceed the second preset threshold but be less than the first preset threshold is compared with the preset duration, and the amplitude characteristics of the first difference and the amplitude characteristics of the second difference are compared with the first amplitude threshold and the second amplitude threshold respectively, so as to determine whether the motor has a persistent electrical fault.

4. A bimetallic circuit breaking control method according to claim 3, characterized in that: The determining of the corresponding judgment parameter according to the operating mode includes: monitoring the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the first difference in the operating mode without triggering a trip; According to the operating mode, obtaining a first initial threshold, a second initial threshold, and an initial duration from the preset judgment parameters corresponding to different operating modes; Determine respectively the deviation of the peak amplitude of the first difference from the first initial threshold, the deviation of the peak amplitude of the second difference from the second initial threshold, and the deviation of the duration from the initial duration, and adjust the first initial threshold, the second initial threshold and the initial duration to obtain the adjusted first amplitude threshold, the second amplitude threshold and the preset duration.

5. A bimetallic circuit breaking control method according to any one of claims 3 or 4, characterized in that: The determining of the corresponding judgment parameter according to the operation mode further includes: In response to the operating mode not being any of high-load operation, light-load operation, and shutdown, generating a first initial threshold, a second initial threshold, and an initial duration according to the monitored peak amplitude of the first difference, the peak amplitude of the second difference, and the duration; The first initial threshold, the second initial threshold and the initial duration are used as judgment parameters.

6. A bimetallic circuit breaking control method according to claim 4, characterized in that: The adjusting the first initial threshold, the second initial threshold, and the initial duration to obtain the adjusted first amplitude threshold, the second amplitude threshold, and the preset duration includes: Obtaining a degree of deviation of the peak amplitude of the first difference from a first initial threshold and a duration of the deviation, a degree of deviation of the peak amplitude of the second difference from a second initial threshold and a duration of the deviation, and a degree of deviation of the duration from an initial duration and a duration of the deviation; According to the degree of deviation and the duration of the deviation, the first initial threshold, the second initial threshold and the initial duration are adjusted incrementally or decrementally using a preset adjustment rule to obtain the adjusted first amplitude threshold, the second amplitude threshold and the preset duration.

7. A bimetallic circuit breaking control method according to claim 6, characterized in that: The preset adjustment rules include: For deviations with a small degree of deviation but a long duration, it is set to an incremental adjustment with a small step size; for deviations with a large degree of deviation and a long duration, it is set to an incremental adjustment with a large step size; and for deviations with a large amplitude but a short duration, it is set to zero adjustment or very small adjustment.

8. A bimetallic circuit breaking control method according to claim 5, characterized in that: In response to the operating mode not being any of high-load operation, light-load operation, and shutdown, generating a first initial threshold, a second initial threshold, and an initial duration according to the monitored peak amplitude of the first difference, the peak amplitude of the second difference, and the duration, including: Performing statistical analysis on the peak amplitude of the monitored first difference, the peak amplitude of the monitored second difference, and the duration within a preset observation period; The first initial threshold, the second initial threshold and the initial duration are determined according to the statistical analysis results and a preset safety margin.

9. A bimetallic circuit breaking control method according to claim 8, characterized in that: The statistical analysis of the monitored peak amplitude of the first difference, the peak amplitude of the second difference and the duration includes: respectively calculating the mean and standard deviation of the peak amplitude of the first difference, the peak amplitude of the second difference and the duration.

10. A bimetallic strip disconnect circuit control system, applied to a thermal overload relay device including three-phase current, each phase of current having a corresponding bimetallic strip and a sensor for sensing the deformation and displacement of the bimetallic strip, characterized in that: The system comprises: A deformation acquisition module is used to acquire deformation signals of multiple bimetallic strips, determine one deformation signal as a reference signal, and the rest as observation signals; A difference calculation module is used to calculate the difference between each observation signal and the reference signal to obtain a first difference and a second difference; The circuit control module is used to control the triggering of tripping and disconnecting the circuit if the first difference or the second difference exceeds a first preset threshold; if it is monitored that the first difference or the second difference continuously exceeds the second preset threshold but is less than the first preset threshold, and the duration is greater than a preset time length, then control the triggering of an early warning signal.

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