A bimetallic strip disconnection circuit control method and system

Abstract

This invention provides a bimetallic strip circuit disconnection control method and system, relating to the field of circuit protection technology. By acquiring the bimetallic strip deformation signal and calculating the difference, and combining different thresholds and durations for judgment, it distinguishes between instantaneous large fluctuations and continuous small faults, achieving accurate tripping and early warning. It has the advantages of effectively distinguishing between normal instantaneous fluctuations and continuous electrical faults, avoiding false tripping, and providing early warning, thereby improving the accuracy and reliability of circuit protection.

Description

Technical Field

[0001] This 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 circuit disconnection control method and system for motor protection in multi-phase circuits. Background Technology

[0002] In industrial production environments, the safe and stable operation of multiphase circuit systems, especially power supply circuits used to drive large motors, is crucial. To prevent motor damage due to overload, short circuit, or phase current imbalance, thermal overload relays are typically connected in series. The core protective element of these relays often uses a bimetallic strip, which operates based on the thermal effect (Joule heating) generated when current flows, causing the bimetallic strip to deform. When the deformation reaches a preset mechanical threshold, it triggers the tripping mechanism, cutting off the main circuit and thus protecting the equipment. However, in practical applications, traditional bimetallic strip-controlled protection devices face complex interference, leading to deviations in their protection function, such as misjudgment or ignoring real faults. Specifically, existing technologies have the following problems: On the one hand, external environmental factors may passively affect the working state of the bimetallic strip. For example, when the local ambient temperature of the protection device fluctuates periodically due to external heat sources (such as nearby high-frequency induction heat treatment furnaces), the bimetallic strip absorbs additional heat, not generated by the current. On the other hand, the protected equipment itself may also generate instantaneous but large-amplitude current imbalance signals during normal operation. More seriously, when the insulation layer of the motor windings suffers real, physical faults due to cumulative damage (e.g., forming a weak but persistent leakage path), the resulting current imbalance may be very small initially, far less than the instantaneous current imbalance generated during normal operation fluctuations. Traditional bimetallic strip control systems, as analog devices based on total heat accumulation, cannot distinguish the nature of the signal; they can only sense heat but cannot identify its source.

[0003] To address the aforementioned issues, existing technologies still require improvement. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides a bimetallic strip circuit disconnection control method and system, which has the advantages of effectively distinguishing between normal instantaneous fluctuations and continuous electrical faults, avoiding false tripping, and providing early warning, thereby improving the accuracy and reliability of circuit protection.

[0005] This application provides a method for controlling the disconnection of a bimetallic strip circuit, the key technical points of which are:

[0006] A bimetallic strip disconnection circuit control method 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. The method includes:

[0007] Obtain deformation signals from multiple bimetallic sheets, determine one deformation signal as the reference signal, and the rest as observation signals;

[0008] Calculate the difference between each observed signal and the reference signal to obtain the first difference and the second difference;

[0009] If the first difference or the second difference exceeds the first preset threshold, the circuit will be tripped and disconnected. If the first difference or the second difference is detected to continuously exceed the second preset threshold but is less than the first preset threshold, and the duration is greater than a preset duration, an early warning signal will be triggered.

[0010] Furthermore, this application also proposes a thermal overload relay device for protecting an electric motor;

[0011] If the first difference or the second difference is detected to continuously exceed the second preset threshold but is less than the first preset threshold, and the duration is greater than a preset duration, then the control triggers an early warning signal, including: judging that the motor has a continuous electrical fault based on the duration of the first difference or the second difference and the amplitude characteristics of the first difference or the second difference.

[0012] 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 determined that the motor has a continuous electrical fault, including: acquiring the motor's operating mode; the operating mode includes high-load operation, light-load operation, and shutdown; determining the 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 during which the first difference or the second difference is continuously exceeded by the second preset threshold but less than the first preset threshold with the preset duration; and comparing the amplitude characteristics of the first difference and the second difference with the first amplitude threshold and the second amplitude threshold, respectively, to determine that the motor has a continuous electrical fault.

[0013] Furthermore, this application also proposes determining the corresponding judgment parameters based on the operating mode, including:

[0014] The system monitors the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the operation mode without triggering tripping. Based on the operation mode, it obtains the first initial threshold, the second initial threshold, and the initial duration from the preset judgment parameters corresponding to different operation modes. It then determines 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. 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.

[0015] Furthermore, this application also proposes that determining the corresponding judgment parameters according to the operating mode further includes: in response to the operating mode not belonging to any of the high load operation, light load operation, or shutdown, generating a first initial threshold, a second initial threshold, and an initial duration based on the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the monitored value; and using the first initial threshold, the second initial threshold, and the initial duration as judgment parameters.

[0016] Furthermore, this application proposes 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, including: obtaining the deviation degree and duration of the peak amplitude of the first difference from the first initial threshold, the deviation degree and duration of the peak amplitude of the second difference from the second initial threshold, and the deviation degree and duration of the duration from the initial duration; and adjusting the first initial threshold, the second initial threshold, and the initial duration incrementally or subtractively according to the deviation degree and the deviation duration using a preset adjustment rule to obtain the adjusted first amplitude threshold, the second amplitude threshold, and the preset duration.

[0017] Furthermore, this application also proposes that the preset adjustment rules include: for deviations with small magnitude but long duration, a small step increment adjustment is set; for deviations with large magnitude and long duration, a large step increment adjustment is set; and for deviations with large magnitude but short duration, a zero adjustment or a minimal adjustment is set.

[0018] Furthermore, in response to the fact that the operating mode does not belong to any of the high-load operation, light-load operation, or shutdown, a first initial threshold, a second initial threshold, and an initial duration are generated based on the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the monitored first difference. This includes: performing statistical analysis on the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the monitored second difference 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.

[0019] Furthermore, statistical analysis was performed on the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the monitored values, including: calculating the mean and standard deviation of the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the duration.

[0020] Furthermore, this application also proposes a bimetallic strip disconnect circuit control system, applied to a thermal overload relay device including three-phase current, each phase current having a corresponding bimetallic strip and a sensor for sensing the deformation displacement of the bimetallic strip. The system includes: a deformation acquisition module, 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, used to calculate the difference between each observation signal and the reference signal to obtain a first difference and a second difference; and a circuit control module, used to control and trigger the tripping circuit disconnection if the first difference or the second difference exceeds a first preset threshold; and control and trigger an early warning signal if the first difference or the second difference is continuously detected to exceed the second preset threshold but is less than the first preset threshold, and the duration is greater than a preset duration.

[0021] In summary, the bimetallic strip disconnection circuit control method and system provided in this application acquires the bimetallic strip deformation signal and calculates the difference, and combines different thresholds and durations to distinguish between instantaneous large fluctuations and continuous small faults, thereby achieving accurate tripping and early warning. It has the advantages of effectively distinguishing between normal instantaneous fluctuations and continuous electrical faults, avoiding false tripping, and providing early warning, thereby improving the accuracy and reliability of circuit protection. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the steps of the bimetallic strip disconnect circuit control method disclosed in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the bimetallic strip disconnect circuit control system disclosed in an embodiment of the present invention. Detailed Implementation

[0024] The implementation details of the technical solution in this embodiment are described in detail below:

[0025] Traditional multiphase circuit protection devices, especially those relying 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 workshop, the core power unit of a production line is a three-phase asynchronous motor that drives a high-precision stamping machine. To ensure the motor's safe operation, a standard thermal overload relay is connected in series in its power supply circuit. The relay's core protection element consists of three independent bimetallic strips, each corresponding to one of the A, B, or C phases of the current.

[0026] Under normal operating conditions, the three-phase current load is balanced, and the heat generated by the three sets of bimetallic strips due to the current heating effect is equal, maintaining their stable physical form, and the relay does not trip. When any phase current becomes abnormally high or low, causing an imbalance in the three-phase current, the corresponding bimetallic strip is heated unevenly, resulting in differential deformation. When this deformation accumulates to a preset mechanical threshold, it will trigger a tripping mechanism, cutting off the motor's main circuit, thereby achieving imbalance protection.

[0027] A new high-frequency induction heat treatment furnace was installed approximately two meters from the press control cabinet. This furnace operates intermittently at a fixed rhythm, radiating heat into the surrounding space, causing periodic fluctuations in the local ambient temperature around the control cabinet. This externally introduced ambient heat is passively transferred to the bimetallic strip within the relay, causing its physical temperature to exceed the workshop's average ambient temperature even when the motor is not running. Simultaneously, the press executes a combined "deep drawing-fast return" work cycle. During the "deep drawing" phase, the motor experiences a brief, approximately 1.5-second high load, resulting in a momentary phase current imbalance of about 12%. When the heat treatment furnace is at its peak heat dissipation stage and the press enters the "deep drawing" work cycle, the combined heat from both causes the total heat absorbed by the bimetallic strip in one phase to exceed the set tripping threshold, triggering the relay and stopping the press. However, on-site measurements show that the motor's operating parameters are normal. After several unexpected shutdowns, a weak but persistent leakage path began to appear in the insulation layer of the motor windings, resulting in a real current imbalance with an amplitude of only about 3%. At this point, the bimetallic strip control system could not distinguish the nature of the signal; it responded to the large amplitude fluctuations of normal operation, but ignored the real fault signal with a small amplitude but a persistent presence.

[0028] To address this, this application proposes a bimetallic strip disconnection circuit control method, applied to a thermal overload relay device including three-phase current, where each phase current has a corresponding bimetallic strip and a sensor for sensing the deformation and displacement of the bimetallic strip, such as... Figure 1 As shown, the method includes:

[0029] S101, acquire deformation signals of multiple bimetallic sheets, determine one deformation signal as the reference signal, and the rest as observation signals;

[0030] S102, calculate the difference between each observed signal and the reference signal to obtain the first difference and the second difference;

[0031] S103, if the first difference or the second difference exceeds the first preset threshold, the circuit is tripped and disconnected; if the first difference or the second difference is detected to continuously exceed the second preset threshold but is less than the first preset threshold, and the duration is greater than a preset duration, an early warning signal is triggered.

[0032] Among them, a bimetallic strip is a component composed of two metal layers with different coefficients of thermal expansion. When heated, it bends and deforms due to the difference in expansion between the different metal layers. Its purpose is to convert the thermal effect generated by the current into a measurable mechanical displacement. The deformation signal is the signal output by the sensor that characterizes the deformation displacement of the bimetallic strip. It can be a voltage signal, a current signal, or a digital signal. Its purpose is to provide quantitative data on the current deformation state of the bimetallic strip. The reference signal is a signal selected as a benchmark from the deformation signals of multiple bimetallic strips, and the rest are observation signals. This setting is mainly to establish a relative benchmark, thereby eliminating the synchronous influence of common factors such as environmental temperature fluctuations on all bimetallic strips.

[0033] The solution proposed in this application achieves the judgment of abnormal circuit states by monitoring and analyzing the deformation of bimetallic strips in each phase of the thermal overload relay device. First, the system continuously acquires deformation signals of multiple bimetallic strips corresponding to the three-phase current. Since external factors such as ambient temperature fluctuations may synchronously affect all bimetallic strips, to eliminate this common-mode interference, the system determines one deformation signal as a reference signal from these signals, while the remaining deformation signals are designated as observation signals. This reference-observation setup allows subsequent analysis to focus on the relative differences in deformation between phases, rather than absolute deformation values, thereby eliminating interference from environmental factors.

[0034] 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 inside the microcontroller treats this deformation signal from the C-phase bimetallic strip as a real-time reference value for the current temperature change inside the control cabinet. Since the heat radiated from the heat treatment furnace in the stamping workshop has a uniform effect on all bimetallic strips inside the relay, the C-phase, as a detector of the ambient thermal reference, accurately reflects this fluctuation in external heat.

[0035] The bimetallic strips in phases A and B (e.g., Bimetal-A and Bimetal-B components) are also equipped with the same miniature linear displacement sensors, converting their respective deformations (H_A and H_B) into electrical signals, which are then input to the STM32 microcontroller. The microcontroller acquires the digital values ​​of H_A, H_B, and H_C in real time, with a sampling cycle of 50 milliseconds. Within each sampling cycle, the microcontroller performs the following calculations:

[0036] ΔH_AC = H_A - H_C;

[0037] ΔH_BC = H_B - H_C; these calculations represent the "additional" deformation of phases A and B relative to the ambient thermal reference. This difference calculation directly utilizes the uniformity of heat radiation from the heat treatment furnace, ensuring that common deformations caused by ambient temperature fluctuations are effectively offset in the calculation.

[0038] The physical basis for the above differential deformation calculation is that when the high-frequency induction heat treatment furnace in the stamping workshop is at its peak heat dissipation, the additional heat radiated into the surrounding space will be evenly transferred to all bimetallic strips in the control cabinet. Assuming the deformation caused by ambient heat is H_env, then the total deformation of the A-phase, B-phase, and C-phase bimetallic strips will be respectively:

[0039] H_A_total=H_A_current+H_env,

[0040] H_B_total=H_B_current+H_env,

[0041] 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, meaning H_C_total = H_env. Through calculation:

[0042] ;as well as

[0043] This mathematical cancellation allows the calculated differential deformations ΔH_AC and ΔH_BC to accurately reflect the thermal deformation caused solely by the current imbalance between phase A and phase B, thus completely eliminating the periodic thermal interference from the heat treatment furnace environment.

[0044] Based on this, the system calculates the deformation difference between each observed signal and the reference signal, thus obtaining the first difference (ΔH_AC) and the second difference (ΔH_BC). These differences directly quantify the degree of bimetallic strip deformation difference caused by the current imbalance in each phase. It is precisely this difference calculation that allows the system to capture changes in phase imbalance while remaining insensitive to overall ambient temperature changes. Subsequently, the system executes different protection strategies based on the magnitude and duration of these differences. If either the first or second difference exceeds a first preset threshold, which typically indicates an overload, short circuit, or imbalance, the system immediately controls the trigger trip mechanism to disconnect the circuit, achieving rapid protection of the protected equipment. This rapid response mechanism ensures that power can be cut off promptly in the event of a sudden fault, preventing equipment damage.

[0045] In other words, after obtaining ΔH_AC and ΔH_BC, the microcontroller compares them with a preset differential deformation threshold (e.g., corresponding to 80% of the deformation level caused by the 12% instantaneous phase current imbalance generated by the motor in the "deep drawing" step). This threshold is determined before the system is put into operation by simulating the "deep drawing" step at standard ambient temperature, measuring the peak values ​​of ΔH_AC and ΔH_BC, and then appropriately lowering them. The microcontroller only sends a command to the tripping actuator when either ΔH_AC or ΔH_BC consistently exceeds this calibrated differential deformation threshold. For example, this command could be to provide a 24V DC voltage to an electromagnetic trip coil to generate sufficient magnetic force to push the mechanical trip lever and disconnect the main circuit. This reconstruction of the criterion is specifically designed for the "high amplitude, short duration" benign current imbalance generated by the "deep drawing" step of the stamping press, ensuring that it will not be falsely triggered even when ambient heat is added.

[0046] Furthermore, to identify potential faults with small but persistent amplitudes, such as the slow degradation of motor winding insulation, the system incorporates an early warning mechanism. When a first or second difference is detected that consistently exceeds a second preset threshold but remains below the first preset threshold, and this state persists for more than a preset duration, the system triggers an early warning signal. This tiered judgment mechanism, particularly its comprehensive consideration of duration and amplitude characteristics, enables the solution to distinguish between transient normal operating fluctuations and gradual, genuine faults. Early warnings provide maintenance personnel with an opportunity for proactive intervention, preventing minor faults from escalating into major incidents, thereby improving the overall system reliability and predictive maintenance capabilities.

[0047] In some preferred embodiments, this 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, which measures the bending displacement of the bimetallic strip by emitting a laser beam and receiving the reflected light, and converts the displacement into a digital signal output. These digital deformation signals are then sent to a microcontroller unit. The microcontroller unit first receives deformation signals from three sensors corresponding to the three-phase bimetallic strip. During the initial setup or calibration phase, the bimetallic strip deformation signal of one phase (e.g., phase A) can be designated as a reference signal, while the deformation signals of phases B and C are used as 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.

[0048] 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 difference or the second difference exceeds the first preset threshold, the microcontroller immediately outputs a high-level signal. This signal drives a relay coil, causing the relay contacts to open and thus cutting off the main circuit power supply.

[0049] On the other hand, the microcontroller unit continuously monitors either the first or second difference. If the absolute value of either difference consistently exceeds the second preset threshold but does not reach the first preset threshold, the microcontroller starts an internal timer. Once the duration recorded by this timer exceeds a preset duration, the microcontroller triggers an alarm output, such as illuminating an LED indicator, driving a buzzer to sound an alarm, or sending an alarm message to the host computer via the communication interface. This specific implementation allows the system to provide graded responses based on the magnitude and duration of the deformation difference, thereby improving the level of protection.

[0050] Furthermore, in this application, a thermal overload relay device is used to protect a motor; if a first difference or a second difference is detected to continuously exceed a second preset threshold but is less than a first preset threshold, and the duration is greater than a preset duration, then a warning signal is triggered, including: determining that the motor has a continuous electrical fault based on the duration of the first difference or the second difference and the amplitude characteristics of the first difference or the second difference.

[0051] Among them, amplitude characteristics refer to the quantitative representation of the strength or magnitude of a signal within a specific time period. Specifically, it can be the peak value, root mean square value, average value, or rate of change of the signal, etc. Its purpose is to reflect the strength or severity of the signal. Continuous electrical faults refer to abnormal fluctuations in current or voltage signals caused by insulation aging, partial short circuits in windings, loose wiring, or phase imbalance during motor operation. These abnormal fluctuations have a certain duration and their purpose is to distinguish between transient interference or normal operating fluctuations and true potential faults.

[0052] This application's solution applies a thermal overload relay device to protect the motor, and further refines the triggering logic of the warning signal. Specifically, when a first or second difference is detected to continuously exceed a second preset threshold but be less than the first preset threshold, and the duration is greater than a preset duration, the system no longer relies solely on the duration and threshold range to trigger the warning, but further considers the amplitude characteristics of the first or second difference. This means that when judging potential anomalies, the system not only focuses on the persistence of the abnormal signal, but also deeply analyzes its intensity or severity. By comprehensively analyzing the duration and amplitude characteristics of the first or second difference, the system can more accurately determine whether the motor has a persistent electrical fault. This method can effectively distinguish deformation differences caused by normal operating fluctuations, transient interference, or external environmental factors from real abnormal signals that may have small amplitudes but persist, indicating internal insulation deterioration or local faults in the motor. For example, when a weak leakage current occurs in the motor windings, the bimetallic strip deformation difference may be small in amplitude but will persist. Judging solely by duration might lead to overlooking faults due to their small amplitude; judging solely by amplitude could result in confusion with normal instantaneous high loads. This solution combines both factors, enabling the system to identify these hidden, progressive faults, thus avoiding misjudgments or omissions and improving the accuracy and reliability of motor protection. This comprehensive assessment of signal duration and amplitude characteristics allows thermal overload relays to detect potential motor faults earlier, providing time for preventative maintenance, preventing fault escalation, and reducing equipment damage and downtime.

[0053] In some preferred embodiments, the thermal overload relay device may integrate a microcontroller or a dedicated digital signal processor to execute the above-described judgment logic.

[0054] This application further proposes a step for determining that a motor has a persistent electrical fault, including: acquiring the motor's operating mode; the operating mode includes 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 for which the first difference or the second difference continuously exceeds the second preset threshold but is less than the first preset threshold with the preset duration; and comparing the amplitude characteristics of the first difference and the second difference with the first amplitude threshold and the second amplitude threshold, respectively, to determine that the motor has a persistent electrical fault.

[0055] The operating mode refers to the working state of the motor under specific operating conditions. Specifically, it can be identified by monitoring physical quantities such as motor current, voltage, speed, load rate, or ambient temperature. Its purpose is to reflect the inherent electrical characteristics and thermal deformation law 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.

[0056] This application's solution addresses the issue of accurate motor electrical fault diagnosis under different operating modes by introducing the perception of the motor's operating mode and dynamically adjusting fault judgment parameters accordingly. Specifically, the motor's operating mode is first acquired, such as high-load operation, light-load operation, or shutdown. This is because the internal electrical parameters and bimetallic strip deformation characteristics under external environmental influences differ significantly under different operating modes. For example, under high load, even normal current fluctuations can lead to a large bimetallic strip deformation difference; while under shutdown, any small deformation difference may indicate an anomaly. Therefore, accurately identifying the current operating mode is fundamental for accurate judgment. Based on this, according to the 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 specific operating modes to reflect the normal fluctuation range and duration characteristics of the bimetallic strip deformation difference under that mode. For example, in high-load operation mode, a relatively high amplitude threshold and a long preset duration can be set to avoid misjudging normal instantaneous high current fluctuations as faults; while in shutdown mode, a lower amplitude threshold and a shorter preset duration can be set to promptly detect even minor, persistent anomalies. Subsequently, the system compares the duration of the monitored first or second difference with the preset duration determined under the current operation mode, and simultaneously compares the amplitude characteristics of the first and second differences with their 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 method avoids the misjudgment or missed judgment that may result from using fixed thresholds, enabling the early warning mechanism to effectively distinguish between normal operating fluctuations and real fault signals. Therefore, this solution, combined with the mechanism in previous technologies that judges the existence of persistent electrical faults in motors based on the duration and amplitude characteristics of the difference, introduces the consideration of the operation mode, making the early warning judgment no longer singular and static, but dynamically adaptable 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. At the same time, it can more sensitively capture real and continuous electrical fault signals, thereby avoiding unexpected downtime caused by misjudgment and ensuring that early warnings can be issued in the early stages of real faults to prevent the fault from worsening.

[0057] In some preferred embodiments, this application is implemented as follows. To obtain the motor's operating mode, existing sensor data in the motor control unit or programmable logic controller can be used. For example, data from the motor's real-time current, voltage, speed, or load sensors can be read and combined with a preset operating state model for judgment. For example, when both the motor's current and speed are higher than a certain specific value, it can be judged as a high-load operating mode; when both the current and speed are lower than another specific value, it can be judged as a light-load operating mode; when the current is close to zero and the speed is zero, it is judged as a 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 a first amplitude threshold, a second amplitude threshold, and a preset duration that are pre-calibrated or empirically set for different operating modes (such as high-load operation, light-load operation, and shutdown). When 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 set of relatively lenient thresholds and durations; if it is identified as a shutdown mode, a set of stricter thresholds and durations will be loaded. Subsequently, the system continuously monitors the real-time data of the first and second differences. When either difference is detected to continuously exceed the second preset threshold but is less than the first preset threshold, the system will start timing and record the amplitude characteristics of the difference. Once the duration reaches or exceeds the preset duration obtained from the lookup table, and the amplitude characteristics of the difference also satisfy the comparison conditions of the first and second amplitude thresholds obtained from the lookup table, the system will determine that the motor has a persistent electrical fault and trigger the corresponding warning signal. For example, if the motor is in a light-load operation mode, the system will use the judgment parameters in the light-load mode for comparison; if the duration of the first difference exceeds the preset duration in the light-load mode, and its amplitude characteristics also exceed the amplitude threshold range in the light-load mode, the system will issue a warning. This method ensures the accuracy of fault diagnosis and avoids issuing unnecessary warnings when the motor is operating normally with fluctuations.

[0058] Furthermore, this application proposes a step for determining the corresponding judgment parameters based on the operating mode, including: monitoring the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the operation mode without triggering tripping; obtaining the first initial threshold, the second initial threshold, and the initial duration from the preset judgment parameters corresponding to different operating modes according to the operating mode; 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, respectively; 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.

[0059] Among them, the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the monitoring operation mode without triggering tripping refer to the real-time or periodic acquisition and recording of the maximum instantaneous amplitude of the first and second difference signals, and the duration of these difference signals within a specific range, during the normal or quasi-normal state when the motor is in a specific operating mode and has not yet triggered tripping. This can be implemented using a data acquisition unit, signal processing unit, or storage unit, with the aim of obtaining actual electrical characteristic fluctuation data of the motor in this operating mode, providing a basis for subsequent parameter adjustments. 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 operating modes before the system is put into operation. These can be determined based on motor design specifications, historical operating data analysis, expert experience, or simulation models, with the aim of providing 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, the peak amplitude of the second difference, and the duration of the actual monitored values ​​and the corresponding first initial threshold, second initial threshold, and initial duration. This deviation can be quantified using methods such as numerical comparison, percentage calculation, or difference calculation. Its purpose is to assess the degree of matching between the current initial judgment parameters and the actual operating state of the motor. Meanwhile, adjustment refers to correcting or optimizing the first initial threshold, second initial threshold, and initial duration based on the deviation between the actual monitored data and the initial parameters, making them closer to the actual operating characteristics of the motor. This can be achieved using rule-based adjustment, adaptive algorithms, or machine learning models, with the aim of improving the accuracy and reliability of fault diagnosis.

[0060] This application's solution addresses the problem of traditional fixed parameters failing to adapt to dynamic changes in motor operating states by introducing a mechanism for dynamically adjusting judgment parameters. Specifically, during normal operation of the motor in a specific operating mode without triggering tripping, the system continuously monitors the peak amplitude of a first difference, the peak amplitude of a second difference, and its duration. This monitoring data reflects 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 as benchmarks from pre-set initial judgment parameters corresponding to different operating modes. Subsequently, the system calculates the deviations of the monitored peak amplitude of the first difference from the first initial threshold, the peak amplitude of the second difference from the second initial threshold, and the duration from the initial duration. These deviations quantify the differences 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 adjusted first amplitude thresholds, second amplitude thresholds, and preset durations. It is through this cyclical process of monitoring, comparison, and dynamic adjustment that the parameters used to determine whether a motor has a persistent electrical fault can adapt in real time to the motor's actual operating conditions, aging level, and environmental changes. For example, when a motor operates stably for a long period in a certain operating mode, its electrical characteristics may drift slightly. By continuously monitoring and adjusting the judgment parameters, these parameters can be kept consistent with the motor's actual "healthy" state. When the motor enters a new operating mode or its electrical characteristics change, the adjusted parameters can more accurately reflect its current state, avoiding misjudgments or omissions caused by using mismatched fixed parameters. This dynamic adaptability makes subsequent fault judgments based on these adjusted parameters more accurate and reliable, effectively preventing the protection system from malfunctioning or "ignoring" real faults under complex operating conditions, such as when external heat source interference and instantaneous imbalances in normal operation are superimposed as described in the background art.

[0061] In some preferred embodiments, this application is implemented as follows. To dynamically adjust the judgment parameters, a data acquisition and processing unit can be configured. This unit is connected to the sensor of the thermal overload relay device 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 of the difference in motor operating mode without triggering the tripping state. For example, the processing unit can sample and record these amplitudes and durations at preset time intervals and store them in a temporary buffer. Simultaneously, the system can preset a parameter database, which stores a first initial threshold, a second initial threshold, and an initial duration for different operating modes such as high-load operation, light-load operation, and shutdown. When the system identifies the current motor operating mode, the processing unit can retrieve and obtain the corresponding first initial threshold, second initial threshold, and initial duration from the parameter database. Subsequently, the processing unit can calculate the difference between the peak amplitude of the monitored first difference and the obtained first initial threshold, and the difference between the peak amplitude of the second difference and the second initial threshold, and calculate the difference between the monitored duration and the initial duration. These differences can be used as deviation values. For example, if the detected peak amplitude is higher than the initial threshold, the deviation is positive; if it is lower, the deviation is negative. Based on these deviation values, the processing unit can use an adaptive adjustment algorithm to adjust the initial threshold. For example, an adjustment factor can be set so that when the detected peak amplitude is consistently higher than the first initial threshold to a certain extent, the first initial threshold can be increased slightly by a preset step size; conversely, when it is consistently lower than the first initial threshold, it can be decreased slightly. A similar approach can be used to adjust the 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 judgments of continuous electrical faults in the motor, thereby enabling the judgment logic to better adapt to the actual operating conditions of the motor.

[0062] This application further proposes to determine the corresponding judgment parameters based on the operating mode, and also includes: in response to the operating mode not belonging to any of the high load operation, light load operation, or shutdown, generating a first initial threshold, a second initial threshold, and an initial duration based on the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the monitored value; and using the first initial threshold, the second initial threshold, and the initial duration as judgment parameters.

[0063] Among them, generating the first initial threshold, the second initial threshold, and the initial duration refers to calculating and determining the benchmark parameters for subsequent fault judgment based on the currently monitored electrical characteristic data through a specific algorithm or model. This can be achieved through data analysis, machine learning, or rule-based derivation. Its purpose is to provide a dynamically generated judgment standard that conforms to the current actual operating state for unpreset operating modes, so as to ensure the accuracy of fault judgment.

[0064] This application's solution effectively addresses the limitations of traditional fixed or preset-based parameter adjustments under complex and variable operating conditions by introducing an adaptive handling 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 belongs to one of the preset modes such as high-load operation, light-load operation, or shutdown, the system will follow the logic of previous solutions, monitoring the electrical characteristics of the operating mode and performing deviation analysis and adjustments based on preset parameters to obtain adjusted first amplitude thresholds, second amplitude thresholds, and preset durations as judgment parameters. However, when the system detects that the operating mode does not belong to any preset mode, this solution no longer forcibly applies or adjusts preset parameters. Instead, in response to this undefined state, it immediately initiates a completely new judgment parameter generation process. At this time, the system will monitor in real time the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the difference under the current operating mode. These real-time monitoring data directly reflect the electrical characteristics under the current undefined operating condition. Based on these real-time monitored data, the system will dynamically generate a completely new set of first initial thresholds, second initial thresholds, and initial durations. These newly generated initial thresholds and durations are calculated based on current actual operating data, thus more accurately reflecting the normal electrical fluctuation range under the current undefined operating mode. Subsequently, these newly generated initial thresholds and durations are directly adopted as judgment parameters for subsequent fault diagnosis. In this way, this scheme enables the thermal overload relay to intelligently identify and adapt to various complex, unpredictable operating environments. It avoids misjudgments or missed judgments due to parameter mismatches under unknown operating conditions, ensuring that even in unforeseen operating modes, a reasonable judgment standard can be established based on actual electrical characteristics. This complements schemes that rely solely on preset modes for adjustment, jointly improving the robustness and accuracy of the entire bimetallic strip disconnect circuit control method under various operating modes, thereby effectively avoiding unexpected shutdowns and improving the ability to identify real faults.

[0065] In some preferred embodiments, when the system detects that the operating mode does not fall under any of the categories of 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 several minutes or hours, during which data on the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration can be continuously collected. After the observation period ends, statistical analysis can be performed on these collected data. 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 respectively. Based on these statistical analysis results, and in conjunction with a preset safety margin, a first initial threshold, a second initial threshold, and an initial duration can be dynamically determined. For example, the first initial threshold can be set as the mean of the peak amplitude of the first difference plus a preset safety margin multiple multiplied by its standard deviation; the second initial threshold can be set as the mean of the peak amplitude of the second difference plus a preset safety margin multiple multiplied by its standard deviation; and the initial duration can be set as the mean of the duration plus a preset safety margin multiple multiplied by its standard deviation. Once these initial thresholds, second initial thresholds, and initial durations are calculated, they can be immediately adopted by the system as judgment parameters for the currently undefined operating mode, and used in subsequent fault diagnosis logic. In this way, the system can establish a reasonable and adaptive set of judgment criteria for unknown operating modes based on actual operating data.

[0066] Furthermore, in this application, the first initial threshold, the second initial threshold, and the initial duration are adjusted to obtain the adjusted first amplitude threshold, the second amplitude threshold, and the preset duration, including: obtaining the deviation degree and duration of the peak amplitude of the first difference from the first initial threshold, the deviation degree and duration of the peak amplitude of the second difference from the second initial threshold, and the deviation degree and duration of the duration from the initial duration; and adjusting the first initial threshold, the second initial threshold, and the initial duration incrementally or subtractively according to the deviation degree and the deviation duration using a preset adjustment rule to obtain the adjusted first amplitude threshold, the second amplitude threshold, and the preset duration.

[0067] Among them, the degree of deviation refers to the difference between the detected peak amplitude or duration and the corresponding initial threshold or initial duration. It can be quantified by calculating the absolute difference, relative percentage difference, or standardized difference. Its purpose is to quantify the deviation magnitude between the abnormal signal and the normal benchmark. The deviation duration refers to the length of time that the detected peak amplitude or duration remains in a deviated state. It can be determined by recording with a timer, counter, or timestamp. 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 deviation duration. It can be a lookup table, a piecewise function, or a machine learning-based model. Its purpose is to achieve adaptive adjustment of the judgment parameters. The incremental or decremental adjustment refers to the operation of increasing or decreasing the initial threshold or initial duration. It can be adjusted by 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.

[0068] This application optimizes the adjustment mechanism of the judgment parameters by introducing considerations of the degree and duration of deviation. Specifically, after monitoring the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the deviation under the operating mode, the system acquires the deviation information between these monitored values ​​and preset first initial thresholds, second initial thresholds, and initial durations. Based on this, the solution further analyzes in depth, not only identifying whether deviation exists, but more importantly, acquiring the specific degree of these deviations and the duration of these deviation states. For example, for the peak amplitude of the first difference, the system calculates its deviation from the first initial threshold and records how long the deviation state lasts. Similarly, for the peak amplitude and duration of the second difference, a similar acquisition of the degree and duration of deviation is performed. It is precisely because the degree and duration of deviation are acquired simultaneously that the system can obtain more comprehensive dynamic information about bimetallic strip deformation anomalies. A small deviation, if it persists for a long time, may indicate a slow but continuous accumulation of faults; while a significant deviation, if it only occurs instantaneously, may only be a brief disturbance. Based on this refined deviation information, the system adopts preset adjustment rules. This rule is an intelligent decision-making logic that determines whether to incrementally or subtractively adjust the first initial threshold, second initial threshold, and initial duration based on the combination of the degree and duration of deviation. For example, when the deviation is large and the duration is long, the rule may indicate a larger incremental adjustment to improve the sensitivity of the warning; while when the deviation is small but the duration is short, the rule may indicate zero or minimal 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 according to 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 true state of 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.

[0069] In some preferred embodiments, this application is implemented as follows. Assume a thermal overload relay device is protecting a motor operating in a high-load mode. The system first continuously monitors the peak amplitude of a first difference, the peak amplitude of a second difference, and its duration. Simultaneously, the system obtains the first initial threshold, the second initial threshold, and the initial duration corresponding to the current high-load operating mode from preset parameters. When a deviation is detected in the peak amplitude of the first difference, the system calculates the specific degree of deviation between the peak amplitude and the first initial threshold. For example, if the first initial threshold is 10mV and the detected peak amplitude is 12mV, the deviation is 2mV. The system also records how long this 2mV deviation lasts, for example, 5 seconds. A similar process of obtaining the degree and duration of deviation is performed for the peak amplitude and duration of the second difference. Once this refined deviation data is obtained, the system invokes a preset adjustment rule. This rule can be a lookup table stored in a microcontroller or dedicated processing chip. For example, the lookup table might define the following: if the deviation is less than 1mV and the duration of the deviation exceeds 30 seconds, the corresponding initial threshold is adjusted incrementally with a small step (e.g., 0.1mV); if the deviation is greater than 5mV and the duration of the deviation exceeds 10 seconds, the corresponding initial threshold is adjusted incrementally with a large step (e.g., 0.5mV); if the deviation is greater than 3mV but the duration of the deviation is 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 initial threshold, the second initial threshold, and the initial duration. For example, if the peak amplitude deviation of the first difference is detected to be 2mV and the duration is 5 seconds, the preset adjustment rule might indicate 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 strip deformation signal during actual operation, enabling the thermal overload relay to provide accurate early warnings even under complex operating conditions, avoiding false alarms or missed alarms.

[0070] Furthermore, in this application, the preset adjustment rules include: for deviations with small magnitude but long duration, a small step increment adjustment is set; for deviations with large magnitude and long duration, a large step increment adjustment is set; and for deviations with large amplitude but short duration, a zero adjustment or a minimal adjustment is set.

[0071] Among them, a small deviation but long duration refers to a situation where the peak amplitude of the detected first or second difference value is small compared to the corresponding first or second initial threshold, but this difference persists for a long time. This can be achieved by dual-judging the deviation amplitude and duration. Small-step incremental adjustment refers to a slight increase in the judgment parameters (first initial threshold, second initial threshold, and initial duration). This can be achieved by presetting a small fixed value or calculating a small increment based on the deviation amplitude and duration. A large deviation and long duration refers to a situation where the peak amplitude of the detected first or second difference value is large compared to the corresponding first or second initial threshold, and this difference persists for a long time. This can also be achieved by dual-judging the deviation amplitude and duration. Large-step incremental adjustment refers to a significant increase in the judgment parameters (first initial threshold, second initial threshold, and initial duration). This can be achieved by presetting a large fixed value or calculating a large increment based on the deviation amplitude and duration. A large-amplitude but short-duration deviation refers to a significant difference between the peak amplitude of the first or second difference and the corresponding first or second initial threshold, but this difference only lasts for a short period. This can be achieved by dual-judging the deviation amplitude and duration. Zero adjustment or minimal adjustment refers to no adjustment or only negligible adjustments to the judgment parameters (first initial threshold, second initial threshold, and initial duration). This can be achieved by setting the adjustment step size to zero or a value close to zero.

[0072] This application optimizes the adjustment mechanism of the judgment parameters by introducing refined preset adjustment rules. Assume a thermal overload relay is protecting a motor, and the system has acquired the deviations of the peak amplitudes of the first and second differences from the corresponding first and second initial thresholds, as well as the deviations and durations of these deviations from the initial duration. For example, if the peak amplitude of the first difference deviates slightly from the first initial threshold, such as only 2% of the initial threshold, but this deviation has persisted for a considerable time, such as more than 5 minutes, it is identified as a small but long-lasting deviation. In this case, the system will perform 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 aims to gradually adapt to subtle changes in the motor's operating environment or the slow development of early faults. As a specific implementation, if the peak amplitude of the second difference deviates significantly from the second initial threshold, such as reaching 15% of the initial threshold, and this deviation has also persisted for a considerable time, such as more than 1 minute, it is identified as a large and long-lasting deviation. At this point, the system will perform large incremental adjustments, for example, increasing the second initial threshold by 5% and the initial duration by 30 seconds. This large adjustment aims to respond quickly to severe, persistent anomalies, ensuring that protection parameters are tightened in a timely manner to address imminent risks. Specifically, if the peak amplitude of the first difference is detected to deviate significantly from the first initial threshold, for example, reaching 20% ​​of the initial threshold, but this deviation only lasts for a very short time, such as less than 0.5 seconds, it is identified as a large-amplitude but short-duration deviation. In this case, the system will be set to zero adjustment or minimal adjustment; for example, no adjustment will be made to the first initial threshold and initial duration, or only a negligible tiny adjustment will be made. This effectively avoids misjudgments and unnecessary parameter adjustments caused by transient interference or normal operating fluctuations, thereby improving the system's anti-interference capability and stability.

[0073] Through the above technical solution, this application can perform 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 and persistent anomalies, the system can quickly tighten 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 in judging abnormal motor conditions, thereby enhancing the equipment's protection performance, reducing unexpected downtime, and effectively preventing the masking of true faults.

[0074] Furthermore, in this application, in response to the operating mode not belonging to any of the high-load operation, light-load operation, or shutdown, the step of generating a first initial threshold, a second initial threshold, and an initial duration based on the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the monitored difference includes: performing statistical analysis on the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the monitored difference 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.

[0075] The preset observation period refers to the time period during which the system continuously monitors and collects relevant data under an unknown operating mode. This period can be a fixed length of time, such as several 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 collected within the preset observation period, such as the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration. Specifically, this can involve calculating statistical measures such as the mean, median, mode, variance, standard deviation, and percentiles 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, providing a quantitative basis for subsequent threshold setting. The preset safety margin refers to an additional buffer or adjustment factor added when determining the initial threshold and initial duration based on statistical analysis results. Specifically, 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, thereby improving the robustness and reliability of the judgment.

[0076] This application's solution, when the operating mode does not fall under any of the high-load, light-load, or shutdown categories, no longer relies on preset fixed parameters or human experience. 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. Specifically, the system performs statistical analysis on these key data within a preset observation period to obtain the true characteristics and fluctuation range of the difference signal under the current unknown operating mode. For example, 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 can intelligently determine the first initial threshold, the second initial threshold, and the initial duration. The safety margin is introduced to add a buffer based on the statistical results, ensuring that the set thresholds and durations can effectively distinguish between normal fluctuations and actual faults, avoiding misjudging transient signals during normal operation as abnormalities, and preventing the omission of real, persistent faults due to excessively low thresholds or short durations. This adaptive parameter generation mechanism allows the thermal overload relay to automatically learn and adjust its judgment criteria when facing new, unpreset operating modes. This contrasts sharply with previous solutions, which faced issues such as missing or inapplicable parameters when the operating mode was not of a known type. In this way, the proposed solution ensures that the thermal overload relay can accurately and reliably diagnose faults under any operating mode, especially those conditions that are not clearly categorized. This significantly improves the robustness and applicability of the protection system, effectively avoids misdiagnosis and missed diagnosis, and thus guarantees the safe operation of the protected equipment.

[0077] In some preferred embodiments, when the motor protected by the thermal overload relay enters an unknown operating mode that does not belong to high-load operation, light-load operation, or shutdown, the system can initiate an adaptive learning process. Specifically, the system can set a preset observation period, such as 24 hours. During this period, the system continuously monitors and records 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, its amplitude and duration are recorded regardless of whether it triggers an alarm or trip. After the preset observation period ends, the system can perform statistical analysis on all collected peak amplitude data of the first difference, peak amplitude data of the second difference, and duration data. For example, the mean and standard deviation of these datasets 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 a preset safety margin. For example, the first initial threshold can be determined as the average of the peak amplitudes of the first difference plus a certain multiple of its standard deviation (e.g., the average plus three times the standard deviation), with an additional preset safety margin value, such as adding 5% to the calculated result as a safety margin. Similarly, the second initial threshold and initial duration can be determined in a similar way. For example, the initial duration can be determined as the average duration plus a certain multiple of its standard deviation, with an additional time safety margin, such as adding 0.5 seconds to the calculated result. Parameters determined in this way can fully reflect the actual signal characteristics under the current unknown operating mode and leave sufficient margin to avoid misjudgment, thus enabling the thermal overload relay to continue to accurately perform its protection function in this new mode.

[0078] 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. Instead, it can adaptively generate a first initial threshold, a second initial threshold, and an 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 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 operating conditions occur, 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. This effectively avoids false tripping or missed faults due to parameter mismatch, ensuring the continuous safe operation of the equipment.

[0079] Furthermore, the steps of this application to statistically analyze the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the monitored difference include: calculating the mean and standard deviation of the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the monitoring, respectively.

[0080] Specifically, in this embodiment, statistical analysis is performed on the peak amplitude of the first difference, the peak amplitude of the second difference, and the duration of the detected difference. Specifically, a data acquisition module can be set up to continuously monitor and record the peak amplitude of the first difference, the peak amplitude of the second difference, and the corresponding duration data within 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 a dedicated processor. After receiving this data, the data processing unit executes a preset statistical algorithm. For the set of peak amplitude data for the first difference, its arithmetic mean is calculated as the mean, and its standard deviation is calculated. Similarly, for the set of peak amplitude data and the set of duration data for the second difference, their mean and standard deviation are also calculated respectively. These calculation results, i.e., the mean and standard deviation of each parameter, will be used in the subsequent process of determining the initial threshold and initial duration. For example, a benchmark value can be set based on the mean, and the benchmark value can be adjusted according to the magnitude of the standard deviation to incorporate a safety margin or adapt to data volatility.

[0081] In some embodiments, the step of statistically analyzing the peak amplitude of the 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, capturing the upper limit of most normal fluctuations and providing a reliable boundary for threshold setting. By calculating the specific percentile of the peak amplitude, the system can obtain the data distribution boundary of the peak amplitude, eliminating the influence of transient outliers on the peak amplitude. This ensures that the statistical results can capture most normal fluctuations and provide a reference point for subsequent amplitude threshold determination, making the threshold generation result consistent with the actual situation. For duration data, specific percentiles can effectively eliminate transiently short or abnormally long fluctuations, capturing the upper limit of the duration of most normal fluctuations. By calculating the specific percentile of the duration, the system can obtain the data distribution boundary of the duration, eliminating the influence of transient outliers on the duration. This ensures that the statistical results can capture the vast majority of normal fluctuations and provide a reference point for determining the subsequent duration threshold, so that the threshold generation results are consistent with the actual situation.

[0082] Therefore, this application further proposes a bimetallic strip disconnect circuit control system, 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 and displacement of the bimetallic strip, such as Figure 2 As shown, the system includes:

[0083] The deformation acquisition module 201 is used to acquire deformation signals of multiple bimetallic sheets, determine one deformation signal as a reference signal, and the rest as observation signals;

[0084] The difference calculation module 202 is used to calculate the difference between each observed signal and the reference signal to obtain the first difference and the second difference.

[0085] The circuit control module 203 is used to control the tripping of the circuit if the first difference or the second difference exceeds the first preset threshold; and to control the triggering of a warning signal if the first difference or the second difference is continuously exceeded by the second preset threshold but less than the first preset threshold and the duration is greater than a preset duration.

[0086] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A bimetallic strip disconnection circuit control method applied to a thermal overload relay device including three-phase currents, each phase current having a corresponding bimetallic strip and a sensor for sensing the displacement of the bimetallic strip, characterized by, The method comprises: Obtaining deformation signals of a plurality of bimetallic strips, determining a deformation signal as a reference signal, and determining the remaining deformation signals as observation signals; Calculating the difference between each observation signal and the reference signal to obtain a first difference value and a second difference value; If the first difference value or the second difference value exceeds a first preset threshold value, triggering a tripping circuit; if the first difference value or the second difference value continuously exceeds a second preset threshold value but is less than the first preset threshold value, and the duration is greater than a preset duration, triggering a warning signal.

2. The method of claim 1, wherein the method further comprises: The thermal overload relay device is used for protecting an electric motor; If the first difference value or the second difference value continuously exceeds the second preset threshold value but is less than the first preset threshold value, and the duration is greater than a preset duration, triggering a warning signal, comprising: According to the duration of the first difference value or the second difference value and the amplitude characteristics of the first difference value or the second difference value, determining that the electric motor has a persistent electrical fault.

3. The method of claim 2, wherein the step of applying a voltage to the bimetallic strip is performed by a controller. According to the duration of the first difference value or the second difference value and the amplitude characteristics of the first difference value or the second difference value, determining that the electric motor has a persistent electrical fault, comprising: Obtaining the operating mode of the electric motor; the operating mode comprises high-load operation, light-load operation, and shutdown; According to the operating mode, determining corresponding judgment parameters; the judgment parameters comprise a first amplitude threshold value, a second amplitude threshold value, and a preset duration; Comparing the duration of the first difference value or the second difference value continuously exceeding the second preset threshold value but being less than the first preset threshold value with the preset duration, and comparing the amplitude characteristics of the first difference value and the amplitude characteristics of the second difference value with the first amplitude threshold value and the second amplitude threshold value, respectively, to determine whether the electric motor has a persistent electrical fault.

4. The bimetallic strip trip circuit control method of claim 3, wherein, According to the operating mode, determining corresponding judgment parameters, comprising: Monitoring the peak amplitude of the first difference value, the peak amplitude of the second difference value, and the duration under the operating mode without triggering tripping; According to the operating mode, obtaining a first initial threshold value, a second initial threshold value, and an initial duration from the preset judgment parameters corresponding to different operating modes; Respectively determining the deviation of the peak amplitude of the first difference value from the first initial threshold value, the deviation of the peak amplitude of the second difference value from the second initial threshold value, and the deviation of the duration from the initial duration, adjusting the first initial threshold value, the second initial threshold value, and the initial duration to obtain an adjusted first amplitude threshold value, a second amplitude threshold value, and a preset duration.

5. A method of controlling a bimetallic strip disconnection circuit according to any one of claims 3 or 4, characterised in that, According to the operating mode, determining corresponding judgment parameters, further comprising: In response to the operating mode not belonging to any of high-load operation, light-load operation, and shutdown, generating a first initial threshold value, a second initial threshold value, and an initial duration according to the monitored peak amplitude of the first difference value, the peak amplitude of the second difference value, and the duration; Taking the first initial threshold value, the second initial threshold value, and the initial duration as judgment parameters.

6. The method of claim 4, wherein the step of applying a voltage to the bimetallic strip is performed by a controller. Adjusting the first initial threshold value, the second initial threshold value, and the initial duration to obtain an adjusted first amplitude threshold value, a second amplitude threshold value, and a preset duration, comprising: obtaining a deviation degree and a deviation duration of a peak amplitude of the first difference value from a first initial threshold value, a deviation degree and a deviation duration of a peak amplitude of the second difference value from a second initial threshold value, and a deviation degree and a deviation duration of the duration from an initial duration; according to the deviation degree and the deviation duration, adopting a preset adjustment rule to incrementally or decrementally adjust the first initial threshold value, the second initial threshold value and the initial duration, to obtain an adjusted first amplitude threshold value, a second amplitude threshold value and a preset duration.

7. The method of claim 6, wherein the step of applying a voltage to the bimetallic strip is performed by applying a voltage to the bimetallic strip through a resistor. the preset adjustment rule comprises: for the deviation with a small deviation degree but a long duration, an incremental adjustment with a small step is set; for the deviation with a large deviation degree and a long duration, an incremental adjustment with a large step is set; and for the deviation with a large amplitude but a short duration, zero adjustment or extremely small adjustment is set.

8. The bimetallic strip trip circuit control method of claim 5 wherein, in response to the running mode not belonging to any one of the high-load running, the light-load running and the shutdown, generating the first initial threshold value, the second initial threshold value and the initial duration according to the monitored peak amplitude of the first difference value, the peak amplitude of the second difference value and the duration, comprises: in a preset observation period, statistically analyzing the monitored peak amplitude of the first difference value, the peak amplitude of the second difference value and the duration; according to a statistical analysis result and a preset safety margin, determining the first initial threshold value, the second initial threshold value and the initial duration.

9. The method of claim 8, wherein the step of applying a voltage to the bimetallic strip is performed by a controller. the statistical analysis of the monitored peak amplitude of the first difference value, the peak amplitude of the second difference value and the duration comprises: respectively statistically analyzing a mean value and a standard deviation of the peak amplitude of the first difference value, the peak amplitude of the second difference value and the duration.

10. A bimetallic strip disconnection circuit control system applied to a thermal overload relay device including three-phase currents, each phase current having a corresponding bimetallic strip and a sensor for sensing displacement of the bimetallic strip, characterized by, the system comprises: a deformation acquisition module configured to acquire deformation signals of a plurality of bimetallic strips, determine a deformation signal as a reference signal, and determine the remaining deformation signals as observation signals; a difference calculation module configured to calculate a difference value between each observation signal and the reference signal to obtain a first difference value and a second difference value; a circuit control module configured to control triggering of a tripping disconnecting circuit if the first difference value or the second difference value exceeds a first preset threshold value, and control triggering of a warning signal if it is monitored that the first difference value or the second difference value continuously exceeds a second preset threshold value but is less than the first preset threshold value, and the duration is greater than a preset duration.

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