Motor overload protection dynamic locking method and system based on transient current fingerprint

Abstract

The present application relates to a kind of motor overload protection dynamic locking method and system based on transient current fingerprint, belong to motor overload protection technical field.The method includes: the attenuation track of three-phase current is analyzed from operating state to the change of flow interruption state, forms transient current fingerprint;Calibrate the amplitude reference of fundamental component of three-phase current, extract the sideband harmonic component corresponding to rotor broken bar and bearing fault, analyze the energy proportion of sideband harmonic component relative to the amplitude reference of fundamental component, generate mechanical deterioration representation and nonlinear thermal reduction coefficient;The reference thermal accumulation tripping threshold is nonlinearly reduced to form dynamic thermal trip boundary, and the real-time thermal potential value exceeds dynamic thermal trip boundary to trigger the break;Mechanical deterioration representation and nonlinear thermal reduction coefficient are written into nonvolatile storage area to form restart check reference after breaking, check the restart permission state of thermal potential value back-off state and mechanical deterioration representation, drive reclosing operation when meeting restart condition, otherwise maintain restart lock.

Description

Technical Field

[0001] This invention belongs to the field of motor overload protection technology, specifically relating to a dynamic interlocking method and system for motor overload protection based on fused transient current fingerprint. Background Technology

[0002] Electric motors are widely used in continuous operation scenarios such as water pumps, fans, compressors, and conveying equipment. Water pumps and similar load devices typically experience long operating times, continuous load variations, and prolonged exposure of mechanical components to friction and impact. During long-term operation, changes in the mechanical condition of an electric motor, such as rotor bar breakage and bearing wear, can alter electromagnetic losses, mechanical friction losses, and operating current characteristics, and also change the winding heat accumulation process. When a motor has already experienced mechanical degradation but continues to operate, relying solely on current amplitude or traditional heat accumulation status for overload protection is insufficient to effectively characterize the impact of these mechanical condition changes on the motor's heat accumulation process and protection thresholds.

[0003] Existing motor overload protection typically sets protection thresholds based on operating current, temperature rise, or thermal accumulation status, and disconnects the circuit when the thermal condition reaches a preset condition. This type of protection mainly protects against winding heating caused by current, and can meet basic overload protection requirements when the motor's mechanical condition is normal. However, as mechanical degradation progresses due to rotor bar breakage, bearing wear, and other factors, increased mechanical losses alter the thermal accumulation process under the same current conditions. Traditional protection methods still primarily rely on fixed thermal parameters or temperature rise status for judgment, lacking a direct correlation between mechanical degradation and thermal protection status, which can easily lead to discrepancies between protection judgments and actual operating conditions.

[0004] In motor fault diagnosis, existing technologies can perform spectral analysis on the three-phase operating current and identify mechanical faults using rotor bar breakage characteristic frequencies, bearing fault characteristic frequencies, and their sideband components. These methods typically focus on fault detection, fault classification, or status alarms, and the extracted spectral features are independent of the overload protection process. For continuously operating motors, mechanical degradation is not merely a matter of whether a fault occurs at a specific moment; the corresponding sideband energy continuously changes with the operating state. Existing protection methods lack a corresponding state-connection mechanism to establish a stable link between these continuously evolving mechanical degradation characteristics and the motor thermal accumulation protection process.

[0005] On the other hand, the transient response of the three-phase current generated during motor disconnection includes attenuation characteristics resulting from the change from the operating state to the disconnection state. This transient response is related to the motor windings, electromagnetic state, and operating state at the time of disconnection. Existing protection processes typically treat the disconnection action as the result of protection execution, and immediately proceed to shutdown or cooling after disconnection, rarely utilizing the transient current changes before and after disconnection as a reference for subsequent operating current analysis. Therefore, when the motor's operating state changes, the reference state used for operating current characteristic analysis may be offset, thus affecting the stability of mechanical degradation characteristic identification and protection judgment.

[0006] Furthermore, after a motor trips due to overload protection, existing restart control typically determines whether to release the lockout based on the current temperature, thermal index, or cooling time. When the motor already exhibits mechanical degradation such as broken rotor bars or worn bearings before tripping, simply relying on the degree of thermal recovery for restart judgment cannot fully reflect the mechanical condition established before tripping. Even if the current thermal condition recovers to an acceptable range, mechanical degradation may still cause changes in thermal accumulation characteristics after restarting. Therefore, existing motor protection technology still has shortcomings in utilizing multi-dimensional state information during operation for protection judgment, and there is still room for further optimization in the correlation processing between changes in mechanical degradation state, changes in thermal accumulation, and the continuation of the state after tripping. Summary of the Invention

[0007] To address the aforementioned problems in the existing technology, this invention provides a dynamic interlocking method and system for motor overload protection based on transient current fingerprinting. The objective of this invention can be achieved through the following technical solutions: The transient response of the three-phase current of the continuously running motor before and after the tripping action is obtained, and the decay trajectory of the three-phase current from the running state to the tripping state is analyzed to form a transient current fingerprint. Based on the transient current fingerprint, the fundamental component amplitude reference of the three-phase current is calibrated. Spectral analysis is performed on the three-phase current to extract the sideband harmonic components corresponding to rotor bar breakage and bearing faults. The energy ratio of the sideband harmonic components relative to the fundamental component amplitude reference is analyzed to generate mechanical degradation characterization quantities and nonlinear thermal loss coefficients. The reference thermal accumulation trip threshold is nonlinearly reduced based on the nonlinear thermal loss coefficient to form a dynamic thermal trip boundary. When the real-time thermal potential value exceeds the dynamic thermal trip boundary, a disconnection command is triggered. After disconnection, the mechanical degradation characterization quantity and the nonlinear thermal loss coefficient are written into the non-volatile storage area to form a restart verification benchmark. During restart, the thermal potential value fall-off state and the restart allowable state of the mechanical degradation characterization quantity are verified. If both states are satisfied, the reclosing operation is driven; otherwise, the restart lockout is maintained.

[0008] Specifically, the formation process of the transient current fingerprint includes: Determine the current state transition position corresponding to the interruption moment, and extract the three-phase current change sequence before and after the transition position; establish a three-phase transient response sequence according to the attenuation start state, change direction and current interruption stability state of each phase current, and uniformly encode the transient response sequence to form the transient current fingerprint.

[0009] Specifically, the calibration process for the fundamental component amplitude reference includes: Extract the pre-break amplitude state and transient decay amplitude state from the transient current fingerprint, analyze the response change relationship between the pre-break amplitude state and the transient decay amplitude state, and form an amplitude correction state; The amplitude correction state is applied to the fundamental component of the three-phase current during the operating cycle to correct the amplitude reference state of the fundamental component, and the corrected amplitude of the fundamental component is used as the amplitude reference of the fundamental component.

[0010] Specifically, the spectrum analysis includes: The three-phase current sampling sequence is obtained according to the operating cycle, and frequency domain analysis is performed on the three-phase current sampling sequence to locate the frequency position corresponding to the fundamental component. Using the frequency position as a reference, analyze the frequency response on both sides, perform directional retrieval according to the frequency offset position corresponding to rotor bar breakage and bearing failure, extract the corresponding sideband harmonic components, and generate the energy state and change state of the sideband harmonic components within the continuous operating cycle.

[0011] Specifically, the process of generating the mechanical degradation characterization quantity includes: Extract the sideband harmonic components corresponding to rotor bar breakage and bearing faults, and analyze the corresponding sideband energy change state according to different fault characteristics; The sideband energy change state is normalized and characterized using the fundamental component amplitude as a reference. The degree of degradation change corresponding to different fault characteristics is extracted, and the trend of the degree of degradation change is tracked along the continuous operation cycle. The degree of degradation change and its trend are jointly characterized to form the mechanical degradation characterization quantity.

[0012] Specifically, the formation process of the nonlinear thermal loss coefficient includes: Extract the synchronous change state of the mechanical degradation characterization quantity and the real-time thermal potential value within the continuous operating cycle, and establish the state correspondence between the degree of mechanical degradation and the degree of thermal potential change. The thermal loss states are divided according to the magnitude of thermal potential change during the increasing degree of mechanical deterioration. The change in loss increment between adjacent thermal loss states is identified, and a nonlinear correspondence between the degree of mechanical deterioration and the degree of thermal resistance loss is formed according to the change in loss increment, thereby generating the nonlinear thermal loss coefficient.

[0013] Specifically, the nonlinear reduction includes: The thermal tolerance loss state corresponding to the nonlinear thermal loss coefficient is divided into multiple incremental loss intervals, and a corresponding threshold reduction increment is configured for each incremental loss interval. The reference thermal accumulation trip threshold is progressively reduced based on the current thermal tolerance damage state. When the thermal tolerance damage state enters the next incremental damage interval, the corresponding threshold reduction increment is switched so that the reduction degree of the reference thermal accumulation trip threshold increases progressively as the degree of mechanical degradation increases, thus forming the dynamic thermal trip boundary.

[0014] Specifically, the process of forming the restart verification benchmark includes: When the break command is triggered, the thermal potential value, mechanical degradation characterization quantity and nonlinear thermal loss coefficient corresponding to the break time are latched, and the same break status identifier is configured for the three status data. The status data with the break status identifier is written to the non-volatile storage area. After the writing is completed, the status data is reread for integrity verification. The broken status data that passes the verification is used as the restart verification benchmark. The restart verification benchmark is used for restart latch verification.

[0015] Specifically, the restart latch verification includes: Read the nonlinear thermal loss coefficient and mechanical degradation characterization quantity in the restart verification benchmark, determine the restart thermal potential allowable boundary based on the nonlinear thermal loss coefficient, and compare the current mechanical degradation characterization quantity with the preset mechanical degradation allowable boundary for compliance. The current thermal potential value is detected. If the current thermal potential value is lower than the restart thermal potential allowable boundary and the current mechanical degradation characterization quantity meets the mechanical degradation allowable boundary, the restart lockout is released and the reclosing operation is driven. Otherwise, the restart lockout is maintained.

[0016] The beneficial effects of this invention are as follows: (1) By acquiring the transient response of the three-phase current before and after the circuit disconnection device trips, the attenuation trajectory of the change from the running state to the disconnection state is analyzed to form a transient current fingerprint characterizing the current electrical response state of the motor. Compared with the existing technology that only uses the amplitude of the running current or the temperature rise state for protection judgment, the present invention transforms the transient attenuation characteristics during the tripping process into an amplitude correction state and applies it to the fundamental component of the three-phase current during the operating cycle to correct the amplitude reference state. This reduces the fundamental amplitude reference offset caused by the electrical response drift during tripping and operation, improves the stability of mechanical degradation identification based on the calibrated fundamental component, and makes the protection judgment no longer dependent on fixed current parameters.

[0017] (2) Based on the calibrated fundamental component amplitude reference, the operating current is subjected to spectrum analysis to extract the sideband harmonic components corresponding to rotor bar breakage and bearing faults. The energy ratio of the sideband harmonic components relative to the calibrated fundamental component is analyzed to generate mechanical degradation characterization quantities. The mechanical degradation characterization quantities and real-time thermal potential values ​​are simultaneously calibrated to form a nonlinear thermal loss coefficient. This processing method establishes a state correspondence between the traditionally independent mechanical fault diagnosis process and the overload protection process, so that the additional loss changes caused by mechanical degradation can participate in the nonlinear reduction of the thermal accumulation protection threshold. By dividing the thermal loss state according to the thermal potential change amplitude during the increasing mechanical degradation process and progressively increasing the reduction degree, the protection process can reflect the evolution of the actual operating state of the motor, reduce the problem of increased thermal risk and delayed protection response of mechanically degraded motors under the same current conditions, and improve the overload protection adaptability of continuously operating equipment.

[0018] (3) When the interruption command is triggered, the thermal potential value, mechanical degradation characterization quantity, and nonlinear thermal loss coefficient are latched and bound to the same interruption event identifier, and burned to the non-volatile storage area to form a restart verification benchmark across the interruption event. During the restart process, the restart thermal potential allowable boundary is determined based on the nonlinear thermal loss coefficient in the restart verification benchmark, and the current mechanical degradation characterization quantity is compared with the preset mechanical degradation allowable boundary for compliance. This invention maintains the mechanical state information formed before the interruption, so that the restart judgment requires that the current thermal potential value is lower than the restart thermal potential allowable boundary and that the current mechanical degradation characterization quantity meets the mechanical degradation allowable boundary. This avoids the motor from being put back into operation when the thermal state has temporarily recovered but the mechanical state is still unsuitable for operation, and improves the state continuity and reliable interlocking capability of the motor protection process in multiple operation cycles. Attached Figure Description

[0019] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0020] Figure 1 This is a flowchart illustrating a dynamic interlocking method for motor overload protection based on transient current fingerprinting according to the present invention. Figure 2 This is a primary loop diagram of a dynamic interlocking system for motor overload protection based on transient current fingerprinting, as described in this invention. Detailed Implementation

[0021] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided.

[0022] Please see Figures 1-2 , Figure 1 This is a flowchart illustrating a dynamic interlocking method for motor overload protection based on transient current fingerprinting according to the present invention. Figure 2 This is a schematic diagram of the primary circuit structure of the dynamic interlocking system for motor overload protection based on transient current fingerprinting of the present invention. It shows the connection relationship between the three-phase power supply, the current acquisition device, the circuit cutting device, the motor and the microcomputer protection device, as well as the interaction process of the microcomputer protection device with the three-phase current sampling, disconnection control and restart control signals.

[0023] A dynamic interlocking method for motor overload protection based on transient current fingerprinting includes: The transient response of the three-phase current of the continuously running motor before and after the tripping action is obtained, and the decay trajectory of the three-phase current from the running state to the tripping state is analyzed to form a transient current fingerprint. Based on the transient current fingerprint, the fundamental component amplitude reference of the three-phase current is calibrated. Spectral analysis is performed on the three-phase current to extract the sideband harmonic components corresponding to rotor bar breakage and bearing faults. The energy ratio of the sideband harmonic components relative to the fundamental component amplitude reference is analyzed to generate mechanical degradation characterization quantities and nonlinear thermal loss coefficients. The reference thermal accumulation trip threshold is nonlinearly reduced based on the nonlinear thermal loss coefficient to form a dynamic thermal trip boundary. When the real-time thermal potential value exceeds the dynamic thermal trip boundary, a disconnection command is triggered. After disconnection, the mechanical degradation characterization quantity and the nonlinear thermal loss coefficient are written into the non-volatile storage area to form a restart verification benchmark. During restart, the thermal potential value fall-off state and the restart allowable state of the mechanical degradation characterization quantity are verified. If both states are satisfied, the reclosing operation is driven; otherwise, the restart lockout is maintained.

[0024] This embodiment applies to the protection scenario of a continuously operating three-phase asynchronous motor. This embodiment uses a three-phase asynchronous motor continuously driving a water pump in an industrial setting as an example. The motor operates under constant or periodic load conditions for extended periods. During operation, changes in mechanical factors such as bearing wear and rotor bar breakage can alter the internal loss state of the motor, causing deviations in the current response characteristics and heat accumulation process.

[0025] Step 1: Obtain the transient response of the three-phase current of the continuously running motor before and after the disconnection action, analyze the attenuation trajectory of the three-phase current from the running state to the disconnection state, and form a transient current fingerprint.

[0026] Example 1: In this example, the motor operating circuit is configured with a current acquisition device, a circuit disconnection device, and a control processing device. The current acquisition device acquires the A-phase current, B-phase current, and C-phase current in the motor's three-phase input circuit. The circuit disconnection device uses a contactor, circuit breaker, or a protective switch with disconnection control function to disconnect the motor power supply circuit when overload protection is triggered. The control processing device receives the three-phase current sampling data and performs transient response analysis, spectrum processing, and protection status management.

[0027] Specifically, during continuous operation of the motor, the control processing device acquires a three-phase current sampling sequence according to a preset sampling period. When the circuit disconnection device is detected to have a disconnection action, the time position corresponding to the disconnection action is recorded, and the time position is determined as the transient response transition position.

[0028] The transient response of the three-phase current before and after the disconnection action refers to the response process formed by the change of the three-phase current amplitude over time during the process of the motor switching from a stable power supply state to a power-off state. Among them, the current state before the disconnection action reflects the current characteristics corresponding to the current operating load, electromagnetic state, and mechanical operating state of the motor; the current decay state after the disconnection action reflects the response characteristics corresponding to the state of the motor windings, inductor energy storage, and internal losses.

[0029] During the specific data acquisition process, a transient sampling window is established with the break point as the center, and the current amplitude sequences of phase A, phase B, and phase C are acquired within the transient sampling window.

[0030] For any phase current, such as phase A current, its transient response sequence is expressed as: I a (t)={i a (t1),i a (t2),...,i a (t n )}, Among them: I a (t) represents the transient response sequence of phase A current; i a (t n () represents the amplitude of phase A current at the nth sampling time; t n This represents the nth sampling time point.

[0031] By performing state analysis on the transient response sequence, the current amplitude during the stable operation phase before the interruption, the direction of amplitude change after the interruption, and the stable response state after the current interruption are obtained.

[0032] Specifically, in this embodiment, the following are extracted respectively: (1) Initial amplitude state before the break; The initial amplitude state is used to characterize the actual operating current level of the motor before the disconnection occurs. For example: I 0a ,I 0b ,I 0c , These represent the initial current amplitudes of phases A, B, and C before the breaking time, respectively.

[0033] (2) The direction and state of amplitude change; The direction of amplitude change is used to describe the trend of the current in each phase changing from the operating state to the interrupted state after the interruption.

[0034] For example: D x = , D x This indicates the direction of change of the corresponding phase current; x represents phase A, phase B, or phase C.

[0035] (3) Stable amplitude state after current interruption; The stable amplitude state is used to represent the residual current state after the transient response ends: I sa ,I sb ,I sc , These represent the stable response amplitudes after the interruption of phases A, B, and C, respectively.

[0036] After obtaining the above three types of state data, the transient states of each phase are arranged according to the three-phase phase sequence relationship to form a three-phase response sequence: S t ={I 0a D a ,I sa ,I0 b D b ,I sb ,I 0c D c ,I sc}, Wherein: S t Represents the three-phase transient response sequence; I0 represents the initial amplitude state before the break; D represents the amplitude change direction state; I s This indicates the stable amplitude state after the current is interrupted.

[0037] Furthermore, to reduce the impact of differences in rated capacity and current level of motors on the feature expression, the three-phase response sequence is normalized.

[0038] Specifically, the amplitude states are converted to a unified characteristic range: F t =N(S t ), Wherein: F t Represents the formed transient current fingerprint; N(·) represents the normalization encoding process; S t This represents the original three-phase response sequence.

[0039] After the above processing, the transient current fingerprint no longer represents only a single interruption action, but forms a comprehensive current characteristic that includes the operating state before interruption, transient change trend and interruption response state, which is used for subsequent operating current reference calibration.

[0040] After forming the transient current fingerprint, this embodiment further performs the fundamental component amplitude reference calibration process.

[0041] Specifically, due to the influence of load changes, winding state changes, and mechanical state changes during motor operation, the amplitude of the fundamental component in the three-phase current may change. If a fixed fundamental amplitude is directly used as the reference value for spectrum analysis, it will lead to deviations in the subsequent sideband harmonic energy analysis.

[0042] Therefore, this embodiment utilizes the pre-disconnection operating state information in the transient current fingerprint to calibrate the fundamental component amplitude of the three-phase current within the operating cycle.

[0043] First, the initial amplitude state before the break is read from the transient current fingerprint: I0={I 0a ,I 0b ,I 0c}, Simultaneously, the fundamental frequency of the three-phase current collected during the normal operation cycle of the motor is extracted to obtain the corresponding fundamental frequency amplitude: I1={I 1a ,I 1b ,I 1c}, Where: I1 represents the three-phase fundamental amplitude value extracted during the operating cycle; I 1a ,I 1b ,I 1c These represent the amplitudes of the three-phase fundamental components.

[0044] Subsequently, based on the relationship between the operating state before the break and the current fundamental frequency state, the fundamental frequency correction state is formed: C f =Φ(I0,I1), Where: C f Φ(·) represents the fundamental correction state; Φ(·) represents the processing procedure for establishing a correspondence between the two sets of amplitude states.

[0045] Furthermore, the fundamental correction state is applied to the current fundamental amplitude to obtain the calibrated fundamental component amplitude reference: I1′=Cf×I1, Where: I1′ represents the calibrated fundamental component amplitude reference.

[0046] The calibrated fundamental component amplitude reference is used as an energy reference in the subsequent mechanical degradation feature extraction process. It is used to reduce the fundamental amplitude offset caused by changes in motor operating status, so that the energy changes of sideband harmonic components can more accurately reflect changes in mechanical status.

[0047] Through the above process, this embodiment uses the transient current response during the motor disconnection process to establish a transient current fingerprint, and further uses the transient current fingerprint to correct the reference state of the fundamental component amplitude within the operating cycle, so that the disconnection transient information is transformed from auxiliary information in the traditional protection execution process into basic data for subsequent mechanical state analysis, providing a data basis for the generation of subsequent mechanical deterioration characterization quantities and thermal protection state adjustment.

[0048] Step 2: Based on the transient current fingerprint, calibrate the fundamental component amplitude reference of the three-phase current, perform spectrum analysis on the three-phase current, extract the sideband harmonic components corresponding to rotor bar breakage and bearing faults, analyze the energy ratio of the sideband harmonic components relative to the fundamental component, and generate mechanical degradation characterization quantities and nonlinear thermal loss coefficients.

[0049] Example 2: Based on the transient current fingerprint and fundamental component amplitude benchmark established in Example 1, this example performs spectrum analysis on the three-phase current of a continuously running motor to obtain the sideband harmonic components corresponding to rotor bar breakage and bearing faults. The energy change of the sideband harmonic components relative to the calibrated fundamental component is converted into a mechanical degradation characterization quantity. Furthermore, a real-time thermal potential value that changes synchronously with the mechanical degradation characterization quantity is introduced to analyze the correspondence between the change in mechanical degradation degree and the change in heat accumulation, forming a nonlinear thermal loss coefficient, which provides a basis for the nonlinear reduction of the subsequent heat accumulation trip threshold.

[0050] I. Spectrum Analysis of Three-Phase Operating Current In this embodiment, the control processing device continuously acquires the current sampling sequences of phases A, B, and C during the continuous operation of the motor, and forms a three-phase current sampling window according to a preset operating cycle. The operating cycle is used to ensure that adjacent spectrum results have a uniform time scale and to enable the mechanical degradation state to be tracked along the continuous operation process.

[0051] Let the three-phase current sampling sequences corresponding to the k-th operating cycle be as follows: X a (k)={x a (1),x a (2),...,x a (N)}, X b (k)={x b (1),x b (2),...,x b (N)}, Xc (k)={x c (1),x c (2),...,x c (N)}, Among them, X a (k), X b (k), X c (k) represents the current sampling sequences of phase A, phase B, and phase C in the k-th operating cycle, respectively; x a (n), x b (n), x c (n) represents the nth sample value of the corresponding phase; N represents the number of sample points in a single operating cycle.

[0052] Frequency domain analysis was performed on the above three-phase current sampling sequences to obtain the corresponding spectral sequences: G x (k,f)=FFT[X x (k)], Among them, G x (k,f) represents the spectrum result of the x-th phase current at frequency f during the k-th operating cycle; x can be A, B or C; FFT[·] represents the spectrum analysis process of converting the time-domain sampled sequence into a frequency-domain sequence.

[0053] After completing the spectrum analysis, the frequency position of the fundamental component is first located. Let the operating fundamental frequency be f1, then establish frequency search ranges on both sides with f1 as the center, and perform sideband searches for the frequency offset positions corresponding to rotor bar breakage and bearing faults respectively.

[0054] II. Extraction of Harmonic Components from the Sideband of Broken Rotor Bars For a three-phase asynchronous motor, broken rotor bars alter the rotor current distribution and air gap magnetic field state, causing a slip-related sideband response to appear in the stator current spectrum near the fundamental frequency. This embodiment determines the slip *s* based on the current motor operating speed and synchronous speed, and follows the following: f r =(1±2s)f1, Determine the location of the characteristic frequency of the broken rotor bar.

[0055] Among them, f r This indicates the position of the sideband frequency corresponding to the broken rotor bar; s represents the current motor slip; and f1 represents the operating fundamental frequency.

[0056] Control processing device at f r A search range is established near the corresponding frequency position, adjacent spectral peaks are extracted in a directional manner, and the corresponding sideband harmonic energy is recorded to form the rotor bar sideband energy state E. r (k).

[0057] The E r (k) is not directly used as a binary judgment result of "whether the bar is broken", but retains the changing state in the continuous operation cycle for subsequent description of the change in the degree of mechanical deterioration.

[0058] III. Extraction of Harmonic Components from Bearing Fault Sidebands In bearing wear scenarios, localized bearing defects, raceway wear, and rolling element damage can cause periodic mechanical disturbances in the motor, which are reflected in the stator current spectrum via electromechanical coupling. The corresponding fault characteristic frequencies are determined based on the bearing structural parameters.

[0059] Taking a bearing outer ring failure as an example, its characteristic frequency can be expressed as: f bo =Z n (1-d·cosθ / D) / 2, Among them, f bo The bearing outer ring fault characteristic frequency is represented by Z; the number of rolling elements is represented by n; the bearing speed is represented by d; the rolling element diameter is represented by D; and the bearing pitch circle diameter is represented by θ.

[0060] For other conditions such as bearing inner ring failure and rolling element failure, the fault characteristic frequency is determined using the corresponding structural parameters, and the fault is searched at the corresponding frequency positions on both sides of the fundamental wave.

[0061] The control processing device extracts the spectral peaks and their energy states within the corresponding frequency range to form the bearing fault sideband energy state E. b (k), where E b (k) represents the bearing fault sideband energy corresponding to the kth operating cycle.

[0062] Through the above processing, the rotor broken bar sideband energy state E is obtained in this embodiment. r (k) and bearing fault sideband energy state E b (k), and retain the change trajectory of the two in the continuous running cycle.

[0063] IV. Energy proportion based on the calibrated fundamental component amplitude reference Example 1 has already established the fundamental component amplitude reference. To avoid performing dimensionally inconsistent calculations between the sideband energy and the fundamental amplitude, this example converts the fundamental component amplitude reference into a corresponding fundamental energy representation.

[0064] Let the calibrated fundamental component amplitude reference be I1′(k). Then, under the same sampling window and uniform normalization conditions, its corresponding fundamental energy is characterized as: E f (k)=[I1′(k)] 2 , Among them, Ef (k) represents the fundamental energy characterization of the kth operating cycle; I1′(k) represents the calibrated fundamental component amplitude reference obtained in Example 1.

[0065] Subsequently, the energy percentages of the rotor bar breakage sideband and the bearing failure sideband were calculated separately: R r (k)=E r (k) / E f (k), R b (k)=E b (k) / E f (k), Among them, R r (k) represents the proportion of the rotor bar breakage sideband energy to the fundamental frequency energy; R b (k) represents the proportion of bearing fault sideband energy to fundamental energy.

[0066] By using the fundamental energy corresponding to the calibrated fundamental component amplitude benchmark as a unified reference, the drift in sideband proportion caused by directly using the uncalibrated fundamental state can be avoided, and the sideband energy proportions obtained in different operating cycles can have a unified basis for comparison.

[0067] V. Continuous generation of mechanical degradation characterization quantities In obtaining R r (k) and R b After (k), this embodiment does not directly determine the mechanical fault level based on the sideband energy ratio of a certain operating cycle, but tracks the changing trend of the energy ratio along the continuous operating cycle.

[0068] First, for R in the continuous running cycle r (k),R b (k) Perform trend tracking to obtain the degree of deterioration change corresponding to rotor bar breakage characteristics and bearing failure characteristics, respectively.

[0069] Furthermore, the synchronous changes of the two types of fault characteristics during continuous operating cycles are jointly characterized to form a mechanical degradation characterization quantity: M(k)=Γ[R r (k),R b [(k),T(k)], Where M(k) represents the mechanical degradation characterization quantity in the k-th operating cycle; T(k) represents R r (k) and R b (k) represents the trend of change in continuous operation cycle; Γ(·) represents the processing relationship that jointly characterizes the two types of fault sideband change states and their continuous change trends.

[0070] In practical applications, when bearing wear gradually worsens, R b (k) will continue to rise, and as the rotor bar breakage condition gradually worsens, R r (k) will show a continuous increase. The control processing device avoids directly taking a single sporadic spectral peak as a mechanical degradation state by continuous periodic tracking, so that M(k) reflects the evolution of the mechanical state during continuous operation.

[0071] VI. Establish a synchronous state between mechanical degradation and thermal potential changes. After obtaining the mechanical degradation characterization quantity, this embodiment further introduces a real-time thermal potential value, so that the mechanical degradation state no longer stays at the fault diagnosis level, but establishes a corresponding relationship with the motor thermal accumulation process.

[0072] The real-time thermal potential value is used to characterize the cumulative thermal load state generated and continuously retained by the three-phase current during the current operation of the motor. The real-time thermal potential value does not directly represent the winding temperature, but serves as a state quantity during the thermal accumulation protection process. The control processing device continuously updates the real-time thermal potential value according to the operating cycle, so that the current thermal load of the current operating cycle and the thermal accumulation state retained in the previous operating cycle jointly participate in the thermal potential value update.

[0073] The real-time thermal potential value for the kth operating cycle is expressed as: H(k) = ρH(k-1) + (1-ρ)Q(k), Where H(k) represents the real-time thermal potential value of the kth operating cycle; H(k-1) represents the thermal potential value of the previous operating cycle; Q(k) represents the current thermal load corresponding to the current operating cycle; ρ represents the thermal potential retention factor, with a value range of 0<ρ<1, which is used to characterize the degree of retention of the thermal accumulation state of the previous operating cycle in the current operating cycle.

[0074] In this embodiment, Q(k) is determined based on the effective value of the three-phase current and the equivalent heat loss state of the winding, specifically expressed as: Q(k) = R e ( (k)+ (k)+ (k)) / 3, Among them, I a (k), I b (k), I c (k) represents the effective values ​​of the currents in phases A, B, and C during the k-th operating cycle, respectively; R e This represents the equivalent resistance parameter of the winding.

[0075] Through the above relationship, Q(k) and H(k) adopt the same thermal load characterization scale, so that the current thermal load in the continuous operation cycle can form a continuous thermal accumulation state according to the thermal potential maintenance relationship, and serve as the comparison object for the subsequent reference thermal accumulation trip threshold and dynamic thermal trip boundary.

[0076] After H(k) is formed, it is synchronized with the mechanical degradation characterization quantity M(k) obtained in the same operating cycle to establish a synchronous state sequence: {M(k),H(k)}. Where M(k) represents the mechanical degradation characteristic of the k-th operating cycle, and H(k) represents the real-time thermal potential value of the same operating cycle. The two state data points are associated using the same operating cycle identifier, ensuring that changes in mechanical degradation and thermal potential originate from the same operating state. Furthermore, obtain the state changes between adjacent running cycles: ΔM(k)=M(k)-M(k-1), ΔH(k)=H(k)-H(k-1), Where ΔM(k) represents the periodic change of the mechanical degradation characterization quantity, and ΔH(k) represents the periodic change of the real-time thermal potential value.

[0077] When the mechanical degradation characterization quantity undergoes an effective change, the degree of thermal potential response corresponding to the mechanical degradation change is further formed: G(k) = ΔH(k) / ΔM(k), Wherein, G(k) represents the degree of thermal potential response corresponding to the mechanical deterioration change.

[0078] When the change in mechanical degradation characteristics between consecutive operating cycles is lower than the preset effective change range, the thermal response degree is not updated and the previous effective state is maintained; when the change in mechanical degradation characteristics enters the effective change range, the thermal response degree is updated according to ΔM(k) and ΔH(k) of the current cycle.

[0079] VII. Formation of nonlinear thermal loss coefficient Based on the M(k), H(k), and G(k) states formed during continuous operation cycles, this embodiment divides the degree of mechanical deterioration into an increasing range of thermal damage states.

[0080] For example, mechanical degradation can be divided into mild, moderate and severe ranges according to the mechanical degradation characterization quantity, and the degree of change of G(k) corresponding to each range can be further compared.

[0081] When G(k) changes little in the mild range, but begins to increase significantly after entering the moderate range, and further increases in the severe range, it indicates that the effect of mechanical degradation on heat accumulation has a progressive amplification characteristic.

[0082] Therefore, this embodiment does not directly convert M(k) into thermal loss using a fixed ratio, but instead sets different loss change rates based on the degree of thermal potential response corresponding to different mechanical degradation intervals, forming a piecewise progressive nonlinear loss relationship: K h =g[M(k),G(k)], Among them, K h denoted as the nonlinear thermal loss coefficient; M(k) represents the mechanical degradation characterization quantity; G(k) represents the degree of thermal potential response corresponding to the change in mechanical degradation; g(·) represents the relationship between determining the thermal tolerance loss state based on different mechanical degradation ranges and their degree of thermal potential response.

[0083] For example, in the mild mechanical degradation range, the thermal loss coefficient changes relatively slowly; after entering the moderate mechanical degradation range, the degree of thermal loss change increases according to the increasing state of G(k); after entering the severe mechanical degradation range, the loss increment is further increased, so that the thermal tolerance loss corresponding to the increase in the degree of mechanical degradation changes progressively.

[0084] The resulting K h As the input for the nonlinear reduction of the subsequent thermal accumulation trip threshold, the mechanical deterioration state is brought into the thermal protection process through the actual thermal potential response, rather than remaining in the fault detection or alarm stage.

[0085] This embodiment completes the following processing chain: three-phase current spectrum analysis, sideband harmonic extraction, fundamental energy normalization, continuous characterization of mechanical degradation, synchronous analysis of mechanical degradation and thermal potential, and formation of nonlinear thermal loss. This provides a state basis for subsequent reduction of the thermal accumulation tripping threshold based on the nonlinear thermal loss coefficient.

[0086] Step 3: Based on the nonlinear thermal loss coefficient, the reference thermal accumulation trip threshold is nonlinearly reduced to form a dynamic thermal trip boundary. When the real-time thermal potential value exceeds the dynamic thermal trip boundary, a disconnection command is triggered.

[0087] In Example 3, based on the mechanical degradation characterization quantity and nonlinear thermal loss coefficient formed in Example 2, the current thermal potential value of the motor is continuously updated, and the nonlinear thermal loss coefficient is converted into the corresponding thermal tolerance loss state. According to the thermal tolerance loss state, the reference thermal accumulation trip threshold is subjected to graded progressive nonlinear reduction to form a dynamic thermal trip boundary corresponding to the current mechanical degradation state. When the real-time thermal potential value exceeds the dynamic thermal trip boundary, the circuit cut-off device is triggered to perform disconnection.

[0088] I. Determination of the Reference Thermal Accumulation Trip Threshold When the motor is in normal operating mechanical condition, the reference thermal accumulation trip threshold is determined based on the motor's rated capacity, the winding's allowable thermal load, and the thermal protection requirements of the protection device, and is denoted as H. baseThe reference thermal accumulation trip threshold represents the thermal accumulation state that the motor is allowed to reach without mechanical deterioration or damage.

[0089] The real-time thermal potential value in this embodiment is the same as the thermal potential value H(k) obtained in Embodiment 2. The thermal potential value represents the cumulative heat load state corresponding to the current operating cycle and is continuously updated with the three-phase current heat load and the heat accumulation state of the previous operating cycle.

[0090] Under normal mechanical conditions, with H(k) ≥ H base As a criterion for thermal overload detection, H(k) represents the real-time thermal potential value in the k-th operating cycle. base This represents the reference thermal accumulation trip threshold.

[0091] When the motor exhibits mechanical deterioration, continue to use H base As a fixed protection threshold, it cannot reflect the decrease in thermal tolerance caused by mechanical additional losses. Therefore, this embodiment uses the nonlinear thermal loss coefficient K formed in Embodiment 2. h (k) The reference thermal accumulation trip threshold is state-based.

[0092] II. Interval Division of Nonlinear Thermal Loss State Example 2 has established a nonlinear thermal loss coefficient K based on the mechanical degradation characterization quantity M(k), the real-time thermal potential value H(k), and their synchronous change states during continuous operation cycles. h (k). The K h (k) is used to indicate the degree of heat resistance loss corresponding to the current mechanical deterioration state.

[0093] This embodiment does not include K. h (k) is not directly used as the threshold reduction ratio, but is first divided into multiple incremental reduction intervals according to the corresponding degree of heat resistance loss. The incremental reduction intervals are arranged in order of increasing mechanical degradation, and a corresponding threshold reduction increment is configured for each interval.

[0094] Let the heat resistance loss range be: Z1, Z2, ..., Z j , Among them, Z j This represents the j-th increasing loss interval.

[0095] For each increasing loss interval, configure the threshold reduction level: C1 <C2<...<C j , Among them, C j This indicates the degree of threshold reduction corresponding to the j-th increasing loss interval.

[0096] The C jIt is not directly generated by a fixed ratio, but is determined based on the change in the degree of thermal response as the degree of mechanical degradation increases in Example 2. When the degree of mechanical degradation is low, it corresponds to a smaller threshold reduction; when the degree of mechanical degradation enters a higher damage range, it corresponds to a larger threshold reduction.

[0097] This range configuration ensures that the change in the protection threshold corresponding to the increase in mechanical degradation does not decrease proportionally, but rather forms a progressively increasing reduction relationship.

[0098] III. Forming a dynamic thermal trip boundary by performing nonlinear reduction The control processing unit first reads the nonlinear thermal loss coefficient K corresponding to the current operating cycle. h (k), according to K h (k) determines the current interval number j within the heat resistance loss interval, and then calls the threshold reduction degree C corresponding to the interval. j .

[0099] The baseline thermal accumulation trip threshold is reduced according to the current loss range to form a dynamic thermal trip boundary: H dyn (k)=H base (1-C j ), K h (k)∈Z j , Wherein: H dyn (k) represents the dynamic thermal trip boundary corresponding to the kth operating cycle.

[0100] For example, when K h (k) When in the first loss interval Z1, use a smaller C1 for H base Execute reduction; as mechanical deterioration worsens during continuous operation, K h (k) When entering the second loss interval Z2, the control processing device switches the current threshold reduction level to C2. Since C2 > C1, the dynamic thermal trip boundary is further reduced; when K h (k) When entering a higher loss range, repeat the range switching to further increase the threshold reduction.

[0101] This achieves the following: Increased mechanical degradation → improved thermal tolerance → increased threshold voltage reduction → further tightening of dynamic thermal trip boundary.

[0102] This process is the nonlinear reduction in this embodiment. Its nonlinearity does not come from a simple fixed ratio adjustment, but is formed by the state switching between the incremental loss interval and the incremental threshold reduction degree.

[0103] IV. Continuous updating of dynamic thermal trip boundaries During continuous operation of the motor, the mechanical degradation characteristic quantity M(k) and the nonlinear thermal loss coefficient K are... h (k) may change with the operating cycle. Therefore, the control processing device obtains an updated K in each new operating cycle. h After (k), the current loss interval positioning is re-executed.

[0104] When the updated K h (k) is still within the original loss range Z j During the internal time, maintain the corresponding C j and H dyn (k); When K h (k) Entering the next loss interval Z j+1 When the threshold reduction level C is reached, switch to the corresponding threshold reduction level. j+1 and reformed: H dyn (k+1)=H base (1-C j+1 ), Because of C j+1 >C j Therefore, as the degree of mechanical degradation further increases, the dynamic thermal tripping boundary decreases accordingly.

[0105] Through this continuous update method, the dynamic thermal trip boundary will not remain a fixed value after the first identification of mechanical deterioration, but will be adjusted in real time as the mechanical deterioration state continues to change, so that the thermal protection state can follow the actual mechanical state of the motor.

[0106] V. Comparison and Judgment of Real-time Thermal Potential Value and Dynamic Thermal Trip Boundary After completing the dynamic thermal trip boundary update, the control processing device obtains the real-time thermal potential value H(k) corresponding to the current operating cycle, and compares the real-time thermal potential value with the dynamic thermal trip boundary H. dyn (k) Perform amplitude comparison.

[0107] When H(k) > H dyn When (k), it is determined that the current heat accumulation state has exceeded the allowable heat protection range corresponding to the mechanical deterioration state. The control processing device latches the current protection state and outputs a disconnection command to the circuit disconnection device.

[0108] After receiving the disconnection command, the circuit disconnection device cuts off the motor power supply circuit, causing the motor to switch from the running state to the disconnection state.

[0109] Simultaneously with the triggering of the break command, the control processing device reads the mechanical degradation characterization quantity M(k) and the nonlinear thermal loss coefficient K corresponding to the current operating cycle. h(k) and pass both to the disconnection state holding process in Embodiment 4. Thus, the current mechanical degradation state will not disappear from the protection process due to circuit disconnection, but will serve as the data source for subsequent restart verification.

[0110] VI. Application Process of this Embodiment Taking a three-phase asynchronous motor that continuously drives a water pump as an example, the motor is in a low mechanical degradation state in the initial stage of operation, and the nonlinear thermal loss coefficient K h (k) Located in a lower wear range, the dynamic thermal trip boundary is close to the reference thermal accumulation trip threshold. As bearing wear continues to develop, the mechanical degradation characterization quantity obtained in Example 2 gradually increases, and the synchronous thermal potential response degree improves. The nonlinear thermal wear coefficient enters a higher wear range, and the control processing device switches to a greater threshold reduction degree accordingly.

[0111] Therefore, under the same operating current conditions, when mechanical deterioration causes an increase in the rate of thermal potential growth, the dynamic thermal trip boundary can enter the protection range before the reference thermal accumulation trip threshold under normal mechanical conditions, so that the motor that already has mechanical deterioration will no longer continue to use the fixed thermal protection boundary under normal conditions.

[0112] Step 4: After disconnection, write the mechanical degradation characterization quantity and nonlinear thermal loss coefficient into the non-volatile storage area to form a restart verification benchmark. During restart, verify the thermal potential value fall-off state and the restart allowable state of the mechanical degradation characterization quantity. If both states are satisfied, drive the reclosing operation; otherwise, maintain the restart lockout.

[0113] Example 4: Based on Example 3's formation of dynamic thermal trip boundaries and triggering of trip commands, this example latches and non-volatilely maintains the motor's thermal state and mechanical degradation state at the moment of tripping. Upon subsequent motor restart, the tripping state is read to form restart thermal potential allowable boundaries and mechanical degradation allowable boundaries, respectively. A joint verification is then performed on the current thermal state and current mechanical degradation state. This process ensures that the mechanical degradation state does not disappear from the protection process due to motor power failure and allows the mechanical degradation state formed before tripping to continue participating in subsequent restart permission judgments.

[0114] I. Latching of Disconnected State Data In Example 3, when the real-time thermal potential value H(k) exceeds the dynamic thermal trip boundary H dyn When (k) occurs, the control processing device outputs a break command. Upon triggering the break command, the thermal potential value, mechanical degradation characterization quantity, and nonlinear thermal loss coefficient corresponding to the current operating cycle are immediately latched.

[0115] in: S k ={H(k),M(k),K h (k)}, Among them, Sk H(k) represents the set of data for the k-th breakpoint state; H(k) represents the real-time thermal potential value corresponding to the breakpoint time; M(k) represents the mechanical degradation characterization quantity corresponding to the breakpoint time; K h (k) represents the nonlinear thermal loss coefficient corresponding to the break point.

[0116] In this embodiment, all three status data items use the same segmentation status identifier T. s By associating them, the following can be formed: R s ={T s ,H(k),M(k),K h (k)}, Among them, R s Indicates the broken state record; T s This indicates the status identifier corresponding to this segmentation.

[0117] The disconnection status identifier can be formed using a disconnection count value, a timestamp, or a combination of both, to distinguish different disconnection records formed by multiple consecutive protection actions. In this embodiment, "disconnection timestamp + disconnection sequence number" is used as the disconnection status identifier.

[0118] By using a unified disconnection status identifier, it can be ensured that the thermal potential value, mechanical degradation characterization quantity, and nonlinear thermal loss coefficient always belong to the same disconnection status, thus avoiding reading status data belonging to different disconnection times after multiple protection actions.

[0119] 2. The breakout status record is written to the non-volatile storage area. After the breakout status data is latched, the control processing device writes the breakout status record into a non-volatile storage area. The non-volatile storage area can be an EEPROM, FRAM, or a Flash storage area with power-down retention function. In this embodiment, a non-volatile storage area with power-down retention function is used.

[0120] After the disconnection status record is written, even if the motor power supply circuit remains disconnected or the control processing device is powered on again, the R s It can still be retained.

[0121] To avoid incomplete data writing during the segmentation process, this embodiment performs a readback verification after writing the segmentation status record. Specifically, the control processing device reads the newly written status record based on the segmentation status identifier and performs a consistency verification between the read result and the status data latched before writing.

[0122] when = When the time is right, the current breakout status record is determined to be valid, and the status record is set as the restart verification benchmark.

[0123] in: This indicates a fragmentation status record read from a non-volatile memory area; This indicates the interrupt status record latched when the interrupt instruction is triggered.

[0124] If the readback result is inconsistent with the latch state, the current interrupted locking state will be maintained, the record will not be used as a valid restart verification benchmark, and the motor power supply circuit will remain disconnected.

[0125] III. Conversion from Restart Verification Baseline to Restart Thermal Potential Allowable Boundary When the motor needs to be restarted, the control processing unit first reads the valid restart verification benchmark: R s0 ={T s H s M s ,K hs}, Wherein: T s Indicates a valid break status; H s Indicates the thermal potential value preserved at the time of interruption; M s K represents the mechanical degradation characterization quantity preserved at the time of fragmentation. hs It represents the nonlinear thermal loss coefficient preserved at the time of disconnection, which is used to characterize the degree of thermal resistance loss corresponding to the mechanical deterioration state of the motor at the time of disconnection.

[0126] The control processing device according to the K hs Determine the permissible thermal potential state for the current restart phase. The permissible restart thermal potential boundary is denoted as H. r , which represents the allowable boundary of restart thermal potential corresponding to the thermal loss state at the time of breakage.

[0127] Therefore, the restart phase does not adopt the approach of allowing startup once the current thermal potential value drops to any normal range. Instead, it first redetermines the allowable thermal potential boundary based on the thermal loss state maintained at the time of disconnection.

[0128] IV. Restart Permission Boundary Verification under Current Mechanical Deterioration State After the restart thermal potential limit is established, the control processing device reacquires the current mechanical degradation characterization quantity M. c This indicates the mechanical deterioration state of the motor when the restart judgment is made.

[0129] Simultaneously, a mechanical degradation allowable boundary M is preset. lim This indicates the upper limit of mechanical deterioration at which the motor is allowed to be put back into operation.

[0130] The control processing device will use the current mechanical degradation characterization quantity M c With the mechanical degradation allowable boundary Mlim Perform a compliance comparison. When M c ≤M lim When M... c >M lim At that time, maintain the restart lockout.

[0131] The judgment here is based on the relationship between the current mechanical degradation state and the preset restart allowable boundary, rather than simply comparing the current mechanical degradation characteristic with the mechanical degradation characteristic saved at the time of disassembly. Therefore, even if the current mechanical degradation level is lower than the state at the time of disassembly, as long as it still exceeds the restart allowable boundary, the restart lockout will not be lifted.

[0132] V. Joint Verification of Thermal and Mechanical Conditions To obtain the current thermal potential value H c And the current mechanical degradation characterization quantity M c Then, the control processing device simultaneously performs two restart checks.

[0133] The first item is thermal state verification: H c <H r , The second item is mechanical condition verification: M c ≤M lim , When both conditions are met simultaneously, the control processing device determines that the motor simultaneously meets the thermal recovery condition and the mechanical condition allowable condition, releases the restart interlock, and outputs a reclosing command to the circuit disconnection device or the reclosing control mechanism.

[0134] If any condition is not met, the restart interlock remains in place and no reclosing command is output.

[0135] VI. Status recovery after reclosing When both the thermal potential and mechanical deterioration conditions meet the restart conditions, the control processing device outputs a reclosing command, the circuit disconnection device reconnects the motor power supply circuit, and the motor enters the restart process.

[0136] After reclosing is completed, the control processing device re-establishes the operating cycle count and re-executes the three-phase current transient response acquisition in Example 1 and the mechanical degradation characterization process in Example 2. The original disconnection status record is retained as a historical protection record, while the current re-operation status serves as the basis for new subsequent monitoring.

[0137] If the motor experiences further mechanical deterioration, the mechanical deterioration characteristics will change again, the nonlinear thermal loss coefficient will be re-formed, and the thermal accumulation trip threshold will be dynamically reduced again. If the corresponding dynamic thermal trip boundary is exceeded again, the trip will be triggered again, and a new trip status record will be formed.

[0138] Through the above method, the entire protection process forms a continuous state cycle: Operational status monitoring → Mechanical deterioration characterization → Dynamic adjustment of thermal protection → Disconnection → Status maintenance → Joint restart verification of thermal and mechanical status → Re-operation or maintaining lockout.

[0139] The key to this embodiment is that the mechanical degradation state is not cleared after the power supply is interrupted following motor disconnection. Instead, it is retained across the disconnection stage through disconnection status identification and non-volatile storage. During restart, the stored thermal degradation state is used to determine the allowable boundary of the restart thermal potential, while an independent permissibility judgment is performed on the current mechanical degradation state. This avoids unlocking the system solely based on the completion of cooling or a decrease in thermal potential, allowing the mechanical degradation state to persist throughout motor operation, protection disconnection, and subsequent restart processes.

[0140] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A dynamic interlocking method for motor overload protection based on transient current fingerprinting, characterized in that, Includes the following steps: The transient response of the three-phase current of the continuously running motor before and after the tripping action is obtained, and the decay trajectory of the three-phase current from the running state to the tripping state is analyzed to form a transient current fingerprint. Based on the transient current fingerprint, the fundamental component amplitude reference of the three-phase current is calibrated. Spectral analysis is performed on the three-phase current to extract the sideband harmonic components corresponding to rotor bar breakage and bearing faults. The energy ratio of the sideband harmonic components relative to the fundamental component amplitude reference is analyzed to generate mechanical degradation characterization quantities and nonlinear thermal loss coefficients. The reference thermal accumulation trip threshold is nonlinearly reduced based on the nonlinear thermal loss coefficient to form a dynamic thermal trip boundary. When the real-time thermal potential value exceeds the dynamic thermal trip boundary, a disconnection command is triggered. After disconnection, the mechanical degradation characterization quantity and the nonlinear thermal loss coefficient are written into the non-volatile storage area to form a restart verification benchmark. During restart, the thermal potential value fall-off state and the restart allowable state of the mechanical degradation characterization quantity are verified. If both states are satisfied, the reclosing operation is driven; otherwise, the restart lockout is maintained.

2. The method according to claim 1, characterized in that, The formation process of the transient current fingerprint includes: Determine the current state transition position corresponding to the interruption moment, and extract the three-phase current change sequence before and after the transition position; establish a three-phase transient response sequence according to the attenuation start state, change direction and current interruption stability state of each phase current, and uniformly encode the transient response sequence to form the transient current fingerprint.

3. The method according to claim 1, characterized in that, The calibration process for the fundamental component amplitude reference includes: Extract the pre-break amplitude state and transient decay amplitude state from the transient current fingerprint, analyze the response change relationship between the pre-break amplitude state and the transient decay amplitude state, and form an amplitude correction state; The amplitude correction state is applied to the fundamental component of the three-phase current during the operating cycle to correct the amplitude reference state of the fundamental component, and the corrected amplitude of the fundamental component is used as the amplitude reference of the fundamental component.

4. The method according to claim 1, characterized in that, The spectrum analysis includes: The three-phase current sampling sequence is obtained according to the operating cycle, and frequency domain analysis is performed on the three-phase current sampling sequence to locate the frequency position corresponding to the fundamental component. Using the frequency position as a reference, analyze the frequency response on both sides, perform directional retrieval according to the frequency offset position corresponding to rotor bar breakage and bearing failure, extract the corresponding sideband harmonic components, and generate the energy state and change state of the sideband harmonic components within the continuous operating cycle.

5. The method according to claim 1, characterized in that, The process of generating the mechanical degradation characterization quantity includes: Extract the sideband harmonic components corresponding to rotor bar breakage and bearing faults, and analyze the corresponding sideband energy change state according to different fault characteristics; The sideband energy change state is normalized and characterized using the fundamental component amplitude as a reference. The degree of degradation change corresponding to different fault characteristics is extracted, and the trend of the degree of degradation change is tracked along the continuous operation cycle. The degree of degradation change and its trend are jointly characterized to form the mechanical degradation characterization quantity.

6. The method according to claim 1, characterized in that, The formation process of the nonlinear thermal loss coefficient includes: Extract the synchronous change state of the mechanical degradation characterization quantity and the real-time thermal potential value within the continuous operating cycle, and establish the state correspondence between the degree of mechanical degradation and the degree of thermal potential change. The thermal loss states are divided according to the magnitude of thermal potential change during the increasing degree of mechanical deterioration. The change in loss increment between adjacent thermal loss states is identified, and a nonlinear correspondence between the degree of mechanical deterioration and the degree of thermal resistance loss is formed according to the change in loss increment, thereby generating the nonlinear thermal loss coefficient.

7. The method according to claim 1, characterized in that, The nonlinear compression includes: The thermal tolerance loss state corresponding to the nonlinear thermal loss coefficient is divided into multiple incremental loss intervals, and a corresponding threshold reduction increment is configured for each incremental loss interval. The reference thermal accumulation trip threshold is progressively reduced based on the current thermal tolerance damage state. When the thermal tolerance damage state enters the next incremental damage interval, the corresponding threshold reduction increment is switched so that the reduction degree of the reference thermal accumulation trip threshold increases progressively as the degree of mechanical degradation increases, thus forming the dynamic thermal trip boundary.

8. The method according to claim 1, characterized in that, The process of forming the restart verification benchmark includes: When the break command is triggered, the thermal potential value, mechanical degradation characterization quantity and nonlinear thermal loss coefficient corresponding to the break time are latched, and the same break status identifier is configured for the three status data. The status data with the break status identifier is written to the non-volatile storage area. After the writing is completed, the status data is reread for integrity verification. The broken status data that passes the verification is used as the restart verification benchmark. The restart verification benchmark is used for restart latch verification.

9. The method according to claim 8, characterized in that, The restart lockout verification includes: Read the nonlinear thermal loss coefficient and mechanical degradation characterization quantity in the restart verification benchmark, determine the restart thermal potential allowable boundary based on the nonlinear thermal loss coefficient, and compare the current mechanical degradation characterization quantity with the preset mechanical degradation allowable boundary for compliance. The current thermal potential value is detected. If the current thermal potential value is lower than the restart thermal potential allowable boundary and the current mechanical degradation characterization quantity meets the mechanical degradation allowable boundary, the restart lockout is released and the reclosing operation is driven. Otherwise, the restart lockout is maintained.

10. A dynamic interlocking system for motor overload protection based on transient current fingerprinting, comprising a processor for performing the method as described in any one of claims 1 to 9.

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