A method for preventing insulation failure of a generator winding based on electrostatic coating

Abstract

The present application belongs to the technical field of generator, and provides a generator winding insulation failure prevention method based on coating electrostatic spraying, which can accurately simulate the accelerated aging and failure of the generator stator winding under the condition of thermal-mechanical coupling load. And according to the experimental device, an improved coating electrostatic spraying process is proposed to effectively improve the insulation damage of the stator winding. Finally, through the analysis of the insulation performance of the stator winding, the effectiveness of the improved process is proved. It is conducive to studying the influence of mechanical load, thermal load and coupling load on the insulation response and the stator insulation aging condition and performance change trend through experimental simulation, and provides a solid foundation for effectively preventing the shutdown failure of the generator winding insulation due to wear.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of generators, and particularly relates to a generator winding insulation failure prevention method based on coating electrostatic spraying. BACKGROUND

[0002] Stator winding insulation is one of the main components of the overall insulation of the motor, and a schematic diagram is as shown in Figure One , which is an important factor for evaluating the service life and reliability of the motor. When the motor operates in a harsh environment, the main insulation part of the motor is exposed to high temperature, electromagnetic field, vibration and chemical environment for a long time, is subjected to the combined action of the above factors, and is accelerated to be aged or damaged, so that the insulation resistance is high-voltage breakdown, and finally the motor is retired. There are many factors affecting insulation aging, and the aging process is complex. The failure process mainly bears two kinds of loads: one is thermal stress in a continuous high temperature environment, and the other is mechanical stress generated by motor vibration.

[0003] In engineering practice, the stator insulation damage of the generator often exists, and has the characteristics of high risk and high repair difficulty, but the mechanism and prevention of accelerated aging of the stator winding insulation are unknown, and the reason is that there is no effective simulation method and device and method for effectively improving the wear resistance of insulation and prolonging the service life.

[0004] Therefore, the research and technical personnel in the field urgently need to improve the insulation damage and aging of the stator winding based on the coating electrostatic spraying technology, so as to prevent the insulation failure of the generator winding. SUMMARY

[0005] To solve the above technical problems, the application provides a generator winding insulation failure prevention method based on coating electrostatic spraying, to solve the problems in the prior art, and the technical scheme adopted by the application is:

[0006] A generator winding insulation failure prevention method based on coating electrostatic spraying, comprising the following steps:

[0007] Step 1: Build a stator winding insulation accelerated aging experiment platform under the action of thermal-mechanical load coupling, and determine the easy-wear position of the stator winding;

[0008] Step 2: Test and analyze the insulation performance of the stator winding after the accelerated aging experiment, including mechanical performance and dielectric performance;

[0009] Step 3: Based on the accelerated aging experiment of step 1 and the test analysis of step 2, the wear-resistant coating is adsorbed on the easy-wear position of the stator winding through the electrostatic spraying technology;

[0010] Step four: the sprayed stator winding is subjected to the aging acceleration experiment of step one under the same conditions, and after the experiment, the mechanical properties and dielectric properties of the winding are tested to compare the mechanical properties and dielectric properties of the experimental group and the control group.

[0011] Further, in step one, the stator winding insulation acceleration aging experiment platform comprises a fixing frame, a strain gauge, a vibration exciter, a silica gel heating pad, a data acquisition instrument, an acceleration sensor, a power amplifier and a sweep signal generator.

[0012] The straight sections of the stator winding are fixed on the fixing frame, the vibration exciter and the silica gel heating pad are used to apply mechanical load and thermal load to the winding respectively, the electromagnetic force and temperature rise of the stator winding in the actual working condition are simulated, and the acceleration sensor is used to measure the vibration data; the strain gauge is used to measure the strain of different parts of the end winding under different loads; the sweep signal generator generates a sine signal which is amplified by the power amplifier and input into the vibration exciter, so that the vibration exciter generates a sine excitation force to simulate the mechanical load of the winding in the actual operation; the acceleration sensor and the strain gauge are connected with the data acquisition instrument.

[0013] Further, the two straight sections of the stator winding are evenly divided into four sections, each section is wrapped with a silica gel heating pad to realize heating at the position, and different temperatures are applied to simulate the differential temperature distribution.

[0014] Further, two acceleration sensors are installed at the middle position of the involute of the stator winding for measuring the vibration of the end winding under the action of mechanical load and coupled load; strain gauges are fixed at the connection between the straight section and the involute of the stator winding, the middle section of the involute and the position near the nose, for measuring the strain of different parts of the end winding under the action of different loads.

[0015] Further, step two comprises: the straight section and the end connection of the stator winding have the maximum stress and are most affected by mechanical-thermal load, and this position is the easy-wear position of the stator winding insulation.

[0016] For the measurement of the mechanical properties of the stator winding insulation, the elastic modulus is used for quantitative characterization; when measuring the elastic modulus, the tensile experiment is carried out by using a microcomputer-controlled electronic universal testing machine according to the standard of ASTM D638, the tensile rate is set to 1.5 mm / min, and the elastic modulus is obtained by fitting the stress-strain curve.

[0017] For the measurement of the electrical properties of the stator winding insulation, the dielectric constant and volume resistivity are used for quantitative measurement.

[0018] Furthermore, step three includes: an air pump generates compressed air to power powder delivery and spraying; an electrostatic generator generates high-voltage static electricity, which is transmitted to the powder spray gun via a high-voltage cable, enabling the spray gun to generate static electricity; ETFE / POM powder coating is fed into the powder spray gun and forms a mist-like jet stream under the impetus of compressed air; at the same time, the powder is charged by the electrostatic generator at the spray gun, becoming charged powder particles; the charged powder particles are sprayed onto easily worn surfaces under the combined action of compressed air and electrostatic attraction.

[0019] Further, step four includes: simulating mechanical load by inputting a sinusoidal signal to the exciter and simulating thermal load by using a silicone heating pad; constructing an accelerated aging test platform for stator winding insulation under thermomechanical coupling to determine the wear-prone locations of the stator winding; analyzing the insulation performance of the stator winding after the experiment, measuring the elastic modulus to characterize the mechanical properties of the insulation, and measuring the dielectric constant and volume resistivity to characterize the dielectric properties of the insulation; adjusting the spraying voltage of the electrostatic generator, dispersing and atomizing the coating through a powder spray gun, and spraying the wear-prone locations; subsequently placing the sprayed winding into a curing oven for curing, and allowing it to cool naturally to room temperature inside the oven after curing; conducting an accelerated aging test on the sprayed winding under the same conditions, and testing its mechanical and dielectric properties after the experiment, comparing and analyzing them with the mechanical and dielectric properties of the unsprayed winding.

[0020] An insulation aging assessment method includes: constructing an insulation aging assessment model to describe the correlation between the degree of insulation aging of a generator stator winding and its elastic modulus and dielectric constant; the model input includes the measured elastic modulus, dielectric constant, and environmental operating condition parameters of the insulation material; the model output is an insulation aging degree index and its corresponding remaining life estimate, used to reflect the intrinsic mapping relationship between the decrease in elastic modulus, the increase in dielectric constant, and the acceleration of insulation aging; the steps are as follows:

[0021] First, the input data is normalized and features are extracted to establish a coupled feature matrix of dielectric response and mechanical properties changing over time.

[0022] ;

[0023] ;

[0024] in, X For coupling feature matrix / vector, To normalize the elastic modulus, The normalized permittivity, T ( t () represents the temperature influence factor. H ( t ( ) represents the humidity influencing factor. E f (t ) is the electric field strength influence factor, E 0 and ε 0 represent the corresponding initial reference values, E t ) and ε t represent the measured values at time t;

[0025] The degree of insulation aging is then defined as a function of the degradation of dielectric properties and mechanical modulus by solving the multi-parameter fitting and state equation:

[0026] ;

[0027] ;

[0028] A ( is the aging index, t is the matrix representation of the degradation rate, θ E is the elastic modulus degradation rate, k ε is the dielectric constant degradation rate, k is the elastic modulus weight coefficient, α is the dielectric constant weight coefficient; β The Arrhenius-based acceleration mechanism and Levenberg-Marquardt are used to estimate the evolution rate of insulation damage in real time:

[0029]

[0030] ;

[0031] ; λ and γ represent the learning rate coefficient and damping factor, respectively; I represents the unit matrix,

[0032] represents the model prediction aging index;

[0033] The dynamic update and prediction of the aging state are realized through Bayesian filtering:

[0034] ;

[0035] ​​​In the formula, A(t) represents an insulation aging index at time t; X(t) represents a coupling characteristic matrix at the same time, including a normalized elastic modulus, a normalized dielectric constant, and environmental working condition parameters such as temperature, humidity, and electric field strength; p(A(t)X(t)) is a posterior probability distribution of the state A(t) after the current coupling characteristic X(t) is observed, reflecting the uncertainty of the current aging degree; p(X(t)A(t)) is an observation model, indicating the possibility of the coupling characteristic X(t) appearing when the aging state A(t) is given, and is used to map the observation information to the state space; p(A(t-1)|X(t-1)) is a prior probability distribution, indicating the estimation of the state at the last time under the condition of the previous observation; the formula recursively updates the aging state by combining the prior and the observation, so that the insulation aging index A(t) can dynamically reflect the degradation evolution process of the insulation material under the action of thermal-electric-humid-force multi-fields over time, and simultaneously provide real-time input for residual life prediction.

[0036] An evaluation model of insulation aging, comprising: constructing an insulation aging evaluation model according to the winding insulation performance test result of step two, describing the correlation between the insulation aging degree of the generator stator winding and the elastic modulus and the dielectric constant thereof, and the model input comprising the measured elastic modulus, dielectric constant and environmental working condition parameters of the insulation material, and being expressed as:

[0037] ;

[0038] Among them, δ represents an insulation aging degree index, E and ε respectively represent the measured elastic modulus and the dielectric constant, E 0 and ε 0 represent the corresponding initial reference values, T is the temperature, f ( T ) is a temperature acceleration factor function, K , m , n are parameters determined by fitting experimental data; the formula is used to quantitatively reflect the synergistic effect of the decrease of the elastic modulus and the increase of the dielectric constant on the insulation aging degree.

[0039] The present application has the following beneficial effects:

[0040] The application can accurately simulate the accelerated aging and failure of the stator winding of the generator under the condition of thermal-mechanical coupling load; and an improved coating electrostatic spraying process for effectively improving the insulation damage of the stator winding is proposed according to the experimental device; finally, the effectiveness of the improved process is proved through the analysis of the insulation performance of the stator winding; which is conducive to studying the influence of mechanical load, thermal load and coupling load on the insulation response and the aging condition and performance change trend of the stator insulation through experimental simulation, and provides a solid foundation for effectively preventing the shutdown failure of the generator winding insulation due to wear. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is a schematic diagram of the stator winding;

[0042] Figure 2 is an accelerated aging experimental platform for the insulation of the stator winding;

[0043] Figure 3 is a spraying process;

[0044] Figure 4 is a general flowchart. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings. Figures 1-4 The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings.

[0046] A generator winding insulation failure prevention method based on coating electrostatic spraying, comprising the following steps:

[0047] Step one, build an accelerated aging experimental platform for the insulation of the stator winding under the action of thermal-mechanical load coupling, and determine the easy-wear position of the stator winding:

[0048] To determine the easy-wear position of the stator winding and explore the insulation aging condition and performance change trend of the stator winding in the actual operating condition, an accelerated aging experimental platform for the insulation of the stator winding under the action of thermal-mechanical load coupling is built, and the overall structure is as shown in Figure 2 The experimental platform includes a fixing frame, a vibration exciter, a silica gel heating pad, a data acquisition instrument, an acceleration sensor, a power amplifier and a sweep signal generator and the like.

[0049] The straight line segment of the winding is fixed on the fixing frame, the vibration exciter and the silica gel heating pad are used to apply mechanical load and thermal load to the winding respectively, the electromagnetic force and temperature rise of the stator winding in the actual operating condition are simulated, and the vibration acceleration, strain and other data of the winding are measured by the acceleration sensor.

[0050] The straight section of the stator winding is evenly divided into 4 sections, each of which is wrapped with a silica gel heating pad to heat the position, a total of 8 silica gel heating pads, by applying different temperatures to simulate different temperature distributions, further wrapping the outside of the insulation straight section with a layer of aerogel cloth to achieve the effect of heat preservation, and finally the winding straight section is tightly fixed on the fixing frame by the clamp to prevent the winding from moving, simulating the fixed condition of the winding in the stator core. In addition, a high-power exciter is placed at the bottom of the winding nose, and the exciter is connected with the power amplifier. The sweep signal generator generates a sine signal which is amplified by the power amplifier and input into the exciter, so that the exciter generates a sine excitation force to simulate the mechanical load of the winding in the actual running condition.

[0051] In addition, two acceleration sensors are installed at the middle position of the end winding involute, for measuring the vibration of the end winding under the action of mechanical load and coupling load. At the same time, strain gauges are fixed at the connection between the straight section and the involute, the middle of the involute and the nose end, for measuring the strain of different parts of the end winding under the action of different loads. In addition, thermocouples are installed on the insulation surface of the stator winding for temperature monitoring to prevent abnormal temperature of the insulation surface. The acceleration sensor and strain gauge are connected with a 20-channel DH5922D dynamic signal test analyzer, and the final data is transmitted and saved to the computer.

[0052] In order to study the influence of mechanical load, thermal load and coupling load on the insulation response, different amplitude and frequency of excitation force and different temperature distribution of the difference load input are set in the experiment.

[0053] Step two, test and analyze the insulation performance of the stator winding after accelerated aging experiment, including mechanical performance and dielectric performance:

[0054] During the operation of the permanent magnet generator, the stator winding is subjected to the action of thermal stress, mechanical vibration and other factors, and the multi-stress synergistic effect causes the continuous deterioration of the winding insulation, and the irreversible reduction of the mechanical performance and dielectric performance of the insulation. In order to analyze the influence of thermal-mechanical load on the insulation performance of the stator winding of the permanent magnet generator during operation, based on this, the insulation performance after accelerated aging experiment needs to be tested and analyzed, including mechanical performance and dielectric performance, to study the influence of temperature, excitation force amplitude and frequency on the mechanical performance and electrical performance of the insulation of the permanent magnet stator winding.

[0055] Through the analysis of the thermal-mechanical wear test results of the above winding, the stress of the straight part and the end connection of the winding is the largest, and the mechanical-thermal load is the most serious, which is the most vulnerable part of the stator winding insulation during the operation of the generator. In order to take samples conveniently, the straight section near the end of the connection is selected as the test sample after accelerated aging. The sample is further processed according to the test requirements.

[0056] In terms of mechanical performance measurement of winding insulation, elastic modulus is the core parameter of mechanical performance of insulation mica tape, which can directly reflect the stiffness and deformation resistance of the material under the action of thermal-mechanical stress coupling. Therefore, the elastic modulus can quantitatively characterize the ability of the insulation material to resist mechanical deformation and reveal the accelerated degradation effect of thermal vibration on mechanical performance. When measuring the elastic modulus of the insulation, the standard of ASTM D638 is referred to, the tensile experiment is carried out by using the microcomputer control electronic universal testing machine, the tensile rate is set to 1.5mm / min, and the elastic modulus is obtained by stress-strain curve fitting.

[0057] In terms of electrical performance measurement of winding insulation, the dielectric constant depends on the dipole moment of the sample under external electric field, which determines the response ability of the sample to external electric field, and the volume resistivity is a key index for measuring the current leakage resistance of winding insulation. The size of the two parameters is directly related to the electrical performance of the winding insulation, which is very important to ensure the safe and stable operation of the winding. The dielectric constant is measured by the dielectric constant measuring instrument of the new energy power system national key laboratory, the test voltage is 140V, and the frequency is 0.001~1000Hz. The volume resistivity is measured according to the standard of GB / T 1410-2006. The electrochemical workstation is selected as the test equipment for measuring the volume resistivity, and the test temperature is selected as 60 degrees Celsius according to the actual operating temperature of the permanent magnet generator.

[0058] The application also provides an evaluation method for insulation aging, which is characterized by constructing an insulation aging evaluation model according to the test results of the winding insulation performance (step one, step two) to describe the correlation between the insulation aging degree of the generator stator winding and the elastic modulus and the dielectric constant thereof. The model input includes the measured elastic modulus, dielectric constant and environmental working condition parameters (temperature, humidity, electric field intensity, etc.) of the insulation material, and the specific steps are as follows:

[0059] Firstly, the input data is normalized and feature extracted to establish a coupling feature matrix of dielectric response and mechanical performance changing with time;

[0060] ;

[0061] ;

[0062] Among them,X is the coupling characteristic matrix / vector, is the normalized elastic modulus (mechanical degradation index), is the normalized dielectric constant (electrical degradation index), T t is the temperature influence factor, H t is the humidity influence factor, E f t is the electric field intensity influence factor, E 0 and ε 0 represent the corresponding initial reference values, E t and ε t represent the measured values at time t.

[0063] Subsequently, the insulation aging degree is defined as a function of dielectric properties and modulus degradation by multi-parameter fitting and state equation solving:

[0064]

[0065]

[0066] A t is the aging index, θ is the matrix representation of the degradation rate, k E is the elastic modulus degradation rate, k ε is the dielectric constant degradation rate, α is the elastic modulus weight coefficient, β is the dielectric constant weight coefficient.

[0067] The insulation damage evolution rate is estimated in real time based on the Arrhenius acceleration mechanism and Levenberg–Marquardt:

[0068]

[0069]

[0070] λ and γ represent the learning rate coefficient and the damping factor, respectively, and their numerical values can be set according to actual conditions; I represents the unit matrix, represents the model prediction of the aging index, which is obtained by extrapolation from the current current parameters θ t .

[0071] The dynamic update and prediction of the aging state are realized through Bayesian filtering:​​​​​​​​​​​​

[0072] ;

[0073] In the formula, A(t) represents an insulation aging index at time t, which is a state quantity to be estimated; X(t) represents a coupling characteristic matrix at the same time, including a normalized elastic modulus, a normalized dielectric constant, and environmental working condition parameters such as temperature, humidity, and electric field strength; p(A(t)X(t)) is a posterior probability distribution of the state A(t) after the current coupling characteristic X(t) is observed, reflecting the uncertainty of the current aging degree; p(X(t)A(t)) is an observation model, indicating the possibility of the coupling characteristic X(t) appearing when the aging state A(t) is given, and is used to map the observation information to the state space; p(A(t-1)|X(t-1)) is a prior probability distribution, indicating the estimation of the state at the last time under the condition of the previous observation; the formula recursively updates the aging state by combining the prior and the observation, so that the insulation aging index A(t) can dynamically reflect the degradation evolution process of the insulation material under the action of thermal-electric-humid-force multi-fields, and provide real-time input for residual life prediction.

[0074] The output is an insulation aging degree index and its corresponding residual life estimation, which can reflect the internal mapping relationship between the decrease of the elastic modulus, the increase of the dielectric constant, and the aggravation of the insulation aging.

[0075] In addition to the above-mentioned insulation aging evaluation method, the application also proposes another simple model for evaluating the insulation aging degree, specifically: an insulation aging evaluation model, according to the above winding insulation performance test results, an insulation aging evaluation model is constructed to describe the correlation between the insulation aging degree of the generator stator winding and its elastic modulus and dielectric constant, the model input includes the measured elastic modulus, dielectric constant and environmental working condition parameters (temperature, humidity, electric field strength, etc.) of the insulation material, which can be expressed as:

[0076] ;

[0077] Among them, δ represents an insulation aging degree index, E and ε represent the measured elastic modulus and dielectric constant, respectively, E 0 and ε 0 represent the corresponding initial reference values, T is the temperature, f ( T ) is a temperature acceleration factor function, K , m , n are parameters determined by fitting experimental data. The formula can quantitatively reflect the synergistic effect of the decrease of the elastic modulus and the increase of the dielectric constant on the insulation aging degree.

[0078] Step three, based on the accelerated aging test of step one and the test analysis of step two, the wear-resistant coating is adsorbed on the easy-wearing position of the stator winding through electrostatic spraying technology:

[0079] Through the thermal-mechanical load coupling accelerated aging test of step one, under the action of thermal-mechanical coupling, the multi-load interaction effect borne by the winding is not a simple algebraic superposition, but there is a thermal-mechanical load interaction inhibition mechanism, and the stress fluctuation is mainly driven by mechanical load; with the increase of the excitation force amplitude, frequency and environmental temperature, the response parameters such as the structural deformation of the winding insulation and the stress value all show a significant increasing trend. Further, through regression analysis of the data obtained by the thermal-mechanical coupling accelerated aging test, a quantitative relationship between the excitation force, temperature and insulation aging degree can be established by using a multivariate nonlinear regression method, and the excitation force amplitude, frequency and environmental temperature are selected as independent variables, and the insulation aging degree is selected as dependent variable.

[0080] It is further proved by the insulation performance test results of step two that high temperature environment will cause the resin material inside the winding insulation to deteriorate, and the cyclic mechanical load will cause insulation delamination, cracking and other defects, and under the double action, the stator winding insulation aging process is accelerated, and the mechanical properties and dielectric properties are irreversibly attenuated, which eventually leads to the failure of the generator due to the wear of the winding insulation. The easy-wearing position of the stator winding insulation, the winding nose, is the key weak point of insulation failure.

[0081] In order to solve the above-mentioned aging and wear problem of the winding easy-wearing position (nose) under the coupling load and avoid the decline of the mechanical properties and dielectric properties, the application provides a targeted insulation failure prevention method based on coating electrostatic spraying, and the core innovation is that: based on the accurate determination of the easy-wearing position of the winding insulation (winding nose) in the foregoing experiment, the wear-resistant coating is adsorbed on the easy-wearing position through electrostatic spraying technology, the insulation of the nose is directionally reinforced, so as to slow down the insulation aging rate, reduce the wear degree and prolong the service life of the winding.

[0082] The electrostatic spraying is used to spray coating on the nose part of the stator winding in the application, the coating should have strong high-temperature resistance, excellent electrical insulation, strong wear resistance and mechanical properties, and chemical resistance, and the cost of the material should be as low as possible and have certain processing convenience. For example, ethylene-tetrafluoroethylene copolymer (ETFE) and polyoxymethylene (POM) materials. The spraying process is as follows Figure 3The core of the electrostatic spraying device includes an electrostatic generator, a powder spraying gun, and a gas pump. Before the experiment, the spraying voltage of the electrostatic generator is adjusted according to the material properties of ETFE and POM and the shape of the stator winding insulation, and the powder gas pressure parameters are adjusted to make the powder particles charged and the charge density optimal. Then the wear-resistant coating is dispersed and atomized by the powder spraying gun, and the powder is uniformly adsorbed to the grounded winding insulation. In particular, the adsorbed coating forms a coating with a thickness of 0.05mm. Next, the sprayed ETFE and POM winding is placed in a curing oven for curing, and after curing, the curing oven is turned off and the winding is naturally cooled to room temperature in the oven.

[0083] Step four, the sprayed stator winding is subjected to the aging acceleration experiment of step one under the same conditions, and after the experiment, the mechanical properties and dielectric properties of the winding are tested, and the mechanical properties and dielectric properties of the experimental group and the control group are compared:

[0084] In order to study the effect of electrostatic spraying on the insulation performance of the winding, the sprayed winding is subjected to an aging acceleration experiment under the same conditions as the control group. After the experiment, the mechanical properties and dielectric properties of the winding are tested. By comparing the mechanical properties and dielectric properties of the experimental group and the control group, the effectiveness of the invention in preventing generator winding insulation is proved. The overall flowchart is as follows Figure 4 .

[0085] The method is simple and easy to operate, and has high efficiency, which can effectively prevent the shutdown failure of the generator winding insulation due to wear. At the same time, the utilization rate of the coating can be as high as 95%-99%, which is easy to realize automatic production and greatly reduces the production cost.

[0086] The above embodiments only describe the preferred mode of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications, variations, modifications, and replacements of the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for preventing generator winding insulation failure based on electrostatic spraying of a coating, characterized in that, Includes the following steps: Step 1: Construct an experimental platform for accelerated aging of stator winding insulation under thermo-mechanical load coupling to determine the wear-prone locations of the stator winding; Step 2: Test and analyze the insulation performance of the stator winding after accelerated aging test, including mechanical and dielectric properties; Step 3: Based on the accelerated aging experiment in Step 1 and the test analysis in Step 2, wear-resistant coating is applied to the wear-prone areas of the stator winding using electrostatic spraying technology. Step 4: The sprayed stator windings are subjected to the accelerated aging test of Step 1 under the same conditions. After the test, the mechanical and dielectric properties of the windings are tested, and the mechanical and dielectric properties of the experimental group and the control group are compared. In step one, the stator winding insulation accelerated aging test platform includes: a fixing frame, strain gauges, an exciter, a silicone heating pad, a data acquisition instrument, an accelerometer, a power amplifier, and a sweep frequency signal generator; The straight section of the stator winding is fixed on a mounting frame. Mechanical and thermal loads are applied to the winding using a vibrator and a silicone heating pad, respectively, to simulate the electromagnetic force and temperature rise experienced by the stator winding under actual operating conditions. Vibration data is measured using an accelerometer. Strain gauges are used to measure the strain at different locations of the end winding under different loads. A sweep frequency generator produces a sinusoidal signal, which is amplified by a power amplifier and then input to the vibrator, causing the vibrator to generate a sinusoidal excitation force to simulate the mechanical load experienced by the winding under actual operating conditions. The accelerometer and strain gauges are connected to a data acquisition instrument. Step three includes: an air pump generates compressed air to power powder delivery and spraying; an electrostatic generator generates high-voltage static electricity, which is transmitted to the powder spray gun via a high-voltage cable, enabling the spray gun to generate static electricity; ETFE / POM powder coating is fed into the powder spray gun and forms a mist-like jet stream under the propulsion of compressed air; at the same time, the powder is charged by the electrostatic generator at the spray gun, becoming charged powder particles; the charged powder particles are sprayed onto easily worn surfaces under the combined action of compressed air and electrostatic attraction. Step four includes: simulating mechanical loads by inputting a sinusoidal signal to the exciter and simulating thermal loads by using a silicone heating pad; constructing an accelerated aging test platform for stator winding insulation under thermomechanical coupling to determine the wear-prone areas of the stator winding; analyzing the insulation performance of the stator winding after the experiment, measuring the elastic modulus to characterize the mechanical properties of the insulation, and measuring the dielectric constant and volume resistivity to characterize the dielectric properties of the insulation; adjusting the spraying voltage of the electrostatic generator, dispersing and atomizing the coating through a powder spray gun, and spraying the wear-prone areas; subsequently, placing the sprayed winding in a curing oven for curing, and allowing it to cool naturally to room temperature inside the oven after curing; conducting an accelerated aging test on the sprayed winding under the same conditions, and testing its mechanical and dielectric properties after the experiment, comparing and analyzing them with those of the unsprayed winding.

2. The generator winding insulation failure prevention method based on electrostatic spraying of coating according to claim 1, characterized in that, The two straight segments of the stator winding are each evenly divided into four segments, and each segment is wrapped with a silicone heating pad to achieve heating. Different temperatures are applied to simulate differential temperature distribution.

3. The generator winding insulation failure prevention method based on electrostatic spraying of coating according to claim 1, characterized in that, Two accelerometers are installed at the middle position of the involute of the stator winding to measure the vibration of the end winding under mechanical and coupled loads. Strain gauges are fixed at the connection between the straight section and the involute of the stator winding, the middle section of the involute, and near the nose end to measure the strain of different parts of the end winding under different loads.

4. The generator winding insulation failure prevention method based on electrostatic spraying according to claim 1, characterized in that, Step two includes: the straight section and end connection of the stator winding have the greatest stress and are most severely affected by mechanical-thermal loads. This location is the most easily worn part of the stator winding insulation. For the measurement of the mechanical properties of stator winding insulation, the elastic modulus is used for quantitative characterization. When measuring the elastic modulus, the ASTM D638 standard is referred to, and a microcomputer-controlled electronic universal testing machine is used to carry out tensile tests. The tensile rate is set to 1.5 mm / min, and the elastic modulus is obtained by fitting the stress-strain curve. For the measurement of the electrical properties of stator winding insulation, quantitative measurements are performed using two aspects: dielectric constant and volume resistivity.

5. A method for assessing insulation aging, based on the generator winding insulation failure prevention method based on electrostatic spraying of a coating as described in any one of claims 1-4, characterized in that, include: An insulation aging assessment model is constructed to describe the correlation between the degree of insulation aging of generator stator windings and its elastic modulus and dielectric constant. The model inputs include the measured elastic modulus, dielectric constant, and environmental operating parameters of the insulation material. The model output is an insulation aging degree index and its corresponding remaining life estimate, used to reflect the intrinsic mapping relationship between the decrease in elastic modulus, the increase in dielectric constant, and the acceleration of insulation aging. The steps are as follows: First, the input data is normalized and features are extracted to establish a coupled feature matrix of dielectric response and mechanical properties changing over time. ； in, X For coupling feature matrix / vector, To normalize the elastic modulus, The normalized permittivity, T ( t ) represents the temperature influence factor. H ( t ( ) represents the humidity influencing factor. E f ( t ) represents the electric field strength influencing factor. E 0 and ε 0 represents the corresponding initial reference value. E ( t )and ε ( t () represents the measurement value at time t; Subsequently, through multi-parameter fitting and solving the state equation, the degree of insulation aging was defined as a function of dielectric properties and mechanical modulus degradation: ； A ( t () is the aging index. θ This is the matrix representation of the degradation rate. k E The rate of degradation of the elastic modulus. k ε The rate of degradation of dielectric constant, α This is the weighting coefficient for the elastic modulus. β The dielectric constant weighting coefficient; Real-time estimation of insulation damage evolution rate using the Arrhenius acceleration mechanism and Levenberg–Marquardt method: ； λ and γ represent the learning rate coefficient and damping factor, respectively; I represents the identity matrix. This indicates that the model predicts the aging index; And the dynamic updating and prediction of the aging state are achieved through Bayesian filtering: ； In the formula, A(t) represents the insulation aging index at time t; X(t) represents the coupling feature matrix at the same time, including the normalized elastic modulus, normalized dielectric constant, and environmental parameters such as temperature, humidity, and electric field strength; p(A(t)X(t)) is the posterior probability distribution of state A(t) after observing the current coupling feature X(t), reflecting the uncertainty of the current aging degree; p(X(t)A(t)) is the observation model, representing the probability of the coupling feature X(t) appearing given the aging state A(t), used to map the observation information to the state space; p(A(t-1)|X(t-1)) is the prior probability distribution, representing the estimate of the state at the previous time under the previous observation conditions; this formula recursively updates the aging state by combining prior and observation, so that the insulation aging index A(t) can dynamically reflect the degradation evolution process of the insulating material under the action of multiple fields of heat, electricity, humidity, and force over time, while providing real-time input for the prediction of remaining lifetime.

6. An insulation aging assessment model, based on the generator winding insulation failure prevention method based on electrostatic spraying of a coating as described in any one of claims 1-4, characterized in that, include: Based on the winding insulation performance test results from step two, an insulation aging assessment model is constructed to describe the correlation between the degree of aging of the generator stator winding insulation and its elastic modulus and dielectric constant. The model input includes the measured elastic modulus, dielectric constant, and environmental operating condition parameters of the insulation material, expressed as follows: ； in, δ Indices representing the degree of insulation aging E and ε These represent the measured elastic modulus and dielectric constant, respectively. E 0 and ε 0 represents the corresponding initial reference value. T For temperature, f ( T ) is the temperature acceleration factor function. K , m , n These are parameters determined through fitting experimental data; this formula is used to quantitatively reflect the synergistic effect of the decrease in elastic modulus and the increase in dielectric constant on the degree of insulation aging.

Images