Method for evaluating main insulation performance of stator coil of high-voltage variable frequency motor

Abstract

The invention relates to the technical field of motor performance detection, in particular to a method for evaluating the main insulation performance of a stator coil of a high-voltage variable-frequency motor. Comprising the following steps: selecting a plurality of stator coils in the same batch, and sequentially carrying out a first conventional insulation performance test, a plurality of alternating tests of high-frequency impact electrothermal aging tests and power-frequency alternating-current electrothermal aging tests, and a second conventional insulation performance test; dividing all the stator coils into a plurality of groups and carrying out power frequency alternating current electric heating aging life tests to obtain test result parameters; and based on the insulation voltage durability mathematical model of the high-voltage motor stator coil, introducing test result parameters to implement linear fitting to obtain an insulation performance evaluation formula which is used for carrying out insulation life expectancy evaluation on the stator coil when a high-voltage variable frequency motor product is designed. The technical scheme has the characteristics of simple flow and high applicability, the reasonability and feasibility of the main insulation structure design of the high-voltage variable-frequency stator coil can be effectively verified, and the insulation performance of the stator coil is improved.

Description

[0001] Technical Domain

[0002] The present invention relates to the field of motor performance detection technology, and in particular to a method for evaluating the main insulation performance of a stator coil of a high-voltage variable-frequency motor. Background Art

[0003] The electrical performance of the stator coil main insulation is one of the key indicators of high-voltage motor insulation design, and its reliability plays a vital role in the long-term safe and stable operation of the unit. Compared with industrial frequency high-voltage motors, the insulation of high-voltage variable-frequency motors needs to withstand the output voltage impact of the inverter containing a large number of high-frequency components. The frequency conversion parameters (impact rise time, sudden voltage and impulse voltage repetition rate, etc.) have a greater impact on the performance of the stator coil main insulation. The potential stress of the stator coil main insulation of the high-voltage variable-frequency motor during testing and operation is more concentrated, and the temperature rise loss is higher.

[0004] The performance evaluation methods for the main insulation of the stator coil of conventional high-voltage motors with industrial frequency are mainly voltage withstand test, electrothermal aging life test and electrical aging life test under industrial frequency voltage. The traditional evaluation methods under industrial frequency voltage cannot fully and truly reflect the main insulation performance of the stator coil of high-voltage variable-frequency motors under high-frequency parameters, and have great limitations. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and to propose a method for evaluating the main insulation performance of the stator coil of a high-voltage variable-frequency motor, as follows:

[0006] A method for evaluating the main insulation performance of a stator coil of a high-voltage variable-frequency motor comprises the following steps:

[0007] S1, select several stator coils from the same batch as test samples, and conduct the first conventional insulation performance test on all test samples;

[0008] S2, based on the set test condition parameters, all test samples are subjected to several alternating tests of high-frequency impact electrothermal aging test and power frequency AC electrothermal aging test;

[0009] S3, conduct secondary conventional insulation performance tests on all test samples;

[0010] S4, according to the relationship between the working field strength and insulation thickness of the high-voltage motor stator coil, based on different test setting parameters, all current test samples are divided into several groups for power frequency AC thermal aging life tests, and the test result parameters of each group of test samples are recorded;

[0011] S5, based on the mathematical model of insulation voltage durability of high-voltage motor stator coil, the test result parameters are introduced to perform linear fitting to obtain the insulation performance evaluation formula;

[0012] S6, based on the insulation performance evaluation formula, evaluate the expected insulation life of the stator coil when designing high-voltage variable-frequency motor products.

[0013] Preferably, in step S1 and step S3, conventional insulation performance tests include: insulation resistance test, using an insulation resistance tester to detect whether the stator coil insulation is damp and damaged; dielectric loss test, using a dielectric loss tester to detect the insulation curing state of the stator coil and the insulation density of the coil; partial discharge test, using a partial discharge tester to detect the insulation density of the stator coil; power frequency AC withstand voltage test, using a power frequency AC transformer test system to detect the electrical strength of the stator coil insulation; anti-corona test, using a power frequency AC transformer test system to detect the surface discharge of the high resistance anti-corona area at the end of the stator coil.

[0014] Preferably, in step S2, the test condition parameter settings of the high-frequency impact electrothermal aging test include: setting the test peak-to-peak voltage to the maximum sudden change voltage that the variable frequency motor withstands during operation multiplied by a safety factor of 2.0, the impact rise time is less than 2μs, the test frequency range is 8kHz to 20kHz, the test temperature is 120°C, and the test time is 100h.

[0015] Preferably, in step S2, the test condition parameter setting of the power frequency AC thermal aging test includes: setting the applied voltage value to be the maximum peak-to-peak value relative to ground voltage during the operation of the variable frequency motor multiplied by a safety factor of 1.5, and setting the equivalent voltage effective value to be the peak-to-peak value divided by The test temperature is 120℃ and the test time is 1000h.

[0016] Preferably, in step S4, the relationship between the working field strength and insulation thickness of the stator coil of the high-voltage motor is: Among them, E is the field strength that the stator coil insulation is subjected to, U is the applied test voltage; and d is the insulation thickness of the stator coil.

[0017] Preferably, in step S4, the power frequency AC thermal aging life test includes the following steps:

[0018] For each group of test samples, at the test temperature T i Under the condition of U i The test voltage is E, and the stator coil insulation thickness d remains unchanged. i ;

[0019] After the insulation of the test sample is broken down, record the breakdown time L;

[0020] For each individual group of test samples, take the median value L among the recorded breakdown times iAs the insulation life of the batch of test samples under the current test conditions;

[0021] Where i represents the test sample group number, T i represents the test temperature of the i-th group of test samples, E i Indicates the test field strength of the i-th group of test samples; U i Indicates the test voltage of the i-th group of test samples, L i Indicates the i-th group of test samples at the test temperature T i , Test field strength E i The median breakdown time under the conditions.

[0022] Preferably, in step S5, the mathematical model of the insulation voltage durability of the high-voltage motor stator coil is expressed as Among them, L s Indicates the insulation life of the stator coil, E s It represents the field strength of the stator coil, and C and n are constants affected by the test conditions.

[0023] Preferably, in step S5, the test result parameters are introduced into the high-voltage motor stator coil insulation voltage durability mathematical model to perform linear fitting under the condition that the natural logarithm of the test field intensity is used as the X-axis and the natural logarithm of the life time is used as the Y-axis, that is, the insulation performance evaluation formula is expressed as: Among them, e is a natural constant, which is the base of the natural logarithm; x represents the natural logarithm of the test field intensity, and y represents the natural logarithm of the life time.

[0024] Preferably, in step S6, the method for evaluating the expected insulation life of the stator coil is: for the stator coil with the same material, structure and manufacturing process as the test sample, the working field strength design value is obtained according to the factory design data of the high-voltage variable-frequency motor in which the stator coil is located; the working field strength design value is used as the field strength received by the stator coil into the insulation performance evaluation formula to obtain the insulation life L s That is the expected insulation life of the stator coil in the corresponding high-voltage variable-frequency motor.

[0025] Preferably, the natural logarithm x of the test field strength and the natural logarithm y of the life time are determined based on the operating characteristics of the high-voltage variable-frequency motor in which the stator coil is located and the insulation life requirements of the stator coil; wherein, 25≤x≤27, 8.05≤y≤8.52.

[0026] Beneficial technical effects brought by the present invention:

[0027] 1) Compared with the sinusoidal industrial frequency AC voltage applied in the main insulation performance test of the stator coil of a conventional high-voltage motor, the technical scheme proposes a method for evaluating the main insulation performance of the stator coil of a high-voltage variable frequency motor, which adds a high-frequency impact electrothermal aging test and adopts high-frequency parameters such as high-frequency pulse test voltage, impact rise time of the high-frequency pulse test voltage and impact voltage repetition rate, which can more strictly assess the electrical performance of the main insulation structure of the stator coil. Specifically: the high-frequency impact electrothermal aging test in the technical scheme uses a high-frequency pulse test power supply, and its frequency conversion parameters (impact rise time, sudden change voltage and impact voltage repetition rate, etc.) rapidly reduce the insulation capacitive reactance of the stator coil, and the rapidly increasing capacitive current can more accurately test the main insulation performance of the stator coil of the high-voltage variable frequency motor under high-frequency parameters. This evaluation method has the characteristics of simple process and strong applicability, and can effectively verify the rationality and feasibility of the design of the main insulation structure of the high-voltage variable frequency stator coil, and improve the insulation performance of the stator coil.

[0028] 2) This technical solution proposes a method for evaluating the main insulation performance of the stator coil of a high-voltage variable-frequency motor. It adopts the method of alternating high-frequency impact electrothermal aging test with industrial frequency AC electrothermal aging test. It can not only evaluate the insulation performance of the stator coil, but also further evaluate the anti-corona performance of the coil, and more comprehensively verify the design level of the main insulation structure and anti-corona structure of the stator coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the basic implementation flow chart of this technical solution. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0031] Therefore, the following detailed description of the invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the invention. Based on the embodiments of the invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the invention.

[0032] Example 1

[0033] This embodiment discloses a method for evaluating the main insulation performance of a stator coil of a high-voltage variable-frequency motor, as a preferred embodiment of the present invention. Figure 1 As shown, the following steps are included:

[0034] S1, select several stator coils from the same batch as test samples, and conduct the first routine insulation performance test on all test samples. The purpose is to ensure that the stator coils meet the basic insulation performance requirements and provide a comparison basis for subsequent tests.

[0035] S2, based on the set test condition parameters, all test samples are subjected to several alternating tests of high-frequency impact electrothermal aging test and power frequency AC electrothermal aging test. The purpose is to test the stator coil's resistance to high-frequency impact electrothermal aging and power frequency AC electrothermal aging.

[0036] S3, conduct secondary conventional insulation performance tests on all test samples. This step is implemented on the basis of step 2, and the test results can be compared with the test results of step S1. Only if the secondary conventional insulation performance test is passed, it indicates that the batch of test samples meets the requirements of the stator coil's resistance to high-frequency impact electrothermal aging performance and resistance to industrial frequency AC electrothermal aging performance.

[0037] The aforementioned steps S1 to S3 are preliminary preventive tests of the present technical solution, which ensure that the stator coil meets the basic performance requirements and prevent data deviations in subsequent tests.

[0038] S4, according to the relationship between the working field strength and insulation thickness of the high-voltage motor stator coil, based on different test setting parameters, all current test samples are divided into several groups for power frequency AC thermal aging life tests, and the test result parameters of each group of test samples are recorded.

[0039] S5, based on the mathematical model of insulation voltage durability of high-voltage motor stator coil, the test result parameters are introduced to perform linear fitting and obtain the insulation performance evaluation formula.

[0040] S6, based on the insulation performance evaluation formula, evaluate the expected insulation life of the stator coil when designing high-voltage variable-frequency motor products.

[0041] Example 2

[0042] This embodiment discloses a method for evaluating the main insulation performance of a stator coil of a high-voltage variable-frequency motor, which, as a preferred implementation scheme of the present invention, comprises the following steps:

[0043] S1, select several stator coils from the same batch as test samples, and conduct the first routine insulation performance test on all test samples. The first routine insulation performance test includes:

[0044] The insulation resistance test uses an insulation resistance tester to detect whether the stator coil insulation is damp or damaged. It is a preventive test before and after the high-voltage test.

[0045] Dielectric loss test: Use a dielectric loss tester to detect the insulation curing state of the stator coil and the insulation density of the coil.

[0046] Partial discharge test: Use a partial discharge tester to detect the insulation density of the stator coil (microscopically).

[0047] The power frequency AC withstand voltage test uses a power frequency AC transformer test system to detect the electrical strength of the stator coil insulation.

[0048] The anti-corona test uses a power frequency AC transformer test system to detect the surface discharge conditions in the high resistance anti-corona area at the end of the stator coil.

[0049] S2: Based on the set test condition parameters, all test samples are subjected to several alternating tests of high-frequency impact electrothermal aging test and power frequency AC electrothermal aging test.

[0050] S3, all test samples are subjected to secondary conventional insulation performance tests. Correspondingly, the secondary conventional insulation performance tests also include insulation resistance test, dielectric loss test, partial discharge test, power frequency AC withstand voltage test and corona protection test, which are all test items specified by conventional standards in this field.

[0051] S4, according to the relationship between the working field strength and insulation thickness of the high-voltage motor stator coil, based on different test setting parameters, all current test samples are divided into several groups for power frequency AC thermal aging life tests, and the test result parameters of each group of test samples are recorded.

[0052] S5, based on the mathematical model of insulation voltage durability of high-voltage motor stator coil, the test result parameters are introduced to perform linear fitting and obtain the insulation performance evaluation formula.

[0053] S6, based on the insulation performance evaluation formula, evaluate the expected insulation life of the stator coil when designing high-voltage variable-frequency motor products.

[0054] Example 3

[0055] This embodiment discloses a method for evaluating the main insulation performance of a stator coil of a high-voltage variable-frequency motor, which, as a preferred implementation scheme of the present invention, comprises the following steps:

[0056] S1, select several stator coils from the same batch as test samples, and conduct the first routine insulation performance test on all test samples.

[0057] S2: Based on the set test condition parameters, all test samples are subjected to several alternating tests of high-frequency impact electrothermal aging test and power frequency AC electrothermal aging test.

[0058] Among them, the purpose of the high-frequency impact electrothermal aging test is to detect whether the insulation / anti-corona performance of the stator coil can adapt to the high-frequency pulse related test parameters, to ensure the reliability of the stator coil insulation / anti-corona design and process manufacturing, and to conduct conventional insulation performance tests after the test for judgment. The high-frequency impact electrothermal aging test uses a high-frequency pulse generator and electric heating equipment. The test condition parameter settings involve: setting the test peak-to-peak voltage to the maximum sudden change voltage that the variable frequency motor withstands during operation multiplied by a safety factor of 2.0, the impact rise time is less than 2μs, the test frequency range is 8kHz to 20kHz, the test temperature is 120°C, and the test time is 100h. The above test condition parameters are set according to demand and can be adjusted according to actual conditions.

[0059] Furthermore, the power frequency AC electric thermal aging test used a power frequency aging test bench and electric heating equipment. The test condition parameter settings involved: setting the applied voltage value to the maximum peak-to-peak value relative to ground voltage during the operation of the variable frequency motor multiplied by a safety factor of 1.5, and setting the equivalent voltage effective value to the peak-to-peak value divided by The test temperature is 120℃ and the test time is 1000h.

[0060] S3, conduct secondary conventional insulation performance tests on all test samples.

[0061] S4, according to the relationship between the working field strength and insulation thickness of the high-voltage motor stator coil, based on different test setting parameters, all current test samples are divided into several groups for power frequency AC thermal aging life tests, and the test result parameters of each group of test samples are recorded.

[0062] S5, based on the mathematical model of insulation voltage durability of high-voltage motor stator coil, the test result parameters are introduced to perform linear fitting and obtain the insulation performance evaluation formula.

[0063] S6, based on the insulation performance evaluation formula, evaluate the expected insulation life of the stator coil when designing high-voltage variable-frequency motor products.

[0064] Example 4

[0065] This embodiment discloses a method for evaluating the main insulation performance of a stator coil of a high-voltage variable-frequency motor, which, as a preferred implementation scheme of the present invention, comprises the following steps:

[0066] S1, select several stator coils from the same batch as test samples, and conduct the first routine insulation performance test on all test samples.

[0067] S2: Based on the set test condition parameters, all test samples are subjected to several alternating tests of high-frequency impact electrothermal aging test and power frequency AC electrothermal aging test.

[0068] S3, conduct secondary conventional insulation performance tests on all test samples.

[0069] S4, according to the relationship between the working field strength and insulation thickness of the high-voltage motor stator coil, based on different test setting parameters, all current test samples are divided into several groups for power frequency AC thermal aging life tests, and the test result parameters of each group of test samples are recorded.

[0070] Among them, the relationship between the working field strength and insulation thickness of the high-voltage motor stator coil is: E is the field strength that the stator coil insulation is subjected to, U is the applied test voltage; d is the insulation thickness of the stator coil.

[0071] Therefore, the power frequency AC thermal aging life test includes the following steps:

[0072] For each group of test samples, at the test temperature T i Under the condition of applying U i The test voltage is E, and the stator coil insulation thickness d remains unchanged. i ;

[0073] After the insulation of the test sample is broken down, record the breakdown time L;

[0074] For each individual group of test samples, take the median value L among the recorded breakdown times i As the insulation life of the batch of test samples under the current test conditions;

[0075] Where i represents the test sample group number, T i represents the test temperature of the i-th group of test samples, E i Indicates the test field strength of the i-th group of test samples; U i Indicates the test voltage of the i-th group of test samples, L i Indicates the i-th group of test samples at the test temperature T i , Test field strength E i The median breakdown time under the conditions.

[0076] S5, based on the mathematical model of insulation voltage durability of high-voltage motor stator coil, the test result parameters are introduced to perform linear fitting and obtain the insulation performance evaluation formula.

[0077] S6, based on the insulation performance evaluation formula, evaluate the expected insulation life of the stator coil when designing high-voltage variable-frequency motor products.

[0078] Example 5

[0079] This embodiment discloses a method for evaluating the main insulation performance of a stator coil of a high-voltage variable-frequency motor, which, as a preferred implementation scheme of the present invention, comprises the following steps:

[0080] S1, select several stator coils from the same batch as test samples, and conduct the first routine insulation performance test on all test samples.

[0081] S2: Based on the set test condition parameters, all test samples are subjected to several alternating tests of high-frequency impact electrothermal aging test and power frequency AC electrothermal aging test.

[0082] S3, conduct secondary conventional insulation performance tests on all test samples.

[0083] S4, according to the relationship between the working field strength and insulation thickness of the high-voltage motor stator coil, based on different test setting parameters, all current test samples are divided into several groups for power frequency AC thermal aging life tests, and the test result parameters of each group of test samples are recorded.

[0084] S5, based on the mathematical model of high-voltage motor stator coil insulation voltage durability Substitute the test result parameters into the linear fitting to obtain the insulation performance evaluation formula; where L s Indicates the insulation life of the stator coil, E s It represents the field strength of the stator coil, and c and n are constants affected by the test conditions.

[0085] Furthermore, under the condition that the natural logarithm of the test field intensity is the X-axis and the natural logarithm of the life time is the Y-axis, the test result parameters are introduced into the high-voltage motor stator coil insulation voltage durability mathematical model to perform linear fitting, that is, the insulation performance evaluation formula is expressed as Among them, e is a natural constant, which is the base of the natural logarithm; x represents the natural logarithm of the test field intensity, and y represents the natural logarithm of the life time.

[0086] Furthermore, the natural logarithm x of the test field strength and the natural logarithm y of the life time are determined based on the operating characteristics of the high-voltage variable-frequency motor in which the stator coil is located and the insulation life requirements of the stator coil; wherein, 25≤x≤27, 8.05≤y≤8.52.

[0087] S6, based on the insulation performance evaluation formula, the expected insulation life of the stator coil of the high-voltage variable-frequency motor product design is evaluated. Specifically: for the stator coil with the same material, structure and manufacturing process as the test sample, the working field strength design value is obtained according to the factory design data of the high-voltage variable-frequency motor in which it is located; the working field strength design value is used as the field strength received by the stator coil into the insulation performance evaluation formula to obtain the insulation life L s That is the expected insulation life of the stator coil in the corresponding high-voltage variable-frequency motor.

[0088] Example 6

[0089] This embodiment discloses a method for evaluating the main insulation performance of a stator coil of a high-voltage variable-frequency motor, which, as a preferred implementation scheme of the present invention, comprises the following steps:

[0090] S1, select 12 stator coils from the same batch as test samples, and conduct the first routine insulation performance test on all test samples, including insulation resistance test, dielectric loss test, partial discharge test, power frequency AC withstand voltage test and corona protection test.

[0091] S2, based on the set test condition parameters, all test samples are subjected to several alternating tests of high-frequency impact electrothermal aging test and power frequency AC electrothermal aging test. The specific number of alternating tests is set according to actual needs. For example, two alternating tests can be set. Specifically:

[0092] S21, the first high-frequency impact electrothermal aging test was carried out on 12 test samples using a high-frequency pulse generator and an electric heating equipment. The test condition parameter settings involved include: setting the test peak-to-peak voltage to the maximum sudden voltage that the variable frequency motor can withstand during operation multiplied by a safety factor of 2.0, the impact rise time is less than 2μs, the test frequency range is 8kHz to 20kHz, the test temperature is 120℃, and the test time is 100h.

[0093] S22, the first power frequency AC electric thermal aging test was carried out on 12 test samples using a power frequency aging test bench and electric heating equipment. The test condition parameter settings involved included: setting the applied voltage value to the maximum peak-to-peak relative ground voltage during the operation of the variable frequency motor multiplied by a safety factor of 1.5, and setting the equivalent voltage effective value to the peak-to-peak value divided by The test temperature is 120℃ and the test time is 1000h.

[0094] S23, based on the test condition parameter setting of step S21, a second high-frequency impact electrothermal aging test is performed on the 12 test samples.

[0095] S24, based on the test condition parameter setting of step S22, a second power frequency AC electric thermal aging test is performed on the 12 test samples.

[0096] S3, all test samples are subjected to secondary conventional insulation performance tests, insulation resistance test, dielectric loss test, partial discharge test, power frequency AC withstand voltage test and corona protection test.

[0097] S4, according to the relationship between the working field strength and insulation thickness of the high-voltage motor stator coil Based on different test setting parameters, all current test samples are divided into several groups for power frequency AC thermal aging life test, and the test result parameters of each group of test samples are recorded. Among them, E is the field strength borne by the stator coil insulation, U is the applied test voltage; d is the insulation thickness of the stator coil, and for the same model of stator coil, the insulation thickness is a fixed value.

[0098] The AC power frequency thermal aging life test includes the following steps: for each group of test samples, at the test temperature T i Under the condition of applying U i The test voltage is E, and the stator coil insulation thickness d remains unchanged. i ; After the test sample is insulated and broken down, record its breakdown time L; for each group of test samples, take the median value L of the recorded breakdown time i As the insulation life of the batch of test samples under the current test conditions. Where i represents the test sample group number, T i represents the test temperature of the i-th group of test samples, E i Indicates the test field strength of the i-th group of test samples; U i Indicates the test voltage of the i-th group of test samples, L i Indicates the i-th group of test samples at the test temperature T i , Test field strength E i The median breakdown time under the conditions.

[0099] In this technical solution, the 12 test samples can be divided into 4 groups, each group has 3 stator coil test samples. Based on this, the power frequency AC thermal aging life test is as follows:

[0100] S41, use the industrial frequency AC transformer test system to conduct industrial frequency AC thermal aging life tests on the three test samples in the first group at the test temperature T1, during which the test voltage U1 is applied, and the corresponding test field strength is E1; after the three test samples are all broken down, the breakdown time of the three test samples is recorded respectively, and the median value L1 of the three breakdown time data is taken as the insulation life of the first group of test samples at the test temperature T1 and the test field strength E1.

[0101] S42, using the industrial frequency AC transformer test system, the three test samples in the second group are subjected to industrial frequency AC thermal aging life tests at the test temperature T2, during which the test voltage U2 is applied, and the corresponding test field strength is E2; after the three test samples are broken down, the breakdown time of the three test samples is recorded respectively, and the median value L2 of the three breakdown time data is taken as the insulation life of the second group of test samples at the test temperature T2 and the test field strength E2.

[0102] S43, using the industrial frequency AC transformer test system, the three test samples in the third group are subjected to industrial frequency AC thermal aging life tests at the test temperature T3, during which the test voltage U3 is applied, and the corresponding test field strength is E3; after the three test samples are all broken down, the breakdown time of the three test samples is recorded respectively, and the median value L3 of the three breakdown time data is taken as the insulation life of the third group of test samples at the test temperature T3 and the test field strength E3.

[0103] S43, use the industrial frequency AC transformer test system to conduct industrial frequency AC thermal aging life tests on the three test samples in the fourth group at the test temperature T4, during which the test voltage U4 is applied, and the corresponding test field strength is E4; after the three test samples are all broken down, the breakdown time of the three test samples is recorded respectively, and the median value L4 of the three breakdown time data is taken as the insulation life of the fourth group of test samples at the test temperature T4 and the test field strength E4.

[0104] Among them, T1=T2=T3=T4, and its value range is the ambient temperature range after the stator coil is put into operation.

[0105] U4>U3>U2>U1, for example, U1 can be set to 1.5 times the rated voltage, U2 to 2.0 times the rated voltage, U3 to 2.5 times the rated voltage, and U4 to 3.0 times the rated voltage.

[0106] In summary, the following test result parameter table is obtained:

[0107] Sample set Test voltage Test field strength Insulation life Test temperature Group 1 <![CDATA[U1]]> <![CDATA[E1]]> <![CDATA[L1]]> <![CDATA[T1]]> Group 2 <![CDATA[U2]]> <![CDATA[E2]]> <![CDATA[L2]]> <![CDATA[T2]]> Group 3 <![CDATA[U3]]> <![CDATA[E3]]> <![CDATA[L3]]> <![CDATA[T3]]> Group 4 <![CDATA[U4]]> <![CDATA[E4]]> <![CDATA[L4]]> <![CDATA[T4]]>

[0108] S5, based on the mathematical model of high-voltage motor stator coil insulation voltage durability Substitute the test result parameters into the linear fitting to obtain the insulation performance evaluation formula. s Indicates the insulation life of the stator coil (failure time or end life), E s It represents the field strength of the stator coil. C and n are constants affected by the test conditions (field strength, temperature and other environmental conditions).

[0109] Furthermore, under the condition that the natural logarithm of the test field intensity is the X-axis and the natural logarithm of the life time is the Y-axis, the test result parameters are introduced into the high-voltage motor stator coil insulation voltage durability mathematical model to perform linear fitting, that is, the insulation performance evaluation formula is expressed as Among them, e is a natural constant, which is the base of the natural logarithm; x represents the natural logarithm of the test field intensity, and y represents the natural logarithm of the life time.

[0110] Furthermore, the natural logarithm x of the test field strength and the natural logarithm y of the life time are determined based on the operating characteristics of the high-voltage variable-frequency motor in which the stator coil is located and the insulation life requirements of the stator coil; wherein, 25≤x≤27, 8.05≤y≤8.52.

[0111] S6, based on the insulation performance evaluation formula, the expected insulation life of the stator coil of the high-voltage variable-frequency motor product design is evaluated. Specifically: for the stator coil with the same material, structure and manufacturing process as the test sample, the working field strength design value is obtained according to the factory design data of the high-voltage variable-frequency motor in which it is located; the working field strength design value is used as the field strength received by the stator coil into the insulation performance evaluation formula to obtain the insulation life L s That is the expected insulation life of the stator coil in the corresponding high-voltage variable-frequency motor.

Claims

1. A method for evaluating the main insulation performance of a high-voltage variable-frequency motor stator coil, characterized in that: The following steps are involved: S1, select several stator coils from the same batch as test samples, and conduct the first conventional insulation performance test on all test samples; S2, based on the set test condition parameters, all test samples are subjected to several alternating tests of high-frequency impact electrothermal aging test and power frequency AC electrothermal aging test; S3, conduct secondary conventional insulation performance tests on all test samples; S4, according to the relationship between the working field strength and insulation thickness of the high-voltage motor stator coil, based on different test setting parameters, all current test samples are divided into several groups for power frequency AC thermal aging life test, and the test result parameters of each group of test samples are recorded; S5, based on the mathematical model of insulation voltage durability of high-voltage motor stator coil, the test result parameters are introduced to perform linear fitting to obtain the insulation performance evaluation formula; S6, based on the insulation performance evaluation formula, evaluate the expected insulation life of the stator coil when designing high-voltage variable-frequency motor products.

2. A method for evaluating the main insulation performance of a high-voltage variable-frequency motor stator coil as claimed in claim 1, characterized in that: In step S1 and step S3, the conventional insulation performance test includes: Insulation resistance test: use an insulation resistance tester to detect whether the stator coil insulation is damp or damaged; Dielectric loss test: use a dielectric loss tester to detect the insulation curing state of the stator coil and the insulation density of the coil; Partial discharge test: use a partial discharge tester to detect the insulation density of the stator coil; Power frequency AC withstand voltage test, using the power frequency AC transformer test system to detect the electrical strength of the stator coil insulation; The anti-corona test uses a power frequency AC transformer test system to detect the surface discharge conditions in the high resistance anti-corona area at the end of the stator coil.

3. The method for evaluating the main insulation performance of a stator coil of a high-voltage variable-frequency motor according to claim 1, characterized in that: In step S2, the test condition parameter settings of the high-frequency impact electrothermal aging test include: setting the test peak-to-peak voltage to the maximum sudden change voltage that the variable frequency motor can withstand during operation multiplied by a safety factor of 2.0, the impact rise time is less than 2μs, the test frequency range is 8kHz to 20kHz, the test temperature is 120°C, and the test time is 100h.

4. A method for evaluating the main insulation performance of a stator coil of a high-voltage variable-frequency motor as claimed in claim 1, characterized in that: In step S2, the test condition parameter setting of the power frequency AC thermal aging test includes: setting the applied voltage value to the maximum peak-to-peak value relative to ground voltage during the operation of the variable frequency motor multiplied by a safety factor of 1.5, and setting the equivalent voltage effective value to the peak-to-peak value divided by The test temperature is 120℃ and the test time is 1000h.

5. The method for evaluating the main insulation performance of a stator coil of a high-voltage variable-frequency motor according to claim 1, characterized in that: In step S4, the relationship between the working field strength and insulation thickness of the high-voltage motor stator coil is: Among them, E is the field strength that the stator coil insulation is subjected to, U is the applied test voltage; and d is the insulation thickness of the stator coil.

6. A method for evaluating the main insulation performance of a stator coil of a high-voltage variable-frequency motor as claimed in claim 4, characterized in that: In step S4, the power frequency AC thermal aging life test includes the following steps: For each group of test samples, at the test temperature T i Under the condition of applying U i The test voltage is E, and the stator coil insulation thickness d remains unchanged. i ; After the insulation of the test sample is broken down, record the breakdown time L; For each individual group of test samples, take the median value L among the recorded breakdown times i As the insulation life of the batch of test samples under the current test conditions; Where i represents the test sample group number, T i represents the test temperature of the i-th group of test samples, E i Indicates the test field strength of the i-th group of test samples; U i Indicates the test voltage of the i-th group of test samples, L i Indicates the i-th group of test samples at the test temperature T i , Test field strength E i The median breakdown time under the conditions.

7. A method for evaluating the main insulation performance of a high-voltage variable-frequency motor stator coil as claimed in claim 1, characterized in that: In step S5, the mathematical model of the insulation voltage durability of the high-voltage motor stator coil is expressed as: Among them, L S Indicates the insulation life of the stator coil, E S It represents the field strength of the stator coil, and C and n are constants affected by the test conditions.

8. A method for evaluating the main insulation performance of a stator coil of a high-voltage variable-frequency motor as claimed in claim 6, characterized in that: In step S5, the test result parameters are introduced into the high-voltage motor stator coil insulation voltage durability mathematical model to perform linear fitting under the condition that the natural logarithm of the test field strength is used as the X-axis and the natural logarithm of the life time is used as the Y-axis. That is, the insulation performance evaluation formula is expressed as: Among them, e is a natural constant, which is the base of the natural logarithm; x represents the natural logarithm of the test field intensity, and y represents the natural logarithm of the life time.

9. A method for evaluating the main insulation performance of a stator coil of a high-voltage variable-frequency motor as claimed in claim 7, characterized in that: In step S6, the method for evaluating the expected insulation life of the stator coil is as follows: for the stator coil with the same material, the same structure and the same manufacturing process as the test sample, the working field strength design value is obtained according to the factory design data of the high-voltage variable-frequency motor in which the stator coil is located; the working field strength design value is substituted into the insulation performance evaluation formula as the field strength received by the stator coil, and the obtained insulation life Lc is the expected insulation life of the stator coil in the corresponding high-voltage variable-frequency motor.

10. A method for evaluating the main insulation performance of a stator coil of a high-voltage variable-frequency motor as claimed in claim 7, characterized in that: The natural logarithm x of the test field strength and the natural logarithm y of the life time are determined based on the operating characteristics of the high-voltage variable-frequency motor in which the stator coil is located and the insulation life requirements of the stator coil; wherein, 25≤x≤27, 8.05≤y≤8.52.

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