A non-intrusive method for detecting early insulation faults in asynchronous motors

Abstract

The application relates to the technical field of asynchronous motor fault detection, and particularly discloses a non-invasive early insulation fault detection method for asynchronous motors, which comprises the following steps: collecting electromagnetic wave frequency signals in the space where the asynchronous motor body operates, and obtaining electromagnetic wave frequency band A stored in the space when the asynchronous motor body operates; comparing electromagnetic wave frequency band C generated by partial discharge and spark discharge caused by insulation defects of the asynchronous motor body with the electromagnetic wave frequency band A, eliminating interference, and forming interference-free electromagnetic wave frequency band C'; obtaining the electromagnetic wave frequency band C' through an antenna receiving electromagnetic waves; and determining that insulation defects exist in the asynchronous motor body and partial discharge and spark discharge are generated when the antenna obtains the electromagnetic wave frequency band C'.

Description

Technical Field

[0001] This invention relates to the field of asynchronous motor fault detection technology, and specifically to a non-invasive method for detecting early insulation faults in asynchronous motors. Background Technology

[0002] Asynchronous motors are robust in structure and have mature manufacturing processes. Their operational reliability directly affects production safety and efficiency. Once a failure occurs, the resulting losses are often systemic and catastrophic.

[0003] When the internal insulation of an asynchronous motor breaks down, leading to a short circuit, it signifies the end of the motor's lifespan. Monitoring electrical faults in asynchronous motors, especially early-stage insulation defects, partial discharges, and weak spark discharges, is crucial. It effectively improves the timeliness and accuracy of fault diagnosis, reducing the risk of unplanned downtime.

[0004] There are roughly three common methods for detecting asynchronous motor faults: vibration signal analysis, temperature analysis, and electrical quantity analysis. Most of the related structures used for these methods need to be installed inside the asynchronous motor and require a power outage for installation. However, in some operating conditions where it is inconvenient to stop the asynchronous motor, online installation and monitoring are not feasible. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a non-invasive method for detecting early insulation faults in asynchronous motors. This method has the advantage of detecting insulation defects without opening the motor casing or interrupting power supply, thus solving the problem that existing technologies cannot detect insulation faults without shutting down the motor.

[0006] The non-intrusive method for detecting early insulation faults in asynchronous motors according to the present invention includes the following steps: S1. Collect electromagnetic wave frequency signals in the space where the asynchronous motor is running, and obtain the electromagnetic wave frequency band A in the space where the asynchronous motor is running; and analyze the electromagnetic wave frequency band A to obtain the electromagnetic wave frequency band a generated by the asynchronous motor and the abnormal electromagnetic wave frequency band b. S2. Based on the electromagnetic wave frequency band c generated by partial discharge and spark discharge caused by insulation defects in the asynchronous motor body, compare electromagnetic wave frequency band c with electromagnetic wave frequency band a and electromagnetic wave frequency band b, and eliminate the interference of electromagnetic wave frequency band a and electromagnetic wave frequency band b to form an interference-free electromagnetic wave frequency band c`. S3. Obtain the electromagnetic wave frequency band c` through the antenna that receives electromagnetic waves. When the antenna obtains the electromagnetic wave frequency band c`, it is determined that there is an insulation defect inside the asynchronous motor body and partial discharge and spark discharge are generated.

[0007] S3.1 By utilizing the characteristics of the asynchronous motor body, an antenna is placed outside the heat dissipation holes at the rear of the asynchronous motor body to capture the electromagnetic wave frequency band c`, thereby achieving non-invasive fault detection of insulation discharge faults inside the asynchronous motor body.

[0008] In some embodiments, the antenna is an N-element array antenna arranged in a linear array, and the detection frequency of the array elements in the N-element array antenna is a fixed frequency band between electromagnetic wave frequency bands c'.

[0009] In some embodiments, by adjusting the size of the array elements in the N-element array antenna, each array element has only one receiving frequency point located in the electromagnetic wave frequency band c', thus avoiding noise interference.

[0010] In some embodiments, the spacing between the array elements in the N-element array antenna is adjusted to form a gain beam that achieves balance.

[0011] In some embodiments, the size of the N-element array antenna is smaller than the size of the heat dissipation hole area of ​​the asynchronous motor body.

[0012] In some embodiments, the N-element array antenna has four elements, and the array antenna with four elements is set as a four-element array antenna. The electromagnetic wave signals received by the array elements in the four-element array antenna enter the receiver for amplification and detection through an impedance matching network. The array elements in the four-element array antenna with a high receiving frequency are set as high-frequency array elements, and the high-frequency array elements include the same first high-frequency array element and second high-frequency array element. The array elements in the four-element array antenna with a low receiving frequency are set as low-frequency array elements, and the low-frequency array elements include the same first low-frequency array element and second low-frequency array element. The width of the high-frequency array element and the low-frequency array element is 37.2 mm, and the height of the high-frequency array element and the low-frequency array element is 28.1 mm and 60 mm, respectively.

[0013] In some embodiments, the distance between the high-frequency array element and the low-frequency array element, as well as the distance between the first low-frequency array element and the second low-frequency array element, is 20-25mm.

[0014] In some embodiments, the PCB dielectric material used in the N-element array antenna has a dielectric constant of 4.4 and a thickness of 1.6 mm.

[0015] In some embodiments, the quad array antenna transforms the impedance to 50 ohms through an impedance matching network.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention collects electromagnetic wave signals present in the operating space of the asynchronous motor body, as well as electromagnetic wave signals generated by partial discharge and spark discharge caused by insulation defects in the asynchronous motor body. By eliminating interference signal frequency bands through elimination, the remaining frequency bands can be detected by antenna to determine whether there are partial discharges and spark discharges caused by insulation defects in the asynchronous motor body.

[0017] 2. This invention utilizes the characteristic that electromagnetic wave signals generated by insulation defect discharge can penetrate the heat dissipation holes of the asynchronous motor body. It can be installed in a non-intrusive manner without opening the casing or interrupting power. The antenna can be installed at the heat dissipation hole at the rear of the asynchronous motor body. Compared with existing detection equipment technology placed inside the asynchronous motor body, it has the advantage of not requiring power interruption for installation and can also detect the asynchronous motor body in operation.

[0018] 3. The present invention uses an N-element array antenna, which is significantly superior to an omnidirectional antenna under the same transmission power and operating frequency, and can detect the electromagnetic wave frequency band c' transmitted by the asynchronous motor body due to insulation fault more sensitively and accurately. 4. The four-element array antenna of this invention uses a width of High-frequency array elements and When the low-frequency array element has a spacing of 23mm, it has three balanced beams with good directivity and high gain. This means it can effectively detect early-stage electrical sparks caused by insulation faults, while also avoiding interference from the noise frequency band of the asynchronous motor and the signal frequency band of the mobile phone base station.

[0019] 5. The four-element array antenna of the present invention can effectively perform non-invasive detection of asynchronous motors when the detection is limited by operation and installation space. Especially under the conventional installation of asynchronous motors, a certain amount of heat dissipation space needs to be left behind the heat dissipation holes, thus providing detection space for the four-element array antenna provided by this solution. That is, the four-element array antenna of this solution can not only detect and determine the internal insulation fault of the asynchronous motor, but also effectively utilize the actual heat dissipation space requirement of the asynchronous motor to achieve convenient detection. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of electromagnetic wave frequency band A existing in the space where the asynchronous motor body of the present invention is running; Figure 2This is a simulation diagram of electromagnetic wave signal diffusion when there is an insulation defect at the brush location in this invention; Figure 3 This is a simulation diagram of electromagnetic wave signal diffusion when there is an insulation defect in the front air gap of the present invention. Figure 4 This is a simulation diagram of electromagnetic wave signal diffusion when there is an insulation defect in the air gap in the middle of the present invention. Figure 5 This is a schematic diagram of the four-element array antenna of the present invention; Figure 6 The dimensions of the high-frequency array element of this invention are Return loss diagram at time; Figure 7 This is a simulation diagram of the detection beam when the element spacing in the four-element array antenna of the present invention is 31mm; Figure 8 This is a simulation diagram of the detection beam when the element spacing in the four-element array antenna of the present invention is 23mm; Figure 9 This is a Smith chart of the four-element array antenna of the present invention; Figure 10 This is an electric field distribution diagram of the four-element array antenna of the present invention; Figure 11 This is a magnetic field distribution diagram of the four-element array antenna of the present invention; Figure 12 This is a three-dimensional radiation gain diagram of the four-element array antenna of the present invention; Figure 13 This is a return loss diagram of the four-element array antenna of the present invention.

[0021] In the diagram: 1. 300MHz band; 2. 900MHz band; 3. 1.8GHz band; 4. 2.4GHz band; 5. Quad-element array antenna; 6. Heat dissipation hole; 7. Asynchronous motor body; 8. First high-frequency array element; 9. First low-frequency array element; 10. Second high-frequency array element; 11. Second low-frequency array element; 12. Network; 13. PCB dielectric material; 14. 1.14GHz frequency point; 15. 2.23GHz receiving frequency point; 16. Insulation defect at the brush position; 17. Insulation defect in the front air gap; 18. Insulation defect in the middle air gap; 19. Beam. Detailed Implementation

[0022] The following drawings will disclose several embodiments of the present invention. For clarity, many physical details will be described in the following description. However, it should be understood that these physical details are not intended to limit the invention. That is, in some embodiments of the invention, these physical details are not essential. Furthermore, for the sake of simplicity, some conventional structures and components will be shown in the drawings in a simple schematic manner.

[0023] In addition, in the present invention, descriptions such as "first", "second", etc. are only for descriptive purposes, and do not particularly refer to the meaning of order or sequence, nor are they used to limit the present invention. They are merely used to distinguish components or operations described with the same technical terms, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0024] Embodiment 1: The non-invasive early insulation fault detection method for an asynchronous motor of the present invention includes the following steps: S1. Collect electromagnetic wave frequency signals in the space where the asynchronous motor body 7 operates, and obtain the electromagnetic wave frequency band A existing in the space during the operation of the asynchronous motor body 7; and analyze the electromagnetic wave frequency band A to obtain the electromagnetic wave frequency band a generated during the operation of the asynchronous motor body 7, and the abnormal electromagnetic wave frequency band b; S2. According to the electromagnetic wave frequency band c generated during partial discharge and spark discharge caused by insulation defects of the asynchronous motor body 7, compare the electromagnetic wave frequency band c with the electromagnetic wave frequency bands a and b, and eliminate the interference of the electromagnetic wave frequency bands a and b to form an interference-free electromagnetic wave frequency band c'; S3. Obtain the electromagnetic wave frequency band c' through the antenna that receives electromagnetic waves. When the antenna obtains the electromagnetic wave frequency band c', it is determined that there are insulation defects inside the asynchronous motor body 7 and partial discharge and spark discharge occur; In this embodiment: As Figure 1 shown, the electromagnetic wave frequency band A existing in the space during the operation of the asynchronous motor body 7, where the electromagnetic wave frequency band A includes the electromagnetic wave frequency band a and the electromagnetic wave frequency band b; the electromagnetic wave frequency band a is below the 300 MHz band 1; the electromagnetic wave frequency band b includes multiple strong electromagnetic wave frequency bands, which are respectively the 900 MHz band 2, the 1.8 GHz band 3, and the 2.4 GHz band 4. These are the signal frequencies of mobile phone base stations and belong to strong interference electromagnetic wave frequencies; Using the actual measurement method, the measured electromagnetic wave frequency band c is 300 MHz - 3 GHz. Therefore, the electromagnetic wave frequency band c' is {c'|300 MHz < c' < 3 GHz and c' ≠ 900 MHz, c' ≠ 1.8 GHz, c' ≠ 2.4 GHz}.

[0025] In this embodiment: S3.1 By utilizing the characteristics of the outer shell of the asynchronous motor body 7, an antenna is placed outside the heat dissipation hole 6 at the tail of the asynchronous motor body 7 to capture the electromagnetic wave frequency band c`, thereby achieving non-invasive fault detection of insulation discharge faults inside the asynchronous motor body 7. Please see Figures 2-4 Because the asynchronous motor body 7 is encased in a thick metal casing with minimal or no gaps, electromagnetic waves have difficulty penetrating. However, the asynchronous motor body 7 generates a significant amount of heat, and each asynchronous motor body 7 has heat dissipation holes 6 at its rear. These holes effectively release the electromagnetic wave signals from within the asynchronous motor body 7. Therefore, through software simulation, when insulation defects occur at different locations within the asynchronous motor body 7, electromagnetic waves can primarily penetrate through the heat dissipation holes 6 of the asynchronous motor body 7. Figure 2 Simulation diagram of electromagnetic wave signal diffusion at the location of the brush with insulation defect 16. Figure 3 Simulation diagram of electromagnetic wave signal diffusion when there is an insulation defect in the front air gap at time 17. Figure 4 Simulation diagram of electromagnetic wave signal diffusion at 18 degrees Celsius due to insulation defects in the middle air gap; It can be seen that placing the antenna at the heat dissipation hole 6 at the rear of the asynchronous motor body 7 to capture the electromagnetic wave frequency band c` can effectively detect the electromagnetic wave signal inside the asynchronous motor body 7. In practical use, by taking advantage of the characteristic that the electromagnetic wave signal generated by the discharge of insulation defects can penetrate the heat dissipation hole 6 of the asynchronous motor body 7, it is possible to install it in a non-intrusive manner without opening the casing or interrupting the power supply. The antenna can be installed at the heat dissipation hole 6 at the tail of the asynchronous motor body 7. Compared with the existing detection equipment technology placed inside the asynchronous motor body 7, it has the advantage of not requiring power interruption for installation, and can also detect the asynchronous motor body 7 in operation.

[0026] Example 2: As a further description of the antenna described in Embodiment 1, the antenna is an N-element array antenna arranged in a linear array manner, and the detection frequency of the array elements in the N-element array antenna is a fixed frequency band between electromagnetic wave frequency bands c'.

[0027] By adjusting the size of the array elements in the N-element array antenna, each array element has only one receiving frequency point located in the electromagnetic wave frequency band c', thus avoiding noise interference.

[0028] The gain beam is balanced by adjusting the spacing between the array elements in the N-element array antenna.

[0029] The size of the N-element array antenna is smaller than the size of the heat dissipation hole 6 area of ​​the asynchronous motor body 7. Since the frequency generated by the insulation fault of the asynchronous motor body 7 is a fixed frequency band between 300MHz and 3GHz, the size of each element is relatively fixed. As the number of elements increases, the size of the entire antenna array will continuously increase. Since the asynchronous motor body 7 is often placed in confined spaces, an antenna that is too large is not easy to install. Furthermore, when the antenna array size exceeds the size of the heat dissipation hole 6, a portion of the beam will inevitably be outside the heat dissipation hole 6, thus weakening its detection sensitivity. Typically, the diameter of the heat dissipation hole 6 of an asynchronous motor body 7 below 10kV is generally less than 20cm. When the number of elements N is greater than 8, the size of the entire antenna array is often greater than 20cm. Therefore, considering maximizing detection sensitivity while also considering antenna size, 4-8 elements are usually optimal.

[0030] In this embodiment, the antenna is an N-element array antenna arranged in a linear array. Compared with the existing omnidirectional antenna, the N-element array antenna has a significant gain effect under the same transmission power and operating frequency, and can better detect the electromagnetic wave frequency band c'. According to the formula for calculating free-space received power: ; Omnidirectional antenna gain under ideal conditions The maximum gain of an N-element array antenna is approximately: Under the same transmission power and operating frequency: Omnidirectional antenna received power: ; Array antenna received power: ; The ratio of received power of the array antenna to that of the omnidirectional antenna: ; The corresponding improvements in gain and sensitivity are: ; The effective communication distance improvement factor of the array antenna compared to the omnidirectional antenna is: ; in For received power, For transmission power, Transmit antenna gain Receive antenna gain The operating wavelength, R is the straight-line distance between the transmitting and receiving antennas, L is the system's additional loss, and 4π is the solid angle coefficient of free space radiation.

[0031] Table 1, which compares the parameters of the N-element array antenna and the omnidirectional antenna, is obtained as a result. Table 1 ; In summary, the N-element array antenna is significantly superior to the omnidirectional antenna at the same transmission power and operating frequency, and can detect the electromagnetic wave frequency band c` transmitted by the asynchronous motor body 7 due to insulation faults more sensitively and accurately.

[0032] Example 3: When the PCB dielectric material 13 used in the N-element array antenna has a dielectric constant of 4.4 and a thickness of 1.6mm, the array antenna has 4 elements, and the array antenna with 4 elements is set as a four-element array antenna 5. The electromagnetic wave signal received by the array elements in the four-element array antenna 5 enters the receiver for amplification and detection through the impedance matching network 12. The array elements with a high receiving frequency in the four-element array antenna 5 are set as high-frequency array elements, and the high-frequency array elements include the same first high-frequency array element 8 and second high-frequency array element 10. The array elements with a low receiving frequency in the four-element array antenna 5 are set as low-frequency array elements, and the low-frequency array elements include the same first low-frequency array element 9 and second low-frequency array element 11. Because the array elements are "planar microstrip patch array elements," array elements of different sizes have different receiving frequencies and different gains. Therefore, it is necessary to simulate or measure the specific dimensions of the high-frequency and low-frequency array elements. When the array element width is fixed at 37.2mm, the height changes of the high-frequency and low-frequency array elements will change the receiving frequency. The specific data are shown in Tables 2 and 3 below: Table 2 ; Table 3 ; As shown in Tables 2 and 3, when the height of the high-frequency array element is greater than or less than 28.1 mm, and the height of the low-frequency array element is greater than or less than 60 mm, multiple receiving frequency points will appear, and most of them will be in or near the noise frequency band, making them very susceptible to interference during detection; for example, the size of the high-frequency array element is... At that time, receiving frequencies of 2.21 GHz and 2.67 GHz appeared in the high-frequency band, such as... Figure 6 As shown, 2.67GHz is in the noise band and is very susceptible to noise interference.

[0033] Therefore, when the left and right dimensions of the high-frequency array element and the low-frequency array element are approximately 28.1mm and 60mm respectively, there is only one receiving frequency point, which avoids noise interference and also has a large gain. In summary, the width of the high-frequency array element and the low-frequency array element is 37.2 mm, and the height of the high-frequency array element and the low-frequency array element is 28.1 mm and 60 mm, respectively.

[0034] In this embodiment, the four-element array antenna 5 generates three detection beams. When the distance between the high-frequency array element and the low-frequency array element changes, the detection range beam formed by the high-frequency array element and the low-frequency array element will change. The specific data obtained by actual measurement or simulation are shown in Tables 4 and 5 below: Table 4 ; Table 5 ; For example, when the distance between the high-frequency array element and the low-frequency array element is 31mm, the middle beam of the three beams is very weak. Figure 7 As shown, compared to the three beams with basic gain equalization, there is a problem of missed detection.

[0035] As shown in Tables 4 and 5, when the distance between the high-frequency array element and the low-frequency array element, as well as the distance between the first low-frequency array element 9 and the second low-frequency array element 10, are both 20-25 mm, preferably 23 mm, the gain of the three beams is basically balanced. The specific beam model is as follows: Figure 8 As shown.

[0036] When the width of the high-frequency array element and the low-frequency array element is 37.2mm, the height of the high-frequency array element and the low-frequency array element is 28.1mm and 60mm respectively, and the distance between the high-frequency array element and the low-frequency array element and the distance between two high-frequency array elements are both 23mm. The return loss of this quaternary array antenna 5 is as follows: Figure 13 There are 1.14GHz receiving frequency point 14 and 2.23GHz receiving frequency point 15, which effectively avoids the noise frequency band of the asynchronous motor body 7 and the mobile phone base station signal frequency band.

[0037] The Smith chart of this quaternary array antenna 5 is shown below. Figure 9 ,exist Figure 9 The output impedance 16 of the antenna is very close to the center of the circle, meaning the output impedance is close to 50 ohms. This indicates that by transforming the impedance of the microstrip antenna array to 50 ohms through the impedance matching network 12, the circuit can achieve optimal impedance matching. Therefore, the aforementioned quad-element array antenna 5 transforms its impedance to 50 ohms through the impedance matching network 12.

[0038] The electric and magnetic field distribution diagrams of this four-element array antenna 5 are shown below. Figure 10 and Figure 11 As can be seen from the figure, the electromagnetic field radiation area is mainly concentrated in the center of the array element and points in front of the array element.

[0039] As can be seen from Embodiment 1, the heat dissipation hole 6 of the asynchronous motor body 7 is a good electromagnetic wave propagation channel. When the antenna in Embodiment 1 is the four-element array antenna 5 in this embodiment, the three narrow beams 19 formed by the four-element array antenna 5 can well point to and cover the electromagnetic wave signal penetrating from the heat dissipation hole 6, such as... Figure 12 As shown.

[0040] In summary, the quad array antenna 5 designed in this embodiment has excellent directivity and high gain, while effectively avoiding interference from the noise frequency band of the asynchronous motor body 7 and the mobile phone base station signal frequency band. Furthermore, by utilizing the electromagnetic wave transmission channel of the heat dissipation hole 6 of the asynchronous motor body 7, it is possible to detect the weak electromagnetic wave signal generated by early insulation defects inside the asynchronous motor body 7.

[0041] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A non-invasive method for detecting early insulation faults in asynchronous motors, characterized in that, Includes the following steps: S1. Electromagnetic wave frequency signal is collected in the space where the asynchronous motor body (7) is running, and electromagnetic wave frequency band A is obtained in the space where the asynchronous motor body (7) is running; and electromagnetic wave frequency band A is analyzed to obtain electromagnetic wave frequency band a and abnormal electromagnetic wave frequency band b generated by the asynchronous motor body (7) during operation. S2. Based on the electromagnetic wave frequency band c generated by partial discharge and spark discharge caused by insulation defects of the asynchronous motor body (7), compare electromagnetic wave frequency band c with electromagnetic wave frequency band a and electromagnetic wave frequency band b, and eliminate the interference of electromagnetic wave frequency band a and electromagnetic wave frequency band b to form an interference-free electromagnetic wave frequency band c`. S3. Obtain the electromagnetic wave frequency band c` through the antenna that receives electromagnetic waves. When the antenna obtains the electromagnetic wave frequency band c`, it is determined that there is an insulation defect inside the asynchronous motor body (7) and partial discharge and spark discharge are generated.

2. The non-intrusive method for detecting early insulation faults in an asynchronous motor according to claim 1, characterized in that: S3.1 By taking advantage of the characteristics of the asynchronous motor body (7), the antenna is placed outside the heat dissipation hole (6) at the tail of the asynchronous motor body (7) to capture the electromagnetic wave frequency band c`, thereby realizing non-invasive fault detection of insulation discharge fault inside the asynchronous motor body (7).

3. The non-invasive method for detecting early insulation faults in an asynchronous motor according to claim 2, characterized in that: The antenna is an N-element array antenna arranged in a linear array, and the detection frequency of the array elements in the N-element array antenna is a fixed frequency band between electromagnetic wave frequency bands c'.

4. The method for detecting early insulation faults in a non-invasive asynchronous motor according to claim 3, characterized in that: By adjusting the size of the array elements in the N-element array antenna, each array element has only one receiving frequency point located in the electromagnetic wave frequency band c', thus avoiding noise interference.

5. The non-invasive method for detecting early insulation faults in an asynchronous motor according to claim 3, characterized in that: The gain beam is balanced by adjusting the spacing between the array elements in the N-element array antenna.

6. The method for detecting early insulation faults in a non-invasive asynchronous motor according to claim 5, characterized in that: The size of the N-element array antenna is smaller than the size of the heat dissipation hole (6) area of ​​the asynchronous motor body (7).

7. The method for detecting early insulation faults in a non-invasive asynchronous motor according to claim 6, characterized in that: The N-element array antenna has four elements. The array antenna with four elements is set as a four-element array antenna (5). The electromagnetic wave signal received by the array elements in the four-element array antenna (5) enters the receiver for amplification and detection through the impedance matching network (12). The array elements with a large receiving frequency in the four-element array antenna (5) are set as high-frequency array elements. The high-frequency array elements include the same first high-frequency array element (8) and second high-frequency array element (10). The array elements with a small receiving frequency in the four-element array antenna (5) are set as low-frequency array elements. The low-frequency array elements include the same first low-frequency array element (9) and second low-frequency array element (11). The width of the high-frequency array element and the low-frequency array element is 37.2 mm, and the height of the high-frequency array element and the low-frequency array element is 28.1 mm and 60 mm, respectively.

8. The non-invasive method for detecting early insulation faults in an asynchronous motor according to claim 7, characterized in that: The distance between the high-frequency array element and the low-frequency array element, as well as the distance between the first low-frequency array element (9) and the second low-frequency array element (10), are all 20-25mm.

9. A non-invasive method for detecting early insulation faults in an asynchronous motor according to claim 7 or 8, characterized in that: The N-element array antenna uses a PCB dielectric material (13) with a dielectric constant of 4.4 and a thickness of 1.6 mm.

10. A non-invasive method for detecting early insulation faults in an asynchronous motor according to claim 9, characterized in that: The quad array antenna (5) transforms the impedance to 50 ohms through an impedance matching network (12).

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