Contactor contact electrical wear detection device and contact overtravel calculation method
By setting two stroke switches with different strokes in the AC contactor, calculating the contact over-stroke and issuing an alarm, the problem of difficulty in detecting electrical wear in the prior art is solved, and the accuracy of the life of the contactor is achieved and the convenience of accurate prediction and maintenance of the contactor is achieved.
Patent Information
- Application Number
- CN202411867760.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-18
- Publication Date
- 2025-04-22
AI Technical Summary
The prior art is difficult to effectively detect the amount of electrical wear of AC contactor contacts, resulting in inaccurate forecasting of contactor life, inconvenient maintenance, and additional components and costs.
A contact contact electrical wear detection device is designed, and by setting two stroke switches with different strokes, the contact over-stroke of the contactor is calculated, and an alarm signal is issued when the over-stroke is less than a predetermined value.
Real-time monitoring of electrical wear of contactor contacts is realized, alarms are issued in advance, contactor failures and economic losses caused by contactor wear, and the reliability of the electrical system is improved.
Smart Images
Figure CN119860704A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of switch equipment, in particular to a contactor contact electrical wear detection device and a contact overtravel calculation method. Background Art
[0002] An AC contactor is an electrical appliance used to frequently connect and disconnect AC and DC main circuits and large-capacity control circuits over long distances. Its main control object is the motor, but it can also be used to control electrical loads such as electric heating equipment, electric lighting, electric welding machines and capacitor banks.
[0003] When the AC contactor disconnects the circuit, an arc and a large amount of heat will be generated between the moving contact and the static contact. Along with the transfer of the arc, the contact materials of the moving contact and the static contact will splash and evaporate, and the contact thickness will gradually decrease, which is generally referred to as the electrical wear of the contactor. Electrical wear will cause the contact pressure of the AC contactor to decrease, the contact resistance to increase, and the contact reliability to decrease. In order to ensure the contact pressure, the contact bracket will continue to move a certain distance after the contact contacts during the contactor closing process. This distance is called the contact overtravel in the field of low-voltage electrical appliance design. As the electrical wear progresses, the contact overtravel gradually decreases, eventually leading to a connection failure or a disconnection failure. If the amount of electrical wear of the AC contactor contacts can be predicted, the life of the contactor can be predicted, and planned maintenance or replacement can be carried out to avoid greater economic losses caused by sudden failures of the contactor.
[0004] At present, the remaining life prediction of AC contactors mainly relies on the statistical data of product sampling tests in the product design stage, that is, the electrical life data provided by product manufacturers. Although this method can reflect the average design life of a certain specification of AC contactors, in fact, due to the influence of many factors such as the manufacturing process, storage, load type, and use environment of contactor parts, the service life and average service life of individual contactors vary greatly.
[0005] In some snap-on AC contactors, the amount of contact wear can be indicated by a mechanical pointer. However, for direct-acting AC contactors, the product needs to be disassembled to detect the amount of contact wear, which makes inspection and maintenance very inconvenient, especially for electrical systems that require continuous operation. The product needs to be disassembled after shutdown for inspection and maintenance, which affects the normal production.
[0006] In some low-voltage circuit breakers and related literature, a technical solution is used to estimate the remaining life of the product by monitoring the current and voltage during disconnection to calculate the arc energy and then estimate the amount of contact wear. However, for contactors, additional components such as voltage transformers and current transformers are required, which will greatly increase the size and cost of the product. Summary of the invention
[0007] The purpose of the present invention is to provide a contactor contact electrical wear detection device and a contact overtravel calculation method, two travel switches with different travels are set, and the contact overtravel of the contactor is calculated. When the contact overtravel is less than a predetermined value, it is considered that the contact wear has reached a critical point, and an alarm signal is sent to the user through an alarm circuit to solve the problems existing in the prior art.
[0008] To achieve the above object, the technical solution adopted by the present invention is: A contactor contact electrical wear detection device comprises a signal detection module installed on the upper surface of a contactor housing, the signal detection module comprises a left travel switch and a right travel switch, both travel switches are connected to a microcontroller, the top of the left travel switch and the right travel switch are provided with a driving rod with the front end tilted in the same direction, the top position of the left driving rod is lower than the top position of the right driving rod, the top of the driving rod is provided with a contact shaft, the left and right ends of the contact shaft respectively penetrate the mounting holes at the top of the contact support of the contactor, the lower part of the contact support penetrates the housing and is connected to the moving contact, the lower part of the moving contact is provided with a contact spring, the bottom of the moving contact is provided with a reaction spring, the contact shaft is connected with one end of a clamping handle, the other end of the clamping handle is fixed on the side walls of both sides of the moving magnet, a static magnet fixed on the upper surface of the housing is provided below the moving magnet, a coil is installed between the moving magnet and the static magnet; the spacing between the top of the left driving rod and the top of the right driving rod is smaller than the spacing between the moving contact and the static contact when the contactor leaves the factory.
[0009] Preferably, the microcontroller is connected to an alarm circuit.
[0010] A method for calculating overtravel of contactor contacts, the method is implemented based on the above-mentioned contactor contact electrical wear detection device. When the coil is energized, the moving magnet moves downward and is attracted by the static magnet. The moving magnet drives the contact bracket and the moving contact to move downward together through the contact shaft. The moving contact and the static contact are closed. During the movement, the contact shaft contacts the top of the right driving rod and the top of the left driving rod in turn. The two travel switches are closed successively, and the travel switch closing signal is transmitted to the microcontroller. When the coil loses power, the moving magnet is disconnected from the static magnet, and the moving contact and the static contact are closed at the same time. The contacts are disconnected, and the moving contact accelerates upward under the joint action of the contact spring and the reaction spring, with an acceleration of a1. When the contact spring is fully extended, the moving contact continues to move upward only under the action of the reaction spring, with an acceleration of a2. The contact bracket moves upward with the moving contact, and successively separates from the top of the left drive rod and the top of the right drive rod. The left travel switch opens at t2, and the right travel switch opens at t3. The travel difference between the two travel switches is s, and the action time difference is t3-t2. The calculation formula for the contact overtravel S1 of the moving contact is: (1) Where: k1 is the elastic coefficient of the contact spring; S2 is the movement stroke of the left travel switch (12) from the start of movement of the contact support (6) to the opening of the travel switch (12); S3 is the movement stroke of the right travel switch (11) from the start of movement of the contact support (6) to the opening of the travel switch (11); t=t3-t2, is the action time difference between the left travel switch (12) and the right travel switch (11); m is the total mass of the moving contact (7), the contact support (6), the contact spring (9), the shaft (5), and the moving magnet (4).
[0011] Preferably, in the formula (1), according to the machining accuracy of the parts, the errors of k1, k2, S2, S3, and m, the value of k1 is much larger than the value of k2, and the estimated deviation is corrected by using the contact overtravel data measured mechanically during the contactor production stage. The simplified and corrected calculation formula of the contact overtravel is as follows: (2) Where c is the correction value.
[0012] Preferably, the contact overtravel S1 is filtered: The calculated contact overtravel S1 value is discrete. When the contactor's contact closing and breaking times reach m times, the median S1(n) of the m groups of calculated contact overtravel S1 data is taken. After every m breaking times, a recursive numerical filtering calculation is performed. The contact overtravel S1 (n+1) filtering algorithm formula is: S1(n+1)=S1(n-1)*k+S1(n)*(1-k) (3) Where: k is the filter coefficient, and its value is between 0 and 1; S1(n-1) is the calculation result of the last filtering; S1(n) is the median value of the sorted S1 data of the m contact overtravels in this round.
[0013] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, two left-side travel switches and a right-side travel switch are provided, and the travels of the two travel switches are different. When the contacts are disconnected, the shaft linked with the contacts will sequentially trigger the two travel switches. By detecting the time difference t between the two travel switches, the contact overtravel of the contactor can be calculated using a formula. When the contact overtravel is less than a predetermined value, it is considered that the contact wear has reached a critical point, and an alarm signal is sent to the user through the alarm circuit.
[0014] During use of the present invention, if the contactor has product failure problems such as deformation of the moving contact or breakage of the contact spring, the reaction force of the contactor will change significantly, and the time difference t between the two travel switches will change significantly when the contactor is disconnected. The present invention can immediately detect this type of failure.
[0015] During use, the present invention runs a test each time the contact is disconnected, thereby realizing real-time monitoring of the electrical wear of the contact. When the contact wear has reached the critical point of the remaining life, an alarm is issued, so that the user can carry out planned shutdown and maintenance, avoiding major accidents such as contactor heating, combustion and fire caused by unreliable contact due to contact wear, thereby improving the reliability of the electrical system. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2 yes Figure 1 A cross-sectional view of the present invention; Figure 3 yes Figure 1 Schematic diagram of the structure of the middle contact bracket Figure 4 It is a schematic diagram of the two travel switch driving rods when the moving magnet and the static magnet are in the attracted state; Figure 5 It is a schematic diagram of the two travel switch driving rods when the moving magnet and the static magnet are in the released state; Figure 6 It is a schematic diagram of the connection structure between the contact shaft and the moving magnet; Figure 7 It is the relationship diagram between the contact support displacement point of the contactor and the corresponding time; Figure 8 It is the flow chart of the signal detection module of the contactor; In the figure: 1. AC contactor, 2. signal detection module, 3. coil, 4. moving magnet, 5. shaft, 6. contact bracket, 7. moving contact, 8. static contact, 9. contact spring, 10. reaction spring, 11, 12 position switch, 13, 14 driving rod of position switch, 15, static magnet, 16. lever, 17, lever support, 18, moving magnet connecting part. DETAILED DESCRIPTION
[0017] The present invention will be further described in detail below in conjunction with the accompanying drawings.
[0018] like Figure 1A contactor contact electrical wear detection device shown in the figure comprises a signal detection module 2 installed on the upper surface of a contactor housing 1, the signal detection module 2 comprises a left travel switch 12 and a right travel switch 11, both travel switches are connected to a microcontroller, the top of the left travel switch 12 and the top of the right travel switch 11 are both provided with a driving rod with the front end tilted in the same direction, the top position of the left driving rod 14 is lower than the top position of the right driving rod 13, the top of the driving rod is provided with a contact shaft 5, the left and right ends of the contact shaft 5 respectively penetrate the installation holes at the top of the contact bracket 6 of the contactor The mounting hole is provided, and the lower part of the contact bracket 6 passes through the shell 1 and is connected to the moving contact 7. The lower part of the moving contact 7 is installed with a contact spring 9, and the bottom of the moving contact 7 is installed with a reaction spring 10. The contact shaft 5 is connected to one end of the clamping handle 16, and the other end of the clamping handle 16 is fixed to the side walls of both sides of the moving magnet 4. A static magnet 15 fixed to the upper surface of the shell 1 is provided below the moving magnet 4, and a coil 3 is installed between the moving magnet 4 and the static magnet 15; the distance between the top end of the left driving rod 14 and the top end of the right driving rod 13 is smaller than the distance between the moving contact 7 and the static contact 8 when the contactor leaves the factory.
[0019] The microcontroller is connected to the alarm circuit.
[0020] A method for calculating overtravel of contactor contacts, the method is implemented based on the above-mentioned contactor contact electrical wear detection device. When the coil 3 is energized, the moving magnet 4 moves downward and is attracted by the static magnet 15. The moving magnet 4 drives the contact bracket 6 and the moving contact 7 to move downward together through the contact shaft 5. The moving contact 7 is closed with the static contact 8. The contact shaft 5 contacts the top of the right driving rod 13 and the top of the left driving rod 14 in turn during the movement. The two travel switches are closed successively, and the travel switch closing signal is transmitted to the microcontroller. When the coil 3 loses power, the moving magnet 4 is disconnected from the static magnet 15, and the moving contact 7 and the static contact 8 are closed at the same time. The contact 8 is disconnected, and the moving contact 7 accelerates upward under the joint action of the contact spring 9 and the reaction spring 10, with an acceleration of a1. When the contact spring 9 is fully extended, the moving contact 7 continues to move upward only under the action of the reaction spring 10, with an acceleration of a2. The contact bracket 6 moves upward with the moving contact 7, and successively disengages from the top of the left driving rod 14 and the top of the right driving rod 13. The left travel switch 12 opens at time t2, and the right travel switch 11 opens at time t3. The travel difference between the two travel switches is s, and the action time difference is t3-t2. The calculation formula for the contact overtravel S1 of the moving contact 7 is: (1) Where: k1 is the elastic coefficient of the contact spring; S2 is the movement stroke of the left travel switch 12 from the start of the movement of the contact support 6 to the opening of the travel switch 12; S3 is the movement stroke of the right travel switch 11 from the start of the movement of the contact support 6 to the opening of the travel switch 11; t=t3-t2, is the action time difference between the left travel switch 12 and the right travel switch 11; m is the total mass of the moving contact 7 , the contact support 6 , the contact spring 9 , the shaft 5 , and the moving magnet 4 .
[0021] For a general AC contactor, k1, k2, S2, S3, and m in formula (1) are all known physical quantities, and t can be measured. Therefore, the contact overtravel can be directly calculated using formula (1).
[0022] Considering the influence of the machining accuracy of the parts, there may be errors in k1, k2, S2, S3, and m. Considering that k1 is much larger than k2 in this embodiment, formula (1) can be simplified. At the same time, the estimated deviation is corrected by using the contact overtravel data measured by mechanical means during the contactor production stage. The simplified and corrected calculation formula for the contact overtravel is as follows: (2) Where c is the correction value; Filtering of contact overtravel S1: The calculated contact overtravel S1 value is discrete. When the contactor's contact closing and breaking times reach m times, the median S1(n) of the m groups of calculated contact overtravel S1 data is taken. After every m breaking times, a recursive numerical filtering calculation is performed. The contact overtravel S1 (n+1) filtering algorithm formula is: S1(n+1)=S1(n-1)*k+S1(n)*(1-k) (3) Where: k is the filter coefficient, and its value is between 0 and 1; S1(n-1) is the calculation result of the last filtering; S1(n) is the median value of the sorted S1 data of the m contact overtravels in this round.
[0023] In actual work, if the total mass m of the movable parts of the contactor, such as the moving contact, contact bracket, shaft, and moving iron, is 3.27kg, the travel difference S3-S2 between the travel switch 11 and the travel switch 12 is 10mm, and the elastic coefficient k1 of the contact spring is 2400N / m. When the contactor is inspected at the factory, the contact overtravel is measured to be 8.2mm, and the time difference t between the travel switch 11 and the travel switch 12 is determined to be 38.854ms after filtering after 100 action data. The theoretical contact overtravel is calculated to be 9.5mm, and the correction value c is -1.3mm, which is saved in the microcontroller.
[0024] After the contactor has been running for a period of time, the contacts will produce electrical wear. The signal detection module measures the time t to be 70.984ms. After calculation, the electrical wear of the contactor is 4.2mm and the contact overtravel is 4mm, which has reached the critical point of life. The signal detection module sends a light alarm signal through the alarm circuit to remind the user to replace the contactor.
[0025] The present invention provides two left-side travel switches and a right-side travel switch, and the travels of the two travel switches are different. When the contacts are disconnected, the shaft linked with the contacts will sequentially trigger the two travel switches. By detecting the time difference t between the two travel switches, the contact overtravel of the contactor can be calculated using a formula. When the contact overtravel is less than a predetermined value, it is considered that the contact wear has reached a critical point, and an alarm signal is sent to the user through the alarm circuit.
[0026] The above are only preferred embodiments of the present invention. It should be noted that for those skilled in the art, under the technical enlightenment provided by the present invention, other equivalent variations and improvements can also be made, which should also be regarded as the protection scope of the present invention.
Claims
1. A contactor contact electrical wear detection device, characterized in that: The invention comprises a signal detection module (2) mounted on the upper surface of a contactor housing (1), the signal detection module (2) comprising a left travel switch (12) and a right travel switch (11), the two travel switches being connected to a microcontroller, the top ends of the left travel switch (12) and the right travel switch (11) being provided with a driving rod with the front end tilted in the same direction, the top end position of the left driving rod (14) being lower than the top end position of the right driving rod (13), the top end of the driving rod being provided with a contact shaft (5), the left and right ends of the contact shaft (5) respectively passing through the mounting holes at the top of a contact bracket (6) of the contactor, and the lower part of the contact bracket (6) passing through the housing ( 1) is connected to the moving contact (7), a contact spring (9) is installed at the bottom of the moving contact (7), a reaction spring (10) is installed at the bottom of the moving contact (7), the contact shaft (5) is connected to one end of a clamping handle (16), the other end of the clamping handle (16) is fixed to the side walls of both sides of the moving magnet (4), a static magnet (15) fixed to the upper surface of the housing (1) is arranged below the moving magnet (4), and a coil (3) is installed between the moving magnet (4) and the static magnet (15); the distance between the top end of the left driving rod (14) and the top end of the right driving rod (13) is smaller than the distance between the moving contact (7) and the static contact (8) when the contactor leaves the factory.
2. The detection device according to claim 1, characterized in that: The microcontroller is connected with the alarm circuit.
3. A method for calculating contactor overtravel, which is implemented according to the contactor electrical wear detection device according to claim 1 or 2, and is characterized in that: When the coil (3) is energized, the moving magnet (4) moves downward and is attracted by the static magnet (15). The moving magnet (4) drives the contact bracket (6) and the moving contact (7) to move downward together through the contact shaft (5). The moving contact (7) and the static contact (8) are closed. During the movement, the contact shaft (5) sequentially contacts the top of the right driving rod (13) and the top of the left driving rod (14). The two travel switches are closed successively, and the travel switch closing signal is transmitted to the microcontroller. When the coil (3) loses power, the moving magnet (4) and the static magnet (15) are disconnected, and the moving contact (7) and the static contact (8) are disconnected at the same time. The moving contact (7) is closed in the contact spring. The moving contact (7) moves upwards at an acceleration of a1 under the combined action of the contact spring (9) and the reaction spring (10). When the contact spring (9) is fully extended, the moving contact (7) continues to move upwards only under the action of the reaction spring (10) at an acceleration of a2. The contact bracket (6) moves upwards with the moving contact (7) and successively separates from the top of the left driving rod (14) and the top of the right driving rod (13). The left travel switch (12) opens at time t2 and the right travel switch (11) opens at time t3. The travel difference between the two travel switches is s, and the action time difference is t3-t2. The contact overtravel S1 of the moving contact (7) is calculated as follows: （1） Where: k1 is the elastic coefficient of the contact spring; S2 is the movement stroke of the left travel switch (12) from the start of movement of the contact support (6) to the opening of the travel switch (12); S3 is the movement stroke of the right travel switch (11) from the start of movement of the contact support (6) to the opening of the travel switch (11); t=t3-t2, is the action time difference between the left travel switch (12) and the right travel switch (11); m is the total mass of the moving contact (7), the contact support (6), the contact spring (9), the shaft (5), and the moving magnet (4).
4. The calculation method according to claim 3, characterized in that: In the formula (1), according to the machining accuracy of parts, the errors of k1, k2, S2, S3, and m, the value of k1 is much larger than the value of k2. The estimated deviation is corrected by using the contact overtravel data measured mechanically during the contactor production stage. The simplified and corrected calculation formula of the contact overtravel is as follows: （2） Where c is the correction value.
5. The calculation method according to claim 3 or 4, characterized in that: The contact overtravel S1 of the moving contact (7) is filtered: The calculated contact overtravel S1 value is discrete. When the contactor's contact closing and breaking times reach m times, the median S1(n) of the m groups of calculated contact overtravel S1 data is taken. After every m breaking times, a recursive numerical filtering calculation is performed. The contact overtravel S1 (n+1) filtering algorithm formula is: S1(n+1)=S1(n-1)*k+S1(n)*(1-k) (3) Where: k is the filter coefficient, and its value is between 0 and 1; S1(n-1) is the calculation result of the last filtering; S1(n) is the median value of the sorted S1 data of the m contact overtravels in this round.