Method and device for detecting oil corrosion resistance of enameled copper wire

Abstract

The invention relates to the technical field of corrosion detection, and discloses a method and a device for detecting the oil corrosion resistance of enameled copper wires, and the method comprises the following steps: selecting two enameled copper wires, removing a coating layer on one enameled copper wire, weighing the two enameled copper wires respectively, and bending the two enameled copper wires into U shapes with the same size; respectively communicating the two enameled copper wires with a power supply, and then immersing the enameled copper wires into a tank body filled with oil liquid; heating and stirring the oil liquid, and switching on a power supply; after the test is finished, oil on the two enameled copper wires is cleaned up, weighing is carried out again, and the weight change rate before and after is calculated; then the two enameled copper wires are observed by using amplification observation equipment; when the weight change rate of the enameled copper wire of which the coating layer is not removed is less than or equal to 1%, the weight change rate of the enameled copper wire of which the coating layer is removed is less than or equal to 5%, and the bending part is not corroded, the corrosion capability is determined to be good; according to the method and the device, the corrosion resistance of the enamel cover with / without the coating layer can be accurately judged at the same time.

Description

Technical Field

[0001] This invention relates to the field of corrosion detection technology, and in particular to a device and method for evaluating the resistance of enameled copper wire to oil corrosion. Background Technology

[0002] Oil-cooled motors have become the mainstream technology for new energy vehicles due to their higher power density. For effective insulation, the enameled copper flat wire used in oil-cooled motors is typically made by coating the surface of copper flat wire with polyimide or polyamide-imide. However, in actual use, this wire needs to be bent to form a motor hairpin. This bending process can easily create micro-cracks. During actual use, since the enameled copper flat wire is in direct contact with the motor cooling oil, if the polyimide and oil are not compatible, the oil may penetrate the insulation layer or micro-cracks and come into direct contact with the copper body. In this case, the active components in the oil additives may corrode the copper surface, leading to insulation failure. Therefore, a scientific evaluation of the enameled wire's resistance to oil corrosion is crucial.

[0003] Currently, the industry standard for verifying the oil corrosion resistance of enameled wires generally follows the traditional combination of direct immersion followed by high and low temperature shock tests in an environmental chamber: the wire sample is first completely immersed in a specified oil solution, then subjected to a pre-set high and low temperature shock test; after the cycle, the sample is removed, and inspectors visually observe whether the enameled copper wire shows signs of cracking or corrosion. This entire process lacks quantitative indicators, the judgment results heavily rely on personal experience, are highly subjective, and make it difficult to accurately distinguish between minor damage and early failure. This method can no longer meet the increasingly stringent requirements of high-end motors and new energy vehicle drive systems. Summary of the Invention

[0004] This invention proposes a method and apparatus for testing the corrosion resistance of enameled copper wire to oil, thereby overcoming the shortcomings of the prior art. The apparatus and method can accurately distinguish between minor damage and early failure caused by corrosion in enameled copper wire without the influence of human subjective factors.

[0005] The technical solution of this invention is: a method for testing the oil corrosion resistance of enameled copper wire, comprising the following steps: Select two enameled copper wires of the same length, remove the coating layer from one of the enameled copper wires, weigh the two enameled copper wires separately, and bend them into U-shapes of the same size. Connect the two enameled copper wires to the power supply respectively, then immerse the two enameled copper wires in a tank containing oil, and seal the tank. The oil in the tank is heated, the power is turned on, and the oil in the tank is stirred. After the test, the two enameled copper wires are removed and the oil on the two enameled copper wires is cleaned. After the test, the two enameled copper wires were weighed again, and the rate of change of weight of the two enameled copper wires relative to before the test was calculated; then, the bending points of the two enameled copper wires were observed using a magnified observation device. When the weight change rate of the enameled copper wire without removing the coating is ≤1%, the weight change rate of the enameled copper wire with the coating removed is ≤5%, and there is no corrosion at the bend, its corrosion resistance is considered good.

[0006] In at least one embodiment of the present invention, during the test, the oil in the tank is heated to 140°C to 160°C.

[0007] In at least one embodiment of the present invention, the current is set to 4mA to 6mA during the test.

[0008] In at least one embodiment of the present invention, the test duration is maintained for 230h to 250h during the test.

[0009] In at least one embodiment of the present invention, after the test, the two enameled copper wires are cleaned with NY-120 solvent gasoline and the two enameled copper wires are dried with oil-absorbing paper, and then weighed and their microstructure is observed.

[0010] In at least one embodiment of the present invention, the weight of the two enameled copper wires is accurate to 0.1 mg before and after the test.

[0011] In at least one embodiment of the present invention, the observation device of the method is a scanning electron microscope (SEM). During observation, the accelerating voltage of the SEM is 15±5kV, the electron beam current is 100±10μA, and the magnification is 400~600 times.

[0012] In at least one embodiment of the present invention, the invention includes: a tank, a sealing cap, two pairs of terminal blocks, a heating tube, and an electromagnetic stirrer. The tank is used to hold oil. The sealing cap is detachably connected to the tank. Two terminal blocks are disposed opposite to each other on the sealing cap. Multiple terminals are respectively provided opposite to each other on the two terminal blocks above and below the sealing cap. The heating tube is wound around the side wall of the tank and is used to heat the oil in the tank. The electromagnetic stirrer is disposed at the bottom of the inner cavity of the tank and is used to stir the oil in the tank.

[0013] Compared with the prior art, the beneficial effects of the present invention are: This invention proposes a method for testing the oil corrosion resistance of enameled copper wire. The method involves dividing the enameled copper wire into two types: one with a coating and one without. Each type is weighed, bent into the same shape, and immersed in a sealed tank containing oil. The oil is then heated, the power supply to the enameled copper wire is connected, and the oil is stirred. After the test, both enameled copper wires are removed and cleaned. They are then weighed again, and the weight change rate relative to the initial value is calculated. A magnified observation device is then used to observe the bends of the two wires. If the weight change rate of the enameled copper wire without the coating removed is ≤1%, the enameled copper wire with the coating removed is considered safe. When the weight change rate is ≤5% and there is no corrosion at the bend, the corrosion resistance is considered good. Compared with the existing method of oil bath immersion and visual inspection, this method can simultaneously test the oil corrosion resistance of enameled wire with and without coating. The testing environment of enameled copper wire is more in line with its actual use environment, ensuring the reliability of the test results. Furthermore, by using the weight change rate as the evaluation standard through the weighing method, the corrosion resistance test has a more accurate quantitative indicator. At the same time, the use of magnification equipment to observe the micro-corrosion morphology on the surface of the copper wire is scientific and precise, completely eliminating the influence of subjective factors, in order to meet the increasingly stringent requirements of high-end motors and new energy vehicle drive systems. Attached Figure Description

[0014] Fig. 1 This is a flowchart of the method of the present invention.

[0015] Fig. 2 This is a cross-sectional view of the device of the present invention.

[0016] Fig. 3 This is a top view of the device of the present invention.

[0017] Explanation of reference numerals in the attached figures: 1. Enameled copper wire; 2. Tank body; 3. Sealing cap; 4. Terminal block; 5. Heating element; 6. Electromagnetic stirrer. Detailed Implementation

[0018] The accompanying drawings in this invention are not strictly drawn to scale, and the specific dimensions and quantity of each structure can be determined according to actual needs. The drawings described in this invention are merely structural schematic diagrams.

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "inner," "outer," "upper," "lower," "far," "near," "front," and "rear" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0021] Combination Figs. 1-2 As shown, a method for evaluating the oil corrosion resistance of enameled copper wire includes the following steps: Two enameled copper wires 1 of the same length are selected. The coating layer on one of the enameled copper wires 1 is removed. The two enameled copper wires 1 are weighed separately and bent into U-shapes of the same size. In this embodiment, each enameled copper wire 1 is 20cm long. The weighing mass of the enameled copper wire 1 without removing the coating layer and the enameled copper wire 1 with the coating layer removed are recorded as M1 and M2, respectively.

[0022] Connect the two enameled copper wires 1 to the power supply respectively, then immerse the two enameled copper wires 1 into the tank 2 containing oil, and seal the tank 2.

[0023] The oil in tank 2 is heated, the power supply to the two enameled copper wires 1 is turned on, and the oil in tank 2 is stirred. After the test, the two enameled copper wires 1 are removed, the oil on the two enameled copper wires 1 is cleaned, and the two enameled copper wires 1 are kept dry.

[0024] After the test, the two enameled copper wires 1 were weighed again. The weights of the enameled copper wire 1 with and without the coating were recorded as M3 and M4, respectively. Then W was calculated. t1 % = (M3 - M1) / M1, W t2 % = (M4 - M2) / M2; then, magnified observation equipment was used to observe the bends of the two enameled copper wires 1.

[0025] When W t1 %≤1% and W t2 When the corrosion rate is ≤5% and there is no corrosion at the bend, the enameled copper flat wire is considered to have good corrosion resistance. Using the gravimetric method with the rate of weight change as the evaluation standard provides a more precise quantitative indicator for corrosion resistance testing. Furthermore, using magnification equipment to observe the microscopic corrosion morphology on the copper wire surface is scientific and accurate, completely eliminating the influence of subjective factors.

[0026] As an alternative embodiment, during the test, the oil in tank 2 is heated to 140°C~160°C, preferably 150°C. Generally, the maximum operating temperature of a motor is limited to 150°C. This embodiment selects the most stringent temperature to carry out the experiment, which is closer to the actual use and ensures the reliability of the test results.

[0027] As an alternative embodiment, the current is 4mA to 6mA during the test, preferably 5mA. The 5mA current can maintain slight cathodic polarization, inhibit the anodic dissolution of the copper substrate, and at the same time will not cause electrochemical degradation of the varnish film, thereby delaying the erosion of the enameled copper wire by the corrosive medium in the oil without damaging the insulation layer.

[0028] As an alternative embodiment, the testing period is maintained at 230h~250h, preferably 240h. 240h is the optimal testing time. If the testing time is too long, the test cost will increase. If the testing time is too short, the change in corrosion weight will not be obvious and it will be difficult to make a direct judgment.

[0029] As an alternative embodiment, after the test, the two enameled copper wires 1 were cleaned with NY-120 solvent gasoline and then dried with absorbent paper before weighing and observing the method. The above cleaning method can remove the oil adhering to the enameled copper wires 1 more quickly and thoroughly, ensuring the accuracy of the weighing results after the experiment.

[0030] As an alternative embodiment, the two enameled copper wires 1 are weighed to an accuracy of 0.1 mg before and after the test to ensure detection accuracy.

[0031] As an alternative embodiment, the observation equipment used in this method is a scanning electron microscope (SEM). During observation, the accelerating voltage of the SEM is 15±5 kV, the electron beam current is 100±10 μA, and the magnification is 400x to 600x, preferably 500x. These parameters represent the optimal instrument parameters for clearly observing the morphology of the copper wires.

[0032] This invention also proposes a device for evaluating the corrosion resistance of enameled copper wire to oil, characterized by comprising: a tank 2, a sealing cover 3, two pairs of terminal blocks 4, a heating tube 5, and an electromagnetic stirrer 6. The tank 2 is used to hold oil, and the sealing cover 3 is detachably connected to the tank 2, used to completely seal the tank 2 during testing. The two terminal blocks 4 are respectively installed on the sealing cover 3. Multiple terminals are respectively provided on the two terminal blocks 4 above and below the sealing cover 3. The heating tube 5 is wound around the side wall of the tank 2, and is used to heat the oil in the tank 2. The electromagnetic stirrer 6 is installed in the tank 2, and is used to stir the oil in the tank 2 to make the oil temperature uniform. Specifically, the tank 2 is a circular tank.

[0033] The above embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit them. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions implemented in the present invention, and should all be covered within the protection scope of the present invention.

Claims

1. A method for testing the oil corrosion resistance of enameled copper wire, characterized in that, Includes the following steps: Select two enameled copper wires of the same length, remove the coating layer from one of the enameled copper wires, weigh the two enameled copper wires separately, and bend them into U-shapes of the same size. Connect the two enameled copper wires to the power supply respectively, then immerse the two enameled copper wires in a tank containing oil, and seal the tank. The oil in the tank is heated, the power supply to the two enameled copper wires is turned on, and the oil in the tank is stirred. After the test, the two enameled copper wires are removed and the oil on the two enameled copper wires is cleaned. After the test, the two enameled copper wires were weighed again, and the rate of change of weight of the two enameled copper wires relative to before the test was calculated. Then, magnified observation equipment was used to observe the bends of the two enameled copper wires; When the weight change rate of the enameled copper wire without removing the coating is ≤1%, the weight change rate of the enameled copper wire with the coating removed is ≤5%, and there is no corrosion at the bend, its corrosion resistance is considered good.

2. The method for testing the oil corrosion resistance of enameled copper wire as described in claim 1, characterized in that, During the test, the oil in the tank was heated to 140°C~160°C.

3. The method for testing the oil corrosion resistance of enameled copper wire as described in claim 1, characterized in that, During the test, the current was set to 4mA~6mA.

4. The method for testing the oil corrosion resistance of enameled copper wire as described in claim 1, characterized in that, During the testing process, the testing time is maintained at 230h~250h.

5. The method for testing the oil corrosion resistance of enameled copper wire as described in claim 1, characterized in that, After the test, the two enameled copper wires were cleaned with NY-120 solvent gasoline and then dried with absorbent paper. After that, the weight was measured and the microstructure was observed.

6. The method for testing the oil corrosion resistance of enameled copper wire as described in claim 1, characterized in that, When weighing the two enameled copper wires before and after the test, the weight was accurate to 0.1 mg.

7. The method for testing the oil corrosion resistance of enameled copper wire as described in claim 1, characterized in that, The observation equipment used in this method is a scanning electron microscope (SEM). During observation, the accelerating voltage of the SEM is 15±5kV, the electron beam current is 100±10μA, and the magnification is 400~600 times.

8. The device for testing the oil corrosion resistance of enameled copper wire as described in claim 1, characterized in that, include: The tank is used to hold oil. The sealing cap is detachably connected to the tank body; Two terminal blocks are mounted opposite each other on the sealing cover; multiple terminal posts are respectively provided on the two terminal blocks above and below the sealing cover. Heating tubes are wound inside the side wall of the tank to heat the oil inside the tank. An electromagnetic stirrer is installed inside the tank to stir the oil inside the tank.

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