Enamelled wire, method for producing the same and electric machine

Abstract

The present disclosure relates to an enameled wire, a preparation method thereof and a motor, the enameled wire comprising a conductor and a first varnish layer, a second varnish layer and a third varnish layer successively covering the conductor; the first varnish layer and the third varnish layer are of the same material, and the first varnish layer and the second varnish layer are of different materials. The present disclosure simplifies the complexity of varnish and preparation process, can effectively reduce the loss of varnish in the production process, reduce the production cost, and the enameled wire has good performance in heat resistance, corona resistance and PDIV performance.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an enameled wire, a preparation method thereof and a motor. BACKGROUND

[0002] During long-term operation, the motor gradually ages due to the combined effects of electric field, thermal field, mechanical force and environmental factors, eventually leading to the degradation of insulation performance and breakdown. In the field of new energy electric vehicles, the power density demand of the electric drive system is increasing, and the drive motor is developing towards high speed, high efficiency, high voltage and oil cooling. With the introduction of the 800V high-voltage platform for new energy electric vehicles, the initial partial discharge inception voltage (PDIV) of the motor insulation at some local positions will be significantly reduced under some extremely harsh high-altitude and high-temperature working conditions. Under the action of high dv / dt pulse voltage, once the maximum voltage borne by the inter-winding insulation exceeds the PDIV of the insulation at the corresponding position, partial discharge will occur, thereby causing electrical aging.

[0003] As an important component of the motor insulation system, the performance of the enameled wire is crucial. In order to ensure the high efficiency of the electric drive system and improve the power density, it is necessary to limit the thickness of the paint film of the enameled wire, and the enameled wire for 800V and above high-voltage platforms needs to have both high PDIV performance and corona resistance. The paint layer in the traditional enameled wire structure is usually made of more than three kinds of multi-paint formulations, which has high complexity of paint formulation and process and high production loss, and is difficult to meet the performance requirements of the high-voltage platform in terms of heat resistance, corona resistance and PDIV performance. SUMMARY

[0004] The purpose of the present disclosure is to provide an enameled wire with simple paint formulation and excellent performance, a preparation method thereof and a motor.

[0005] To achieve the above-mentioned purpose, the first aspect of the present disclosure provides an enameled wire, comprising a conductor and a first paint layer, a second paint layer and a third paint layer successively coated on the conductor; wherein the materials of the first paint layer, the second paint layer and the third paint layer are independently selected from at least one of modified or unmodified polyamide-imide, modified or unmodified polyamide and modified or unmodified polyether-imide; the materials of the first paint layer and the third paint layer are the same, and the materials of the first paint layer and the second paint layer are different.

[0006] Optionally, the modification methods of the polyamide-imide, the polyamide and the polyether-imide are independently selected from at least one of adhesion modification, corona resistance modification, oil resistance modification, hydrolysis resistance modification, heat resistance modification, wear resistance modification and chemical resistance modification.

[0007] Optionally, the first varnish layer and the third varnish layer are made of oil-resistant and hydrolysis-resistant modified polyimide respectively.

[0008] The second varnish layer is made of corona-resistant modified polyimide.

[0009] Optionally, the thickness of the first varnish layer is 0.01-0.02 mm, the thickness of the second varnish layer is 0.04-0.10 mm, and the thickness of the third varnish layer is 0.03-0.08 mm.

[0010] The total thickness of the first varnish layer, the second varnish layer and the third varnish layer is 0.08-0.20 mm.

[0011] Optionally, the partial discharge inception voltage of the enameled wire is not less than 1100 Vrms, the breakdown voltage is not less than 10 kV, the corona-resistant life is 100-500 hours, and the partial discharge inception voltage and the breakdown voltage after the ATF oil resistance test for 2000 hours are not less than 90% of the initial values.

[0012] In a second aspect of the present disclosure, a method for preparing the enameled wire of the first aspect of the present disclosure is provided, which comprises:

[0013] obtaining a conductor, a first varnish, a second varnish and a third varnish; wherein the first varnish, the second varnish and the third varnish each independently contain at least one of modified or unmodified polyamide-imide, modified or unmodified polyimide and modified or unmodified polyether-imide; the first varnish and the third varnish are the same, and the first varnish and the second varnish are different;

[0014] sequentially coating the first varnish, the second varnish and the third varnish on the outer surface of the conductor and curing to form a first varnish layer, a second varnish layer and a third varnish layer successively covering the conductor.

[0015] Optionally, the solid content of the first varnish is 22-32 wt%, the solid content of the second varnish is 22-38 wt%, the solid content of the third varnish is 22-32 wt%, and / or,

[0016] The viscosity of the first varnish at 20℃ is 7000-30000 mPa·s, the viscosity of the second varnish at 20℃ is 7000-32000 mPa·s, and the viscosity of the third varnish at 20℃ is 7000-30000 mPa·s.

[0017] Optionally, the coating amount of the first varnish is 1-3 passes, the coating amount of the second varnish is 15-28 passes, and the coating amount of the third varnish is 6-25 passes.

[0018] Optionally, the curing conditions include: an evaporation temperature of 300-400℃, a curing temperature of 350-580℃, a line speed of 8-15m / min, and a curing time of 50-120min.

[0019] In a third aspect of the present disclosure, an electric motor is provided, which comprises the enameled wire of the first aspect of the present disclosure.

[0020] With the above technical solution, in the enameled wire of the present disclosure, the material of the first and third layers is the same, and the material of the second layer is different, that is, only two kinds of varnish are used in the three layers of varnish, which advantageously simplifies the complexity of varnish types and preparation process, effectively reduces the loss of varnish in the production process, reduces the production cost, and the enameled wire has good performance in heat resistance, corona resistance and PDIV performance.

[0021] Other features and advantages of the present disclosure will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings are included to provide a further understanding of the present disclosure and constitute a part of the specification, and together with the following specific embodiments, serve to explain the present disclosure but do not constitute a limitation thereof. In the drawings:

[0023] Figure 1 is a structural schematic diagram of an enameled wire according to a specific embodiment of the present disclosure.

[0024] Explanation of reference signs

[0025] 1 - conductor, 2 - first varnish layer, 3 - second varnish layer, 4 - third varnish layer. DETAILED DESCRIPTION

[0026] The specific embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and do not limit the present disclosure.

[0027] In a first aspect of the present disclosure, an enameled wire is provided, referring to Figure 1 , comprising a conductor 1 and a first varnish layer 2, a second varnish layer 3 and a third varnish layer 4 successively coated on the conductor 1. Wherein the material of the first varnish layer 2, the second varnish layer 3 and the third varnish layer 4 is independently selected from at least one of modified or unmodified polyamide-imide, modified or unmodified polyimide and modified or unmodified polyetherimide; the material of the first varnish layer 2 and the third varnish layer 4 is the same, and the material of the first varnish layer 2 and the second varnish layer 3 is different.

[0028] The traditional enameled wire needs to use more than three multi-enameled formula schemes, so that the feeding complexity on the production line is high, multiple enameled pipelines and multiple enameled tanks need to be set to prevent mixing and pollution between different enamels, and the enameled loss is high. The enameled wire of the present disclosure uses only two enamels in the three enameled layers, which advantageously reduces the number of enameled types, thereby reducing the number of enameled pipelines and enameled tanks on the production line, simplifying the equipment layout, while effectively reducing the enameled loss in the production process, reducing the production cost.

[0029] According to the present disclosure, the materials of the first enameled layer 2, the second enameled layer 3 and the third enameled layer 4 can be designed as needed within the aforementioned material type range. Among them, the weight average molecular weight of polyamide-imide (PAI) can be 7000-26000, the weight average molecular weight of polyimide (PI) can be 18000-60000, and the weight average molecular weight of polyetherimide (PEI) can be 5000-21000; according to the UL heat resistance test certification, the heat resistance temperature of the above-mentioned polyamide-imide is above 200dgC, the heat resistance temperature of the above-mentioned polyimide is above 240dgC, and the heat resistance temperature of the above-mentioned polyetherimide is above 180dgC, which can ensure that the enameled wire works stably in high temperature environment for a long time, is not easy to age, and can adapt to the demand of high temperature working conditions such as driving motor.

[0030] Modified polyamide-imide, modified polyimide and modified polyetherimide refer to products obtained by modifying the above-mentioned polyamide-imide, polyimide and polyetherimide through modification methods such as structural modification, component modification or surface modification, in order to further improve the performance. Specifically, the modification method of the polyamide-imide, the polyimide and the polyetherimide can be independently selected from at least one of adhesion modification, corona resistance modification, oil resistance modification, hydrolysis resistance modification, heat resistance modification, wear resistance modification and chemical resistance modification. These modified products can be commercially available goods, or can be prepared by using the modification method in the prior art.

[0031] In an embodiment, the first paint layer 2 and the third paint layer 4 are made of oil and hydrolysis resistant modified polyimide respectively, and the second paint layer 3 is made of corona resistant modified polyimide. The oil and hydrolysis resistant modified polyimide can be at least one selected from fluorinated polyimide and silicone modified polyimide. The corona resistant modified polyimide can be obtained by uniformly dispersing inorganic fillers in a polyimide varnish solution, and the inorganic fillers can be at least one selected from silicon dioxide, aluminum oxide, titanium oxide and chromium oxide. In this case, the first paint layer 2 has good adhesion and oil and water environment resistance, the second paint layer 3 has good corona resistance, and the third paint layer 4 further provides good oil and water environment resistance, which is beneficial to significantly improve the comprehensive performance of the enameled wire.

[0032] In an embodiment, the first paint layer 2 and the third paint layer 4 are made of polyimide respectively, and the second paint layer 3 is made of oil, hydrolysis and corona resistant modified polyimide. The oil, hydrolysis and corona resistant modified polyimide can be obtained by uniformly dispersing inorganic fillers in a fluorinated polyimide varnish solution, and the inorganic fillers can be at least one selected from silicon dioxide, aluminum oxide, titanium oxide and chromium oxide. This embodiment only uses one kind of modified polyimide paint as the second paint layer 3, and the first paint layer 2 and the third paint layer 4 use ordinary polyimide paint, which effectively reduces the cost of the enameled wire.

[0033] The thickness of the first paint layer 2, the second paint layer 3 and the third paint layer 4 can be adjusted within a certain range. Specifically, the thickness of the first paint layer 2 can be 0.01-0.02 mm, the thickness of the second paint layer 3 can be 0.04-0.10 mm, and the thickness of the third paint layer 4 can be 0.03-0.08 mm. Further, in the embodiment where the first paint layer 2 and the third paint layer 4 are made of oil and hydrolysis resistant modified polyimide respectively, and the second paint layer 3 is made of corona resistant modified polyimide, the thickness of the first paint layer 2 can be 0.01-0.015 mm, the thickness of the second paint layer 3 can be 0.05-0.07 mm, and the thickness of the third paint layer 4 can be 0.06-0.08 mm; in the embodiment where the first paint layer 2 and the third paint layer 4 are made of polyimide respectively, and the second paint layer 3 is made of oil, hydrolysis and corona resistant modified polyimide, the thickness of the first paint layer 2 can be 0.012-0.016 mm, the thickness of the second paint layer 3 can be 0.07-0.10 mm, and the thickness of the third paint layer 4 can be 0.03-0.05 mm.

[0034] The enameled wire of the present disclosure has a small number of paint layers, and each paint layer has a small thickness, which is conducive to achieving a low total paint layer thickness and improving the power density of the electric drive system. Specifically, the total thickness of the first paint layer 2, the second paint layer 3 and the third paint layer 4 can be 0.08-0.20 mm.

[0035] The enameled wire of the present disclosure has no special restrictions on the shape and size of the conductor 1. For example, the cross-sectional shape of the conductor 1 can be circular, square, rectangular, etc.; the diameter of the conductor 1 (the maximum size of the conductor 1 in the cross-section) can be 0.5-20 mm, such as 1 mm, 1.5 mm, 3 mm, 5 mm, 8 mm, etc.; the R corner length of the conductor can be 0.1-1 mm, such as 0.3 mm, 0.35 mm, 0.45 mm, etc.

[0036] The enameled wire of the present disclosure has excellent heat resistance, corona resistance and PDIV performance, and can meet the performance requirements of high voltage and oil environment, and meet the development trend of high voltage and oil cooling of the driving motor. Specifically, the partial discharge inception voltage value of the enameled wire can be not less than 1100 Vrms, preferably not less than 1250 Vrms; the breakdown voltage value can be not less than 10 kV, preferably not less than 14 kV; the corona resistance life can be 100-500 hours, preferably 250-500 hours; the partial discharge inception voltage value and the breakdown voltage value after 2000 hours of ATF oil resistance test are both not less than 90% of the initial value, preferably not less than 92%. The partial discharge inception voltage value and the breakdown voltage value can be tested under the measurement standard of 50 Hz sinusoidal alternating current, 100 PC apparent discharge amount (GBT 4074.5 Winding Wire Test Methods Part 5: Electrical Performance); the corona resistance life can be tested in a bipolar square wave voltage environment of 155℃, 4000Vppk, rising edge 100ns, duty cycle 50%, frequency 20kHz (GBT 4074.21 Winding Wire Test Methods Part 21: High Frequency Pulse Voltage Resistance Performance); the ATF oil resistance test can be tested in a sealed ATF oil environment of 155℃, 0.2wt% water.

[0037] In a second aspect, the present disclosure provides a method for preparing the enameled wire of the first aspect of the present disclosure, which comprises the following steps S1-S2:

[0038] S1, obtaining a conductor, a first paint, a second paint and a third paint;

[0039] S2, sequentially coating the first paint, the second paint and the third paint on the outer surface of the conductor and curing to form a first paint layer, a second paint layer and a third paint layer which sequentially cover the conductor.

[0040] In step S1, in order to improve product quality, the method can further include a step of pretreating the conductor, and the pretreatment can include cleaning, annealing, removing oil stains, etc.

[0041] The first paint, the second paint and the third paint are respectively used to form the first paint layer 2, the second paint layer 3 and the third paint layer 4 described above, and each independently contains at least one of modified or unmodified polyamide-imide, modified or unmodified polyimide and modified or unmodified polyether-imide; the first paint and the third paint are the same, and the first paint and the second paint are different, and the specific types can refer to the above description.

[0042] The first paint, the second paint and the third paint are liquid materials containing the above-mentioned polymers, and in addition to the polymer component, they can also contain solvents, modifiers, inorganic fillers and other common components. In order to achieve favorable product performance, the viscosity of the first paint at 20℃ can be 7000-30000 mPa·s, the viscosity of the second paint at 20℃ can be 7000-32000 mPa·s, and the viscosity of the third paint at 20℃ can be 7000-30000 mPa·s. Further, in the implementation where the first paint and the third paint each contain oil-resistant and hydrolysis-resistant modified polyimide, and the second paint contains corona-resistant modified polyimide, the viscosity of the first paint at 20℃ is preferably 12000-20000 mPa·s, the viscosity of the second paint at 20℃ is preferably 15000-22000 mPa·s, and the viscosity of the third paint at 20℃ is preferably 12000-20000 mPa·s; in the implementation where the first paint and the third paint each contain polyimide, and the second paint contains oil-resistant, hydrolysis-resistant and corona-resistant modified polyimide, the viscosity of the first paint at 20℃ is preferably 17000-23000 mPa·s, the viscosity of the second paint at 20℃ is preferably 20000-28000 mPa·s, and the viscosity of the third paint at 20℃ is preferably 17000-23000 mPa·s.

[0043] Further, the solid content of the first paint can be 22-32 wt%, preferably 23-28 wt%; the solid content of the second paint can be 22-38 wt%, preferably 24-30 wt%; and the solid content of the third paint can be 22-32 wt%, preferably 23-28 wt%. Among them, the solid content refers to the weight percentage of the above-mentioned polymer component. By adjusting the viscosity and / or solid content of the paint, it is beneficial to improve the coating effect and promote curing, improve the adhesion and durability of the paint layer, and achieve better comprehensive performance of the product.

[0044] In step S2, the coating and curing can be performed in common equipment in the art. The coating amount of the first paint can be 1-3 passes; the coating amount of the second paint can be 15-28 passes; and the coating amount of the third paint can be 6-25 passes. The curing conditions can be adjusted according to actual needs, wherein the curing time can be adjusted according to the coating amount (i.e. total number of passes), curing furnace height, line speed, curing temperature, and properties of the paint (such as characteristic temperature, etc.).

[0045] For example, the curing conditions can include an evaporation temperature of 300-400°C, a curing temperature of 350-580°C, a line speed of 8-15 m / min, and a curing time of 50-120 min.

[0046] The enameled wire preparation method of the present disclosure is simple to operate and easy to automate, effectively reduces the loss of paint during production, reduces production costs, improves product quality, and the prepared enameled wire has the excellent performance described above.

[0047] In a third aspect, the present disclosure provides an electric machine comprising the enameled wire of the first aspect of the present disclosure.

[0048] The present disclosure is further illustrated by the following examples, but is not intended to limit the present disclosure.

[0049] Example 1

[0050] (1) A soft copper core rod (i.e. conductor) with a diameter of 8 mm enters a continuous extruder through a guide roller, the conductor is made into a flat blank core material through the continuous extruder, and the flat blank core material is made into a flat wire core material with a nominal size of 1.58 mm x 3.7 mm through multiple stretching by a multi-union single die drawing machine; the surface of the flat wire core material is cleaned through an ultrasonic cleaning water tank, and the residual stress between copper grains and surface residual oil are removed through an annealing furnace.

[0051] (2) The first paint and the third paint are oil and hydrolysis resistant modified polyimide paints with a solid content of 26% by weight and a viscosity of 15000 mPa·s at 20°C; the second paint is a corona resistant modified polyimide paint with a solid content of 25% by weight and a viscosity of 18000 mPa·s at 20°C.

[0052] (4) The flat wire core material is pulled into a high-speed continuous drawing and wrapping machine with a DV value of 50-75, 2 passes of the first paint, 16 passes of the second paint, and 21 passes of the third paint are coated, the poly-crystal material is sequentially threaded through the paint coating mold from small to large, and then pulled out, the threading, positioning, and leveling of the paint coating mold are completed, and the paint coating length is 23 meters. Under the conditions of a temperature of 350°C in the oven evaporation zone, a temperature of 510°C in the oven curing zone, and a line speed of 11.5 m / min, the paint coated on the flat wire core material is cured to form a first paint layer, a second paint layer, and a third paint layer, and the curing time is 78 min; after curing, natural cooling in air and particle detection by a photoelectric combined defect detection device are performed, and winding by a take-up machine is performed, and the tightly and uniformly wound enameled wire is obtained.

[0053] The enameled wire prepared in this example has an actual measured size of 1.857 mm x 3.980 mm (narrow side size x wide side size), an actual measured size of the conductor of 1.582 mm x 3.703 mm (narrow side size x wide side size), an average value of the single-sided paint layer thickness outside the conductor of 0.135 mm, an average value of the first paint layer thickness of 0.01 mm, an average value of the second paint layer thickness of 0.06 mm, an average value of the third paint layer thickness of 0.065 mm, and paint loss is counted after one week of continuous production, which is listed in Table 1.

[0054] Example 2

[0055] The enameled wire is prepared according to the method of Example 1, except that in step (2), the first paint and the third paint are polyimide paints with a solid content of 25% by weight and a viscosity of 20,000 mPa·s at 20°C; the second paint is an oil-resistant, hydrolysis-resistant, and corona-resistant modified polyimide paint with a solid content of 28% by weight and a viscosity of 25,000 mPa·s at 20°C; and in step (4), the first paint is coated for 3 passes, the second paint is coated for 28 passes, and the third paint is coated for 6 passes, and the curing conditions are: a temperature of 350°C in the oven evaporation zone, a temperature of 510°C in the oven curing zone, a line speed of 10 m / min, and a curing time of 85 min.

[0056] In the enameled wire prepared in this example, the average value of the single-sided paint layer thickness outside the conductor is 0.14 mm, the average value of the first paint layer thickness is 0.015 mm, the average value of the second paint layer thickness is 0.095 mm, and the average value of the third paint layer thickness is 0.03 mm, and the paint loss is counted after one week of continuous production, which is listed in Table 1.

[0057] Example 3

[0058] The enameled wire was prepared according to the method of Example 1, except that in step (2), the first and third enamels were oil and hydrolysis resistant modified polyimide enamels with a solid content of 32 wt% and a viscosity of 30000 mPa s at 20°C; the second enamel was a corona resistant modified polyimide enamel with a solid content of 38 wt% and a viscosity of 32000 mPa s at 20°C; in step (4), the first enamel was coated for 2 passes, the second enamel was coated for 16 passes, and the third enamel was coated for 21 passes; and the curing conditions were as follows: the temperature of the oven evaporation zone was 330°C, the temperature of the oven curing zone was 490°C, the line speed was 13.5 m / min, and the curing time was 66 minutes.

[0059] In the enameled wire prepared in this example, the average thickness of the single-sided enamel layer outside the conductor was 0.13 mm, the average thickness of the first enamel layer was 0.01 mm, the average thickness of the second enamel layer was 0.06 mm, and the average thickness of the third enamel layer was 0.06 mm. The paint loss was counted after one week of continuous production, and is listed in Table 1.

[0060] Comparative Example 1

[0061] The enameled wire was prepared according to the method of Example 1, except that in step (2), the first enamel was a polyimide enamel with a solid content of 30 wt% and a viscosity of 15000 mPa s at 20°C; the second enamel was a corona resistant modified polyimide enamel with a solid content of 25 wt% and a viscosity of 18000 mPa s at 20°C; the third enamel was an oil and hydrolysis resistant modified polyimide enamel with a solid content of 26 wt% and a viscosity of 15000 mPa s at 20°C; in step (4), the first enamel was coated for 4 passes, the second enamel was coated for 16 passes, and the third enamel was coated for 20 passes; and the curing conditions were the same as in Example 1.

[0062] In the enameled wire prepared in this example, the average thickness of the single-sided enamel layer outside the conductor was 0.13 mm, the average thickness of the first enamel layer was 0.01 mm, the average thickness of the second enamel layer was 0.06 mm, and the average thickness of the third enamel layer was 0.06 mm. The paint loss was counted after one week of continuous production, and is listed in Table 1.

[0063] Comparative Example 2

[0064] The enameled wire was prepared according to the method of Example 1, except that in step (2), the first paint was an adhesion-modified polyamide-imide paint with a solid content of 43 wt% and a viscosity of 12000 mPa·s at 20℃; the second paint was a corona-resistance-modified polyamide-imide paint with a solid content of 43 wt% and a viscosity of 14000 mPa·s at 20℃; the third paint was an oil-resistance and hydrolysis-resistance-modified polyamide-imide paint with a solid content of 37 wt% and a viscosity of 14000 mPa·s at 20℃; in step (4), the first paint was coated for 5 passes, the second paint was coated for 13 passes, and the third paint was coated for 13 passes, and the curing conditions were as follows: the temperature of the oven evaporation zone was 320℃, the temperature of the oven curing zone was 430℃, the line speed was 13.5 m / min, and the curing time was 53 min.

[0065] The enameled wire prepared in the present comparative example had an average thickness of the single-sided paint layer outside the conductor of 0.143 mm, an average thickness of the first paint layer of 0.033 mm, an average thickness of the second paint layer of 0.06 mm, and an average thickness of the third paint layer of 0.05 mm. The paint loss was calculated after one week of continuous production.

[0066] Test Example

[0067] The enameled wires prepared in the examples and comparative examples were tested as follows: the partial discharge inception voltage (PDIV) and the breakdown voltage (BDV) were measured in a 50 Hz sinusoidal AC voltage with a 100 PC apparent discharge amount measurement standard; the corona resistance life was measured in a 155℃, 4000 Vppk, 100 ns rising edge, 50% duty cycle, 20 kHz frequency, bipolar square wave voltage environment; the partial discharge inception voltage and the breakdown voltage of the enameled wire after resistance were measured after 2000 hours of resistance to ATF oil environment test in a sealed environment with 0.2%wt water added, and the results are shown in Table 1.

[0068] Table 1

[0069]

[0070] As can be seen from the results of the examples and comparative examples, the comprehensive performance of the enameled wire prepared in the examples is significantly improved, the paint layer thickness is lower and the paint loss is lower, the PDIV performance and the corona resistance life are better under the unit paint layer thickness, and the oil resistance performance is effectively improved.

[0071] The preferred embodiments of the present disclosure are described in detail above with reference to the drawings, but the present disclosure is not limited to the specific details in the above-described embodiments. Various simple modifications can be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

[0072] It should be further noted that various specific technical features described in the above specific embodiments can be combined in any suitable manner, and the disclosure will not be repeated here for various possible combinations.

[0073] In addition, various different embodiments of the disclosure can also be combined with each other as long as they do not contradict the idea of the disclosure, and they should also be considered as disclosed by the disclosure.

Claims

1. An enameled wire, characterized in that, The device includes a conductor and an enamel layer covering the conductor. The enamel layer is composed of a first enamel layer, a second enamel layer, and a third enamel layer that sequentially cover the conductor. The first enamel layer and the third enamel layer are made of oil-resistant and hydrolysis-resistant modified polyimide, respectively. The second enamel layer is made of corona-resistant modified polyimide. The thickness of the first paint layer is 0.01–0.015 mm, the thickness of the second paint layer is 0.05–0.07 mm, and the thickness of the third paint layer is 0.06–0.08 mm; the total thickness of the first, second, and third paint layers is 0.08–0.20 mm.

2. The enameled wire according to claim 1, wherein, The partial discharge initiation voltage of the enameled wire is not less than 1100Vrms, the breakdown voltage is not less than 10kV, the corona resistance life is 100-500 hours, and the partial discharge initiation voltage and breakdown voltage after 2000 hours of ATF oil resistance test are not less than 90% of the initial values.

3. A method for preparing the enameled wire according to claim 1 or 2, characterized in that, The method includes: Obtain a conductor, a first coating, a second coating, and a third coating; wherein the first coating and the third coating each contain oil- and hydrolysis-resistant modified polyimide, and the second coating contains corona-resistant modified polyimide; The first paint, the second paint, and the third paint are sequentially applied to the outer surface of the conductor and cured to form a first paint layer, a second paint layer, and a third paint layer that sequentially cover the conductor; the first paint is applied in 1 to 3 coats, the second paint in 15 to 28 coats, and the third paint in 6 to 25 coats.

4. The method according to claim 3, wherein, The first paint has a solid content of 22-32% by weight; the second paint has a solid content of 22-38% by weight; the third paint has a solid content of 22-32% by weight; and / or, The viscosity of the first paint at 20°C is 7000–30000 mPa·s, the viscosity of the second paint at 20°C is 7000–32000 mPa·s, and the viscosity of the third paint at 20°C is 7000–30000 mPa·s.

5. The method according to claim 3, wherein, The curing conditions include: evaporation temperature of 300-400℃, curing temperature of 350-580℃, linear speed of 8-15m / min, and curing time of 50-120min.

6. An electric motor comprising the enameled wire as described in claim 1 or 2.

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