Technical Field

[0001] The present invention relates to an electrically insulating coating for insulating an electrical conductor. For example, an insulating coating for insulating a copper wire. The present invention further relates to a method of coating an electrically insulating coating for insulating an electrical conductor. For example, a method of coating an electrically insulating coating for insulating a copper wire.

Background

[0002] Copper has been known to be a good electrical conductor. Copper wires and strips are commonly used as electrical conductors and contacts in many electrical applications such as power generation, power transmission, power distribution, telecommunication, electronic circuitry, electronic appliances and equipment, etc.

[0003] Typically, the copper wire or strip is being insulated by a layer of PVC (polyvinyl chloride) or rubber. The layer of PVC or rubber is being coated onto the surface of the copper wire or strip. For electromagnetic applications such as transformers, inductors, motors, speakers, hard disk head actuators, electromagnets, etc, copper wires are insulated (also known as enameled) using a thin layer of polyvinyl formal (Formvar), polyurethane, polyamide, polyester, polyester-polyimide, polyamide-polyimide (or amide- imide), and polyimide. For these enameled wires, the thin insulation layer is typically about 150-200 pm thick, and the operating temperature is typically limited to 200°C. This is because the polymer insulation layer will melt at temperature higher than 200°C. This temperature limitation essentially restricts the electrical load carrying capacity of the copper wire and thus limits the performance of the electromagnetic device.

[0004] Furthermore, due to the operating environment of the copper wire or strips, the coating 100 has to be hard to withstand wear and tear and at the same time, it has to be flexible to allow the copper wire or strips to be laid and be installed in the tight-spaced casing of the device. [0005] Therefore, in order to increase the electrical load carrying capacity of the copper wire to improve the performance of the electromagnetic device, a coating that is able to withstand a higher melting temperature, e.g. higher than 200°C and is able to electrically insulate the copper wire or strip is required. Furthermore, the coating should be relatively hard and yet flexible. In addition, preferably, the manufacturing costs of the copper wire or strip should be relatively low to make if affordable for such wires to be used.

[0006] It is the object of this invention to provide electrical insulation coating 100 that has the abovementioned properties.

Summary

[0007] According to various embodiments, the present invention relates to an electrically insulating coating for insulating an electrical conductor. The coating includes a first layer adapted to be deposited onto the electrical conductor, the first layer comprising A1203, and a second layer adapted to be formed onto the first layer, the second layer comprising Si02.

[0008] According to various embodiments, the first layer has a thickness of 100-200nm.

[0009] According to various embodiments, the second layer has a thickness of 1 -2pm

[0010] The present invention further relates to a method of coating an electrically insulating coating for insulating an electrical conductor. The method includes depositing a first layer onto the electrical conductor, the first layer comprises A1203, and forming a second layer onto the first layer, the second layer comprises Si02.

[0011] According to various embodiments, depositing the first layer includes depositing using atomic deposition method.

[0012] According to various embodiments, the method may further include passing the electrical conductor through a precursor solution comprising polysilazane. [0013] According to various embodiments, the precursor solution may further include perhydropolisilazane.

[0014] According to various embodiments, the method may further include passing the electrical conductor at a pre-determined speed through the precursor solution having a pre determined concentration, such that the method further comprises varying the pre-determined speed of the electrical conductor.

[0015] According to various embodiments, the method may further include varying the length of the electrical conductor through the precursor solution.

[0016] According to various embodiments, the method may further include curing the second layer at a temperature between 25°C and 200°C.

[0017] According to various embodiments, the method may further include curing the second layer for at least six hours.

Brief Description of Drawings

[0018] Fig. 1 shows a sectional view of an exemplary embodiment of an electrically insulating coating for insulating a electrical conductor.

[0019] Fig. 2 shows a method of coating an electrically insulating coating on an electrical conductor.

[0020] Fig. 3 shows a sectional view of an exemplary embodiment of an apparatus for the coating the second layer.

Detailed Description

[0021] Fig. 1 shows a sectional view of an exemplary embodiment of an electrically insulating coating 100 for insulating an electrical conductor 10. Coating 100 includes a first layer 110 adapted to be deposited onto the electrical conductor 10, the first layer 110 includes AI2O3, and a second layer 120 adapted to be formed onto the first layer 110, the second layer 120 includes S1O2. Electrical conductor 10 may include a wire, a connector, a strip, etc. For example, the coating 100 may be used for a copper wire, a copper strip or electrical conducting elements in any form, shape and size.

[0022] First layer 110 may be deposited onto the electrical conductor 10 using a deposition method, e.g. atomic deposition method or Atomic Layer Deposition method. First layer 110 may be deposited directly onto the electrical conductor 10 such that the first layer 110 is in contact with the electrical conductor 10. Second layer 120 may be formed onto the first layer 110 by dip coating method. Second layer 120 may be formed directly onto the first layer 110. Second layer 120 may be coated and cured onto the first layer 110. Second layer 120 may function as a protective film. First layer 110 may have a thickness of 100-200nm. Second layer 120 may have a thickness of 1-2 pm. Coating 100 is able to insulate the electrical conductor 10 electrically. Coating 100 may insulate the electrical conductor 10 with a breakdown voltage of about 40V. Coating 100 is able to withstand a high temperature, e.g. higher than 200°C. Coating 100 may withstand an operating temperature of up to 500°C. Due to the material property of the coating 100, the coating 100 is relatively harder than conventional polymer sheath, e.g. PVC, and rubber sheath. In addition, due to the thickness (or thinness) of the coating 100, it is flexible and easy to be bent. Conventional insulation sheave would not have been able to achieve the properties mentioned, e.g. good electrical insulation, high operating temperature, at the same thickness of the coating 100. In this way, the electrical conductor 10 with the coating 100 can be used in many applications, such as automobile, train, building, etc. as a protective coating 100. In addition, with the reduction in the thickness of the coating 100, the size of the devices, e.g. transformers, inductors, motors, speakers, hard disk head actuators, electromagnets, etc., that use such electrical conductor 10, e.g. copper wire as windings, may be significantly reduced.

[0023] Fig. 2 shows a method 2000 of coating 100 an electrically insulating coating 100 on an electrical conductor 10. Method 2000 includes depositing a first layer 110 onto the electrical conductor 10 in block 2100. First layer 110 includes AI2O3. Method 2000 includes forming a second layer 120 onto the first layer 110 in block 2200. Second layer 120 includes SiCh. [0024] Fig. 3 shows a sectional view of an exemplary embodiment of an apparatus 302 for coating the second layer 320 (not shown in Fig. 3), e.g. SiC . As mentioned earlier, the first layer 310 (not shown in Fig. 3) may be deposited onto the electrical conductor 10 using the atomic deposition method or any suitable method. For other conductors, a suitable coating method may be used, e.g. painting, adhesion. Second layer 320 may be formed onto the first layer 310 by dipping coating method or any other suitable known methods. Electrical conductor 10, with the first layer 310, may be passed through a precursor solution 332 comprising polysilazane. Precursor solution 332 may include perhydropolisilazane. Referring to Fig. 3, the apparatus 302 may include a tank 330 for containing the precursor solution 332 and a conveyor 340 for conveying the electrical conductor 10 through the precursor solution 332. Conveyor 340 may include a plurality of conveying elements 342, e.g. pulleys, for conveying the electrical conductor 10 through the precursor solution 332. Conveying elements 342 may be submerged within the precursor solution 332. As shown in Fig. 3, the electrical conductor 10 may only be deposited with the first layer 310 at portion 10 A. As the electrical conductor 10 with the first layer 310 is being conveyed into the precursor solution 332 by the conveyor 340, it is gradually being coated with the second layer 320 as it passes through the precursor solution 332. As the electrical conductor 10 is being conveyed out of the precursor solution 332, the electrical conductor 10 with the first layer 310 may be coated with the second layer 320 at the required thickness at portion 10B. Using the polysilazane solution as the precursor solution 332, a thin layer of SiCh may be formed or coated onto the first layer 310.

[0025] Precursor solution 332 may include a solvent and polysilazane in its composition. The composition of the precursor solution 332 may be expressed as,

[0026] Precursor solution 332 may further include perhydropolysilance in its composition. The composition of the precursor solution 332 may be expressed as, [0027] Typically, the concentration of polysilazane and perhydropolysilazane, i.e. X+Y%, may be less than 10%. The thickness of the coating 100 after curing may vary with the travel speed.

[0028] Electrical conductor 10 may pass through the precursor solution 332 having a pre determined concentration at a pre-determined speed. The speed of the electrical conductor 10 may be dependent on the thickness of coating 300 required. The thickness of the coating 300 on the electrical conductor 10 may be varied. As such, the per-determined speed of the electrical conductor 10 may be varied accordingly. The variables used to control the thickness of the second layer 320 on the first layer 310 may depend on the duration of the electrical conductor 10 being submerged in the precursor solution 332, i.e. the dipping time, and the composition of the precursor solution 332, e.g. the concentration of the solute, e.g. polysilazane, of the precursor solution 332. The duration may be the time taken from the time the electrical conductor 10 enters the precursor solution 332 to the time the electrical conductor 10 exits the precursor solution 332. The duration may be affected by the conveying speed of the electrical conductor 10 through the precursor solution 332, i.e. the faster the conveying speed, the shorter the duration or dipping time and vice versa. The duration may be affected by the path length of the electrical conductor 10 in the precursor solution 332, i.e. the longer the path length, the longer the duration or dipping time and vice versa. As such, the length of the electrical conductor 10 in the precursor solution 332 may be varied. Referring to Fig. 3, the length of the electrical conductor 10 in the precursor solution 332 may be lengthened if a longer duration for the electrical conductor 10 to be submerged in the precursor solution 332 is required. For example, the distance between the plurality of conveying elements 342 may be increased and/or the number of conveying elements 342 may be increased to deviate the path, e.g. zig-zag arrangement, of the electrical conductor 10 to increase the path length. Depending on the concentration of the solute, the speed of the electrical conductor 10 being conveyed by the conveyor 340 may be determined to achieve a pre-determined thickness of the coating 100 on the electrical conductor 10. The duration or dipping time may be in the range of several hundred seconds, e.g. 100-500 seconds. Once the required thickness is achieved, the second layer 320 may be cured for at least six hours, e.g. 7 hours, 8 hours, and at a temperature between room temperature, e.g. 25°C, and 200°C. The curing temperature may range from 25°C to 100°C. [0029] The present invention relates to an electrically insulating coating and a method of coating the coating generally as herein described, with reference to and/or illustrated in the accompanying drawings.