A method for manufacturing an involute transformer core

Abstract

The application discloses a manufacturing method of an involute transformer core, which comprises the following steps: S1, cutting a stainless steel silicon steel sheet to obtain a silicon steel sheet blank; S2, using a rolling tool to manufacture the silicon steel sheet blank into an involute silicon steel sheet; S3, stacking a plurality of the involute silicon steel sheets on the periphery of a base cylinder, and tightly holding the involute silicon steel sheets and the base cylinder by using a plurality of stainless steel hoops to form a holding piece, and annealing the holding piece as a whole; S4, bundling; S5, preheating the bundled piece; S6, immersing the preheated bundled piece into insulating paint; S7, solidifying the bundled piece; S8, surface treatment; and S9, gluing, coating epoxy glue on the outer surface of the component which has been surface treated in the step S8, and firmly bonding the component with an epoxy cylinder. The manufacturing method of the involute transformer core provided by the application has single specification of the involute silicon steel sheet, avoids a plurality of specifications of the width of the radial silicon steel sheet, is convenient to manage, and reduces storage devices.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of transformer core manufacturing, and particularly relates to a manufacturing method of a involute transformer core. BACKGROUND

[0002] The transformer core is composed of silicon steel sheets, in order to reduce the heat loss of the core, the core is stacked by silicon steel sheets with thin thickness, the silicon steel sheets used by the transformer have high silicon content, and the two surfaces of the silicon steel sheets are coated with insulating materials, so that the silicon steel sheets stacked together are insulated from each other, and most manufacturers currently adopt a radial lamination mode, since the widths of the silicon steel sheets are inconsistent, the adjacent two radial silicon steel sheets are prone to generate large gaps.

[0003] In order to prevent the core from generating inter-sheet short circuit, the selection of the silicon steel sheet insulating paint is particularly important, with the continuous increase of the capacity of the transformer and the gradual improvement of the heat resistance grade, higher and higher requirements are put forward for the insulation of the core silicon steel sheet, and the performance requirements of the silicon steel sheet insulating paint are also more and more strict. The impregnating paint is divided into two categories of solvent type and solventless type according to the types of solvents, based on the development of the environmental requirements and the VPI impregnation process, in recent years, the development of the solventless impregnating paint is relatively rapid. The high-temperature impregnating paint widely produced in China at present includes diphenyl ether modified impregnating paint, heat-resistant epoxy type impregnating paint, heat-resistant polyester type impregnating paint, unsaturated polyester-imine type impregnating paint and the like.

[0004] Chinese patent application No. 201610591305.3 discloses a high-hanging paint amount impregnated resin for an electric vehicle motor, the patent uses hyperbranched polysiloxane prepared by hydrolysis reaction to improve the hanging paint amount, but research shows that the hyperbranched polysiloxane prepared by hydrolysis condensation method has certain defects, such as being prone to generate various by-products, being not conducive to structure control, and being prone to form non-melting and non-dissolving gel and lose effectiveness.

[0005] Therefore, in the manufacturing process of the transformer core, the heat resistance and insulation of the insulating impregnating paint are crucial to the transformer, and meanwhile, the adhesion performance of the insulating impregnating paint and the silicon steel sheet is also a key to improve the service life of the transformer. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a manufacturing method of an involute transformer core, the manufacturing method of the involute silicon steel sheet is simple, the lamination coefficient is high, and the insulation performance is good, so as to solve the problem that the inconsistent widths of the radial silicon steel sheets easily cause large gaps between the adjacent silicon steel sheets in the prior art.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a manufacturing method of an involute transformer core, comprising the following steps:

[0008] S1, blanking, cutting a stainless steel silicon steel sheet to obtain a silicon steel sheet blank;

[0009] S2, roll forming, using a roll forming tool to form the silicon steel blank into an involute silicon steel sheet;

[0010] S3, inserting and stacking, stacking a plurality of involute silicon steel sheets around the periphery of the base cylinder, and using a plurality of stainless steel hoops to tightly hold the involute silicon steel sheets and the base cylinder to form a tightly held piece, and annealing the tightly held piece as a whole;

[0011] S4, bundling, after the tightly held piece is tightly bundled with iron wire, the stainless steel hoops are separated from the tightly held piece;

[0012] S5, preheating, preheating the bundled piece;

[0013] S6, paint dipping, dipping the preheated bundled piece into insulating paint; in the paint dipping tank, after the workpiece is placed in, it is soaked for 0.5 hours under the condition that the pressure is kept at ≤200 Pa, then pressurized to 0.4 Mpa, and kept for 0.5 hours before taking out;

[0014] S7, curing, curing the bundled piece;

[0015] S8, surface treatment, removing the iron wire on the surface of the bundled piece and shaping the outer surface of the bundled piece after the iron wire is removed;

[0016] S9, glue coating, coating epoxy glue on the outer surface of the part after surface treatment in step S8, and firmly bonding with the epoxy cylinder.

[0017] Preferably, the thickness of the silicon steel blank in step S1 is 0.04-0.1 mm.

[0018] Preferably, the roll forming tool in step S2 is a cylinder, the roll forming tool is provided with a groove, and the two ends of the groove are provided with round corners, and the lengths of the involute silicon steel sheet, the base cylinder and the epoxy cylinder are equal.

[0019] Preferably, the number n of involute silicon steel sheets used in step S3 is calculated as follows: n = outer circumference of base cylinder / thickness of single involute silicon steel sheet.

[0020] Preferably, the preheating temperature in step S5 is 90-120℃.

[0021] Preferably, the preparation method of the insulating paint in step S6 comprises the following steps:

[0022] (a) uniformly mixing bisphenol A type epoxy resin and diallyl phthalate, then adding methylphenylsilane and stirring to react, and obtaining a mixed solution after the reaction is completed;

[0023] (b) adding boron nitride into toluene, then adding γ-aminopropyl trimethoxysilane, and carrying out constant temperature reaction, and after the reaction is completed, filtering and drying to obtain aminated boron nitride; then adding the aminated boron nitride, pentaerythritol monooctyleneglycol acrylate, toluene diisocyanate and epichlorohydrin into anhydrous ethanol, and carrying out stirring reaction, and after the reaction is completed, obtaining modified boron nitride;

[0024] (c) mixing the mixed solution in step (a), the modified boron nitride in step (b), trimellitic anhydride and boron trifluoride ethylamine uniformly to obtain the insulating paint.

[0025] Preferably, in step (a), the mass ratio of the bisphenol A type epoxy resin, phthalic acid type resin, diallyl phthalate and methyl phenyl silane is 60:20-30:1-3; the stirring reaction temperature is 50-70℃, and the reaction time is 2-4h.

[0026] Preferably, in step (b), the mass ratio of the boron nitride and γ-aminopropyl trimethoxysilane is 100:1-3; the constant temperature reaction temperature is 30-50℃, and the reaction time is 1-3h; the mass ratio of the aminated boron nitride, pentaerythritol monooctyleneglycol acrylate, toluene diisocyanate and epichlorohydrin is 100:50-60:30-40:20-30; the stirring reaction temperature is 40-50℃, and the reaction time is 3-6h; in step (c), the mass ratio of the mixed solution, modified boron nitride, trimellitic anhydride and boron trifluoride ethylamine is 100:3-6:2-4:0.3-1.

[0027] Preferably, in step S7, the setting values of the curing time and temperature are as follows:

[0028] (1) heating for 0.5h to raise the temperature from 30℃ to 90℃;

[0029] (2) keeping the temperature at 90℃ for 2h;

[0030] (3) heating for 0.5h to raise the temperature from 90℃ to 150℃;

[0031] (4) keeping the temperature at 150℃ for 8h;

[0032] (5) cooling for 1h to lower the temperature from 150℃ to 90℃;

[0033] (6) keeping the temperature at 90℃ for 2h;

[0034] (7) naturally cooling.

[0035] Preferably, in step S8, the surface shaping is carried out by manual polishing or mechanical processing.

[0036] Compared with the prior art, the present application has the following beneficial effects:

[0037] (1) The application provides a manufacturing method of an involute transformer core, which comprises the following steps: blanking, roll forming, inserting and stacking, bundling, preheating, immersing in insulating paint, solidifying, surface treatment and gluing.

[0038] (2) The application provides a manufacturing method of an involute transformer core, wherein the used involute silicon steel sheet has a single specification, the width of the silicon steel sheet is prevented from being in multiple specifications, management is facilitated, and the storage device is reduced.

[0039] (3) The application provides a manufacturing method of an involute transformer core, wherein the roll-formed involute parameters are consistent, the adhesion between two adjacent involute silicon steel sheets is high, and the gap is small, that is, the lamination coefficient of the transformer core made of the involute silicon steel sheet is high.

[0040] (4) The application provides a manufacturing method of an involute transformer core, wherein the number of the required involute silicon steel sheets and the inner diameter of the stainless steel hoop can be calculated according to the diameter of the base cylinder and the specification of the involute silicon steel sheet, so as to ensure the overall performance of the transformer core.

[0041] (5) The application provides a manufacturing method of an involute transformer core, wherein the surface of boron nitride is grafted with pentaerythritol and siloxane by modifying boron nitride, the heat resistance of the insulating paint is improved by using boron nitride as a filling heat-conducting material, the modified boron nitride fillers can form a heat-conducting net chain by mutual lapping, heat can be quickly conducted along the heat-conducting path, the compatibility between the boron nitride and the matrix resin is improved by introducing organic branches on the surface of the boron nitride, the mechanical properties of the insulating paint are improved, and the dielectric properties of the epoxy resin are excellent, and the epoxy resin remains stable in a high temperature, humidity and frequency range by adding diallyl phthalate and methylphenylsilane in the epoxy resin matrix. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is a schematic view of the application before roll forming;

[0043] Figure 2 is a schematic view of the involute silicon steel sheet formed after roll forming of the application;

[0044] Figure 3 is a schematic view of the application after inserting and stacking, and the stainless steel hoop is tightly held;

[0045] Figure 4 is a schematic view of the finished product of the application.

[0046] In the figure: 1, silicon steel sheet blank; 2, roll forming tool; 3, involute silicon steel sheet; 4, base cylinder; 5, stainless steel hoop; 6, epoxy cylinder. Detailed Implementation

[0047] 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 embodiments of the present invention, and not all embodiments. Based on the 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.

[0048] Example 1

[0049] See appendix Figures 1 to 4 The present invention provides a method for manufacturing an involute transformer core, comprising the following steps:

[0050] S1) Cutting: The stainless steel silicon steel sheet is cut into blank 1 by mechanical equipment to obtain silicon steel sheet blank 1. The thickness of silicon steel sheet blank 1 is 0.08mm.

[0051] S2) Roll forming: The silicon steel blank 1 is formed into an involute silicon steel sheet 3 using the roll forming fixture 2. The roll forming fixture 2 is a cylinder with a groove and rounded corners at both ends. To improve the efficiency of roll forming, the width of the groove of the roll forming fixture 2 is usually 0.8mm, so that ten silicon steel blanks 1 can be rolled simultaneously. The length of the roll forming fixture 2 is equal to the length of the silicon steel blank 1. During roll forming, ten silicon steel blanks 1 are inserted into the groove of the roll forming fixture 2 and pressed tightly. Roll forming is performed on the worktable to obtain ten involute silicon steel sheets 3.

[0052] S3) Stacking: Based on the outer diameter of the base cylinder 4 and the thickness of the involute silicon steel sheet 3, the number n of involute silicon steel sheets 3 required for stacking can be calculated, where n = outer circumference of the base cylinder / thickness of a single involute silicon steel sheet. Stack n involute silicon steel sheets 3 around the perimeter of the base cylinder 4, and use several stainless steel clamps 5 to clamp the involute silicon steel sheets 3 to the base cylinder 4 to form a clamping component. In order to increase the clamping effect, the interval between adjacent stainless steel clamps 5 is 200mm. After clamping, the clamping component is annealed as a whole to eliminate stress.

[0053] S4) Binding: After securing the clamping parts with wire, separate the stainless steel clamp 5 from the clamping parts.

[0054] S5) Preheating: Preheat the bundled wire bundles to 100℃.

[0055] S6) Impregnation: The preheated bundled parts are immersed in insulating varnish. The impregnation is carried out in an impregnation tank. After the workpiece is placed in, it is immersed for 0.5 hours under vacuum with a pressure of ≤200Pa. Then the pressure is increased to 0.4Mpa and maintained for 0.5 hours before being taken out.

[0056] S7) curing, curing the bundled piece after the insulating material is applied, the curing is divided into stages of heating, holding, cooling, holding and natural cooling, and the specific curing time and temperature setting value are:

[0057] (1) heating for 0.5h, making the temperature rise from 30℃ to 90℃;

[0058] (2) holding at 90℃ for 2h;

[0059] (3) heating for 0.5h, making the temperature rise from 90℃ to 150℃;

[0060] (4) holding at 150℃ for 8h;

[0061] (5) cooling for 1h, making the temperature rise from 150℃ to 90℃;

[0062] (6) holding at 90℃ for 2h;

[0063] (7) natural cooling.

[0064] S8) surface treatment, first removing the iron wire on the surface of the bundled piece, the surface of the bundled piece after removing the iron wire will have uneven insulating material, at this time, manual polishing or machining can be performed on the residual material according to the size of the residual material, and the outer surface is shaped.

[0065] S9) gluing, the outer surface of the part after surface treatment in step S8 is coated with epoxy glue, and is firmly bonded with the epoxy cylinder 6, and is placed on a special storage device, completing the production of a single involute transformer core, wherein the lengths of the involute silicon steel sheet 3, the base cylinder 4 and the epoxy cylinder 6 are equal.

[0066] The preparation method of the insulating paint in step S6 comprises the following steps:

[0067] (a) uniformly mixing 60g of bisphenol A type epoxy resin and 25g of diallyl phthalate, then adding 2g of methylphenylsilane, stirring and reacting at 60℃ for 3h, and obtaining a mixed solution after the reaction is completed;

[0068] (b) adding 100g of boron nitride into 800mL of toluene, then adding 2g of γ-aminopropyltrimethoxysilane, and reacting at 40℃ for 2h, filtering and drying after the reaction is completed to obtain aminated boron nitride; then adding 100g of aminated boron nitride, 55g of pentaerythritol monoacrylate, 35g of toluene diisocyanate and 25g of epoxy chloropropane into 800mL of anhydrous ethanol, stirring and reacting at 45℃ for 5h, and obtaining modified boron nitride after the reaction is completed;

[0069] (c) mixing the mixture (100 g) in step (a), the modified boron nitride (5 g) in step (b), 3 g of trimellitic anhydride, and 0.5 g of boron trifluoride ethylamine to obtain the insulating paint.

[0070] Example 2

[0071] The application provides a manufacturing method of an involute transformer core, comprising the following steps:

[0072] S1) blanking, the stainless steel silicon steel sheet is cut by a mechanical device to obtain a silicon steel sheet blank 1, and the thickness of the silicon steel sheet blank 1 is 0.08 mm.

[0073] S2) roll forming, the silicon steel sheet blank 1 is formed into an involute silicon steel sheet 3 by using a roll forming tool 2, the roll forming tool 2 is a cylinder, the roll forming tool 2 is provided with a groove, and the two ends of the groove are provided with round corners, in order to improve the efficiency of roll forming, the width of the groove of the roll forming tool 2 is usually 0.8 mm, so that ten silicon steel sheet blanks 1 can be simultaneously roll formed, the length of the roll forming tool 2 is equal to the length of the silicon steel sheet blank 1, ten silicon steel sheet blanks 1 are inserted into the groove of the roll forming tool 2 and are pressed tightly, and roll forming is performed on a workbench, so that ten involute silicon steel sheets 3 are obtained.

[0074] S3) insertion and stacking, according to the outer diameter of the base cylinder 4 and the thickness of the involute silicon steel sheet 3, the number n of the involute silicon steel sheets 3 required during insertion and stacking can be calculated, wherein n = the outer circumference of the base cylinder / the thickness of a single involute silicon steel sheet, n involute silicon steel sheets 3 are stacked around the periphery of the base cylinder 4, and a plurality of stainless steel hoops 5 are used to tightly hold the involute silicon steel sheets 3 and the base cylinder 4 to form a tightly held piece, in order to increase the holding effect, the interval between adjacent stainless steel hoops 5 is 200 mm, and the tightly held piece is annealed as a whole after being tightly held to eliminate stress.

[0075] S4) bundling, after the tightly held piece is tightly bundled with iron wire, the stainless steel hoops 5 are separated from the tightly held piece.

[0076] S5) preheating, the bundled piece tightly bundled with the iron wire is preheated, and the preheating temperature is 100 DEG C.

[0077] S6) paint dipping, the preheated bundled piece is dipped into insulating paint, the dipping is performed in a paint dipping tank, after the workpiece is put into the paint dipping tank, the paint dipping tank is vacuumized to keep the pressure at ≤200 Pa, then the pressure is increased to 0.4 Mpa after the workpiece is soaked for 0.5 h, and the workpiece is taken out after being kept for 0.5 h;

[0078] S7) solidification, the bundled piece coated with the insulating material is solidified, and the solidification includes the stages of temperature rising, temperature keeping, temperature falling, temperature keeping and natural cooling, and the specific solidification time and temperature setting value are as follows:

[0079] (1) temperature rising for 0.5 h, so that the temperature rises from 30 DEG C to 90 DEG C;

[0080] (2) 90℃, 2h;

[0081] (3) 0.5h, from 90℃ to 150℃;

[0082] (4) 150℃, 8h;

[0083] (5) 1h, from 150℃ to 90℃;

[0084] (6) 90℃, 2h;

[0085] (7) natural cooling.

[0086] S8) surface treatment, firstly removing iron wire on the surface of the binding member, uneven insulating material will exist on the surface of the binding member after removing the iron wire, at this time, manual polishing or machining can be carried out according to the size of the residue, and the outer surface is shaped.

[0087] S9) gluing, the outer surface of the part after surface treatment in step S8 is coated with epoxy glue, and is firmly bonded with the epoxy cylinder 6, and is placed on a special storage device, and the production of a single involute transformer core is completed, wherein the lengths of the involute silicon steel sheet 3, the base cylinder 4 and the epoxy cylinder 6 are equal.

[0088] The preparation method of the insulating paint in step S6 comprises the following steps:

[0089] (a) 60g of bisphenol A type epoxy resin, 20g of diallyl phthalate are uniformly mixed, then 1g of methylphenylsilane is added, and stirring reaction is carried out at 20℃ for 2h, and a mixed solution is obtained after the reaction is completed;

[0090] (b) 100g of boron nitride is added into 800mL of toluene, then 1g of γ-aminopropyltrimethoxysilane is added, and constant temperature reaction is carried out at 30℃ for 1h, and after the reaction is completed, filtration and drying are carried out to obtain aminated boron nitride; then 100g of aminated boron nitride, 50g of pentaerythritol monoacrylate, 30g of toluene diisocyanate and 20g of epoxy chloropropane are added into 800mL of anhydrous ethanol, and stirring reaction is carried out at 40℃ for 3h, and modified boron nitride is obtained after the reaction is completed;

[0091] (c) the mixed solution (100g) in step (a), the modified boron nitride (3g) in step (b), 2g of trimellitic anhydride and 0.3g of boron trifluoride ethylamine are uniformly mixed, and the insulating paint is obtained.

[0092] Example 3

[0093] The application provides a production method of an involute transformer core, comprising the following steps:

[0094] S1) blanking, using mechanical equipment to cut the stainless steel silicon steel sheet to obtain the silicon steel sheet blank 1, the thickness of the silicon steel sheet blank 1 is 0.08mm.

[0095] S2) roll forming, using a roll forming tool 2 to make the involute silicon steel sheet 3 from the silicon steel sheet blank 1, the roll forming tool 2 is a cylinder, the roll forming tool 2 is provided with a groove and the two ends of the groove are provided with a round corner, in order to improve the efficiency of roll forming, the width of the groove of the roll forming tool 2 is usually 0.8mm, so that ten silicon steel sheet blanks 1 can be roll formed at the same time, the length of the roll forming tool 2 is equal to the length of the silicon steel sheet blank 1, when roll forming, ten silicon steel sheet blanks 1 are inserted into the groove of the roll forming tool 2 and are pressed tightly, and roll forming is carried out on the workbench, so that ten involute silicon steel sheets 3 can be obtained.

[0096] S3) insertion and stacking, according to the outer diameter of the base cylinder 4 and the thickness of the involute silicon steel sheet 3, the number n of the involute silicon steel sheets 3 required when insertion and stacking is calculated, wherein n = the outer circumference of the base cylinder / the thickness of a single involute silicon steel sheet, n involute silicon steel sheets 3 are stacked around the periphery of the base cylinder 4, and a plurality of stainless steel hoops 5 are used to tightly hold the involute silicon steel sheets 3 and the base cylinder 4 to form a tightly held piece, in order to increase the holding effect, the interval between adjacent stainless steel hoops 5 is 200mm, and after being tightly held, the tightly held piece is annealed as a whole to eliminate stress.

[0097] S4) bundling, after the tightly held piece is tightly bundled with iron wire, the stainless steel hoops 5 are separated from the tightly held piece.

[0098] S5) preheating, the bundled piece bundled with iron wire is preheated, and the preheating temperature is 100℃.

[0099] S6) paint dipping, the preheated bundled piece is dipped into insulating paint; after the workpiece is put into the paint dipping tank, it is soaked for 0.5h under the condition that the pressure is kept at ≤200Pa, then the pressure is increased to 0.4Mpa and kept for 0.5h, and then it is taken out;

[0100] S7) curing, the bundled piece coated with insulating material is cured, and the curing includes the stages of temperature rising, temperature keeping, temperature falling, temperature keeping and natural cooling, and the specific curing time and temperature setting value are:

[0101] (1) temperature rising for 0.5h, so that the temperature rises from 30℃ to 90℃;

[0102] (2) temperature keeping at 90℃ for 2h;

[0103] (3) temperature rising for 0.5h, so that the temperature rises from 90℃ to 150℃;

[0104] (4) temperature keeping at 150℃ for 8h;

[0105] (5) temperature falling for 1h, so that the temperature rises from 150℃ to 90℃;

[0106] (6) 90℃, 2h;

[0107] (7) Natural cooling.

[0108] S8) Surface treatment, firstly removing the iron wire on the surface of the binding member, the surface of the binding member with the removed iron wire will have uneven insulating material, at this time, the residual material can be manually polished or machined according to its size, and the outer surface is shaped.

[0109] S9) Gluing, the outer surface of the part with the surface treatment in step S8 is coated with epoxy glue, and is firmly bonded with the epoxy cylinder 6, and is placed on a special storage device to complete the production of a single involute transformer core, wherein the lengths of the involute silicon steel sheet 3, the base cylinder 4 and the epoxy cylinder 6 are equal.

[0110] The preparation method of the insulating paint in step S6 comprises the following steps:

[0111] (a) 60g of bisphenol A type epoxy resin, 30g of diallyl phthalate are uniformly mixed, then 3g of methylphenylsilane is added, and stirring reaction is carried out at 70℃ for 4h, and a mixed solution is obtained after the reaction is completed;

[0112] (b) 100g of boron nitride is added into 800mL of toluene, then 3g of γ-aminopropyltrimethoxysilane is added, and constant temperature reaction is carried out at 50℃ for 3h, and after the reaction is completed, filtration and drying are carried out to obtain aminated boron nitride; then 100g of aminated boron nitride, 60g of pentaerythritol monoacrylate, 40g of toluene diisocyanate and 30g of epoxy chloropropane are added into 800mL of anhydrous ethanol, and stirring reaction is carried out at 50℃ for 6h, and a modified boron nitride is obtained after the reaction is completed;

[0113] (c) the mixed solution (100g) in step (a), the modified boron nitride (6g) in step (b), 4g of trimellitic anhydride and 1g of boron trifluoride ethylamine are uniformly mixed to obtain the insulating paint.

[0114] Comparative Example 1

[0115] A production method of an involute transformer core comprises the following steps:

[0116] S1) Cutting, using mechanical equipment to cut the stainless steel silicon steel sheet to obtain a silicon steel blank 1, and the thickness of the silicon steel blank 1 is 0.08mm.

[0117] S2) roll forming, using a roll forming tool 2 to make the involute silicon steel sheet 3 from the silicon steel sheet blank 1, the roll forming tool 2 being a cylinder, the roll forming tool 2 being provided with a groove and the two ends of the groove being provided with a round corner, in order to improve the efficiency of the roll forming, the width of the groove of the roll forming tool 2 is usually 0.8mm, so that ten silicon steel sheet blanks 1 can be simultaneously roll formed, the length of the roll forming tool 2 being equal to the length of the silicon steel sheet blank 1, ten silicon steel sheet blanks 1 being inserted into the groove of the roll forming tool 2 and pressed tightly during roll forming, and the roll forming being carried out on a workbench, so that ten involute silicon steel sheets 3 can be obtained.

[0118] S3) inserting and stacking, according to the outer diameter of the base cylinder 4 and the thickness of the involute silicon steel sheet 3, the number n of the involute silicon steel sheets 3 required during the inserting and stacking can be calculated, wherein n = the outer circumference of the base cylinder / the thickness of a single involute silicon steel sheet, n involute silicon steel sheets 3 are stacked around the periphery of the base cylinder 4, and a plurality of stainless steel hoops 5 are used to tightly hold the involute silicon steel sheets 3 and the base cylinder 4 to form a tightly held piece, in order to increase the effect of the holding, the interval between adjacent stainless steel hoops 5 is 200mm, and after the holding, the tightly held piece is annealed as a whole to eliminate stress.

[0119] S4) bundling, after the tightly held piece is tightly bundled with iron wire, the stainless steel hoops 5 are separated from the tightly held piece.

[0120] S5) preheating, the bundled piece tightly bundled with iron wire is preheated, and the preheating temperature is 100℃.

[0121] S6) paint dipping, the preheated bundled piece is dipped into insulating paint; after the workpiece is put into the paint dipping tank, it is soaked for 0.5h under the condition that the pressure is kept at ≤200Pa after vacuumizing, and then the pressure is increased to 0.4Mpa and kept for 0.5h, and then the workpiece is taken out;

[0122] S7) curing, the bundled piece coated with insulating material is cured, and the curing is divided into stages of temperature rising, temperature keeping, temperature falling, temperature keeping and natural cooling, and the specific curing time and temperature setting value are:

[0123] (1) temperature rising for 0.5h, so that the temperature rises from 30℃ to 90℃;

[0124] (2) temperature keeping for 2h at 90℃;

[0125] (3) temperature rising for 0.5h, so that the temperature rises from 90℃ to 150℃;

[0126] (4) temperature keeping for 8h at 150℃;

[0127] (5) temperature falling for 1h, so that the temperature rises from 150℃ to 90℃;

[0128] (6) temperature keeping for 2h at 90℃;

[0129] (7) natural cooling.

[0130] S8) surface treatment, first remove the iron wire on the surface of the binding member, the surface of the binding member where the iron wire is removed will have uneven insulating material, at this time the residue can be manually polished or machined according to its size, and the outer surface is shaped.

[0131] S9) gluing, epoxy glue is applied to the outer surface of the part that has been surface treated in step S8, and is firmly bonded with the epoxy cylinder 6, and is placed on a special storage device, completing the production of a single involute transformer core, wherein the lengths of the involute silicon steel sheet 3, the base cylinder 4 and the epoxy cylinder 6 are equal.

[0132] The preparation method of the insulating paint in step S6 comprises the following steps:

[0133] (a) uniformly mix 60g of bisphenol A type epoxy resin and 25g of diallyl phthalate, stir and react at 60°C for 3h, and obtain a mixed solution after the reaction is completed;

[0134] (b) uniformly mix the mixed solution (100g) in step (a), 5g of boron nitride, 3g of trimellitic anhydride and 0.5g of boron trifluoride ethylamine, and the insulating paint is obtained.

[0135] The involute transformer cores prepared in Examples 1-3 and Comparative Example 1 were tested for performance, wherein the breakdown voltage was tested according to standard GB / T1408.1-2016, and the volume resistivity was tested according to standard GB / T31838.5-2021, and the test results are shown in Table 1 below

[0136] Table 1

[0137] Breakdown voltage / kV Volume resistivity / Ω.m Example 1 96 5.3 x 10 12 ]]> Example 2 92 5.2 x 10 12 ]]> Example 3 93 4.9 x 10 12 ]] Comparative Example 1 81 2.7 x 10 12 ]]

[0138] As can be seen from Table 1 above, the involute transformer core prepared by the present application has good breakdown voltage and volume resistivity, and has good application prospect; the insulating paint in Comparative Example 1 does not contain methylphenylsilane and modified boron nitride, resulting in a significant decrease in electrical performance.

[0139] Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method of making an involute transformer core, characterized by, The method comprises the following steps: S1, blanking, cutting the stainless steel silicon steel sheet to obtain a silicon steel sheet blank (1); S2, roll forming, using a roll forming tool (2) to make the silicon steel sheet blank (1) into an involute silicon steel sheet (3); S3, inserting and stacking, stacking a plurality of involute silicon steel sheets (3) around the periphery of a base cylinder (4), and using a plurality of stainless steel hoops (5) to tightly hold the involute silicon steel sheets (3) and the base cylinder (4) to form a tightly held part, and annealing the tightly held part as a whole; S4, bundling, after the tightly held part is firmly bundled with iron wire, the stainless steel hoops (5) are separated from the tightly held part; S5, preheating, preheating the bundled part; S6, dipping paint, immersing the preheated bundled part into insulating paint; S7, curing, curing the bundled part; S8, surface treatment, removing the iron wire on the surface of the bundled part and shaping the outer surface of the bundled part after removing the iron wire; S9, gluing, applying epoxy glue to the outer surface of the part after surface treatment in step S8, and firmly bonding with an epoxy cylinder (6); The preparation method of the insulating paint in step S6 comprises the following steps: (a) uniformly mixing bisphenol A type epoxy resin and diallyl phthalate, then adding methylphenylsilane and stirring to react, and obtaining a mixed solution after the reaction is completed; (b) adding boron nitride into toluene, then adding γ-aminopropyltrimethoxysilane and performing constant temperature reaction, filtering and drying after the reaction is completed to obtain aminated boron nitride; then adding aminated boron nitride, pentaerythritol monoacrylate, toluene diisocyanate and epichlorohydrin into anhydrous ethanol and stirring to react, and obtaining modified boron nitride after the reaction is completed; (c) uniformly mixing the mixed solution in step (a), the modified boron nitride in step (b), trimellitic anhydride and boron trifluoride amine to obtain the insulating paint; The mass ratio of the bisphenol A type epoxy resin, diallyl phthalate and methylphenylsilane in step (a) is 60:20-30:1-3; the temperature of the stirring reaction is 50-70°C, and the reaction time is 2-4h; The mass ratio of the boron nitride and γ-aminopropyltrimethoxysilane in step (b) is 100:1-3; the temperature of the constant temperature reaction is 30-50°C, and the reaction time is 1-3h; the mass ratio of the aminated boron nitride, pentaerythritol monoacrylate, toluene diisocyanate and epichlorohydrin is 100:50-60:30-40:20-30; the temperature of the stirring reaction is 40-50°C, and the reaction time is 3-6h; the mass ratio of the mixed solution, modified boron nitride, trimellitic anhydride and boron trifluoride amine in step (c) is 100:3-6:2-4:0.3-1.

2. The method of making an involute transformer core of claim 1, wherein, The thickness of the silicon steel sheet blank (1) in step S1 is 0.04-0.1mm.

3. The method of making an involute transformer core of claim 1, wherein, The roll forming tool (2) in step S2 is a cylinder, the roll forming tool (2) is provided with a groove, and the two ends of the groove are provided with round corners; the lengths of the involute silicon steel sheet (3), the base cylinder (4) and the epoxy cylinder (6) are equal.

4. The method of making an involute transformer core of claim 1, wherein, The number n of the involute silicon steel sheets (3) used in step S3 is calculated by the following formula: n = outer circumference length of base cylinder / thickness of single involute silicon steel sheet.

5. The method of making an involute transformer core of claim 1, wherein, The preheating temperature of step S5 is 90-120℃.

6. The method of making an involute transformer core of claim 1, wherein, The curing time and temperature setting values in step S7 are: (1) heating for 0.5h to raise the temperature from 30℃ to 90℃; (2) keeping the temperature at 90℃ for 2h; (3) heating for 0.5h to raise the temperature from 90℃ to 150℃; (4) keeping the temperature at 150℃ for 8h; (5) cooling for 1h to lower the temperature from 150℃ to 90℃; (6) keeping the temperature at 90℃ for 2h; (7) natural cooling.

7. The method of making an involute transformer core of claim 1, wherein, The surface shaping of step S8 is performed by manual polishing or machining.

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