Method for producing an adhesion- and crack-resistant insulating layer structure and topcoat structure for current transformer housings

Abstract

Method for producing an adhesion- and crack-resistant insulating layer structure and topcoat structure for current transformer housings (1), wherein The cleaning of the current transformer housing (1) is carried out in several steps: to remove organic substances, a brief flame treatment is applied; then, to remove inorganic contaminants, especially electrostatic charge carriers, ionized air is blown out; subsequently, moisture is removed by ice drying or heat application; and then an adhesion promoter (2) in the form of a primer (2) is applied as an intermediate layer (2) with a defined layer thickness to the metal current transformer housing (1), with the simultaneous introduction of dipoles and an enlarged adhesion surface, which is generated by means of a high-pulsed blasting process; and on this intermediate layer (2) a conductive coupling layer (3) in the form of an electrically conductive lacquer (3) is applied as a basis for the subsequent assembly of the current transformer housing (1) with a current transformer (4) using potting technology.wherein, as a basis for the subsequent installation of the current transformer using potting technology in the current transformer housing (1), a primer (2) as an intermediate layer (2), as an adhesion promoter (2) and as an insulating layer (2) based on a 2K filling primer and an electrically conductive lacquer (3) as a top layer lacquer (3) and as a coupling layer (3) are applied one above the other, wherein the electrically conductive lacquer (3) consists of pigmented polyester and wherein the base filler (2) and the topcoat lacquer (3) are both applied in the same layer thickness of approximately 10 µm.

Description

[0001] Adhesion- and crack-resistant insulating layer structure and top layer coating structure for current transformer housings and an associated manufacturing process for the subsequent installation of the current transformer coils with potting technology.

[0002] The current transformer coils are potted during installation in the current transformer housings. During this process, and later during the use of the current transformer, cracks and various adhesion problems quickly arise between the potting compound of the current transformer coil and the current transformer housing. This problem has already been addressed in several publications. For example, German patent DE 25 14 607 A1 describes a method for producing insulating lacquer layers and an insulating layer produced according to this method. In this method, a material with very high specific electrical strength, such as mica or aluminum oxide in the form of small flakes, is added to the lacquer. These flakes are embedded in the lacquer layer as it is applied to the conductor or coil, forming dipoles. This results in a significant increase in electrical strength.At the same time, the presence of these flakes results in the paint layer having a much greater mechanical compressive strength. According to the inventive method, the paint layer can be built up by electrophoresis and / or electrostatic spraying. In one variant, the application can also be carried out in two or more layers.

[0003] German patent DE 10 2006 014 199 A1 describes a method for improving the adhesion of insulating coatings to substrates and reducing cracking of transducer housings. After surface treatment with a solvent-based cleaning fluid, an adhesion promoter is applied, followed by an insulating coating. An additional release agent is then applied to the insulating coating, which reduces the force transmission of the resin to the insulating coating during the subsequent potting of the transducer.

[0004] Furthermore, patent DE 14 79 428 B describes a method for encasing devices, in particular electrical, current-carrying metal parts, in which the device is first surrounded with a cushioning layer made of elastic plastic, in which an electrically conductive or semiconducting shielding surface is applied over it, which is then encased with castable synthetic resin, and in which both the cushioning layer and a thin layer of elastic synthetic resin provided between the cushioning layer and the shielding surface for sealing the cushioning layer and finally the shielding surface consisting of synthetic resin-bonded conductive lacquer are sprayed on using a multi-component metering spray gun.

[0005] Document US 2003 / 0175541A1 describes a conductive and weldable corrosion protection composition for coating metal surfaces, comprising: (a) 5 to 40 wt.% of an organic binder containing: (aa) at least one epoxy resin, (ab) at least one hardener selected from cyanoguanidine, benzoguanamine, and plasticizer, (ac) at least one amine adduct selected from polyoxycylenetriamine and epoxy resin / amine adducts, (b) 0 to 15 wt.% of a corrosion protection pigment, (c) 40 to 70 wt.% of a conductive pigment selected from powdered zinc, aluminum, graphite, molybdenum sulfide, carbon black, and iron phosphide, (d) 0 to 45 wt.% of a solvent; and a painted metal structural component having a conductive organic layer.

[0006] German patent application DE 10 2005 059 614 A1 describes a coating material for protecting metals, especially steel, from corrosion and / or scaling, a method for coating metals, and a metal element. To create a coating material that protects steel from corrosion and / or scaling and remains weldable after heat treatment of the coated steel at temperatures above 800°C, it is proposed that means for achieving weldability, particularly by spot welding, of the applied coating material be provided; that the coating material be applicable by wet chemical means; that the coating material undergo a structural change during high-temperature processes above 600°C and be suitable as a base for further coating materials.Surprisingly, it was found that by using a suitable binder with a suitable filler during the high-temperature treatment of a hardening process, the coatings according to the invention transform in such a way that electrically conductive reaction layers are formed which, together with the metal substrate, can be welded and, in particular, spot welded even after treatment at temperatures above 800 degrees C.

[0007] The invention is based on the objective of creating a method for producing an adhesion- and crack-resistant insulating layer structure and top layer coating structure for current transformer housings, which has good adhesion to the transformer housing and between the coating structure and the potting compound of the coils and good electrical properties, such as good insulation and at the same time magnetic decoupling.

[0008] Furthermore, the current transformer coils must be encased on at least five sides to prevent electrostatic discharge and to provide antistatic protection. Additionally, no abrasion should occur in the coating during the potting of the coils with the potting compound.

[0009] The inventive problem is solved by the features of the main claim, through the technology of the process.

[0010] In addition to the solutions named in the problem statement, the advantages achievable with the invention also include the fact that the previously common step of applying an additional separating layer can be eliminated, thus saving working time.

[0011] An embodiment produced using a method according to the invention is shown in the drawing, and the method is described in more detail below. The drawing shows the insulating layer structure and the topcoat lacquer structure with an embedded coil in the current transformer housing.

[0012] The insulation and coating structure on the inside of the current transformer housing 1 consists of a layer of primer 2, acting as an adhesion promoter 2 and as an insulating layer 2, based on a 2K filler primer. On top of this layer lies a layer of electrically conductive lacquer 3 made of pigmented polyester, serving as a topcoat 3 and as a coupling layer 3. The coupling layer 3 has an enlarged adhesion surface. Both layers, the primer 2 and the coupling layer 3, preferably have an approximately equal thickness of 10 µm.

[0013] The inventive method for producing an adhesion- and crack-resistant inner coating for a metal current transformer housing 1 is characterized by the following process steps. The method begins with a surface pretreatment process. Organic substances are removed by brief flame treatment instead of using solvents or so-called adhesion promoters. This is followed by the removal of inorganic contaminants, in particular electrostatic charge carriers, by blowing with ionized air, and finally, the removal of moisture by ice drying or the application of heat.

[0014] After surface pretreatment, an adhesion promoter 2 in the form of a primer 2 is applied to the current transformer housing 1 using a high-pulse blasting process. The pulsation of the beam is significantly greater than the pulsation of the current transformer housing 1; that is, the pulse frequency of the beam is chosen to be much higher than the resonant frequency of the current transformer housing 1. This increases the adhesion surface area and thus creates better coupling to the layer above. Dipoles are added to the adhesion promoter 2, which, depending on their charge strength, provide electrical and magnetic decoupling and thus electrical insulation.

[0015] An electrically conductive lacquer 3, based on pigmented polyester, is then applied as a coupling layer 3 to the base filler 2. This achieves a Faraday paradox and thus prevents electrostatic charging. The required enclosure condition of the current transformer, at least five sides, is thereby fulfilled, and good adhesion to the potting compound 5 is achieved, thus preventing the coupling layer 3 from detaching due to shrinkage of the potting compound 5. No abrasion effect will occur during the pouring of the potting compound 5 if over-coating is avoided; that is, the adhesion promoter 2 and the coupling layer 3 are applied with an equal thickness, preferably approximately 10 µm. Compilation of reference symbols 1 current transformer housing 2. Bonding agent, primer, insulating layer 3 electrically conductive lacquer, topcoat lacquer, coupling layer 4 current transformers 5 Potting compound

Claims

[1] Method for producing an adhesion- and crack-resistant insulating layer structure and top layer coating structure for current transformer housings (1), wherein The cleaning of the current transformer housing (1) is carried out in several steps: to remove organic substances, a brief flame treatment is applied; then, to remove inorganic contaminants, especially electrostatic charge carriers, ionized air is blown out; subsequently, moisture is removed by ice drying or the application of heat; and then an adhesion promoter (2) in the form of a primer (2) is applied as an intermediate layer (2) with a defined layer thickness to the metal current transformer housing (1), with the simultaneous introduction of dipoles and an enlarged adhesion surface, which is generated by means of a high-pulsed blasting process; and on this intermediate layer (2) a conductive coupling layer (3) in the form of an electrically conductive lacquer (3) is applied as a basis for the subsequent assembly of the current transformer housing (1) with a current transformer (4) using potting technology.wherein, as a basis for the subsequent installation of the current transformer using potting technology in the current transformer housing (1), a primer (2) as an intermediate layer (2), as an adhesion promoter (2) and as an insulating layer (2) based on a 2K filling primer and an electrically conductive lacquer (3) as a top layer lacquer (3) and as a coupling layer (3) are applied one above the other, wherein the electrically conductive lacquer (3) consists of pigmented polyester and wherein the base filler (2) and the topcoat lacquer (3) are both applied in the same layer thickness of approximately 10 µm. [2] Method for producing an adhesion- and crack-resistant insulating layer structure and topcoat structure according to claim 1, characterized by , that a dilution of less than 10% of the total volume is additionally mixed into the base filler (2) before application.

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