Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
  • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
  • H01F41/04—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing coils
  • H01F41/12—Insulating of windings
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/28—Coils; Windings; Conductive connections
  • H01F27/32—Insulating of coils, windings, or parts thereof
  • H01F27/324—Insulation between coil and core, between different winding sections, around the coil; Other insulation structures
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
  • C08G63/60—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from the reaction of a mixture of hydroxy carboxylic acids, polycarboxylic acids and polyhydroxy compounds
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
  • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
  • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
  • H01B3/40—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes epoxy resins
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
  • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
  • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
  • H01B3/42—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes polyesters; polyethers; polyacetals
  • H01B3/421—Polyesters
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/28—Coils; Windings; Conductive connections
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/28—Coils; Windings; Conductive connections
  • H01F27/2871—Pancake coils
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/28—Coils; Windings; Conductive connections
  • H01F27/32—Insulating of coils, windings, or parts thereof
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
  • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
  • H01F41/04—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing coils
  • H01F41/12—Insulating of windings
  • H01F41/125—Other insulating structures; Insulating between coil and core, between different winding sections, around the coil
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/28—Coils; Windings; Conductive connections
  • H01F27/32—Insulating of coils, windings, or parts thereof
  • H01F27/322—Insulating of coils, windings, or parts thereof the insulation forming channels for circulation of the fluid
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/49002—Electrical device making
  • Y10T29/4902—Electromagnet, transformer or inductor

Definitions

• the invention relates to the field of electrical transformers, particularly insulators or spacers used in power and distribution transformers.
• a transformer is a device for stepping-up, isolating or stepping- down, the voltage of an alternating electric signal and is widely used for transferring energy of an alternating current in the primary winding to that in one or more secondary windings.
• the basic design of a transformer consists of two or more electrical circuits comprising primary and secondary windings, each made of multi- turn coils of conductors with one or more magnetic cores coupling the coils by transferring magnetic flux there between.
• the two or more vertically arranged laminated steel core legs have two or more windings concentrically arranged around each core leg.
• the windings are commonly separated into Low Voltage (LV) and High Voltage (HV) winding sections.
• LV and HV coils are interleaved vertically for shell form construction. The coils are separated from each other by a dielectric (insulating) material. It is known, for example, see U.S. published patent application no.
• the windings are of the disc type, which term also encompasses the terms section, helix, and, in the shell form type, the term pancake
• it is known to provide axial and radial spacing through appropriate use of axial spacers and/or radial (disc) spacers.
• the radial spacers are discreet and secured onto the axial spacers along the height of the coil so as to maintain the radial spacers in place and thus provide desired dielectric distance between conductors and adequate flow of coolant fluid around the windings.
• a fluid coolant medium such as oil, air, or gas is used.
• These radial spacers are typically glued to a sheet insulation called a washer in the shell form construction.
• the axial and radial spacers are combined to form a comb shaped configuration.
• Some examples of winding spacers are described, for example, in U.S. patents nos. 1 ,159,770, 2,201 ,005, 2,756,397, and 2,783,441.
• the insulating material must have appropriate dielectric strength, and be able to withstand heat and fluctuations of temperature.
• the coils and insulating layers are immersed in fluid, which aids in transporting heat away from the coils, so the insulator material should ideally be resistant to the commonly used fluids.
• the spacers must be able to withstand the mechanical stresses developed during manufacturing and electrical/mechanical stresses during the operation of the transformer, such as, for example, during a short-circuit event.
• the spacers are made of a variety of insulating materials depending on required temperature classes, design, cost, and other performance and property requirements.
• Commonly used materials include cellulose fibres, paper or board, ceramic materials, ararnid fibres, paper or pressboard, and glass fibre-filled thermoset materials such as epoxy or polyester, where the glass can be in form of discontinuous short fibres, a glass mat, or a fabric
• Cellulose insulation is a cost-effective insulation material, even with the significant labour required to prepare the parts.
• the parts are typically cut or sawn from large sheets, milled to a consistent thickness, milled on the edges to remove sharp corners that might tear wire insulation and then finally punched into individual parts.
• Ad-hoc adjustments during assembly of the windings are typical, to compensate for inconsistent spacers dimensions (for example in respect to the thickness of radial spacers in a disc wound assembly) and can lead to substantial increased time of assembly and, ultimately, costs.
• cellulose fibres are subject to hydrolytic degradation and age, which causes spacer shrinkage, resulting in loosening of the mechanical clamping structure, eventually leading to transformer failure under short- circuit conditions.
• a great deal of time is also spent in drying and adjusting windings, due to the moisture absorption tendency of the cellulose.
• Glass fibre-filled epoxy or polyester insulation materials have better temperature performance (up to 155 ⁇ 180°C for epoxy, up to 220 0 C for polyesters), however, the presence of glass fibres, which is necessary to impart structural rigidity, shortens the life of the insulator and may precipitate partial discharges. Under repeated temperature cycling the difference in the thermal coefficients of expansion of glass and polymer can lead to the formation of voids in the part, resulting in partial discharges or corona effects, eventually leading to the breakdown of the insulator. Hence, such materials are more commonly found in dry type transformers, whereas in liquid filled transformers aramid and cellulose fibres are generally preferred, especially in HV winding sections.
• thermoset materials are limited, placing constraints on transformer design. Also, thermoset materials are not inherently flame resistant (UL 94 -VO), and their use in dry type transformers requires extensive formulation by use of flame retardant additives. Ceramic spacers are being less and less used in dry-type transformers, primarily because of the relatively high cost due to their manufacturing process, and their brittleness, which can cause frequent need for repair. The brittleness can cause cracking during the winding process, during assembly of the coils onto the core structure, and in the field during routine maintenance. Practical limitations also apply on the variety of available shapes.
• the desired insulator shape must be cut out of a panel of pressboard, or stamped out of aramid paper sheets, resulting in significant handling and labour costs, and considerable waste of material in the non-used trimmings. All of these add to transformer cost.
• the coil assemblies have to be designed to fit the shape/size of the spacers, A need remains for improved spacers for transformers.
• the invention provides a discrete insulating spacer element, which is used to separate and maintain space between the conducting windings or coils of a transformer, wherein the spacer element is made of a liquid crystalline polymer (LCP).
• the invention provides an electrical transformer comprising: electrical conducting coils for stepping up, isolating and/or stepping down voltage, and discrete insulating spacer elements separating and insulating the electrical coils, wherein the discrete spacer elements are made of a liquid crystalline polymer.
• the invention provides a process for making an insulating spacer element for an electrical transformer, comprising injection-moulding or extruding an LCP composition into the desired form.
• the invention provides a process for making an electrical transformer, comprising the step of: inserting an insulating spacer made of LCP between coils of conducting wire.
• Figure 1 shows an electrical transformer constructed using the discrete spacer elements of the invention.
• Figure 2 shows a preferred embodiment of a discrete spacer element of the invention, with attachment means at two ends.
• Figure 3 shows a preferred embodiment of a discrete spacer element of the invention, with attachment means at one end.
• insulating spacers between coils of electrical transformers can be made of liquid crystal polymers (LCPs).
• the spacer is a modular form that can be used to build up a transformer of any desired size of shape, simply by increasing the number of coils and spacers.
• a transformer is made by forming coils, of the desired number of turns, with spacers of LCP between the coils.
• the spacers of the invention are separable from the coils.
• the method of building a transformer with the spacers of the invention is distinct from known methods of encapsulation with LCP.
• the spacers of the invention are discrete, detached or separate from the coils.
• the wire coils In the encapsulation method, the wire coils must first be made, and then cast in molten polymer. Once the coils take on larger dimensions, as is the case with a high voltage transformer for long-range transmission, it is not possible to cast them in molten polymer.
• the method of the invention is not limited in this way. Transformers of essentially limitless size and capacity can be constructed.
• transformers in which some of the spacer elements are made of LCP (for example, in potential hotspots) and other spacer elements are made of conventional materials, such as cellulose, aramid, ceramic, orthermoset material.
• the spacers of the present invention have inherently very low moisture absorption and moisture regain characteristics ( ⁇ 0.05% after 6 months immersion in water measured according to ASTM D570). This represents a significant advantage over cellulose spacers, in that spacers of the invention show excellent dimensional stability and consistency.
• the wire coils may be wrapped around the spacers made of LCP.
• the spacers made of LCP have the advantage over glass fibre- filled epoxy or polyester insulators that the spacer does not require glass- fibre reinforcement. By avoiding glass-fibre reinforcement, faults leading to partial discharges are greatly minimized, meaning the spacers have a longer useful lifetime without discharges.
• the spacers of the invention do not comprise glass fibre.
• LCP's are inherently fire-resistant. This means that spacers may be made without the addition of fire-retardants.
• spacers comprising fire retardants are also within the scope of the invention.
• compositions described herein may be made and formed into the spacers by conventional methods used for mixing and forming thermoplastic compositions.
• the compositions may be made by melt mixing the LCP and any other low melting ingredients in a typical mixing apparatus such as a single or twin-screw extruder or a melt kneader.
• Parts may be formed by typical thermoplastic forming methods such as extrusion, extrusion coating, thermoforming, blow moulding, injection, sheet, or press moulding.
• Preferred forming processes are injection moulding or extruding. Particularly preferred is injection moulding, because spacers of essentially any desired shape may be made, while avoiding waste, excessive handling, and significant labour costs. It is also possible to form a sheet of LCP and to cut the spacers from the sheet, for example, using a laser beam or a mechanical method of cutting such as a knife or saw. Any waste cuttings may be remelted and recycled.
• the spacers of the invention may have any desired form, making it possible to design the transformer shape and size to fit the end use. The spacers may be designed to fit the coils, rather than the other way round.
• a preferred form for the spacers is sheets, which may have the shape, for example, of rectangles, squares, triangles, circles, ellipses, or irregular shapes.
• the spacers may take the form of rods or sticks.
• the spacers take the form of rods, which are then used to provide a framework for building up the coils of the transformer, by supporting the coils at the circumference of the coil, or in the middle of the coil.
• Such rod-like spacers may also support sheet-like spacers, which can be placed orthogonally to the rods, between the coils of the transformer.
• the spacers of the invention may be hollow, partially hollow or solid, depending on the strength requirements of the particular spacer.
• the LCP spacers of the invention may be used in air, gas, or oil- filled transformers, but are particularly suited to use in oil-filled transformers.
• a liquid crystalline polymer herein is meant a polymer that is anisotropic when tested using the TOT test or any reasonable variation thereof, as described in U.S. patent no. 4,118,372, which is hereby included by reference.
• Useful LCPs include polyesters.
• One preferred form of LCP is "all aromatic", that is all of the groups in the polymer main chain are aromatic (except for the linking groups such as ester groups), but side groups which are not aromatic may be present.
• the melting point of the LCP is about 35O 0 C or higher, more preferably about 365 0 C or higher, and especially preferably about 39O 0 C or higher. Melting points are measured by ASTM Method D3418. Melting points are taken as the maximum of the melting endotherm and are measured on the second heat at a heating rate of 10°C/min. If more than one melting point is present, the melting point of the polymer is taken as the highest of the melting points.
• a preferred LCP is made from 4,4'-biphenol / 1 ,4-dihydroxybenzene / 1 ,4-benzenedicarboxylic acid / 2,6-naphthalenedicarboxylic acid / 4- hydroxybenzoic acid or derivatives thereof (50/50/88/12/320 molar parts) and has a melting point of about 35O 0 C.
• the molar parts of 1 ,4- benzenedicarboxylic acid / 2,6-naphthalenedicarboxylic acid can also range from about 70/30 to about 90/10.
• a second preferred LCP is made from 1,4-dihydroxybenzene / 1,4-benzenedicarboxylic acid / 2,6- naphthalenedicarboxylic acid / 4-hydroxy benzoic acid or derivatives thereof (100/5/95/100 molar parts) and has a melting point of about 35O 0 C.
• the molar parts of 1 ,4-benzenedicarboxylic acid / 2,6- naphthalenedicarboxylic acid can also range from about 5/95 to about 30/70 and the molar parts of 4-hydroxybenzoic acid can also range from about 100 to about 300.
• thermoplastic compositions may also be present in the composition. These materials should preferably be chemically inert and reasonably thermally stable under the operating environment of the moulded part in service, and/or during part formation. Such materials may include, for example, one or more of fillers, reinforcing agents, pigments, and nucleating agents. Other polymers may also be present, thus forming polymer blends. If other polymers are present, it is preferred that they are less than 25 weight percent of the composition. In another preferred type of composition, other polymers are not present except for a small total amount (less than 5 weight percent) of polymers such as lubricants and processing aids.
• the composition contains about 1 to about 55 weight percent of fillers and/or reinforcing agents, more preferably about 5 to about 40 weight percent of these materials.
• Reinforcing agents and/or fillers include glass filler, fibrous materials such as meta- or para-aramid fibres and particulates (pulp, fibrids, powder), wollastonite, titanium dioxide whiskers, and powders (particulates) such as mica, clays, calcium sulphate, calcium phosphate, barium sulphate, and talc. Some of these materials may act to improve the strength and/or modulus of the composition and/or may improve the flammability resistance (see for instance WO02/02717, which is hereby included by rerere ⁇ ce;.
• Preferred fillers/reinforcing agents include talc.
• glass filler herein is meant any relatively small particle or fibrous glass material suitable for mixing into a thermoplastic.
• Useful glass materials include so-called “E-glass”, “S-glass”, soda lime glass, and borosilicate glass.
• This filler may be in any form, such as fibre (fibreglass), milled glass (ground glass fibre), glass flake, hollow, or solid spheres. All percents by weight herein are based on the total composition containing the LCP and filler, unless otherwise stated.
• the amount of LCP in the composition is at least about 35 weight percent, more preferably at least about 45 weight percent.
• amount of filler (which in some instances may be considered a reinforcing agent) is 0.1 to about 65 weight percent, more preferably about 5 to about 50 weight percent.
• the composition have a UL-94 rating of V-1 at a thickness of 0.79 mm, more preferably a UL-94 rating of V-O at a thickness of 0.79 mm.
• the UL-94 test (Underwriter's Laboratories) is a flammability test for plastics materials, and the requirements for a V-O rating are more stringent than those of a V-1 rating.
• the composition has a Heat Deflection Temperature (HDT) at 1.82 MPa of at least about 24O 0 C 1 more preferably at least about 275 0 C, and especially preferably at least about 34O 0 C.
• the HDT is measured by ASTM Method D648.
• FIG. 1 An example of a voltage transformer according to the invention is shown in Figure 1.
• the transformer consists of high voltage coils (1) and low voltage coils (2) in separate compartments.
• the coils are made of conducting material such as copper.
• Vertical LCP spacers according to the invention (3) are designed to engage with horizontal LCP spacers according to the invention (4), by engaging tabs (5) at either end of the horizontal spacers.
• the horizontal spacers (4) fit horizontally between adjacent conducting coils.
• Figure 2 shows the horizontal spacer (4), with tabs (5) at two ends.
• Figure 3 shows a variation with tabs (5) at only one end.
• the tabs can be made in many variations, such as a "tee” shape "dogbone” shape or any other attachment shapes.
• a transformer, as depicted in Figure 1, can be built up as desired, by adding horizontal spacers (4) by clipping the tabs (5) onto the vertical spacers (3).
• horizontal spacers (4) are designed so that the tabs (5) have some degree of play when clipped into place on the vertical spacers (3). In this way the spacers (3) and (4) can accommodate changes in dimensions that can occur with temperature changes.
• Spacers according to the invention were injection moulded from an LCP made from 4,4'-biphenol / 1 ,4-dihydroxybenzene / 1 ,4- benzenedicarboxylic acid / 2,6-naphthalenedicarboxylic acid / 4- hydroxybenzoic acid (50/50/88/12/320 molar parts) and having a melting point of about 35O 0 C.
• Spacers of various dimensions and thicknesses were made.
• spacers of dimensions 30 x 89 (Width x Length) were made in 1 , 2 and 3.5mm thicknesses.
• the spacers were tested for Electrical Strength according to International Standard IEC 60243-1. This method determines the voltage at which the material breaks down, and a discharge occurs. The results are normalised by dividing by the thickness of the spacer.
• the spacers were placed between two electrodes, and the voltage between the electrodes was ramped rapidly until a discharge occurred.
• the voltage at which the discharge occurred was divided by the thickness of the spacer in mm, resulting in the dielectric strength, reported in V/mm.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Manufacturing & Machinery (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Medicinal Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Insulating Of Coils (AREA)
• Organic Insulating Materials (AREA)
• Polyesters Or Polycarbonates (AREA)
• Coils Or Transformers For Communication (AREA)

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Applications Claiming Priority (2)

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• 2007
  • 2007-03-06 US US11/714,758 patent/US20080061919A1/en not_active Abandoned
  • 2007-03-20 MX MX2008012010A patent/MX2008012010A/es unknown
  • 2007-03-20 JP JP2009501522A patent/JP2009530860A/ja active Pending
  • 2007-03-20 EP EP07753557A patent/EP1997118A1/en not_active Withdrawn
  • 2007-03-20 KR KR1020087023420A patent/KR20080103582A/ko not_active Withdrawn
  • 2007-03-20 CN CN2007800098489A patent/CN101405820B/zh active Active
  • 2007-03-20 CA CA002642705A patent/CA2642705A1/en not_active Abandoned
  • 2007-03-20 WO PCT/US2007/006938 patent/WO2007111889A1/en not_active Ceased
  • 2007-03-20 BR BRPI0709356A patent/BRPI0709356B8/pt active IP Right Grant

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