RU210354U1 - WINDING WIRE WITH RECTANGULAR COPPER CORE - Google Patents

Abstract

The utility model relates to electrical engineering and can be used, for example, in power electrical machines (for example, in the windings of power transformers), in particular, in winding subdivided wires with enamel insulation. copper conductors (when used in power windings of electrical machines) by increasing the mechanical strength of the cable winding at high temperatures (primarily at temperatures above 90 ° C) (reducing the likelihood of winding deformation) and simultaneously increasing the level of electrical insulation (electrical strength) of the wire. To achieve the claimed technical result, a new subdivided winding wire with rectangular copper conductors has been developed. Each core is covered with a layer of enamel insulation and has a longitudinal side conjugated with the corresponding side of the adjacent core. In the area of conjugation of the indicated sides, an area extended along the length of the core is made in the form of a strip of an epoxy coating of a thermosetting polymer, which provides an adhesive connection of the above sides. All cores are covered by a common insulation layer made of insulating paper. The number of rectangular current-carrying copper conductors is not more than 4. The edges of the strip with epoxy coating are equidistant from the corresponding edges of the mating area. The width of each strip of epoxy coating is W=(Z-2*r)*K, where K is an empirical dimensionless coefficient, Z is the given width of each rectangular conductive copper core, r is the radius of the rounded corners of the rectangular core. Strip thickness h, while 0.015 mm≤h≤0.025 mm. Between the layer of enamel insulation and the surface of the copper base of each of the above cores, a layer of resin based on aromatic polyamide with a thickness of 0.003 to 0.008 mm is made. 2 w.p. f-ly, 3 ill.

Description

The field of technology to which the utility model belongs.

The utility model relates to electrical engineering and can be used, for example, in power electrical machines (for example, in windings of power transformers), in particular, in winding subdivided wires with enamel insulation.

The level of technology.

In modern power electrical devices, in particular in transformers, enamelled winding wires are widely used, containing rectangular conductive wires, each of which is covered with an insulating layer of insulating varnish. To ensure the operation of the transformer, these winding wires must withstand electrodynamic mechanical loads arising in it as a result of the interaction of magnetic fields created by the current-carrying parts of the transformer during a short circuit.

From the level, a subdivided winding wire is known (RF patent No. 69307, publ. 10.12.2007), containing rectangular copper conductors, conjugated with the larger side to each other. Each core is covered with a layer of insulation made of electrical insulating varnish, and all cores are covered with a common layer of insulation made of electrical insulating paper. The disadvantage of the technical solution is the relatively low mechanical strength of the inter-core coupling, which leads to undesirable displacements of the cores (and damage to the transformer windings) at high electrodynamic loads that occur during a short circuit.

A technical solution is known (RF Patent No. 186329, published on January 16, 2019) - a transposed winding wire. It contains at least 5 rectangular conductors (strands) with enamel insulating coating and adhesive epoxy coating. Along the entire length, the conductors change their position in the wire along a rectangular contour. The wire also has insulation covering all the cores. The adhesive epoxy coating in the form of a strip covers no more than 80% of the surface of each wide side of the rectangular conductor. The disadvantages of this technical solution include the limitation of its use for transposed wires, and in the wire, according to the technical solution, a minimum of 5 cores is required, in addition, the distribution of the adhesive epoxy coating in the form of a strip is not optimized taking into account the shape of a typical rectangular core, which usually has rounded corners.

The closest analogue of the utility model (prototype) is a technical solution (see international application WO 1998014964 A1, published on 04/09/1998) - stranded subdivided wire for windings of electrical machines and devices. The winding wire contains rectangular current-carrying copper wires, each of which is covered with a layer of enamel insulation and has a conjugated longitudinal side with the corresponding side of the neighboring wire, while in the area of the mating of the above mated sides between them, an area extended along the length of the wire is made in the form of an epoxy coating strip, providing adhesive connection of said mating sides. All cores are covered by a common insulation layer made of insulating paper. The resin coated area is approximately 80-95% of the contact surface (i.e. the width of the epoxy coated area is approximately 95-80% of the contact surface width, and the edge area of the strand pads is free of epoxy coating). The disadvantages of this technical solution include insufficiently accurate optimization of the position of the epoxy coating strip relative to the edges of the mating area, insufficiently accurate optimization of the contact surface area (in width), which does not take into account the features of the actual geometry of rectangular conductors (it has rounded edges of a given radius) and the thickness of the epoxy coating . This can lead to an increase in the likelihood of partial discharges on the windings during a short circuit on extruded (during wire assembly and during operation) epoxy microparticles (due to the excessive width of the epoxy resin area). Also, in the specified technical solution, the adhesion strength between the core (the surface of the copper base) and the insulating layer is not high enough when the winding is heated above 95°C. These factors reduce the resistance of the winding of an electric machine to dynamic forces arising from a short circuit in the circuit and, accordingly, reduce the working life of the electric machine.

Disclosure of the essence of the utility model

The objective of this utility model is to increase the electrodynamic resistance of power electrical machines using subdivided winding wires (windings) with enamel insulation and rectangular conductive cores. In particular, it is necessary to improve the strength characteristics of power transformer windings at high temperatures, which allows the transformer to work for a long time without damage, even under conditions of high electrodynamic forces arising in the windings as a result of the interaction of magnetic fields created during a short circuit.

The main technical result of the utility model is to increase the service life of a subdivided winding wire with rectangular copper conductors (when used in power windings of electrical machines) by increasing the mechanical strength of the cable winding at high temperatures (primarily at temperatures above 90 ° C) (reducing the likelihood of deformation winding) and at the same time increasing the level of electrical insulation (electrical strength) of the wire. An additional advantage of this utility model is the simultaneous achievement (with the main technical result) of the effect of reducing the amount of unwanted accumulations of epoxy varnish on the rounded edges of the strands. This allows not only to reduce the likelihood of a corona discharge - i.e. to maintain and/or increase the electrical strength of the cable, but also to reduce the consumption of epoxy materials and reduce the overall dimensions of the winding wire with rectangular copper conductors. In addition, these wires have a smaller spread in the value of mechanical strength, i.e. more stable reproducible parameters of mechanical strength. A positive additional technical effect is the increase in the electrical strength of the insulation under the action of large electrodynamic forces and thermal loads that occur during a short circuit in the circuit of a power electric machine.

To achieve the claimed technical result, a new subdivided winding wire with rectangular copper conductors has been developed. Each core is covered with a layer of enamel insulation and has a longitudinal side conjugated with the corresponding side of the adjacent core. Between them, in the area of conjugation of the indicated sides, an area extended along the length of the core is made in the form of a strip of epoxy coating, providing an adhesive connection of the above sides. All cores are covered by a common insulation layer made of insulating paper. The number of rectangular conductive copper conductors is not more than 4.

Epoxy coated strip has the following characteristics. The edges of the epoxy coated strip are equidistant from the corresponding edges of the mating region. The width of each strip of epoxy coating is W=(Z-2*r)*K, where K is an empirical dimensionless coefficient that satisfies the condition 0.6≤K≤0.8, Z is the specified width of each rectangular conductive copper core, r is the radius of the rounded corners of the rectangular core, in this case, the condition 0<r<Z/4 is satisfied. The thickness of the epoxy coating strip h, while the condition 0.015 mm≤h≤0.025 mm is fulfilled. In the winding wire, Z and r can meet the conditions of 0.3mm≤r≤1.25mm, 3mm≤Z≤20mm, respectively, and the height of the rectangular conductive copper core H can satisfy the condition of 0.8mm≤H≤6.0mm.

The enamel insulation layer may be made of polyvinylformal resins. Between the enamel insulation layer and the surface of the copper base of each of the above cores, a layer of resin based on aromatic polyamide with a thickness of 0.003 to 0.008 mm can be made. The above epoxy coating may contain a thermosetting epoxy binder.

Brief description of the drawings

Fig. 1 Subdivided winding wire with rectangular copper conductors, assembled (cross section).

Fig. 2 Rectangular epoxy-coated copper conductor on mating side (cross section).

Fig. 3 An example of comparative tests of the mechanical strength of a non-optimized wire (prototype) and a wire according to the claimed technical solution.

Implementation of the utility model

On FIG. 1 shows a cross-section of a subdivided winding wire 1 with two rectangular copper conductors 5 (in a subdivided wire, by definition, the strands run parallel to each other). Each core 5 is covered with a layer of enamel insulation 3. The height of the core is H, the width of the core is Z, and r is the radius of the rounded corners (hereinafter roundings) of the rectangular core 6 (for each of the four edges of the core) (see Fig. 2). The cores face each other with their wide sides 7 and 8 (i.e., the standard pairing of the cores is made - with the wide sides), in other words, 7 is the surface of the mating side of the core 1, and 8 is the surface of the mating side of the core 2. The width of the conjugated area S (see. Fig. 2) practically coincides with the width Z of a rectangular conductive copper core (having the same dimensions) for two mating cores adjacent to each other with their sides. The mating area of the wires can be limited by the mating sides of adjacent wires and the inner surface of the insulating paper 2 covering these wires. At the same time, in the area of conjugation of the above mating sides - between them there is an area extended along the length of the core in the form of a strip 4 of an epoxy coating. It provides an adhesive connection between mating sides of the strands. The edges of the epoxy coated strip are equidistant from the corresponding edges of the mating region with width S. The thickness of the epoxy coated strip 4 is h and its width is W.

Fig. 2 shows a conditional rectangular coordinate system with the axes Ox and Oy centered at the point O (located in the center of the cross section of the core, the central axis of symmetry of the core passes through the point O, which will be perpendicular to the xOy plane). The epoxy coating strip may have an axis of symmetry coinciding in direction with the central axis of symmetry of the core. The epoxy coating (thermosetting epoxy binder) has both the necessary adhesive force and, accordingly, the required mechanical strength in the event of a short circuit in power windings made of subdivided wire. In addition, all cores 5 are covered by a common insulation layer made of insulating paper 2, which is tightly wound over the assembly, providing not only the necessary additional level of insulation of the windings, but also the necessary additional strengthening of the assembly. In the specified stranded wire, increased mechanical strength is provided and the epoxy coating in it (for example, a thermosetting epoxy binder) has the necessary adhesive force, the required mechanical strength, which guarantees a longer operation of the wire even in the event of a short circuit in the windings.

To increase the adhesion strength between the insulating layers of adjacent wires, it is required to maximize the contact area. As a first approximation, the width of the epoxy varnish strip can be calculated from the formula. W=Z-2*r, where Z is the width of the core, and r is the radius of the conductor fillets. However, it must be taken into account that when pressure is applied to the conductors at the time of their gluing, the epoxy resin can be squeezed out onto the radius fillets. In this case, negative effects occur, such as the occurrence of partial discharges on extruded (on the edges of the conjugated zone with a width S) microparticles (lumps) of epoxy resin. Therefore, it is necessary to further reduce the application width and select the optimal thickness of the epoxy layer p. It has been experimentally established that the spreading of the varnish occurs by about 20-30%. The location of the edges of the strip (with epoxy coating) must be equidistant from the corresponding edges of the mating area. The uneven location of different edges (technological) of the strip up to 5-7% (i.e. one edge of the strip is closer to the edge of the conjugated zone than the other by no more than 5-7%) is acceptable and it is considered that the equidistance is maintained. This almost strict symmetrical arrangement of the strip with respect to the edges of the conjugated zone reduces the adverse effects of the formation of epoxy microparticles. Taking into account the provision of the necessary adhesive strength of the connection of the mating zones of the cores and minimizing the above undesirable effects, an empirical formula was selected to optimize the application width of such an epoxy layer (for an epoxy strip with equidistant edges from the edges of the mating zone and the thickness of the epoxy coating h, 0.015 mm≤h≤0.025 mm ). Epoxy coating strip width W=(Z-2*r)*K, where K is an empirical dimensionless coefficient 0.6≤K≤0.8, Z is the specified width of each rectangular conductive copper core (standardly the same), r is the core rounding radius, while the condition 0<r<Z/4 is satisfied.

Note that the feature of the technical solution "the number of rectangular current-carrying copper conductors in a subdivided wire is not more than 4 is necessary for this design solution. This is due, in particular, to the fact that the proposed wire design is optimized specifically for wires containing no more than 4 conductors. In the case of a larger number of wires (and, accordingly, other mutual arrangements of the cores relative to each other (and with a different arrangement of conjugate tunings), other design solutions may be required with different parameters of the epoxy coating (and possibly a different thickness).

The insulating layer is an enamel layer for conductors, quite often made of resins based on polyvinylformal, since this material provides a stable and stable dielectric strength of the insulation in electrical insulating oil. The disadvantage is the low temperature resistance. The glass transition temperature of polyvinylformal is 85-95°C. In the event of a short circuit in the transformer circuit, a sharp increase in the temperature of the core of the wire occurs, which heats the layers of the polyvinylformal insulating coating adjacent to the core. The temperature of the adjacent layers in this case reaches 120°C and higher, as a result of which the polyvinyl formal softens and, to a certain extent, loses its adhesive strength. To solve this problem, a thermoset epoxy coating resin is used in combination with the application of a thin layer of aromatic polyamide resin (0.003 to 0.008 mm thick), which improves the adhesion of copper to the insulation layer by 10%, (and increases the dielectric strength of the wire) and when the temperature rises above 90°C, there is no loss of adhesion, due to the fact that the polyamide layer has excellent heat resistance with a softening point of about 180°C.

Thus, these modifications of the wire additionally help to increase the service life of the subdivided winding wire with rectangular copper conductors (when used in power windings of electrical machines) by increasing the mechanical strength of the cable winding. We emphasize that it is the combination of the above resin based on aromatic polyamide with the use of a thermosetting epoxy binder, which does not melt when the temperature rises even above 90 ° C, which additionally guarantees the strength of the bonding wire at high temperatures.

An example implementation of the utility model

Various variants of winding subdivided wire with rectangular copper conductors (with 2, 3 and 4 conductors) were tested. The operating parameters of the copper conductors were selected taking into account GOST 434-78 "Rectangular-section wire and copper busbars for electrical purposes specifications" or IEC 60851-0-2. In particular, a variant of wire with soft copper wire (PMM) was used. For example, PMM 0.80 × 3.00 mm. Various design options were considered, including the option of using an additional layer of resin based on an aromatic polyamide with a thickness of 0.003 to 0.008 mm and an epoxy coating with a thermosetting epoxy binder. Bonding strength tests were carried out taking into account GOST IEC 60851-3-2016 "WINDING WIRES Test methods Part 3 Mechanical properties". They showed that for constructive variants of the wire in accordance with the present technical solution, there is an increase in the mechanical strength (gluing strength) of the cable winding using the wire according to the present utility model) at high temperatures (see Fig. 3).

Tests have shown that the claimed technical solution provides an increase in the dynamic resistance of the windings of electrical machines in the entire temperature range up to 120°C. The technical solution also provides a reduction in the overall dimensions of the wire due to the absence of an epoxy adhesive layer on the non-mating sides of the wire (where there is no need for adhesive bonding). The electrical strength of the insulation is improved due to the absence (or a significant reduction in the amount) of uneven accumulations of epoxy binder (forming an epoxy coating) on the ribs and radii of curvature. (In places of such accumulations, the likelihood of corona discharges increases - leading to a decrease in electrical strength).

As a result of using the utility model, along with an increase in electrical strength, there is a significant increase in the mechanical strength (gluing) of the conductors, which is required to increase the resistance of the electrical machine winding to dynamic forces arising from a short circuit in the circuit and to prevent winding deformation. In general, there is a complex increase in factors that provide increased strength parameters of the wire - the adhesive strength between the core wire and the insulating layer increases, the adhesive strength between the insulating layer and the insulating layer of the adjacent wire increases, and the strength parameters of the wire are maintained when the temperature rises above 90 ° C (at least , up to 130°С).

Claims (3)

1. Winding wire subdivided with rectangular copper conductors, each of which is covered with a layer of enamel insulation and has a longitudinal side mated with the corresponding side of the adjacent conductor, while between them in the area of the mate of these sides, an area extended along the length of the conductor is made in the form of a strip of epoxy coating , providing an adhesive connection of the above sides, while all the cores are covered by a common insulation layer made of insulating paper, characterized in that the number of rectangular conductive copper cores is not more than 4, the edges of the epoxy-coated strip are equidistant from the corresponding edges of the mating area, while the width of each epoxy coating strip W=(Z-2*r)*K, where K is an empirical dimensionless coefficient that satisfies the condition 0.6≤K≤0.8, Z is the specified width of each rectangular conductive copper core, r is the radius of the rounded corners of the rectangular core, while the condition 0<r<Z/4 is satisfied, while the thickness of the strip of epok cover h, while the condition 0.015 mm ≤ h ≤ 0.025 mm is met. 2. Winding wire subdivided according to claim 1, characterized in that Z and r satisfy the conditions 0.3 mm≤r≤1.25 mm, 3 mm≤Z≤20 mm, respectively, and the height of the rectangular conductive copper core H satisfies the condition 0 .8mm≤H≤6.0mm. 3. Winding wire subdivided according to claim 1, characterized in that the layer of enamel insulation is made of resins based on polyvinylformal, while between the layer of enamel insulation and the surface of the copper base of each of the above cores, a layer of resin based on aromatic polyamide with a thickness of 0.003 to 0.008 mm, and the above epoxy coating contains a thermosetting epoxy binder.

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