SE520890C2 - Electromagnetic apparatus with magnetic field generating electric circuit - Google Patents

Abstract

The apparatus includes a magnetic field generating electric circuit with one or more electric conductors with insulation systems. The system comprises electric insulation (4) formed by a solid insulation material. Exteriorly of the insulation is an outer layer (5). This layer has an electrical conductivity higher than the insulation making the outer layer capable by connecting with earth or low potential of operating to equalise potential and subsequently enclose the electric field arising as a consequence of the conductor (2) inwardly of the outer layer.

Description

l5 20 25 30 35 'š2o, š§d the motors with rated power from a few hundred KVA up to over 1000 MVA with rated voltage from 3-4 kilovolts and up to very high transmission voltages, 400 kilovolts to 800 kilovolts or higher.

Although the following description of the state of the art with regard to the second aspect mainly relates to power transformers, the invention is also intended to be applicable to reactors, which as is known can be made single-phase and three-phase. In terms of insulation and cooling, there are basically the same transformers. There are embodiments which thus carry air-insulated and oil-insulated, self-cooled, pressure-oil-cooled, etc. reactors. Although reactors have unwinding (per phase) and can be carried out both with and without a magnetic core, the description of the state of the art is largely relevant also for reactors.

The electrical circuit for generating or by means of magnetic fields may in some embodiments be air-wound but usually comprises a magnetic core of laminated, normal or oriented, I or sheet or other, for example amorphous powder-based, material or other intentional to allow alternating current and a winding. The circuit often includes some form of cooling system etc. In the case of a rotating electric machine, the winding can be located in the stator or rotor of the machine or in both.

The invention also comprises 'a method for electric field control' in: a in electromagnetic device cx fl in a method for manufacturing a magnetic circuit.

POSITION OF THE TECHNOLOGY In order to be able to explain and describe the invention, the prior art will be described below with regard to both a rotating electric machine and a power transformer. 10 15 20 25 30 35 3 520 890 Rotary electric machine Such a rotary electric machine will be exemplified on the basis of a synchronous machine. The first part of the report mainly relates to the magnetic circuit of such a machine and how it is constructed according to classical technology. Since the magnetic circuit referred to in most cases is in the stator, the magnetic circuit below will generally be referred to as a stator with a laminated sheet metal core, the winding of which will be referred to as stator winding, and the grooves in the sheet metal core of the winding will be referred to as single track.

Most synchronous machines have a field winding in the rotor, there and an alternating current winding Sometimes the latter main flow is generated with direct current, in the stator. The synchronous machines are usually three-phase. the synchronous machines are designed with pronounced poles. has the AC winding in the rotor.

The stator body for larger synchronous machines is often made of sheet steel with a welded construction. The sheet metal core is normally made of lacquered 0.35 or 0.5 mm electrical sheet. For larger machines, the plate is punched in segments that are attached to the stator body with the plate core, wedges / salmon are held together. with pressure fingers and pressure rings.

For cooling the windings of the synchronous machine, three different cooling systems are available. During air cooling, both the stator and rotor windings are cooled by flowing cooling air. The cooling air ducts are found in the stator plate as well. as in. rotor. For radial ventilation and air cooling, the sheet metal core is, at least for medium and large machines, divided into packages with radial and axial ventilation ducts embedded in the core.

The cooling air can consist of ambient air, but at higher effects, mainly closed, cooling systems with heat exchangers are used.

Hydrogen cooling is used in turbo generators and in large l10 l5 20 25 30 4 520 890 synchronous compensators. The cooling method works in the same way as for air cooling with a heat exchanger, but instead of air as coolant, hydrogen gas is used. Hydrogen has a better cooling capacity than air, but difficulties arise in sealing and monitoring leaks. For turbogenerators in the higher power range, it is known to apply water cooling of both the stator and rotor windings. The cooling channels consist of tubes that are placed inside conductors in the stator winding. A problem for large machines is that the cooling tends to be uneven and that there are thus temperature differences across the machine.

The stator winding is placed in grooves in the plate core and where the grooves usually have a cross section like a rectangle or like a trapezoid. Each winding phase consists of a number of series-connected coil groups and each coil group of a number of series-connected coils. The different parts of the coil are called the coil side for the part that is placed in the stator and the coil for the part that A coil consists of one or height and / or width. The middle is outside the stator. several conductors joined together in each conductor there is a thin insulation, eg epoxy / fiberglass.

The coil is insulated against the track with a coil insulation, ie an insulation intended to withstand the machine's rated voltage against ground. Various plastic, lacquer and fiberglass materials can be used as insulation material. Commonly used so-called Mica tape, which is a mixture of mica and hard plastic, specially developed. to provide resistance to partial discharges, which can quickly break down the insulation. The insulation is applied to the skein by wrapping the Mica tape around the skein in several layers. The insulation is impregnated and then the coil side is applied with a carbon-based paint to improve the contact with the surrounding stator which is connected to earth potential.

The conductor area of the windings is determined by the current current and by the cooling method. Conductors and coils are usually designed with a rectangular shape to maximize the amount of conductor material in the groove.

A typical tangle is formed by so-called roebel rods, where some of the steel can be made hollow for coolant. A ruble rod consists of a plurality of rectangular, parallel-connected copper conductors, which are transposed 360 degrees along the track. Ring land rods with 540 degree transpositions and other transpositions also occur. The transposition is reddish to avoid the emergence of circulating currents generated in a cross section of the conductor material seen from. the magnetic field.

For mechanical and electrical reasons, a machine cannot be made as large as it should be. The machine power is mainly determined by three factors: ß - The conductor area of the windings. At normal operating temperature, for example, copper has a maximum value of 3-3.5 A / mm2.

- Maximum flux density (magnetic flux) in the stator and rotor material.

- Maximum electric field strength in the insulating material, the so-called electric rock strength.

Multiphase AC windings are made as single- or two-layer windings. For single-layer windings there is only one warp side per track, for two-layer windings two warp sides per track. Two-layer windings are usually made as transition windings, while in this context current single-layer windings can. performed sonx transition winding or ~ plane winding. In the case of transition winding, only one (or possibly two) torsional widths occur, while planar windings are performed as concentric windings, ie with widely varying torsional widths. Twisting width refers to the distance in arc measured between two twisting sides belonging to the same twist, either in relation to the actual pole division or in the number of intermediate track divisions. Usually different variants of coding are applied, eg step shortening to give the winding desired properties. The winding type mainly describes how the coils in the grooves, the coil sides, are connected outside the stator, ie at the coil ends. lO 15 20 25 30 35 520 6890 Outside the stator plate package, the coil is not provided with a painted semiconducting earth potential layer. The end face is normally equipped with an E-field guide in the form of so-called glow protection varnish to convert a radial field to an axial field, which means that the insulation on the end faces ends up at a high potential relative to earth. This sometimes gives rise to glitter in the region of reversion, which can be destructive. The so-called field control points' at. the turntables pose problen1 for a rotating electric machine.

Normally, all larger machines are made with 2-layer winding and equally large skeins. Each tangle is placed with one side in one This means At several layers and the other side in the other layer. that all coils cross each other in reverse. layer than two, these junctions complicate winding work and impair the reversal.

It is generally known that the connection of a synchronous machine / generator to a power grid must take place via an A / Y-connected so-called "step-up" transformer, since the voltage of the power grid is usually at a higher level than the voltage of the rotating electric machine. . This transformer thus, together with the synchronous machine, forms integral parts of a plant. The transformer is an additional cost and also has the disadvantage that the overall efficiency of the system is reduced. If it were possible to manufacture machines for significantly higher voltages, the "step-up" transformer can thus be excluded.

In recent decades, there has been a desire for rotating electric machines for higher voltage than has been possible to design and manufacture before. The maximum voltage level that according to the state of the art has been possible to achieve for synchronous machines with good output in the coil production is 25-30 kV. 10 l5 20 25 30 35 5207 890 Some attempts at innovation in the construction of synchronous machines are described, among other things, in an article "Water-and-oil-cooled Turbogenerator TVM-300" in J. Elektrotechnika, Nr. 1, 1970, pages 6-8, in US 4,429,244 "Stator of generator" and in Russian patent specification CCCP patent 955369.

The water- and oil-cooled synchronous machine described in J.

Elektrotechnika is intended for voltages up to 20 kV. The article describes a new insulation system consisting of the whole The oil can then be used as a cooling To prevent oil / paper insulation, which makes it possible to soak the stator in oil. dium while being used as insulation. oil in the stator to leak out towards the rotor, there is a dielectric oil separating ring at the inner surface of the core.

The stator winding is made of conductors with an oval hollow shape provided with oil and paper insulation. The warp sides with their insulation are held in the grooves with a rectangular cross-section by means of wedges. Oil is used as a coolant both in the hollow conductors and in holes in the major walls. Such cooling systems, however, mean that there will be a large number of connections of both oil and electricity at the reversers. The thick insulation also means an increased radius of curvature on the conductors, which in turn leads to an increased size of the coil extension.

The above-mentioned US patent relates to the stator part of a synchronous machine which comprises a magnetic core of laminated sheet metal with trapezoidal grooves for the stator winding. The grooves are tapered because the need for insulation of the stator winding is less towards the rotor where the part of the winding that is closest to the neutral point is located. The stator part also comprises a dielectric oil separating cylinder closest to the inner surface of the core. This part may increase wagnetise- vw 'nrrflfwmlwmwraå- velnf-Ã fi ri- a mzaclr-É fi' mf-nn Male: -v-w nn 'Cf-: M-nvl inr-ll ..

J-LLÅÛ L / šllívåLa .L J-ÉQ-LVG \ .rÅÅ \ ll \ ŧJJ \ -J-LÅ \ Å \ ø \ ÅÅÅ ÄLLÅÅLZ J - LÅLÜ LJSfQÅLQ / L-Lal-ÅÅJ ningen is made of oil-soaked cables with the same diameter for each spool bearing. The bearings are separated from each other by 10 15 20 25 30 35 520 §9o by means of spacer elements in the grooves and secured with wedges. What is special about the winding is that it consists of two so-called half-windings connected in series. One of the two half-windings is centrally located inside an insulating sleeve. The stator winding conductors are cooled with ambient oil. A disadvantage of so much oil in the system is the risk of leakage and the large remediation work that can result from a fault condition. The parts of the insulating sleeve that are located outside the grooves have a cylindrical part and a conical shield electrode whose task is to control the electric field strength in the area where the cable leaves the plate.

CCCP 955369 states in another attempt to increase the rated voltage of the synchronous machine that the oil-cooled stator winding consists of a low-voltage cable with the same dimension for all bearings. The cable is placed in stator rafters shaped as circular radially placed openings corresponding to the cross-sectional area of the cable and the necessary place for fixing and coolant. surrounded by and fixed in insulating pipes.

The various radially placed bearings of the winding Insulating spacers fix the pipes in the stator groove. Due to the oil cooling, an inner dielectric ring is also needed here for sealing the oil coolant against the internal air gap. The construction shown has no stepping of the insulation or of the stator tracks.

The construction has a very narrow radial waist between the various stator grooves, which means a large groove leakage flow which significantly affects the magnetization needs of the machine.

A report from the Electric Power Research Institute, EPRI, EL-3391 from April 1984 reports a review of machine concepts for achieving higher voltage in a rotating electric machine in order to be able to connect a machine to such a power grid without an intermediate transformer. A solution is judged by the inquiry to provide good efficiency gains and major economic benefits. The main reason why it was judged in 1984 that it was possible to start developing generators for direct connection to power grids was that. then had developed a superconducting rotor. The large magnetizing capacity of the superconducting field makes it possible to use air gap winding with sufficient thickness to withstand the electrical stresses. By combining the most promising concept according to the project to construct a magnetic circuit with winding, so-called "monolithic cylinder armature", a concept where two cylinders of conductors are enclosed in three cylinders of insulation and the whole structure is attached to an iron core without teeth. rotary electric machine for high voltage could be directly connected to a power grid. must be made thick enough to withstand mesh-to-mesh and the solution meant that the main insulation mesh-to-earth potentials. The insulation system which, after an overview of all technology known at the time, was deemed necessary to withstand an increase to higher voltage was that normally used for power transformers and which consists of dielectric liquid impregnated cellulose press disks. Obvious disadvantages of the proposed solution are that in addition to requiring a superconducting rotor, a very thick insulation is required which increases the machine size.

The inverters must be insulated and cooled with oil or freons to control the large electric fields at the ends. The entire machine must be hermetically sealed to prevent the liquid dielectric from absorbing moisture from the atmosphere.

In the manufacture of rotating electrical machines according to the prior art, the winding is produced with conductors and insulation systems in several stages, the winding having to be formed in advance before it is mounted on the magnetic circuit. Impregnation for the production of the insulation system is carried out after mounting the winding on the magnetic circuit.

Power transformer 10 15 20 25 35 520 låfao In order to be able to place a power transformer / reactor according to the invention in its proper context and thereby be able to describe the new thinking that the invention entails and the advantages that the invention possesses relative to the state of the art, Below is a relatively comprehensive description of a power transformer as it is performed today and the limitations and problems that exist with regard to calculation, construction, insulation, earthing, manufacture, use, testing, transport, etc. of these transformers.

In general, the main task of a power transformer is to allow the exchange of electrical energy between two or more electrical systems of usually different voltages with the same frequency.

A conventional power transformer comprises a transformer core hereinafter referred to as a core, often of laminated oriented sheet, usually of ferrosilicon. The core consists of a number of core legs connected by yokes which together form one or more core windows. Transformers with such a core are often called number of core transformers. Around the core bones there are windings which are usually referred to as primary, secondary and control winding. In the case of power transformers, these windings are practically always concentrically arranged and distributed along the length of the core legs. The core transformer usually has circular coils and a stepped leg section to fill the coils as close as possible. Other types of core constructions are also known, such as those included in so-called sheath transformers. These are often designed with rectangular coils and a rectangular leg section.

Conventional power transformers, in the lower part. of is sometimes performed with air cooling for In order to the aforementioned power range, to eliminate the inevitable own losses. 10 l5 20 25 30 35 ll 520 890 protect against contact and possibly to reduce the transformer's external magnetic field, it is then often provided with an outer casing provided with ventilation openings.

However, most conventional power transformers are oil-cooled. the very important function of the insulation medium. An oil One of the reasons for this is that the oil also has a cooled and oil-insulated power transformer is surrounded by an outer box, as the description below follows, very high demands are placed on. As a rule, means are provided for water cooling of the oil.

The following part of the description will for the most part be attributable to oil-filled power transformers.

The windings of the transformer are formed by one or more series-connected coils built up of a number of series-connected turns.

The coils are also provided with a special device to be able to allow switching by means of screw connections or more often by means of a special switch maneuverable in connection with the ladder. In the event that switching can take place for a transformer under voltage, the switch is called a winding switch, while in another case it is called a switching switch.

In the case of oil-cooled and oil-insulated power transformers in the upper power range, the switching elements of the winding couplers are placed in special oil-filled containers with a direct connection to the transformer's load. The switch elements are operated purely mechanically via a motor-driven rotating shaft and arranged so that there is a rapid movement during the switching at open contact and a slower movement when the contact is to be closed. The winding couplers as such are, however, II 'l -vw-ww of Å a * _' Å .-. ^ - ~. ^ Ål _-_, _, __.__ '_ .. ._ plâCeràdG l S] âlVâ tïâïïSfOinxxatt / iladaii . Viu ma Luviciiugcn occur arcs and sparks. This leads to degradation of the oil in the tanks. To obtain smaller arcs l0 l5 20 25 35 12 j 520 890 and. hence. also. less soot formation and Inner wear on to This is because those contacts are the winding couplers normally connected to the high voltage side of the transformer. currents that need to be disconnected or connected are smaller on the high voltage side than if the winding switches were connected to the low voltage side. Fault statistics on conventional oil-filled power transformers show that it is often the winding couplers that give rise to faults.

In the lower power range of oil-cooled and oil-insulated power transformers, both the winding couplers and their switching elements are located inside the box. This means that the above-mentioned problem of degradation of the oil due to arcs during operation, etc., affects the entire oil system.

What. With regard to piled or induced voltage, it can be roughly said that a voltage which is stationary over a winding is distributed equally on each revolution of the winding, i.e. that the rotational voltage is equal on all revolutions.

From an electrical potential point of view, however, the situation is completely different. One end of a winding is usually connected to ground. However, this means that the electrical potential of each revolution increases linearly from practically zero of the revolution closest to the earth potential up to a potential of the revolutions at the other end of the winding which corresponds to the applied voltage. This potential distribution determines the structure of the insulation system because one must have sufficient insulation both between adjacent turns of the winding and between each turn and earth.

The turns in a single coil are normally combined into a geometrically cohesive unit, physically separated from the other coils. The distance between the coils is also determined by the dielectric stress that can be allowed to occur between the coils. This thus means that a certain insulation distance between the coils is also required 10 15 20 25 30 35 13 52Û 89Û. According to the above, sufficient insulation distances are also required for other electrically conductive objects that are in the electric field from the electric potential occurring locally in the coils. It thus appears from the above that for the individual coils the voltage difference internally between physically adjacent conductor elements is relatively low while the voltage difference outwards towards other metal objects, here including other coils, can be relatively high. The voltage difference is determined partly by the voltage, induced by magnetic induction, and distributed occur from a connected external electrical system on the transformer and partly by the capacitive voltages that can external connections. In addition to operating voltage, the voltage types that can come in externally include AC voltages and switching voltages.

In the coils' current conductors, additional losses occur due to the magnetic leakage field around the conductor. In order to keep these losses as low as possible, especially for power transformers in the upper power range, the conductors are normally divided into a number of conductor elements, often connected in parallel, during operation. These strands must be transposed in such a pattern that the induced voltage in each strut becomes as equal as possible and so that the difference in induced voltage between each pair of strands becomes as small as possible so that internally circulating current components can be kept down on a from a loss point of view reasonable level.

In the design of transformers according to the prior art, it generally applies that one strives to have as large an amount of conductor material as possible within a given area limited by L.. - the so-called transformer window, generally referred to as achieving as high a filling factor as possible. Within the available space, in addition to the conductor material, there shall also be the coil's associated insulation material, partly internally between the coils and partly to other metallic components, including the magnetic core.

The insulation system partly within a coil / winding and partly between coils / windings and other metal parts is normally designed as a solid cellulose- or lacquer-based insulation closest to the individual conductor element and outside there of solid insulating cellulose and liquid, possibly also gaseous, tion. Windings with insulation and any bracing parts in this way represent large volumes that will be exposed to high electric field strengths that occur in and around the active electromagnetic parts of the transformer. In order to be able to predetermine the dielectric stresses son1 arises' and. achieve. one. dimensioning with minimal risk of collapse, good knowledge of the properties of the insulation material is required. It is also important to create such an ambient environment that it does not change or reduce the insulation properties. the insulation system for high voltage The prevailing power transformers today consist of cellulose material as the solid insulation and transformer oil as the liquid insulation. The transformer oil is based on so-called mineral oil.

The transformer oil has a dual function because, in addition to the insulated function, it also actively contributes to cooling the core, winding, etc. by transporting away the transformer's heat loss. Oil cooling requires an oil pump, external cooling element, expansion coupling, etc.

LS The electrical connection between the outer of the transformer a 1 Ü clni-nínrwnv n fl h Hz: nšåv-nqncf- anQlnf - nza cnmlarnn / linrqninrwnrnn r: - oluciilllnc ... oc ... ut, H-Åluvv- ... oldcllu .. .pel ._. lc., ........ o ...._... 3.l _ .. o. c is a bushing intended for a conductive connection through the box which, in the case of oil-supplied power transformers around 1020 25 30 35 15 520 B90, provides the transformer itself. The bushing is usually a separate component fixed to the box and is built to meet existing insulation requirements both on the outside and inside of the box, while at the same time it must be able to withstand current current loads and the resulting current forces. It should be noted that the same requirements for the insulation system as described above with regard to windings also apply to the required internal connections between coils, between bushings and coils, different types of switches and the bushings as such.

All metallic components inside a power transformer are normally connected to a given earth potential with the exception of the live conductors. This avoids the risk of unwanted and difficult-to-control potential increase due to capacitive voltage distribution between high-potential current conductors and earth. Such an unwanted potential increase can give a so-called glimpse. Glim- which partial- elevated voltage and cause of partial discharges, ning can be revealed in the normal delivery tests, wise occurs at, compared with. rating data, frequency. Glitter can cause damage during normal operation.

The individual coils in a transformer must have such a mechanical dimensioning that they can withstand the stresses that occur as a result of occurring currents and consequent current forces during a short-circuit process. Normally, the coils are designed so that occurring forces are absorbed within each individual coil, which in turn can mean that the coil cannot be dimensioned optimally for its normal function during normal operation.

Within a narrow range of voltages and power of oil-filled power transformers, the windings are designed as so-called belts. This means that the previously mentioned individual conductors have been replaced by thin belts. Band winding power lines 10 l5 20 25 30 35 16 520 890 formers are manufactured for voltages up to 20-30 kV and for outputs up to 10-30 MW.

The isolation system of power transformers in the upper power range requires a relatively complicated precondition. in order to make the best use of the insulation system's properties in order to build even special manufacturing measures. good insulation must be achieved, the insulation system must have a low moisture content, calculated with the surrounding oil and the risk of residual In order for the solid part of the insulation to be well imp- "gas" pockets in the solid part must be minimal. ensure this is carried out during manufacture, a special drying and impregnation process on a complete core with windings before it is put down in a box. After this drying and impregnation process, the transformer is placed in the box. sowx then closes. Before. When refilling with oil, the box with submersible transformer must be emptied of all air.

This is done in connection with a special vacuum treatment. When this has been carried out, oil is added.

In order to be able to obtain the promised service life, etc., in connection with the vacuum treatment, pumping out to an almost absolute vacuum is required. This thus presupposes that the box surrounding the transformer is designed for full vacuum, which means significant consumption of material and manufacturing time.

If electrical discharges occur in an oil-filled power transformer or if there is a local significant increase in the temperature of any part of the transformer, the oil is read and gaseous products are dissolved in the oil. The transformers are therefore generally equipped with monitoring devices for detecting gas dissolved in the oil.

For weight reasons, large power transformers are transported without oil. Installation of the transformer on site at a customer requires in its. turn renewed. vacuum treatment. This is also a 10 l5 20 25 30 35 17 520 890 process soul also must be repeated * each time the box. has been opened for any action or inspection.

It is obvious that these processes are very time-consuming and costly and constitute a significant part of the total time for production and repair, while at the same time requiring access to extensive resources.

The insulation material in conventional power transformers makes up a large part of the total volume of the transformer. For a power transformer in the upper power range, oil quantities in the order of 100s of cubic meters of transformer oil can occur. The oil, which shows some resemblance to diesel oil, is low-liquid and has a relatively low flash point. It is thus obvious that oil together with the cellulose constitutes a non-negligible fire risk in the event of unintentional heating, for example in the event of an internal spill and with oil spills caused by this.

It is also obvious that there is a very big transport problem, especially with oil-filled power transformers. One in the Upper Power Range can have a weight of up to 30-40 tons. It is realized that the external construction of the transformer sometimes has to be adapted to the current trans-tunnels port profile, ie for possible passage of bridges, etc.

The following is a brief summary of the state of the art with respect to oil-filled power transformers and of what can be described as limiting or problem areas for these: An oil-filled power transformer - comprises an outer box in which a transformer consisting of a transformer core with coils, oil for insulation and cooling, mechanical stay devices 10 15 20 25 18 520 890 devices of various kinds, etc. Very high mechanical requirements are placed on the drawer, after-season, without. oil but with a transformer, must be able to be vacuum treated to almost full vacuum. The box requires rather extensive manufacturing and testing processes and the large external dimensions of the box also usually cause major transport problems. usually includes a so-called pressure oil cooling. This cooling method requires access to an oil pump, external cooling elements, expansion vessels and coupling, etc. includes an electrical connection between the transformer's external connections and the most closely connected coils / windings in the form of a bushing fixed to the drain. The bushing is built to meet existing insulation requirements both on the outside and inside of the drawer. comprises coils / windings whose conductors are divided into a number of conductor elements, parts, which must be transposed in such a way that it. induced voltage, in each party becomes as equal as possible and so that the difference in induced voltage between each pair of parties becomes as small as possible. comprises an insulation system partly within a coil / winding and partly between coils / windings and other metal details which is designed as a solid cellulose- or lacquer-based insulation closest to the individual conductor element and outside of solid cellulose and liquid, possibly also gaseous, insulation. It is also extremely important that the insulation system has a very low moisture content. 10 l5 20 25 30 35 19 520 s9o - includes as an integral part an oil-surrounded winding coupler which is usually connected to the transformer's high-voltage winding for voltage control. - contains oil which can cause a non-negligible fire risk in connection with internal partial discharges, so-called glare, sparking 'in winding couplers and other fault conditions. - usually includes a monitoring device for loose gas in the oil that occurs during electrical discharges in it or during local temperature rises. - includes oil which in the event of damage or accident can result in oil spills causing extensive environmental damage.

SUMMARY OF THE INVENTION The object of the present invention is primarily to provide an electromagnetic device in which at least one or some of the above-discussed disadvantages associated with the prior art are known to provide a method of electric field control when eliminated. In addition, the invention relates to an electromagnetic device for electric power use and to a method for manufacturing a magnetic circuit for a rotating electric machine.

The primary object is achieved by means of a device of the type defined in the appended claims, and then most closely in claims 1-5.

In a broad sense, it is stated that the design according to the invention, by creating the possibility to contain mainly the electric field arising from said electrical conductor in the insulation system, reduces losses which occur so that consequently the device can operate with a 0 2 520 890 The reduction of losses gives in its somewhat higher efficiency. This leads to a lower temperature in the device, reduces the need for cooling and means that any existing cooling devices can be designed more easily than the absence of the invention.

The. The conductor / insulation system according to the invention can be realized as a flexible cable, which entails significant advantages in terms of manufacture and assembly compared to hitherto conventional rigid windings in prefabricated. It according to the invention. The insulation system used also means a lack of gaseous and liquid insulation media.

With regard to the invention in its form of a rotating electric machine, conditions are thus created for driving the power that the previously mentioned skin with such a voltage "step up" transformer can be excluded. The machine can thus be operated with significantly higher voltage than machines according to the state of the art for making a direct connection to the power grid. This entails significantly lower investment costs for systems with a rotating electric machine and the overall efficiency of the system can be increased. The invention eliminates the need for special field control measures at certain areas of the winding, which field control measures have been necessary according to the prior art. A further advantage is that the invention makes it easier to achieve under- and over-magnetization in order to reduce reactive effects that occur when voltage and current are out of phase with each other.

With regard to the aspect of the invention as a power transformer / reactor, the invention eliminates above all the need for oil filling of the power transformers and the consequent problems and disadvantages. The design of the winding so that along at least a part of its length it comprises an insulation formed of a solid insulating material, inside this insulation an inner layer and outside the insulation an outer layer with these layers of semiconducting electrical field in. the entire device within the winding. By material creates the possibility of containing the term "solid insulating material" used here, it is meant that the winding must lack liquid or gaseous insulation, for example in the form of oil. Instead, the insulation is intended to be formed of a polymeric material. The inner and outer layers are also formed of a polymeric material, however a semiconducting one.

The inner layer and the solid insulation are firmly connected to each other over substantially the entire interface. The outer layer and the solid insulation are also firmly connected to each other over substantially the entire interface therebetween. The inner layer functions as a potential equalizer and thus a equalizer with respect to the electric field outside the inner layer as a consequence of. its semiconducting properties. The outer layer is likewise intended to be formed of a semiconducting material and has at least an electrical conductivity which is higher than that of the insulation so that the outer layer by connection to earth or otherwise relatively low potential is able to function as a potential equalizer, and in mainly contain the electric field arising inside the outer layer due to said electric conductor. On the other hand, the outer layer should have a resistivity sufficient to minimize the electrical losses therein.

The solid connection between the insulating material and the inner and outer semiconducting layers must be so uniform over substantially the entire interface that no cavities, pores or the like occur. At the high voltage levels referred to in the invention, the electrical and thermal load that may occur will place extremely high demands on the insulation material. It is known that so-called partial discharges, PD, generally pose a serious problem for insulation materials in high-voltage installations. If cavities, pores or the like occur, internal corona discharges can occur at high electrical voltages, whereby the insulation material gradually breaks down and this can eventually lead to electrical penetration through the insulation. This can lead to serious breakdowns in the electromagnetic device. The insulation should thus be homogeneous.

The inner layer inside the insulation must have an electrical conductivity that is lower than that of the electrical conductor but sufficient for the inner layer to function and thus equalize in this case in the combination potential equalizing electric field outside the inner layer. tion with the fixed connection of the inner layer and the insulation over substantially the entire interface, i.e. the absence of cavities, etc., means a substantially uniform electric field outside the inner layer and a minimal risk of PD. It is preferred that the inner layer and the solid insulation consist of materials with substantially equal coefficients of thermal expansion. The same is preferred with respect to the outer layer and the solid insulation. This means that the inner and outer layers and the solid insulation will form an insulation system which, in the event of temperature changes, expands or contracts uniformly as a monolithic part without these temperature changes giving rise to any destruction or fragmentation in the interfaces.

Thus, intimacy in the contact surface between the inner and outer layers and the solid insulation is ensured and it is assumed that this intimacy »A + - n AA 1 å fi m-s att. unucf .tonga nings to operating periods. lO l5 20 25 30 35 23 520 390 The electrical load on the insulation system reduces sonx a consequence. in that the inner and outer layers of the insulating material consisting of * semiconductor material will tend to constitute substantially equipotential surfaces and that thereby the electric field in the insulation itself will be distributed relatively evenly over the thickness of the insulation.

It is known that high voltage cables for the transmission of electrical energy can be built up of conductors with an insulation of a solid insulation material with inner and outer layers of semiconducting material. When transferring electrical energy, it has long been established that the insulation must be free from defects. In the case of high-voltage cables for transmission, however, the electrical potential does not change along the length of the cable, but the potential is in principle at the same level. However, even with high-voltage cables for transmission use, instantaneous potential differences due to transient processes can occur, are used in the electromagnetic device as winding as in lightning strikes. According to the present invention, a flexible cable formed according to the appended claims.

One. further improvement can be achieved by: the electrical conductor. in the winding is built up. of rnindre so-called kardeler, By making these parties with relatively li- of 'at least some are isolated from each other. the cross-section, preferably approximately round, the magnetic field over the parties will have a constant geometry in relation to the field and the occurrence of eddy currents will thus be minimized.

According to the invention, the winding thus preferably consists of a cable comprising the electrical conductor and the previously described insulation system, wherein its layer extends around the parts of the conductor. Outside this inner semiconductor layer is the cable's main insulation 1 solid insulation material. 10 15 20 30 MJ (D 24 szn 890 According to the invention, the outer semiconductor layer must exhibit such electrical properties that a potential equalization along the conductor is ensured. However, the outer layer must not exhibit such conductive properties that a current will be conducted along the surface, which would give rise to losses For those (at 20 ° For the inner which in turn can cause undesired thermal load. inner and outer layers apply the resistance data C) defined in the following claims 8 and 9. the semiconducting layer must have sufficient electrical conductivity to ensure equipotential bonding of the electric field, but at the same time this layer must exhibit such resistivity that the confinement of the electric field is ensured.

It is important that the inner layer evens out irregularities in the conductor surface and forms an equipotential surface with a high surface finish at the interface with the solid insulation. The inner layer can be formed with varying thickness but to ensure a smooth. surface with. with respect to the conductor and the solid insulation, the thickness is suitably between 0.5 and 1 mm.

One such flexible winding cable which is used according to the present invention in its electromagnetic device is a further development of the PEX cable used per se for transmission purposes or a cable with EP rubber insulation. The further development includes, among other things, a new design both as far as the parts of the electrical conductor are concerned and also that the cable, at least in certain embodiments, is not intended to have an outer casing for mechanical protection of the cable. However, it is possible according to the invention that outside the outer semiconducting layer a conductive multi-shield and a outer jacket are arranged. The metal frame will FT obtain the character of external mechanical and electrical protection, for example against lightning strikes. It is preferred that the inner semiconductor layer 1010 25 25 35 35 520 890 will be on the potential of the electrical conductor. For this purpose, at least one of the strands of the electrical conductor is intended to be uninsulated and arranged so that good electrical contact is achieved with the inner semiconducting layer. alternately conductive with electrical contact with the inner semiconductor layer. windings of a flexible cable according to the above mean drastic Alternatively, different strands can be Manufacturing transformer or reactor differences in the electric field distribution between conventional power transformers / reactors and a power transformer / reactor according to the invention. The decisive advantage of a cable-shaped winding according to the invention is that the electric field is enclosed in the winding and that there is thus no electric field outside the outer semiconductor layer. The electric field provided by the live conductor appears only in the fixed Boat from the structural main insulation. and from a manufacturing point of view, it entails significant advantages: - The transformers' windings can be designed without having to take into account any electric field distribution and the transformation of parts mentioned under the state of the art is eliminated.

- The core design of the transformer can be designed without having to take into account any electric field distribution.

- No oil is needed for electrical insulation of the winding, ie the surrounding medium of the winding can be air.

- No special connections are required for electrical connection between the external connections of the transformer and the nearest connected coils / windings, as the electrical connection, unlike conventional systems, is integrated with the winding. lO} _. \ Ul 20 25 30 35 26 520 890 - The manufacturing and testing technology required for a. The power transformer according to the invention is substantially simpler than for a conventional power transformer / reactor since the impregnation, drying and vacuum treatments described below in the prior art are no longer required. This results in significantly shorter production times.

By using the technology according to the invention for insulation, considerable impossibilities are obtained in developing the magnetic part of the transformer, which was given in accordance with previous technology.

When applying the invention as a rotating electrical machine, a significantly reduced thermal stress occurs on the stator. Temporary overloads of the machine thus become less critical and it becomes possible to operate the machine in case of overload for a longer period of time without risking damage. This means great advantages for power plant owners soni in the event of disturbances today are quickly forced to switch to other equipment to ensure statutory delivery requirements.

With a rotating electric machine according to the invention, maintenance costs can be significantly reduced thanks to the fact that the transformer and switch do not have to be included in the system to connect the machine to the power grid.

It has already been described above whether the outer semiconducting layer of the winding cable is intended to be connected to earth potential. The intention is that the layer along the entire length of the winding cable should be kept at substantially ground potential.

It is possible to divide the outer semiconductor layer by cutting into a number of sections distributed along the length of the winding cable, whereby each individual layer section can be connected to the ground potential. for greater uniformity along the length of the winding cable.

It has been mentioned above how the solid insulation and the inner and outer layers can be achieved by, for example, extrusion. However, other techniques are also quite possible, for example the formation 'of' these interiors and. outer layer or the insulation by means of spraying of the material in question.

It is preferred that the winding cable be designed with a circular cross section. However, other cross-sections can also be used in cases where it is desired to obtain a better packing density.

To build up voltage in the rotating electrical machine, the winding cable is laid in several successive turns in the lock in the magnetic core. The winding can be designed as a multi-layered concentric cable winding to reduce the number of reversals. The cable can be made with stepped insulation to make better use of the magnetic core, whereby the design of the rafter can also be adapted to the stepped insulation of the winding.

A significant advantage in the application of the invention to a rotating electric machine is that the electric field is close to zero in the reversal region outside the outer semiconductor and that with earth potential on the outer semiconductor layer, the electric field does not need to be controlled. This means that no field concentrations can be obtained either within the core, in regions of return or in the transition between these.

The present invention also relates to a method for electric field control in an electromagnetic device for electric power use according to the following claim 40. 10 15 20 25 30 35 =.> -. 28 520. 890 Furthermore, the invention relates to a method for manufacturing a magnetic circuit according to the following claim 41, wherein a flexible cable is used as winding which is inserted into openings formed in grooves in a magnetic core of the rotating electrical machine. The flexibility of the cable means that a cable can be laid in several turns in one coil. will then consist of bending zones of the cables. also. spliced in such a way that its properties * remain * constant over the cable length. This procedure entails significant simplifications compared with the state of the art. The so-called rubble rods are not flexible but must be preformed to the desired shape. Insulating winding and impregnation of the coils are also extremely complicated and expensive techniques in the production of rotating electric machines of today.

In summary, it thus applies that an electromagnetic device in the form of a rotating electric machine according to the invention. entails a significant number of important advantages relative to corresponding machines according to the state of the art.

First, the machine according to the invention can be connected directly to a power grid at all types of high voltage. Another significant advantage is that earth potential has been consistently carried along at least part of and preferably along the entire winding, which means that the turning region can be made compact and that bracing devices in the turning region can be applied to, in the near future, earth potential. As already pointed out above with regard to power transformers / reactors, oil-based insulation and cooling systems also disappear with rotating electrical machines. This means that no sealing problems arise and that the previously mentioned dielectric ring is no longer needed. It is also important that all forced cooling can take place at ground potential. 10 15 20 25 30 35 29 520 890 Brief Description of the Drawings With reference to the accompanying drawings, a more detailed description of exemplary embodiments of the invention follows.

In the drawings: Fig. 1 is a partially cut-away view showing the parts included in the current modified standard cable, Fig. 2 an axial end view of a sector / pole division of a magnetic circuit according to the invention, Fig. 3 a view showing the electric field distribution around a winding of a conventional power transformer / reactor, Fig. 4 is a perspective view illustrating an embodiment of a power transformer according to the invention, Fig. 5 is a cross-sectional view illustrating a relatively modified cable structure with several electrical conductors, and Fig. 6 is a cross-section of a further cable structure comprising several electrical conductors but in a different device than that in Fig. 5.

DESCRIPTION OF PREFERRED EMBODIMENTS An important prerequisite for being able to manufacture a magnetic circuit in accordance with the invention is to use for the winding a conductor cable with solid electrical insulation, with an inner semiconducting layer between the insulation and one or more internal electrical conductors and with a outer half 10 20 20 25 30 35 30 520 890 Such cables are available as standard cables for other power-using conductive layers located outside the insulation. areas, namely power transmission. In order to be able to account for an embodiment, a brief description of a standard cable must initially be given. The internal live conductor consists of a number of strands. Around the strands there is a semiconducting inner layer or casing. Outside this semiconducting inner layer is an insulating layer of solid insulation. The solid insulation is formed from a polymeric material with low electrical losses and high breakdown strength. As concrete examples may be mentioned polyethylene (PE) and (PEX) (EP).

A semiconducting, then particularly crosslinked polyethylene and ethylene-propylene pine core1 and an outer insulating casing can be arranged around the outer semiconducting layer. The layers consist of a polymeric material, for example ethylene copolymer, with an electrically conductive component, for example conductive soot. Such a cable will be referred to below as a power cable.

A preferred embodiment of a cable intended as winding in the rotating electrical machine is shown in Figure 1. The cable 1 is shown in the figure as comprising a live conductor 2 which comprises transposed both uninsulated and insulated solid. These strands may be percussion strands. Electrically machined, insulated strands * are also conceivable. / transposed in a number of layers. Around the conductor there is an inner semiconducting layer 3 which in turn is surrounded by a homogeneous layer of a solid insulating material. The insulation 4 thus completely lacks insulation material of liquid and gas type. This layer 4 is surrounded by an outer semiconducting layer 5. The cable used as winding in the preferred embodiment may be provided with a metal shield and outer sheath but need not be so. In order to avoid induced currents and associated losses in the outer semiconductor layer 5, this is cut off, preferably in the end face alignment, ie in the transitions from plate package to tangle basket. The cut-off 10 20 25 30 31 520 890 is made so that the outer semiconducting layer 5 will be divided into several, electrically completely or partially separated parts distributed along the cable. part is then connected to earth whereby the outer semiconductor apart. Each cut-off layer 5 will be poured on or almost at earth potential throughout the cable length. This means that around the permanently insulated winding at the end faces, the touchable and, after a certain period of use, dirty surfaces only have negligible potentials to earth and that they also cause negligible electric fields.

In order to optimize a rotating electric machine, the design of the magnetic circuit with regard to the grooves and the teeth, respectively, is important. The grooves should be connected as close to the casing side casing as possible. It is also desirable that the teeth at each radial level are as wide as possible. This is important to minimize machine losses, magnetization needs, etc.

With access to a conductor for the winding such as the cable mentioned above, there are _large_ opportunities to_ be able to optimize the magnetic core from the mentioned points of view. In the following, reference is made to a magnetic circuit in the stator of the rotary electric machine. Figure 2 shows an embodiment of an axial end view of a sector / pole division 6 of a machine according to the invention.

Rotor with rotor pole is denoted by 7. The stator is in a conventional manner composed of a laminated core of electric plate successively composed of sector-shaped plates. From a radially outermost ridge portion 8 of the core, a number of teeth 9 extend radially towards the rotor. Between the teeth there is a corresponding number of grooves 10. The use of cables ll as above allows, among other things, that the depth of the grooves for high-voltage machines can be made greater than has been possible according to the state of the art. The groove has a stepped cross section towards the rotor as the need for cable insulation is lower for each winding layer towards the rotor. As can be seen from the figure, the groove consists essentially of a circular cross section 10 around each layer of the winding with narrower waist portions 13 in between. the layers. right referred to as a Such a track cross section can. with 'certain "bicycle chain tracks". In the exemplary embodiment shown in Figure 2, cables with three different dimensions are used for cable insulation, arranged in three sections 14, 15 and 16 dimensioned accordingly, ie in practice there will be a modified cycle chain groove. The figure also shows that the stator tooth 9 can be designed with a practically constant radial width along the entire depth of the groove.

In an alternative embodiment, the cable used as winding may be a conventional power cable such as the one mentioned above. by peeling off the metal shield and sheath of the cable in the appropriate manner. The outer semiconductor layer 5 is then grounded.

Within the scope of the invention, a large number of alternative embodiments are accommodated, depending on the available cable dimensions as far as insulation and the outer semiconductor layer etc. are concerned. Embodiments with such bicycle chain tracks can also be defined in addition to what is described here.

As mentioned above, the magnetic circuit may be located in the stator and / or rotor of the rotating electric machine. However, the design of the magnetic circuit will largely correspond to the above description, regardless of whether the magnetic circuit is located in the stator and / or the rotor.

A winding is preferably used as a winding which can be described as a multilayer concentric cable winding. such a winding means that the number of intersections at the hair ends has been minimized by placing all the twists within the same group radially outside each other. This also allows a simpler procedure in the manufacture and threading of the stator winding in the various grooves. Due to the fact that the cable used according to the invention is relatively easily bendable, the winding can be effected by a relatively simple threading operation, in which the flexible cable is inserted into the openings 12 present in the grooves 10.

Power transformer / reactor (Figs. 3 and 4) Figure 3 shows in a simplified and principled manner the electric field distribution around a winding of a conventional power transformer / reactor, where 17 is a winding and 18 a core and 19 indicates equipotential lines, ie lines where the electric field has same size. The lower part of the winding is assumed to be at ground potential.

The potential distribution determines the structure of the insulation system because you must have sufficient insulation both between adjacent turns of the winding and between each turn and earth. The figure thus shows that the upper part of the winding is exposed to the highest insulation technical loads. The design and location of a winding relative to the core is determined in this way mainly by the electric field distribution in the core window.

The cable which can be used in the windings included in dry power transformers / reactors according to the invention has been described with reference to Fig. 1. The cable can, as mentioned earlier, be provided with other special outer layers intended for special purposes, for example to prevent excessive electrical stresses in other areas of the transformer / reactor. From a geometric dimensional point of view, the cables in question will generally have a conductor area of between 2 and 3000 mm2 and an outer cable diameter of between 20 and 250 mm.

Windings of a power transformer / reactor made of it. The cable 1015 20 25 30 35 34 520 890 reported during the description of the invention can be used in both single-phase, three-phase and multi-phase transformers / reactors, regardless of how the core is designed. An embodiment is shown in Figure 4 which shows a three-phase laminated nuclear transformer. The core consists in a conventional manner of three core legs 20, 21 and 22 and the cohesive yokes 23 and 24. both the core legs and the yoke stepped cross-sections.

In the embodiment shown, the windings formed with cable are located around the core legs. The embodiment shown in Figure 4 has as 26 and 27.

The innermost winding turn 25 can represent the primary winding, there are three concentric winding turns 25, the winding and the other two winding turns 26 and 27 can represent the secondary winding. In order not to burden the figure with too many details, the connections of the windings are not shown. The figure in general shows that in the embodiment shown, there are spacer rails 28 and 29 with several different functions in certain places around the windings. The spacer rails can be designed of insulating materials intended to provide a certain space between the concentric winding turns for cooling, bracing, etc. They can also be made of electrically conductive material to be part of the earthing system of the windings.

Alternative cable designs In the cable variant illustrated in Fig. 5, the same reference numerals are used as before, only with the addition of the embodiment characteristic letter a. In this embodiment, the cable comprises several electrical conductors 2a, which are mutually separated by means of the insulation 4a. Expressed in other words, the insulation 4a serves both for insulation between individual adjacent electrical conductors 2a and between these and the environment. The different electrical conductors 2a can be laid in different ways, which causes varying cross-sectional shape of the cable as a whole. In the example according to Fig. 10, 1020 25 30 35 35 520 890 is illustrated as if the conductors 2a are laid on a straight line, something which gives rise to a relatively flat cross-sectional shape of the cable. From this it can be concluded that the cross-sectional shape of the cable can vary within wide limits.

In Fig. 5, a voltage which is less than a phase voltage is assumed to exist between adjacent electrical conductors. More specifically, the electrical conductors 2a in Fig. 5 are thought to be formed by different turns in the winding itself, which means that the voltage between these adjacent conductors is relatively moderate.

Seasonally, a semiconducting outer layer 5a is present outside the insulation 4a provided by a solid insulating material. An inner layer 3a of a semiconducting material is arranged around each of said electrical conductors 2a, i.e. each of them has its own surrounding inner semiconducting layer 3a. function equalizing as far as the individual This layer 3a will thus be the electrical conductor.

The variant in Fig. 6 uses the same reference numerals as before only with the addition of the design-specific letter b. Here, too, there are several, more precisely 3, electrical conductors 2b. Between these, in the example, phase voltage is thought to exist, ie a substantially higher voltage than that present between conductors 2a in the embodiment according to Fig. 5. In Fig. 6 there is an inner semiconducting layer 3b, inside which the electrical conductors 2b are arranged. However, each of the electrical conductors 2b is enclosed by its own additional layer 30 with properties corresponding to the properties of the inner layer 3b discussed above. Insulation material is present between each additional layer 30 and the layer 3b arranged around them. Consequently, the layer 3b will be present as a potential equalizing layer outside the electrical conductors' own additional layers 30 of semiconducting material, these additional layers 30 being adjacent to the respective electrical conductors 2b to be placed on equal potential. like this.

POSSIBLE MODIFICATIONS It is a given that the invention is not only limited to the embodiments described above. Thus, those skilled in the art will recognize that a variety of detailed modifications are possible once knowledge of the basic inventive concept is obtained without having to. should deviate from the inventive concept as defined in the appended claims. By way of example, it is pointed out that the invention is not exemplified limited to the specific material choices as above. Functionally equivalent materials can thus be used instead. With regard to the manufacture of the insulation system according to the invention, it is pointed out that techniques other than extrusion and spraying are also possible as long as intimacy between the different layers is achieved. It is further pointed out that more equipotential layers could be arranged. For example, one or more equipotential layers of semiconductor material could be placed in the insulation between those referred to above as "inner" and "outer".

Claims (37)

10 15 20 25 30 35 37 520 890 Patent claims Electromagnetic device, comprising an electrical circuit for generating or by means of a magnetic field including at least one electrical conductor (2) with an insulation system, characterized in that the insulation system comprises an insulation (4) formed by a fixed insulation (5). ), has an electrical conductivity that is higher than that of iso-materials and outside the insulation an outer layer such as the lation. in order for the outer layer genonx connection to earth or otherwise relatively low potential to be able to function as a potential equalizer, partly to contain it mainly due to said electrical conductor (2) arising (5), that comprises a single electrical conductor the field inside the outer layer the insulation system inside the insulation (4) (3), (2) is arranged inside the inner layer (3) inner layer that said at least one electrical conductor and that the inner layer has an electrical conductivity which is lower than that of the electrical conductor but sufficient for the inner layer to function. equalization and. thereby equalizing the electric field outside the inner layer (3). Electromagnetic device comprising at least one electrical conductor (2) with an insulation system, characterized in that the insulation system comprises at least two potential layers (3, 5) and between them an electrical insulation (4) of a solid insulating material, and that the potential layers and the solid insulation has substantially the same thermal properties. Device according to claim 1 or 2, characterized in that said at least one conductor (2) constitutes at least one induction coil. 10 15 20 25 30 35 38 520 890 Device according to one of the preceding claims, characterized in that the inner and / or outer layer (3, 5) comprises a semiconducting material. Device according to any one of the preceding claims, characterized in that the inner layer (3) and / or the outer layer (5) has a resistivity in the range 10 '5 Qcm - 100 kQcm, suitably 10 * 3-1000 (kmr preferably 1 -500 Qcm. Device according to any one of the preceding claims, the inner layer claim, characterized (3) and / or the outer layer (5) having a resistance which in the length meter of the layer is in the range 50 pQ - 5 MQ. hence, Device according to one of the preceding claims, characterized in that the solid insulation (4) and the inner layer (3) and / or the outer layer (5) consist of polymeric material. Device according to any one of the preceding claims, that the inner layer (3) claims, characterized and / or the outer layer (5) and the solid insulation (4) are firmly connected to each other, others over substantially the entire interface. Device according to any one of the preceding claims, the inner layer (3) being claimed, and / or the outer layer (5) and the solid insulation (4) being made of materials with substantially equal coefficients of thermal expansion. Device according to one of the preceding claims, characterized in that the solid insulation (4) is produced by extrusion. 11. ll. Device according to claim 10, characterized in that the inner layer (3) and / or the outer layer (5) are provided by extrusion simultaneously with the extrusion of the solid insulation (4). Device according to one of the preceding claims, in that the conductor (2) and its insulation system form a winding formed by means of a flexible cable (1). characterized therefrom, Device according to claim 12, characterized in that the area of said at least one electrical conductor of the cable is in the range 2-3000 mm 2 while the outer diameter of the cable is between 20 and 250 mm. Device according to any one of the preceding claims, characterized in that the inner layer (3) and / or the outer layer (5) comprises a polymeric material containing an electrically conductive component. hence, Device according to any one of the preceding claims, that the inner layer (3) comprises the at least one electrical conductor (2). characterized thereby, is in electrical contact with Device according to claim 15, characterized in that said at least one electrical conductor (2) comprises a number of strands and that at least one strut of the electrical conductor. (2) is at least partially uninsulated and arranged in electrical contact with the inner layer (3). Device according to an earlier (3b) electrical conductor (2b) isolated from each other. requirements, characterized in that several are arranged inside the inner layer Device according to claim 17, (3a) around each of said plurality of electrical conductors. characterized in that an inner layer according to any preceding claim 'is' arranged 10 15 20 25 30 35 40 520 890 Device according to claim 17, characterized in that within the inner layer (3b) (2b) there are further layers around each of said several conductors (30) with properties corresponding to the inner layer. Device according to one of the preceding claims, characterized in that the outer layer (5) is divided into a number of parts, low potential. Device according to any one of the preceding claims, characterized in that it constitutes a rotating electric machine. Machine according to Claim 21, characterized in that its electric circuit for generating an average magnetic field is arranged in the stator and / or rotor of the machine. Machine according to one of Claims 21 to 22, characterized in that the magnetic field generation circuit comprises one or more magnetic cores (8) (10) with grooves for the winding (1). Machine according to claims 21-23, the outer layer (5) characterized in that with connected to ground potential * the electric field of the machine outside the outer layer is close to 0 both in the grooves (10) and in the reversal region. Machine according to any one of claims 21-24, characterized in that (10) separated by a narrower waist portion to the grooves (12) the cylindrical openings. are shaped as a number of cylindrical openings (13) between Machine according to Claim 25, characterized in that the cross-section (10) (8) of the magnetic core is calculated. the density of the grooves openings decreases from a back portion which are individually connected to ground or otherwise. 10 15 20 25 30 35 l 4 520 890 Machine according to Claim 26, characterized in that the cross section of the latch (10) decreases continuously or discontinuously. Machine according to one of Claims 21 to 27, characterized in that it consists of a generator, motor or synchronous compensator. 29. A machine according to claim 28, characterized in that the generator is of the type hydrogen generator or turbo generator. Device according to one of Claims 1 to 20, characterized in that it consists of a power transformer / reactor. Power transformer / reactor according to Claim 30, characterized in that it has a magnetic core. Power transformer / reactor according to Claim 30 or 31, characterized in that it is air-wound and thus has no magnetic core. A power transformer / reactor according to any one of claims 30-32, comprising at least two galvanically separated windings, characterized in that the windings (25-27) are concentrically wound. 34. A high-voltage electric power plant or electric power grid comprising one or more electromagnetic devices according to any one of claims 1-33. A method for electric field control in an electromagnetic device for electric power use comprising a circuit for generating or by means of a magnetic field having at least one winding (1) with at least one electric conductor (2) and an outer portion thereof (4), formed of a solid insulating material and that the present insulation is characterized in that the insulation (4) 10 15 20 25 30 q -Uu 4 2 520 890 outside the insulation is arranged an outer layer (5), closes to earth or otherwise relatively low potential and which has an electrical conductivity which is higher than that of the insulation (4) but lower than that of the electrical conductor (2) in order to function as a potential equalizer and to cause the electric field inside the outer layer (5) to be substantially enclosed in the winding and that an inner layer is arranged inside the solid insulation (4), that said at least is arranged inside the inner and that this inner layer (3) has conductivity which is lower than the conductivity of the electron one electricity The conductor (2) layer (3) has an electric conductor but sufficient to cause the inner layer to function smoothly with respect to the electric field outside the inner layer (3). 36. A method of manufacturing a magnetic circuit for a rotating electric machine, wherein the riveting circuit is arranged therein. rotating electric. the stator and / or rotor (10) of the machine, the grooves being formed with openings and comprising a magnetic core (8) for one (12), such as winding using a flexible with groove winding, characterized therefrom, high voltage cable (1) (12). and that this high voltage cable is inserted into the openings Use of a cable comprising at least one electrical conductor (2) with an insulation system comprising at least two potential layers and between them an insulation of a solid electrical insulation material, where the potential layers and the solid insulation have substantially equal thermal properties, for formation of a winding for generating or by magnetic field in an electromagnetic device.