SE510925C2 - Electromagnetic device - Google Patents

Abstract

An electromagnetic device comprises at least one magnetic circuit (1) and at least one electric circuit (2, 3) comprising at least one winding (4, 5). The magnetic and electric circuits are inductively coupled to each other. The device comprises a control arrangement (7) to control operation of the device. This control arrangement is adapted to control frequency, amplitude and/or phase as concerns electric power to/from the device by the control arrangement comprising means (9) controlling the magnetic flux in the magnetic circuit.

Description

35 510 925 2 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 prior art with regard to the second aspect mainly relates to power transformers, the invention is also intended to be applicable to reactors, both single-phase and three-phase. In the case of insulation and cooling, there are in principle the same embodiments as for transformers. There are thus air-insulated and oil-insulated, self-cooled, pressure-oil-cooled, etc. reactors. Although reactors have a winding (per phase) and can be designed both with and without a magnetic core, the description of the state of the art is largely relevant for reactors as well.

The at least one winding of the electrical circuit may in some embodiments be air wound but usually comprises a magnetic core of laminated, normal or oriented, sheet or other, for example amorphous or powder based, material or other measure intended 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 may be located in the stator or rotor of the machine or in both.

A problem with known embodiments of electromagnetic devices of the type discussed above is that it is either relatively difficult to achieve effective control within a certain range of parameters or that the control devices tend to be relatively expensive. It is pointed out in this context that it is known in generator technology to exercise control of functional parameters via the field winding. If the rotor includes electromagnets, this field winding is formed on the rotor with the disadvantages this entails in the form of a more expensive and more difficult-to-control design. In the case of a permanent magnet rotor, the problem arises that field control does not become practically feasible. This, of course, complicates regulation in general and in particularly delicate regulatory situations in particular. A further problem with the prior art is that the conventional winding technique makes it expensive to manufacture the windings. The known embodiments also cause significant energy losses and 3A sin 925 imposes limitations on the location of the windings at the magnetic circuit.

SUMMARY OF THE INVENTION The object of the present invention is to provide ways to simplify and improve the possibilities of regulating the function of electromagnetic devices according to the preamble of the following claim 1, and better conditions for rational winding production and assembly are to be created.

The basic object of the present invention is fulfilled in that the control device is arranged to regulate frequency, amplitude and / or phase with respect to electrical energy to / from the device in that the control device comprises means for regulating the magnetic flux in the magnetic circuit.

Accordingly, the present invention is based on the idea of directly influencing the magnetic flux in the magnetic circuit in the desired direction by flow control in order thereby to be able to regulate the function of the device. This results in a very rational and cost-effective design, and offers increased opportunities for regulation in order to achieve optimized operation.

According to a particularly preferred embodiment of the invention, the control means comprises at least one control winding inductively connected to the magnetic circuit. Consequently, via the control winding, the control device is capable of effecting the required regulation of the magnetic flux in the magnetic circuit by applying such control parameters via the control winding that the magnetic flux flowing in the magnetic circuit is affected to the required extent. The control winding could even be short-circuited. The magnetic flux can then in some embodiments not pass the control winding. Depending on the design of the magnetic circuit, partial or total blockage of the magnetic flux may occur.

Examples of control functions that can be achieved with the invention according to the invention are * voltage change and stabilization, elimination of transients, attenuation of oscillations in the power network, filtering out harmonics, frequency adjustments and phase adjustments (including separate control for the phases are taken care of). It is pointed out here that the control device according to the invention can be arranged to add to the magnetic flux in the magnetic circuit a magnetic additional flux, i.e. that the control device could function for direct energy supply.

The control according to the invention of the magnetic flux in the magnetic circuit means in the case of a transformer, for example, that good control can be exercised over the secondary winding voltage so that it meets the set requirements despite difficult fluctuations in the primary voltage or the load connected to the secondary winding.

Further details and advantages of the flow control according to the invention in the magnetic circuit will appear from the following detailed description.

It is also within the scope of the invention that at least one of the windings of the electromagnetic device or at least a part of this winding comprises at least one flexible electrical conductor with a housing which is magnetically permeable but capable of substantially enclosing the electric field arising around the conductor. Expressed in other words, this means that the flexible electrical conductor and its housing (in the form of an insulation system) are formed by means of a flexible cable. This entails significant advantages in terms of manufacture and assembly compared to hitherto conventional rigid windings in prefabricated form. The insulation system used according to the invention also means a lack of gaseous and liquid insulation media.

In the invention, by substantially enclosing the electric field arising around the electric conductor in the cable in the insulation system, the invention reduces losses which occur so that the device can consequently function with a higher efficiency. The reduction of the losses in turn gives rise to a lower temperature in the device, which reduces the need for cooling and means that any existing cooling devices can be designed more easily than in the absence of this aspect of the invention. 10 15 20 25 30 35 5 510 925 With regard to the invention in its form of a rotating electric machine, conditions are thus created for operating the machine with such a high voltage that conventional "step-up" transformers 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 an electric power grid. This entails significantly lower investment costs for systems with a rotating electrical 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 prior art. A further advantage is that the invention makes it easier to achieve under- and over-magnetization for the purpose of reducing reactive effects occurring 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 it comprises along at least a part of its length 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 material creates the possibility to contain the electric field in the entire device within the winding. The term "solid insulating material" as used herein means that the winding should 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 between them. The inner layer functions as a potential equalizer and thus 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 10 15 20 25 30 35 510 925 6 which is higher than that of the insulation so that the outer layer by connection to earth or otherwise relatively low potential is partly to function as a potential equalizer, and partly to 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 which may arise will place extremely high demands on the insulating 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 insulating 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 electric conductivity that is lower than that of the electrical conductor but sufficient for the inner layer to function as a potential equalizer and thus to provide the electric field outside the inner layer. This in combination 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 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 of interfaces. Thus, intimate adhesion in the contact surface between the inner and outer layers and the solid insulation and conditions for maintaining this adhesion for long operating periods are ensured. the adhesion shall be of such a nature that the adhesion between at least that of the inner layer and the solid insulation and preferably also the outer layer and the solid insulation is also ensured at the bends to which the electrical line and the insulation system will be subjected. It is pointed out here that in order to be able to perform the threading of the winding, the cable should be flexible in a radius of curvature which is less than 25 times the cable diameter, preferably less than 15 times the cable diameter. Most preferably, the cable is flexible down to a radius of curvature less than or substantially equal to 8 times the cable diameter.

It is essential that the insulation system consists of materials with good elasticity. The E-modulus of the materials should be relatively low, ie the deformation resistance of the materials should be relatively low. In order to avoid that adventurous shear stresses arise in the boundary zone between different layers included in the insulation system, it is preferred that the elasticity (E-modulus) of the layers included in the insulation system is substantially equal.

The electric load on the insulation system decreases as a result of the fact that the inner and outer layers of the semiconductor material around the insulation will tend to constitute substantially equipotential surfaces and that 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 of 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 can occur due to transient processes, such as during lightning strikes. According to the present invention, in the electromagnetic device, a flexible cable formed according to the following claims is used as winding.

A further improvement can be achieved in that the electrical conductor in the winding is built up of smaller so-called card parts, at least some of which are insulated from each other. By making these parts with a relatively small cross section, preferably approximately round, the magnetic field over the parties will show a constant geometry in relation to the field and the occurrence of eddy currents is thereby 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 inner layer extends around the parts of the conductor. Outside this inner semiconductor layer is the cable's main insulation in the form of a solid insulating material.

According to the invention, the outer semiconductor layer must have 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 which in turn can cause undesired thermal load. For the inner and outer layers, the resistance data (at 20 ° C) defined in the following claims 22 and 23 apply. For the inner semiconductor layer, it must have sufficient electrical conductivity to ensure equipotential bonding for 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 surface of the conductor 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 in order to ensure a smooth surface with respect to the conductor and the solid insulation, the thickness is suitably between 0.5 and 1 mm. 10 15 20 25 30 35 9 510 925 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 designs, is not intended to have any outer casing for mechanical protection of the cable. However, it is possible according to the invention that a conductive metal shield and an outer sheath are arranged outside the outer semiconducting layer. The metal screen will thereby acquire the character of external mechanical and electrical protection, for example against lightning strikes. It is preferred that the inner semiconductor layer be at 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. Alternatively, different strands may be alternately conductive with electrical contact with the inner semiconductor layer. Manufacturing transformer or reactor windings from a flexible cable as above involves drastic differences in the electric field distribution between conventional power transformers / reactors and a power transformer / reactor according to the invention. The crucial 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 main insulation. From both a design and manufacturing point of view, this means significant advantages: - The transformer 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 construction of the transformer can be designed without having to take into account any electric field distribution. 10 15 20 25 30 35 51Û 925 10 - 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 transformer's external connections and the nearest connected coils / windings, as the electrical connection, unlike conventional systems, is integrated with the winding.

The manufacturing and testing technology required for a power transformer according to the invention is significantly simpler than for a conventional power transformer / reactor, since the impregnation, drying and vacuum treatments described in the prior art are no longer necessary.

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 benefits for power plant owners who, in the event of disruptions 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 due 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 then that the layer along the entire length of the winding cable should be poured on substantially earth 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 directly to earth potential. This creates the conditions for greater uniformity along the length of the winding cable. 10 15 20 25 30 35 11 510 925 It has been mentioned above how the solid insulation and the inner and outer layers can be produced by, for example, extrusion.

However, other techniques are also well possible, for example the formation of these inner and outer layers and 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 grooves 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 grooves can also be adapted to the stepped insulation of the winding.

A significant advantage in the application of the invention in 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 origin or in the transition between them.

In a method of manufacturing a device according to the invention, 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 length of cable can be laid in several turns in a tangle. The inverters will then consist of bending zones in the cables. The cable can also be spliced in such a way that its properties remain constant over the cable length. This method involves significant simplifications compared to the prior art. The so-called rubble rods are not flexible but must be preformed to the desired shape. Soler winding and impregnation of the coils are also extremely complicated and expensive techniques in the manufacture of rotating electrical machines of today. 10 15 20 25 30 35 510 925 12 In summary, an electromagnetic device in the form of a rotating electric machine according to the invention thus entails a significant number of important advantages relative to corresponding machines according to the prior art. First, the machine according to the invention can be connected directly to a power grid for 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.

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 schematic view illustrating a device according to the invention in the form of a transformer, Fig. 2 a schematic view of a transformer variant, Fig. 3 a schematic view of a further transformer variant, Fig. 4 a view of an embodiment similar to that of Fig. 3. but with respect to a reactor, Fig. 5 is a schematic view illustrating a generator embodiment, Fig. 6 is a partially cut-away view showing the parts included in the current modified standard cable, Fig. 7 is an axial end view of a sector / pole division of a magnetic circuit according to the invention, Fig. 8 is a view showing the electric field distribution around a winding of a conventional power transformer / reactor, Fig. 9 is a perspective view illustrating an embodiment of a power transformer according to the invention, Fig. 10 is a cross-sectional view illustrating a relatively Fig. 1 modified cable structure with several electrical conductors, and Fig. 11 a cross-section of a further cable structure comprising several electrical l but in a different device than that in Fig. 6.

DESCRIPTION OF PREFERRED EMBODIMENTS The electromagnetic device illustrated in Fig. 1 is in the form of a transformer. This has a magnetic circuit 1 and two electrical circuits 2, 3 each comprising at least one coil-shaped winding 4 and 5, respectively.

The example illustrates how the transformer has a core 6 of a magnetic material. The core suitably consists of a package of magnetic disks to reduce eddy current losses. It is pointed out, however, that it is not a precondition for the application of the invention that a core really exists. Air-wound designs etc. are thus well possible within the scope of the inventive idea. It follows that the term magnetic circuit must be interpreted in a broad sense. The term in question thus means no more than that magnetic fields generated by existing windings 4, 5 must be capable of generating a magnetic flux.

The device according to the invention comprises a device generally denoted by 7 for regulating the function of the transformer.

This control device 7 is arranged to control frequency, amplitude and / or phase with respect to electrical power leaving the transformer. In the example, the electrical circuit 2 forms the primary side of the transformer while the electrical circuit 3 constitutes the secondary side of the transformer.

Power from the device thus exits via the secondary circuit 3, to which a load schematically indicated by 8 is connected. This load can be of any kind, for example pure consumers but also distribution and transmission networks.

The control device 7 comprises means 9 for regulating the magnetic flux in the magnetic circuit 1. The control means 9 includes in the example at least one control winding inductively connected to the magnetic circuit 1. In the example, this control winding 9 is wound around a portion of the core 6. In a coreless transformer design, the control winding 9 must be coordinated with the primary and secondary windings 4 and 5, respectively, so that the magnetic flux induced in the coreless magnetic circuit is inductively connected to the control winding 9.

According to a preferred embodiment of the invention, the control device 7 is intended to be of active type, i.e. the control device 7 should be arranged to actively control via the control winding 9 so that the magnetic flux in the magnetic circuit 1 acquires the desired character. It is then preferred that the control device 7 includes an external power source so that the control device 7 shall be capable of regulating the magnetic flux through the magnetic circuit 1 by causing a current to flow through the winding 9. The invention is particularly advantageous in connection with high voltage applications. Consequently, this means that relatively high voltage is normally intended to be associated with the electrical circuits 2 and 3. For control purposes, however, it is sufficient in such a case that the control device 7 causes a relatively high current to flow in the winding 9 with a relatively low voltage. For control purposes, the control device 7 can then be arranged to add a magnetic additional current to the magnetic flux in the magnetic circuit 1. This additional flow will be added to the otherwise occurring flow and by appropriate control of this additional flow the desired parameters with respect to the power output via the secondary circuit 3 can be achieved. As a basis for its control function, the device 7 can be arranged to receive from a voltage measuring device 10 a voltage information regarding the voltage in the secondary circuit and / or over the load 8. A current 10 15 20 25 30 35 15 510 925 measuring means 11 serves for current measurement in the secondary circuit 3.

The additional flow generated via the control device 7 can, as previously mentioned, be used to regulate frequency, amplitude and / or phase with respect to the power output via the secondary circuit 3.

It is pointed out that the control device 7 can be arranged to receive external control instructions via an input 12.

It is further pointed out that the control device 7 can be arranged to effect a passive control via the control winding 9. By means of passive control in this respect is meant that power from any external source is not used for the control. In this context it is pointed out that the control device 7 may be capable of connecting one or more passive elements over the control winding 9, such as resistors, capacitances or inductors connected in series or in parallel.

Such passive elements connected to the control winding 9 in a purpose-adapted manner thus enable different effects on the magnetic flux, which effects in turn result in consequences in terms of frequency, amplitude and / or phase in terms of the electrical power from the device.

Fig. 1 also shows whether the device on the primary side has a voltage measuring device 13 and a current measuring device 14 similar to what occurs on the secondary side.

Fig. 2 illustrates a transformer embodiment which differs from that merely described in Fig. 1 in that the magnetic circuit 1 here comprises a core 6 which comprises a further leg 16 in addition to that present in Fig. 1 on the secondary side, with 15 designated and that which occurs on the primary side and with 17 denoted. This thus means that the core 6 according to Fig. 2 will form two different flow paths schematically indicated by 18 and 19, respectively. The control winding 9a is arranged here around the central leg 16, i.e. at the flow path 18, which of course undergoes the transformer primary winding 4. The second flow path 19, on the other hand, passes by the control winding 9a via the secondary winding 5.

Via the control device 7, it is now possible to influence the magnetic flux in the leg 16 by means of the control winding 9a, which in turn will affect the magnetic flux in the leg 15 through the secondary side winding 5. Expressed in other words is thus the control winding 9a here is only associated with one of the two flow paths.

The variant in Fig. 3 involves the addition of an additional control winding 9b2 to the already existing 9b1. These two control windings are arranged around each of the legs 16b, 15b, i.e. these control windings 9b1 and 9b2 will each belong to the flow paths 18, 19. The control device 7b here comprises a control unit 20, which in turn controls control elements 21 and 22, respectively, coordinated with the control windings 9b1 and 9b2, respectively. By actively or passively controlling the control elements 21, 22 via the control unit 20, adjustment can be made so that the magnetic flux either passes through only one of the flow paths 18, 19 or is divided thereon.

In connection with Fig. 3 it may also be mentioned that the secondary winding 4b of the transformer comprises at least two series-connected winding parts 23 and 24, respectively. The main winding part 23 is flowed through by the magnetic flux in both flow paths 18, 19 while the winding part 24 is only flowed through by the flow thus means that when by means of the control windings 9b1 and 9b2 the magnetic flux is allowed to pass only through the leg 16b no magnetic flux passes through the winding part 24. This thus means a lower output voltage than that which applies to the operating case when the magnetic flux passes completely through the flow path 19 than when then both secondary winding parts 23 and 24 are traversed by the total magnetic flux. Accordingly, in such an operating case, the control winding 9b1 is intended to have broken the magnetic flux through the leg 16b completely or at least partially.

Fig. 4 illustrates a reactor design somewhat reminiscent of the transformer according to Fig. 3. The difference is that the reactor has no secondary side so that instead its power winding is divided into two winding parts 25, 26. As in the previous embodiment, there are two control windings 9c1 and 9c2. , by means of which the magnetic flux can be controlled so that it passes through the winding part 26 to the desired degree. The entire flux always passes through the winding part 25. Fig. 5 illustrates a particularly simplified generator design, the rotor of which is designated 26. This is thought in the example to be a permanent magnet rotor. However, it would also be possible to design the rotor with field windings. The magnetic circuit 1d here has an output electrical circuit 5d inductively connected to the magnetic flux in the core 6d. The core 6d has portions located adjacent to the rotor 26 so that during the rotation of the rotor the permanent magnets will generate a magnetic flux in the core. This flow passes through the outgoing winding 5d and generates in it an outgoing effect. The control device 7d comprises, as before, a control winding 9d inductively connected to the magnetic circuit 1d. Measuring devices 10d and 11d, respectively, for voltage and current are also present here for monitoring the output power. With the aid of the control device 7d, the control winding 9d can now be subjected to the required functionality for the control purpose, passively or actively in order to provide the output power from the generator desired properties with respect to frequency, amplitude and / or phase.

It is emphasized that in the figures extremely simplified embodiments are presented, and this in particular with only one phase. In reality, the designs can be significantly more complicated, especially multi-phase. The number of windings and winding parts can be significantly greater than that reported not only in terms of primary and secondary windings but also in terms of the number of control windings. The magnetic circuits can also have varying designs depending on functional requirements.

It is pointed out in particular that the fact that according to the invention at least one of the existing windings comprises an electric conductor surrounded by two mutually separated equipotential layers and a fixed insulation arranged between them means that the electric field around the conductor will be substantially enclosed in the cable. and secondary windings with very great freedom can be placed anywhere on the magnetic circuit. Even mixing of the windings is possible. It is also pointed out in this context that the control device is applicable to transformers of both the core and shell type. 10 15 20 25 30 35 510 925 18 l especially in high voltage applications, the design of the winding just described is suitable. It is pointed out here that normally the control winding / control windings 9 will be at lower potential than the power windings, so the control winding / control windings do not necessarily have to be designed with such an insulation system as at least one of the power windings.

An important aspect in order to be able to reach an electromagnetic device in accordance with the invention is to use at least one of the windings, apart from the control winding (s), a conductor cable with solid electrical insulation, with an inner semiconducting layer between the insulation and one or more internal electrical conductors and with an outer semiconductor layer located outside the insulation. Such cables are available as standard cables for other power engineering applications, 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 current 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 of a polymeric material with low electrical losses and high breakdown strength. As concrete examples may be mentioned polyethylene (PE) and then especially crosslinked polyethylene (PEX) and ethylene propylene (EP). A metal shield and an outer insulating casing can be arranged around the outer semiconducting layer. The semiconducting 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 a rotating electrical machine is shown in Figure 6. The cable 41 is shown in the figure as comprising a live conductor 42 which comprises transposed both uninsulated and insulated strands.

Electrically machined, firmly insulated strands are also conceivable. These strands can be beaten / transposed in a number of layers. Around the conductor is an inner semiconducting layer 43 which in turn is surrounded by a homogeneous layer of a solid insulating material. Thus, in the insulation 44, the insulation 44 is completely devoid of liquid and gas type insulation material. This layer 44 is surrounded by an outer semiconductor layer 45. 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 45, this is cut off, preferably in the end face alignment, ie in the transitions from sheet metal package to tangle basket. The cut-off is made so that the outer semiconductor layer 45 will be divided into several parts distributed along the cable, electrically completely or partially separated from each other.

Each cut-off portion is then connected to ground whereby the outer semiconductor layer 35 will be held at or almost at ground 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 electrical 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 be 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 great 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 7 shows an embodiment of an axial end view of a sector / pole division 46 of a machine according to the invention. Rotor with rotor pole is denoted by 47. 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 back portion 48 of the core, a number of teeth 49 extend radially toward the rotor. Between the teeth there is a corresponding number of grooves 50. The use of cables 51 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. 10 15 20 25 30 35 510 925 20 The groove has a cross-section stepped 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 52 around each layer of the winding with narrower waist portions 53 between the layers. Such a track cross-section can with some right be referred to as a "bicycle chain track". Since such a high voltage machine will require a relatively large number of layers and the availability of current cable dimensions in terms of insulation and outer semiconductors is limited, it can in practice be difficult to achieve a desired continuous phasing of cable insulation and stator groove respectively. In the exemplary embodiment shown in Figure 7, cables with three different dimensions of cable insulation are used, arranged in three devices 54, 55 and 56 dimensioned accordingly, ie in practice there will be a modified cycle chain groove. The figure also shows that the stator tooth 49 can be designed with a practically constant radial width along the entire depth of the groove.

It is again pointed out that the winding sections denoted in Fig. 7 by 54, 55 and 56 correspond to the winding denoted by Fig. 5 by 5d. In Fig. 7, on the other hand, one or more windings corresponding to the control winding 9 in Fig. 5 are denoted by the reference 40. In the example, these control windings 40 are located furthest radially out from the rotor. It is pointed out that it is not necessary for the control winding 9 to be located in the place indicated by 40 in Fig. 7. In an alternative embodiment, the cable used as winding may be a conventional power cable such as the one discussed above.

The grounding of the outer semiconducting layer 45 then takes place by peeling off the metal shield and sheath of the cable in suitable places. within the scope of the invention, a large number of alternative embodiments can be accommodated, depending on the available cable dimensions in terms of insulation and the outer semiconductor layer, etc. Embodiments with so-called bicycle chain tracks can also be modified in addition to what is described here. 10 15 20 25 30 35 21 510 925 As discussed 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 broadly correspond to the above description regardless of whether the magnetic circuit is in the stator and / or the rotor.

As winding, a winding which can be described as a multilayer concentric cable winding is preferably used. Such a winding means that the number of intersections at the end turns has been minimized by all the turns within the same group being placed radially outside each other. This also allows a simpler procedure in the manufacture and threading of the stator winding in the various grooves.

Because the cable used according to the invention is relatively easily flexible, the winding can be achieved by a relatively simple threading operation, in which the flexible cable is inserted into the openings 52 located in the grooves 50. Figure 8 shows in simplified form and in principle the electric field distribution around a winding of a conventional power transformer / reactor, where 57 is a winding and 58 a core and 59 indicates equipotential lines, i.e. lines where the electric field is the 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 was 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. previously, 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 geometrical 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 dry power transformer / reactor manufactured by the cable reported during the description of the invention can be used in both single-phase, three-phase and multiphase transformers / reactors, regardless of how the core is designed. An embodiment is shown in Figure 8 which shows a three-phase laminated nuclear transformer. The core consists in a conventional manner of three core legs 60, 61 and 62 and the cohesive yokes 63 and 64. In the embodiment shown, both the core legs and the yoke have stepped cross-sections.

Concentrically around the core legs are the cable-shaped windings. The embodiment shown in Figure 9 has, as can be seen, three concentric winding turns 65, 66 and 67. The innermost winding turn 65 may represent the primary winding and the other two winding turns 63 and 64 may 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, in some places around the windings there are spacer rails 68 and 69 with several different functions.

The spacer rails can be formed of insulating material intended to provide a certain space between the concentric winding turns for cooling, bracing, etc. They can also be designed of electrically conductive material to be included in the grounding system of the windings. Fig. 9, no control windings 9 are drawn. 10 15 20 25 30 35 023 510 925 ALTERNATIVE CABLE DESIGNS In the cable variant illustrated in Fig. 10, the same reference numerals as before are used only with the addition of the design characteristic letter a. In this embodiment, the cable comprises several electrical conductors 42a, which are separated by the insulation 44a. In other words, the insulation 44a serves both for insulation between individual adjacent electrical conductors 42 and between them and the environment. The different electrical conductors 42a can be laid in different ways, which causes varying cross-sectional shape of the cable as a whole. The example of Fig. 10 illustrates how the conductors 42a are laid in a straight line, which causes 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. 10, a voltage which is less than a phase voltage is thought to exist between adjacent electrical conductors. More specifically, the electrical conductors 42a in Fig. 10 are thought to be formed by different turns in the winding itself, which means that the voltage between these adjacent conductors is relatively moderate.

As before, a semiconducting outer layer 45a is present outside the insulation 44a provided by a solid insulating material. An inner layer 43a of a semiconductor material is arranged around each of said electrical conductors 42a, i.e. each of them has its own surrounding inner semiconductor layer 43a. This layer 43a will thus function as a potential equalizer with respect to the individual electrical conductor. the variant in Fig. 11 uses the same reference numerals as before only with the addition of the embodiment-specific letter b. Here, too, there are several, more specifically 3, electrical conductors 42b. Between these, in the example, phase voltage is thought to exist, ie a substantially higher voltage than that which exists between conductors 42a in the embodiment according to Fig. 10. In Fig. 11 there is an inner semiconducting layer 43b, inside which the electrical conductors 42b are arranged. However, each of the electrical conductors 42b is enclosed by its own additional layer 70 having properties corresponding to the properties of the inner layer 10b 20 25 5 510 925 24 43b discussed above. There is insulating material between each additional layer 70 and the layer 43b arranged around them. Consequently, the layer 43b will be present as a potential equalizing layer outside the electrical conductors' own additional layers 60 of semiconducting material, these additional layers 70 being adjacent to the respective electrical conductors 42b to be placed on equal potential therewith.

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 has been obtained without departing from the inventive concept as defined in the appended claims. By way of example, it is pointed out that the invention is not limited to the specific material choices exemplified 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 applied in the insulation between those referred to above as "inner" and "outer". It is again pointed out that according to the invention it should not normally be necessary to design the control windings 9 by means of such a flexible cable as discussed above as a consequence of the control winding or control windings normally being at lower voltage than other windings of the current electromagnetic device. More specifically, other windings can be direct high voltage windings. In addition, it is pointed out that the exact principle of control in the practice of the procedure according to the invention can be varied in a number of ways within the framework of the control functions referred to.

Claims (36)

10 15 20 25 30 35 25 510 925 Patent claims An electromagnetic device comprising at least one magnetic circuit (1) and at least one electrical circuit (2,3) comprising at least one winding (4,5), the magnetic and electrical circuits being inductively connected to each other and the device comprising a control device (7) for regulating the function of the device, characterized in that the control device (7) is arranged to regulate frequency, amplitude and / or phase in terms of electrical power to / from the device in that the control device comprises means (9) for regulating the magnetic the current in the magnetic circuit, and that the at least one winding (4,5) or at least a part thereof comprises at least one electrical conductor (42) with an insulation system comprising an electrical insulation (44) formed of a solid insulating material and within it an inner layer ( 43), that the at least one electrical conductor (42) is arranged inside the inner layer (43) and that the inner layer has an electrical conductor which is lower than the conductivity of the electric conductor but sufficient to cause the inner layer (43) to function smoothly with respect to the electric field outside the inner layer. Device according to claim 1, characterized in that the control means comprises at least one control winding (9) inductively connected to the magnetic circuit. Device according to Claim 1 or 2, characterized in that the control device (7) is arranged to control the reluctance in the magnetic circuit. Device according to one of the preceding claims, characterized in that the control device is arranged to add a magnetic additional flux to the magnetic flux in the magnetic circuit. Device according to claim 3, characterized in that the magnetic circuit comprises material with a permeability greater than 1 and that the control device (7) is arranged to control the reluctance in the magnetic circuit by varying the permeability of one or more such zones of the magnetic circuit having variable permeability. . 10 15 20 25 30 35 510 925 26 Device according to claim 5, characterized in that the zone or zones with variable permeability comprise one or more gaps in the magnetic circuit. Device according to one of the preceding claims, characterized in that the magnetic circuit lacks a magnetic core. Device according to one of Claims 1 to 6, characterized in that the winding is wound around a magnetic core (6). Device according to claim 2 and one or more of the remaining claims, characterized in that the control winding (9) and the winding (4,5) of the electrical circuit are arranged to flow through by substantially the same magnetic flux. Device according to one of the preceding claims, characterized in that the device forms a reactor arranged to regulate the frequency, amplitude and / or phase by means of the at least one control winding with respect to the electric power flowing in the winding (4,5) of the electrical circuit. Device according to one of Claims 1 to 8 or 10, characterized in that the electrical circuit (2) has at least two series-connected windings (23, 24), in that the magnetic circuit comprises at least two alternative flow paths (18, 19), in that it at least one control winding is arranged to control the magnetic flux to pass in one or both of these flow paths and that the two windings of the electrical circuit are positioned so that one of them by means of said at least one control winding can be disconnected from magnetic flux. Device according to one of Claims 1 to 9 or 11, characterized in that the magnetic circuit is arranged in the stator or rotor of a rotating electrical machine. Device according to one of Claims 1 to 9, characterized in that the magnetic circuit (1) belongs to a transformer with primary and secondary windings (4,5) and in that the primary and secondary windings 10 15 20 25 30 35 27 510 925 and the control winding (9) are arranged to flow through the same magnetic flux. Device according to one of Claims 1 to 8, in a transformer, characterized in that the secondary winding of the transformer comprises at least two series-connected winding parts, that the magnetic circuit comprises at least two alternative supply paths (18, 19), that at least two existing control windings (9b1, 9b2) 9c1,9c2) are arranged to control the magnetic flux to pass in one or both of these flow paths and that the two winding parts of the secondary winding are positioned so that one of them can be disconnected from magnetic flux by means of the control windings. Device according to one of Claims 11 and 14, characterized in that it has a magnetic core with at least three legs connected in parallel and that two of these belong to different flow paths while the third is common to the two flow paths. Device according to any one of the preceding claims. characterized in that the insulation system outside the insulation comprises an outer layer (45), which has an electrical conductivity which is higher than that of the insulation in order for the outer layer to be able to function as a potential equalizer by connection to earth or otherwise relatively low potential. Device according to any one of the preceding claims, characterized in that the outer layer is arranged to contain substantially the electric field arising due to said electric conductor (42) inside the outer layer (45). Device according to one of the preceding claims, characterized in that the inner layer (43,) and the solid insulation have substantially the same thermal properties. Device according to any one of the preceding claims, characterized therefrom. that the outer layer (45) and the solid insulation have substantially equal thermal properties. 10 15 20 25 30 35 510 925 23 Device according to any one of the preceding claims, characterized in that said at least one conductor (42) constitutes at least one induction revolution. Device according to one of the preceding claims, characterized in that the inner and / or outer layer (43, 45) comprises a semiconducting material. Device according to any one of the preceding claims, characterized in that the inner layer (43) and / or the outer layer (45) has a resistivity in the range 10-6 Qom - 100 mom, preferably 10-3-1000 Qom, preferably 1 -500 Qom. Device according to one of the preceding claims, characterized in that the inner layer (43) and / or the outer layer (45) has a resistance which per meter of conductor / insulation system is in the range 50 pQ - 5 MQ. Device according to one of the preceding claims, characterized in that the solid insulation (44) and the inner layer (43) and / or the outer layer (45) are made of polymeric materials. Device according to one of the preceding claims, characterized in that the inner layer (43) and / or the outer layer (45) and the solid insulation (44) are firmly connected to one another over substantially the entire interface in order to ensure adhesion even during bending. and temperature change. Device according to any one of the preceding claims, characterized in that the solid insulation and the inner layer and / or the outer layer are of material with high elasticity in order to maintain the mutual adhesion during stresses during operation. Device according to any one of the preceding claims, characterized in that the solid insulation and the inner layer and / or the outer layer are of material with substantially equal E-modulus. Device according to one of the preceding claims, characterized in that the inner layer (43) and / or the outer layer (45) and the solid insulation (44) are made of materials with substantially equal thermal coefficients of expansion. Device according to one of the preceding claims, characterized in that the conductor (42) and its insulation system form a winding formed by means of a flexible cable (41). Device according to one of the preceding claims, characterized in that the inner layer (43) is in electrical contact with the at least one electrical conductor (42). Device according to claim 30, characterized in that said at least one electrical conductor (42) comprises a number of strands and that at least one strut of the electrical conductor (42) is at least partially uninsulated and arranged in electrical contact with the inner layer (43). ). Device according to one of the preceding claims, characterized in that the conductor (42) and its insulation system are designed for high voltage, suitably above 10 kV, in particular above 36 kV and preferably above 72.5 kV. Device according to claim 12, characterized in that the magnetic circuit comprises one or more magnetic cores (48) with grooves (50) for the winding (41). Device according to one of Claims 12 and 32 to 33, characterized in that it consists of a generator, motor or synchronous compensator. ~ Device according to one of Claims 12 and 32 to 34, characterized in that it is directly connected to an excessively high voltage network, suitably 36 kV and above, without an intermediate transformer. Device according to one of Claims 1 to 11 and 13 to 32, characterized in that it consists of a power transformer / reactor.