EP0970491B1 - A controllable inductor - Google Patents
A controllable inductor Download PDFInfo
- Publication number
- EP0970491B1 EP0970491B1 EP97919817A EP97919817A EP0970491B1 EP 0970491 B1 EP0970491 B1 EP 0970491B1 EP 97919817 A EP97919817 A EP 97919817A EP 97919817 A EP97919817 A EP 97919817A EP 0970491 B1 EP0970491 B1 EP 0970491B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- core
- part control
- control windings
- inductor according
- windings
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- the present invention relates to a controllable inductor including at least one tubular core, a main winding surrounding the core and a control winding running substantially axially through said core and returning substantially axially outside thereof between said core and said main winding, said control winding being divided into a plurality of separate part control windings.
- controllable inductor is previously known from, for example, the applicant's WO 94/11891.
- controllable is to be given such a wide meaning, that it also comprises the case that a control current, which is constant over time passes through the control winding.
- a controllable inductor of this type connected in series with a capacitor functions as a so-called harmonic filter in connection with a high voltage station for converting direct voltage to alternating voltage and vice versa, its main winding being connected to the high voltage net over a capacitor, usually on the alternating voltage side.
- the permeability of its core and thereby the inductance is adjusted with the aid of the cross-magnetization generated inside the core by causing direct current to run through said control winding, wherein the inductance of the inductor may be adjusted to exactly that frequency an overtone generated in the high voltage net is having for an effective fade-out thereof while causing small energy losses in the inductor.
- the different part control windings of such a controllable inductor are heated partly by the eddy-current losses generated therein because of that the magnet flux generated by the main winding and running substantially longitudinal with respect to the core, passes through said control winding wires, and partly by the direct current running through the wires with the intention to control the inductance of the inductor.
- every part control winding is produced with a number of thin wires, as the power dissipation per unit volume is proportional to the square of the thickness of the metal perpendicular to the flux direction for the metal effected by a certain magnetical flux density.
- the inductor and the control winding are important to dimension the inductor and the control winding in such a way that a high magnetic energy density is achieved in the tubular core, so that the inductor receives a low weight and thereby achieving a low cost.
- the storable energy density in the core is thereby inverse proportional to the permeability of a specific flux density and thus it is important to achieve the highest possible number of ampere-turns of the control winding passing in the core at a specific winding space. This implies of course high heat release and the possibilities to cool the control winding may be decisive for the achievable number of ampere-turns. It is thus desirable to form the core as compact as possible, i.e.
- the part control windings have usually been produced with a substantially circular cross section, the part control windings desirably being arranged to circumferentially abut against each other for a good level of filling of the inner room of the core.
- air channels are formed between different part control windings enabling cooling air to be blown or drawn therethrough for heat exchange with the surfaces of the part control windings.
- the object of the present invention is to provide a solution of the above discussed problem by providing a controllable inductor that enables a substantially higher number of ampere-turns than by previously known controllable inductors at a specific winding space inside the core by enabling a good filling of this space and at the same time provide effective cooling.
- the main part of the adjacent part control windings inside said core are separated by a spacing, which is at least partly defined by substantially parallel surfaces of said part control windings.
- the part control windings have such a cross section that at least some adjacent part control windings outside said core are separated by a spacing, which is at least partly defined by substantially parallel surfaces of said part control windings.
- each part control winding running closest outside and/or inside said core has surfaces extending substantially parallel to surfaces of the envelope of said core for defining a spacing therebetween. It is in this way possible to obtain a desired distance between the part control winding and the core respectively for obtaining the necessary cooling of the part control winding, but thanks to said substantially parallel surfaces and the advantages connected thereto with respect of the cooling, this spacing may be made so "narrow" that a very good filling of the spacing will be obtained inside and outside the core.
- said spacings are substantially completely defined by substantially parallel surfaces of adjacent part control windings, which makes it possible to obtain a very uniform distribution of the cooling air over the complete control winding volume, allowing a high heat release per unit volume in combination with a high degree of filling of the inner room of the core.
- At least some of said part control windings have a form tapering substantially wedge-like towards the centre of said core as seen in a radial cross section through a portion of said windings running inside said core. Thanks to that the respective part control winding has been arranged with such a cross section form, the room inside the core may be filled to a large extent while obtaining spacings defined by substantially parallel surfaces between adjacent part control windings, receiving a circular segment character, and it will be possible to obtain a very large surface available for cooling per unit volume of the control winding in combination with a high degree of filling of the inner room of the core.
- the inductor comprises part control windings, which have a portion thereof running inside said core having a narrow, substantially elongated form in radial direction with respect to said core as seen in a radial cross section.
- part control windings which have a portion thereof running inside said core having a narrow, substantially elongated form in radial direction with respect to said core as seen in a radial cross section.
- the inductor comprises several part control windings located inside each other and running in radial direction with respect to said core and that these part control windings define spacings between each other by substantially tangentially and axially directed surfaces thereof.
- This embodiment is especially suitable for large inductors where the part control windings in this way may be formed more handy while being divided into a larger number while maintaining all the above penetrated advantages of the invention.
- the number of part control windings inside said core increases in radial direction from the centre of the core and outwards along circles with the centre of the core as the centre for filling the inner room of said core.
- a part control winding for a controllable inductor as defived in the preamble of claim 1 can be produced by a method which is characterised by elongated electrical conductors having a mantle comprising a thermoplastic glue layer being wound about a mould to a coil, said coil subsequently being heated to bond the conductors together to a part control winding in one piece.
- the above defined part control windings may be efficiently achieved in this way by simple means.
- Fig 1 schematically illustrates how a controllable inductor 1 according to the invention may be connected over a capacitor C to the alternating voltage side 2 of a station 3 for converting high voltage direct current (HVDC) to alternating current and inversely alternating current to direct current.
- HVDC high voltage direct current
- the controllable inductor works in conjunction with a capacitor as a harmonic filter fading out these overtones, the filter being intended to have a minimum impedance at exactly the frequency that the overtone has, that is intended to be faded out.
- the inductor has a main winding 5 connected to the high voltage net over capacitor, the main winding being wound in layers at a distance outside a cylinder 6 of electrical insulating material.
- the main winding 5 has one end 7 being on a high potential, the voltage thereby falling in direction towards the opposite lower end 8 in Fig. 2, said lower end being on ground potential.
- a cylinder 9 of electrical insulating material is arranged inside the cylinder 6 and running coaxially against the same.
- a core 10 of magnetic material is arranged in the room defined by the cylinder 9, running coaxially against said cylinder.
- This core has a partly conical form at its ends, the form being intended to decrease the eddy-current losses caused by the alternating longitudinal magnet flux generated in the core because of the alternating overtone current in the main winding 5.
- a controllable winding 11 formed by several separate part control windings, passes substantially axially through the core and returning parallel to the axis of the core into the room between the core and the insulating cylinder 9 in a closed loop.
- the control winding 11 is connectable to a direct current source for transmitting a direct current through the same, which direct current will generate a tangentially directed magnet flux in the core running across the main flux and in this way decrease its permeability for the longitudinal magnet flux from the main winding.
- the power dissipation per unit volume due to a magnet flux passing across surfaces of a metal object is proportional to the square of the thickness of the object measured perpendicular to the flux direction, implying the core 10 to being produced by very thin sheets wound in several turns, while the control winding is formed by a large number of thin wires. The heat release in the control winding will thereby be decreased due to eddy-current losses.
- the respective part control winding 12 has an inner portion 13 passing substantially axially through the inner room 38 of the core 10 as well as a substantially axially running outer portion 14 returning outside of the core, which portions form a closed coil, a direct current being able to forced to flow through the coil with not shown means in order to cause a tangentially directed magnet flux in the core, said flux running across the main flux, which is indicated with the arrow 15.
- the part control windings have such a cross section that two adjacent part control windings define spacings 20, 21 inside as well as outside of the core between each other by way of mutually substantially parallel surfaces 16, 17, 18, 19. Said surfaces 16, 17, 18, 19 are extending substantially in radial and axial direction.
- the inner as well as the outer portion has one substantially wedge-formed cross section as seen in radial direction, the insignificant tapering taking place at the outer portion inwardly towards the core may also be represented as a substantially wedge-formed cross section. In this way it is possible to obtain relatively small spacing distances between the different part control windings, obtaining a high degree of filling of the winding room.
- portion 14 running outwardly of the core as well as the inner portion 13 of the respective part control winding has surfaces 22, 23 extending substantially parallel with surfaces of the envelope of the core for defining a spacing 24, 25 respectively therebetween.
- Fig. 4 shows how a plurality of part control windings could be arranged with respect to the core in radial direction inside each other, and that these part control windings between each other define spacings 26 through substantially tangentially and axially directed surfaces of the same, except for that the adjacent part control winding portions 27, 28 through substantially parallel surfaces define spacings between each other.
- the same is also valid for the control winding portions extending outside the core, where however the number of part control windings decrease outwardly, while the number of part control windings inside the core increase in radial direction from the centre of the core.
- This alternative embodiment is most probably especially suitable for large inductors, where the different part control winding coils will be as easy as any to handle, because them being divided in this way.
- the part control windings will be kept in place while defining said spacings between each other and the core through suitable distance parts, as a boat-steering-wheel-like rubber part arranged centrally in the core at 29, which rubber part having tips projecting into between each control winding.
- a support cross 30 arranged in order to unit the complete inductor is also indicated in Fig. 5.
- a mould 31 for producing a part control winding according to the invention is shown in Fig. 5.
- This mould 31 has two elements 34, 35 defining a spacing between each other and provided with inner form defining surfaces 32, 33 converging in a direction towards each other and a distance part 36 dividing said spacing and mutually connecting the elements and arranged to receive elongate electrical conductors wound surrounding the elements while filling the spacings on each side thereof for obtaining a part control winding with the two portions 13, 14 with a substantially wedge-formed cross section.
- a production of a part control winding according to the invention takes place with the aid of this mould 31 in the following way.
- such a coil with a number of parallel wires is wound, resulting in that the number of turns of winding is minimised and that there is a possibility for adaptation to the apparatus that is going to generate the control current running through the coil.
- the coil is thereby preferably wound with a wire provided with an outer thermoplastic layer of glue, so-called bakable wire.
- bakable wire glue
- a winding mould with the described design, it is also possible to form the winding around a mould with for example a rectangular cross section and thereafter forming the coil obtained after the baking to a wedge-form in a subsequent pressing.
- inner part winding portion could for example have said spacings arranged with respect to adjacent part control winding portions and/or have a substantially wedge-formed cross section, while the outer portion possibly could lack these characteristics, in case the cooling problems outside the core would lack importance.
- substantially parallel surfaces in the claims includes at least all angles between such surfaces below 20°. These surfaces do not either have to extend in one plane, but they could have a certain arc-form.
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- Coils Or Transformers For Communication (AREA)
- Coils Of Transformers For General Uses (AREA)
Description
Claims (15)
- A controllable inductor including at least one tubular core (10), a main winding (5) surrounding the core and a control winding (11) running substantially axially through said core and returning substantially axially outside thereof between said core and said main winding, said control winding being divided into a plurality of separate part control windings (12), characterized in that said part control windings have such a cross section that at least some adjacent part control windings inside said core are separated by a spacing (20), which is at least partly defined by substantially parallel surfaces (16, 17) of said part control windings.
- An inductor according to claim 1, characterized in that the main part of the adjacent part control windings (12) inside said core (10) are separated by a spacing (20), which is at least partly defined by substantially parallel surfaces (16, 17) of said part control windings.
- An inductor according to claim 1, characterized in that all adjacent part control windings (12) inside said core (10) are separated by a spacing (20), which is at least partly defined by substantially parallel surfaces (16, 17) of said part control windings.
- An inductor according to any of the claims 1-3, characterized in that said substantially parallel surfaces (16, 17) comprise surfaces extending substantially radially and axially with respect to said core (10).
- An inductor according to any of the claims 1-4, characterized in that said part control windings (12) have such a cross section that at least some adjacent part control windings outside said core (10) are separated by a spacing (21), which is at least partly defined by substantially parallel surfaces (18, 19) of said part control windings.
- An inductor according to any of the claims 1-5, characterized in that each part control winding (12) running closest outside and/or inside said core (10) has surfaces (22, 23) extending substantially parallel to surfaces of the envelope of said core for defining a spacing (24, 25) therebetween.
- An inductor according to any of the claims 1-6, characterized in that it comprises adjacent part control windings, which have spacings (26) defined therebetween by surfaces thereof extending substantially tangentially and axially with respect to said core.
- An inductor according to any of the claims 1-7, characterized in that said spacings (20, 21) are substantially completely defined by substantially parallel surfaces (16, 17) of adjacent part control windings.
- An inductor according to any of the claims 1-8, characterized in that at least some of said part control windings (12) have a form tapering substantially wedge-like towards the centre of said core (10) in a radial cross section through a portion (13) of said windings running inside said core.
- An inductor according to any of the claims 1-9, characterized in that at least some of said part control windings (12) have a form tapering substantially wedge-like towards said core (10) as seen in a radial cross section through a portion (14) of said windings running outside said core.
- An inductor according to any of the claims 1-10, characterized in that it comprises part control windings (12), which have a portion (13) thereof running inside said core having a narrow, substantially elongated form in radial direction with respect to said core (10) as seen in a radial cross section.
- An inductor according to any of the claims 1-11, characterized in that it comprises several part control windings (27, 28) located inside each other and running in radial direction with respect to said core and that these part control windings define spacings (26) between each other by substantially tangentially and axially directed surfaces thereof.
- An inductor according to claim 12, characterized in that the number of part control windings (12) inside said core (10) increases in radial direction from the centre of the core and outwards along circles with the centre of the core as the centre for filling the inner room (38) of said core.
- An inductor according to any of the claims 1-13, characterized in that said part control windings (12) are formed to substantially fill the inner room (38) of said core (10).
- An inductor according to any of the claims 1-14, characterized in that said spacings (20, 21) are substantially more narrow in a radial cross section than the average thickness of said part control windings (12) in such a cross section.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/SE1997/000529 WO1998047159A1 (en) | 1997-03-26 | 1997-03-26 | A controllable inductor |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0970491A1 EP0970491A1 (en) | 2000-01-12 |
EP0970491B1 true EP0970491B1 (en) | 2002-10-16 |
Family
ID=20405801
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP97919817A Expired - Lifetime EP0970491B1 (en) | 1997-03-26 | 1997-03-26 | A controllable inductor |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0970491B1 (en) |
JP (1) | JP2001526835A (en) |
DE (1) | DE69716482T2 (en) |
-
1997
- 1997-03-26 DE DE69716482T patent/DE69716482T2/en not_active Expired - Lifetime
- 1997-03-26 JP JP54096398A patent/JP2001526835A/en active Pending
- 1997-03-26 EP EP97919817A patent/EP0970491B1/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
EP0970491A1 (en) | 2000-01-12 |
JP2001526835A (en) | 2001-12-18 |
DE69716482D1 (en) | 2002-11-21 |
DE69716482T2 (en) | 2003-06-26 |
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