EP3861562B1 - Magnetkernanordnung, induktive vorrichtung und installationsvorrichtung - Google Patents

Magnetkernanordnung, induktive vorrichtung und installationsvorrichtung Download PDF

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Publication number
EP3861562B1
EP3861562B1 EP19779919.0A EP19779919A EP3861562B1 EP 3861562 B1 EP3861562 B1 EP 3861562B1 EP 19779919 A EP19779919 A EP 19779919A EP 3861562 B1 EP3861562 B1 EP 3861562B1
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Prior art keywords
magnetic core
magnetic
core
gap
equal
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English (en)
French (fr)
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EP3861562A1 (de
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Rolf DISSELNKÖTTER
Jimmy Kjellsson
Adrian Hozoi
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Hitachi Energy Ltd
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Hitachi Energy Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F3/00—Cores, Yokes, or armatures
    • H01F3/10—Composite arrangements of magnetic circuits
    • H01F3/14—Constrictions; Gaps, e.g. air-gaps

Definitions

  • aspects of the invention relate to a magnetic core arrangement, in particular a transformer core arrangement, comprising at least two stacked cores forming a so called composite core, in particular ring-like cores, each comprising one or more core segments.
  • an inductive device such as an inductor or transformer, including at least one core arrangement, and an installation device including at least one of said inductive devices, in particular a transformer and/or inductor.
  • a magnetic core typically includes one or more pieces of ferromagnetic material with high magnetic permeability used to confine and guide magnetic fields in electrical, electromechanical, and magnetic devices.
  • Inductive devices such as inductors or transformers using a magnetic core are known and widely used in electrical equipment. Modern electrical equipment is required to provide increasingly better performance, functionality, operation range, and robustness, leading to technical challenges.
  • Wider operating frequency range may be required in order to deal with various rated frequencies, high frequency harmonics, and low frequency or high frequency signals caused by fault conditions.
  • typical rated frequencies in electrical power and distribution equipment are 16.7 Hz, 50 Hz, 60 Hz, but harmonics well above 1 kHz may be present.
  • Transitory signals with very low frequency content, e.g. below 5 Hz, or very high frequency content, e.g. above 10 kHz, are possible in case of fault conditions.
  • Wide operating frequency range may also be required in case of power drives and converters.
  • DC currents or low frequency currents may be present in AC power lines because of the type of equipment connected to the grid or because of fault conditions such as short circuits.
  • Very large transitory currents with very low frequency content, e.g. below 5 Hz, or very high frequency content, e.g. above 10 kHz, are possible in case of fault conditions or switching.
  • DC signals are limiting the AC operating range of inductive components with ferromagnetic cores and may even cause them to fail.
  • Transformers can be particularly sensitive to DC signals as even tiny DC currents can cause them to saturate.
  • modern inductive components are often required to be able to operate under moderate DC currents caused by modern equipment or under severe DC currents caused by fault conditions.
  • inductive devices are desired to provide excellent AC performance over a wide frequency range but also to withstand high DC currents while providing acceptable AC performance.
  • Such transformers are desired to accurately measure AC currents comprised in a very wide range, possibly from 1 mA to 1000 A, and from 16 Hz to 10 kHz. Furthermore, they are also desired to withstand comparably high DC currents without saturating.
  • the current transformers are desired to be ideally compact and lightweight.
  • the effective permeability may be representative for the magnetic core and it is usually not identical to the permeability of the pure ferromagnetic material but it may be also influenced by the construction of the core.
  • the effective permeability may depend on multiple factors related to the construction of the core such as the orientation of the magnetic material, filling ratio, presence of gaps, mechanical stresses or strains, etc.
  • the effective permeability can be a practical way to compare cores fabricated using different technologies and/or materials. Experimentally, it can be determined from inductance or hysteresis measurements (B-H curves), without applying corrections related to the construction of the core.
  • Hysteresis measurements are typically employed to also measure other magnetic properties of the core, such as saturation flux density, B s , and residual magnetic flux density, B r .
  • the magnetic properties of the core may be seen as being representative for the core and are usually a result of the construction of the core and of the magnetic properties of the ferromagnetic material(s) employed.
  • a composite core including two ferromagnetic cores one core with very high permeability and one core with moderate permeability.
  • Current transformers with composite cores are known from JPS58216412 and JP5525270 , where one of the cores includes at least one gap to lower its effective permeability.
  • the core with high permeability is a non-gapped core.
  • the composite core features thus two operating regimes: at null or weak DC currents, high effective permeability is ensured by the non-gapped core; at increasing DC current, low effective permeability is ensured by the gapped core and the non-gapped core saturates.
  • the relative permeability of the non-gapped core needs to be very high, for example having a value comprised between 20000 and 100000.
  • the permalloy core disclosed in JP5525270 would feature a value of the permeability value in the upper range of the interval.
  • the effective relative permeability of the gapped core needs to be low, e.g. less than 4000.
  • acceptable AC performance under DC currents still needs to be provided, which requires the gapped core to feature a sufficiently large value of the effective relative permeability, e.g. above 400.
  • a small value of the total gap width is thus needed, e.g. less than 0.25 mm.
  • the total gap width is equal to the sum of the width of all gaps, taking usually the mean values, and it is used to generally describe a core with one or more gaps.
  • the width of each gap must be 0.05 mm and cannot be precisely produced using available methods.
  • Fabricating thin gaps with precise width is technically very challenging and the problem becomes increasingly severe as the gap is thinner, for example in the order of 0.1 mm or less.
  • the gap width must be precise and stable over the operating conditions and lifetime of the core in order to ensure reliable and reproducible performance. Practical means to fabricate gaps with precise and thin width, e.g. below 0.25 mm, are not known from state of the art.
  • the composite core has two ring cores fabricated from stacked laminations, such construction being mainly suitable for isotropic ferromagnetic materials with relatively large thickness of the laminations, e.g. above 0.2 mm. This drastically limits the choice of useable materials as practically all ferromagnetic materials featuring low magnetic losses and high saturation magnetic flux density are anisotropic and/or feature thin laminations. Grain-oriented electrical steels, amorphous alloys, and nanocrystalline alloys are thus excluded.
  • the gap of the gapped core is processed involving elastic forces present in the core, resulting in residual strain which is detrimental to the magnetic properties.
  • the non-gapped core is made from permalloy and it features thus limited saturation flux density, B s ⁇ 0.8 T.
  • Composite cores are still facing technical challenges related to optimizing the AC performance and their saturating limit, especially the DC withstand. Providing thin gaps with precise width is one major problem and it becomes increasingly severe as the gap is thinner, for example in the order of 0.1 mm or less. Such practical constraints has made the usage of composite cores unpopular.
  • a magnetic core arrangement according to claim 1 an inductive device, such as an inductor or a current transformer, comprising at least one such magnetic core arrangement according to claim 15, and an installation device according to claim 16 are provided.
  • a magnetic core arrangement for an inductive device such as an inductor or a transformer
  • the core arrangement includes at least two cores primarily made from magnetic material, wherein a first core and a second core having lower effective permeability than the first core are provided and combined forming a so called composite core.
  • the second core includes at least one non-magnetic gap, provided in the magnetic path of the core, so as to form at least one semi- or partly ring-like magnetic structure.
  • the non-magnetic gap is filled partly or totally with a resin such as an adhesive compound.
  • a current transformer comprising the disclosed core arrangement is provided.
  • An exemplary current transformer may include a primary winding or an opening for a primary winding, and a secondary winding being coupled to the core arrangement.
  • the primary winding and/or the secondary winding are configured to be wound around the magnetic core arrangement as described above.
  • an installation device includes at least one inductive device, in particular an inductor or transformer as described above.
  • the inductive device in particular an inductor or transformer, may include at least one electrical winding, which is configured to be wound around a magnetic core arrangement as described above.
  • a transformer one or more of said magnetic core arrangements may be applied.
  • the proposed magnetic core arrangement according to the invention may be applied to various inductive devices, like for example choke(s), inductor(s), or transformer(s), wherein the proposed core arrangement allows having increased inductance, wider AC current and frequency operating range, higher DC current withstand, reduced size, lower mass, and/or lower cost.
  • said magnetic core arrangement applied to an inductive device, in particular a current transformer or inductor would also feature improved accuracy.
  • the gap comprises resin and one or more solid spacer(s) inserted partly or fully into the gap and/or filler particles dispersed in the resin.
  • the solid spacer may include and/or is composed of filler particles dispersed in the adhesive.
  • the filler particles can be commonly available filler particles being employed in other technical fields, such as for example as fillers for composite materials, grinding media, or blasting media.
  • the filler particles can be microparticles, microsperes, beads, or grains having with desired tolerances and particle size distributions.
  • the filler particles are microparticles made from an electrically non-conductive material.
  • the microparticles can be dispersed in the adhesive prior to application.
  • the microparticles can be made of and/or include a non-organic material, such assilica, glass, sand, ceramic, or compositions thereof.
  • Silica or ceramic-based microparticles are commonly employed in different technical fields as fillers to be mixed with polymers to produce casting resins and other composite materials featuring improved structural properties.
  • Structural adhesives containing premixed fillers are commercially available or they may be prepared on-site using common adhesive handling equipment.
  • microparticles can be employed to refer to tiny particles having a size, such as an average diameter, ranging from 1 ⁇ m to 1000 ⁇ m, specifically being equal to or smaller than 1000 ⁇ m.
  • the size of the microparticles may range, for example, between 1 ⁇ m and 250 ⁇ m, Specifically, the microparticles may be equal to or smaller in size than 250 ⁇ m.
  • Various techniques exist to measure and/or to characterize the particle size such as laser diffraction, morphological imaging, optical imaging, or microscopy.
  • the first magnetic core can have a higher permeability than the second magnetic core.
  • the first magnetic core can provide a high permeability, achieve good AC performance and low losses and/or the second core can provide a low permeability, achieve a good DC withstand and avoid saturation.
  • the second magnetic core can have an effective relative permeability of equal to or greater than 400 and/or of equal to or smaller than 4000. Additionally or alternatively, the second magnetic core can have a magnetic saturation flux density being equal to or larger than 1.5 T.
  • the first magnetic core and the second magnetic core can have approximately or almost the same inner and/or outer diameters. Additionally or alternatively, the first magnetic core and the second magnetic core are stacked together to form the composite core. For instance, as depicted e.g. in Fig. 1A , the first magnetic core and the second magnetic core may be stacked together along the axis, in particular the rotary axis. Accordingly, the axis of the composite core and/or of the second magnetic core, can be the direction along which the first magnetic core and the second magnetic core are stacked together. According to embodiments described herein, the first magnetic core and the second magnetic core can be arranged coaxially.
  • the second magnetic core can include at least two gaps.
  • the second magnetic core may be formed from two parts and subportions respectively.
  • the second magnetic core has two non-magnetic gaps between the two subportions.
  • the subportions are shaped as half-rings.
  • the two subportions can be of approximately equal size.
  • “approximately equal size” such as when referring to the size of the two subportions, may be understood as being equal in size within manufacturing tolerances and/or in a manner that does not alter the electrical properties of the two subportions with respect to each other by more than 10%, specifically by not more than 5%.
  • the second magnetic core can be cut into two half-cores which are joined such that two non-magnetic gaps are created at the joining interfaces.
  • the half-cores or subportions can be joined by the adhesive and the width of the two non-magnetic gaps can be precisely controlled, e.g. by using the solid spacers.
  • the second magnetic core can be based on a tape-wound core which is cut into two half-cores which are subsequently joint such that two non-magnetic gaps are created at the joining interfaces.
  • a current transformer is provided and claimed, which is based on the composite core described herein.
  • the current transformer may include a secondary electrical winding which can be wound on the composite core.
  • the secondary electrical winding can be preferably homogenously distributed over the composite core.
  • the current transformer may be provided with a primary winding or with an opening where a primary conductor may be inserted to serve as a primary winding.
  • a current transformer which includes a primary winding or an opening for a primary winding, and/or a secondary winding.
  • the primary winding and/or the secondary winding can be configured to be wound around a composite core as described herein.
  • the secondary winding can be homogenously distributed over the composite core.
  • a primary conductor may be inserted into the opening to serve as a primary winding.
  • the primary winding and/or the secondary winding can be a primary electrical winding and/or a secondary electrical winding, respectively.
  • the current transformer may include a mechanical casing, fixation(s), electrical contacts and other practical accessories enabling optimum usage and integration of the device.
  • current transformers that are compact and/or provide excellent accuracy over wide AC current range spreading over several decades can be provided.
  • the current transformers described herein can be configured to accurately measure AC currents in a range between 1 mA and 1000 A, and/or to withstand DC currents up to 100 A or even above without saturating.
  • current transformers that are compact and lightweight can be provided.
  • the current transformer can have a composite core including a first magnetic core and a second magnetic core, wherein the first magnetic core and the second magnetic core are beneficially ring shaped, even though other geometries are also possible.
  • the first magnetic core and the second magnetic core may be assembled in concentrical arrangement or stacked arrangement.
  • a stacked arrangement is, e.g., shown in Figs. 1A and 1B and may imply that the first magnetic core and the second magnetic core have approximately equal inner and outer diameters.
  • first magnetic core and/or the second magnetic core can be beneficially provided with a polymer coating, such as epoxy.
  • a polymer coating such as epoxy. This ensures a smooth surface suitable for applying the electrical windings without having to enclose the composite core in a case. Avoiding a case can be suitable for minimizing dimensions of the current transformer and/or minimizing a resistance of the secondary winding, which may result in better electrical performance such as accuracy and wider range.
  • the first magnetic core and the second magnetic core can be fixed together by various means, for example using adhesive joining or adhesive tape.
  • first magnetic core and the second magnetic core of the composite core of the current transformer may complement each other efficiently in order to provide both excellent AC accuracy and withstand of DC currents. Accordingly, AC operation range, AC accuracy, and/or DC withstand capabilities can be maximized.
  • the current transformer can be employed for the measurement of electrical current in an installation device or installation unit, such as protection relays.
  • an installation device including at least one current transformer can be provided.
  • the installation device can include one current transformer per current phase.
  • the installation device can include three or four current transformers in 3-phase applications.
  • a total gap width of the second core portion i.e. the sum of all gaps, can have a value typically of between 0.05 mm and 0.25 mm.
  • the particular value of the total gap width may depend on the specific application and it may be precise and stable over operating conditions in order to ensure reliable results.
  • the installation device can include a network interface for connecting the installation device to a data network, in particular a global data network.
  • the data network may be a TCP/IP network such as Internet.
  • the installation device can be operatively connected to the network interface for carrying out commands received from the data network.
  • the commands may include a control command for controlling the installation device to carry out a task such as measuring a current.
  • the installation device is adapted for carrying out the task in response to the control command.
  • the commands may include a status request.
  • the installation device may be adapted for sending a status information to the network interface, and the network interface can then be adapted for sending the status information over the network.
  • the commands may include an update command including update data.
  • the installation device is adapted for initiating an update in response to the update command and using the update data.
  • the data network may be an Ethernet network using TCP/IP such as LAN, WAN or Internet.
  • the data network may comprise distributed storage units such as Cloud.
  • the Cloud can be in form of public, private, hybrid or community Cloud.
  • the present application may provide inductive devices, such as the composite core, transformer and installation unit, having excellent AC performance at low to medium frequencies and that are able to withstand of high DC currents.
  • inductive devices such as the composite core, transformer and installation unit
  • withstand of high DC currents may be understood and/or may imply that acceptable AC performance may be provided even when the device is subjected to high DC currents.
  • Figs. 1A and 1B show a side view and a top view, respectively, of a magnetic core arrangement 100 comprising cores of different effective permeability forming a so called composite core according to embodiments described herein.
  • the magnetic core arrangement 100 according to the disclosed embodiment of figures 1A and 1B comprises two stacked ring-like cores forming a so called composite core primarily made from magnetic material, wherein a first core 110 and a second core 120 having lower effective permeability than the first core and made from and/or including a magnetic material, specifically a ferromagnetic material, are provided.
  • the second core 120 includes a one non-magnetic gap 122, provided in the magnetic path of the second core 120, so as to form at least one semi- or partly ring-like magnetic structure.
  • the non-magnetic gap 122 is filled partly or totally with a resin such as an adhesive compound, in particular in order to adjust and control the gap width and permeability accordingly and/or to increase structural stability of the core.
  • the non-magnetic gap is provided and/or arranged in the magnetic material of the second core 120, e.g. by cutting or locally removing the magnetic material of the second core 120. Specifically, the non-magnetic gap is provided and/or arranged in the magnetic material of the second core 120 such that it interrupts the magnetic path of the second core 120.
  • a medium may be understood as “magnetic” if the relative value of its magnetic permeability is significantly larger than 1, for example up to orders of magnitude larger than the magnetic permeability of vacuum. Further, a medium may be understood as "non-magnetic” if the relative value of its magnetic permeability is approximately equal to 1, i.e. it is in the same order of magnitude as the magnetic permeability of vacuum.
  • the non-magnetic gap has a magnetic permeability which is significantly lower than the permeability of the magnetic material of the second core 120.
  • the magnetic permeability of a gapped core such as the second core 120, largely depends on the dimensions of the gap and/or the filling of the gap.
  • the width of the gap mainly determines the effective permeability and remanence of the gapped core.
  • the gap can be provided in a way that the surface normal of the adjacent cross sections of the core and/or gap are oriented in a direction parallel or approximately parallel to the magnetic path of the core. Alternatively, it is also possible to provide the gap at different angles to the magnetic path of the core.
  • the at least one non-magnetic gap 122 is filled by and/or with a resin.
  • the resin can be an adhesive or adhesive compound. Accordingly, whenever “adhesive” or “adhesive compound” is mentioned herein it can be replaced by “resin", unless it is technically not meaningful.
  • the filling of the at least one non-magnetic gap 122 by and/or with a resin can allow a precise control of a width of the at least one non-magnetic gap 122.
  • the at least one non-magnetic gap 122 can be reliably formed with an intended width, specifically with a small width.
  • the at least one non-magnetic gap 122 and/or the width of the at least one non-magnetic gap 122 can be precisely set to obtain a desired DC performance in practice.
  • the at least one non-magnetic gap 122 can be configured to obtain moderate AC performance and high DC withstand. In this way, an optimum balance between AC performance and DC withstand is provided for the magnetic core arrangement.
  • the first magnetic core can be optimized for excellent AC accuracy and also for moderate DC withstand and/or the second magnetic core can be optimized for moderate AC accuracy and strong DC withstand.
  • the first magnetic core 110 can have a higher permeability than the second magnetic core 120.
  • the first magnetic core 110 can provide a high permeability, achieve good AC performance and low losses and/or the second core 120 can provide a low permeability, achieve a good DC withstand and avoid saturation. Accordingly, an optimum balance between AC performance and DC withstand can be provided for the magnetic core arrangement 100 in practice.
  • the magnetic core arrangement or so called composite core 100 can include two magnetic cores, i.e. the first magnetic core 110 and the second magnetic core 120, featuring different inductance values and saturation limits.
  • the first magnetic core 110 can provide high inductance and can be an excellent performer under predominantly AC currents, while the second magnetic core 120 can provides lower inductance and can be harder to saturate under DC currents.
  • the first magnetic core 110 and the second magnetic core 120 can be primarily made from magnetic material, such as ferromagnetic material, with high relative permeability.
  • the first magnetic core 110 and/or the second magnetic core 120 can beneficially have a tape-wound construction in order to provide optimal combination between compact size, high permeability, and low losses.
  • the first magnetic core 110 and/or the second magnetic core 120 can beneficially be shaped like a ring or approximately like a ring, however, other geometries such as oval or rectangular are also possible.
  • the first magnetic core 110 and/or the second magnetic core 120 may be assembled in concentric arrangement or in stacked arrangement.
  • the first magnetic core 110 and/or the second magnetic core 120 can beneficially in a stacked arrangement can beneficially have almost the same inner and outer dimensions or radii.
  • the first magnetic core 110 and/or the second magnetic core 120 can be fixed together by various means, for example using adhesive joining means, tape, clamps, etc.
  • Fig. 1 shows an example of the core arrangement where two ring shaped cores are assembled in a stacked manner, featuring approximately equal inner and outer diameters.
  • the first magnetic core 110 can be provided with sufficiently high permeability in order to ensure excellent AC performance but specifically not excessively high in order to withstand low levels of DC current without saturating. For typical applications, optimum tradeoffs can be achieved when its effective permeability has a value between 20000 and 60000.
  • the first magnetic core 110 can also have a sufficiently high saturation magnetic induction, Bs, above 0.8 T, and/or low remanence Br/Bs ⁇ 0.3, in order to reach sufficiently large operation range.
  • cores made from nanocrystalline alloys similar to those described for example in EP0271657 , are available with both high permeability and exceptionally low losses, and can be used as the first magnetic core 110. They can be produced in different grades with various permeability and remanence values allowing to optimally tune the desired magnetic properties of the core.
  • the first magnetic core 110 may have an effective relative permeability of equal to or greater than 20000 and/or of equal to or smaller than 60000. Additionally or alternatively, the first magnetic core 110 may have a remanence flux density being lower, e.g. less than 30%, than a saturation flux density When practicing embodiments, the first magnetic core can be provided with a high enough permeability in order to ensure excellent AC performance but not excessively high in order to withstand low levels of DC current without saturating.
  • the first magnetic core 110 can have a sufficiently high saturation magnetic induction, B s , of e.g. equal to or greater than 0.8 T, and/or a low remanence B r / B s ⁇ 0.3, in order to reach sufficiently large operation range.
  • B s sufficiently high saturation magnetic induction
  • the first magnetic core 110 can be such a nanocrystalline core, in particular a Fe-based nanocrystalline core.
  • the first magnetic core 110 can be undergone a thermal and magnetic annealing process.
  • the second magnetic core 120 can be provided with an effective permeability which is low enough in order to prevent the core from saturating when subject to high DC currents but specifically still sufficiently high to allow reproducing AC signals with acceptable accuracy.
  • the effective permeability of the second magnetic core 120 can be controlled by providing the second magnetic core 120 with the at least one non-magnetic gap 122, such that it interrupts the magnetic path of the second magnetic core 120.
  • the at least one non-magnetic gap 122 can interrupt the magnetic path of the second magnetic core 120.
  • the at least one non-magnetic gap 122 may be implemented by cutting or locally removing the magnetic material of the second magnetic core 120.
  • the at least one non-magnetic gap 122 can be provided by a cut extending in radial direction and wherein the intersection planes are aligned almost orthogonal to the magnetic path of the core.
  • a permeability of the at least one non-magnetic gap 122 is much lower than the permeability of the magnetic material of the second magnetic core 120, implying that the effective permeability of the second magnetic core 120 would largely depend on the width of the at least one non-magnetic gap 122.
  • the value of the effective relative permeability should be precise in order to ensure reliable and reproducible results. For example, it was found that the effective permeability may have to be set between 400 and 4000 depending on the particular requirements of the intended application. Such values for the effective permeability of the core would typically lead to a at least one non-magnetic gap 122 with small width, i.e. lower than 0.25 mm.
  • the gap width may be between 0.05 mm and 0.1 mm, however, other values between 0.03 mm and 0.25 mm are possible.
  • the width of the at least one non-magnetic gap 122 should be precise and stable in order to ensure reliable and reproducible performance of the core.
  • the second magnetic core 120 can have an effective relative permeability of equal to or greater than 400 and/or of equal to or smaller than 4000. Additionally or alternatively, the second magnetic core 120 can have a magnetic saturation flux density being equal to or larger than 1.5 T.
  • the effective permeability of the second magnetic core can be optimally controlled and/or the magnetic performance of the core can be tailored to obtain the desired magnetic response.
  • the second magnetic core can thus be finely optimized to provide the desired response when DC currents are present.
  • the second magnetic core 120 can be provided with an effective permeability which is low enough in order to prevent the magnetic core arrangement 100 from saturating when subject to high DC currents but still sufficient to allow reproducing AC signals with acceptable accuracy.
  • the second magnetic core 120 can also have a high saturation magnetic induction, B s , and/or a low remanence, B r .
  • the second magnetic core 120 can have a saturation magnetic induction, B s , larger than 1.5 T, remanence B r / B s ⁇ 0.3, and/or effective relative permeability which can be between 400 and 4000 depending on the particular requirements of the application.
  • the value of the effective relative permeability can be precisely controlled in order to ensure reliable and reproducible results.
  • the magnetic losses of the second magnetic core 120 can be kept low in order to provide acceptable AC performance.
  • Grain-oriented electrical steel may provide the highest saturation magnetic induction out of ferromagnetic core materials available with moderately low magnetic losses. Accordingly, the first magnetic core 110 and/or the second magnetic core 120 can be made from and/or include grain-oriented electrical steel. As grain-oriented electrical steel is an anisotropic material, a magnetic properties of grain-oriented electrical steel can be best exploited in tape-wound core constructions resulting in compact dimensions but also maximum saturation magnetic induction, B s > 1.8 T, and minimum losses. Accordingly, the first magnetic core 110 and/or the second magnetic core 120 can have a tape-wound core construction.
  • the first magnetic core 110 can be a tape-wound magnetic core manufactured from nanocrystalline alloy, and/or the second magnetic core 120 can be based on a tape-wound core manufactured from grain-oriented electrical steel.
  • the permeability of the magnetic core arrangement or formed composite core can be optimized.
  • the width of the at least one non-magnetic gap 122 can be equal to or smaller than 0.5 mm, specifically equal to or smaller than 0.35 mm, particularly equal to or smaller than 0.25 mm, and/or equal to or greater than 0.01 mm, specifically equal to or greater than 0.03 mm, particularly equal to or greater than 0.05 mm. Additionally or alternatively, a sum of the widths of all of the at least one non-magnetic gap 122 can be equal to or small than 0.5 mm, specifically equal to or smaller than 0.35 mm, particularly equal to or smaller than 0.25 mm, and/or equal to or greater than 0.01 mm, specifically equal to or greater than 0.03 mm, particularly equal to or greater than 0.05 mm. Further, in case at least two non-magnetic gaps 122 are provided, the at least two non-magnetic gaps 122 can have a same or different width.
  • the total width of the at least one non-magnetic gap 122 i.e. the sum of the widths of all of the at least one non-magnetic gap 122, can determine the effective permeability of the composite core 100.
  • the at least one non-magnetic gap 122 may also cause a self-demagnetization effect of the composite core 100, which may lower significantly the residual flux density, B r , significantly.
  • the effective permeability value and the remanence of the composite core 100 may thus be controlled by the total gap width.
  • the resin such as a polymer or an adhesive compound
  • the resin may be applied in liquid state in the at least one gap 122 and reach a solid state when fully processed.
  • the resin may also be available for application in other states, such as paste or powder.
  • the resin can be a solid compound providing adhesive bonding to the magnetic material of the second magnetic core 120 and/or ensuring structural stability of the second magnetic core 120. This would strengthen the second magnetic core 120 and allow it to better withstand mechanical pressure exerted during further processing and operation, resulting in reduced stress and deformation.
  • the gap may be fully or partly filled with resin.
  • the resin may be based on one or more components and could be employed in combination with suitable surface activators.
  • Various resin types may be employed, as for example based on epoxy, polyurethane, acrylic, or some other technology.
  • a solid spacer 124 may be introduced in the at least one gap 122, particularly in order to further adjust the precision and the stability of the at least one gap 122 (see Figs. 2A and 2B ).
  • the cut width may be slightly larger than the intended width of the gap.
  • Using an appropriate spacer 124 and gentle pressure on the second magnetic core 120 would allow to stabilize and fix the at least one gap 122 and reach the intended gap width.
  • This method may also provide a benefit that it allows producing a thin gap using a cut width which is larger than the intended final gap width. The cutting process may then be easier to implement and common tooling may be employed resulting in lower production cost.
  • the solid spacer 124 may help to produce the at least one gap 122 with improved precision and/or stability of the width.
  • the spacer 124 may occupy a significant portion of the width of the at least one gap 122, for example at least 60%. It would not necessarily occupy the full width of the at least one gap 122 as resin may be entrapped between the spacer 124 and the gap surfaces of the second magnetic core 120.
  • the solid spacer 124 can be made from a different material than the resin, being beneficially non-magnetic and electrically non-conductive. If an electrically conductive spacer 124 is employed, then its dimensions may be formed sufficiently small, e.g. significantly smaller than the cross-section of the second magnetic core 120, in order to avoid noticeable losses caused by eddy currents induced in the spacer 124. It may be beneficial to fabricate the solid spacer from a material with good mechanical stability and low coefficient of thermal expansion, for example based on ceramic or glass. Excellent stability over the operating conditions and lifetime of the inductive component would be then ensured. One or more solid spacers may be provided in the at least one gap 122.
  • the adhesive can include the solid spacer 124 defining the at least one non-magnetic gap 122.
  • the solid spacer 124 can be inserted into at least one of the at least one non-magnetic gaps 122.
  • the solid spacer can be made from and/or include an electrically non-conductive material.
  • "defining the at least one non-magnetic gap” can be understood as providing the at least one non-magnetic gap 122 with a desired width.
  • the solid spacer can further facilitate forming of the at least one non-magnetic gap 122a with an intended width.
  • the solid spacer 124 is based on filler particles dispersed or mixed in the resin.
  • the filler particles can be commonly available fillers employed in composite materials or particles available in other technical fields, such as grinding media, or blasting media. They are often referred to as microparticles, microspheres, beads, or grains and are commonly available with guaranteed tolerances and particle size distributions.
  • microparticles is usually employed to refer to tiny particles having the size, such as the average diameter, ranging from 1 ⁇ m to 1000 ⁇ m. In the context of the present application, the size of the microparticles may range, for example, between 5 ⁇ m and 250 ⁇ m.
  • Various techniques exist to measure and/or to characterize the particle size such as laser diffraction, morphological imaging, optical imaging, or microscopy.
  • the filler particles can be microparticles preferably made from a material which is non-magnetic and electrically non-conductive. They may include or consist of non-organic material, such as for example silica, glass, sand, ceramic, or combinations thereof. Silica or ceramic-based microparticles are commonly employed in different technical fields as fillers to be mixed with polymers to produce casting resins and other composite materials featuring improved structural properties. It is possible to disperse and/or mix the microparticles in the resin prior to applying the resin in the at least one gap 120, resulting in a practical and convenient binding process. Structural adhesives or resins containing premixed fillers are commercially available or they may be prepared on-site using common mixing and dispensing equipment. Epoxy adhesives filled with non-organic microparticles are known to provide high quality structural bonding. However, other resins or adhesives are also encompassed, e.g. based on polyurethanes or other substances, like for example compounds.
  • the size of the microparticles and their concentration in the resin may be conveniently selected in order to prepare a composite resin which can be employed to simultaneously stabilize and fix the width of the at least one gap 122 and to bind the second magnetic core 120. It is possible to use, for example, low concentration of microparticles such that clustering is prevented. It can then be possible to achieve a gap width which is marginally larger than the size of the predominantly large microparticles, using for example appropriate resin and delicate pressure on the second magnetic core 120 to gently compress the at least one gap 122. In this case, at least some of the larger particles can have the size of greater than 75% of the width of the at least one gap 122.
  • a width of the at least one non-magnetic gap can be produced with a simple and cost effective assembly process. Furthermore, the stability of the adhesive in terms of temperature, humidity, and ageing can be improved.
  • Controlling a width of the at least one non-magnetic gap of the second magnetic core using an adhesive filled with microparticles can thus be a convenient manufacturing process, easy to apply using commonly available equipment and materials. Selecting the appropriate microparticles may allow precise control of the gap width.
  • the adhesive can be an epoxy. Epoxy adhesives filled with non-organic microparticles are known to provide high quality structural bonding. However, other adhesive are also encompassed, e.g. based on polyurethanes.
  • non-organic fillers stabilize the structural properties of the adhesive resulting in improved stability of the gap width versus temperature, humidity, and ageing.
  • the gap width can be thus precisely maintained over wide operating climatic conditions and the lifetime of the device.
  • At least one, specifically non-magnetic, gap with small width can be thus precisely produced using simple and cost effective processing means. Furthermore, improved stability of the gap width is ensured versus temperature, humidity, and ageing. The gap width can be thus precisely maintained over wide operating climatic conditions and over the lifetime of the inductive component.
  • Two or more non-magnetic gaps can in particular be formed by joining adjacent parts of the second magnetic core.
  • the joining may be achieved by employing a bonding technique where the adhesive is provided between the adjacent parts to define the gap width.
  • Figs. 3A and 3B show an exemplary magnetic core arrangement forming a composite core 100 having at least two gaps 122a, 122b, specifically with two gaps 122a, 122b, formed in the second magnetic core 120.
  • the second magnetic core 120 can be cut into two pieces, such as two half-cores.
  • the two core pieces can be joined using the resin to provide adequate binding and to produce two non-magnetic gaps 122a, 122b at the joining interfaces.
  • the width of one or of both gaps 122a, 122b can be conveniently controlled using appropriate spacer(s) or microparticles as described herein.
  • the total width of the gaps 122a, 122b i.e.
  • the sum of the widths of the two gaps 122a, 122b, can determine the effective permeability of the second magnetic core 120. Cutting one magnetic core into two pieces is a widely available, well-established process and may be easier and cheaper to implement than cutting one single gap with very small width.
  • a second magnetic core 120 with one gap 122 or a second magnetic core 120 with two gaps 122a, 122b, or even more gaps may be more beneficial.
  • the provided solution will result in low mechanical stresses induced in the core which may cause degradation or reduction of the magnetic losses.
  • employing a resin filled with appropriate microparticles may allow to conveniently produce thin gaps featuring precise and stable width at attractive cost. It is then possible to reliably control the effective permeability of the second core portion.
  • the inductance of the core can be thus conveniently tailored to obtain the desired electromagnetic response.
  • the gap(s) may also cause a self-demagnetization effect of the core which can reduce the remanence, Br, which typically becomes very low, for example Br/Bs ⁇ 0.1. Excellent reproducibility and operating range of the core may thus be ensured in practice.
  • the second core beneficially also has a high saturation magnetic induction, Bs.
  • the magnetic losses of the second core can be beneficially low in order to provide acceptable AC performance.
  • Grain-oriented electrical steel may provide the highest saturation magnetic induction out of ferromagnetic core materials available with moderately low magnetic losses. Because it is an anisotropic material, its magnetic properties are best exploited in tape-wound core constructions resulting in compact dimensions but also high saturation magnetic induction, Bs > 1.8 T, and minimum losses.
  • the second magnetic core can thus be finely optimized to provide the desired response when DC currents are present.
  • Setting the width of at least one non-magnetic gap of the second core using a resin possibly filled with microparticles may be a convenient manufacturing process, easy to apply based on commonly available equipment and materials.
  • Suitable microparticles can be selected to precisely control the width of the gap(s) and to ensure great stability versus operating conditions and aging.
  • the magnetic core arrangement or formed composite core 100 or any of the core portions, such as the first magnetic core 110 and/or the second magnetic core 120, can be provided with a mechanical encapsulation, beneficially a polymer layer or coating such as epoxy. This can ensure a smooth surface suitable for applying electrical windings without having to enclose the composite core 100 in a case. Avoiding a case may be suitable for minimizing the dimensions of the inductive component but also reducing the resistance of a secondary winding resulting in better electrical performance. Edges of the gap(s) of the second magnetic core 120 may need additional protection in order to provide a smooth surface of the core, for example in order to avoid damaging the electrical windings. For example, local coating or adhesive tape may be applied if necessary.
  • the first magnetic core 110 can be provided with a polymer coating, such as epoxy, in order to provide mechanical encapsulation and a smooth surface.
  • a polymer coating such as epoxy
  • the second magnetic core 120 can be provided with a polymer coating such as epoxy.
  • the polymer coating can be applied before forming the at least one non-magnetic gap 122a, 122b. Additionally or alternatively, the polymer coating can be applied after forming the at least one non-magnetic gap 122a, 122b, but before filling the at least one non-magnetic gap 122a, 122b with the adhesive or after filling the at least one non-magnetic gap 122a, 122b with the adhesive.
  • edges of the at least one non-magnetic gap 122a, 122b can be provided with an additional coating or protection layer for providing a smooth surface. For example, local coating or adhesive tapes may be applied.
  • the first magnetic core 110 and/or the second magnetic core 120 can be ring shaped.
  • ring shaped such as when referring to the shape of the first magnetic core 110 and/or the second magnetic core 120, can be understood as including shapes that deviate from a perfect ring or circle, but are still considered as being ring-like, such as e.g. an oval shape. Furthermore, also an almost rectangular shape is possible.
  • the composite core 100 also referred to as a magnetic core arrangement 100, described herein may provide practical means to engineer its electromagnetic performance depending on the DC current present in the circuit.
  • Very high inductance, very low losses, and low remanence can be provided by the first core 110, also referred to as a first core 110, under low DC current.
  • Excellent AC performance over wide current range and frequency range can then be ensured by the composite core 100.
  • Useable inductance, low losses, and very low remanence can be provided by the second core 120, also referred to as a second core 120, under excessive DC current. Acceptable AC performance can be still reached then by the composite core 100.
  • the composite core 100 described herein can provide improved means to fabricate gaps 122, 122a, 122b with small and precise width.
  • the inductance value provided under high DC currents can be thus more precise and stable.
  • the second magnetic core 120 can also provide lower losses by using tape wound cores, improved materials, and gap fabrication processes resulting in lower stresses in the core.
  • the first magnetic core 120 can be also better optimized for reaching high inductance and low losses. Furthermore, using more precise and stable fabrication can allow designing with lower tolerances allowing to better optimize the resources in order to reach higher performance and/or lower mass and cost.
  • Figs. 1A to 3B show at least one non-magnetic gap 122a, 122b that particularly extends from one end side of the second magnetic core 120 to an opposite end side of the second magnetic core 120.
  • the at least one non-magnetic gap 122a, 122b extends from one end side of the second magnetic core 120 to an opposite end side of the second magnetic core 120 in a radial direction of the second magnetic core 120, i.e. the at least one non-magnetic gap 122a, 122b spans the full extension and/or cross-section of the second magnetic core 120 in the radial direction.
  • the at least one non-magnetic gap 122a, 122b extends from one end side of the second magnetic core 120 to an opposite end side of the second magnetic core 120 in the axial direction of the second magnetic core 120, i.e. the at least one non-magnetic gap 122a, 122b spans the full extension and/or cross-section of the second magnetic core 120 in the axial direction. Accordingly, the at least one non-magnetic gap 122a, 122b may provide a complete cut through the second magnetic core 120, i.e. the at least one non-magnetic gap 122a, 122b may completely separate the material of the second magnetic core 120.

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  • Chemical & Material Sciences (AREA)
  • Composite Materials (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Coils Or Transformers For Communication (AREA)

Claims (16)

  1. Eine Magnetkernanordnung (100) für eine induktive Vorrichtung, insbesondere für einen Induktor oder einen Transformator, die Magnetkernanordnung umfassend:
    - einen ersten Magnetkern (110); und
    - einen zweiten Magnetkern (120), wobei der zweite Kern (120) mindestens einen nichtmagnetischen Spalt (122, 122a, 122b) einschließt, wobei der mindestens eine nichtmagnetische Spalt (122, 122a, 122b) teilweise oder vollständig mit einem Harz gefüllt ist,
    dadurch gekennzeichnet, dass der Spalt das Harz und einen oder mehrere feste Abstandhalter, die teilweise oder vollständig in den Spalt eingeführt sind und/oder Füllpartikel, die im Harz verteilt sind, umfasst.
  2. Die Magnetkernanordnung nach Anspruch 1, wobei der eine oder die mehreren festen Abstandhalter, nichtmagnetische feste Abstandhalter (124) sind.
  3. Die Magnetkernanordnung nach Anspruch 2, wobei die Füllpartikel Mikropartikel sind, die aus einem nicht elektrisch leitfähigen und/oder nichtmagnetischen und/oder nichtorganischen Material gefertigt sind, einschließlich Siliziumoxid, Glas, Sand, Keramik oder Zusammensetzungen daraus.
  4. Die Magnetkernanordnung nach Anspruch 2, wobei die festen Abstandhalter (124) aus einem nicht elektrisch leitfähigen und/oder nichtorganischem Material gefertigt sind und/oder sich über einen Abschnitt der Breite des Spalts erstrecken, insbesondere über mindestens 60 % der Breite des Spalts.
  5. Die Magnetkernanordnung nach einem der vorhergehenden Ansprüche, wobei die Breite des Spalts oder die Gesamtbreite mehrerer Spalte im Bereich zwischen 0,03 mm und 0,25 mm liegt.
  6. Die Magnetkernanordnung nach einem der Ansprüche 1 bis 5, wobei der nichtmagnetische Spalt (122, 122a, 122b) eine Breite von höchstens 0,35 mm, insbesondere höchstens 0,25 mm, vor allem höchstens 0,20 mm, und/oder mindestens 0,01 mm, insbesondere mindestens 0,03 mm, vor allem mindestens 0,05 mm aufweist.
  7. Die Magnetkernanordnung nach einem der Ansprüche 1 bis 5, wobei der nichtmagnetische Spalt (122, 122a, 122b) eine Breite von höchstens 0,15 mm und mindestens 0,03 mm aufweist.
  8. Die Magnetkernanordnung nach einem der Ansprüche 1 bis 7, wobei der erste Magnetkern (110) eine höhere magnetische Permeabilität und eine geringere Remanenz aufweist als der zweite Magnetkern (120).
  9. Die Magnetkernanordnung nach einem der Ansprüche 1 bis 8, wobei der erste Magnetkern (110) eine effektive relative Permeabilität von hauptsächlich mindestens 20000 und/oder höchstens 60000 aufweist und/oder eine Remanenzflussdichte, die niedriger ist, z. B. um höchstens 30 %, als eine Sättigungsflussdichte und/oder wobei der zweite Magnetkern (120) eine effektive relative Permeabilität von mindestens 400 und/oder höchstens 4000 aufweist und/oder eine magnetische Sättigungsflussdichte aufweist, die mindestens 1,5 T beträgt.
  10. Die Magnetkernanordnung nach einem der Ansprüche 1 bis 9, wobei der zweite Magnetkern (120) aus mindestens zwei Kernabschnitten oder Kernsegmenten ausgebildet ist und mindestens zwei nichtmagnetische Spalte (122) zwischen den mindestens zwei Kernabschnitten oder Segmenten aufweist.
  11. Die Magnetkernanordnung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, dass der erste Magnetkern und/oder der zweite Magnetkern als bandgewickelte Kerne ausgebildet sind.
  12. Die Magnetkernanordnung nach einem der Ansprüche 1 bis 11, wobei der erste Magnetkern (110) ringförmig ist und/oder mit einer Polymerbeschichtung, wie etwa Epoxy, versehen ist und/oder wobei der zweite Magnetkern (120) ringförmig ist und/oder mit einer Polymerbeschichtung, wie etwa Epoxy, versehen ist.
  13. Die Magnetkernanordnung nach einem der Ansprüche 1 bis 12, wobei der erste Magnetkern (110) und der zweite Magnetkern (120) etwa den gleichen Innen- und/oder Außendurchmesser aufweisen und/oder aufeinander gestapelt sind, um einen Verbundkern (100) auszubilden.
  14. Die Magnetkernanordnung nach einem der Ansprüche 1 bis 13, wobei der erste Kern (110) ein bandgewickelter Kern ist, der aus einer nanokristallinen Legierung gefertigt ist und/oder wobei der zweite Kern (120) auf einem bandgewickelten Kern basiert, der aus einem kornorientierten Elektrostahl gefertigt ist.
  15. Eine Induktive Vorrichtung, insbesondere ein Induktor oder ein Stromtransformator, umfassend mindestens eine Magnetkernanordnung (100) nach einem der Ansprüche 1 bis 14 und wobei mindestens eine elektrische Wicklung dazu konfiguriert ist, um die Magnetkernanordnung (100) herum gewickelt zu werden.
  16. Eine Installationsvorrichtung, umfassend mindestens eine induktive Vorrichtung nach Anspruch 15.
EP19779919.0A 2018-10-05 2019-10-04 Magnetkernanordnung, induktive vorrichtung und installationsvorrichtung Active EP3861562B1 (de)

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PCT/EP2019/076961 WO2020070309A1 (en) 2018-10-05 2019-10-04 Magnetic core arrangement, inductive device and installation device

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JPS58216412A (ja) * 1982-06-09 1983-12-16 San Eisha Seisakusho:Kk 広範囲非飽和変流器
US4881989A (en) 1986-12-15 1989-11-21 Hitachi Metals, Ltd. Fe-base soft magnetic alloy and method of producing same
KR20020091049A (ko) * 2000-08-24 2002-12-05 코닌클리케 필립스 일렉트로닉스 엔.브이. 실질적으로 폐쇄된 코어의 제조 방법 및 코어 및 자기 코일
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DE102011107252A1 (de) * 2011-07-14 2013-01-17 Schneider Electric Sachsenwerk Gmbh Spule zur Strombegrenzung
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