Patent ID: 12191073

DETAILED DESCRIPTION

The present disclosure provides an improved magnet device based on the Bitter principle which has a low thermal dissipation and permits a high winding current density thus making stronger magnetic fields possible.

A first embodiment of a magnet device based on the Bitter principle according to the disclosure has an arrangement which is formed from a plurality of conductor layers and a plurality of substrate layers. In this case, each substrate layer carries a conductor layer and with this takes the form of a ring. The ring has a radial slot extending through the entire ring. “Carries” means that the conductor layer is formed in two layers with the substrate layer and the more robust substrate layer forms a base for the conductor layer.

Three or more rings (preferably an even number, here in each case circular rings in the form of a flat piece between two different circles with the same center point, wherein the circle with the smaller diameter forms a central through-hole) form a spiral arrangement with a ring in each case at the beginning of the spiral arrangement (initial ring) and a ring at the end of the spiral arrangement (end ring), at least one or more rings between the initial ring and the end ring (middle rings), wherein the initial ring and the end ring with in each case one of their ends adjacent to the slot are, via a contact section, in current-conducting contact with a middle ring at its end adjacent to the slot, and wherein each middle ring with its two ends adjacent to the slot is, via a contact section, in current-conducting contact with two other rings. The spiral arrangement is preferably a helical arrangement and has a circular-cylindrical basic shape; however, other basic shapes are also possible, such as, for example, an ellipsoidal, rectangular or polygonal basic shape, the corners of which can be rounded.

In this case, the rings are arranged alternately in the arrangement, in that a ring with a downward-facing conductor layer follows a ring with an upward-facing conductor layer.

The spiral, which is formed by the arrangement of the individual current-conducting rings in the magnet device, permits continuous current transmission. In the radial direction, the rings are homogeneous and in the axial direction the rings are inhomogeneous, whereby mechanical transverse stresses are avoided. At least three rings, preferably four, five or even more such rings, which are geometrically identical and whose middle through-holes are in alignment in the spiral arrangement, are required to form them.

Because the middle through-holes are in alignment, in an assembly arrangement of the magnet device they surround a cylindrical space for experimental devices or other devices that are to be exposed to the magnetic field formed in this cylindrical space.

The device is referred to herein as a magnet device based on the Bitter principle, since it follows the Bitter principle known from the prior art. It is a layer-based principle in which plates or plate-shaped rings are assembled with intermediate layers of insulating materials to form layered magnets.

The spiral arrangement creates a magnet device with a significantly lower total resistance and losses than is the case with previously used Bitter magnets from the prior art. The magnet device based on the Bitter principle thus permits a high winding current density and stronger magnetic fields. Furthermore, the lower total resistance permits the power supply to be dimensioned smaller in terms of power than in the prior art, and the magnet device has low thermal dissipation due to the use of high-temperature superconductors.

In order to achieve continuous current transmission in the spiral arrangement, the rings are oriented alternately such that the conductor layers and the substrate layers each come into contact with one another: The initial ring begins with an orientation “conductor layer at the top” and the following middle ring continues the arrangement with an orientation “conductor layer at the bottom,” thereby enabling a very compact design. The space requirement is optimized and less or no insulating material is required overall. The good heat dissipation leads to a greater quenching reliability at high winding current densities, i.e., above 200 A/mm2, especially when high-temperature superconductors are used. Depending on the operating temperature (thus also depending on the power requirement), the cooling can be carried out with various cryogens which are economical as regards consumption, such as, for example, liquid nitrogen, liquid neon, liquid hydrogen or liquid helium. Furthermore, higher operating currents can thereby be used than in the prior art and stronger magnetic fields can thus be achieved, e.g. 3 T at 100 A/mm 2 in a volume of approx. 10 cm3.

In a further embodiment of the magnet device, two rings contacting each other overlap at the contact section. An overlap produces an improved electrical contact between two conductor layers that face each other and enables continuous current transmission in the magnet device. An insulation layer or electrically poorly conductive layer can be present in interfaces between two conductor layers lying one above the other, with the exception of the contact section. As a result, large time constants can be prevented in the event of a change in the operating current and subsequent current redistribution.

According to a further embodiment of the magnet device, a contact material is applied in a planar manner to the contact section, or to the surface between the overlapping rings. Alternatively, at the contact section the conductor layers that face each other of the two contacting rings can be sintered together. As a result, a bonded connection can be produced. Both the application of a contact material and the sintering serve to improve the electrical contact and thus improve a continuous current flow and to keep it low-loss.

In a preferred further embodiment of the magnet device, the contact material is a material which is superconducting during operation of the magnet device based on the Bitter principle. The material can be a thin layer, preferably an indium or niobium layer, for example an AgIn solder. Simple solders or solder connections can also be used, for example solders which contain lead or tin. The thin layer acts like an interposed foil, which is pressed between two rings in the finished magnet device and thus already creates a good frictional contact between the contacting ends, adjacent to the slot, of two rings.

According to a further embodiment of the magnet device, the rings have further through-holes in their annular surface. The rings are arranged one above the other in the spiral arrangement such that these further through-holes, because they are aligned with one another, form cooling channels. A further embodiment of the magnet device provides that in the spiral arrangement, spaces are provided between the rings—initial ring, end ring and one or more middle rings—except at the contact sections, in which spaces a filler material for stabilizing the spiral arrangement is arranged. The filler material is preferably an insulating or thermally conductive material. Filler material is preferably selected from a group of materials which includes wax, resin and epoxy resins. The epoxy resins can be filled, for example, with Al2O3.

Furthermore, a further embodiment of the magnet device provides that conductor layers are preferably superconductor layers which consist of superconducting material. The conductor layers are preferably high-temperature superconductor layers which have 2G high-temperature superconductors. Preferably RE-123 is used, where RE stands for Rare Earth and refers to rare earths with the exception of praseodymium. This superconductor achieves high current densities, a high upper critical magnetic field and a wide temperature use range with at the same time anisotropic behavior and crystal structure. The superconducting materials are embedded in a specific layer structure and form a coated conductor. This structure begins with a metal substrate in the form of a carrier strip, to which a ceramic buffer layer is applied and onto which the actual superconductor is deposited. By means of a protective layer, the superconductor is protected from damage or the electrical contact is simplified.

The use of high-temperature superconductors results in no ohmic losses, relative to the main path of the current. Any normal-conducting electrical contacts that are used for supplying power to the initial and end rings and that are necessary so that the magnet device can be connected to a power source are excluded. Furthermore, normal-conducting transition contacts, for example made of an AgIn solder, can be provided between the rings.

Furthermore, a crystallographic C-axis of the high-temperature superconductor layer is oriented parallel to a longitudinal axis of the spiral arrangement. The orientation of the high-temperature superconductor layer has the consequence that, in the radial direction, material and thermal expansion coefficients are homogeneous and constant for a constant axial position, so that transverse stresses and shear stresses are prevented and degradation problems are avoided.

According to yet another embodiment of the magnet device, the cooling channels extend through the filler material. The magnetic device is cooled with a cryogen, for example with liquid nitrogen (LN2), liquid neon (LNe), liquid hydrogen (LH2) or liquid helium (LHe), so that the conductor layer, if made of a superconducting material, can be put into the superconducting state. This cryogen can flow through the cooling channels and thus cool the magnet device not only from the outside, but also easily reach inner regions, depending on the dimensions of the magnet device.

In a further embodiment of the magnet device, the substrate layers consist of stainless steel, nickel, a nickel alloy or highly corrosion-resistant nickel-molybdenum alloys (Hastelloy®). The insulation materials are preferably made of Kapton, PEEK and polyimides.

According to yet another embodiment, the magnet device provides that the initial ring and the end ring are connected to an electrical contact device at their ends which are not in current-conducting contact with a middle ring. Additionally or alternatively, the electrical contact device can have a persistent-mode bridge. With the persistent-mode bridge, the magnet in its excited state can be disconnected from the power source.

By selection of a corresponding number of rings and different dimensions of the rings, the magnet device is advantageously scalable to the respective desired operating current and magnetic field generation. The rings can be produced in different sizes in order to generate the desired magnetic field flux density for different applications. Dimensions are thus possible whereby the smallest dimension of the inner through-opening is less than the radial dimension of the rings, or the dimension of the inner through-opening is three times as large as the radial dimension of the rings. The magnet device can be used in a rotor or stator in a rotor-stator arrangement of an electric machine.

Other embodiments of the magnet device based on the Bitter principle as well as some of the advantages associated with these and other embodiments will be become clear and more understandable through the following detailed description with reference to the accompanying figures. Objects or parts thereof which are substantially the same or similar can be provided with the same reference numerals. The figures are merely schematic representations of embodiments of the disclosure.

FIG.1andFIG.5show a magnet device1based on the Bitter principle, which is constructed from a plurality of rings4. Each ring4, asFIG.2also shows, is constructed from two layers: a conductor layer2and a substrate layer3. Each ring4has a circular geometry with a central through-hole44, wherein each ring4has a radial slot5, which extends through the entire ring4, namely starting from the outer circular ring, which describes the circumference, to the inner circular ring, which delimits the through-hole44in the center of the ring4. The ends51,52of the ring4adjoin the slot5. These ends51,52serve as contact points between the conductor layers2of two rings4arranged one above the other.

InFIG.3it is shown how the rings4are placed one on top of the other in such a way that they form a spiral arrangement, as shown inFIG.1. Here each ring4is arranged on its adjacent ring4in such a way that a ring4with an upward-facing conductor layer2adjoins a ring4with a downward-facing conductor layer2. The structure here provides that the conductor layer2of the initial ring41faces downwards in the figure and the middle ring43following it is offset by an offset in a rotationally symmetrical manner and is arranged with its downward-facing conductor layer2on the initial ring41.

The initial ring41and the subsequent middle ring43have an overlap which forms a contact section A and which in its dimension corresponds to the offset. InFIG.4, a contact material6is shown in the gap that is provided between the contacting annular surfaces. In this contact section A, the two conductor layers2of the two adjacent rings41,43are in electrical contact, so that a continuous current can flow in the magnet device1when current is applied to the magnet device1. The contact material6can be a thin metallic layer. Alternatively, the conductor layers2of the two adjacent rings41,43can be sintered together in the contact section A in order to produce a good electrical contact.

Between the substrate layers3of the initial ring41and of the middle ring43, an insulating layer10is introduced (seeFIGS.1and3). It serves to electrically separate the two rings41,43from each other and to avoid current redistribution currents. In the contact section A, one end52of the initial ring41rests on the other end51of the middle ring43. This is repeated with the next middle ring43, the one end of which now rests on one end of the ring43and thus overlaps in the contact section A there. Due to the rotationally symmetrical offset of the individual rings41,42,43, a spiral-shaped arrangement is formed. In this case, the rings41,42,43are arranged relative to one another in such a way that the odd-numbered rings41,42,43face upwards with their conductor layer2and the even-numbered rings42,43face upwards with their substrate layer3.

The magnet device1is terminated by an end ring42which is arranged such that inFIG.1its substrate layer3faces upwards.

FIG.4shows how the individual layers of the individual rings41,42,43are placed one above another. Thus, the overlap in the contact section A is again clearly shown here, in which the intermediate contact material6is present in order to improve the electrical contact between the contacting conductor layers2. In order to impart stability to the magnetic device1, a filler material7, such as, for example, an epoxy resin, is provided between the sections of the rings41,42,43which are not in contact with each other. InFIG.5the layering of the rings41,42,43of the magnet device1together with the filler material7is shown.

In order to supply current to the magnet device1, electrical terminals11are arranged at one end51of the initial ring41and at the end52of the end ring42, asFIG.1shows. In this way, the spiral arrangement of the magnet device1can be connected to a current-supplying source or a persistent-mode bridge and can produce continuous current operation.

While subject matter of the present disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. Any statement made herein characterizing the invention is also to be considered illustrative or exemplary and not restrictive as the invention is defined by the claims. It will be understood that changes and modifications may be made, by those of ordinary skill in the art, within the scope of the following claims, which may include any combination of features from different embodiments described above.

The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.

LIST OF REFERENCE SIGNS

1Magnet device2Conductor layer3Substrate layer4Ring41Initial ring42End ring43Middle ring44Central through-hole5Slot51End adjacent to slot52End adjacent to slot6Contact material7Filler material8Through-holes9Cooling channels10Insulation layer11Electrical contact device