Cooling system for a rotor, rotor and electric machine
The cooling system for superconducting rotors addresses inefficiencies by using a vacuum chamber and refrigerant channel to minimize heat input and maintain temperature independence, improving cooling efficiency and connection options.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- KARLSRUHER INST FUR TECH
- Filing Date
- 2025-12-17
- Publication Date
- 2026-06-25
Smart Images
Figure EP2025087670_25062026_PF_FP_ABST
Abstract
Description
[0001] Karlsruhe Institute of Technology, December 17, 2025
[0002] KIT17219PC / ST / PF / PF
[0003] Cooling system for a rotor, rotor and electric machine
[0004] Technical field
[0005] The present invention relates to a cooling system for a rotor. The present invention further relates to a rotor with a cooling system. The present invention further relates to an electric machine.
[0006] Technical background
[0007] Various rotating electric machines with superconducting rotors and cooling systems for such machines are known from the prior art. These types of electric machines are used particularly, but not exclusively, in wind turbines and as propulsion motors for ships, trucks, aircraft, etc.
[0008] Wind power generation is becoming increasingly important, particularly for the German electricity grid. To adapt to wind conditions, wind turbines require a pitch adjustment (blade angle adjustment) of their typically three blades. This adjustment can be achieved either electrically or hydraulically via appropriate control lines and cross-sections. These lines must be routed within the central shaft from the stationary control instrumentation to the front hub and the rotating blades.
[0009] For "cryogenic rotors," cooling can be achieved either via rotating cold heads or by supplying a cryogenic refrigerant. Both require a central supply to the rotor. DE 100 39 964 A1 describes a superconducting device with a cooling unit for cooling a rotating superconducting winding. The superconducting device includes a rotor rotatable about an axis of rotation, with a superconducting winding in a thermally conductive winding carrier. The winding carrier has a central, cylindrical cavity. A cold head of a cooling unit, located outside the rotor, is thermally connected to a heat transfer element that projects into the cavity of the winding carrier. An annular gap between the winding carrier and the heat transfer element is filled with a thermally conductive contact gas.
[0010] DE 102 11 363 A1 describes a superconducting device with a cold head of a refrigeration unit thermally coupled to a rotating, superconducting winding, operating with a thermosiphon effect. The superconducting device comprises a rotor rotatable about an axis of rotation, with a superconducting winding in a thermally conductive winding carrier. This winding carrier has a central refrigerant cavity to which a lateral cavity extending from the winding carrier is connected. Outside the rotor, a cold head of a refrigeration unit is connected to a condenser unit for condensing the refrigerant. A stationary heat pipe carrying the refrigerant is coupled to the condenser unit, projects axially into the co-rotating lateral cavity, and is sealed against this cavity. The refrigerant is intended to be a mixture of several components with different condensation temperatures.
[0011] DE 103 21 463 A1 describes a superconducting machine with a superconducting winding and thermosiphon cooling. The machine comprises a rotor rotatable about an axis, the superconducting winding of which is thermally coupled to a central refrigerant cavity. This cavity, together with laterally connected pipe sections and a condenser chamber of a refrigeration unit located outside the machine, forms a single-pipe system in which a refrigerant circulates due to a thermosiphon effect. To maintain the supply of refrigerant to the central cavity even when the rotor is tilted, pressure boosting devices are provided. These devices generate pressure pulses of gaseous refrigerant acting on the liquid refrigerant in the condenser chamber or the adjoining pipe sections.
[0012] DE 103 58 341 B4 describes a device for supporting a coolant supply, in particular long coolant supplies for superconducting machines, comprising a hollow shaft which can be connected to the superconducting machine in a first section and in whose interior the coolant supply is arranged for conveying coolant from the refrigeration unit to the superconducting machine. The coolant supply can be connected to the refrigeration unit in a second section of the hollow shaft and is thus fixed within it. A magnetic bearing is provided in the first section of the hollow shaft, arranged such that a radial and thus centering force is exerted on the coolant supply.
[0013] DE 103 61 885 B3 describes a refrigeration system with a condenser having a connection surface for a cold head. In the refrigeration system, an application to be cooled within an evacuated workspace is cooled via a piping system. The refrigerant conducts the heat away via a condenser, which is connected to a cold head (not shown). To enable easy replacement of the cold head, the condenser is mounted in an elastic suspension according to the invention. The movement of the condenser towards the partition wall resulting from the elasticity of the suspension is limited by a stop device and, optionally, away from the partition wall by an additional stop. This advantageously protects the refrigeration system from damage when replacing the cold head, as the condenser is supported in a groove in the partition wall by the stop device during installation of the cold head.
[0014] German patent DE 10 2004 040 493 A1 describes a machine with a superconducting excitation winding with thermosiphon cooling and a method for cooling the winding. The machine comprises a rotor whose superconducting excitation winding is thermally coupled to a central refrigerant cavity. This rotor cavity, together with an external condenser chamber of a refrigeration unit and connecting pipe sections, forms a closed, single-pipe system in which a refrigerant circulates due to a thermosiphon effect.To maintain a supply of refrigerant to the rotor cavity even when the rotor is tilted, the following shall be provided: a cold buffer volume integrated into the piping sections and filled with liquid refrigerant; a warm buffer volume filled with gaseous refrigerant under overpressure, which is connected to the condenser chamber or the piping sections via a controllable valve; a brief pumping action on the liquid refrigerant towards the rotor cavity by means of pressure pulses on the gaseous refrigerant by means of a corresponding opening of the controllable valve; and also a temporary increase in the temperature in the piping system after the pumping action to a predetermined temperature level above the normal operating temperature.
[0015] DE 10 2005 002 361 B3 describes a refrigeration system for a superconducting device with multiple cold heads. The refrigeration system for a superconducting device comprises a closed piping system with condenser chambers, multiple cold heads, a refrigerant working volume of the device, and connecting piping sections. A refrigerant circulates in the piping system, utilizing a thermosiphon effect. A refrigerant collection chamber is integrated into the piping system to act as a phase separator. The piping sections between each condenser chamber and the refrigerant collection chamber form a single-pipe thermosiphon system, while the piping sections between the refrigerant collection chamber and the refrigerant working volume form a two-pipe thermosiphon system. The refrigerant collection chamber is located at a sufficiently high geodetic elevation. The refrigeration system is suitable for operation in fluctuating environments.
[0016] DE 102014212 166 A1 describes a cooling device for cooling an electric machine with a rotor rotatably mounted about an axis of rotation and arranged on a central rotor shaft. The cooling device comprises at least one stationary condenser chamber, which is in thermal contact with at least one stationary cold head, and at least one first coolant chamber arranged on the rotor, wherein the first coolant chamber surrounds the central rotor shaft in an annular manner and has an axial boundary wall provided with an annular gap for the supply and / or discharge of coolant. Furthermore, an electric machine with a rotor rotatably mounted about an axis of rotation and arranged on a central rotor shaft, and such a cooling device, is described.
[0017] DE 102014212 167 A1 describes a cooling device for cooling an electric machine with a rotor rotatably mounted about an axis of rotation and arranged on a central rotor shaft. The cooling device comprises at least one stationary condenser chamber, which is in thermal contact with at least one stationary cold head, and at least one first coolant channel arranged on the rotor. The first coolant channel is fluidically connected to the condenser chamber via at least one opening in an outer wall of the rotor shaft, and the rotor shaft is provided internally with at least one conveying vane for conveying coolant from a region of the condenser chamber towards the first coolant channel. Furthermore, an electric machine with a rotor rotatably mounted about an axis of rotation and arranged on a central rotor shaft, and such a cooling device, is described.
[0018] DE 102014215 649 describes a cooling device for cooling an electric machine with a rotor rotatably mounted about an axis of rotation and arranged on a central rotor shaft. The cooling device comprises at least one thermal coupling element arranged on the rotatable rotor shaft for transferring heat from a radially inner region to a radially outer region. The thermal coupling element is immersed, at least in a partial region of its circumference, in a stationary reservoir containing a condensed first coolant. Furthermore, an electric machine with a rotor rotatably mounted about an axis of rotation and arranged on a central rotor shaft, and such a cooling device, is described.
[0019] Despite the numerous advantages of existing rotating electric machines and cooling systems, there is still room for improvement. A particular challenge with rotating machines featuring a superconducting rotor is that only one shaft end is available for various tasks or interfaces, such as coolant inlet / outlet, electrical connections for rotor excitation, bushings through the entire shaft, etc. The other shaft end is typically occupied by torque transmission. Current connections for cryogenic cooling require a central pipe with multiple connections, either for working gases at different pressures or for coolant and coolant gas, usually from the non-drive end.While the aforementioned approaches can generally make the second shaft end available for purposes other than coolant transfer, this is only possible by accepting temperature gradients due to solid-state heat conduction and / or additional heat input from the kinetic energy of the supplied coolant or cryogen. For example, in "cryogenic rotors," such a central feedthrough must, according to current technology, traverse the central space. This entails several hot-cold transitions, the heat input from which through the feedthroughs is usually unacceptable.
[0020] Theoretically, electrical control lines could be routed not inside the central shaft, but across the outer surfaces of the (cold) rotor. However, due to the greater line lengths and especially the confined space within the machine's air gap, this approach proves impractical.
[0021] For motors / generators, the concept of a neon thermosiphon for cooling the rotor has been extensively developed and demonstrated, albeit without the need for the implemented pitch control. The "off-axis cooling concepts" described for specific applications in DE 10 2014 212 166 Al, DE 10 2014 212 167 Al and DE 10 2014 215 649 Al share the common feature that the cooling capacity of the neon thermosiphon is significantly reduced by additional energy inputs and heat transfer surfaces.
[0022] Object of the invention
[0023] It would therefore be desirable to provide a cooling system for a rotor and an electric machine that largely avoids the disadvantages of known cooling systems, rotors, and electric machines. In particular, the connection options should be improved or expanded while simultaneously increasing cooling efficiency. A solution should be provided that avoids multiple penetrations of the cold space and does not interfere with the rotor's cooling supply.
[0024] General description of the invention
[0025] This problem is addressed by a cooling system for a rotor, a rotor and an electric machine with the features of the independent claims. Advantageous embodiments, which can be implemented individually or in any combination, are described in the dependent claims.
[0026] In the following, the terms "have," "exhibit," "comprise," or "include," or any grammatical variations thereof, are used in a non-exclusive manner. Accordingly, these terms can refer both to situations in which, apart from the features introduced by these terms, no other features are present, and to situations in which one or more additional features are present. For example, the expression "A has B," "A exhibits B," "A comprises B," or "A includes B" can refer both to the situation in which, apart from B, no other element is present in A (i.e., a situation in which A consists solely of B) and to the situation in which, in addition to B, one or more other elements are present in A, such as element C, elements C and D, or even further elements.
[0027] Furthermore, it should be noted that the terms "at least one" and "one or more," as well as grammatical variations of these terms, when used in connection with one or more elements or features and intended to express that the element or feature may be present once or multiple times, are generally used only once, for example, when the feature or element is first introduced. Upon subsequent mention of the feature or element, the corresponding term "at least one" or "one or more" is generally no longer used, without restricting the possibility that the feature or element may be present once or multiple times.
[0028] Furthermore, the terms "preferably," "in particular," "for example," or similar terms are used in the following text in connection with optional features without limiting alternative embodiments. Features introduced by these terms are optional features, and it is not intended that these features limit the scope of protection of the claims, and in particular the independent claims. As the person skilled in the art will recognize, the invention can also be implemented using other embodiments. Similarly, features introduced by "in one embodiment of the invention" or by "in an exemplary embodiment of the invention" are understood as optional features without limiting alternative embodiments or the scope of protection of the independent claims.Furthermore, these introductory expressions are intended to leave all possibilities of combining the features introduced herein with other features, whether optional or non-optional features, unaffected.
[0029] Furthermore, the terms "first", "second" or similar terms are used solely to distinguish between different components and are not intended to indicate any particular order or weighting of their importance.
[0030] In a first aspect of the present invention, a cooling system for a rotor is proposed.
[0031] The cooling system comprises a first vacuum chamber. This first vacuum chamber is designed to be rotatably arranged relative to a central shaft and is subjected to a vacuum below atmospheric pressure. In other words, the first vacuum chamber is designed such that it can be rotatably arranged relative to a central shaft. Electrical coils are arranged within this first vacuum chamber. In the assembled state, the coils are arranged coaxially to the central shaft. The vacuum chamber, being under negative pressure, allows for the housing of the coils. The negative pressure or vacuum in the first vacuum chamber provides thermal insulation, enabling effective cooling of the coils.
[0032] The cooling system also includes a refrigerant reservoir. The refrigerant reservoir is located in the first vacuum chamber and is rotatable. In the assembled state, the refrigerant reservoir is rotatable, particularly relative to the central shaft. The refrigerant reservoir is thermally connected to the coils.
[0033] The placement of the refrigerant reservoir in the first vacuum chamber prevents or minimizes heating of the refrigerant within the reservoir. Furthermore, its position in the first vacuum chamber places it as close as possible to the coils, thus minimizing the thermally conductive connection between the refrigerant reservoir and the coils, thereby also preventing or minimizing heating of the refrigerant.
[0034] The negative pressure or vacuum in the first vacuum chamber provides thermal insulation, allowing the coils to be cooled effectively. In particular, the negative pressure or vacuum in the first vacuum chamber prevents a temperature increase of the refrigerant or cryogen in the refrigerant reservoir and the thermally conductive connection between the refrigerant reservoir and the coils.
[0035] The cooling system further comprises a housing with a cylindrical housing projection. The housing has a refrigerant inlet, a refrigerant channel, and a refrigerant outlet. The refrigerant inlet and outlet are formed within the housing. The refrigerant outlet is fluidly connected to the refrigerant reservoir and, in particular, is gas-permeable. The housing projection is designed such that, in the assembled state, it projects coaxially from the housing to the central shaft and is located section by section between the central shaft and the first vacuum chamber. The refrigerant inlet is fluidly connected to the refrigerant channel. The refrigerant channel extends section by section in a curved shape into the refrigerant reservoir.
[0036] In its assembled state, the refrigerant channel can extend in a spiral shape around the central shaft into the refrigerant reservoir. The refrigerant inlet allows connection to a refrigeration system, thus enabling the supply of refrigerant to the channel and through it into the reservoir. Gaseous refrigerant can be returned to the refrigeration system and its condenser via the refrigerant outlet. The arrangement of the housing projection between the central shaft and the first vacuum chamber provides thermal insulation from the central shaft and allows the first vacuum chamber to rotate freely on the housing projection. This ensures that the rotational speed of the central shaft and the outer rotor components, such as the first vacuum chamber and coils, is independent of the rotational speed.The segmented, egg-shaped refrigerant channel allows for a greater degree of tilting of the cooling system due to the larger radial distance between the refrigerant inlet and outlet coordinates. Furthermore, it enables temperature independence for the rotating components—the central shaft and the rotor outer component(s), such as the first vacuum chamber and coils. This eliminates temperature differences via solid-state heat conduction to the refrigerant reservoir. However, it is emphasized that the central shaft itself does not necessarily have to be rotatable.
[0037] The central shaft can be a solid shaft or a hollow shaft. It can be rotatable about an axis of rotation. Unlike a solid shaft, the central shaft can alternatively be hollow. This leaves the inner area of the central shaft free for various applications. Furthermore, the invention even allows for a certain degree of inclination of the central shaft's axis of rotation. The central, continuous shaft can operate at a different temperature than the refrigerant or cryogen. The central shaft can be part of a pitch tube system in a wind turbine.
[0038] Preferably, the first vacuum chamber borders the housing projection. For example, the first vacuum chamber borders the housing projection in the axial direction with respect to the axis of rotation. This minimizes the effort required to provide gas-tight bearings.
[0039] Overall, the cooling system allows a warm central shaft to pass through a cold section of a rotor. The presented novel cooling system concept avoids multiple hot-cold transitions and the associated heat input. The cooling system comprises a complex system of multiple nested compartments for the refrigerant, vacuum, and components of an electric machine, such as a wind turbine. The concept generally allows for three different rotational speeds of the functional compartments.
[0040] The refrigerant reservoir, when assembled, can rotate together with the first vacuum chamber relative to the central shaft and the housing projection. This allows the refrigerant reservoir and the first vacuum chamber to rotate together at the same speed.
[0041] The central shaft can be rotatably mounted in the housing projection. This allows the housing and the housing projection to be stationary or immovable, while the central shaft can rotate freely and securely within the housing projection.
[0042] The housing can be fixed at the housing projection. This allows for connection to a refrigeration system, and other components such as the first vacuum chamber and the central shaft can be rotatably mounted on the housing projection.
[0043] The first vacuum chamber can be rotatably mounted on the housing projection. This allows the first vacuum chamber to rotate and thus transmit the rotational motion for energy transfer.
[0044] The first vacuum chamber can be rotatably mounted on the housing projection using gas-tight bearings. This special arrangement of sealing bearings for the first vacuum chamber allows for independent rotational speeds of the rotating components. Furthermore, it reliably prevents the escape of gaseous refrigerant. This achieves a complex interplay of numerous bearings, which advantageously do not have to bear large rotating loads. These loads are borne by the torque transmission element of the active rotor components. The interior of the central shaft remains available for any purpose, even at room temperature.
[0045] Gas-tight bearings are preferably ferrofluid-sealing bearings. Such bearings exhibit a particularly good sealing effect against gaseous refrigerants.
[0046] The ferrofluid-sealing bearings can have an inner ring, an outer ring, at least one rolling element, and a receiving area filled with a ferrofluid. The inner ring can be arranged on the housing projection. In particular, the inner ring can be positively engaged with the surrounding surface of the housing projection. The outer ring can be arranged on the first vacuum chamber. In particular, the outer ring can be positively engaged with the surrounding surface of the first vacuum chamber. The rolling element(s) can be movably mounted between the inner ring and the outer ring. This allows the ferrofluid-sealing bearings to be particularly well adapted to the conditions of the housing projection and the first vacuum chamber. The receiving area can be arranged on at least one axial side of the ferrofluid-sealing bearing. This creates a seal against an axial outer surface.
[0047] The refrigerant reservoir can be hollow and cylindrical. This makes the refrigerant reservoir particularly suitable for the temporary storage of liquid refrigerant or cryogen.
[0048] When assembled, the refrigerant channel cannot extend more than 180° around the central shaft in any circumferential direction. This ensures that liquid refrigerant reaches the refrigerant reservoir even if the central shaft's axis of rotation is tilted.
[0049] An annular space can be formed in the housing projection. The refrigerant outlet can be fluidly connected to the refrigerant reservoir via this annular space, and in particular, it can be gas-permeable. This allows gaseous refrigerant to be discharged from the refrigerant reservoir to the refrigerant outlet. From there, the gaseous refrigerant can then be fed back into a refrigeration system.
[0050] The refrigerant channel can be located at least partially within the annular space. This means the refrigerant channel is partially in a cold environment, which prevents or minimizes the warming of the refrigerant within the channel.
[0051] The refrigerant channel can extend through the annular space. This means the refrigerant channel is located in a cold environment, which effectively prevents or minimizes warming of the refrigerant within the channel.
[0052] The housing can have a second vacuum chamber. This second vacuum chamber can be located in the housing projection. The second vacuum chamber can be pressurized to a lower pressure than atmospheric conditions. Providing an additional vacuum chamber in the housing projection improves the thermal insulation properties. In particular, it minimizes or prevents the heating of refrigerant in the refrigerant channel and the annular space.
[0053] The second vacuum chamber can coaxially surround the annular space. This minimizes or prevents the heating of refrigerant within the annular space. The second vacuum chamber can surround the annular space on a radially inner side and a radially outer side relative to the axis of rotation. In other words, the second vacuum chamber can be double-ring shaped. This minimizes or prevents the heating of refrigerant within the annular space, potentially caused by higher temperatures emanating from the central shaft.
[0054] The refrigerant reservoir can be in contact with the coils. Alternatively, the refrigerant reservoir can be thermally connected to the coils via a cooling bus.
[0055] The coils can be superconducting coils. This creates a cooling system for parts of a superconducting rotor.
[0056] In a further aspect of the present invention, a rotor is proposed. The rotor comprises a cooling system according to one of the embodiments described above or below. The rotor further comprises electrical coils. The coils are arranged in the first vacuum chamber. The rotor further comprises a central shaft.
[0057] Thus, the rotor exhibits particularly good cooling efficiency.
[0058] The central shaft can be made from a solid material. Preferably, the central shaft is designed as a hollow shaft. If the central shaft is a hollow shaft, the rotor also allows for an increase in connection options by routing cables or the like through the central shaft.
[0059] The rotor can also include a torque transmission element. This torque transmission element can be located inside a wall of the first vacuum chamber. This allows the rotational motion of the drive flange, for example, of the gearbox of a wind turbine, to be transmitted to the wall of the first vacuum chamber and then to the coil system of the rotor. The torque transmission element can also be an integral part of the wall of the first vacuum chamber.
[0060] In a further aspect of the present invention, an electric machine is proposed. The electric machine comprises a rotor according to one of the embodiments described above or below. The electric machine further comprises a stator. Thus, the electric machine exhibits particularly good cooling efficiency while simultaneously increasing the connection options by routing cables or the like through the central shaft.
[0061] The electric machine can also include a refrigeration system. The refrigeration system can be fluid-connected via the refrigerant inlet and outlet. This ensures a reliable supply of refrigerant or cryogen to the electric machine.
[0062] The refrigeration system can be designed to supply refrigerant at a temperature below the transition temperature of a material used in the electrical coils. This allows for superconducting operation.
[0063] The term "cooling system," as used here, is a broad term and should be understood in its usual and common sense, as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. Without limitation, the term can refer in particular to a system through which a refrigerant supplied by a refrigeration system flows or is transported to a location to be cooled. Accordingly, the term refers to components that can be connected to a refrigeration system and allow the transport of a refrigerant, such as, in particular, pipes and ducts. Furthermore, the term includes components that provide temporary storage for the refrigerant during its transport from the refrigeration system to the location to be cooled and vice versa.
[0064] The term "rotor," as used here, is a broad term to which its ordinary and common meaning, as understood by those skilled in the art, should be attributed. The term is not limited to any specific or adapted meaning. Without limitation, the term can refer in particular to a rotating part of a machine or assembly. Specifically, the term "rotor" is used when a stator is also present. In rotating electrical machines, the entire rotating part of the machine is referred to as the rotor.
[0065] The term "central shaft," as used here, is a broad term to which its ordinary and common meaning, as understood by those skilled in the art, should be attributed. The term is not limited to any specific or adapted meaning. Without limitation, the term can refer in particular to a rotating, elongated machine element, usually with circular cross-sections, that serves to transmit rotary motion and torque. A shaft or central shaft is designed to transmit torque. Such a shaft is connected to the machine frame via at least two rotary bearings. During the transmission of torque, the shaft is subjected to torsional stress.
[0066] The term "hollow shaft," as used here, is a broad term to which its ordinary and common meaning, as understood by those skilled in the art, should be attributed. The term is not limited to any specific or adapted meaning. Without limitation, the term can refer in particular to a rotating, elongated machine element, usually with circular cross-sections, that serves to transmit rotary motion and torque. In contrast to a conventional shaft, a hollow shaft is not made of solid material but is hollow inside, similar to a hose. A shaft, or central shaft, is designed to transmit torque. Such a shaft is connected to the machine frame via at least two rotary bearings. During the transmission of torque, the shaft is subjected to torsional stress.
[0067] The term "vacuum space," as used here, is a broad term to which its ordinary and common meaning, as understood by those skilled in the art, should be attributed. The term is not limited to any specific or adapted meaning. Without restriction, the term can refer in particular to a space in which, relative to atmospheric conditions, there is a low pressure and, as far as technically possible, a vacuum. In technical practice, a vacuum is a space with a near absence of matter. In a vacuum, there are no solid objects or liquids, only extremely little gas and thus an extremely low gas pressure. A technical vacuum is created by removing (gas) molecules from a container with a pump; the pressure inside decreases (gas pressure arises from collisions of the gas molecules against the container wall). The pumping creates a low pressure, i.e., a pressure that is lower than the ambient pressure.If the pressure in the container drops below 300 mbar and molecules are gradually removed from the space, a rough vacuum, fine vacuum, high vacuum, and finally ultra-high vacuum are obtained in succession. Creating a vacuum is also called "evacuum," and breaking it is called "vacuum removal." According to DIN 28400 Part 1 (May 1990), a vacuum is the state of a gas when the pressure of the gas, and thus the particle number density, is lower in a container than outside, or when the pressure of the gas is lower than 300 mbar, i.e., lower than the lowest atmospheric pressure found on the Earth's surface. The term "electrical coil," as used here, is a broad term and should be understood according to its usual and common meaning as understood by those skilled in the art. The term is not limited to a specific or adapted meaning.The term can refer, without limitation, to windings and wound components suitable for generating or detecting a magnetic field. These are electrical components or parts of a device, such as a transformer, relay, electric motor, loudspeaker, or electromagnet. On the other hand, the term also refers to separate coils, which are inductive passive components whose essential property is a defined inductance. They are predominantly used in signal processing for frequency-determining circuits, e.g., in LC resonant circuits, low-pass filters, high-pass filters, band-pass filters, for signal phase correction, interference suppression, current flow smoothing, or as energy storage devices in switched-mode power supplies and many other electrical and electronic devices. See also choke (electrical engineering).However, inductors are used much less frequently than resistors and capacitors, as these are often cheaper and easier to manufacture and can also be integrated more cheaply into electronic semiconductor circuits. Most inductors consist of at least one winding of a conductor made of wire, enameled copper wire, silver-plated copper wire, or high-frequency litz wire, which is usually wound on a coil former and predominantly fitted with a soft magnetic core. The winding arrangement and shape, the wire diameter, the winding material, and the core material determine the inductance and the coil's quality factor. Furthermore, spirally arranged conductor tracks on printed circuit boards, which may be surrounded by ferrite cores, are also considered "coils" in the sense of inductive passive components.The windings of a coil must always be insulated from each other and from the often electrically conductive coil core to prevent a short circuit, which would significantly impair the coil's function. In coils and transformers with multiple layers or windings made of enameled copper wire, the individual layers or windings are often additionally insulated against voltage breakdown, for example, with enameled paper, when voltage differences exceed approximately 50 volts. In a preferred embodiment, the electrical coils are superconducting. Superconductors are materials whose electrical resistance becomes practically zero when the so-called critical temperature is reached.
[0068] When using superconducting wires, wire-to-wire insulation may be omitted. The term "refrigerant reservoir," as used here, is a broad term and should be interpreted in its usual and common sense, as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. Without limitation, the term can refer in particular to any container designed for storing, and especially temporarily storing or preserving, liquid refrigerant.
[0069] The term "thermally conductive connection," as used here, is a broad term and should be understood in its usual and common sense, as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. Without restriction, the term can refer in particular to a connection that allows heat conduction between two different components.
[0070] The term "egg-shaped," as used here, is a broad term to which its ordinary and common meaning, as understood by those skilled in the art, should be attributed. The term is not limited to any specific or adapted meaning. Without restriction, the term can refer in particular to a shape in the form of a curve that winds around the surface of a cylinder with a constant slope. This shape is also called helical.
[0071] The term "section-wise curved," as used here, is a broad term to which its ordinary and common meaning, as understood by those skilled in the art, should be attributed. The term is not limited to any specific or adapted meaning. Without limitation, the term can refer in particular to a design in the form of a curve that winds around the surface of a cylinder with a constant slope, but does not complete a full revolution or circumferential extension around the cylinder axis.
[0072] The term "gas," as used here, is a broad term and should be understood in its usual and common sense, as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. Without restriction, the term can refer in particular to a refrigerant in a gaseous state.
[0073] The term "cold gas," as used here, is a broad term and should be understood in its usual and common sense, as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. Without limitation, the term can refer in particular to a refrigerant in a gaseous state having a temperature of -70°C or lower.
[0074] The term "gas-tight bearing," as used here, is a broad term and should be understood in its usual and common sense, as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. Without limitation, the term can refer in particular to a bearing that provides a seal against gas, and especially gaseous refrigerants.
[0075] The term "ferrofluid," as used here, is a broad term and should be understood according to its usual and common meaning, as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. Without limitation, the term can refer in particular to a fluid that reacts to magnetic fields without solidifying. It consists of magnetic particles a few nanometers in size, colloidally suspended in a carrier fluid. The particles are typically stabilized with a polymeric surface coating. True ferrofluids are stable dispersions, meaning that the solid particles do not settle over time and do not adhere to one another, even in extremely strong magnetic fields, or separate from the fluid as a distinct phase. Ferrofluids are superparamagnetic and exhibit very low hysteresis.The particles are usually made of iron, magnetite, or cobalt and are smaller than a magnetic domain, typically 5–10 nm (nanometers) in diameter. The surrounding fluid is usually oil or water, less often wax. Surfactants are added to stabilize the suspension by causing the particles bound in micelles to repel each other due to steric interactions. In a magnetic field, the magnetic moments of the magnetofluid particles tend to be deflected toward the field, thus acquiring macroscopic magnetization. However, the random motion of the particles still outweighs the force that pulls them together; they do not form chains, their viscosity hardly changes, but they tend to remain in strong magnetic fields. Ferrofluids are used in loudspeakers to dissipate heat between the voice coil and the magnet assembly and to passively dampen the movement of the diaphragm.They are positioned where the air gap around the voice coil would normally be and are held there by the field of the permanent magnet. Similarly, they are used to form liquid (and therefore wear-free, low-friction) seals around rotating shafts through walls. These seals are used for shaft penetrations in vacuum chambers or cleanrooms, for example, in a hard drive. Water-based ferrofluid is used for density separation. This involves generating an additional pressure using a magnetic field gradient, which can also be used to make high-density bodies float.
[0076] The term "ferrofluid-sealing bearing," as used here, is a broad term and should be interpreted according to its usual and common meaning, as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. Without limitation, the term can refer in particular to a bearing whose sealing effect is based on the presence of a ferrofluid. These seals are used for shaft penetrations in vacuum chambers or cleanrooms, for example, in a hard drive. Water-based ferrofluid is used for density separation. In this process, an additional pressure is generated using a magnetic field gradient, which can also be used to make high-density bodies float.
[0077] The term "refrigerated bus," as used here, is a broad term to which its ordinary and common meaning, as understood by those skilled in the art, should be attributed. The term is not limited to any specific or adapted meaning. Without limitation, the term can refer in particular to a system for heat transfer between several components via a common transmission path. The refrigerated bus can be made of a highly thermally conductive material, such as a metal, for example, (high-purity) copper. The refrigerated bus can, in particular, be designed in the form of one or more thermally conductive rails. The rails can, in particular, radiate from a common point or center. Each rail can thermally contact an electrical coil.
[0078] The term "torque transmission element," as used here, is a broad term and should be understood in its usual and common sense, as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. Without limitation, the term can refer in particular to a component designed to transmit torque to another component. The torque transmission element can, in particular, be flange-shaped and be connected to another component by frictional and / or positive locking. Advantageously, the torque transmission element is at least partially made of a fiber-reinforced composite material to minimize heat input, even at high torques.
[0079] The term "transition temperature," as used here, is a broad term to which its ordinary and common meaning, as understood by those skilled in the art, should be attributed. The term is not limited to any specific or adapted meaning. Without limitation, the term can refer in particular to the temperature below which a system of quantum mechanical effects is dominated. In particular, the well-known quantum mechanical statistics, Bose-Einstein statistics, and Fermi-Dirac statistics apply in these regions. The transition temperature—also called the "critical temperature" Tc—is very low for most superconductors; to achieve superconductivity, the material generally needs to be cooled with liquefied helium (boiling point -269 °C). Only for high-temperature superconductors is liquefied nitrogen (boiling point -196 °C) sufficient for cooling.Other cryogens with lower boiling points can also be used to advantage.
[0080] The term "in the assembled state," as used here, is a broad term to which its ordinary and common meaning, as understood by a person skilled in the art, should be attributed. The term is not limited to any specific or adapted meaning. Without limitation, the term can refer in particular to a state in which the cooling system is mounted on or arranged on a central shaft.
[0081] In summary, without limiting further possible embodiments, the following embodiments are proposed:
[0082] Embodiment 1: Cooling system for a rotor, comprising a first vacuum chamber, wherein the first vacuum chamber is configured for rotatable arrangement relative to a central shaft and is subjected to a vacuum relative to atmospheric conditions, wherein electrical coils are arranged in the first vacuum chamber, a refrigerant reservoir, wherein the refrigerant reservoir is arranged and rotatable in the first vacuum chamber, wherein the refrigerant reservoir is thermally connected to the coils, and a housing with a cylindrical housing projection, wherein the housing has a refrigerant inlet, a refrigerant channel and a refrigerant outlet, wherein the refrigerant inlet and the refrigerant outlet are formed in the housing, wherein the refrigerant outlet is fluidly connected, in particular gas-permeable, to the refrigerant reservoir, wherein the housing projection is configured such thatthat in the assembled state it projects coaxially to the central shaft of the housing and is arranged section by section between the central shaft and the first vacuum space, wherein the refrigerant inlet is fluidly connected to the refrigerant channel, wherein the refrigerant channel extends section by section in an egg-shaped curve into the refrigerant reservoir.
[0083] Embodiment 2: Cooling system according to the preceding embodiment, wherein, in the assembled state, the refrigerant reservoir together with the first vacuum chamber is rotatable relative to the central shaft and the housing projection.
[0084] Embodiment 3: Cooling system according to one of the preceding embodiments, wherein the central shaft can be rotatably mounted in the housing projection.
[0085] Embodiment 4: Cooling system according to one of the preceding embodiments, wherein the housing with the housing projection are immovable.
[0086] Embodiment 5: Cooling system according to one of the preceding embodiments, wherein the first vacuum chamber is rotatably mounted on the housing projection.
[0087] Embodiment 6: Cooling system according to the preceding embodiment, wherein the first vacuum chamber is rotatably mounted on the housing projection by means of gas-tight bearings.
[0088] Embodiment 7: Cooling system according to the preceding embodiment, wherein the gas-tight bearings are ferrofluid-sealing bearings.
[0089] Embodiment 8: Cooling system according to the preceding embodiment, wherein the ferrofluid-sealing bearings have an inner ring, an outer ring, at least one rolling element and a receiving area filled with a ferrofluid, wherein the inner ring is arranged on the housing projection, wherein the outer ring is arranged on the first vacuum chamber, wherein the at least one rolling element is movably received between the inner ring and the outer ring.
[0090] Embodiment 9: Cooling system according to the preceding embodiment, wherein the receiving area is arranged on at least one axial side of the ferrofluid sealing bearing.
[0091] Embodiment 10: Cooling system according to one of the preceding embodiments, wherein the refrigerant reservoir is hollow cylindrical. Embodiment 11: Cooling system according to one of the preceding embodiments, wherein the refrigerant channel, in the assembled state, extends no more than 180° in any circumferential direction around the central shaft.
[0092] Embodiment 12: Cooling system according to one of the preceding embodiments, wherein an annular space is formed in the housing projection, wherein the refrigerant outlet channel is fluidly connected to the refrigerant reservoir by means of the annular space and is particularly gas-permeable.
[0093] Embodiment 13: Cooling system according to the preceding embodiment, wherein the refrigerant channel is at least partially arranged in the annular space.
[0094] Embodiment 14: Cooling system according to one of the two preceding embodiments, wherein the refrigerant channel extends through the annular space.
[0095] Embodiment 15: Cooling system according to one of the three preceding embodiments, wherein the housing has a second vacuum chamber, wherein the second vacuum chamber is arranged in the housing projection, wherein the second vacuum chamber is subjected to a negative pressure relative to atmospheric conditions.
[0096] Embodiment 16: Cooling system according to the preceding embodiment, wherein the second vacuum space coaxially surrounds the annular space.
[0097] Embodiment 17: Cooling system according to one of the two preceding embodiments, wherein the second vacuum space surrounds the annular space with respect to the axis of rotation on a radially inner side and on a radially outer side.
[0098] Embodiment 18: Cooling system according to one of the preceding embodiments, wherein the refrigerant reservoir touches the coils or is thermally connected to the coils by means of a cooling bus.
[0099] Embodiment 19: Cooling system according to one of the preceding embodiments, wherein the coils are superconducting coils. Embodiment 20: Rotor comprising a cooling system according to one of the preceding embodiments, electrical coils, wherein the coils are arranged in the first vacuum chamber, and a central shaft.
[0100] Embodiment 21: Rotor according to the preceding embodiment, wherein the central shaft is made of solid material or is designed as a hollow shaft.
[0101] Embodiment 22: Rotor according to one of the two preceding embodiments, further comprising a torque transmission element, wherein the torque transmission element is arranged inside a wall of the first vacuum space.
[0102] Embodiment 23: Electric machine comprising a rotor according to one of the three preceding embodiments and a stator.
[0103] Embodiment 24: Electric machine according to the preceding embodiment, further comprising a refrigeration system, wherein the refrigeration system is fluidly connected to the refrigerant inlet and the refrigerant outlet.
[0104] Embodiment 25: Electric machine according to the preceding embodiment, wherein the refrigeration system is designed to provide refrigerant at a temperature below a transition temperature of a material of the electrical coils.
[0105] Brief description of the characters
[0106] Further details and features will become apparent from the following description of exemplary embodiments, particularly in conjunction with the dependent claims. The respective features can be implemented individually or in combination with one another. The invention is not limited to these exemplary embodiments. The exemplary embodiments are shown schematically in the figures. Identical reference numerals in the individual figures denote identical or functionally equivalent elements, or elements that correspond to one another with respect to their functions. Specifically, the figures show:
[0107] Figure 1 shows a cross-sectional view of a cooling system according to an embodiment of the present invention; and
[0108] Figure 2 shows a perspective view of the annular space and the refrigerant channel.
[0109] Description of the exemplary implementations
[0110] Figure 1 shows a cross-sectional view of a cooling system 100 according to an embodiment of the present invention. The cooling system 100 is designed to cool a rotor 102 of an electric machine 104. The electric machine 104 can, for example, be a wind turbine.
[0111] The rotor 102 has a central shaft 106. As shown in the present embodiment, the central shaft 106 is preferably designed as a hollow shaft. Alternatively, the central shaft 106 can be made of solid material. The central shaft 106 is rotatable about an axis of rotation 108. However, the central shaft 106 does not necessarily have to be rotatable. In this case, the axis 108 represents an axis of rotation around which the central shaft 106 is formed. The central shaft 106 is made of metal, preferably steel. However, it is explicitly emphasized that alternative materials for the central shaft 106, as well as its precise design, are fundamentally conceivable.
[0112] The cooling system 100 further comprises a first vacuum chamber 110. In its assembled state, the first vacuum chamber 110 is rotatable relative to the central shaft 106, in particular about the axis of rotation 108. The first vacuum chamber 110 is subjected to a vacuum equivalent to atmospheric conditions. Electrical coils 112 are arranged in the first vacuum chamber 110. In its assembled state, the coils 112 are arranged coaxially with the central shaft 106. Thus, in its assembled state, the coils 112 are distributed circumferentially around the central shaft 106, in particular uniformly. The electrical coils 112 can be electrically connected to electrical components of the rotor 102, which can serve as an excitation component. The electrical connection to components outside the rotor 102 can be implemented without physical contact. The coils 112 are superconducting coils. The cooling system 100 also has a refrigerant reservoir 116.The refrigerant reservoir 116 is hollow and cylindrical. It is located within the first vacuum chamber 110. In its assembled state, the refrigerant reservoir 116 is rotatable relative to the central shaft 106, specifically about the axis of rotation 108. The refrigerant reservoir 116 is rotatable relative to the central shaft 106, particularly together with the first vacuum chamber 110. The refrigerant reservoir 116 is thermally connected to the coils 112. Specifically, the refrigerant reservoir 116 is thermally connected to the coils 112 by means of a cooling bus 118. The cooling bus 118 is made of a material with good thermal conductivity, such as copper. In particular, each coil 112 is thermally connected to the refrigerant reservoir 116 by means of its own cooling bus 118. The refrigerated buses 118 can, for example, extend in a star shape from the refrigerant reservoir 116 to the coils 112.Alternatively, the refrigerant reservoir 116 can contact the coils 112. This is possible, for example, by a sufficiently large radial design of the refrigerant reservoir 116. However, it is explicitly emphasized that the design of the refrigerant reservoir 116 shown is exemplary and the exact design of the refrigerant reservoir 116 depends on the specific machine requirements.
[0113] The cooling system 100 further comprises a housing 120 with a cylindrical housing projection 122. The housing 120 and the housing projection 122 are fixed in place. The first vacuum chamber 110 is rotatably mounted on the housing projection 122, as described in more detail below. The housing 120 has a refrigerant inlet 124, a refrigerant channel 126, and a refrigerant outlet 128. The refrigerant inlet 124 and the refrigerant outlet 128 are formed within the housing 120. The refrigerant outlet 128 is fluidly connected to the refrigerant reservoir 116 and, in particular, is gas-permeable. The refrigerant outlet 128 of the cooling system 100 is shown facing downwards for clarity only and could instead be arranged upwards around the refrigerant inlet 124.
[0114] In its assembled state, the housing projection 122 extends coaxially from the housing 120 to the central shaft 106 and is partially or completely located between the central shaft 106 and the first vacuum chamber 110. The central shaft 106 is rotatably mounted in the housing projection 122. Several conventional bearings 130 are arranged between the central shaft 106 and the housing projection 122. The bearings 130 are selected according to the expected rotational speed, load, and service life. Generally, the design process must determine whether a point load or a circumferential load acts on the inner or outer ring of the bearing. This load case (point load or circumferential load) then determines whether a tight fit or a loose fit is required for the inner or outer ring of the bearing.The housing projection 122 is, in particular, cylindrical and, in the embodiment shown, has a length 132 that is greater than its outer diameter 134. However, other configurations of the housing projection 132 are also conceivable in principle. The refrigerant inlet 124 is fluidly connected to the refrigerant channel 126. The refrigerant channel 126 extends in sections in a spiral shape into the refrigerant reservoir 116. In the assembled state, the refrigerant channel 126 extends in sections in a spiral shape around the central shaft 106 into the refrigerant reservoir 116. The refrigerant channel 126 extends, in particular, by no more than 180° with respect to any circumferential direction around the central shaft 106. It is explicitly emphasized that the exact configuration of the refrigerant channel 126 depends on the respective machine requirements. Thus, the material of the refrigerant channel 126 must be suitable for low temperatures, i.e.,Strength, embrittlement, and coefficients of expansion are adapted. Examples of materials from which the refrigerant duct 126 can be manufactured include stainless steels such as 1.4301, 1.4571, 1.4429, and the like. Invar, i.e., steel 1.3912, is also possible. Other materials are also generally feasible.
[0115] An annular space 136 is formed in the housing projection 122. The annular space 136 is bounded by an inner wall 138 of the housing projection 122 and by an outer wall 140 of the housing projection 122. The outer wall 140 of the housing projection 122 is shorter in the axial direction than the inner wall 138 of the housing projection 122. The refrigerant reservoir 116 adjoins an axial end 142 of the outer wall 140 of the housing projection 122 and the annular space 136. It is explicitly emphasized that the illustrated configuration of the annular space 136 is merely exemplary and that the exact configuration with regard to diameter, wall thickness, length, and the like is freely selectable and adapted to the respective application. The refrigerant outlet 128 is fluidly connected, and more precisely gas-permeable, to the refrigerant reservoir 116 via the annular space 136.
[0116] Figure 2 shows a perspective view of the annular space 136 and the refrigerant channel 126. As shown in Figure 2, the refrigerant channel 126 is located at least partially within the annular space 136. In particular, the refrigerant channel 126 extends through the annular space 136. As can be clearly seen in Figure 2, the refrigerant channel 126 extends in a semicircular shape around the central shaft 106 through the annular space 136 into the refrigerant reservoir 116. As further shown in Figure 1, the housing 120 has a second vacuum chamber 144. The second vacuum chamber 144 is located in the housing projection 122. The second vacuum chamber 144 is pressurized relative to atmospheric conditions. The second vacuum chamber 144 surrounds the annular space 136 coaxially. More precisely, the second vacuum chamber 144 is formed as a double ring.In particular, the second vacuum chamber 144 surrounds the annular chamber 136 with respect to the axis of rotation 104 on a radially inner side and on a radially outer side. Thus, a radially inner part or region of the second vacuum chamber 144 is located on a side of the annular chamber 136 facing the central shaft 106, and a radially outer part or region of the second vacuum chamber 144 is located on a side of the annular chamber 136 facing away from the central shaft 106.
[0117] The first vacuum chamber 110 is rotatably mounted on the housing projection 122 by means of gas-tight bearings 146. For example, one gas-tight bearing 146 is arranged between the first vacuum chamber 110 and the inner wall 138 of the housing projection 122, and another gas-tight bearing 146 is arranged between the first vacuum chamber 110 and the outer wall 140 of the housing projection 122. Thus, the gas-tight bearings 146 are arranged on opposite axial sides of the refrigerant reservoir 116. The annular space 136 is separated from the gas-tight bearings 146 by only a narrow passage. The gas-tight bearings 146 are preferably ferrofluid-sealing bearings. The ferrofluid-sealing bearings (not shown in detail) have an inner ring, an outer ring, at least one rolling element, and a receiving area filled with a ferrofluid. The inner ring is arranged on the housing projection 122. The outer ring is arranged on the first vacuum chamber 110.The inner ring and the outer ring are positively connected to the surrounding radial surfaces of the housing projection 122 and the first vacuum chamber 110, respectively. The rolling element(s) is or are movably mounted between the inner ring and the outer ring. The mounting area is located on at least one axial side of the ferrofluid-sealing bearing.
[0118] The cooling system 100 can, for example, be part of a rotor 102 of an electric machine 104, such as a wind turbine. The rotor 102 then comprises the coils 112 arranged in the first vacuum chamber 110 or is electrically connected to them. The rotor 102 100 can further comprise a torque transmission element 148. The torque transmission element 148 can be flange-shaped. The torque transmission element 148 is arranged on the inside of a wall 150 of the first vacuum chamber 110. The electric machine 104 further comprises a stator 152. The electric machine 104 further comprises a refrigeration unit 154. The refrigeration unit 154 is fluidly connected to the refrigerant inlet 124 and the refrigerant outlet 128. For this purpose, the refrigerant inlet 124 can be connected to a discharge opening of the refrigeration system 154 (not shown in detail) and the refrigerant outlet 128 can be connected to a supply opening of the refrigeration system 154.The refrigeration system 154 is designed to supply refrigerant 156 at a temperature below the transition temperature of a material of the electrical coils 112. The refrigerant 156 is, for example, liquid nitrogen, liquid helium, liquid neon, or another refrigerant suitable for superconductivity.
[0119] The torque transmission element 148 is connected, for example, to the drive side of the wall 150 of the first vacuum chamber 110, such as via a gearbox. Thus, the side of the cooling system 100 with the torque transmission element 148 represents the drive end. The side of the cooling system 100 with the housing 120 represents the non-drive end. The electrical energy is then drawn off from a stator (not shown).
[0120] The following describes an operating mode of the cooling system 100. According to the embodiment described above, there are components of the cooling system 100 that remain stationary and do not rotate, and rotatably mounted components, each rotating at a specific speed. The central shaft 106, for example, rotates at a first speed of approximately 10 revolutions per minute around the axis of rotation 108. Refrigerant 156 is supplied in liquid form by the refrigeration unit 154 and fed to the refrigerant channel 126 via the refrigerant inlet 124. The refrigerant 156 is guided in a spiral path along a radius of the central shaft 106 through the refrigerant channel 126 to the refrigerant reservoir 116 in the direction of the rotor 102.The refrigerant channel 126 is wound in a spiral shape around the central warm chamber of the central shaft 106, which serves, for example, as a pitch tube, such that a continuous gradient with respect to gravity is maintained for the refrigerant. This results in only a spiral half-winding over the distance to be bridged between the stationary refrigeration technology of the refrigeration system and the refrigerant reservoir 116, designed as a rotating "ring pool" in the rotor 102. The central shaft 106 is free internally and thus available for any desired application. The cooling system 100 allows cooling from the non-drive end and even a certain inclination of the axis of rotation 108, provided that the inlet to the refrigerant channel 126 at the housing projection 122 is higher with respect to gravity than the outlet from the refrigerant channel 126 at the refrigerant reservoir 116. Stationary components are mounted on the central shaft 106 and supported by conventional bearings 130.These stationary components comprise the refrigerant inlet 124, the refrigerant channel 126 around the central shaft 106, which directs the refrigerant 156 into the refrigerant reservoir 116, and the refrigerant outlet 128, through which gaseous refrigerant 156 can be discharged. The liquid refrigerant 156 is guided through the stationary components into the refrigerant reservoir 116. The refrigerant reservoir 116 rotates at a second speed, for example, 600 revolutions per minute. The refrigerant 156 is introduced into the refrigerant reservoir 116 and forced radially outwards by centrifugal forces. Design considerations include the clearance dimensions to the stationary components, which must be adapted to the specific requirements.
[0121] The refrigerant reservoir 116 is located in the evacuated first vacuum chamber 110, which contains the superconducting coils 112 of the rotor 102. The coils 112 are thermally connected to the refrigerant reservoir 116 via a cooling bus 118. This bus, through its thermal conductivity, brings the coils 112 of the rotor 102 to the temperature of the refrigerant reservoir 116, enabling them to operate in the superconducting state. The cold-gas-tight bearings 146 support the components rotating at the second speed #2 relative to the stationary components and prevent the escape of gaseous refrigerant. Evaporated refrigerant 156 is returned from the refrigerant reservoir 116 to the refrigeration system 154 via the annular space 136 and the refrigerant outlet 128.
[0122] Reference symbol list
[0123] Cooling system
[0124] Rotor electric machine
[0125] Central shaft
[0126] axis of rotation of first vacuum chamber
[0127] Sink
[0128] Refrigerant reservoir
[0129] refrigerated bus
[0130] Housing
[0131] housing protrusion
[0132] Refrigerant inlet
[0133] Refrigerant channel
[0134] Refrigerant outlet
[0135] Storage
[0136] length
[0137] Outer diameter
[0138] annular space inner wall outer wall axial end of the outer wall second vacuum space gas-tight bearing
[0139] Torque transmission element
[0140] wall of the first vacuum chamber
[0141] stator
[0142] refrigeration system
[0143] Refrigerant
Claims
Karlsruhe Institute of Technology, December 17, 2025 KIT17219PC ST / PF / PF Claims 1. Cooling system (100) for a rotor (102), comprising a first vacuum chamber (110), wherein the first vacuum chamber (110) is configured for rotatable arrangement relative to a central shaft (106) and is subjected to a vacuum relative to atmospheric conditions, wherein electrical coils (112) are arranged in the first vacuum chamber (110), a refrigerant reservoir (116), wherein the refrigerant reservoir (116) is arranged and rotatable in the first vacuum chamber (110), wherein the refrigerant reservoir (116) is thermally connected to the coils (112), and a housing (120) with a cylindrical housing projection (122), wherein the housing (120) has a refrigerant inlet (124), a refrigerant channel (126) and a refrigerant outlet (128), wherein the refrigerant inlet (124) and the refrigerant outlet (128) are formed in the housing (120), wherein the refrigerant outlet (128) is fluidly connected to the refrigerant reservoir (116),wherein the housing projection (122) is designed such that, in the assembled state, it projects coaxially from the housing (120) to the central shaft (106) and is arranged section by section between the central shaft (106) and the first vacuum chamber (110), wherein the refrigerant inlet (124) is fluidly connected to the refrigerant channel (126), wherein the refrigerant channel (126) extends section by section in an egg-shaped curve into the refrigerant reservoir (116).
2. Cooling system (100) according to the preceding claim, wherein in the assembled state the refrigerant reservoir (116) together with the first vacuum chamber (110) is rotatable relative to the central shaft (106) and the housing projection (122).
3. Cooling system (100) according to one of the preceding claims, wherein the central shaft (106) is rotatably mounted in the housing projection (122).
4. Cooling system (100) according to one of the preceding claims, wherein the housing (120) with the housing projection (122) are immovable.
5. Cooling system (100) according to one of the preceding claims, wherein the first vacuum chamber (110) is rotatably mounted on the housing projection (122).
6. Cooling system (100) according to the preceding claim, wherein the first vacuum chamber (110) is rotatably mounted on the housing projection (122) by means of gas-tight bearings (146).
7. Cooling system (100) according to the preceding claim, wherein the cold gas-tight bearings (146) are ferrofluid-tight bearings.
8. Cooling system (100) according to the preceding claim, wherein the ferrofluid-dense bearings have an inner ring, an outer ring, at least one rolling element and a receiving area which is filled with a ferrofluid, wherein the inner ring is arranged on the housing projection (122), wherein the outer ring is arranged on the first vacuum chamber (110), wherein the at least one rolling element is movably received between the inner ring and the outer ring.
9. Cooling system (100) according to the preceding claim, wherein the receiving area is arranged on at least one axial side of the ferrofluid sealing bearing.
10. Cooling system (100) according to one of the preceding claims, wherein the refrigerant reservoir (116) is hollow cylindrical.
11. Cooling system (100) according to one of the preceding claims, wherein the refrigerant channel (126) extends in the assembled state by no more than 180° with respect to a circumferential direction around the central shaft (106).
12. Cooling system (100) according to one of the preceding claims, wherein an annular space (136) is formed in the housing projection (122), wherein the refrigerant outlet channel (128) is fluidly connected and in particular gas-permeable to the refrigerant reservoir (116) by means of the annular space (136).
13. Cooling system (100) according to the preceding claim, wherein the refrigerant channel (126) is arranged at least partially in the annular space (136).
14. Cooling system (100) according to one of the two preceding claims, wherein the refrigerant channel (126) extends through the annular space (136).
15. Cooling system (100) according to one of the three preceding claims, wherein the housing (120) has a second vacuum chamber (144), wherein the second vacuum chamber (144) is arranged in the housing projection (122), wherein the second vacuum chamber (144) is subjected to a negative pressure relative to atmospheric conditions.
16. Cooling system (100) according to the preceding claim, wherein the second vacuum space (144) coaxially surrounds the annular space (136).
17. Cooling system (100) according to one of the two preceding claims, wherein the second vacuum space (144) surrounds the annular space (136) with respect to the axis of rotation (104) on a radially inner side and on a radially outer side.
18. Cooling system (100) according to one of the preceding claims, wherein the refrigerant reservoir (116) contacts the coils (112) or is thermally connected to the coils (112) by means of a cooling bus (118).
19. Cooling system (100) according to one of the preceding claims, wherein the coils (112) are superconducting coils.
20. Rotor (102) comprising a cooling system (100) according to one of the preceding claims, electrical coils (112) wherein the coils (112) are arranged in the first vacuum space (110) and a central shaft (106).
21. Rotor (102) according to the preceding claim, wherein the central shaft (106) is made of solid material or is designed as a hollow shaft.
22. Rotor (102) according to one of the two preceding claims, further comprising a torque transmission element (148), wherein the torque transmission element (148) is arranged inside a wall (150) of the first vacuum space (110).
23. Electric machine comprising a rotor (102) according to one of the three preceding claims and a stator (152).
24. Electric machine according to the preceding claim, further comprising a refrigeration system (154), wherein the refrigeration system (154) is fluidically connected to the refrigerant inlet (124) and the refrigerant outlet (128).
25. Electric machine according to the preceding claim, wherein the refrigeration system (154) is designed to provide refrigerant (156) at a temperature below a transition temperature of a material of the electrical coils (112).