Air-cooled stator device for a high-performance flywheel energy storage system designed as an external rotor

Abstract

The disclosure relates to a stator device (1) for a high-performance flywheel energy storage device (6) designed as an external rotor, comprising a sleeve unit (2) which has a through-opening (2a) extending in an axial direction (A) of the sleeve unit (2), as well as an inner side (2b) facing the through-opening (2a) and an outer side (2c) facing away from the through-opening (2a); and comprising a motor-generator unit (3) which has a motor winding (3a) and which is arranged on the outer side (2c) of the sleeve unit (2); wherein the sleeve unit (2) has several cooling fins (2d) extending along the axial direction (A) on its inner side (2b) in order to provide a simplified stator device (1) for an external rotor electric machine of a flywheel energy storage device (6).

Description

Scope of the invention

[0001] The disclosure relates to a stator device for a high-performance flywheel mass storage device configured as an external rotor, comprising a sleeve unit having a through-opening extending in an axial direction of the sleeve unit, as well as an inner side facing the through-opening and an outer side facing away from the through-opening; and comprising a motor-generator unit having a motor winding and arranged on the outer side of the sleeve unit. During intended use, i.e., when the stator device is installed in an operated or operational flywheel mass storage device, the outer side typically borders a vacuum, and the inner side typically borders an atmospheric environment. background

[0002] In flywheel energy storage systems, electrical energy is converted into rotational energy and stored as such for varying periods of time, ranging from milliseconds to hours or days. Flywheel energy storage systems are available in internal rotor and external rotor designs. In internal rotor energy storage systems, a rotor rotates within a stator, which results in a large amount of space for the stator and, in particular, eases cooling. Consequently, such flywheel energy storage systems do not have a dedicated cooling system and are passively cooled via the ambient air without any special design measures.

[0003] In external rotor flywheel energy storage systems, a rotor rotates around a stator, resulting in many other components, such as the motor-generator unit and bearing system, being arranged within the rotor unit in a very limited space. Accordingly, the situation here differs fundamentally from internal rotor flywheel energy storage systems.

[0004] For example, various active and passive functional components must be arranged on a stator device, which must meet a multitude of different mechanical (strength, rigidity, etc.) and other requirements (determined, for example, by magnetic properties) in the smallest possible space. At the same time, the stator device typically separates an evacuated (negative pressure) area of ​​the flywheel energy storage system, in which the rotor device is located, from an ambient (atmospheric pressure) area.Since external rotor motors have limited installation space and require reliable transmission of high electrical power between the vacuum and atmospheric pressure ranges, as well as the ability to convert electrical energy into mechanical energy and back again, and the heat generated in the motor-generator unit providing power must be dissipated, external rotor flywheel energy storage systems generally require active cooling. In known implementations of flywheel energy storage systems in external rotor designs, such as DE 10 2020 208 153, this is achieved by fluid cooling due to the high power density of the motor-generator unit as the main heat source and the geometric constraints with poor accessibility to the heat sources.

[0005] Fluid cooling, using the machining processes commonly used in this field, such as turning and milling, results in a stator device composed of a multitude of different bodies, given the familiar geometric constraints. Typically, each body is optimized for a specific function, such as the motor-generator unit, bearings, cooling, etc. However, this composite design presents a number of disadvantages, particularly the large number of sealing surfaces between the vacuum and atmospheric pressure regions. High geometric tolerances are sometimes imposed on the individual bodies, as the joined bodies form a complex tolerance chain.

[0006] The technical task is therefore to provide a simplified stator device for an external rotor electric machine of a flywheel mass storage system. overview

[0007] This problem is solved by the subject matter of the independent claims. Advantageous embodiments emerge from the dependent claims, the description, and the figures.

[0008] One aspect relates to a stator device for a high-performance flywheel energy storage system designed as an external rotor. In the operational state, the high-performance flywheel energy storage system comprises an electric machine with a motor-generator unit and a rotor unit. A flywheel is then arranged on the rotor unit or formed by the rotor unit. The rotor unit is mounted by means of corresponding bearing elements, which are preferably arranged in bearing element receptacles on the stator unit. Magnetic bearing elements and / or safety bearing elements can be installed. The motor-generator unit and rotor unit are then arranged in the (vacuum) area of ​​the flywheel energy storage system and are thus typically located in a vacuum when the flywheel energy storage system is used as intended.

[0009] A high-performance flywheel energy storage system can be understood here as a flywheel energy storage system with a short power-on time. The power-on time refers to the time in which the flywheel energy storage system can be fully charged and / or discharged due to its design. Thus, a fully charged flywheel energy storage system—i.e., one equipped with the maximum permissible mechanical energy by design—can convert all stored mechanical energy into electrical energy and provide the corresponding electrical power with an exemplary power-on time of 15 seconds. Conversely, such a flywheel energy storage system can be fully charged within 15 seconds if no mechanical energy is stored in it.In particular, the flywheel storage device for which the stator device is intended is therefore designed as a flywheel storage device with a power time in a power time range with an upper limit of at most 300 minutes, in particular at most 30 minutes, in particular at most 20 minutes, in particular at most 15 minutes, in particular at most 10 minutes, and / or a lower limit of at least 15 seconds, in particular at least 1 minute, in particular at least 5 minutes. Of course, such a flywheel storage device can also be charged or discharged more slowly if necessary. The flywheel storage device has, in particular, a storage capacity of more than 1 kWh, preferably more than 5 kWh, particularly preferably more than 15 kWh, and most particularly preferably more than 20 kWh.

[0010] The stator device comprises the motor-generator unit with a motor winding and, for example, also a lamination. The motor-generator unit is arranged on an outer side of a sleeve unit of the stator device. The sleeve unit has a central through-opening extending in an axial direction of the sleeve unit, from which the outer side of the sleeve unit faces away, but towards which an inner side of the sleeve unit faces. The orientation of a side can be determined by a corresponding normal vector of the respective side. Since the through-opening is a central through-opening, the rotational axis of the associated rotor unit runs parallel to the axial direction through the through-opening.

[0011] The sleeve unit has a plurality of cooling fins running along its inner side in the axial direction, for example more than three, more than four, more than six, more than eight cooling fins, more than 12 or more than 16 cooling fins. The cooling fins are preferably positioned rotationally symmetrically around a central axis of the through-opening. The central axis can coincide with the axis of rotation of the associated rotor unit. The cooling fins preferably each protrude at least 25%, in particular at least 50% of a (local) maximum radius of the through-opening into the through-opening, for example at least 3 cm, at least 5 cm or at least 8 cm. In a very particularly preferred embodiment, at least two, preferably more than two and particularly preferably all cooling fins merge into one another in the region of the central axis.In particular, the cooling fins serve no other function apart from their cooling function (and any unavoidable stiffening function of the sleeve unit). In particular, a respective main extension plane of the various cooling fins runs parallel to the central or rotational axis.

[0012] This has the advantage that, with sufficient cooling capacity, a simplified design of the stator device and the high-performance flywheel mass accumulator as a whole can be realized. With significantly reduced complexity, i.e., fewer components, and without the extensive use of machining processes typically required in high-performance flywheel mass accumulators with liquid cooling, the concept of the air-flow through-hole, which is used here as a cooling channel, also enables further simplifications, such as the reduction of sealing and fitting surfaces as well as mechanical structural components.The present approach is therefore based on the finding that directing a cooling air flow through a central through-opening of a stator device of the electric machine, running along an axial direction, provides sufficient cooling performance during operation of the high-performance flywheel energy storage system and simultaneously enables significant design simplifications of the stator device and the flywheel energy storage system. This finding is particularly important for flywheel energy storage systems with a short operating time, where space constraints are particularly restrictive, since larger currents with corresponding heat generation occur there.

[0013] In one embodiment, a ventilation unit is provided, which is designed to generate and / or amplify a cooling air flow through the through-opening. The ventilation unit can have a fan for locally generating and / or amplifying the cooling air flow. Alternatively or additionally, the ventilation unit can have a ventilation duct or at least a ventilation duct attachment, via which a cooling air flow from an external fan is directed to and into the through-opening. This has the advantage that a minimum cooling capacity can be provided in a simple manner, for example, also as needed by a control coupled to a temperature sensor.

[0014] In a further embodiment, it is provided that the cooling fins extend as a whole and / or individually in the axial direction over a longer section of the sleeve unit than the motor-generator unit. The cooling fins can extend as a whole and / or individually in the axial direction over one or more sections of the sleeve unit, in which one or more magnetic bearing elements or magnetic bearing element receptacles are arranged on the outside of the sleeve unit. A magnetic bearing element receptacle refers to an area in which, when the stator device is used as intended, a magnetic bearing element of a magnetic bearing for the rotor unit is arranged. In particular, the cooling fins can extend as a whole and / or individually over more than 20%, preferably more than 35%, of the through-opening, and preferably less than 95%.This has the advantage that not only the motor-generator unit as the main heat source is better cooled, but other components, such as magnetic bearing elements, can also be cooled in a simple way.

[0015] In another embodiment, it is provided that the cooling fins are formed integrally (i.e., in one piece) and / or materially bonded to the sleeve unit at least in sections, i.e., in sections in the axial direction or continuously in the axial direction. In particular, they are formed with the sleeve unit at least in sections (in the axial direction). The cooling fins can, for example, be formed in interrupted sections. Thus, cooling fins can be formed in a limited axial section in which the motor-generator unit is arranged, as well as in one or more further limited sections in which, for example, magnetic bearing elements and / or magnetic bearing element receptacles are arranged.Between one limited section and the other limited sections (if necessary also between the other limited sections) there are one or more free sections in which the cooling fins are interrupted (and thus there are no cooling fins on the inside). If, for example, one limited section extends over 25% of the through-opening and two further limited sections each extend over 10% of the through-opening, the cooling fins in their entirety extend over 45% of the through-opening. The cooling fins and the (remaining) sleeve unit can be formed and / or produced accordingly, for example, using a press-and-beam process or a casting process. The press-and-beam process has the advantage that finer cooling fins can be produced compared to the casting process. This improves the cooling performance. The casting process has the advantage of greater design freedom.For example, the through-opening can have varying maximum radii in the axial direction. This can be combined with varying wall thicknesses and / or outer radii of the sleeve unit in the axial direction. This can, for example, locally maximize the cooling surface of the cooling fins, since different axial sections have different requirements for the stability of the sleeve unit. For example, in sections of the sleeve unit that are free of the motor-generator unit and / or bearing element-free sections of the sleeve unit, a thinner wall thickness of the sleeve unit and / or a larger outer radius of the sleeve unit and / or a larger maximum radius of the through-opening can be formed than in sections of the sleeve unit with a motor-generator unit and / or with bearing elements or bearing element receptacles.The one-piece / material-fit design of the cooling fins with the sleeve unit thus has the advantage of reducing the complexity of different components while maintaining mechanical stability and improving cooling performance through heat conduction within the sleeve unit.

[0016] The sleeve unit can be manufactured from a single piece along the through-opening, or it can be composed of at least two, i.e., two or more, sleeve unit section elements. Each of these sleeve unit section elements can have cooling fins as described in the last paragraph.

[0017] Accordingly, it can be provided that the sleeve unit is a sleeve unit that is cast in one piece, at least in sections, into respective sleeve unit section elements, preferably a one-piece cast sleeve unit (with a single sleeve unit section element). The sleeve unit section elements can, for example, be screwed together to form the sleeve unit. The design with multiple sleeve unit section elements is more advantageous from a manufacturing perspective, while the design with a single sleeve unit section element is more advantageous from the perspective of system complexity, cooling performance, and stability. The cast design nevertheless allows for local optimization for different functions, for example, for accommodating magnetic bearing / safety bearing elements or the motor-generator unit.

[0018] In one embodiment, it is provided that the ratio of polar to axial moment of inertia of a rotor unit belonging to the sleeve unit and / or motor-generator unit is less than 1, in particular less than 0.8. Accordingly, the sleeve unit can be referred to as a cylindrical sleeve unit, in contrast to an annular sleeve unit. Alternatively or additionally, it can be provided that a length of the sleeve unit (which, as can be seen from the last paragraph, can also comprise several sleeve unit section elements) in the axial direction is greater than an outer diameter of the sleeve unit, in particular at least twice or at least three times as large as the outer diameter. The outer diameter is preferably the outer diameter of the sleeve unit without further functional components, i.e. the outer diameter of the supporting structure of the sleeve unit.This has the advantage that the sleeve unit provides space on the outside for additional components and cooling performance is improved in that turbulence in the cooling air flow is reduced and the formation of a beneficial laminar flow is promoted.

[0019] In a further embodiment, the sleeve unit comprises one or more magnetic bearing element receptacles and / or one or more backup bearing element receptacles, preferably one or more magnetic bearing elements or backup bearing elements. This makes it possible, for example, to dispense with individual additional sleeve elements for accommodating the respective bearing elements. This also contributes to a reduction in the number of components, thus improving heat conduction in the stator while simplifying the design.

[0020] In another embodiment, motor phase connection cables connected to the motor winding run along the axial direction on the inside, in particular outside the section of the motor-generator unit, particularly preferably outside the section of the cooling fins. The motor phase connection cables are electrically coupled to the motor winding via respective vacuum feedthroughs. The vacuum feedthroughs are thus preferably also arranged in the through-opening. This has the advantage that the motor phase connection cables (acting as heat sinks for the vacuum feedthroughs) and in particular also the vacuum feedthroughs are directly cooled particularly well and, in particular, do not affect the cooling of the motor-generator unit.

[0021] In one embodiment, the stator device comprises a first termination unit arranged at a first axial end and / or a second termination unit arranged at a second axial end. The termination units comprise respective through-openings which adjoin the through-opening of the sleeve unit and continue this through-opening for the passage of the cooling air flow. The through-openings of the termination unit(s) can have a maximum radius which decreases in the direction of the through-opening of the sleeve unit and thus introduce the cooling air flow in a funnel-like manner into the through-opening of the sleeve unit. Preferably, the respective termination unit comprises a respective retainer bearing element receptacle, preferably one or more respective retainer bearing elements.By arranging the safety bearings on the end units, greater design space can be achieved due to the increased mechanical requirements on the safety bearings for the sleeve unit and thus, at the same time, improved cooling performance can be achieved with reduced component complexity.

[0022] Thus, the at least one termination unit is at least substantially, i.e. largely or entirely, preferably made of a different material, preferably of a different metal, than the sleeve unit. The metal of the sleeve unit preferably has a greater thermal conductivity than the metal of the at least one termination unit. Alternatively or additionally, the metal of the at least one termination unit can have a greater strength than the metal of the sleeve unit. For example, the sleeve unit can be made at least substantially of a light metal such as aluminum and / or a magnesium alloy, and the first and / or second termination unit can be made at least substantially of a ferrous metal such as iron, in particular cast iron, or steel. Accordingly, the first and / or second termination unit can be a cast or 3D-printed first and / or second termination unit, respectively.This has the advantage that reliable cooling is achieved in a structurally simple and safe manner.

[0023] A further aspect relates to a sleeve unit for a stator device according to one of the described embodiments.

[0024] Another aspect relates to an electrical machine for a flywheel storage device designed as an external rotor, with a stator device according to one of the described embodiments, as well as a flywheel storage device with such an electrical machine.

[0025] One aspect further relates to a method for cooling an electric machine of a flywheel mass storage device designed as an external rotor, comprising guiding a cooling air flow through a central through-opening of the stator device of the electric machine, said through-opening running along an axial direction of a stator device.

[0026] Advantages and advantageous embodiments of the latter aspects correspond to the advantages and advantageous embodiments described for the former aspect and vice versa.

[0027] The described features and feature combinations, including those in the general introduction, as well as the features and feature combinations disclosed in the description of the figures or the figures alone, can be used not only alone or in the described combination, but also with other features or without some of the disclosed features, without departing from the scope of the invention. Consequently, embodiments that are not explicitly illustrated and described in the figures, but that can be created by separately combining the individual features disclosed in the figures, are also part of the invention. Therefore, embodiments and feature combinations that do not encompass all features of an originally formulated independent claim are also to be considered disclosed.Furthermore, embodiments and combinations of features are to be considered as disclosed which deviate from the combinations of features or go beyond those described in the dependencies of the claims.

[0028] In the context of this disclosure, "transverse / alongitudinal" can be understood as "at least substantially perpendicular / parallel," i.e., "perpendicular / parallel" or "substantially perpendicular / parallel," i.e., perpendicular / parallel except for a predetermined deviation. The predetermined deviation can, for example, be at most 15°, preferably at most 5°, particularly preferably at most 3°. Accordingly, "oppositely oriented" in the context of this disclosure can be understood as "at least substantially oppositely oriented," i.e., "at least substantially antiparallel oriented." Detailed description

[0029] Exemplary embodiments are described in more detail below with reference to schematic drawings. Fig. 1 shows an exemplary embodiment of a stator device for a flywheel storage device designed as an external rotor in a sectional view and a plan view; and Fig. 2 an exemplary embodiment of a flywheel mass storage device with the stator device from Fig. 1 in a sectional view.

[0030] In the figures, identical or functionally equivalent features are provided with the same reference numerals.

[0031] Fig. 1 shows an exemplary embodiment of a stator device for a flywheel storage device designed as an external rotor, in part 1a) in a sectional view and in part 1b) in a plan view.

[0032] The stator device 1 from Fig. 1 has a sleeve unit 2, with a through-opening 2a running in an axial direction A (in this case parallel to the y-direction) of the sleeve unit 2, as well as an inner side 2b facing the through-opening 2a and an outer side 2c facing away from the through-opening 2a. When the stator device 1 is used as intended, the inner side 2b is an ambient-side inner side 2b, i.e. it borders on an ambient region U, which is typically at atmospheric pressure. When the stator device 1 is used as intended, the outer side 2c is a vacuum-side outer side 2c, i.e. it borders on a vacuum region V, which is typically evacuated, i.e. has a negative pressure compared to the ambient region U.However, a vacuum region V within the meaning of the present disclosure can also refer to a region which is filled with a gas which differs from the filling of the surrounding region and is not necessarily under a negative pressure.

[0033] The through-opening 2a is a central through-opening 2a, so that a rotation axis R (of the rotor unit 10 assigned to the stator device 1 ( Fig. 2) and thus also the stator device 1) extends longitudinally (in the y-direction) through the through-opening 2a. The sleeve unit 2 is a cylindrical sleeve unit 2 and, accordingly, in the example shown, has a length measured in the y-direction that is significantly greater than a (maximum) outer diameter measured in the x-direction (here, the length is at least an exemplary factor of 3 greater).

[0034] On the inner side 2b, the sleeve unit 2 has a plurality of cooling fins 2d running along the axial direction A, of which only one is shown here for reasons of clarity. The cooling fins 2d are designed (preferably solely for this purpose) to maximize heat transfer from the sleeve unit 2 to a cooling air flow S (which in this case runs in the positive y-direction). The cooling fins 2d are preferably integrally formed with the sleeve unit 2, i.e. with the rest of the sleeve unit 2. The cooling fins 2d extend at least as a whole, in this case each over a first section 2z of the sleeve unit 2 and thus have a length corresponding to the length of the first section 2z (in the y-direction). As shown in partial image 1b), the cooling fins 2d protrude radially into the through-opening 2a, so their main extension plane here runs parallel to the rotation axis R.

[0035] In the present case, the cooling fins 2d protrude from the inner side 2b determined by a (local) maximum radius rm of the through-opening 2a into the through-opening 2a, each with a depth t of approximately 50% of the (local) maximum radius rm of the through-opening 2a. They could also protrude further into the through-opening and even meet in the middle, i.e. have a depth t of 100%. The maximum radius rm can vary locally, i.e. along the y-direction. A wall thickness of the sleeve unit and / or the outer diameter of the sleeve unit can also vary in the y-direction, whereby within predetermined sections, for example the second section 2y defined in the next paragraph, the maximum radius rm and / or wall thickness and / or outer diameter are preferably constant.

[0036] The stator device 1 also has a motor-generator unit 3 with a motor winding 3a. The motor-generator unit 3 is arranged on the outer side 2c of the sleeve unit 2, in this case in a second section 2y of the sleeve unit 2. The second section 2y lies entirely within the first section 2z. Accordingly, the cooling fins 2d extend in the axial direction A over a longer section than the motor-generator unit 3.

[0037] In the example shown, one or more, here three, magnetic bearing elements 4, 4', 4" are arranged on the outer side 2c. Here, the largest magnetic bearing element 4' is arranged in the first section 2z, which is advantageous in terms of cooling.

[0038] On the inner side 2b, motor phase connection cables 5 connected to the motor winding are also arranged here, which run along the axial direction A. In this case, these are arranged outside the section 2y of the motor-generator unit 3, which improves the cooling of both the motor-generator unit 3 and the motor phase connection cables 5 and thus the vacuum feedthroughs 5a, and simplifies construction and assembly.

[0039] Fig. 2 shows an exemplary embodiment of a flywheel mass storage device with the stator device from Fig.1 in a sectional view. On the stator device 1, a first termination unit 7 is arranged at a first axial end, in this case an end oriented in the positive y-direction, and a second termination unit 8 is arranged at a second axial end, in this case an end oriented in the negative y-direction. Together with an outer wall unit 9, at whose axial ends the two termination units 7, 8 are arranged according to their arrangement on the stator device 1, the two termination units 7, 8 separate the vacuum region V in which a rotor unit 10 is arranged from the surrounding region U. Rotor unit 10 and stator unit 1 belong to an electrical machine required for the operation of the flywheel energy storage device 6. Both the flywheel energy storage device 6 and the electrical machine are (mutually dependent) designed as external rotors.

[0040] The end units 7, 8 have respective through-openings 7a, 8a that correspond to and continue the through-opening 2a. In the example shown, the through-openings 7a, 8a of the end units 7, 8 taper in a funnel shape toward the through-opening 2a of the sleeve unit 2 and merge flush into the through-opening 2a of the sleeve unit 2.

[0041] The end units 7, 8 also each have a backup bearing element 11, 12. Since the backup bearing elements 11, 12 are subjected to significantly greater forces than the magnetic bearing elements 4, 4', 4", this contributes to a simplified design. For example, the end units 7, 8 can be made of a material (such as cast iron or steel) that is more suitable for the backup bearing elements 11, 12 with the greater forces, and the sleeve unit 2 can be made of a material (such as aluminum or a magnesium alloy) that is more suitable for the cooling function. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 208 153

[0004]

Claims

[1] Stator device (1) for a high-performance flywheel mass storage device (6) designed as an external rotor, with - a sleeve unit (2) which has a through-opening (2a) extending in an axial direction (A) of the sleeve unit (2), as well as an inner side (2b) facing the through-opening (2a) and an outer side (2c) facing away from the through-opening (2a); - a motor-generator unit (3) which has a motor winding (3a) and which is arranged on the outer side (2c) of the sleeve unit (2); characterized by that the sleeve unit (2) has a plurality of cooling fins (2d) running on its inner side (2b) along the axial direction (A). [2] Stator device (1) according to claim 1, characterized by a ventilation unit which is designed to generate and / or amplify a cooling air flow (S) through the through opening (2a). [3] Stator device (1) according to one of the preceding claims, characterized bythat the cooling fins (2d) extend in the axial direction (A) over a longer section (2z) of the sleeve unit (2) than the motor-generator unit (3), preferably in each case extend in the axial direction (A) over a longer section (2z) of the sleeve unit (2) than the motor-generator unit (3). [4] Stator device (1) according to one of the preceding claims, characterized by that the cooling fins (2d) are formed at least in sections in one piece with the sleeve unit (2), in particular the cooling fins (2d) are formed at least in sections in one piece with the sleeve unit (2). [5] Stator device (1) according to one of the preceding claims, characterized by that the sleeve unit (2) is a sleeve unit (2) which is at least partially cast in one piece in respective sleeve unit section elements, preferably a sleeve unit (2) which is cast in one piece. [6] Stator device (1) according to one of the preceding claims, characterized by that the sleeve unit (2) is made at least substantially of a light metal, for example aluminum and / or a magnesium alloy. [7] Stator device (1) according to one of the preceding claims, characterized by that the sleeve unit (2) has one or more magnetic bearing element receptacles, preferably one or more magnetic bearing elements (4, 4', 4"). [8] Stator device (1) according to one of the preceding claims, characterized by that on the inside (2b), in particular outside the section (2y) of the motor-generator unit (3), motor phase connection cables (5) connected to the motor winding (3a) run along the axial direction (A). [9] Stator device (1) according to one of the preceding claims, characterized bythat the ratio of polar to axial moment of inertia of a rotor unit (10) belonging to the sleeve unit (2) and / or motor-generator unit (3) is less than 1, in particular less than 0.

8. [10] Stator device (1) according to one of the preceding claims, with a first termination unit (7) arranged at a first axial end and / or with a second termination unit (8) arranged at a second axial end, wherein the respective termination unit (7, 8) has at least one respective safety bearing element receptacle, preferably at least one respective safety bearing element (11, 12). [11] Stator device (1) according to the preceding claim, characterized by that the first and / or second termination unit (7, 8) is made at least substantially from a ferrous metal such as cast iron or steel, in particular is a cast first termination unit (7) or second termination unit (8). [12] Stator device (1) according to one of the preceding claims, characterized by that the sleeve unit and / or the motor-generator unit is designed for a flywheel storage device with a power time in a power time range with an upper limit of at most 300 minutes, in particular at most 30 minutes, in particular at most 20 minutes, in particular at most 15 minutes, in particular at most 10 minutes, and / or a lower limit of at least 15 seconds, in particular at least 1 minute, in particular at least 5 minutes and / or for a flywheel storage device with a storage capacity of more than 1kWh, preferably more than 5kWh, particularly preferably more than 15kWh, very particularly preferably more than 20kWh. [13] Sleeve unit (2) for a stator device (1) according to one of the preceding claims. [14] Electrical machine for a high-performance flywheel mass storage device (6) designed as an external rotor, with a stator device (1) according to one of claims 1-12, as well as high-performance flywheel mass storage device (6) with such an electrical machine. [15] Method for cooling an electrical machine of a high-performance flywheel mass accumulator (6) designed as an external rotor, comprising the method step: - guiding a cooling air flow (S) through a through-opening (2a) of a stator device (1) of the electrical machine, said through-opening running along an axial direction (A).

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