DE102019112389B4 - Cooling of electric motors - Google Patents

Abstract

A stator (1) for an electrical machine (10) with a plurality of teeth (3) separated from one another by slots (2) around which coil windings (SW) are wound in the slots (2) to form coils, the coil windings (SW ) of the respective coil are made of a waveguide (4) each, which is guided in several windings (W1, ..., Wn) on each other around the respective tooth (3) and both ends (41, 42) of each waveguide (4 ) are simultaneously and reversibly connected to a collector (6) via suitable connecting pieces (5) so that a coolant (KM) can flow through the respective waveguides (4), the collector (6) being an electrically non-conductive ring-shaped collector (6 ) and is arranged in the axial direction (R) with respect to the axis of rotation of a rotor (20) of the electrical machine (10) above the stator (1) and two separate inlet and outlet channels (61, 62) encircling the collector (6) ) as coolant channels for connection to the hollow comprises conductor (4), each waveguide (4) comprising at least in the area of the windings (W1, ..., Wn) a rectangular first outer cross section (4qa) and an inner cross section (4qi), the outer side (4a) of which has an electrically insulating coating (43), the connection pieces (5) being led out of the coil winding (SW) in such a way that all waveguides (4) can be contacted separately and the individual ends (41, 42) as inlets (41) and outlets (42 ) the waveguide (4) each parallel to the inlet channel (61) and the outlet channel (62) of the collector (6) are connected in a sealed manner, the collector (6) or a cover (67) closing the collector having a web which the Inlet and outlet channels (61, 62) separates from one another.

Description

Field of the invention

The invention relates to a stator for an electrical machine with directly cooled windings and an electrical machine with such a stator.

Background of the invention

Electrical machines use the properties of electromagnetic interaction and the magnetic force effects between stator and rotor. Electrical machines can be operated as a motor or generator. There are various topologies of rotating electrical machines with one (or more) stator (s) and one (or more) rotors that are movably mounted relative to them. In general, these electrical machines are named according to the plane in which the magnetic flux lines spread and interact, e.g. radial, axial or transverse flux machines. A distinction is also made between concentrated and distributed windings. For applications with more than two coils per pole per phase, distributed windings are mostly used. A main advantage of distributed windings is that the magnetomotive force in the air gap between the stator and the rotor of the machine has a lower proportion of harmonics, i.e. a lower proportion of undesired harmonics of the magnetomotive force. This results in a high efficiency of the electrical machine with low rotor losses, low noise and few vibration problems.

The power range of electrical machines extends over many orders of magnitude up to one gigawatt, as for example with the turbo generators used in the power plant sector. The energy conversion within the electrical machine from electrical to mechanical energy and vice versa is associated with different loss mechanisms, which are expressed in the form of heat. The components penetrated by the current and magnetic flux must be cooled within their thermal operating limits - especially in the high power range and with high power density of the electrical machine. Particularly in the current-carrying winding, high power losses are generated under load with high power loss densities, which must be dissipated. In addition to taking into account the thermal operating limits of the conductor and winding insulation, an increase in the winding temperature leads to an increase in the ohmic conductor resistance, which in turn generates additional losses in the conductor and leads to a reduction in efficiency.

Permanent magnets have a defined demagnetization curve or characteristic depending on their operating temperature and the magnetic flux which penetrates them. If permanent magnets are installed in the rotor of the electrical machine, the excitation of the magnets initially decreases reversibly with the operating temperature up to a certain point. If the temperature rises further, the magnet irreversibly loses its magnetization; the electrical machine is thus permanently damaged. In general, the cost of the permanent magnets used in the electrical machine increases with their resistance to demagnetization against temperature. If no additional, mostly technically complex and expensive cooling mechanisms are installed for the rotor, the rotor temperature is strongly dependent on the stator temperature and thus also on the temperature of the winding. The more the temperature in the rotor rises, the more current has to be adjusted by the inverter in order to keep the torque or the power constant over the time the machine warms up. This requires a certain degree of oversizing of the inverter, which in turn leads to an increase in its size and manufacturing costs.

There is therefore a need for a high-power and efficiently cooled electrical machine with a high degree of efficiency with low material and manufacturing costs and a long service life at the same time.

According to the prior art, indirect cooling of the windings is predominantly used. Here, the stator iron (usually designed as a stacked package of electrical steel sheets) is first cooled by means of a cooling jacket arranged on the stator iron around the yoke and cooled by means of a liquid coolant or by means of convection. The cooling effect is then passed on from the stator iron to the winding via the winding insulation. The current-carrying winding is therefore only indirectly connected to the coolant. This leads to a weakening of the cooling effect on the winding and, given a given load on the electrical machine, to a high temperature difference between the coolant and the winding. Above all, the electrical winding or slot insulation between the stator iron and the windings represents a high heat conduction resistance. This indirect form of cooling therefore limits the use of the stator due to the principle and leads to a non-compact size thanks to the additional cooling jacket on the stator iron the stator and thus the electrical machine.

A more effective and direct cooling of the winding can, as in the DE 10 2015 116 810 A1 , of the DE 10 2017 119 033 A1 or the US 9 515 530 B2 described, can be achieved by means of a waveguide winding of the electrical coils.

The US 9 515 530 B2 describes a stator with concentrated single-tooth winding, the tooth coils being made from cylindrical waveguides and all tooth coils being connected in parallel to an annular distributor, designed separately as the inlet and outlet of the cooling medium. This also includes the US 9 515 530 B2 the design of this arrangement with inlet and outlet on opposite sides of the stator.

In the DE 10 2017 119 033 A1 describes a winding piece in the form of a hairpin for a distributed winding, designed as a waveguide with a round end profile and a rectangular profile adapted to the groove.

In the CH 343 509 A a winding cooling for large electrical machines is described in which the solidly designed conductor or a bundle of electrical conductors is surrounded by metallic and weakly insulated cooling channels, which in addition to the function of conductor cooling inside, a thermal protective layer between the hot conductors inside and the thermal Form sensitive electrical conductor insulation around the conductors. It is the CH 343 509 A not a waveguide winding in the classic sense, but a segmented full conductor winding which is surrounded by cooling channels.

The patent specification DE 26 30 658 A1 describes a connection piece for the coolant supply of a waveguide winding which contains a nipple for connecting a hose for supplying the coolant, as well as an inner sleeve which accommodates the waveguides and connects them electrically in parallel, and hydraulically seals against each other via the use of solder foils. Furthermore, a method is described for shrinking the nipple, which is made of a harder material and has a bead for better sealing, onto the inner sleeve.

All waveguide windings or other designs for direct cooling of the conductor along the coil have in common that, as the coolant flows through or around the waveguide along the coil, the losses are dissipated directly in or on the winding. However, temperature differences arise in the winding due to the steadily increasing temperature of the coolant along the cooling path through the waveguide. Depending on the load point and the length of the cooling channel, as well as the coolant used and its flow rate through the waveguide, a temperature difference arises between the inlet and outlet side. The higher the temperature difference, the greater the mechanical stress in the machine, as well as the thermally determined aging and degradation of the winding insulation and therefore has negative effects on the service life of the corresponding components and, as described above, the utilization and efficiency of the electrical machine. One means of keeping the temperature difference between the inlet and outlet sides of the waveguide winding low is to increase the volume flow of the coolant and the associated pump pressure. For electrical machines in the power class of approx. 50kW to 1,000kW customary for cars, trucks and buses and with a customary voltage level of 200V to 1000V in the intermediate circuit of the inverter, when replacing the conventional winding with waveguides, as in the DE 10 2015 116 810 A1 shown, pump pressures of possibly up to more than 100 bar are necessary in order to press the cooling liquid through the waveguide winding at the appropriate flow rate. The greater the applied pressures, the more constructive effort and costs are incurred for sealing the hydraulic cooling circuit. In addition, high pressures to be applied increase the costs, the internal wear and the energy consumption of the pump due to the higher pump output required for this than, for example, lower pressures, which then cannot provide the desired cooling effect. These comparatively high pressures required in a conventional electrical machine with a waveguide winding instead of the usual copper winding are one of the main reasons why the technology of direct cooling has so far not been represented in the electromobility market.

A central feature of the invention is therefore the decoupling of the hydraulic and electrical interconnection of the individual waveguide coils, which electrically form a winding system. As many parallel connections as possible of the individual coils should be achieved hydraulically. This leads hydraulically to a subdivision of the distributed winding of a radial flux machine into structurally identical and thus inexpensive and reproducible individual coils, which have their hydraulic inlet and outlet channels arranged in an axial direction around the axis of rotation of the motor and the two collector channels in a ring around this axis of rotation. The special design of the connection geometry and the hydraulic collector element enable the use of standard sealing elements which are cost-effective and robust, as well as enable a reliable and automatable manufacturing process. In order to connect the machine electrically according to the required performance class and voltage level, detached from the hydraulic parallel connection of the individual coils, special connecting pieces are described. The Waveguide coil is initially described as a single wound waveguide and, in an alternative embodiment, can be implemented as a coil of the same shape made from a bundle of sub-waveguides. This division of the waveguide, known as segmenting, serves to suppress frequency-dependent current displacement losses in the winding. The aim of this segmentation is a comparatively increase in the polarity change frequency and the increase in power density made possible thereby. If the focus is on the torque density of an electrical machine, the design with a single waveguide should be preferred. If the electrical machine is to be optimized for a particularly high power density, the segmented design should be preferred. The design of the connection of the hydraulic inlet and outlet differ in both embodiments.

Summary of the invention

The object of the invention is to provide a very compact and equally cost-effective electrical machine that has a high degree of efficiency and a long service life, and offers the potential for reliable and cost-effective series production.

This object is achieved by a stator for an electrical machine with several teeth separated from one another by grooves, which are wound by coil windings in the grooves to form coils, the coil windings of the respective coil being made from a waveguide in each case, which is wound in several windings on top of one another is guided around the respective tooth and both ends of each waveguide are simultaneously and reversibly connected to a collector via suitable connecting pieces so that a coolant can flow through the respective waveguide, the collector being designed as an electrically non-conductive annular collector and related in the axial direction is arranged on the axis of rotation of a rotor of the electrical machine above the stator and comprises two separate ring-shaped inlet and outlet channels running around the collector as coolant channels for connection to the waveguide, each waveguide having a right angle at least in the area of the windings A kigen first outer cross-section and an inner cross-section, the outside of which has an electrically insulating coating, the connection pieces being led out of the coil winding in such a way that all waveguides can be contacted separately and the individual ends as inlets and outlets of the waveguides are each hydraulically parallel to the inlet channel and the outlet channel of the collector are connected in a sealed manner, the collector or a cover closing the collector having a web which separates the inlet and outlet channels from one another.

The present invention and its special design of the stator and its coil winding and the connection technology for connecting the waveguide to a coolant supply results in the best possible compromise between the minimum waveguide length of the individual waveguide coils, which are hydraulically connected in parallel to each other, thus the temperature difference in the coil winding under load, the The associated pump losses, which must be reduced, and the number and arrangement of the coil ends to be connected hydraulically in parallel in the existing installation space behind the winding head. The relatively short waveguide reduces the power requirement of the coolant pump to overcome the pressure drop and to generate the required coolant throughput. This enables a high degree of efficiency for the resulting electrical machine, since the drive power or energy of the coolant pump is taken from the overall system or the energy storage device (s) of the vehicle or aircraft and thus reduces the range or the efficiency the entire drive unit consisting of electrical machine, inverter and coolant pump, which is far less the case with the stator or the electrical machine according to the invention than with electrical drives according to the prior art.

In addition to the economic aspect of being able to save the cooling jacket due to the direct cooling of the coils, which is also used to cool the stator core and the rotor of the electrical machine, there are other advantages with the same installation diameter, which increase the performance and efficiency of the electrical system designed according to the invention Increase machine compared to the state of the art. In particular, the internal rotor version that dominates the market benefits from not having a cooling jacket. Instead of the fact that the radial installation space of the conventionally designed electrical machines with indirect cooling is reserved for the cooling jacket according to the state of the art (in standard designs approx. 15% to 30% of the complete stator cross-sectional area between the air gap and the outer contour of the housing), the present invention to enlarge the space freed up by the air gap diameter between rotor and stator, since the longer lever arm and the increased area in the air gap lead to an increase in torque of the electrical machine; in order to increase the copper cross-section in the groove, which results in reduced current density and reduced losses in the winding and in order to be able to make the yoke and the teeth wider in each case, as a result of which the iron losses are reduced and an improvement in the saturation behavior is achieved.

The stator and thus also the electrical machine according to the present invention are therefore inexpensive to manufacture and have compact, effective cooling using inexpensive components, without causing an increased risk of coolant losses or tightness problems due to the comparatively higher pressure according to the prior art. The good cooling results in the advantages described above for the magnets, the winding and the winding insulation, resulting in a high degree of efficiency, a long service life, reliable operation and lower costs.

In one embodiment, an aspect ratio of the long side to the short side of the first rectangular external cross-section can be from 1: 1 to 3: 1, with the long sides being stacked on top of each other in the case of several windings of the waveguide. In a further embodiment, a ratio of a maximum diameter of the inner cross section to the short side of the outer cross section is between 1: 3 and 3: 4. The smallest possible diameter should be selected so that the most advantageous bending properties of the waveguide are retained during the manufacture of the coil winding and the proportion of current-carrying copper for the bore (hollow part of the waveguide) is as high as possible. On the other hand, with a larger diameter of the inner cross-section (channel diameter), a higher volume flow of cooling medium can be achieved with the same pressure losses, and a larger surface can be provided to the waveguide, on which the heat is transferred from the waveguide to the cooling medium. As the coolant flows through the coil winding, the losses are dissipated from the winding. This creates temperature differences in the winding due to the steadily increasing temperature of the coolant along the cooling path. Depending on the flow rate of the cooling medium, the proportion between the outer contour of the waveguide and the inner cross-section of the waveguide (inner cooling channel), as well as the current or loss density in the waveguide, there is a temperature difference between the inlet and outlet side. With the geometries specified above, the mechanical stresses caused by the different temperatures in the components of the electrical machine are kept as low as possible due to the lower temperature difference, which also increases the efficiency of the electrical machine. Because an excessively large rise in the conductor temperature leads to an increase in the ohmic conductor resistance and thus to additional losses in the conductor, i.e. a reduction in efficiency.

With the present invention, the hydraulic parallel connection is decoupled from the electrical connection of the individual waveguide coils.

In a further embodiment, the rectangular first outer cross section comprises rounded edges. For reasons of manufacturing the waveguide and, if necessary, coating the outer contour with an electrically insulating material, the outer edges are slightly rounded.

In a further embodiment, the connection piece is designed in the manner of a cylinder with at least one circular second outer cross section. While the current-carrying waveguide, which is continuously wound and reshaped to form a coil, has a rectangular cross-section on the outside to ensure that the groove is filled as much as possible, the ends of the coil winding, which are used purely for hydraulic contact, are round on the outside, i.e. cylindrical. This change in shape is achieved by machining the ends of the waveguide. In a preferred embodiment, a length of the cylindrical connection piece is at least as great as an outer diameter of the second outer cross section. A waveguide can be connected to other waveguides of the like to form a phase line by electrical parallel or series connection.

In a further embodiment, the waveguide directly adjoining the inlet of the waveguide is located at the air gap between the stator and the rotor of the electrical machine. The rotor is cooled via the air gap, i.e. the surface area between the stator and rotor. It is therefore advantageous that the inlet side and thus the cold side of the waveguide or the coil winding is on the side of the air gap between the stator and the rotor in order to provide the most effective possible cooling of the rotor here. The permanent excitation of the magnets decreases reversibly with the temperature. The more the temperature in the rotor rises, the more current has to be adjusted by the inverter in order to keep the torque or the power constant over the time the machine warms up. In the present invention, this power reserve no longer needs to be kept available in size without effective cooling when dimensioning the inverter. The inverter can be dimensioned for a lower current and can therefore be made smaller and more cost-effective, since the rise in the rotor temperature is reduced by this special design of the coil winding. In principle, the production costs of permanent magnets increase with their resistance to demagnetization against temperature. The use of less temperature-resistant magnets made possible by the present invention brings a great potential for cost savings. Furthermore, a comparatively lower rotor temperature allows the use of plastic-bonded magnet material, which is generally less temperature-resistant. Plastic-bonded magnet material can be injected directly into the pockets of the rotor and thus allows a more complex shape of the magnets while being simple to manufacture. Through the use of waveguide technology instead of indirect cooling via the housing as the state of the art in general and through the described features of the invention in particular (all conductor bars located at the air gap are flowed through in parallel with cold coolant), the maximum potential of direct cooling can effectively reduce losses can also be exhausted from the rotor.

In a further embodiment, the connection pieces for the inlet and outlet of the coolant are located on the same side of the stator. This ensures that the coolant can be provided by a common collector for inlets and outlets of the coolant with the shortest possible supply lines and a compact design. If the inlets and outlets are on the same side of the stator, only an even number of waveguides stacked on top of one another per slot is possible.

In a further embodiment, the inlets and outlets are designed as connection pieces in the form of a jacket-like continuation of the inner cross-section with a reduced cylindrical outer cross-section compared to the rectangular first outside cross-section, the jacket-like continuation representing a sealing area of the connection piece for hydraulic sealing to the collector. The jacket surfaces of all shapes that are the same or similar to a cylinder are referred to as jacket-like. The hydraulic contact is made in the axial direction in relation to the axis of rotation of the rotor via the ring-shaped collector. All inputs and outputs are hydraulically connected in parallel. A single coil has exactly one input and one output. The total number of individual coils corresponds exactly to the number of slots or teeth on the stator. This results in 2 x the number of conductors to be hydraulically contacted. The hydraulic contact between the coil ends and the connection piece above can take place in parallel in the electrically non-conductive ring-shaped collector, independently of the electrical connection.

In a further embodiment, the waveguide is a segmented waveguide which in each case comprises a bundle of a plurality of sub-waveguides stacked one above the other and / or next to one another in direct mechanical contact. All numbers of sub-waveguides greater than 2. These sub-waveguides are electrically and hydraulically connected in parallel on the connection piece. However, the sub-waveguides are electrically insulated from one another over the insulation layer on their outer surfaces over the entire length of the formed coil. This bundle is formed into a coil which has the same shape and configuration as described above for individual waveguides. The shape and proportions of the individual waveguides correspond to the same shapes and proportions of the sub-waveguides.

In a preferred embodiment, the plurality of sub-waveguides in the bundle of sub-waveguides is an even number of sub-waveguides. In the course of the sub-waveguide in the reshaped coil winding, these are structurally parallel to one another or one above the other. With an even number of sub-waveguides, compact and robust stacking of the sub-waveguides is possible, which enables the volume of conductive material in the bundle of the waveguide to be maximized.

In a further embodiment, the sub-waveguides are electrically insulated from one another by a non-conductive coating outside an electrical contact area in the connection piece. This electrical segmentation of the individual sub-waveguides to one another leads to a significant suppression of unwanted frequency-dependent additional losses due to the current displacement effect in the winding.

In a further embodiment, the connection piece is hollow with an inside and receives the bundle of sub-waveguides therein. The inside is preferably adapted to a shape of the bundle of sub-waveguides.

Instead of machining all coil ends to produce connecting pieces from the waveguide material to provide a cylindrical geometry for hydraulic interconnection, a connecting piece is used that is placed over the bundle of waveguides (referred to as segmented waveguides). This connection piece combines several sub-waveguides which are stripped in this area, i.e. freed from the electrically insulating sheathing, to form a bundle without further processing steps having to be carried out on the waveguides, which greatly simplifies the manufacture of the stator according to the invention. In contrast to the single waveguide with a round / cylindrical coolant channel, the flow channel of the sub-waveguide can have alternative geometries for the segmented case. The cross-sectional contour of the coolant channel in the sub-waveguide can be round, oval, square or rectangular. The described proportions still existed. So should the diameter of a round tube-shaped channel or the height of a rectangular channel at least one third of the height of the sub-waveguide ( 1 : 3), to a maximum of three quarters of the height of the sub-waveguide (3: 4). In relation to the width of the flow channel and the width of the sub-waveguide, a ratio of 1: 4 to 3: 4 applies.

In a further embodiment, the connection piece has a fixing groove between the sealing area and the electrical contact area for fixing the connection piece in the electrically non-conductive collector. The connection pieces can thus be fixed securely in the collector, which further increases the pressure safety of the stator according to the invention. The collector and winding can be dismantled reversibly.

In a further embodiment, one or more gaps between the bundle of sub-waveguides and the inside of the connection piece are filled by means of a hardenable and electrically conductive material which, after a corresponding hardening process, seals the gaps in a pressure-tight manner, for example with solder. The solder is used to make electrical contact with the sub-waveguide and the connector and as a filler to hydraulically close the gaps between the sub-waveguides and the connector. The coolant flowing into the winding under high pressure through the hydraulic collector must be reliably sealed from the outside at this point over the life of the machine. Care must be taken here, however, that the heating associated with the soldering process does not introduce too much heat into the winding or sub-waveguide. This process must avoid damaging the outer insulation layer and blocking the coolant channels of the sub-waveguide.

In a further embodiment, the connection piece connects the bundle of the completed conductor ends of the sub-waveguide in the area of the connection piece electrically in parallel with one another. In this refinement, the electrical contacting of the sub-waveguides with one another and on the connection piece is realized without soldering by pressing the connection piece around the sub-waveguide. The advantage of crimping or. Press connections mean that no significant heat input into the connection piece and thus into the waveguide takes place during the connection process. The heat input can destroy or weaken the electrical insulation layer around the waveguide, which increases the risk of a machine defect due to an insulation fault. In order to produce hydraulic tightness, the gaps on the end face of the bundle of sub-waveguides facing the collector can be closed by a downstream welding process.

In a further embodiment, in addition to the electrical contact area, the connection piece also comprises a sealing area for hydraulic sealing on the collector ring.

In a further advantageous embodiment, instead of the connection piece, an electrically conductive connecting element with an electrically conductive sleeve is pressed in the area of the electrical contacting of the stripped ends of the sub-waveguide.
Both the sub-waveguide, the connecting element and the sleeve should consist of the same electrically conductive material, preferably copper and alternatively aluminum. The connecting element is slotted four times according to the rectangular outer geometry of the sub-waveguides stacked one above the other and next to one another. By pressing the sleeve over the four elements, which are shell-shaped in cross section, a flat connection of the sub-waveguide to the connecting element is achieved. In this context, a cross section is referred to as shell-shaped, which has a straight side facing the sub-waveguides and a pitch circle resting on the sleeve. The pitch circle has the same radius as the sleeve that has been widened by pressing on in the elastic area. If the elastic pretensioning force of the sleeve due to the comparatively low modulus of elasticity of copper or aluminum is not sufficient to ensure permanent pressure on the contact surfaces, another sleeve made of, for example, steel or stainless steel can be pressed around the copper sleeve in this area. The gaps between the individual waveguides, the connecting element and the sleeve that remain after the sleeve has been pressed on are closed by a welding process in order to produce hydraulic tightness. Laser or electron beam welding are preferred here. These welding processes are extremely fast, introduce little heat into the components and have a very high level of process reliability. The sleeve has a second cylindrical inner surface which is used for hydraulic contact with the hydraulic collector with standard sealing elements, preferably O-rings.
Through this connection, the non-destructive detachability from the hydraulic ring-shaped collector and the waveguide winding is retained. As described above, the coils or coil windings can be electrically connected to one another in series or in parallel independently of the hydraulic interconnection (all coil windings in parallel). For this purpose, the connecting elements are used, which are made of electrically conductive material, ideally copper. In 7th This connecting element is shown with two bushings for the sub-waveguide bundles for the serial connection of two adjacent segmented waveguide coils. Should the end of the spool be attached to a Star point ring or a phase connection are contacted, only one feedthrough is provided and the connecting elements are arranged radially outwards or inwards with respect to the central axis of rotation of the rotor and are electrically connected there.

The waveguides and connecting elements cannot have any insulation on the contact surfaces. The electrical insulation of the phase strands with one another and with respect to ground must be ensured by appropriate air and creepage distances in accordance with the voltage class of the electrical machine. In addition to the function of distributing the coolant and fixing the coil ends, the hydraulic collector also has the function of creating insulation bridges or webs between the current-carrying components.

In a further embodiment, the collector comprises an inlet funnel made of electrically non-conductive material for the coolant through the inlet and outlet channel of each waveguide coil and one or more sealing rings for sealing against the sealing area of the connection piece, the sealing rings being adapted to the shape of the sealing area are adapted and the inlet funnel locks the sealing ring or rings in their sealing position. The collector is thereby contacted or sealed with the connecting pieces of the waveguide or the coil windings in such a way that, in the event of failure of a sealing element, it can be replaced or serviced without destroying a component. This would not be possible with (hard) soldered connections according to the prior art. In the invention described here, instead of a non-releasable soldered connection, the connection piece of the coil winding is sealed with sealing rings against the collector consisting of non-electrically conductive material. O-rings are preferred because they represent the most economical solution and compensate for mechanical manufacturing tolerances well. An alternative are X-rings, also known as quad-rings. In order to reduce the probability of failure of the electrical machine, more than one sealing ring is preferably used per connector. The end of the inlet funnel facing the sealing rings has a depression in which the connecting pieces are centered. An involute-like inlet geometry that is as rounded as possible is most favorable in terms of flow for the inlet funnel. An inlet geometry that is easier to manufacture in terms of manufacturing technology is a cone. In order to fix the inlet funnel in its installation position, the cylindrical outer contour of the inlet funnel to the collector can be designed as a transition or press fit. Alternatively, the outer contour can be provided with a knurl or locked by means of a partial cover through the cover of the collector. Furthermore, it is alternatively possible to design the inlet funnel as a circumferential ring or as ring segments in the inlet or outlet channels of the collector.

In a further embodiment, an intermediate ring made of an electrically non-conductive material and encircling the sealing area is positioned between adjacent sealing rings. In an embodiment with at least two sealing rings, there are intermediate rings made of non-electrically conductive material between the sealing rings in order to additionally center the cylindrical connector in the inlet to the collector and to prevent mutual tensioning of the sealing rings, e.g. O-rings, during installation . The number of intermediate rings used per sealing point is the number of sealing rings -1.

In a further embodiment, the connection pieces are fixed in the collector by means of one or more fixing bridges pushed radially over the connection pieces into the collector. In this way, the connection pieces are additionally secured in their position for a very good seal and pressure resistance. During assembly, the fixing bridges are inserted radially into the hydraulic collector after the connecting pieces have been pushed in. By locking on the fixing groove, the coil ends are positively and releasably secured in the installation position. An alternative design of the fixation are individual bolts or rods that are inserted radially (star-shaped) or parallel to the radial central axis into the hydraulic collector.

In a further embodiment, the hydraulic collector is closed by means of an electrically non-conductive cover (collector cover) facing away from the stator. In particular, if the stator and rotor are designed as built-in components and are integrated into a gear housing, for example, the cover should be made of electrically non-conductive material. In addition to the formation of the two concentric coolant channels in the collector, the cover can thus be used to electrically isolate the star point ring as an exemplary voltage and current-carrying component from the periphery (the gearbox housing, for example) within the air and creepage distances customary for the respective voltage class. If the electrical machine sits in the vehicle as an independent component to be sealed, it is advantageous to integrate the function of the cover into the end shield in order to reduce the number of components built into the electrical machine. End shields of electrical machines are generally made of aluminum or steel. The function of an isolator cannot be provided in this embodiment. The hydraulic sealing of the coolant-carrying collector channels can be in in both cases by means of sealing rings that are preloaded in either the radial or axial direction. At the interface to the outside, a redundant or multiple redundant design is advantageous in order to reduce the probability of failure of the electrical machine in the event of failure of a sealing element.

In a further embodiment, the teeth of the stator each include a tooth head facing the rotor of the electrical machine, which is axially slipped onto a tooth body of the respective tooth. In the case of the stator according to the invention as a radial flux machine, the coil winding is preferably pushed radially into the slots of the stator during assembly. The distance between adjacent teeth at the air gap must therefore be slightly larger than the width of the waveguide. The formation of a pronounced tooth tip contour at the air gap would have advantages for the performance of the electrical machine, for example an increase in the torque with the same current load, a reduction in the short-circuit current, a reduction in additional losses in the conductor bars at the air gap induced by the field of the rotor (if permanently excited ), better heat dissipation of the heat loss from the rotor to the stator, which is usually better connected to the cooling system, and the function of the mechanical locking of the winding in the slot. In order to nevertheless realize the design of a pronounced tooth tip contour in combination with the winding according to the invention, the separate tooth tips are pushed axially onto the tooth body after the winding has been inserted into the stator slots. The tooth top elements can consist of stacked electrical steel or alternatively of sintered iron (SMC - soft magnetic composites). The tooth tips can be made as long as the laminated stator core or divided into shorter sections in order to reduce the assembly force when it is pushed on axially.

In a further embodiment, the coolant is an electrically non-conductive heat transfer oil, which is also chemically inert at least to copper. Thermal oil has a flowability that is at least comparable to that of water. In addition, the cooling properties of heat transfer oil can be more constant over a wider temperature range than, for example, of water. Alternatively, the coolant should be chemically inert to aluminum or silver.

In a further embodiment, a coolant pressure of less than 30 bar is applied to the coolant. Due to the inventive design of waveguides, collectors and connectors, depending on the machine size and its specific design, a maximum system pressure of between 3 and 30 bar is sufficient to achieve the advantages according to the invention by cooling the electrical machine.

In a preferred embodiment, the waveguide windings are designed as distributed windings. In the so-called distributed windings, the coil winding includes the slots or teeth of the other two phases (for a three-phase system). Due to the so-called stretching of the winding, conductors of different phases can also lie next to or on top of one another in the same slot. In any case, a single coil of a distributed winding comprises at least two teeth or slots per pole. This also applies to distributed windings in designs with a continuous meander-shaped winding, e.g. the wave winding (Continuous Hair Pin) or plug-in windings (Hair Pin). If the same number of rotor poles or the number of pole pairs is taken as a basis, then distributed windings usually have a significantly higher number of slots or teeth per pole compared to concentrated windings. With the same dimensions of the stator core, this results in a larger surface area between the stator iron and the slot or winding. In the active area of the stator package, this results in a significantly better thermal connection between the winding and the stator and vice versa, since the transition of the thermal losses between the winding and the stator iron via the slot insulation is the essential thermal bottleneck of an electrical machine. Distributed windings thus have clear advantages over concentrated windings due to the finer division of the stator described and the fact that the magnetomotive force in the air gap between the stator and rotor of the machine has fewer harmonics, i.e. a lower proportion of undesired harmonics of the magnetomotive force, which can lead to significantly lower rotor losses and thus to a higher continuous power density of the electrical machine. In practice, electrical machines with distributed windings are usually designed with lower poles than with concentrated windings and therefore with a comparatively wider yoke. The lower proportion of undesired harmonics and the wider yoke mean that these electrical machines are significantly quieter than electrical machines with concentrated windings. This criterion is particularly important in the area of passenger transport; for the private sector (cars) as well as the public sector (bus, train, plane).

The invention further relates to an electrical machine comprising at least one stator according to the invention and a rotor rotating around the respective stator as an external rotor or internal rotor with an air gap between the stator and the rotor Rotor. The electrical machine according to the present invention and the possibility of doing without the cooling jacket around the stator is therefore inexpensive to manufacture and has compact, effective cooling through the waveguide winding using inexpensive components, without causing an increased risk of coolant losses or leakage problems. The good cooling results in the advantages described above for the magnets, the windings and the insulation, resulting in a high degree of efficiency, a long service life, reliable operation and lower costs. The present invention thus provides an inexpensive electrical machine which has a high degree of efficiency and a long service life while at the same time operating reliably.

This electrical machine according to the invention is novel for the market of electric motors in mobility applications of all kinds. This includes vehicles bound by road and rail (cars, trucks, buses), aircraft and a large number of special vehicles or aircraft (e.g. VTOL). The required peak powers in these applications of 10 kW to 10 MW can be easily provided by the electrical machine according to the invention.

In one embodiment, the electrical machine is designed as a radial flux machine. The electrical machine can be designed as a radial flux machine both as an internal rotor or as an external rotor. In a radial flux machine, a distributed winding in the special configuration described in the claims is used, which reduces the length of the waveguide channels, decoupled from the electrical interconnection of the coils by the hydraulically parallel arrangement of all individual coils, and achieves improved cooling. The inventive use of waveguide technology in the electrical machine, in particular in the radial flux machine, not only solves the problem of more efficient cooling of the coil winding. Furthermore, due to a larger number of teeth in distributed winding with the same number of poles compared to concentrated windings and due to the rectangular shape of the waveguide for better thermal connection of the waveguide to the surfaces in the groove, the cooling jacket can be dispensed with.

In a further embodiment, a pump for the coolant to flow through the waveguides is integrated in a bearing plate or in a stator bore of the electrical machine. Depending on the operating point and design of the machine, there is a temperature difference between the inlet and outlet side of the coil. If the temperature difference is to be reduced, the volume flow of the coolant must be increased. This is accompanied by an increase in pump pressure. The shorter the length of the waveguide and the larger the inside diameter of the waveguide, the lower the pressure drop that needs to be covered by the coolant pump. It is therefore advantageous to lay the lines conveying coolant between the electrical machine, pump, heat exchanger or cooler and, if necessary, expansion tank as short as possible and free of bends or connecting elements. Therefore, in order to reduce the number of connecting elements and to make the arrangement and space requirements of the components involved in the cooling circuit as compact as possible, the coolant pump is integrated into the end shield of the radial flow internal rotor machine or into the stator bore for the external rotor.

• - Anpassen eines Kühlmittelstroms durch als Hohlleiter ausgeführte Spulenwicklungen von Spulen des Stators an einen jeweiligen Lastpunkt der elektrischen Maschine mittels einer variablen Regelung des elektrischen Pumpenmotors zum Pumpen des Kühlmittelstroms; und
• - Betreiben der elektrischen Maschine in einem so erreichten Minimum an Gesamtverlusten für den jeweiligen Lastpunkt.

Die Ohm'schen Verluste steigen in der elektrischen Maschine mit einer Zunahme der mittleren Wicklungstemperatur unter Last. Um die Verluste besser aus der Wicklung abzuführen, wird der Volumenstrom an Kühlmittel KM erhöht, um somit die Temperatur im Leiter und damit auch die entstehenden Verluste im Hohlleiter zu senken. Der höhere Volumenstrom wird mittels erhöhtem Pumpendruck erzeugt, wobei sich bei größerem Volumenstrom eine zum Durchfluss überproportionale Leistungsaufnahme der Pumpe 40 ergibt. Für jeden Lastpunkt ergibt sich ein Minimum M der Gesamtverluste, welcher für den Wirkungsgrad des Gesamtsystems das Optimum darstellt. Bei gegenüber dem Minimum niedrigeren oder höheren Volumenströmen überwiegend jeweils die Ohm'schen Verluste beziehungsweise die Verluste aus der Pumpe.The invention further relates to a method for optimizing an efficiency of an electrical machine according to the invention comprising at least one stator according to the invention and at least one pump unit with a pump motor, comprising the steps

• - Adaptation of a coolant flow through coil windings of coils of the stator designed as a waveguide to a respective load point of the electrical machine by means of a variable control of the electrical pump motor for pumping the coolant flow; and
• - Operation of the electrical machine with a minimum of total losses thus achieved for the respective load point.

The ohmic losses increase in the electrical machine with an increase in the mean winding temperature under load. In order to better dissipate the losses from the winding, the volume flow of coolant is increased KM increased in order to lower the temperature in the conductor and thus also the resulting losses in the waveguide. The higher volume flow is generated by means of increased pump pressure, with the higher volume flow resulting in a power consumption of the pump that is disproportionate to the flow 40 results. There is a minimum for each load point M. the total losses, which represents the optimum for the efficiency of the overall system. In the case of volume flows that are lower or higher than the minimum, predominantly the ohmic losses or the losses from the pump.

The embodiments listed above can be used individually or in any combination, deviating from the references in the claims to one another, to design the devices according to the invention.

Figure list

• 1: eine Ausführungsform (a) eines erfindungsgemäßen Stators (als Außenläufer und Radialflussmaschine), und (b) einer verteilten Spulenwicklung aus einem Hohlleiter;
• 2: eine weitere Ausführungsform des erfindungsgemäßen Stators (als Innenläufer und Radialflussmaschine) mit einem Sammler (a) in perspektivischer Ansicht und (b) im perspektivischen Schnittbild;
• 3: eine Ausführungsform eines einzelnen Hohlleiters und eines Anschlussstücks in perspektivischer Ansicht und im Schnitt senkrecht zu seiner Längsachse;
• 4: eine andere Ausführungsform des Anschlussstücks mit mehreren Sub-Hohlleitern (segmentiert) in perspektivischer Ansicht und im seitlichen Schnittbild längs der Längsachse des Anschlussstücks;
• 5: eine Ausführungsform des Anschlussstücks für den Einzelhohlleiter im Sammler im seitlichen Schnitt;
• 6: eine weitere Ausführungsform des Sammlers mit Anschlusstücken für die segmentierte Hohlleiterspule in perspektivischer Ansicht;
• 7: eine Ausführungsform der elektrischen Kontaktierung des Anschlussstücks mit Verbindungselement und Hülse;
• 8: eine weitere Ausführungsform des Anschlussstücks mit mehreren Sub-Hohlleitern (segmentiert) in perspektivischer Ansicht, die sich von der in 4 unterscheidet;
• 9: das Anschlussstück gemäß 8 im seitlichen Schnittbild längs der Längsachse des Anschlussstücks angeschlossen an den Sammler;
• 10: eine Ausführungsform des erfindungsgemäßen Stators mit mehrteiligen Zähnen aus Zahnkörpern und Zahnköpfen;
• 11: eine Ausführungsform einer erfindungsgemäßen elektrischen Maschine im seitlichen Schnitt mit Darstellung einer beispielhaften integrierten Anordnung der Kühlmittelpumpe;
• 12: ein Diagramm der Verlustleistung einer erfindungsgemäßen elektrischen Maschine als Funktion des Volumenstroms an Kühlmittel durch die Hohlleiter der Spulenwicklungen hindurch.

These and other aspects of the invention are shown in detail in the figures as follows.

• 1 : an embodiment (a) of a stator according to the invention (as an external rotor and radial flux machine), and (b) a distributed coil winding made of a waveguide;
• 2 : Another embodiment of the stator according to the invention (as an internal rotor and radial flux machine) with a collector (a) in a perspective view and (b) in a perspective sectional view;
• 3 : an embodiment of a single waveguide and a connector in a perspective view and in section perpendicular to its longitudinal axis;
• 4th : Another embodiment of the connection piece with a plurality of sub-waveguides (segmented) in a perspective view and in a sectional side view along the longitudinal axis of the connection piece;
• 5 : an embodiment of the connection piece for the single waveguide in the collector in a lateral section;
• 6th : Another embodiment of the collector with connecting pieces for the segmented waveguide coil in a perspective view;
• 7th : an embodiment of the electrical contacting of the connection piece with the connecting element and sleeve;
• 8th : Another embodiment of the connection piece with several sub-waveguides (segmented) in a perspective view, which differs from the in 4th distinguishes;
• 9 : the connector according to 8th in the side sectional view along the longitudinal axis of the connector connected to the collector;
• 10 : an embodiment of the stator according to the invention with multi-part teeth made of tooth bodies and tooth tips;
• 11 : an embodiment of an electrical machine according to the invention in a lateral section with an illustration of an exemplary integrated arrangement of the coolant pump;
• 12th : a diagram of the power loss of an electrical machine according to the invention as a function of the volume flow of coolant through the waveguides of the coil windings.

Detailed description of the exemplary embodiments

1 shows an embodiment (a) of a stator according to the invention 1 as an external rotor, and (b) a distributed coil winding SW from a waveguide 4th . The stator 1 here includes a large number of grooves 2 separated teeth 3 made by coil windings SW in the grooves 2 are wrapped to form coils. The coil windings SW of the respective coil are each made of a waveguide 4th executed here with two windings W1 , W2 each other around the respective tooth 3 is led. Every waveguide 4th is made using suitable connectors 5 with a coolant KM flows through. Every waveguide 4th possesses at least in the area of the windings W1 , W2 a rectangular first outer cross-section 4qa and an internal cross-section 4qi , its outside 4a an electrically insulating coating 43 having, wherein the connecting pieces 5 so from the coil winding SW are brought out that all waveguides 4th can be contacted separately and thereby the individual ends 41 , 42 as inlets 41 and outlets 42 the waveguide 4th each parallel to the inlet port 61 and the outlet duct 62 of a collector 6th can be connected in a sealed manner (see 2 - 4th ). The one at the inlet 41 of the waveguide 4th directly connected waveguide 4th is located at the air gap 30th of the stator 1 to the rotor 20th of the electric machine 10 while in the outlet 42 of the waveguide 4th Towards part of the waveguide 4th on that of the stator 1 facing bottom of the groove 2 is located. The outlet 42 is therefore not located directly on the groove base 2 , but within the stacked winding above a winding directly on the groove base 2 . The connecting pieces are located here 5 for inlet and outlet of the coolant KM on the same side of the stator 1 . The windings W1 , W2 are designed here as distributed windings. The coolant KM is an electrically non-conductive heat transfer oil that is also chemically inert, at least to copper. The coolant is used for cooling KM acted upon with a coolant pressure less than 30bar. The coil winding SW is designed here in such a way that the incoming coolant KM of the outer conductors in a groove 2 towards the middle of the groove 2 warmed up. In contrast to toothed coils or wildly distributed windings, this ensures that the “cold” waveguide passes through the air gap 30th to the rotor 20th and are closest to the bottom of the groove. In the coil winding shown here SW it is a single coil for an external rotor, in which in each slot 2 four waveguides 4th are stacked on top of each other. In this case there is a single coil with two waveguides each 4th in the two grooves 2 half of which are occupied by this single coil. The circumferential number of grooves or teeth over which this single coil of a distributed winding extends is at least two. In the case of a toothed coil with a concentrated winding, on the other hand, this winding turns exactly one tooth in two adjacent grooves. Versions with a total of two to 14 waveguides are advantageous 4th serially connected, i.e. continuously wound waveguides 4th per groove 2 feature. As the inlets and outlets 41 , 42 are on the same side of the stator, there are only even numbers of waveguides 4th per groove 2 possible. The coil winding shown SW in 1b is an example of the design of the electrical machine 10 as an external runner. The winding marked here as W1 and through which the coolant flows first is closest to the air gap between the stator and rotor and the slot base or the yoke of the stator.

2 shows a further embodiment of the stator according to the invention 1 as an inrunner with a collector 6th (a) in a perspective view and (b) in a perspective sectional view as an internal rotor machine. In order to mechanically stiffen the stator package, rods are used as stator bolts 11 axially pressed into the laminated core. The laminated individual sheets are usually fixed to one another in a form-fitting manner by means of punched noses or by gluing with baking varnish. The stator bolts 11 continue to be used to attach the end shields 50 . One of the end shields 50 can as in 11 the case shown the function of the lid 67 of the collector 6th take. The ends of the stator bolts 11 have a thread. This can be designed as an external thread or internal thread. Here are both ends as well 41 , 42 of each waveguide 4th using suitable connectors 5 simultaneous and reversible with a collector 6th connected to the respective waveguide 4th with a coolant KM can be flowed through, the collector 6th as an electrically non-conductive ring-shaped collector 6th executed and in the axial direction R. based on the axis of rotation of a rotor 20th (not shown here) of the electrical machine 10 above the stator 1 is arranged and two separate annular in the collector 6th circumferential inlet and outlet channels 61 , 62 as coolant channels for connection to the waveguide 4th includes. The individual ends 41 , 42 as inlets 41 and outlets 42 the waveguide 4th are each parallel to the inlet port 61 and the outlet duct 62 of the collector 6th sealed connected. The collector 6th is also by means of an electrically non-conductive cover 67 facing away from the stator in relation to the environment 1 locked.

3 Figure 3 shows an embodiment of a single waveguide 4th and a connector 5 in a perspective view and in section perpendicular to its longitudinal axis. The waveguide 4th has an aspect ratio long side 41 too short side 4k of the first rectangular outer cross-section 4qa from 1: 1 to 3: 1, in the case of multiple windings W1 , W2 of the waveguide 4th one above the other with the long sides 41 be stacked on top of each other. The ratio of a maximum diameter 4D of the inner cross-section to the short side 4k of the external cross-section 4qa is between 1: 3 and 3: 4. The internal cross-section 4qi is along the waveguide 4th executed circular. Here, the rectangular first external cross-section 4qa rounded edges. The connector 5 becomes in this embodiment from the waveguide 4th made by the waveguide 4th in the area of the connector 5 is twisted off so that the resulting fitting 5 cylinder-like with at least one circular second outer cross-section 5qa from the subsequent waveguide 4th stands out. Here is the length of the cylindrical connector 5 (Sealing area 51 ) is at least as large as an outside diameter 5D of the second outer cross-section 5qa . The inlets 41 and outlets 42 as connecting pieces 5 thus represent a jacket-like continuation 44 of the internal cross-section 4qi with opposite the rectangular first outer cross-section 4qa reduced cylindrical outer cross-section 5qa represents, the jacket-like continuation of the sealing area 51 of the connector 5 for hydraulic sealing to the collector 6th represents.

4th shows another embodiment of the connector 5 with waveguide 4th with several sub-waveguides 45 (segmented) in a perspective view and in the side sectional view along the longitudinal axis. Here is the waveguide 4th a segmented waveguide, each comprising a bundle of a plurality of sub-waveguides stacked in direct mechanical contact with one another and / or next to one another 45 includes, here two sub-waveguides 45 stacked next to each other in two layers. The sub-waveguide 45 are outside of an electrical contact area A. inside the connector 5 each electrically isolated from one another by a non-conductive coating. Another electrical contact area 52 on the outer contour of the connector is used to make contact with a connector 5 to the next. In the connector 5 are the sub-waveguides 45 preferably stripped along the entire length of the connector to provide a uniform thickness. The connector 5 itself is hollow inside with an inside 5i . Preferably the inside 5i to the shape of the bundle of the stripped ends of the sub-waveguide, which are therefore slightly reduced in size 45 adjusted (detail of the reduction not shown). One or more columns 54 between the bundle of waveguides 45 and the inside 5i are filled with a hardenable material for pressure-tight sealing, which, after a corresponding hardening process, forms the gap 54 seals pressure-tight. In the connector 5 becomes the bundle of sub-waveguides 45 electrically connected in parallel. The connector 5 also includes in addition to the electrical contact area 52 additionally a sealing area 51 for hydraulic sealing to the collector 6th . The for hydraulic collectors 6th consists of an electrically non-conductive or insulating material. Furthermore, the connection piece 5 between sealing area 51 and electrical contact area 52 an electrically isolated fixing groove 53 to fix the connector 5 on the collector 6th on.

5 shows an embodiment of the connector in the collector 6th in the side cut. The collector 6th each includes an inlet funnel 63 and one or more sealing rings 64 for sealing against the sealing area 51 of the connector 5 , with the sealing rings 64 on the shape of the sealing area 51 are adapted and the inlet funnel 63 the sealing ring or rings 64 locked in their sealing position. Between adjacent sealing rings 64 is here in each case the sealing area 51 circumferential intermediate ring 65 made of an electrically non-conductive material. In addition to the fit for the sealing and intermediate rings 64 , 65 disposes of the collector 6th About cylindrical and slightly larger in diameter than the cylindrical ends of the waveguide 4th Drilled hole for positioning and centering the coil ends. Furthermore, the collector has 6th a phase for inserting the coil ends during assembly. In a further embodiment, as an alternative to the phase, a countersunk hole for centering the rectangular conductor contour of the waveguide can be used 4th in the collector 6th to get integrated.

6th shows another embodiment of the collector 6th with connecting pieces 5 for the segmented waveguide winding with individual sub-waveguides in a perspective view. The connectors 5 are here in the collector 6th via each radial via the connecting pieces 5 Fixing bridges pushed into the collector 66 fixed. For the arrangement of the sealing rings 64 , Intermediate rings 65 , Inlet funnel 63 and arrangement of the sub-waveguides 45 reference is made to the previous figures. The fixing bridges 66 are made of an electrically non-conductive material.

7th shows another to 4th alternative embodiment of the electrical contacting of the connector 5 for the segmented waveguide coil with a plurality of sub-waveguides which are each stripped in this area, consisting of a connecting element 7th and sleeve 8th . The electrical contact with the connector 5 is made by means of a solderless pressing of an electrically conductive connecting element 7th with an electrically conductive sleeve 8th in the connector 5 produced. Here, too, are the sub-waveguides 45 inside the connector 5 stripped. The electrical connection of the waveguides 4th or coil windings SW each other and those of the phase connections are in the invention described here via electrically conductive connecting elements 7th realized as massive bridges (and not designed as waveguides) the sub-waveguides of different connection pieces 5 connect. An electrical parallel or serial connection of the individual coils can thus be independent of the hydraulic connection, depending on the application or voltage level and power class of the electrical machine 10 will be realized. Compared to the soldering process, the electrical contacting of the connecting elements 7th , 7p , 7s (e.g. connecting element 7th as a serial connector of coils of one phase, or as a connection element for phase connection 7p , or as a connecting element to the star point 7s , or the connector to the next phase in the case of a delta or triangle connection instead of a star point) mainly released by mechanical pressing. In this case, two waveguide coils segmented by four sub-waveguides each, for example, are passed through the connecting element 7th , 7p , 7s connected in series. The fasteners 7th , 7p , 7s are preferably made of the same electrically conductive material as the waveguide, preferably copper, and can be used as a phase-to-phase serial connector, as a phase connection to the power electronics and as a phase outlet to the star point or star point ring. A sleeve is then used for fastening 8th preferably made of the same material as the connecting element 7th , 7p , 7s pressed on. The connecting element 7th , 7p , 7s has a slotted sleeve contour with gaps 54 on, which inside for flat contact with the side surfaces of the individual waveguides 4th serves. The surfaces are pressed using another component, the sleeve 8th and realized their bore designed as an interference fit. The interference fit of fastener 7th , 7p , 7s and sleeve 8th can be designed cylindrical or conical. If the elastic pretensioning force of the sleeve should not be sufficient in some embodiments, an additional stainless steel sleeve can be placed around the sleeve, for example 8th be pressed. After pressing on the sleeve 8th remaining column 54 between the individual waveguides 4th , 45 , the connecting element 7th , 7p , 7s and the sleeve 8th are closed via a welding process. The area compressed and closed in this way represents the electrical contact area 52b of the connector 5 Here, laser and electron beam welding are preferred. These welding processes are extremely fast, introduce little heat into the components and have a very high level of process reliability.

8th shows a further embodiment of the connector 5 according to 7th with several sub-waveguides 45 (segmented) in perspective view, where in 8a first the serial connection between two coil windings SW by means of a connecting element 7th was produced. Here are the sub-waveguides 45 to each other Ends of the bundles of sub-waveguides 45 still without connector 5 . In 8b are then these other ends with matching connectors 5 comprising a connecting element 7p for phase connection and a connecting element 7s equipped to the star point. As with the two ends of the bundle of the sub-waveguide 45 in 8a are now the sub-waveguides with their stripped area through the connecting pieces 7th , 7p , 7s pushed and the respective sleeves 8th mechanically on the fasteners 7th , 7p , 7s for connection and contacting with the sub-waveguides 45 pressed.

9 shows the connector 5 according to 8th in the side sectional view along the longitudinal axis of the connector 5 connected to the collector 6th . The larger of the two inner cylinders of the sleeve 8th (please refer 7th ) serves as a sealing surface to the hydraulic collector 6th .
Here, for example, the installation or the serial connection of two segmented waveguide coils is connected in series to the collector 6th shown. The seal between the hydraulic collector 6th and sleeve 8th can with a sealing ring 64 and in the case of a redundant design with an additional intermediate ring 65 between the sealing rings 64 be solved. The sealing and intermediate rings 64 , 65 are on the inside of the sleeve 8th arranged, wherein the collector is designed so that it is in the sleeve 8th engages and by means of the sealing and connecting rings 64 , 65 against the inside of the sleeve 8th is sealed. For more details of the collector 6th will among other things 2 referenced.

10 shows an embodiment of the stator according to the invention 1 with multi-part teeth 3 from tooth bodies 32 and tooth tips 31 using the example of an internal rotor. The teeth 3 of the stator 1 each include a tooth tip 31 facing the rotor 20th of the electric machine 10 axially on a tooth body 32 of the respective tooth 3 is attached. The advantages of this embodiment lie in the form-fitting fastening of the tooth head 31 on the tooth body 32 by dovetail contour, undercut, or the like, as well as the partial overlap of the windings W1 , W2 with slot insulation to lock them radially.

11 shows an embodiment of an electrical machine according to the invention 10 as an internal rotor in a lateral section comprising a stator according to the invention 1 and one in the stator 1 rotating rotor 20th with an air gap 30th (indicated here) between stator and rotor 20th . The electrical machine is a radial flux machine with a pump 40 for flowing through the waveguide 4th with the coolant KM in a bearing shield 50 of the electric machine 10 is integrated (a stator bore for the external rotor, not shown here). The reduction in pressure loss comes from the coolant KM to flow through the cooling circuit is of particular importance. Therefore it is beneficial to relocate the coolant KM promotional lines 80 , 90 , 100 between electric machine 10 , Pump 40 Design, heat exchangers or coolers and, if necessary, expansion tanks as short as possible and free of bends or connecting elements. The coolant pump was designed to reduce the number of connecting elements and to make the arrangement and space requirements of the components involved in the cooling circuit as compact as possible 40 in the end shield 50 the radial flux internal rotor machine shown here or integrated into the stator bore for the external rotor (not shown here). With the maximum system pressures between 3 and 30 bar to be expected depending on the machine size and its specific design, various known pump topologies can in principle be used, such as, for example, the gear pump, gerotor pump or vane pump. What these pumps have in common is that the maximum speed at which the pump operates 40 is operated is limited. Electric motors 70 to drive these pumps 40 can set a significantly higher maximum speed according to the current state of the art. The direct drive of the pump shaft without translation through an interposed gear 60 So it causes a bigger electric drive 70 is needed to get the high torque for the pump 40 than this from the pure power requirement of the electric pump drive 70 would be necessary.
Due to the hydraulic contacting of the waveguide 4th Compared to conventional, indirectly cooled electrical machines, additional installation space required in the axial direction can be used around the entire pump unit 40 , 60 , 70 in the end shield 50 of the electric machine 10 to be integrated in waveguide design. As a gear 60 a planetary gear or a spur gear can be used. By integrating the pump 40 can use the otherwise required connecting cable 80 in the end shield 50 to get integrated. The passive pressure losses in the cooling circuit can be reduced as a result of the integration; the efficiency of the overall system increases.

12th shows a diagram of the power loss of an electrical machine according to the invention 10 as a function of the volume flow of coolant KM through the waveguide 4th of the coil windings SW through. With variable control of the electric pump motor 70 the coolant flow to the respective load point of the electrical machine 10 be adjusted. The aim of this control is the overall efficiency of the system consisting of the electrical machine 10 in waveguide design and the pump unit 40 to optimize. As in 12th shown, on the one hand, the ohmic losses increase with an increase in the average Winding temperature under load. From this point of view, it makes sense to determine the volume flow of coolant KM in order to better dissipate the losses from the winding, in order to lower the temperature in the conductor and thus also the losses in the waveguide. On the other hand, the increased pressure with a larger volume flow causes a power consumption of the pump that is disproportionate to the flow rate 40 . There is a minimum for each load point M. the total losses, which is the optimum for the efficiency of the overall system. The pump 40 must therefore be dimensioned for this optimum under maximum load. An alternative control method is the outlet temperature of the coolant KM to be kept as constant as possible. This does not represent an optimum for the efficiency of the drive system, but it is advantageous if a heater for a vehicle is operated with the heated coolant. By using the heat loss from the drive, an additional heater for generating heat can ideally be dispensed with. Compared to conventional electrical machines with indirect cooling (water cooling jacket as the general state of the art), direct conductor cooling allows a significantly higher temperature difference between flow and return. This is because the return temperature can be set almost equal to the maximum winding temperature with waveguide cooling (slightly higher temperature in the conductor than in the coolant due to the heat transfer gradient on the inner surface of the conductor). With conventional cooling, the difference in temperature between the winding and the flow mainly results from the thermal path cooling jacket - stator - slot insulation - winding. This temperature lift is generally significantly greater than the actual increase in the temperature of the coolant itself. If the heat exchanger for heating a passenger compartment is operated with a comparatively higher coolant temperature, then this can in turn be "down-sized". This results in a further potential for cost savings.

List of reference symbols

1

stator according to the invention

11

Stator bolt

2

Stator slots

21st

Slot insulation

3

Teeth of the stator

31

Tooth tip of the respective tooth

32

Tooth body

4th

Waveguide

4a

Outside of the waveguide

4D

maximum diameter of the inner cross-section of the waveguide

41

long side of the outer cross-section of the waveguide

4k

short side of the outer cross-section of the waveguide

4qa

Outer cross section of the waveguide

4qi

Inner cross section of the waveguide

41

one end of the waveguide as an inlet

42

one end of the waveguide as an outlet

43

insulating coating

44

coat-like continuation

45

Sub-waveguide

5

Connector

5i

Inside of the connection piece towards the bundle of waveguides

5D

Outside diameter of the connector

5qa

External cross-section of the connector

51

Sealing area of the connection piece

52, 52b

electrical contact area of the connector

53

Fixing groove

54

Gap between sub-waveguides and the inside of the connector

6th

Collector

61

Inlet port

62

Exhaust duct

63

Inlet funnel

64

Sealing ring (s)

65

Intermediate ring

66

Fixing bridge

67

cover

7th

Connecting element for connecting two connecting pieces, for example

7p

Connection element for phase connection

7s

Connection element to the star point

8th

Sleeve

10

electrical machine according to the invention

20th

Electric machine rotor

25th

Rotor shaft with bearings

30th

Air gap between stator and rotor

40

pump

50

Bearing shield

60

Gear stage for the coolant pump

70

Electric motor as a pump drive

80

radial connection channel

90

Distribution ring inlet duct (cold side)

100

Distribution ring outlet duct (hot side)

A.

Stripped area of the sub-waveguide in the connector

KM

Coolant, coolant flow

M.

Minimum of total losses

R.

axial direction

SW

Coil windings

W1 ... Wn

individual windings of the waveguide around a tooth or in a groove

Claims (30)

A stator (1) for an electrical machine (10) with a plurality of teeth (3) separated from one another by slots (2) around which coil windings (SW) are wound in the slots (2) to form coils, the coil windings (SW ) of the respective coil are made of a waveguide (4) each, which is guided in several windings (W1, ..., Wn) on each other around the respective tooth (3) and both ends (41, 42) of each waveguide (4 ) are simultaneously and reversibly connected to a collector (6) via suitable connecting pieces (5) so that a coolant (KM) can flow through the respective waveguides (4), the collector (6) being an electrically non-conductive ring-shaped collector (6 ) and is arranged in the axial direction (R) with respect to the axis of rotation of a rotor (20) of the electrical machine (10) above the stator (1) and two separate inlet and outlet channels (61, 62) encircling the collector (6) ) as coolant channels for connection to the hollow comprises conductor (4), each waveguide (4) comprising at least in the area of the windings (W1, ..., Wn) a rectangular first outer cross section (4qa) and an inner cross section (4qi), the outer side (4a) of which has an electrically insulating coating (43), the connection pieces (5) being led out of the coil winding (SW) in such a way that all waveguides (4) can be contacted separately and the individual ends (41, 42) as inlets (41) and outlets (42 ) the waveguide (4) each parallel to the inlet channel (61) and the outlet channel (62) of the collector (6) are connected in a sealed manner, the collector (6) or a cover (67) closing the collector having a web which the Inlet and outlet channels (61, 62) separates from one another. The stator (1) after Claim 1 , characterized in that an aspect ratio of the long side (41) to the short side (4k) of the first rectangular outer cross-section (4qa) can be from 1: 1 to 3: 1, in the case of several windings (W1, ..., Wn) of the waveguide (4) one on top of the other, these are stacked on top of one another with the long sides (41) in each case. The stator (1) after Claim 1 or 2 , characterized in that a ratio of a maximum diameter (4D) of the inner cross-section to the short side (4k) of the outer cross-section (4qa) is between 1: 3 and 3: 4. The stator (1) after Claim 3 , characterized in that the inner cross-section (4qi) along the waveguide (4) is circular. The stator (1) according to one of the preceding claims, characterized in that the rectangular first outer cross section (4qa) comprises rounded edges. The stator (1) according to one of the preceding claims, characterized in that the connecting piece (5) is designed in the manner of a cylinder with at least one circular second outer cross section (5qa). The stator (1) after Claim 6 , characterized in that a length of the cylindrical connection piece (5) is at least as great as an outer diameter (5D) of the second outer cross section (5qa). The stator (1) according to one of the preceding claims, characterized in that the waveguide (4) directly adjoining the inlet (41) of the waveguide (4) is located at the air gap (30) of the stator (1) to the rotor (20) of the electrical machine (10) is located. The stator (1) according to one of the preceding claims, characterized in that the connection pieces (5) for the inlet and outlet of the coolant (KM) are located on the same side of the stator (1). The stator (1) according to one of the preceding claims, characterized in that the inlets (41) and outlets (42) as connecting pieces (5) in the form of a jacket-like continuation (44) of the inner cross-section (4qi) with a reduced cylindrical outer cross-section (5qa) compared to the rectangular first external cross-section (4qa), the jacket-like continuation having a sealing area (51) of the connection piece (5) for hydraulic sealing to the collector (6) represents. The stator (1) according to one of the Claims 1 to 9 , characterized in that the waveguide (4) is a segmented waveguide which each comprises a bundle of a plurality of sub-waveguides (45) stacked in direct mechanical contact with one another, one above the other and / or next to one another. The stator (1) after Claim 11 , characterized in that the sub-waveguides (45) outside an electrical contact area (52) in the connection piece (5) are each electrically isolated from one another by a non-conductive coating. The stator (1) according to one of the Claims 11 or 12th , characterized in that the connection piece (5) is hollow with an inside (5i) and accommodates the bundle of sub-waveguides (45) therein, the inside (5i) being adapted to a shape of the bundle of sub-waveguides (45) is. The stator (1) according to one of the Claims 13 , characterized in that one or more gaps (54) between the bundle of waveguides (45) and the inside (5i) are filled by means of a hardenable material which, after a corresponding hardening process, seals the gaps (54) in a pressure-tight manner. The stator (1) according to one of the Claims 11 to 14th , characterized in that the connection piece (5) connects the bundle of sub-waveguides (45) in the electrical contact area (52) electrically in parallel with one another. The stator (1) according to one of the Claims 10 to 15th , characterized in that the connection piece (5), in addition to the electrical contact area (52), also comprises a sealing area (51) for hydraulic sealing to the collector (6). The stator (1) after Claim 16 , characterized in that the connection piece (5) has a fixing groove (53) between the sealing area (51) and the electrical contact area (52) for fixing the connection piece (5) on the collector (6). The stator (1) according to one of the Claims 11 to 17th , characterized in that electrical contact with the connector (5), to the electrical contact area (52), is made by means of a solderless pressing of an electrically conductive connecting element (7) with an electrically conductive sleeve (8) on the connector (5) . The stator (1) according to one of the Claims 10 to 18th , characterized in that the collector (6) each comprises an inlet funnel (63) and one or more sealing rings (64) for sealing against the sealing area (51) of the connecting piece (5), the sealing rings (64) being adapted to the shape of the sealing area (51) are adapted and the inlet funnel (63) locks the sealing ring or rings (64) in their sealing position. The stator (1) after Claim 19 , characterized in that an intermediate ring (65) made of an electrically non-conductive material and encircling the sealing area (51) is positioned between adjacent sealing rings (64). The stator (1) after Claim 19 or 20th , characterized in that the connecting pieces (5) are fixed in the collector (6) via one or more fixing bridges (66) pushed radially into the collector via the connecting pieces (5). The stator (1) according to one of the preceding claims, characterized in that the collector (6) is closed by means of an electrically non-conductive cover (67) facing away from the stator (1) in relation to the environment. The stator (1) according to one of the preceding claims, characterized in that the teeth (3) of the stator (1) each include a tooth head (31) facing the rotor (20) of the electrical machine (10), which axially on a tooth body (32) of the respective tooth (3) is attached. The stator (1) according to one of the preceding claims, characterized in that the coolant (KM) is an electrically non-conductive heat transfer oil, which is also chemically inert at least to copper. The stator (1) according to one of the preceding claims, characterized in that the coolant (KM) has a coolant pressure less than 30 bar applied to it. The stator (1) according to one of the preceding claims, characterized in that the windings (W1, ..., Wn) are designed as distributed windings. An electrical machine (10) comprising at least one stator (1) according to one of the preceding claims and one that revolves around the respective stator (1) as an external rotor or an internal rotor Rotor (20) with an air gap (30) between stator and rotor (20). The electric machine (10) after Claim 27 designed as a radial flow machine. The electric machine (10) after Claim 27 or 28 , characterized in that a pump (40) for flowing through the waveguide (4) with the coolant (KM) is integrated in a bearing plate (50) or a stator bore of the electrical machine (10). Method for optimizing an efficiency of an electrical machine (10) according to one of the Claims 27 to 29 comprising at least one stator (1) according to one of the Claims 1 to 26th and at least one pump unit (40) with a pump motor (70), comprising the steps of adapting a coolant flow (KM) through coil windings (SW) of coils of the stator (1) designed as a waveguide to a respective load point of the electrical machine (10) by means of a variable control of the electric pump motor (70) for pumping the coolant flow (KM); and - operating the electrical machine (10) with a minimum (M) of total losses thus achieved for the respective load point.

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