REVOLVING ENGINE

Description

[0001] The invention relates to a three-phase rotating field machine with the features of the preamble of claim 1.

[0002] Rotating field machines of this type are well known. For example, synchronous machines have the generic design, as shown in the American patent application US 2002 / 0047418 A1. Similar rotating field machines are disclosed in the Japanese patent application JP 2004 096874 A and the international application WO 2015 / 104795 A1.

[0003] In rotating field machines with so-called loop windings, the windings of each phase are located in two approximately diametrically opposed, axially parallel slots on the circumference of the stator. A first section of a winding lies in the first slot and runs along it to a first axial end or end face of the stator. There, the winding then enters a second slot, running parallel to a secant line relative to the stator cross-section. In this second slot, a second section of a winding runs to the opposite axial end of the stator. The axial end faces of the stator thus form so-called winding heads. The windings on one of these end faces not only run from one slot to the next but are also electrically connected in this area. This winding configuration can be divided into an electromagnetically active area and an inactive area.

[0004] Viewed longitudinally, the active area comprises that part of the

[0005] The active area includes the windings located in the slots, as well as the radial gap and the permanent magnets. In contrast, the winding sections at the axial end faces of the stator, i.e., the winding heads, constitute the inactive area, as they do not interact with the rotating magnetic field in the radial gap to generate torque. The length of these end-face winding sections is determined, as previously explained, by the fact that the electrical conductor must be moved forward and backward at two different machine poles. The winding sections in the area of ​​the winding heads therefore account for up to 50% of all copper losses in the stator.

[0006] Furthermore, in larger permanent magnet machines, the rotor is not used to contribute to the electromagnetic torque because the air gap is too large. Even in non-magnetic rotors, such as those of asynchronous machines with a larger number of poles, the rotor is not sufficiently utilized because the bore diameter must be increased to allow for higher power output.

[0007] German utility model DE 20 2015 006 632 U1 discloses a coaxial generator for a turbine, comprising an outer and an inner permanent magnet rotor element (magnetic wave and magnet array), between which an assembly with coil segments in the form of U-shaped hairpins is arranged, which surround a cylindrical coil carrier and are inserted with axial ends together with the coil carrier into a ring plate, which electrically connects the individual coil segments.

[0008] An electronically commutated DC machine with a coil arrangement consisting of circumferentially wound coils is known from European patent application EP 0 680 133 A1. A similar design of an electronically commutated DC machine with a stator arrangement having meandering, circumferentially extending sections of flat sheet metal is disclosed in German patent application DE 40 42 432 A1.

[0009] Electrical machines with an outer and an inner rotor element and a stator arrangement located between them are also known from international application WO 2016 / 035358 A1 and European patent application EP 2 701 290 A1.

[0010] The object of the present invention is to provide a three-phase rotating field machine which has lower copper losses, so that its efficiency and power density are increased compared to conventional rotating field machines.

[0011] This problem is solved by the rotating field machine with the features of claim 1. Advantageous embodiments are specified in the dependent claims.

[0012] According to the invention, it is proposed that the rotor has a second annular, in particular cylindrical, rotor element with permanent magnets, located concentrically and radially further outwards from the first rotor element, which is rotationally fixed to the first rotor element and to which the stator is spaced apart by a second air gap, and that a first section of a winding extends in an axial direction within the first air gap and, further along, transitions at the end face of the stator into a second section of the winding that is radially offset from the first section and extends in the opposite axial direction within the second air gap. The transition from the first section to the second section thus takes place within a winding head region.

[0013] A key aspect of the invention lies in the machine's design, in which the stator and rotor are nested within each other. This design significantly reduces the length of the end-face winding sections compared to conventional designs, as the turns of the individual windings no longer need to run diametrically or chordwise from one circumferential point of the stator to another. This reduces the inactive area of ​​the windings and simultaneously lowers copper losses. A larger proportion of the windings then becomes active and actively participates in generating electromagnetic torque. This results in increased efficiency and power density while maintaining essentially the same machine dimensions (length and diameter of the stator).

[0014] The machine design according to the invention has two magnetically active air gaps, namely the radially outer and the radially inner air gap, both of which contribute to torque generation, whereas in the prior art only one air gap is common and the magnetic field lines close via the magnetically passive return ring (yoke). In a certain sense, the second rotor element can be considered a return ring, which here, however, rotates together with the rotor, so that there are no remagnetization losses.

[0015] The windings can lie approximately in radial planes, meaning that the first and second sections are arranged at essentially the same azimuthal angle relative to the motor axis. However, it is also possible for the first and second sections to lie at different azimuthal angles, meaning that, relative to the radial cross-section of the machine, they lie on a chord of the machine. Furthermore, the sections can run essentially parallel to the motor axis, but they can also be inclined to it.

[0016] According to the invention, the two rotor elements are ring-shaped and thus surround the similarly ring-shaped stator radially on the outside and radially on the inside over its entire circumference. With regard to the axial cross-sectional geometry, several possibilities theoretically exist for the design of the rotor elements and the stator. Preferably, the stator has a circular or oval cross-sectional shape, wherein the two rotor elements, viewed in cross-section, merge into one another in such a way that the first and second air gaps transition into a common axial air gap in an arc-like manner. For example, the stator can have a circular cross-section, so that its shape corresponds to a torus, in which case the inner first rotor element has a concave outer circumference in cross-section, and the outer second rotor element has a concave inner circumference in cross-section. However, in order to easily join the rotor and stator axially, a rectangular cross-sectional geometry is advantageous.It is therefore advantageous if the first rotor element, the second rotor element, and the stator have a cylindrical axial cross-section. The axial length can be chosen arbitrarily, according to the desired torque that the motor is to generate.

[0017] According to one embodiment, the rotor has additional permanent magnets in the axial direction in front of the stator's end face. This has the advantage that the winding sections located in the winding head area are also within a magnetic field and thus contribute to torque generation. These additional permanent magnets are also suitably arranged in a ring shape. Their magnetization is axial.

[0018] According to a first alternative of the invention, the windings are wound onto an annular support structure. This has the advantage that the round wire commonly used for winding coils and transformers, which is comparatively thin with a diameter of 0.2 mm to 1.5 mm, can be used for manufacturing the windings of the rotating field machine according to the invention. Depending on the cross-sectional geometry of the rotor elements, the support structure can also be cylindrical or form a hollow cylinder.

[0019] In the first alternative, the support structure consists of a non-magnetic material, such as plastic. The windings are therefore ironless and form air-gap windings between the two rotor elements. This has the advantage that there are neither remagnetization losses nor iron losses. This further increases efficiency. In addition, there are no cogging torques, resulting in smoother and quieter operation. Iron saturation cannot occur, and the stator inductance is lower.

[0020] Preferably, the material of the support structure is paramagnetic or diamagnetic. It therefore does not influence the magnetic field lines, so that the magnetic circuit of opposing magnetic poles is closed via the two rotor elements. In this embodiment, the opposing magnetic poles are magnetized in opposite directions. For example, a north pole of the inner permanent magnets is located in the first gap, and a south pole of the outer permanent magnets is located radially further out, or a south pole of the inner permanent magnets is located in the first gap, and a north pole of the outer permanent magnets is located radially further out.

[0021] The support structure is solid, i.e., not hollow, thus ensuring mechanical stability for the winding process. In its solid form, the support structure can also be considered the core.

[0022] Preferably, the support structure is formed from a solid core, wherein the

[0023] Windings in slots of the core, oriented towards the first and / or second air gap. Thus, slots can be located on the radial outside, the radial inside, or on both the outside and inside of the support structure.

[0024] According to another embodiment, the surface of the support structure facing the first and / or the second rotor element can be groove-shaped and made of insulating material. Each groove is radially open and forms a guide element for the winding wire, which is preferably a round wire. This provides support. As a result, the flux is utilized more efficiently, and the higher power density allows for the implementation of air-gap windings at higher power levels than currently possible.

[0025] According to a second alternative according to the invention, the windings are self-supporting, so that no support structure is required. Mechanical stability is ensured by the windings themselves. This significantly simplifies the manufacture of the rotating field machine. In this alternative as well, the windings are coreless, in particular ironless, and thus form pure air-gap windings.

[0026] For the formation of self-supporting windings, a flat wire can be used, which, due to its thickness and width, is dimensionally stable or rigid. The flat wire is ideally wound so that its flat sides face circumferentially. The individual turns of a winding then essentially form a single sheet, and correspondingly many of these sheets lie side by side circumferentially, forming the winding, according to the number of turns in the winding.

[0027] An alternative method for creating a self-supporting winding involves bonding the winding wire, for example, by impregnating it with a varnish or resin. The winding wire can be a standard round wire, which, unlike flat wire, is not dimensionally stable or rigid.

[0028] It is advantageous if the windings, especially the flat wire, are made of a ferromagnetic material such as iron or steel, as this generates a higher magnetic flux in the two air gaps and increases the machine's efficiency. It is acceptable that the ferromagnetic material has a higher ohmic resistance than, for example, copper. However, this is disadvantageous in the winding head area because the winding sections located there, which run essentially perpendicular to the air gaps (essentially radially), do not contribute to torque generation, at least not unless the aforementioned additional permanent magnets are arranged axially in front of the stator.

[0029] To mitigate this disadvantage, the winding sections located at the end face of the stator can be made of a more electrically conductive material than the first and second winding sections. According to this improved design, each winding thus consists of two different electrically conductive materials. This results in the winding sections at the end face, forming the winding head, having a lower ohmic resistance and therefore generating fewer ohmic losses. The winding sections in the winding head region are made of a highly conductive material such as copper.

[0030] To ensure the permanent magnets remain firmly in place during rotor rotation, they can be embedded within the first and / or second rotor element. Accordingly, they are not designed as surface magnets.

[0031] The permanent magnets are arranged and magnetized in the first and / or second rotor element such that the magnetic flux in the first and second air gap is essentially radial. Furthermore, both the first and second rotor elements have alternating north and south poles in the circumferential direction. Preferably, the magnetic poles of the first and second rotor elements are oriented at the same azimuthal angle to each other.

[0032] In the alternatives of the rotating field machine according to the invention without a ferromagnetic core, i.e., in the alternative "air gap winding" with a non-magnetic support structure and in the alternative with self-supporting windings, it is advantageous if the flux direction of the magnetic poles in the first and second air gaps points radially in the same direction. With opposing magnetic poles, they are thus magnetized in the same direction. Consequently, the magnetic field lines close only via the two rotor elements, i.e., not in the air gap or between the rotor elements. This results in a higher flux density in the air gaps, which, in a rotating field machine without a ferromagnetic core, act as a single air gap from the perspective of the magnetic field.

[0033] According to the invention, the first and second winding sections are azimuthally offset from each other. This means that, viewed circumferentially, the first winding section, which extends in one axial direction, is offset at a circumferential angle from the second winding section, which extends back in the opposite axial direction. In technical terms, this is also referred to as step reduction. Due to the different azimuthal angles of the first and second winding sections, turns of immediately adjacent windings overlap. This allows harmonics to be suppressed.

[0034] Ideally, the turns of the same winding are arranged in several layers on top of each other. Preferably, the turns of adjacent windings can be offset from each other in different positions so that the adjacent windings overlap circumferentially. This also helps to suppress harmonics.

[0035] According to one embodiment, the first and second rotor elements are non-rotatably connected to a shaft or a rotatable component of a driven load machine or a driving turbine. In the case of motor operation, the torque generated by the magnetic field is thus transmitted directly to the shaft or other component; in the case of generator operation, the rotary motion is transmitted directly to the rotor elements.

[0036] The rotationally fixed connection between the two rotor elements can be suitably achieved by attaching the first rotor element directly to a shaft and the second rotor element to a rotor disk that is rotationally fixed to the shaft. Alternatively, the first and / or the second rotor element can be attached to a rotor disk, which can be rotationally fixed to a shaft.

[0037] Advantageously, the rotor disc can be part of a pump impeller, for example, the support disc of a pump impeller. Thus, the impeller and the permanent magnet rotor, or at least the second rotor element, form a single structural unit with the impeller.

[0038] According to one embodiment, the support structure is firmly held to a stationary, particularly disc-shaped, support element by means of retaining elements. These retaining elements also serve as spacers for the winding head located between the support element and the support structure, which necessarily requires space. This space requirement is provided between the support element and the support structure, including the windings, by the retaining elements. It is advantageous if the ends of the individual windings are guided to the support element, for example axially, so that the windings can be connected at or in front of the support element. Preferably, the support element can also serve as a connection cap, i.e., it can itself carry the electrical connections for connecting the windings.

[0039] According to one embodiment, the inner and outer gaps can have different widths. This allows a winding wire with a rectangular cross-section to be laid more tangentially at the outer diameter of the support structure, i.e., on the side of the second air gap (the side faces are tilted relative to the radius, so that the radial height of the winding wire is less than its width), while at the inner diameter of the support structure, i.e., on the side of the first gap, the winding wire can be laid more radially (the side faces lie approximately at a radius, so that the radial height of the winding wire corresponds to its width). This is because the azimuth is longer in the outer gap. Therefore, there is space here to tilt the wire, which is lacking in the inner diameter. The advantage is that the outer air gap can be reduced, thus enabling higher flux densities.Preferably, the rotating field machine according to the invention can be a drive motor, in particular for driving a centrifugal pump.

[0040] For better understanding, the invention is explained below using a rotating field machine as an example. However, due to the material of a support structure used therein and the relative position of the first and second winding sections, the machine itself is not part of the invention. The following are shown: Fig. 1: A perspective view of a rotating field machine without stator support. Fig. 2: An axial longitudinal section view of the rotating field machine without stator support. Fig. 3: A perspective view of the rotating field machine with stator support. Fig. 4: A section of a radial cross-section of the rotating field machine. Fig. 5: An axial longitudinal section view of the upper half of the rotating field machine without stator support.

[0041] The Figures 1 to 4Figure 1 shows a three-phase rotating field machine 1 in the form of a drive motor with a stator 3 and a rotor 2, which has a first annular rotor element 5 with permanent magnets 7a and a second annular rotor element 6 with permanent magnets 7b, located concentrically and radially further outwards from the first annular rotor element 5 and non-rotatably connected to the first rotor element 5. The stator 3 comprises windings 11, 12, 13, each assigned to one of the three phases of a three-phase system, which repeat cyclically around the circumference of the stator 3. A radial air gap lies between the first, inner, and the second, outer rotor element 5, 6, which is divided into two individual gaps 8, 9 by the stator 2 with its windings 11, 12, 13. Thus, a first radial air gap 8 exists between the stator 3 and the first rotor element 5, and a second radial air gap 9 exists between the stator 3 and the second rotor element 6, as shown in the Fig. 2 , 4and 5 This is evident. Overall, this results in a nested structure of rotor 2 and stator 3.

[0042] In Fig. 1 The rotating field machine 1 is shown without a stator mount, which is in Fig. 3The first rotor element 5 is a disk-shaped support element 15 located in front of the axial end face of the stator 3. The permanent magnets 7a of the first rotor element 5 are cuboid in shape, with their width extending radially away from the shaft 4 and embedded in a laminated core that fills the space between two adjacent permanent magnets 7a. The permanent magnets 7b of the second rotor element 6 are also cuboid in shape, but their width extends approximately into tangential planes of the stator 3. Two permanent magnets 7b form a pair that is V-shaped and embedded in a corresponding V-shaped pocket 17 formed in a laminated core. The permanent magnets 7b of the second rotor element 6 are thus embedded. Together, the permanent magnets 7b form a ring-shaped arrangement in the second rotor element 6.

[0043] On the in Fig. 1At the rear of the rotating field machine, a rotor disk 14 can be seen, to which the second rotor element 6 is rigidly connected, and which is simultaneously rotationally fixed to the motor shaft 4, which also rotationally fixedly supports the first rotor element 5. Thus, the first and second rotor elements 5, 6 are at a fixed angle to each other.

[0044] Furthermore, it shows Fig. 1 The end-face winding sections of the outermost turns of the individual windings 11, 12, 13, each consisting of several wound layers, with the further layers lying beneath the visible ones, are shown. These winding sections run approximately radially. The windings 11, 12, 13 can, for example, be made of flat wire. The two winding ends of each winding are also not shown in the illustration, but protrude axially from the stator 3.

[0045] Fig. 2The nested structure of rotor 2 and stator 3 is illustrated by a longitudinal section, where the section plane runs through the motor axis 19 and the permanent magnets 7a of the first rotor element 5, but is slightly tilted relative to the radial axis of symmetry of the permanent magnets 7a, so that the permanent magnets 7b in the second rotor element 6 are also cut in. It can be seen that the annular rotor elements 5, 6 and the annular stator 3 each have a rectangular cross-section, i.e., they are formed by concentric hollow cylinders.

[0046] The stator 3 comprises a ring-shaped support structure 10, also rectangular in cross-section, made of a ferromagnetic material, for example iron, onto which the windings are wound directly. A first section 13a of a turn of the windings 13 extends axially in the first air gap 8 and transitions into a second section 13b of the turn at the end face of the stator 3, extending in the opposite axial direction in the second air gap 9. The current in a turn thus flows forward in one air gap and back in the other. The winding principle is described in Fig. 4 more clearly recognizable and is described in more detail below. The support structure 10 forms a slotless core of the stator 3.

[0047] The rotor 2 includes additional permanent magnets 16, which are arranged axially in front of the end face of the stator 3, forming an axial gap 23. This ensures that the current-carrying winding sections at the end face are also located within a magnetic field, primarily perpendicular to it, and thus contribute to torque generation. The magnetization of these axial magnets 16 is correspondingly axial. The axial gap 23 further includes a winding head area 20 and spatially accommodates a winding head 22 of the stator 3, as shown by Fig. 5 better recognizable.

[0048] Fig. 3Figure 1 shows the rotating field machine 1 with the aforementioned support element 15, to which the stator 3 with its windings 11, 12, 13 is attached. The attachment is achieved by means of brackets 21, which here are designed as round, pin-like webs extending parallel to the motor axis 19. At one end, the brackets are attached to the support structure 10, and at the other end to the support element 15, for example, by a weld or by screws. Alternatively, the brackets 21 can also be formed by flat webs. The brackets 21 are equidistantly distributed around the circumference. They define the distance between the disk-shaped support element 15 and the support structure 10, within which lies a winding head area 20, where the windings are also connected. The winding ends, which are also electrically connected to each other on this side, are not shown.

[0049] Fig. 4 shows a section of an enlarged radial cross-section of the rotating field machine 1, Fig. 5 a corresponding longitudinal section. The figures illustrate how the individual windings 11, 12, 13 are wound onto the surface of the support structure 10 in the form of a slotless iron core. They thus form air-gap windings. Alternatively, the support structure 10 can have slots in which the individual windings are placed. The stator 3 therefore comprises the windings 11, 12, 13 and the support structure 10. Each winding 11, 12, 13 extends over a circumferential angle of one-third of the pole pitch α, so that each pole pitch α, or each magnetic pole, is assigned one winding 11, 12, 13 of one of the three voltage phases. Fig. 4The three windings are distinguished by different hatching patterns or the absence of hatching. A first winding 11 with light hatching belongs to the first phase, a second winding 12 with dark hatching to the second phase, and a third winding 13 with no hatching to the third phase. These three phase windings 11, 12, 13 lie side by side on the support structure 10 and repeat cyclically around the circumference of the stator 3, so that the third phase winding is followed by another phase winding corresponding to the first phase.

[0050] The first rotor element 5 comprises 10 cuboid permanent magnets 7a, which are equidistantly distributed around the circumference and extend axially with their length and radially with their width. The thickness is parallel to a tangent to the circumference. The areas of the rotor element 5 between the permanent magnets 7a are each shaped like a slice of a pie, so that the outer circumference of the first rotor element 5 is flower-shaped overall. Thus, the width of the first air gap 8 varies around the circumference, with the width being greatest in the center of the permanent magnets 7a and smallest in the center of the intermediate areas. This rotor shape, known per se, contributes to reducing the cogging torque.

[0051] In the second rotor element 6, the V-shaped pockets 17 are clearly visible, into which the cuboid permanent magnets 7b are axially inserted. One permanent magnet 7b1, 7b2 is located in each leg of one of the V-shaped pockets 17, such that their length extends axially and their width is parallel to a tangent to the circumference. The thickness lies on a chord, i.e., it is slightly tilted relative to the radius. The pockets 17 are also equidistantly distributed around the circumference, resulting in a ring-shaped arrangement of the permanent magnets.

[0052] In the first rotor element 5, ten permanent magnets 7a are arranged, and in the second rotor element 6, twenty permanent magnets 7b are arranged, whereby two permanent magnets 7b1, 7b2 belonging to the same pocket 17 form a pair. They are magnetized identically in the direction of their thickness, so that together they form an outer magnetic pole in the second rotor element 6, the flux direction of which essentially passes radially through the second air gap 9. Fig. 4 The magnetization is indicated by the letters N for north pole and S for south pole. In the direction of travel, the magnetization changes from pair 7b1, 7b2 to pair 7b1, 7b2, so that a north and south pole alternately exist in the second air gap 9 around the circumference. Therefore, there are a total of ten external magnetic poles.

[0053] In the first rotor element 5, the magnetization of the permanent magnets 7a is also oriented along their thickness, with the magnetization alternating from permanent magnet 7a to permanent magnet 7a, so that like poles are always oriented towards each other. Their flux is coupled into the respective common intermediate section of the first rotor element 5, which then conducts it via its outer circumference into the first gap 8. Thus, each of these intermediate sections forms an inner magnetic pole, the flux direction of which essentially passes radially through the first air gap 9. Each inner magnetic pole is therefore generated proportionally by the two adjacent permanent magnets 7a. Consequently, a north and south pole alternately exist in the first air gap 8 in the circumferential direction. The first and second rotor elements 5, 6 are arranged in such a rotationally fixed manner relative to each other that each intermediate section is symmetrically opposite a pair of permanent magnets 7b1, 7b2.

[0054] Overall, the rotating field machine 1 shown is therefore 10-pole, i.e., configured with p=5 pole pairs. Accordingly, one pole pitch is 360° / 2p = 36°. A winding 11, 12, 13 thus extends over a circumferential angle of 12°. It should be noted that, within the scope of the invention, any other number of poles or pole pairs is possible. The direction of flux of the magnetic field lines resulting from the magnetization is shown in Fig. 4 also shown. It becomes clear that the field lines of the outer and inner magnetic poles each close via the iron core 10.

[0055] In Fig. 4Furthermore, for illustrative purposes only, a few of the individual turns of the third phase winding 13 are shown, each comprising a first, radially inner winding section 13a and a second, radially outer winding section 13b. The first winding section 13a lies in the first air gap 8, the second winding section 13b in the second air gap 9. The winding wire here, unlike in Fig. 1 and 3 This is exemplified as a round wire. The first section 13a of the winding extends in an axial direction and, at the end face of the iron core 10, transitions into the second section 13b of the winding, which extends in the opposite axial direction. Thus, the two winding sections 13a and 13b lie at the same azimuthal angle.

[0056] At the end face of the iron core 10, the two winding sections 13a, 13b are connected to each other by a third winding section 13c, see Fig. 5The entirety of all third winding sections forms the winding head 22. The arrows in Fig. 5 indicate the direction of flow of the permanent magnetic fields. As already explained above. Fig. 4As explained, the magnetic field direction of the poles in the first and second air gaps 8, 9 is radially opposite. The turns of the stator windings 11, 12, 13 are oriented relative to the field direction of the permanent magnets 7a, 7b such that the magnetic flux strikes most of the windings perpendicularly. This is true at least for the first and second winding sections 13a, 13b, meaning that the stator current is also perpendicular to the magnetic flux in these sections. Thus, only the portion of the winding wire formed by the third winding section 13c, i.e., the winding head 20, is not perpendicular to the magnetic field. Due to the inventive design of the stator 2 and rotor 3, the length of this winding section 13c is minimized, with the length being essentially determined by the distance between the first and second air gaps 8, 9.

[0057] How Fig. 5Furthermore, the figure shows that an additional permanent magnet 16 is located axially in front of the third winding section 13c, so that the third winding section is also located in a magnetic field acting at right angles and thus contributes to torque generation. The additional permanent magnets 16 also allow the radial thickness of the second rotor element 6 to be reduced, and higher rotational speeds can be achieved because the induced voltages are greater. Fig. 5 Furthermore, at the axial ends of the first rotor element 5, the view of the inner circumferential surface 18 of the stator 3 is revealed, so that the respective outer edges of the axially parallel first winding sections 13a directed towards the shaft 4 are visible.

[0058] Electrically, the windings 11, 12, 13 of the different electrical phases of the three-phase system can be connected in a star or delta configuration, as is common in the prior art. The windings assigned to the same phase can be connected in series or in parallel. Each turn physically corresponds to a current-carrying conductor loop in a permanent magnetic field, which in turn generates an electromagnetic field. Since the sinusoidal currents in the windings of the different phases are each 120° out of phase, the entirety of all windings 11, 12, 13 generates a stator field with poles that also alternate locally in the circumferential direction. Because the current in a winding 11, 12, 13 also changes sinusoidally over time, the stator field rotates at the frequency of the current and exerts a torque on the two cylindrical rotor elements 5, 6.

[0059] To adjust the rotational speed of the rotating field machine 1 according to the invention, the windings 11, 12, 13 can also be supplied by a frequency converter, which accordingly provides three output voltages offset by 120°. With such a frequency converter, for example with a DC link, the rotating field machine 1 can also be operated on an AC power supply.

[0060] In the rotating field machine of the example, which is not part of the invention, the windings 11, 12, 13 are designed without step reduction and therefore do not overlap in the circumferential direction. According to the invention, however, this is the case.

[0061] According to another embodiment not shown, both the first and the second rotor element 5, 6 can be attached to the rotor disk 14.

[0062] According to another embodiment not shown, the cross-sectional shape of the first and second rotor elements 5, 6 and the support structure 10 can be round or elliptical, so that the third winding sections 13c located in the winding head area 20 are also penetrated at right angles by the magnetic field.

[0063] According to yet another alternative design variant, the rotating field machine can be a generator, for example a turbine. Reference symbol list

[0064] 1 Rotating field machine 2 Rotor 3 Stator 4 Shaft 5 First rotor element 6 Second rotor element 7a Permanent magnets in the first rotor element 7b Permanent magnets in the second rotor element 8 First gap 9 Second gap 10 Support structure 11 First winding 12 Second winding 13 Third winding 14 Rotor disk 15 Carrier element 16 Axial magnet 17 Pockets for permanent magnets 18 Inner circumferential surface of the stator 19 Shaft of rotation, motor shaft 20 Winding head area 21 Mounting bracket, spacer 22 Winding head 23 Axial gap

Claims

1. Three-phase induction machine (1) with a rotor (2) comprising a first annular rotor element (5) with permanent magnets (7a), and with a stator (3) having individual windings (11, 12, 13) made of coils, respectively assigned to one of three phases of a three-phase system and repeating periodically in the circumferential direction of the stator (3), wherein there is a first radial air gap (8) between the stator (3) and the first rotor element (5), and the rotor (2) comprises a second annular rotor element (6) with permanent magnets (7b) that is concentric with the first rotor element (5) and located radially further out, the second annular rotor element (6) having a torque-proof connection to the first rotor element (5) and having a distance to the stator (3) forming a second radial air gap (9), wherein a first section (13a) of a coil of the windings (11, 12, 13) extends in the first air gap (8) in one axial direction and, on the face end of the stator (3), in its further course continues into a second section (13b) of the coil that is radially offset to the first section (13a) and that extends in the second air gap (9) in the opposite axial direction, characterised in that the first and second coil sections (13a, 13b) are azimuthally offset relative to each other so that the coils of directly adjacent windings (11, 12, 13) overlap, and in that the windings (11, 12, 13) being wound onto a massive, not hollow annular supporting structure (10) of the stator (3) which consists of a non-magnetic material, in particular plastic, or in that the windings (11, 12, 13) are self-supporting, in particular made of an dimensionally stable flat wire or a backed winding wire.

2. Induction machine (1) according to claim 1, characterised in that the rotor elements (5, 6) and the stator (3) respectively comprise a rectangular cross-section.

3. Induction machine (1) according to claim 1, characterised in that the stator (3) comprises a circular or oval cross-sectional shape and that the two rotor elements (5, 6), viewed in cross-section, merge into each other in that the first and second air gaps (8, 9) merge in an arc-like manner into a joint axial air gap.

4. Induction machine (1) according to one of the preceding claims, characterised in that the rotor (2) comprises additional permanent magnets (16) in the axial direction in front of the face end of the stator (3).

5. Induction machine (1) according to one of the preceding claims, characterised in that the supporting structure (10) comprises grooves in its surface facing the first and / or second air gap (8, 9), in which winding wires of the windings (11, 12, 13) lie.

6. Induction machine (1) according to one of the preceding claims, characterised in that the windings (11, 12, 13), in particular the flat wire, are made of a ferromagnetic material.

7. Induction machine (1) according to one of the preceding claims, characterised in that the coil sections (13c) located at the face end of the stator (3) consist of a material that conducts electricity better than the first and second coil sections (13a, 13b).

8. Induction machine (1) according to at least one of the preceding claims, characterised in that the flow direction of the magnetic poles in the first and second air gap (8, 9) faces radially in the same direction.

9. Induction machine (1) according to one of the preceding claims, characterised in that the coils of the same winding (11, 12, 13) respectively lie on top of each other in several layers, wherein the coils of adjacent windings (11, 12, 13) in different layers are offset relative to each other so that the adjacent windings (11, 12, 13) overlap in the circumferential direction.

10. Induction machine (1) according to one of the preceding claims, characterised in that the first and second rotor elements (5, 6) have a torque-proof connection to a shaft (4) or a rotatable component of a driven load machine or a driving turbine.

11. Induction machine (1) according to one of the preceding claims, characterised in that the first rotor element (5) is mounted directly on a shaft (4) and the second rotor element (6) being mounted on a rotor disc (14) having a torque-proof connection to the shaft (4), or in that the first and / or second rotor element (5, 6) is mounted on a rotor disc (14), in particular that the rotor disc is a part of a pump impeller.

12. Induction machine (1) according to one of the preceding claims, characterised in that the supporting structure (10) is secured by means of support elements (24) on a stationary, in particular disc-shaped carrier (15).

13. Induction machine (1) according to one of the preceding claims, characterised in that the first and second gaps (8, 9) have different gap widths.

14. Induction machine (1) according to one of the preceding claims, characterised by being a drive motor, in particular for a rotary pump.