Multi-winding group fractional slot synchronous machine

Abstract

Described is an electrical machine (1), in particular a dual three-phase fractional slot synchronous machine, comprising: a stator (3) providing a plurality of slots (5) between a plurality of teeth (6); a first multi-phase winding group (7); a second multi-phase winding group (8), wherein both the first winding group (7) and the second winding group (8) are provided in a star-delta connection and are arranged at least partially in the slots (5) and wound around the teeth (6).

Description

Technical Field

[0001] The invention relates to an electric machine, in particular a dual three-phase fractional slot synchronous machine, which may for example be configured as a generator of a wind turbine. Furthermore, the invention relates to a wind turbine comprising the electric machine and further to a method of manufacturing the electric machine. Background Art

[0002] Conventional electrical machines equipped with fractional slot concentrated windings (FSCW) can offer many advantages over integer slot machines. These advantages can include ease of manufacturing, higher fault tolerance, and shorter end windings. However, non-overlapping windings can result in less sinusoidal MMF (magnetomotive force) distributions with a large number of losses that generate harmonics. This can cause problems for the efficiency of adopting this winding structure in large machines, as these unwanted MMF harmonics can cause losses in the rotor and permanent magnets (PM), which can also cause thermal demagnetization. Alleviating these losses by adopting segmentation of the magnets and the use of higher resistivity materials can add complexity and cost. In addition, the induced harmonics can increase the torque ripple of the machine, which can become particularly undesirable in large offshore wind turbines, where the magnitude of the torque is measured in MNm.

[0003] Traditionally, fractional slot concentrated windings may introduce unwanted MMF harmonics, and many methods have been studied to minimize or mitigate them. The most common practices for minimizing these harmonics may include dual three-phase (or even multi-phase machines), multi-layer windings, and stator shifting.

[0004] A conventional example is a dual three-phase electrical machine. A dual three-phase electrical machine can provide increased fault tolerance and reliability, which can result from a second converter connected to the second winding set. In a fractional slot concentrated winding machine, the second converter can be employed with a 30° phase shift relative to the first converter connected to the first winding set. This configuration has the additional benefit of eliminating the first space winding MMF harmonics, thereby reducing rotor losses and torque ripple.

[0005] As a second conventional example, multi-layer windings are provided in electrical machines. Traditionally, electrical machines have either single-layer windings or double-layer windings (one or two coil sides per slot). In wind power applications, electrical machines acting as generators typically have a single-layer configuration. Unfortunately, FSCW with a single-layer winding may have the largest number of unwanted MMF harmonics. By moving to an increased number of layers, such as double, triple, quad, etc., the amplitude of these harmonics can be greatly reduced. However, this also increases the winding complexity.

[0006] As a third conventional example, stator shifting has been applied. Thus, harmonics are minimized by introducing a second winding set into the stator of the electrical machine with a phase shift selected to minimize the selected harmonics. This may require doubling the number of stator slots so that the new winding set operates at a phase shift of half the slot pitch (mechanical angle).

[0007] However, it has been observed that conventional fractional slot electrical machines generate unwanted harmonics which may hamper the operation of the electrical machine, particularly when operating as a generator.

[0008] Therefore, there may be a need for an electrical machine, in particular a fractional slot synchronous machine, further in particular a dual three-phase fractional slot synchronous machine, in which unwanted harmonics are at least reduced or even avoided. Furthermore, there may be a need for an electrical machine in which losses are reduced and / or torque ripple is reduced and / or harmonics are reduced. Summary of the invention

[0009] This need can be met by the subject matter according to the independent claim. Advantageous embodiments of the invention are described by the dependent claims.

[0010] According to one embodiment of the present invention, an electrical machine is provided, in particular a dual three-phase fractional-slot synchronous machine, comprising: a stator having a plurality of slots arranged between a plurality of teeth; a first multi-phase winding group; a second multi-phase winding group, wherein both the first winding group and the second winding group are arranged in a combined star-delta configuration and are arranged in the slots and wound around the teeth.

[0011] The electrical machine may be configured or connected as a generator. The electrical machine may in particular be utilized as a generator of a wind turbine.

[0012] A fractional-slot synchronous machine is characterized in that the ratio between the number of stator slots per phase and the number of rotor poles is different from an integer but a fraction.

[0013] The electrical machine may include at least two winding sets, but may include more than two winding sets, as long as there is an even number of winding sets, such as four, six, eight, ten or even more winding sets (the winding sets must appear in pairs (i.e., the number of winding sets is an even number), so for example four, six, eight winding sets, etc.). Each winding set may provide at least three phases or an even higher number of phases, such as four phases, five phases, six phases, seven phases or even a higher number of phases.

[0014] At least the teeth of the stator may be made of a magnetically high permeable material. During operation, an oscillating magnetic field may be generated in the teeth of the stator and in the surrounding area. The stator material, in particular the material of the teeth, may be magnetized by means of mobile permanent magnets that may be included in a rotor that rotates relative to the stator.

[0015] The first multiphase winding set may comprise a plurality of coils for each of the plurality of phases, the coils being formed by arranging or winding corresponding wire portions at least partially around the teeth of the stator and arranging the wire portions at least partially in the stator slots. The second multiphase winding set may be completely separated from the first multiphase winding set and the two winding sets may not be (electrically) connected to each other. Providing the first multiphase winding set and the second multiphase winding set may make it possible to even enable the electrical machine to operate if one of the first multiphase winding set or the second multiphase winding set fails. Furthermore, harmonics may be reduced.

[0016] The star-delta connection may be characterized by three corner nodes of a triangle, wherein the corner nodes are electrically connected by at least one coil, in particular two coils. In addition, at least one coil, in particular two coils, may originate from each of the triangle corner nodes. The ends of the coils extending from the triangle corner nodes may provide output terminals for multiple phases of each winding set. Providing both the first winding set and also the second winding set in a star-delta connection may enable the harmonics of the MMF generated when the electrical machine is running to be reduced. In addition, due to this configuration, losses may be reduced.

[0017] According to one embodiment of the invention, the first multiphase winding set provides the same number of phases as the second winding set, in particular three phases or four phases or five phases or even a greater number of phases. Having the same number of phases for both the first winding set and the second winding set allows for a simple winding topology while still reducing losses and / or amplitudes of harmonics. The number of phases may for example be three, four, five, six, seven, eight, nine, or ten, or even a number higher than ten. The number of phases may be selected depending on the specific application.

[0018] According to one embodiment of the present invention, the number of phases provided by each of the first winding group and the second winding group is three, wherein the first three-phase winding group and / or the second three-phase winding group includes: for each phase, a first series-connected coil, one end of which provides an output for the phase, and the other end is connected to or provides a total of three triangular corner nodes (associated with the three phases), wherein the three triangular corner nodes are interconnected via three second series-connected coils, and a second series connection is set for each phase.

[0019] The principles of the invention can be extended to a greater number of multi-phase machines (with a number of phases other than three), however the details of the machine topology differ as the number of phases increases. For example, a double five-phase star-delta wound machine with a number of slots equal to 40 and a number of poles equal to 18 will achieve complete cancellation of the first parasitic harmonic and complete cancellation of the eleventh parasitic harmonic, while maintaining the amplitude of the ninth harmonic for operation. To achieve this, there will again be two identical winding groups, each connected to a different converter, this time with an electrical phase shift of 9 degrees, instead of 15 degrees as in a three-phase machine. In this machine, the second winding group will be circumferentially displaced 81° from the first winding group (as opposed to 75° in a three-phase machine). Each winding group will again include a combined "star-delta" winding configuration, however, since there are five phases, the delta-connected coils will be connected in a five-pointed star shape, as opposed to the triangle shape seen in a three-phase machine. Each series star coil will be connected to a node of a five-pointed star, as seen in a three-phase machine. This principle can be extended to other numbers of phases.

[0020] The first series-connected coils (for each phase of each of the first winding group and the second winding group) may include two or three or four or five or six or seven or eight or nine or ten or even a higher number of coils, such as between 10 coils and 200 coils. The same may apply to the second series-connected coils (for each phase and for each of the first winding group and the second winding group). Three delta angle nodes may be associated with three phases. The first series-connected coils (corresponding to the respective phases of the delta angle nodes) may be connected to each of the three delta angle nodes. Between each pair of delta angle nodes, a respective one of the second series-connected coils is connected. In general, for each winding group, the electrical machine may include three first series-connected coils and three second series-connected coils. For example, for each of the first winding group and the second winding group, three first series-connected coils may be provided, and three second series-connected coils may be provided. Therefore, a simple winding topology may be provided, and losses and / or harmonics may be reduced.

[0021] According to one embodiment of the invention, for each phase, the first series-connected coils and the second series-connected coils comprise two or three or four or five or six or seven or eight or nine or between ten and 100 coils. The number of coils in the first series-connected coils and / or the second series-connected coils may be selected depending on the specific application. Thus, greater flexibility may be provided, in particular supporting proportional increase in capacity and / or rating.

[0022] According to one embodiment of the invention, for each phase, each of the first series-connected coils and the second series-connected coils comprises exactly two coils, which are particularly arranged at circumferentially opposite positions of the stator, particularly circumferentially spaced 180° apart. When the machine is extended to said 48S / 20P, the rotational symmetry will be 4, so the series-connected coils will be positioned circumferentially around the stator at intervals of 90°.

[0023] Generally speaking, the offset angle by which the series-connected coils are spaced apart in the circumferential direction is 180° mechanical angle divided by the repetition (number of times) of the 24S / 10P combination, i.e. for 48S / 20P, the offset angle is 180° / 2=90° and so on.

[0024] When two coils are provided for the first series connection and / or the second series connection, the winding topology can be simplified and the performance can be improved.

[0025] The stator may provide an entire circumference forming a ring. The stator may span a 360° circumference. The stator may be configured as a non-segmented or segmented stator. The slots may be spaced apart from each other in a circumferential direction, and the conductor portions of the first winding set and the second winding set may be at least partially arranged in the slots. The two coils arranged in relative positions may at least substantially present mirror symmetry. As an alternative characterization, the two coils may be arranged in a point-symmetrical manner, wherein the point-symmetrical center may be at the axis of rotation of the rotor, or may be defined as the symmetry or rotational symmetry center of the stator.

[0026] According to one embodiment of the present invention, at least one coil of the first series-connected coils and / or the second series-connected coils, in particular all coils, are formed by winding (part of) the wire of the first winding group or the second winding group around two circumferentially adjacent teeth, with slots between the teeth.

[0027] Thus, advantageously, the first winding group and the second winding group can be arranged at the stator in an easy manner. In the slots between circumferentially adjacent teeth, around which the conductor sections of the first winding group or the second winding group are wound, at least one (in particular two) conductor sections of the other of the first winding group or the second winding group can be arranged. In particular, two conductor sections of the other of the first winding group or the second winding group can be arranged in the slots between circumferentially adjacent teeth. Thus, the winding of the first winding group and the second winding group can be offset by only one slot in the circumferential direction in a corresponding, in particular identical manner.

[0028] In adjacent slots, wire sections of the first winding set can alternate with wire sections belonging to the second winding set.Thereby, the first winding set and also the second winding set can be suitably accommodated in the slots of the stator.

[0029] According to one embodiment of the present invention, in each of the plurality of slots, two conductors both belonging to the same winding group are arranged, wherein the two conductors belong to the same or different phases.

[0030] In each of the plurality of slots, one conductor portion of the same winding set may belong to a coil in the first series connection of coils, and another conductor portion (of the same winding set) may belong to a coil in the second series connection of coils. Thus, a simple winding topology may be provided, which may also reduce losses and / or harmonics.

[0031] According to one embodiment of the invention, in two adjacent slots, the two conductors belong to the same phase, and in the next two adjacent slots, the two conductors belong to different phases. Thus, two winding groups can appropriately accompany the slots of the stator.

[0032] According to one embodiment of the present invention, the electric machine further comprises: a first converter having an input for each of a plurality of phases, the input being connected to an output of the phase of the first winding set; and a second converter having an input for each of the plurality of phases, the input being connected to an output of the phase of the second winding set.

[0033] The output of the respective phase of the first winding set may be the end of the first series-connected coil. Similarly, the output of the respective phase of the second winding set may be formed by the first series-connected ends of the second winding set.

[0034] The first converter and the second converter can be controlled by providing and operating a controller, which particularly includes a first control part and a second control part. Each control part can generate, for example, gate drive signals and supply these gate drive signals to the gates of controllable switches (such as transistors or power transistors) respectively included in the first converter and the second converter.

[0035] By providing a corresponding controller and a first converter and a second converter, and connecting the first converter and the second converter to the output ends of the first winding group and the second winding group respectively, appropriate control of the electrical machine can be achieved, in particular, appropriate control of the output voltage and / or output power and / or output reactive power and / or output frequency of the electrical machine.

[0036] Each of the first converter and the second converter may include an AC / DC part (connected to the respective output ends of the first winding group and the second winding group, respectively), a DC link and a respective DC / AC converter part. Thus, it is possible to transform a variable frequency AC power flow into a fixed frequency power flow, which may be supplied to a utility grid, for example, via one or more wind turbine transformers and / or one or more wind farm transformers.

[0037] According to one embodiment of the invention, during operation, for each phase, the currents carried in the output ends of the first and second winding sets are electrically phase-shifted by 15° and / or the output ends of the first and second winding sets are physically spaced 75° apart in the circumferential direction.

[0038] According to one embodiment of the present invention, the angle between adjacent star-wound coils and delta-wound coils is 30 mechanical degrees. This provides an electrical phase shift of 150 electrical degrees. Then, one of these coils can be inverted, providing a phase shift of 30 electrical degrees between adjacent star-wound coils and delta-wound coils.

[0039] By operating the winding sets with the indicated phase shifts, a reduction in higher harmonics can be effectively achieved. In particular, the seventh harmonic order amplitude of the harmonics can be significantly reduced. In addition, the seventh harmonic order, the eleventh harmonic order, the thirteenth harmonic order and the seventeenth harmonic order can be effectively reduced. In other embodiments, other harmonic orders can be reduced depending on the number of slots and / or the number of poles and / or the number of phases. The harmonic orders correspond to multiples of the electrical fundamental frequency, which depends on the rotational speed, the number of slots, the number of poles and the number of phases.

[0040] One embodiment of the present invention comprises exactly two winding groups, each individual group being wound in star-delta. The configuration can be extended to include additional winding groups, but they must be introduced in pairs. For example, to extend an embodiment of the present invention to 48S / 20P, two additional winding groups can be introduced, however this will not add new harmonic cancellation effects, but only improve fault tolerance in the event of a converter fault. More simply stated, if an embodiment of the present invention is extended to 48S / 20P, the original 24-slot winding layout will be repeated in a new 24-slot, with the corresponding phases of each winding group being connected in series.

[0041] According to one embodiment of the invention, the number of slots is a multiple of 24. Thus, a large class of electrical machines can be provided and constructed. The electrical machine can, for example, comprise exactly 24 slots or 48 slots, or three times or four times or five times or six times or even up to seven times to 100 times the number of slots. The number of poles can increase linearly with the number of slots.

[0042] According to an embodiment of the invention, the electric machine further comprises a plurality of magnetic poles rotatably supported relative to the stator, wherein the electric machine is configured as a fractional-slot synchronous machine, wherein the ratio between the number of slots and the number of poles in particular amounts to 2.4, wherein the magnetic poles further in particular comprise permanent magnets.

[0043] When the ratio between the number of slots and the number of poles is 2.4, a simple winding topology can be achieved, and the implementation can be simplified and the manufacturing can also be simplified. A ratio of 2.4 is necessary in any three-phase machine using a double star-delta winding. However, for different numbers of phases, the ratio will be different. For example, in a five-phase machine, the ratio must be 20 / 9 (40 slots / 18 poles, 80 slots / 36 poles, 120 slots / 54 poles, etc.).

[0044] According to one embodiment, a wind turbine is provided, comprising an electric machine according to one of the preceding claims, configured as a generator, and a rotor, on which a plurality of rotor blades are mounted and which is coupled to the generator.

[0045] The rotor may be an inner rotor or an outer rotor. Between the stator teeth and the permanent magnets, a gap may be provided.

[0046] It should be understood that features described or applied to an electrical machine, alone or in any combination, may also be provided or applied or employed, alone or in any combination, in a method of manufacturing an electrical machine according to an embodiment of the invention, and vice versa.

[0047] According to one embodiment of the present invention, a method for manufacturing an electrical machine (particularly a dual three-phase fractional-slot synchronous machine) is provided, the method comprising: manufacturing a stator in which a plurality of slots are arranged between a plurality of teeth; winding a first multi-phase winding group and a second multi-phase winding group around the teeth to be arranged in the slots (for example, to form a plurality of coils), and connecting the wires (coils / windings) of the first winding group and the second winding group, respectively, so that both the first winding group and the second winding group are arranged in a combined star-delta configuration.

[0048] For example, winding the first winding set and the second winding set may include bending the wire portions of the first winding set and the second winding set and sliding the bent wire portions through the teeth. In addition, the manufacturing method may include connecting the output ends of the plurality of phases of each of the first winding set and the second winding set to a corresponding converter.

[0049] The aspects defined above and further aspects of the invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to the examples of embodiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 A cross-sectional view schematically illustrating an embodiment of the present invention viewed along an axial direction of an electric machine;

[0051] Figure 2 The first winding group and the second winding group are shown in FIG. Figure 1 A connection diagram of a winding group used in an electrical machine shown in FIG.

[0052] Figure 3 The schematic diagram includes Figure 1 A rolled-up cross-sectional view of a stator of a winding set of an electric machine shown in FIG.

[0053] Figure 4 The diagram shows how the Figure 1 The amplitudes of different harmonic orders generated when an electrical machine is running are shown in the figure. DETAILED DESCRIPTION

[0054] Embodiments of the present invention will now be described with reference to the accompanying drawings. The present invention is not limited to the embodiments shown or described.

[0055] Embodiments of the present invention can employ two harmonic minimization strategies simultaneously. First, embodiments of the present invention employ stator shifting whereby the number of stator slots is doubled (compared to a conventional stator) and a second winding set is introduced into the second slot set. Second, embodiments of the present invention employ a combined star and delta winding in each winding set to provide a secondary phase shift between the coils in series. Thus, the performance of a dual three-phase machine can be simulated. The combination of these two features or techniques can successfully eliminate at least two unwanted harmonic components as have been observed in conventional systems.

[0056] Figure 1 The electric machine 1 schematically illustrated in a cross-sectional view viewed in the axial direction 2 comprises a stator 3, which is provided with a plurality of slots 5 between a plurality of teeth 6. The electric machine 1 further comprises a first multi-phase winding set 7, which comprises conductor sections providing three phases A, B, C. The conductor sections of the first winding set 7 are at least partially arranged in the slots 5 and wound around the teeth 6, wherein the winding sections belonging to the A phase of the first winding set are marked with reference symbol A1. The conductor sections of the first winding set belonging to the B phase are marked with reference symbol B1, and the conductor sections belonging to the C phase of the first winding set are marked with reference symbol C1.

[0057] Furthermore, the electric machine 1 comprises a second multi-phase winding set 8, in particular a three-phase winding set, wherein the conductor portions of the second winding set 8 are at least partially arranged in the slots 5 and are wound around the teeth 6 of the stator 3. The conductor portions of the second winding set belonging to the A phase are marked with reference symbol A2, the conductor portions belonging to the B phase are marked with reference symbol B2, and the conductor portions of the second winding set belonging to the C phase are marked with reference symbol C2.

[0058] The electric machine 1 further comprises a plurality of magnetic poles 9 which are mounted at the rotor 10 and are thus rotatably supported relative to the stator 3. In the illustrated embodiment, the plurality of magnetic poles 9 are configured as permanent magnets. The rotor 10 on which the magnets 9 are mounted is rotatably supported so as to allow rotation about the rotation axis 2 which is also the rotational symmetry axis of the electric machine 1.

[0059] Figure 1 The electric machine shown in the figure includes 24 slots 5 and 10 poles 9, which are abbreviated as 24S / 10P. Figure 1 The electric machine illustrated in FIG. 1 is configured as a fractional-slot synchronous machine having two winding sets and providing three phases for each winding set.

[0060] Figure 1 The electric machine 1 illustrated in a schematic cross-sectional view in FIG. 1 may be comprised in a wind turbine according to an embodiment of the invention. In this case, the rotor 10 may be mechanically coupled to a hub on which a plurality of rotor blades are mounted.

[0061] exist Figure 1 In the embodiment, for each phase of the first winding group (i.e., phases A1, B1, C1), four coils are provided, wherein the reference symbol Y indicates a first series-connected coil (or star series-connected) and the coil indicated by the reference symbol Δ indicates a second series-connected coil (or delta series-connected), as will be explained in more detail below.

[0062] exist Figure 1 In the electric machine illustrated in FIG. 1 , the number of slots is 24. In other embodiments, the number of slots may be a multiple of 24. Furthermore, in the illustrated embodiment, ten magnetic poles 9 are mounted on the rotor 10. Therefore, the ratio between the number of slots (which is 24) and the number of poles (which is 10) reaches 2.4.

[0063] Figure 2 The circuit diagram or connection diagram of the winding set 7 is shown, and the winding set 7 can be used as Figure 1 The first winding group 7 in the electrical machine, or can also be used as Figure 1 The second winding group 8 of the electric machine 1 shown in FIG. Figure 1 The electrical machine 1 shown in the figure comprises two winding groups, which are Figure 27 for the exemplary winding set 7.

[0064] In particular, the first multi-phase winding set 7 provides the same number of phases as the second winding set 8, i.e. Figure 1 , 2 In the embodiment shown in the figure, each of the first winding group and the second winding group provides three phases. For each of the phases A, B, C, in particular for the phases A1, B1, C1 of the first winding group, the first winding group comprises a first series-connected coil 11, one end 12 providing an output for the phase A, and the other end Δ1 connected to or providing a triangle angle node Δ1 of a total of three triangle angle nodes Δ1, Δ2, Δ3, which are associated with the three phases A, B, C. The three triangle angle nodes Δ1, Δ2, Δ3 are interconnected via three second series connections 12, 13, 14, wherein one second series connection is provided for each phase A, B, C. In particular, for the A phase, a second series connection 12 is provided, for the B phase, a second series connection 13 is provided, and for the C phase, a second series connection 14 is provided.

[0065] Similarly, as for phase A, for phase B, a first series connection 15 is provided, one end 16 provides an output for this phase B, and the other end Δ2 is connected to or provides a triangle angle node Δ2 of a total of three triangle angle nodes. In addition, similarly, for phase C, a first delta connection coil 17 is provided, one end 18 provides an output for this phase, and the other end Δ3 is connected to or provides a triangle angle node Δ3 of the three triangle angle nodes.

[0066] In the illustrated embodiment, each of the first series-connected coils 11, 15, 17 includes exactly two coils. In particular, the first series-connected coil 11 for phase A includes coils A-Y1 and A-Y2. The first series connection 15 for phase B includes coils B-Y1 and B-Y2, and for phase C, the first series connection 17 includes coils C-Y1 and C-Y2. In addition, all second series connections 12, 13, 14 also include exactly two coils, that is, for phase A, the second series connection 12 includes coils A-Δ1 and A-Δ2. For phase B, the second series-connected coil 12 includes coils B-Δ1 and B-Δ2. For phase C, the second series connection 14 includes coils C-Δ1 and C-Δ2.

[0067] As will be explained in more detail below, the two coils of each of the series connections 11, 15, 17, 12, 13, 14 are arranged opposite to each other in the assembled stator 3. For example, for phase A of the first winding group, Figure 1 The electrical machine 1 shown in the figure comprises two Y coils (particularly A-Y1 and A-Y2 (see Figure 2)), they are arranged relative to each other so that the rotation axis 2 can be used as a point symmetry center. The two Y coils are spaced 180° apart along the circumference (i.e., in the circumferential direction 20). In addition, for the A phase of the first winding group, Figure 1 The electrical machine 1 shown in the figure comprises two Δ coils (particularly A-Δ1 and A-Δ2 (see Figure 2 )), the two delta coils are arranged opposite to each other so that the rotation axis 2 can be used as a point symmetry center. The two delta coils are spaced 180° apart along the circumference (ie in the circumferential direction 20).

[0068] The output terminals 12 , 16 , 18 of the three phases A, B, C are connected to a converter 22 . Figure 2 This is applicable to the first winding set 7 and the second winding set 8 .

[0069] Figure 3 Schematically illustrated Figure 1 The stator 3 is shown in an expanded cross-sectional view, with the section line indicated by reference symbol 21, and the stator is composed of stator parts 3a and 3b. Figure 3 In FIG. 1 , stator part 3a is shown above stator part 3b.

[0070] Indicates the output terminals A, B, C for the three first series-connected coils of the first winding set 7 (i.e., the first series connection 11, 15, 17). Figure 3 In the figure, the coils of the first series connection of coils 11, 15, 17 of the first winding group are indicated. Figure 2 The coils of the second series connection 12, 13, 14 are also indicated and labeled with reference symbols as defined in .

[0071] In addition, Figure 3 In the figure, three triangle corner nodes Δ1, Δ2, and Δ3 are indicated. Figure 3 It can be seen from the diagram that for a particular winding set (e.g. Figure 3 For each phase of the first winding group (shown in detail and marked in FIG. 1 ), the first series-connected coils and also all the coils in the second series-connected coils are formed by winding the conductor portion of the corresponding winding group around two circumferentially directly adjacent teeth (for example teeth 6a and 6b), with a slot 5a between the teeth 6a and 6b.

[0072] from Figure 3 It can be further appreciated that in each slot 5 of the stator slots, two conductor portions are arranged such that they both belong to the same winding group. Wire portions of different winding groups are not arranged in the slots.

[0073] The coils of the first (or second) winding group belonging to the first series connection of coils are further marked with a "*" ( Figure 1The coils in the second series connection are indicated by a mark “Y” in the figure, and the coils in the second series connection are further indicated by a mark “Δ” placed in the corresponding slots, and the corresponding wire portions are actually arranged in the corresponding slots.

[0074] from Figure 3 It is further evident from the diagram that the conductor portions belonging to the first winding group are arranged in every other slot, the slots in between being occupied by corresponding conductor portions belonging to the second winding group. Figure 3 It is also apparent that, for example, one of the two wire portions arranged in one of the slots belongs to a coil in the first series connection of coils (marked with a "*" symbol), while the other of the two wire portions belongs to a coil in the second series connection of coils (indicated by a Δ symbol).

[0075] from Figure 3 It is also obvious that, for example, in three adjacent slots 5a, 5b, 5c, in one slot (i.e., 5a) of the three slots, two conductor portions belong to the same phase (e.g., to phase C of the second winding group); in the second slot (i.e., 5b) of the three slots, two conductor portions belong to different phases (e.g., to phase A and phase B of the first winding group in slot 5b), and in the third slot of the three adjacent slots, i.e., slot 5c, two conductor portions belong to different phases (e.g., to phase C and phase A of the second winding group). Thus, the first slot 5a, the second slot 5b, and the third slot 5c are arranged circumferentially spaced apart in this order.

[0076] exist Figure 3 In the embodiment, it is also indicated that during operation, for each phase, the current transmitted in the output of the first winding group and the second winding group is electrically phase-shifted by 15° (θe=15°), and / or the output of the first winding group and the second winding group is physically spaced 75° (θm=75°) apart in the circumferential direction. In addition, there is an electrical phase shift of 150° between the terminals or outputs of adjacent star and triangle coils in the same phase, and there is a mechanical phase shift of 30° between the outputs or terminals of adjacent star and triangle coils in the same phase.

[0077] Reference again Figure 1 According to one embodiment of the invention, the electric machine 1 further comprises a first converter 22a having an input 23a for each of the plurality of phases, the input being connected to the output terminals 12a, 16a, 18a of the first winding set 7 for the phase. The electric machine 1 further comprises a second converter 22b having an input 23b for each of the plurality of phases, the input being connected to the output terminals 12b, 16b, 18b of the second winding set for the phase. The output terminals 12a, 16a, 18a and 12b, 16b, 18b correspond to Figure 2 The output ends 12, 16, 18 of an exemplary winding set 7 are illustrated in FIG.

[0078] Embodiments of the present invention combine the practice of stator shifting with the use of star-delta windings to eliminate two unwanted parasitic winding MMF harmonics. The star-delta windings are able to emulate the performance of a dual three-phase machine, eliminating the first spatial harmonic. Then, through the practice of stator shifting, a second winding set is introduced, for which the second converter is operated with a 15° phase shift, thereby eliminating the second undesirable superharmonic.

[0079] Figure 4 The observed amplitudes of a conventional 12S / 10P three-phase electrical machine are illustrated in a coordinate system having an abscissa 24 indicating harmonic orders and an ordinate 25 indicating amplitudes, wherein the observed amplitudes are marked with reference symbols 27a, 28a, 29a, 30a, 31a and 32a. In addition, a 12S / 10P dual three-phase was investigated and the corresponding amplitudes 27b, 28b, 29b, 30b, 31b and 32b were observed. Finally, the observed amplitudes of different harmonics of a 24S / 10P dual star-delta electrical machine according to one embodiment of the invention are indicated with reference symbols 27c, 29c, 30c, 32c.

[0080] It can be observed that the electrical machine according to the embodiment of the invention does not exhibit any significant amplitude for harmonic orders 1, 7, 11, 13, 17. In contrast, the conventional electrical machine exhibits significant harmonic order amplitudes for harmonic orders 7 and 17. Therefore, in particular by reducing the amplitude of harmonic orders 7 and 17, the losses of the system can be reduced, the lifetime can be extended, and the performance can also be improved.

[0081] According to the embodiments of the present invention, the following advantages can be provided:

[0082] Reduced rotor hysteresis and eddy current losses and reduced permanent magnet eddy current losses and / or reduced torque ripple.

[0083] In particular, successfully eliminating both one parasitic subharmonic and two parasitic superharmonics (particularly harmonics 1, 7 and 17) can reduce losses in both the rotor core and the permanent magnets. The first harmonic can be the main contributor to rotor losses, and thus machine efficiency can be improved by eliminating this harmonic alone. An additional effect of eliminating superharmonics (such as harmonic 17) is to further reduce rotor losses and significantly reduce permanent magnet eddy current losses. By reducing permanent magnet eddy current losses, not only can machine efficiency be improved, but the risk of thermal demagnetization can also be reduced.

[0084] The reduced torque interaction between slots and poles (and due to the increased lowest common multiple in the FSCW design) initially reduces cogging torque. This, coupled with the elimination of unwanted MMF harmonics, also serves to further reduce torque ripple.

[0085] The electrical machine may be utilized or configured in particular as a wind turbine generator, which may be used in particular in an offshore wind farm. Both stator shifting and star-delta winding may be used independently to minimize unwanted harmonics. However, embodiments of the present invention include two converters (used in a dual three-phase machine) in a combined and combined manner to utilize both strategies to eliminate one sub-space harmonic and one hyper-space harmonic.

[0086] Embodiments of the present invention provide an n-converter, m-phase star-delta machine, where m represents the number of phases and n represents the number of converters.

[0087] For any machine with "m" phases and "n" converters, there is a set of slot-pole numbers for which harmonic cancellation or damping can be achieved using multi-winding star-delta coils.

[0088] According to one embodiment of the invention, the electrical machine has a number of slots equal to 4·m·n.

[0089] The electrical angle required for harmonic elimination can be given as

[0090]

[0091] According to an embodiment of the present invention, the coil phase shift can be evenly distributed in the electrical space. Therefore, according to an embodiment of the present invention, the modular sum of all electrical phase shifts can comply with the following rules:

[0092]

[0093] According to an embodiment of the present invention, the number of poles may satisfy the following equation:

[0094]

[0095] m represents the number of phases

[0096] n is the number of converters

[0097] p represents the number of pole pairs

[0098] σ represents the required electrical phase shift between the coils

[0099] Ns represents the number of slots.

[0100] An embodiment of the invention provides a 24s / 10p double star-delta machine (thus having 24 slots, 10 poles, and having exactly a first winding set and a second winding set, in particular each winding set providing three phases).

[0101] It should be noted that the term "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Elements described in conjunction with different embodiments may also be combined. It should also be noted that reference symbols in the claims should not be interpreted as limiting the scope of the claims.

Claims

1. An electrical machine (1), in particular a double three-phase fractional slot synchronous machine, comprising: A stator (3) having a plurality of slots (5) disposed between a plurality of teeth (6); A first multi-phase winding group (7); a second multi-phase winding set (8), The first winding set (7) and the second winding set (8) are both arranged in a star-delta connection and are at least partially arranged in the slot (5) and wound around the tooth (6).

2. An electrical machine according to the preceding claim, wherein: The first multi-phase winding set (7) provides the same number of phases as the second winding set (8), in particular three or four or five or six or seven or even more phases.

3. An electrical machine according to one of the preceding claims, wherein: The number of phases provided by each of the first winding set (7) and the second winding set (8) is three, Wherein, the first three-phase winding set and / or the second three-phase winding set include: for each phase, A first series-connected coil (11, 15, 17) provides an output for the phase (A, B, C) at one end (12, 16, 18) and the other end is connected to or provides a triangle angle node (Δ1, Δ2, Δ3) of a total of three triangle angle nodes, wherein the three triangle angle nodes (Δ1, Δ2, Δ3) are interconnected via three second series-connected coils (12, 13, 14), and a second series connection is provided for each phase.

4. An electrical machine according to the preceding claim, wherein: For each phase (A, B, C), the first series-connected coils (11, 15, 17) and the second series-connected coils (12, 13, 14) include two or three or four or five or six or seven or eight or nine or between ten and one hundred coils.

5. An electrical machine according to one of the two preceding claims, wherein: For each phase (A, B, C), each of the first series-connected coils and / or the second series-connected coils comprises exactly two coils (A-Y1, A-Y2), which are particularly arranged at circumferentially opposite positions of the stator, particularly circumferentially spaced 180° apart.

6. Electrical machine according to one of the three preceding claims, wherein: For each phase, at least one coil, in particular all coils (A-Y1) of the first series-connected coils and / or the second series-connected coils are formed by winding a conductor portion of the first winding group or the second winding group around two circumferentially adjacent teeth (6a, 6b), with a slot (5a) between the teeth (6a, 6b).

7. An electrical machine according to one of the preceding claims, wherein In each slot (5) of the plurality of slots, two conductor portions, both belonging to the same winding group (7, 8), are arranged, wherein one of the two conductor portions belongs to a coil in the first series-connected coils (11, 15, 17), and the other of the two conductor portions belongs to a coil in the second series-connected coils (12, 13, 14), wherein the two conductor portions belong to the same phase or different phases.

8. An electrical machine according to the preceding claim, in, In a first slot (5a) of three adjacent slots (5a, 5b, 5c), the two conductor sections belong to the same phase (C2), and / or In a second slot (5b) of the three adjacent slots, the two conductor sections belong to different phases (A1, B1), and / or In a third slot (5c) of the three adjacent slots, the two conductor portions belong to different phases (C2, A2), The first groove, the second groove and the third groove are particularly arranged in this order at intervals along the circumference.

9. The electrical machine according to one of the preceding claims, further comprising: a first converter (22a) having an input (23a) for each phase of a plurality of phases, the input (23a) being connected to an output terminal (12a, 16a, 18a) of the phase of the first winding set (7); A second converter (22b) has an input (23b) for each phase of the plurality of phases, the input (23b) being connected to the output terminal (12b, 16b, 18b) of the phase of the second winding set (8).

10. An electrical machine according to the preceding claim, wherein During operation, the currents carried in the outputs of the first and second winding sets (7, 8) are electrically phase-shifted by 15° for each phase and / or the outputs of the first and second winding sets are physically spaced 75° apart in the circumferential direction.

11. The electrical machine according to one of the preceding claims, further comprising: at least one pair of two further polyphase winding sets; Therein, each of the two further winding sets is provided in a star-delta connection and is arranged at least partially in the slots and is wound around the teeth.

12. An electrical machine according to one of the preceding claims, wherein The number of the slots (5) is a multiple of 24.

13. The electrical machine according to one of the preceding claims, further comprising: A plurality of magnetic poles (9) rotatably supported relative to the stator (5), wherein the machine is configured as a fractional slot synchronization machine, The ratio between the number of slots and the number of poles is 2.

4. Therein, the magnetic pole (9) further particularly comprises a permanent magnet.

14. A wind turbine comprising: The electrical machine according to one of the preceding claims, configured as a generator; A rotor (10) is provided with a plurality of rotor blades mounted thereon and is coupled to the generator.

15. A method for manufacturing an electrical machine (1), in particular a dual three-phase fractional slot synchronous machine, the method comprising: Manufacturing a stator (3) having a plurality of slots (5) disposed between a plurality of teeth (6); Winding a first multi-phase winding set (7) and a second multi-phase winding set (8) around teeth at least partially arranged in the slots (6); Conductive wires of the first winding set and the second winding set are respectively connected so that both the first winding set and the second winding set are arranged in a star-delta connection.

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