Stator for an electrical machine and electrical machine

Abstract

A stator for an electrical machine comprises slots (2) between which teeth (3) are formed, and at least three phases (A, B, C), wherein each phase comprises two phase windings (A1, A2), each designed as a distributed winding. Each phase winding (A1, A2) covers only part of the circumference of the stator and comprises at least two groups of coils, wherein at the boundary to another phase winding of the same phase, the coils overlap in such a way that in at least one slot there is a conductor section of each coil of a different phase winding. Furthermore, a control unit (5) is provided which is coupled to the phase windings for controlling them with respective phase currents (IA1, IA2, IB1, IB2, IC1, IC2) in such a way that the number of poles of the stator is adjustable.

Description

[0001] The present invention relates to a stator for an electrical machine and to an electrical machine with the stator and a rotor.

[0002] Since the beginning of the industrial revolution, electric machines have been of great importance, and their role continues to grow today. They play a crucial role in everyday life, for example, in household appliances, robotics, the automotive industry, aerospace, wind turbines, and so on. Compared to internal combustion engines, electric machines are more efficient, more cost-effective, and simpler to construct.

[0003] The two main components of the electrical machine are a stator and a rotor that is mounted so that it can move.

[0004] The stator and rotor typically contain magnetic material. An air gap exists between the stator and rotor. The stator typically has slots facing the air gap and distributed along its circumference. Coils of a winding are inserted into these slots. A distinction is made between two types: tooth-concentrated windings and distributed windings.

[0005] Distributed windings comprise coils that are each wound around at least two teeth and overlap each other in the winding head.

[0006] For example, in a standard three-phase machine, the winding geometry and arrangement determines the number of pole pairs of the stator.

[0007] The number of pole pairs, in turn, has a major influence on the characteristics of the machine. For example, a large number of pole pairs is preferred for high torque and low speed, while a small number of pole pairs is preferable for low torque and high speed.

[0008] The object is to provide a stator for an electrical machine with improved properties. Furthermore, the object is to provide an electrical machine with improved properties.

[0009] The problem is solved in this case by the subject matter of the independent patent claims. Embodiments and advantageous developments are the subject matter of the dependent patent claims.

[0010] In one embodiment, a stator for an electrical machine is specified. The stator comprises slots between which teeth are formed. In one embodiment, the slots and teeth are distributed along the circumference of the stator. The slots and teeth can each be axially extended. In one embodiment, the slots and teeth are arranged facing an air gap formed between the stator and a rotor.

[0011] The stator comprises at least three phases, each phase comprising two phase windings, each formed as a distributed winding, each phase winding covering only a part of the circumference of the stator and each phase winding comprising at least two groups of coils.

[0012] At the boundary to another phase winding of the same phase, the coils overlap in such a way that in at least one slot there is a conductor section of each coil of a different phase winding of the same phase.

[0013] Furthermore, the stator comprises a control unit which is coupled to the phase windings for controlling them with respective phase currents in such a way that the number of poles of the stator is adjustable.

[0014] In one embodiment, the control unit is designed to generate the phase currents in the conductor sections of the coils of different phase windings of the same phase located in the at least one slot such that they have the same amplitude and a phase shift of 0 degrees or 180 degrees depending on the set number of poles.

[0015] If the control unit generates the phase currents of the same phase so that they have no phase shift from each other, then the stator winding generates a four-pole magnetic field in the air gap. If the control unit generates the phase currents of the same phase so that they have a phase shift of 180 degrees from each other, then the stator winding generates a two-pole magnetic field in the air gap.

[0016] In one embodiment, the coils overlap at the boundary to another phase winding of the same phase in such a way that in at least two adjacent slots there is a conductor section of each coil of a different phase winding.

[0017] In one embodiment, the distributed windings are realized in such a way that the coils are each wound around at least two teeth of the stator.

[0018] In one embodiment, each group of coils covers one magnetic pole.

[0019] In one embodiment, the control unit is designed such that an individual phase current (IA1, IA2, IB1, IB2, IC1, IC2) can be generated for each phase winding of each phase.

[0020] In one embodiment, each phase winding covers exactly half the stator circumference.

[0021] Alternatively, each phase winding covers less than half of the stator circumference.

[0022] In one embodiment, the coils of the coil groups of each phase winding each form a two-layer winding.

[0023] In one embodiment, an electric machine is provided that comprises a stator described above, as well as a rotor movably mounted relative to the stator. The stator is preferably fixed to the housing. The rotor is mounted such that it preferably rotates about an axis.

[0024] In one embodiment, the rotor comprises at least one of the following: permanent magnet rotor, reluctance rotor, current-excited rotor, asynchronous rotor.

[0025] In one embodiment, the electrical machine comprises at least one of the following: radial flux machine, axial flux machine, linear machine, synchronous machine, asynchronous machine.

[0026] Further details and configurations are explained in more detail below using several exemplary embodiments and drawings. These show: Fig. 1a and Fig. 1b an embodiment of a stator according to the proposed principle with one phase winding each, Fig. 2 an embodiment of a stator according to the proposed principle with two phase windings of one phase, Fig. 3 an embodiment of a phasor diagram of stator currents, Fig. 4 an embodiment of the magnetomotive force, Fig. 5a and Fig. 5b an embodiment of a stator according to the proposed principle with one phase winding each, in two-pole operation, Fig. 6 an embodiment of a stator according to the proposed principle with two phase windings of one phase, in two-pole operation, Fig. 7 an embodiment of a phasor diagram of stator currents, Fig. 8a Embodiment of a stator according to the proposed principle with two phase windings of one phase in two-pole operation and Fig. 8b the equivalent two-pole winding configuration, Fig. 9 an embodiment of the magnetomotive force, Fig. 10 an embodiment of the magnetomotive force, Fig. 11 an embodiment of a stator according to the proposed principle for a four-pole, five-phase machine, Fig. 12 an embodiment of a phasor diagram of stator currents, Fig. 13 an embodiment of the magnetomotive force, Fig. 14 an embodiment of a stator with a winding according to Fig. 11, but in two-pole operation, Fig. 15 an embodiment of a phasor diagram of stator currents, Fig. 16 an embodiment of the magnetomotive force for the stator according to Fig. 15, Fig. 17 an embodiment of the magnetomotive force of the stator in operation with two pole pairs Fig. 18 an embodiment of all phase currents of a three-phase machine according to the proposed principle in four-pole operation, Fig. 19 an embodiment of all phase currents of a three-phase machine according to the proposed principle in two-pole operation, Fig. 20 an embodiment of an electrical machine according to the proposed principle, Fig. 21 to 24 each show embodiments of a rotor of an electrical machine according to the proposed principle.

[0027] Fig. 1a and Fig. 1b shows an embodiment of a stator 1 for an electrical machine. The stator 1 comprises slots 2, between which teeth 3 are formed. The slots 2 and the teeth 3 are evenly distributed along the circumference. Three phases A, B, and C are provided. Each phase comprises two phase windings, each configured as a distributed winding and controlled separately with respective phase currents. Each phase winding comprises two groups of coils.

[0028] Fig. 1a shows two groups of coils of the first phase winding A1 of phase A. Fig. Figure 1b shows two groups of coils of the second phase winding A2 of phase A. The arrows indicate the current direction in the coils. In addition, + indicates that the current flows into the plane of the drawing, and - indicates that the current flows out of the plane of the drawing. IA1 denotes the phase current of the first phase winding A1 of phase A. IA2 denotes the phase current of the second phase winding A2 of phase A.

[0029] Fig. Figure 2 shows the stator 1 with the complete windings of phase A, which include both phase windings A1, A2, which are shown in the Fig. 1a and Fig. 1b and have already been explained.

[0030] It can be seen that the phase winding of phase A of a conventional three-phase, four-pole machine is divided into two phase windings, each of which covers only half the circumference of the stator. Each phase winding comprises two coil groups. Where the two different phase windings adjoin, a conductor section of each coil of a different phase winding is arranged in at least two adjacent slots.

[0031] The two phase windings A1, A2 of phase A are supplied with two independently generated phase currents.

[0032] This winding topology allows for different numbers of poles to be generated. The four-pole operating mode is explained first.

[0033] If the two phase currents IA1 and IA2 of phase A are equal, so that IA1 = IA2 = IA, the resulting distribution of the magnetomotive force is identical to that of a conventional three-phase four-pole machine. This is also shown by the current arrows in Fig. 2. It can be seen that the current direction changes four times along the air gap to which the slots face.

[0034] In the Fig. 1a, Fig. 1b and Fig. 2 shows only the winding of phase A. The windings of phases B and C are constructed in the same way, but are shifted by two slots and four slots, respectively.

[0035] In order to generate a four-pole magnetic field in the air gap, the proposed winding should be supplied with a dual three-phase current system, where the two currents of each phase IA1, IA2; IB1, IB2 and IC1, IC2 are in phase, as shown in Fig. 3 using a phasor diagram.

[0036] The phase currents of phases A, B and C are described by the following equations: IA1=IA2=I cos(wt) IB1=IB2=I cos(wt−2π3) IC1=IC2=I cos(wt+2π3)

[0037] The distribution of the magnetomotive force for this four-pole operating mode is shown in Fig. 4. The upper half of the Fig. Figure 4 shows the magnetomotive force over the angle from 0 to 2 pi, while the lower half of the figure shows the harmonics of the magnetomotive force, each normalized.

[0038] The two-pole operating mode is explained below.

[0039] In this case, the phase currents of each phase have the same amplitude but opposite signs. Thus, IA1 = -IA2, IB1 = -IB2, and IC1 = -IC2.

[0040] Thus, change as in Fig. 5a, the currents and the magnetomotive force of the first phase winding change their signs. However, the signs remain the same for the second phase winding, as shown in Fig. 5b shown.

[0041] Fig. Figure 6 shows the distribution of currents in the coils for this two-pole operating mode and Fig. Figure 7 shows the phasor diagram of the stator currents. Here, the opposite polarity of the two phase currents of the same phase is clearly visible.

[0042] Fig. Figure 8a shows the current linkage distribution for phase A. It shows that in slots located at 0 degrees and 180 degrees, the number of turns per coil is 4 Nwi. Where 4 is the total number of coils at a given position and Nw is the number of turns per coil. Due to the opposite polarity of the coils, the current linkage is zero at 90 degrees and 270 degrees, respectively.

[0043] For a better understanding, Fig. 8b shows the equivalent two-pole winding for phase A. It becomes clear that with the proposed four-pole winding, a two-pole winding can be simulated in two-pole operation.

[0044] The distribution of the magnetomotive force for this two-pole operating mode is shown in Fig. 9. The upper half of the Fig. Figure 9 shows the magnetomotive force over the angle from 0 to 2 pi, while the lower half of the figure shows the harmonics of the magnetomotive force, each normalized.

[0045] The proposed winding can be operated not only in the four-pole operating mode or in the two-pole operating mode, which are both single-pole operating modes.

[0046] In addition, another operating mode is possible, namely a dual-pole operating mode.

[0047] For this purpose, the phase currents are generated according to the following regulations: IA1=ki2 I1 cos(w1t)+ki2 I2 cos(w2t) IB1=ki1 I1 cos(w1t−2π3)+ki2 I2 cos(w2t−2π3) IC1=ki1 I1 cos(w1t+2π3)+ki2 I2 cos(w2t+2π3) IA2=−ki1 I1 cos(w1t)+ki2 I2 cos(w2t) IB2=−ki1 I1 cos(w1t−2π3)+ki2 I2 cos(w2t−2π3) IC2=−ki1 I1 cos(w1t+2π3)+ki2 I2 cos(w2t+2π3)

[0048] Each phase current equation comprises two components that are added together so that the respective currents overlap.

[0049] The first component with index 1 generates the first pole pair with p1=1, while the second component with index 2 generates the second pole pair p2=2.

[0050] I1 and I2 denote the amplitudes of the components of the phase currents assigned to the respective pole pairs.

[0051] The parameters ki1 and ki2 define the percentage of the respective pole pair components in the total flux density in the air gap. Their values ​​can range between 0% and 100%.

[0052] W1 and w2 denote the angular frequencies of the respective components. They define the angular velocity of the respective flux density components in the air gap.

[0053] Fig. Figure 10 shows the distribution of the magnetomotive force for this dual-pole operating mode with I1=I2 and ki1=50%, ki2=100%. The upper half of the figure Fig. Figure 9 shows the magnetomotive force over the angle from 0 to 2 pi, while the lower half of the figure shows the harmonics of the magnetomotive force, each normalized.

[0054] It is important that in this operating mode the frequency or rotation speed of each pole pair component can be controlled independently of each other.

[0055] As mentioned at the beginning, all previous embodiments of the proposed stator winding with adjustable number of poles are based on a two-layer winding with q=2 and fed by a dual three-phase current system, i.e. six phase currents.

[0056] In other embodiments, the proposed principle can also be applied to multiphase systems with more than three phases.

[0057] Fig. Figure 11 shows an embodiment of a stator winding with five phases with q=2 according to the proposed principle. For the sake of simplicity, only the winding of one phase is shown, namely phase A. Unlike a conventional four-pole winding layout, the proposed principle provides for at least two phase windings per phase, with overlaps of the coils of different phase windings of the same phase being provided, for example, in Fig. 11 at the top of the picture, where the phase windings A1 and A2 overlap again.

[0058] If, as in the phasor diagram of Fig. 12, where two phase currents of the same phase have a zero phase shift from each other, the proposed winding generates a four-pole field in the air gap. Furthermore, the distribution of the magnetomotive force is the same as in a conventional four-pole, five-phase machine with only one phase current per phase.

[0059] The distribution of the magnetomotive force for this four-pole operating mode is shown in Fig. 13. The upper half of the Fig. Figure 13 shows the magnetomotive force over the angle from 0 to 2 pi, while the lower half of the figure shows the harmonics of the magnetomotive force, each normalized.

[0060] As an alternative to this four-pole operating mode, the five-phase machine can also be used according to Fig. 11 can optionally be operated in a two-pole operating mode.

[0061] Fig. Figure 14 shows the current directions in the phase A coils for this two-pole operation of the five-phase machine. The currents of the two phase windings of each phase again have equal magnitudes but opposite signs, as in the three-phase machine in two-pole operation.

[0062] Thus, in the slots containing coils of different phase windings, the resulting current connection is zero, while in the slots containing only coils of the same phase winding, it is again 4 Nw*i.

[0063] Fig. Figure 15 shows the corresponding phasor diagram for the ten phase currents of the five-phase machine with two phase windings each and thus two phase currents per phase.

[0064] The distribution of the magnetomotive force for this two-pole operating mode is shown in Fig. 16. The upper half of the Fig. Figure 16 shows the magnetomotive force over the angle from 0 to 2 pi, while the lower half of the figure shows the harmonics of the magnetomotive force, each normalized.

[0065] The five-phase machine can also be operated not only in single-pole operating modes such as the two-pole or optionally four-pole operating mode described above, but also optionally in a dual-pole operating mode.

[0066] Fig. Figure 17 shows the distribution of the magnetomotive force for this dual-pole operating mode. The upper half of the Fig. Figure 17 shows the magnetomotive force over the angle from 0 to 2 pi, while the lower half of the figure shows the harmonics of the magnetomotive force, each normalized. Again, equal amplitudes of the current components I1=I2 are assumed, as in Fig. 10, and ki1=50% and ki2=100%.

[0067] Fig. Figure 18 shows a graph over time of the six phase currents for the four-pole operating mode of a three-phase machine according to the Fig. 2 to 4.

[0068] Fig. Figure 19 shows a diagram over time of the six phase currents for the two-pole operating mode of a three-phase machine according to the Fig. 6 to 9.

[0069] Fig. Figure 20 shows a block diagram of an embodiment of a three-phase electrical machine with stator 1, rotor 4, and the control unit 5 contained in the stator. It can be seen that the control unit 5 provides the six phase currents IA1, IA2, IB1, IB2, IC1, and IC2.

[0070] The proposed winding topology can be used for various electrical machines such as radial flux machines, axial flux machines, linear machines which can operate synchronously or asynchronously.

[0071] Radial flux machines can be constructed according to the proposed principle with an internal rotor or an external rotor.

[0072] Different rotor types can be used in electrical machines with a stator based on the proposed principle. For example, permanent magnet rotors such as those in Fig. 21, reluctance rotors as in Fig. 22, current-excited rotors as in Fig. 23 or asynchronous rotors as in Fig. 24 shown. List of reference symbols 1 stator 2 grooves 3 tooth 4 Rotor 5 Control unit A-Phase A1 phase winding A2 phase winding B-Phase C-Phase IA1 phase current IA2 phase current IB1 phase current IB2 phase current IC1 phase current IC2 phase current

Claims

[1] Stator for an electrical machine, the stator comprising: - grooves (2) between which teeth (3) are formed, - at least three phases (A, B, C), each phase comprising two phase windings (A1, A2), each formed as a distributed winding, - each phase winding (A1, A2) covers only part of the circumference of the stator, - wherein each phase winding (A1, A2) comprises at least two groups of coils, - wherein at the boundary to another phase winding of the same phase, the coils overlap in such a way that in at least one slot there is a conductor section of each coil of a different phase winding, - a control unit (5) which is coupled to the phase windings for controlling them with respective phase currents (IA1, IA2, IB1, IB2, IC1, IC2) in such a way that the number of poles of the stator is adjustable. [2] Stator according to claim 1, wherein the control unit (5) generates the phase currents (IA1, IA2, IB1, IB2, IC1, IC2) in the conductor sections of the coils of different phase windings located in the at least one slot so that they have the same amplitude and a phase shift of 0 degrees or 180 degrees depending on the set number of poles. [3] Stator according to claim 1 or 2, wherein at the boundary to another phase winding of the same phase, the coils overlap in such a way that in at least two adjacent slots there is a conductor section of each coil of a different phase winding. [4] Stator according to one of claims 1 to 3, wherein the coils are each wound around at least two teeth of the stator. [5] Stator according to one of claims 1 to 4, wherein each group of coils covers a magnetic pole. [6] Stator according to one of claims 1 to 5, wherein the control unit is designed such that an individual phase current (IA1, IA2, IB1, IB2, IC1, IC2) can be generated for each phase winding of each phase. [7] Stator according to one of claims 1 to 6, wherein each phase winding (A1, A2) covers exactly half the stator circumference or less than half the stator circumference. [8] Stator according to one of claims 1 to 7, wherein the coils of the coil groups of each phase winding each form a two-layer winding. [9] Electrical machine with a stator according to one of claims 1 to 8 and a rotor (4) mounted movably relative to the stator (1). [10] Electrical machine according to claim 9, wherein the rotor (4) comprises at least one of the following: permanent magnet rotor, reluctance rotor, current-excited rotor, asynchronous rotor. [11] Electrical machine according to claim 9 or 10, comprising at least one of the following: radial flux machine, axial flux machine, linear machine, synchronous machine, asynchronous machine.

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