System comprising an electric machine and method for manufacturing such a system

Abstract

A system (1), in particular for an aircraft (2), comprises: an electric machine (10) with a stator (100) and a rotor (101) rotatable relative thereto, wherein coils (104) are fixed to a body (108) of the stator (100), power electronics (11) and electrical supply lines (12A-12C), each having an impedance (Z0), wherein at least one of the coils (104) is connected via an impedance element (13, 13A-13F) to one of the supply lines (12A-12C), via which the impedance element (13, 13A-13F) is connected to a terminal (112A-112C) of the power electronics (11), wherein the impedance element (13, 13A-13F) has an impedance (Z1) which is greater than the impedance (Z0) of the supply line (12A-12C). and wherein the impedance element (13, 13A-13F) comprises an electrical conductor (131) which runs at least section by section along the body (108) of the stator (100).

Description

[0001] The present disclosure relates to a system, in particular for an aircraft, and to a method for manufacturing a system.

[0002] Vehicles, especially aircraft, are powered by a wide variety of propulsion systems. Internal combustion engines, such as piston engines or gas turbine engines, enable long ranges and high speeds. In contrast, drive units with one or more electric motors allow the use of sustainably generated energy from a wide range of sources and are often particularly low-maintenance and quiet. Advances in battery and fuel cell technology are constantly expanding the applications of electric drives. Electric generators, as part of the power supply system, can power electric motors and also operate a wide variety of related or independent electrical systems. In this context, the electric motors of the generators can be driven by internal combustion engines powered by conventional or renewable fuels.

[0003] In various applications, such as electrically powered aircraft, at least one electric machine is supplied with electrical current via electrical connecting cables. In these cases, a space-saving arrangement of the electric machine and the power supply can present a challenge.

[0004] Furthermore, there are various applications for electric generators, particularly in the context of the ongoing (partial) electrification of aircraft and the use of hybrid propulsion systems. In these applications, at least one electric machine supplies power via electrical connecting cables to, for example, on-board electronics, electric actuators, or electric drive motors.

[0005] The object of the present invention is to improve a system comprising an electric machine and power electronics (e.g., power supply).

[0006] According to one aspect, a system (particularly for an aircraft) is specified, comprising an electric machine (e.g., in the form of an electric motor) with a stator and a rotor rotatable relative to it, wherein coils of the electric machine are fixed to a body of the stator. The system further comprises power electronics, e.g., in the form of a power supply (particularly including a converter with power transistors), with switching elements (e.g., generating voltage waves), for example, with an inverter, and electrical supply lines, each of which has an impedance (particularly identical to each other). At least one of the coils of the electric machine is connected via an impedance element to one of the supply lines, via which the impedance element is connected to a terminal of the power electronics (e.g., power supply).The impedance element has an impedance greater than that of the supply line. The impedance element comprises an electrical conductor that runs at least partially along the body of the stator (e.g., along an outer and / or an inner surface thereof).

[0007] This is based on the understanding that during the operation of an electric machine, voltage wave propagation and reflections can occur between the power electronics (e.g., power supply), for example, with an inverter, and the electric machine due to rapid switching by the power electronics. These reflections can be significant depending on the quality of the supply lines. Such reflections can lead to accelerated aging or novel damage mechanisms in the electric machine's insulation system, thus reducing its lifespan. To minimize these reflections, it is possible to position the power electronics (e.g., power supply) as close as possible to the electric machine, although this can sometimes present challenges regarding available installation space.In contrast, the proposed solution allows for a more flexible arrangement of the power electronics (e.g., power supply) and simultaneously enables the handling of voltage reflections, resulting in an improved system with an electric machine and power electronics (e.g., power supply). In particular, at least one impedance element can provide overvoltage protection. Furthermore, the described system is based on the understanding that the system's weight can be reduced if the impedance element runs along the stator body, as this can then serve as the core for the inductor. This allows for high inductance without the need for an additional core. The body thus benefits from a dual function. The power electronics can be implemented as, or include, a current source converter (CSC) or a voltage source converter (VSC).It is also possible for the power electronics to receive AC current and AC voltage from a source and then convert them into another form of AC current and AC voltage (AC-AC converter). An inverter, a specific type of converter, is also possible. The housing may contain, for example, iron or be made of it. Each of the stator coils may be connected to one of the supply lines via an impedance element. The impedance element may be, for example, partially, simply, or multiple times wound around at least part of the housing. Several such impedance elements may be used, for example, three.

[0008] The conductor of the impedance element can run around the stator body, at least in sections. This allows for high inductance with low weight and a simple design.

[0009] The conductor of the impedance element can run, at least partially, between at least two of the coils. This allows the impedance element to be used to generate torque in addition to other functions. In this way, the impedance element can serve a dual purpose.

[0010] For example, the coils are wound around a respective winding axis. The conductor of the impedance element can alternatively or additionally be wound around a winding axis. This allows high inductances to be achieved.

[0011] Optionally, the winding axes of the coils are aligned concentrically, parallel, or tangentially to an axis of rotation about which the rotor can rotate relative to the stator. Alternatively or additionally, the winding axis of the impedance element can be aligned concentrically, parallel, or tangentially to the axis of rotation. Furthermore, it is possible for the winding axes of the coils to be aligned concentrically, parallel, or tangentially to the axis of rotation, and for the winding axis of the impedance element to be aligned concentrically, parallel, or tangentially to the axis of rotation, but also in a different orientation than the winding axes of the coils. This allows for a compact arrangement.

[0012] For example, the winding axes of the coils are aligned concentrically to the axis of rotation, and the winding axis of the impedance element is aligned parallel, in particular coaxially, or tangentially to the axis of rotation.

[0013] It can be provided that the body is cylindrical and has two opposing, e.g. parallel, ring-shaped end faces, with the conductor of the impedance element following the ring shape on one or both of the end faces.

[0014] The conductor of the impedance element can run from one of the two end faces to the other. At the second end face, the conductor can describe a semicircle. Then, the conductor can run back to the first end face. Two semicircular conductor sections can be provided at each end face. This allows, in the first order, a cancellation of the magnetic flux, so that an increase in capacitive coupling is possible, independent of the inductance.

[0015] The rotor can have two sub-rotors on either side of the stator coils. Part of the coils can face one sub-rotor, and another part can face the other sub-rotor. The conductor of the impedance element can run, at least partially, between at least two of the coils facing one sub-rotor and at least partially between at least two of the coils facing the other sub-rotor. This allows for the achievement of a particularly high torque.

[0016] The insulation of the impedance element conductor, for example, has a greater thickness than the insulation of the individual coil conductors. This allows even high voltage peaks in the impedance element to be tolerated. Since the impedance element can be positioned more freely than the coils, there is greater flexibility in adjusting the thickness of its insulation.

[0017] The impedance element can be arranged such that an electric current flowing through it generates a magnetic field, which sets the rotor into rotation relative to the stator. Thus, the impedance element can also be used to generate torque.

[0018] It can be arranged that the coils are electrically connected to connection points, with each of the (e.g., three) connection points of the electrical machine being connected via an impedance element to one of the respective supply lines, via which the corresponding impedance element is connected to a respective terminal of the power electronics (e.g., power supply), and wherein the impedance elements each have an impedance (in particular, the same impedance among themselves) which is greater than the impedance of the respective supply line. In this way, a particularly good reduction of the effects of reflections on the electrical machine can be achieved.

[0019] The electric machine can have multi-phase windings with star points.

[0020] For example, the electric machine has several, e.g., three, sub-circuits. Each sub-circuit can include at least one of the coils. The sub-circuits can each extend from one of the connection points of the electric machine to a star point (or several star points). At the star point, several (optionally all) of the several (e.g., three) sub-circuits are electrically connected to each other. The power electronics (e.g., power supply) of this electric machine can have a considerable space requirement, so the described arrangement can be particularly advantageous. The electric machine has, for example, a separate sub-circuit for each of several (e.g., three) phases. For ease of reference, the sub-circuits can also be referred to as phases of the electric machine.

[0021] Each of the sub-circuits (e.g., phase, see above) has an impedance. The impedance of each impedance element can be at least 5% (in particular, at least 20%) of the impedance of the respective sub-circuit. This allows for a substantial reduction of reflections at the beginning of the sub-circuit without requiring the impedance elements to be particularly heavy. For example, the impedance of each impedance element is at least 82% and at most 122% of the impedance of the respective sub-circuit. The impedance of each impedance element can be equal to the impedance of the respective sub-circuit. This allows for a particularly effective reduction of reflections.

[0022] Each of the sub-circuits comprises, for example, several coils connected in series and / or several coils connected in parallel. This allows for the use of a powerful electric machine.

[0023] The impedance elements, for example, have the same impedance to each other. This allows for a symmetrical design.

[0024] For example, the impedance element (or at least one, in particular each of the several impedance elements) comprises at least one coil. In this way, a correspondingly high impedance can be achieved.

[0025] The impedance elements can each be arranged at the corresponding connection point of the electrical machine.

[0026] The rotor has one or more permanent magnets mounted on it. The electric machine is, for example, a permanent magnet synchronous machine.

[0027] The impedance elements lead to the occurrence of overvoltages at the resonant frequency of the respective supply line. By choosing short supply lines, especially less than 1 meter, a high resonant frequency can be achieved, particularly above 1 MHz.

[0028] The power electronics may include an inverter. The inverter may be configured to output an alternating voltage, particularly a three-phase alternating voltage, at the terminals of the power electronics. This enables the operation of a high-performance electric machine.

[0029] The power electronics can be located at a distance from the electric motor. This allows for greater flexibility in the arrangement, for example in an aircraft.

[0030] The system can also include a propeller. The rotor of the electric machine can be coupled to the propeller to drive it, e.g., rigidly connected to it. In this way, thrust and / or lift can be provided for an aircraft.

[0031] According to one aspect, a system, particularly for an aircraft, is specified, in particular according to any of the embodiments described herein, comprising: an electric machine with a stator and a rotor rotatable relative thereto, wherein coils are fixed to a body of the stator, power electronics with switching elements and electrical supply lines, each having an impedance, wherein at least one of the coils is connected via an impedance element to one of the supply lines, via which the impedance element is connected to a terminal of the power electronics, wherein the impedance element has an impedance which is greater than the impedance of the supply line and wherein the impedance element is integrated into the stator.

[0032] According to one aspect, a vehicle, in particular an aircraft, is provided, comprising the system according to any of the configurations described herein. The advantages of the system described herein are particularly evident in a vehicle, especially an aircraft.

[0033] According to one aspect, a method for manufacturing a system (in particular according to any of the embodiments described herein) is specified. The method comprises: providing an electric machine with a stator and a rotor rotatable relative thereto, wherein coils of the electric machine are fixed to a body of the stator; determining the impedance of electrical supply lines via which the coils of the electric machine are connected to power electronics (e.g., a power supply); providing impedance elements for each of the supply lines, each with an impedance greater than the impedance of the respective supply line; and connecting the coils of the electric machine via one of the impedance elements to each of the supply lines, via which the respective impedance element is connected to a respective terminal of the power electronics (e.g., a power supply).(power supply) is connected, wherein the impedance element comprises an electrical conductor which is arranged, at least in sections, along the body of the stator. Regarding the advantages, reference is made to the information above.

[0034] The method may further include determining the impedance of each of several sub-circuits of the electrical machine electrically connected to one or more star points, wherein the impedance elements are provided with a respective impedance which is in particular at least 82% and at most 122% of the impedance of the respective sub-circuit, e.g. not higher and in particular equal to the impedance of the respective sub-circuit.

[0035] Exemplary embodiments are now described with reference to the figures; the figures show: Fig. 1 an aircraft in the form of a fixed-wing aircraft with two electric propulsion units; Fig. 2 a schematic sectional view of a basic structure of a permanent magnet, multiphase electric motor as an internal rotor with power supplies; Fig. 3 a schematic diagram of one of the power supplies of the drive unit according to Fig. 2; Fig. 4 a schematic view of an aircraft system according to Fig. 1 with the power supply according to Fig. 3, impedance elements and an electric machine; Fig. 5 a schematic view of a system for the aircraft according to Fig. 1 with the power supply according to Fig. 3, impedance elements and an electric machine; Fig. 6 a method for manufacturing a system for an aircraft; Fig. 7 a measuring arrangement for measuring the impedances of the system according to Fig. 4; Fig. 8 a body of a stator of the electric motor according to Fig. 2 with a cylindrical lateral surface and an impedance element running along it; Fig. 9 and Fig. 10 a part of the stator of the electric motor according to Fig. 2 with an impedance element mounted on it; Fig. 11 a possible wiring of the coils of the electric motor; Fig. 12 and Fig. 13 a part of a stator for the electric motor according to Fig. 2 with an impedance element mounted on it; Fig. 14 and Fig. 15 a part of an electric motor with a stator and an impedance element mounted on it; Fig. 16 the body of the stator of the electric motor according to Fig. 2 with a cylindrical lateral surface and an impedance element extending along it; and Fig. 17 the body of the stator of the electric motor according to Fig. 2 with a cylindrical lateral surface and an impedance element running along it.

[0036] Fig. Figure 1 shows an aircraft 2 in the form of an electrically powered airplane with a fuselage 20 and wings 21.

[0037] Aircraft 2 comprises at least one electric drive unit, specifically two electric drive units. Each electric drive unit comprises an electric machine 10, which can be operated as an electric motor, and a propeller 14. The driven propellers 14 generate thrust for aircraft 2. In this case, one electric drive unit is mounted on each of the wings 21 of aircraft 2, although other arrangements are also conceivable. The propellers 14 comprise several propeller blades, in this example three, which are mounted on a hub.

[0038] In alternative configurations, aircraft 2 includes, for example, a fan instead of a propeller and / or one or more electric drive units, each with at least one propeller, fan, or other rotor unit. Furthermore, one or more drive units can, of course, be positioned and mounted at a location other than a wing, for example, on the fuselage.

[0039] Furthermore, aircraft 2 includes, for example, a battery system 22 (or alternatively or additionally, another energy source, e.g., a fuel cell, a generator, a photovoltaic system, or the like). The battery system 22 stores electrical energy for operating the electric drive units. The battery system 22 comprises several rechargeable battery cells. The battery system 22 is connected to inverter 110 as described below (see, e.g., [reference]). Fig. 2 and Fig. 3) connected, which convert a DC voltage from the battery system 22 into an AC voltage. For efficient transmission of the electrical power, further elements can be arranged between the battery system 22 and the inverter 110. The AC voltage is used to supply the electric machine 10 of the respective electric drive unit in order to set the respective propeller 14 into rotation and thus propel the aircraft 2. The aircraft 2 can also include a turbogenerator 24, e.g., instead of or in addition to the battery system 22.

[0040] Aircraft 2 is depicted here as a fixed-wing aircraft. In an alternative configuration, the aircraft is designed as a VTOL aircraft. In this case, the electric drive units are, for example, at least partially vertically oriented or movable into a vertical position. Furthermore, more than two electric drive units can be provided, e.g., four or eight.

[0041] Fig. Figure 2 shows a simplified representation of the electric machine 10 of one of the electric propulsion units of aircraft 2.

[0042] The electric machine 10 is shown here as an example of a permanent magnet synchronous machine. Fig. 2 it is evident that the electric machine 10 is designed as an internal rotor, although of course a design as an external rotor or disc rotor is also possible.

[0043] The electric machine 10 comprises a stator 100 and a rotatable rotor 101. The stator 100 has an unlabeled opening in which the rotor 101 is rotatably mounted.

[0044] The stator 100 comprises a body 108, here exemplified as a laminated core, to which teeth 102 are attached (here exemplified as integral parts within the respective laminations), which can also be referred to as stator teeth. The teeth 102 are aligned with an air gap L between the body 108 of the stator 100 and the rotor 101. The teeth 102 project radially from the body 108, in this case radially inwards. The body 108 comprises iron, e.g., at least 50% by weight.

[0045] The stator 100 has several winding systems 103A-103D, which can also be referred to as "lanes". The winding systems 103A-103D can be electrically isolated from one another or connected on the power supply side. Each of the winding systems 103A-103D has windings for three electrical phases U, V, W. The individual winding systems 103A-103D are shown here only schematically for the sake of simplicity. Electrical conductors of the winding systems 103A-103D are wound around the teeth 102 of the stator 100 in the form of coils 104.

[0046] Each of the winding systems 103A-103D is designed for multiphase, here three-phase, operation and is connected to the multiphase, here three-phase, alternating voltage with phases U, V, W. In the intended operation of the electrical machine 10, the winding systems 103A-103D (or at least a part of the winding systems 103A-103D) are accordingly supplied with the alternating voltage.

[0047] The rotor 101 is shown here in a simplified example as a salient-pole rotor. The rotor 101 comprises one or more permanent magnets to provide the magnetic flux. In the embodiment shown, the rotor 101 is provided to have a magnetic north pole N and a magnetic south pole S, although this is only an example and for the sake of illustration. Of course, more magnetic poles can also be provided circumferentially, e.g., alternating.

[0048] The rotor 101 is rotatably mounted about an axis of rotation D relative to the stator 100. The three-phase alternating voltage, whose phases U, V, and W are shown here as examples with a phase shift of 120° each, generates a rotating magnetic field in each winding system 103A-103D during normal operation. This rotating magnetic field interacts with the permanent magnet field provided by the rotor 101, thus causing the rotor 101 to rotate relative to the stator 100 during motor operation. The electric machine 10 is intended to serve as the drive motor for the propeller 14. It can also be provided that the electric machine 10 can be operated in intermittently or continuously as a generator to feed energy back into the system or to permanently act as a power source itself.

[0049] In Fig. Figure 2 schematically shows the sections of the winding systems 103A-103D, which are assigned to the respective phases U, V, W.

[0050] The electric drive unit comprises power electronics, in this case in the form of a power supply 11, for each of the winding systems 103A-103D. Each of the winding systems 103A-103D of the electric machine 10 is connected to one of the three-phase power supplies 11. The respective power supply 11 provides the alternating current with the three phases U, V, W for the corresponding winding system 103A-103D. The power supplies 11 obtain the electrical energy required for intended operation from an energy source electrically connected to the power supplies 11, in this example in the form of the battery system 22.

[0051] The individual power supplies 11 are independent of each other. If one of the winding systems 103A-103D or one of the power supplies 11 fails, the other power supplies 11 and winding systems 103A-103D can continue to operate. The propeller 14 can be driven independently of each of the individual winding systems 103A-103D (via the separate lanes).

[0052] The power supplies 11 are identical in construction, although different configurations are also conceivable. Exactly four power supplies 11 and winding systems 103A-103D are provided here, but alternatively, for example, exactly two, exactly three, or even more than four power supplies 11 and winding systems 103A-103D could be provided, or alternatively, only exactly one power supply 11 and exactly one winding system 103A-103D.

[0053] During operation, the electric machine 10 is supplied with e.g. 100 kW up to 10 MW.

[0054] Fig. Figure 3 shows one of the power supplies 11 in a simplified representation. The power supply 11 comprises an inverter 110 and a control unit 111. The control unit 111 can also be referred to as a "lane controller".

[0055] The inverter 110 is connected to a DC voltage source 16. The DC voltage U DC This is provided here by the battery system 22 or alternatively by another energy source of the aircraft 2. In the exemplary arrangement shown with three half-bridges, each of the three phases U, V, W of the electric machine 10 is connected via a branch and a switching element S1-S6 to each of the two potentials of the DC voltage U. DCconnectable. For example, if the upper switching element S1 of phase U is closed and the lower switching element S4 is open, then the positive potential of the DC voltage U is applied to phase U. DC On, with the switch in the reversed position, the negative value is displayed. The two switching elements S1-S6 of a phase U, V, W form an example of a half-bridge circuit here. At a common star point 106 (see Fig. 4) The three phases U, V, W are electrically connected to each other.

[0056] The switching elements S1-S6 are, for example, semiconductor components such as transistors, thyristors or the like.

[0057] If, for each phase U, V, W, one of the two switching elements S1-S6 is closed and the other is opened, six possible switching states result, which are referred to as the fundamental voltage space vector in the stator-fixed coordinate system. In two further switching states, either all upper or all lower switching elements S1-S6 are closed, and the others are open. These states can also be referred to as zero-voltage vector states. In these two cases, the three phases U, V, W are short-circuited.

[0058] The control unit 111 controls the inverter 110. The control unit 111 controls the switching states of the switching elements S1-S6. Here, the control unit 111 provides pulse width modulation (PWM) signals to the inverter 110 as an example. The switching elements S1-S6 are then opened or closed according to the PWM signals. This allows voltage vectors with any desired angle to be set in the stator-fixed coordinate system. Furthermore, the amplitude of a voltage vector can be set in this way. The inductance of the windings provides appropriate filtering, so that a corresponding alternating current is established for each of the phases U, V, W, which is, for example, sinusoidal.

[0059] The electric machine 10 thus comprises the stator 100 with one or more, here four electrically separated winding systems 103A-103D and the rotor 101, which can be set into rotation relative to the stator 100 by energizing the winding systems 103A-103D, wherein the inverters 110 of the power supplies 11 are each electrically connected to one of the winding systems 103A-103D.

[0060] The stator 100 comprises the four (alternatively e.g. one, two or three) electrically separated winding systems 103A-103D and accordingly the four power supplies 11 (alternatively e.g. one, two or three).

[0061] In Fig. Figure 3 further illustrates that the electric machine 10 comprises electrical connection points 105A, 105B, 105C. These electrical connection points 105A, 105B, 105C are, for example, terminals. In this case, the electric machine 10 (e.g., for each of the winding systems 103A-103D) comprises three electrical connection points 105A, 105B, 105C, one for each of the three phases U, V, W. Furthermore, the power supply 11 comprises several, here three, terminals 112A, 112B, 112C. The terminals 112A-112C of the power supply 11 are electrically connected to the connection points 105A-105C of the electric machine 10 in order to supply the electric machine 10 with current (with currents Iu, Iv, Iw).

[0062] Supply lines, such as electrical cables or the like, in the electrical connections between connection points 105A-105C of the electric machine 10 and terminals 112A-112C of the power supply 11 exhibit an (electrical) impedance. This is generally lower than the (electrical) impedance of the electric machine 10, which can be high due to the large inductance of the winding systems. As a result, a voltage wave experiences a step in impedance. When transmitting an alternating voltage in the form of waves, especially with steep voltage edges, particularly rectangular pulses, reflections of voltage waves can occur if the impedance changes along the line. The impedance can therefore also be referred to as characteristic impedance or wave resistance.

[0063] The amplitude ratio between the reflected and incident waves is given as the reflection coefficient gamma. This reflection coefficient is calculated as the ratio of the reflected voltage Ur to the incident voltage Ui: Gamma=Ur / Ui.

[0064] The reflection coefficient gamma can be expressed more broadly as: Gamma=(Z2−Z1) / (Z2+Z1), where Z1 represents the impedance before the impedance step and Z2 represents the impedance after the impedance step.

[0065] The reflection coefficient gamma can take a value between -1 and 1, where a value of -1 indicates total internal reflection at the short-circuited end of a conductor, a value of 0 indicates no reflection, and a value of 1 indicates total internal reflection at the open end of a conductor. The negative sign indicates phase inversion, meaning that the incident and reflected waves can cancel each other out. A reflection coefficient close to 1, however, leads to essentially double the maximum voltage, at least for a short period. In multiphase machines, such maxima can also overlap and further increase the resulting voltage. Such stresses can lead to rapid aging of the insulation of the affected conductors and thus to a shortened service life of the electrical machine.

[0066] The aforementioned electrical connections between connection points 105A-105C of the electric machine 10 and terminals 112A-112C of the power supply 11 are shown in the Fig. 2 and Fig. 3 simplified representations and are subsequently discussed with reference to Fig. 4 will be explained in more detail.

[0067] Fig. Figure 4 shows a system 1 of the aircraft 2. The system 1 comprises the electric machine 10 of one of the electric propulsion units, for example the electric machine 10 according to Fig. 2. As already explained, the electric machine 10 has the stator 100 and the rotor 101, which is rotatable relative to it. Furthermore, the electric machine 10 has the electrical connection points 105A-105C, wherein the coils 104 of the electric machine 10 are electrically connected to the connection points 105A-105C. The coils 104 of the electric machine 10 are in Fig. 4 illustrated by corresponding symbols. The coils 104 are attached to the body 108 of the stator 100, in this example wound around the teeth 102 of the body 108. The body 108 guides the magnetic field lines of the coils 104. The body 108 serves as a yoke.

[0068] The electric machine 10 has a sub-circuit 107A, 107B, 107C for each of the three phases U, V, W. Each of the sub-circuits 107A-107C comprises several coils 104. The sub-circuits 107A-107C each comprise coils 104 connected in series and / or parallel. In the example shown, each of the sub-circuits 107A-107C comprises coils 104 connected in series and coils 104 connected in parallel. This is shown only as an example. Fig. 4 provided that each of the sub-circuits 107A-107C comprises two branches connected in parallel to each other, each with several, namely three, coils 104 connected in series, whereby other numbers are also possible.

[0069] Sub-circuits 107A-107C are each connected at one end to one of the connection points 105A-105C. Sub-circuits 107A-107C are each connected at their other end to a star point 106. At star point 106, the three sub-circuits 107A-107C are electrically connected to each other.

[0070] Each of the sub-circuits 107A-107C has an impedance Z2. The impedances Z2 of the sub-circuits 107A-107C are identical. The impedances Z2 of the sub-circuits 107A-107C represent the respective characteristic impedance of the corresponding sub-circuit 107A-107C from the respective connection point 105A-105C to the star point 106.

[0071] Furthermore, system 1 includes at least one power supply 11, here by way of example the power supply 11 according to Fig. 3.

[0072] System 1 further comprises electrical supply lines 12A-12C and at least one impedance element 13, here several impedance elements 13, in this case three.

[0073] The electrical supply lines 12A-12C each have an impedance Z0 (and, in particular, the same impedance between them). The impedance Z0 of each supply line 12A-12C is lower than the impedance Z2 of the corresponding sub-circuit 107A-107C.

[0074] Each of the connection points 105A-105C of the electric machine 10 is connected via one of the impedance elements 13 to one of the supply lines 12A-12C, via which the corresponding impedance element 13 is connected to a corresponding terminal 112A-112C of the power supply 11. The respective impedance element 13 thus establishes an electrical connection between the corresponding connection point 105A-105C (and the corresponding coil(s) 104) of the electric machine 10 and the corresponding terminal 112A-112C of the power supply 11. The respective electrical supply line 12A-12C establishes an electrical connection between the corresponding impedance element 13 and the corresponding terminal 112A-112C of the power supply 11.Furthermore, for each phase U, V, W, a connecting line 15A, 15B, 15C is illustrated, which establishes an electrical connection between the corresponding impedance element 13 and the corresponding connection point 105A-105C of the electric machine 10, provided that the respective impedance element 13 is not directly connected to the respective connection point 105A-105C. Thus, for each phase U, V, W, the corresponding supply line 12A-12C and the corresponding impedance element 13 (and, if applicable, the corresponding connecting line 15A-15C) (in this order) are connected in series between the respective terminal 112A-112C and the respective connection point 105A-105C.

[0075] Consequently, at least one of the coils 104 (via the connection points 105A-105C of the electrical machine 10) is connected to one of the supply lines 12A-12C via a corresponding impedance element 13. In the present example, this applies to each of the coils 104.

[0076] The connection points 105A-105C of the electrical machine 10 are reference points on or in the electrical machine 10. In one embodiment, the connection points 105A-105C of the electrical machine 10 can be terminals, e.g., terminals, e.g., screw terminals, or solder joints, and / or a section of an electrical conductor to which the first coil 104 of the corresponding sub-circuit 107A-107C (directly) adjoins.

[0077] As already mentioned, the connecting lines 15A-15C can also be omitted, e.g. the impedance elements 13 are then connected directly to the respective connection points 105A-105C of the electric machine 10 (especially without any distance to them) or form these connection points 105A-105C.

[0078] The impedance elements 13 are designed to each have an impedance Z1 (in particular, the same impedance among themselves) which is greater than the impedance Z0 of the respective supply line 12A-12C. In this way, the impedance step, which would conventionally only occur in the sub-circuit of the machine, can take place wholly or partially beforehand in the impedance element. This also reduces the effects of reflections at the designated impedance element on the sub-circuit before they reach it.

[0079] Reflections can also occur between the impedance element and the sub-circuit. Table 1 below shows the percentage ratio Z1 / Z2 in the top row, i.e., what percentage Z1 represents of Z2. The corresponding reflection coefficient Gamma is given in the bottom row. Table 1 5% 11% 18% 25% 33% 43% 54% 66% 82% 100% 122% 150% 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0 -0,1 -0,2

[0080] Even a small value of the impedance Z1 of the respective impedance element 13 can reduce reflections. To achieve an effective reduction of reflections, the impedance Z1 of the respective impedance element 13 can be chosen to be 5% or more of the impedance Z2 of the respective sub-circuit 107A-107C, in particular at least 20% or at least 50%. A value of Z1 that is greater than the value of Z2 is not ideal, but possible and better than complete reflection. For example, a value of Z1 from 0.82 * Z2 to 1.22 * Z2 is possible. Particularly good results are possible with Z1 = Z2 ± 5%. The larger the inductance Z1 of the impedance elements 13, the greater their weight can be. Therefore, in practice, a value for Z1 can be chosen that prevents a portion (e.g., more than half) of the reflections and is not particularly heavy, e.g., 82% or between 82% and 100% of Z2.

[0081] As a result, the impedance step between the respective impedance element 13 and the electrical machine 10 is significantly reduced, which instead results in an impedance step from the respective supply line 12A-12C to the impedance element 13. The impedance elements 13 can be provided with insulation 134 for this purpose, see e.g. Fig. 9. Unlike at the coils 104, this insulation 134 can be reinforced much more easily at the impedance element 13 to such an extent that it withstands even strong reflections for any length of time. The insulation 134 has a greater thickness than the respective insulation I of the coils 104 (see e.g. Fig. 9).

[0082] The individual impedance elements 13 are arranged, for example, at a distance from each other to avoid coupling, or adjacent to each other to cancel out maxima with a phase-shifted control.

[0083] The impedance elements 13 can be identical to each other.

[0084] The 12A supply line is a cable. The 12A supply line has a length. The 15A connecting line, if present, is also a cable and has a length. The length of the 15A connecting line is 1 m or less, e.g., 10 cm or less, or even just 1 cm or less. This further reduces the occurrence of reflections. As mentioned, the 15A connecting line can also be omitted, and the impedance element 13 can be connected directly to the 105A connection point.

[0085] The length of the 12A supply line is greater than the length of the 15A connecting line, if the latter is provided. The length of the 12A supply line can be, for example, more than 1 m, more than 2 m, or more than 5 m. This allows the power supply 11 to be located at a considerable distance from the electrical machine 10. The length of the 15A connecting line, if present, can be measured from the respective impedance element 13 to the first coil 104 of the corresponding sub-circuit 107A-107C.

[0086] The impedance element 13 comprises, for example, a coil, as will be explained in more detail below. The impedance element(s) 13 is / are integrated into the stator 100.

[0087] Fig. Figure 5 shows a system 1 for the aircraft 2, which is set up like system 1 according to Fig. 4, in contrast to this, for example only one coil 104 is provided per sub-circuit 107A, 107B, 107C or alternatively, marked with dashed lines, only one row of (e.g. three) coils 104.

[0088] Furthermore, it is illustrated that the respective connection point 105A-105C is located at the input or beginning of the (first) coil 104 of the respective sub-circuit 107A-107C (e.g., forms the input or beginning of the respective (first) coil 104). The impedance elements 13 are each directly connected to the corresponding connection point 105A-105C. At the connection point 105A-105C, for example, a cable cross-sectional area and / or the thickness of an insulation and / or the properties (e.g., the material) of the insulation change.

[0089] Fig. Figure 6 shows a method for producing a system 1, e.g., system 1 according to Fig. 4 or according to Fig. 5. The procedure comprises the following steps.

[0090] Step S1: Providing an electric machine 10 with a stator 100, a rotor 101 rotatable relative to it, and electrical connection points 105A-105C, wherein coils 104 of the electric machine 10 are electrically connected to the connection points 105A-105C. The coils are mounted on a body 108 of the stator 100.

[0091] Step S2: Determining the impedance Z0 of electrical supply lines 12A-12C, via which each of the connection points 105A-105C (and the coils 104) of the electrical machine 10 is connected to a power supply 11.

[0092] Step S3: Determining the impedance Z2 of each of several sub-circuits 107A-107C of the electric machine 10 that are electrically connected to a star point 106.

[0093] Step S4: Providing one or more impedance elements 13 for one or each of the supply lines 12A-12C, each with an impedance Z1 that is greater than the impedance Z0 of the respective supply line 12A-12C. The impedance elements 13 are provided, for example, with an impedance Z1 that is at least 82% (or 95%) and at most 122% (or 105% or 100%) of the impedance Z2 of the respective sub-circuit 107A-107C, and in particular, is equal to the impedance Z2 of the respective sub-circuit 107A-107C.

[0094] Step S5: Connecting one or each of the connection points 105A-105C and / or the coils 104 of the electric machine 10 via the impedance element 13, or via each of the impedance elements 13, to one of the respective supply lines 12A-12C, via which the respective impedance element 13 is or will be connected to a respective terminal 112A-112C of the power supply 11. The impedance element 13 comprises an electrical conductor which is arranged at least partially along the body 108 of the stator 100.

[0095] The impedances Z0, Z2 can be calculated from the known geometries and materials of the supply lines 12A-12C and the electrical machine 10. Alternatively or additionally, they can also be measured.

[0096] Fig. Figure 7 shows an exemplary setup of a measuring arrangement for measuring the characteristic impedance Z2 of the sub-circuits 107A-107C of the electric machine 10.

[0097] The electric machine 10 is shown only schematically. The sub-circuits 107A-107C are connected to each other at the star point 106 and are also electrically connected to each other at their other ends for measurement purposes. An impedance analyzer 3 is electrically connected to this connection point and also to a ground potential of the electric machine 10, e.g., to its housing or the like. A common-mode signal can be generated in this way.

[0098] The impedance analyzer 3 is used to determine the first resonant frequency f1CM of a standing wave as well as the capacitance cCM (at a frequency in which the phase angle of the impedance is still approximately -90°, e.g. at 10 kHz) of the connected circuit.

[0099] The characteristic impedance Z is Z = Sqrt(I / c), where I is the inductance per unit length and c is the capacitance per unit length.

[0100] The wave propagation speed is v0 = 1 / Sqrt(I * c).

[0101] The first resonant frequency for a standing wave on an electrical line (cable or winding) of length s with a fixed end (i.e. the voltage source is low impedance, therefore a voltage reflection at its end leads to total reflection with phase reversal and thus a resulting voltage at that end equal to zero) is f1CM = v0 / (4*s).

[0102] For the total capacity: cCM = c * s.

[0103] The characteristic impedance is calculated as follows: Z = 1 / (4 * f1CM * cCM). Z1 can then be calculated based on this value for Z2.

[0104] The impedance analyzer 3 can also be used to measure the impedance Z0 in an analogous way.

[0105] As a result of the reduced reflections, the insulation of the electrical machine 10 can be simplified. The impedance elements 13 enable a simplified insulation design.

[0106] Fig. Figure 8 illustrates the body 108 of the stator 100 with an impedance element 13A. The impedance elements 13 of the system 1 described above can be arranged according to the diagram in Fig. The impedance element 13A shown in section 8 is formed.

[0107] Body 108 has a circular cylindrical shape. Body 108 is hollow cylindrical. Body 108 has two opposite end faces 109. The end faces 109 are aligned parallel to each other. The end faces 109 are ring-shaped. A lateral surface M of body 108 extends between the end faces 109.

[0108] The body 108 further comprises the teeth 102. These point concentrically inwards towards the axis of rotation D. The teeth 102 are aligned in the direction of a respective radius of the axis of rotation D. At least one of the coils 104 is wound around each tooth 102, which in Fig. 8 are not shown again. In each receiving area B (here in the form of a groove) between two teeth 102, sections of conductors from at least two coils 104 are arranged.

[0109] The impedance element 13A comprises an electrical conductor 131, which runs at least partially along the body 108 of the stator 100. In this case, the conductor 131 of the impedance element 13A runs around the outside of the body 108 of the stator 100. The conductor 131 of the impedance element 13A runs in a partial turn (see figure). Fig. 10), in one complete turn or in several turns, here ( Fig. 8) in several turns around the lateral surface M of the body 108. In the example shown, the conductor 131 forms a spiral that is concentrically aligned around the axis of rotation D along the axis of rotation D. Here, the conductor 131 extends, for example, from one end face 109 to the other end face 109.

[0110] The conductor 131 is therefore wound around a winding axis A3, which coincides with the axis of rotation D. Furthermore, the coils 104 are each wound around a winding axis A1, which is located centrally within the respective coil 104.

[0111] The winding axes A1 of the coils 104 are, for example, radially, parallel, or tangentially aligned with the axis of rotation D about which the rotor 101 is rotatable relative to the stator 100, and in this example, concentrically with the axis of rotation D. The winding axis A1 of each coil 104 is perpendicular to the axis of rotation D, intersects the axis of rotation D, and extends radially to it. The winding axis A3 of the impedance element 13A is, for example, radially, parallel, or tangentially aligned with the axis of rotation D. Furthermore, the winding axis A3 of the impedance element 13A is oriented differently from the winding axes A1 of the coils 104, namely, in this case, parallel (and, since it is also located at the same position in space, also coaxial) with the axis of rotation D. Each of the winding axes A1 of the coils 104 is perpendicular to the winding axis A3 of the impedance element 13A, as shown in Fig. Figure 8 illustrates one of the winding axes A1. The winding axis of the impedance element, for example, coincides with the rotation axis D. It should be noted that the coils 104 can also be oriented at an angle in space, for example, if the teeth are not perpendicular but are at a (slight) preferred angle on the body.

[0112] Fig. Figure 8 further shows that the supply line 12A is connected to the conductor 131 of the impedance element 13A at a terminal 133 (which is shown here by way of example on the body 108). Furthermore, the conductor 131 is connected at one end 132 (the end furthest from the terminal 133) to (at least) one of the coils 104 (directly), e.g., via a soldered joint, a terminal, or the like. The conductor 131 of the impedance element 13A differs from the conductor of the coil 104 connected to it, in this case by a greater thickness of the insulation around the conductor 131, by a different cross-sectional shape, and by a (larger) cross-sectional area of ​​the conductor 131.

[0113] Due to the design of the impedance element 13A shown, the body 108 serves as the iron core for the conductor 131, thus eliminating the need for an additional iron core. As a result, the impedance element 13A adds only a small amount of weight. However, by protecting the coils 104, weight can be saved elsewhere. Furthermore, the power supply can be arranged more flexibly.

[0114] In accordance with the order Fig. 8. The capacitance can be easily adjusted by changing the distance between the conductor 131 and the iron body 108. The impedance L = N 2 The reluctance (R) can be adjusted via the number of turns, N. A small reluctance can be achieved through the large spanned area. The helical arrangement shown is merely an example. A purely axial or circumferential configuration is also possible.

[0115] The Fig. 9 and Fig. Figure 10 illustrates another possible embodiment of an impedance element 13B for the electric machine 10. The electric machine 10 can include the impedance element 13B instead of, or in addition to, the impedance element 13A. For example, the electric machine 10 includes one impedance element 13B for each phase U, V, W according to Figure 10. Fig. 9 and Fig. 10.

[0116] Fig. Figure 9 shows a section of a cross-section oriented perpendicular to the axis of rotation D. The receiving area B between two teeth 102 and the sections of two coils 104 partially running within it are visible. The conductors of the coils 104 each have insulation I. This insulation is thinner than the insulation 134 of the conductor 131 of the impedance element 13B. Alternatively, the insulation can be provided to have a thickness of at least 50%, at least 100%, or more than 100% of the insulation I.

[0117] The conductor 131 of the impedance element 13B runs section by section (or alternatively, completely) between the two coils 104. In this case, the conductor 131 of the impedance element 13B is U-shaped. The conductor 131 runs along the outside of the lateral surface M of the body 108 (parallel to the axis of rotation D) from one end face 109 to the other. The conductor 131 is then bent inwards and runs in the receiving area B, which can also be called a groove, between the two teeth 102 back to one end face 109. The section of the conductor 131 in the receiving area B is located at its radially outer end. In this case, the conductor 131 (with its insulation) rests against an inner surface of the body 108. This is where the two coils 104 are furthest apart, thus providing the most space. For example, conductor 131 is (at least there) arranged in a cooling channel for a cooling fluid.Furthermore, the body 108 is enclosed at its outer surface M by a housing, through which the body 108 is cooled. The radially outer end of the receiving area B therefore allows for particularly good cooling of the conductor 131.

[0118] The conductor 131 of the impedance element 13B thus runs (at least sectionally) along the body 108 of the stator 100, namely (at least) in two parallel sections, one of which in the present example is located on an inside and one on an outside of the body 108.

[0119] The conductor 131 is wound around a central winding axis A2, which is oriented tangentially to the axis of rotation D. The winding axis A2 of the impedance element 13B is oriented perpendicular to (and spaced apart from) the axis of rotation D and perpendicular to the radius located on the axis of rotation D and passing through the impedance element 13B. The winding axis A2 of the impedance element 13B lies tangentially to an imaginary circle around the axis of rotation D.

[0120] The impedance element 13B can be arranged at exactly one recording area B or, for example, at every recording area according to Fig. 9 (through corresponding sections of conductor 131), on which the corresponding sub-circuit 107A-107C has a coil 104. The impedance element 13B runs partly through the slots of the electrical machine 10, as in e.g. the Fig. 9 and Fig. 10 shown.

[0121] Fig. Figure 11 shows (unrolled from the circular shape for illustrative purposes only) the sub-circuits 107A-107C with the letters a, b, and c of the coils 104 wound around the teeth. For example, the respective impedance element 13B runs in the slots with two coil sides of the same phase (aa, bb, cc). Here, the respective impedance element 13B can serve to increase the torque. However, it is also possible to arrange impedance elements in the other slots (e.g., ab, bc, etc.).

[0122] The Fig. 12 and Fig. Figure 13 illustrates another possible embodiment of an impedance element 13C for the electric machine 10. The electric machine 10 can include the impedance element 13C instead of, or in addition to, the impedance element 13A and / or the impedance element 13B. For example, the electric machine 10 includes one impedance element 13C for each phase U, V, W according to Fig. 12 and Fig. 13.

[0123] Fig. Figure 12 again shows a section of a cross-section oriented perpendicular to the axis of rotation D. This illustrates that the impedance element 13C (this also applies to the impedance element 13B) can comprise (at least) a complete winding instead of an open, U-shaped winding. According to Fig. 12 and Fig. The conductor 131 runs along the outer surface M of the body 108 (parallel to the axis of rotation D) from one end face 109 to the other. The conductor 131 is then bent inwards and runs back to one end face 109 between the two teeth 102 in the receiving area B. The conductor 131 is then bent outwards again and runs (parallel to the first section) to the other end face 109. Optionally, the impedance element 13C has one or more further windings thereafter. The impedance element 13C forms a coil 130.

[0124] Furthermore, in the Fig. 12 and Fig. Figure 13 illustrates that the section(s) of the conductor 131 running along the outer surface M are held to the body 108 by a positive-locking section F. The positive-locking section F covers the section(s) of the conductor 131 running along the outer surface M. The positive-locking section F can comprise or consist of iron. Here, the positive-locking section F extends, by way of example, from one end face 109 to the other. This allows the magnetic field of the impedance element 13C to be strengthened. Furthermore, the impedance element 13C can be securely held to the body 108.

[0125] The Fig. 14 and Fig. Figure 15 illustrates another possible configuration of an impedance element 13D for an electric machine for aircraft 2. For example, the electric machine comprises an impedance element 13D for each phase U, V, W according to Fig. 14 and Fig. 15.

[0126] The electric machine according to Fig. 14 and Fig. Figure 15 illustrates the shape of a disc rotor. The electric machine is, for example, an axial flux machine. However, the electric machine can also be designed as a radial flux machine, with a double rotor, where one part is arranged radially inside the stator and one part radially outside the stator. The section would then also be as shown in Fig. 14 shown, only the axis of rotation would not be vertically aligned next to it but horizontally aligned below it.

[0127] The rotor 101 comprises two sub-rotors T1 and T2 on either side of the coils 104 of the stator 100. One part of the coils 104 faces one sub-rotor T1, and another part faces the other sub-rotor T2. The conductor 131 of the impedance element 13D runs sectionally between two of the coils 104 facing one sub-rotor T1 (in Fig. 14 above) and sectionally between two of the coils 104 facing the other partial rotor T2 (in Fig. 14 below). The conductor can describe a winding open at one end (cf. Fig. 14) or several windings (see Fig. 15) The ends of the winding can be arranged on the same side of the body or on opposite sides (see Fig. 15).

[0128] In the design of the Fig. 9 to 15 the impedance element 13B-13D is arranged such that an electric current flowing through the impedance element 13B-13D generates a magnetic field which sets the rotor 101 into rotation relative to the stator 100.

[0129] The impedance elements 13B-13D can each have a single turn or multiple turns in a single receiving area B. Furthermore, the impedance element 13B-13D can be arranged in several (e.g., all) receiving areas B, each with a single turn or multiple turns.

[0130] Fig. Figure 16 illustrates another possible configuration of an impedance element 13E for the electric machine 10. The electric machine 10 can include the impedance element 13C instead of, or in addition to, one of the other impedance elements 13A-13D. For example, the electric machine 10 includes one impedance element 13E for each phase U, V, W according to Fig. 16.

[0131] Body 108 is constructed as described above with reference to Fig. As already explained in section 8, the conductor 131 of the impedance element 13E is designed to follow the ring shape along each of the two end faces 109, thus completing a circuit. The supply line 12A is electrically connected to conductor 131 at terminal 133. From there, conductor 131 runs once around the ring shape of one end face 109. It is also possible for conductor 131 to complete multiple circuits, i.e., to have several windings on one end face 109. In this case, conductor 131 continues across the outer surface M to the other end face 109. There, conductor 131 continues once around the ring shape of the other end face 109, completing a circuit. It would also be possible for conductor 131 to be connected directly to sub-circuit 107A immediately after completing its circuit along one end face (with or without the circuit across the outer surface M). Furthermore, it may be provided that the conductor 131 (e.g.(also) on the other end face 109 several times, thus having several windings on the other end face 109. After the winding(s) on the other end face 109, the conductor 131 is connected to the corresponding sub-circuit 107A via a further connection 133.

[0132] Fig. Figure 17 illustrates another possible embodiment of an impedance element 13F for the electric machine 10, similar to Fig. 16, wherein according to Fig. 17 The conductor 131 of the impedance element 13F runs (several times) in a semicircle. Specifically, the conductor 131 runs from the first of the two end faces 109 (from the terminal 133) to the second of the two end faces 109, describes a semicircle there, and then runs back to the first of the end faces 109. There, the conductor 131 describes another semicircle and runs back to the second end face 109, describes another semicircle there, runs back to the first end face 109, and describes yet another (fourth) semicircle there.

[0133] Then conductor 131 is connected to the first coil(s) 104 of sub-circuit 107A. It is also possible that fewer (e.g., 2) or more (e.g., 8) semicircles are described.

[0134] When the body 108 is pressed into an outer casing, the arrangement according to Fig. 16 or according to Fig.17 the arrangement of the conductor 131. The conductor runs in a depression on the outer surface M.

[0135] A spiral arrangement of conductor 131 is also possible.

[0136] It should be noted that System 1 can be used in a (e.g., purely) electrically powered aircraft, or alternatively in a hybrid-electrically powered aircraft. Furthermore, the electric machine 10 of System 1 can be an electric motor (i.e., operable as such) and / or a generator (i.e., operable as such).

[0137] It is understood that the invention is not limited to the embodiments described above and that various modifications and improvements can be made without deviating from the concepts described herein. Any of the features can be used separately or in combination with any other features, provided they are not mutually exclusive, and the disclosure extends to and includes all combinations and subcombinations of one or more features described herein. Reference symbol list 1 system 10 electric machine 100 Stator 101 Rotor 102 teeth 103A-103D winding system 104 coil 105A-105C connection point 106 Star Point 107A-107C Sub-circuit 108 bodies 109 Front 11 Power electronics (power supply) 110 inverters 111 Control unit 112A-112C connector 12A-12C supply line 13, 13A-13F Impedance element 130 coil 131 leaders 132 End 133 connection 134 Insulation 14 propellers 15A-15C connecting cable 16 DC voltage source 2 aircraft 20 hull 21 wings 22 Battery system 24 Turbogenerator 3 Impedance analyzer A1, A2, A3 winding axis B Recording area D axis of rotation F Form-fit section I Isolation lu, Iv, Iw current intensity L air gap M surface area North Pole South Pole S1-S6 switching element T1, T2 partial rotor U DC DC voltage U, V, W phase Z0, Z1, Z2 Impedance

Claims

[1] System (1), in particular for an aircraft (2), comprising: - an electric machine (10) with a stator (100) and a rotor (101) rotatable relative to it, wherein coils (104) are fixed to a body (108) of the stator (100), - a power electronics (11) with switching elements (S1-S6) and - electrical supply lines (12A-12C), each having an impedance (Z0), wherein at least one of the coils (104) is connected via an impedance element (13, 13A-13F) to one of the supply lines (12A-12C), via which the impedance element (13, 13A-13F) is connected to a terminal (112A-112C) of the power electronics (11), wherein the impedance element (13, 13A-13F) has an impedance (Z1) which is greater than the impedance (Z0) of the supply line (12A-12C) and wherein the impedance element (13, 13A-13F) comprises an electrical conductor (131) which runs at least section by section along the body (108) of the stator (100). [2] System (1) according to claim 1, wherein the conductor (131) of the impedance element (13, 13A, 13E, 13F) runs at least sectionally around the body (108) of the stator (100). [3] System (1) according to claim 1 or 2, wherein the conductor (131) of the impedance element (13B-13D) runs at least sectionally between at least two of the coils (104). [4] System (1) according to one of the preceding claims, wherein the coils (104) are wound around a respective winding axis (A1) and the conductor (131) of the impedance element (13A-13F) is wound around a winding axis (A2, A3). [5] System (1) according to claim 4, wherein the winding axes (A1) of the coils (104) are aligned radially, parallel or tangentially to an axis of rotation (D) about which the rotor (101) is rotatable relative to the stator (100), and wherein the winding axis (A2, A3) of the impedance element (13A-13F) is aligned radially, parallel or tangentially to the axis of rotation (D) and is aligned differently from the winding axes (A1) of the coils (104). [6] System (1) according to claim 4 or 5, wherein the winding axes (A1) of the coils (104) are aligned concentrically to the axis of rotation (D) and the winding axis (A2, A3) of the impedance element (13A-13F) is aligned parallel, in particular coaxially, or tangentially to the axis of rotation (D). [7] System (1) according to one of the preceding claims, wherein the body (108) is cylindrical and has two annular end faces (109) parallel to each other, wherein the conductor (131) of the impedance element (13E, 13F) runs along one or both of the end faces (109) following the annular shape. [8] System (1) according to claim 7, wherein the conductor (131) of the impedance element (13F) extends from one of the first of the two end faces (109) to the second of the two end faces (109), describes a semicircle there and then extends back to the first of the end faces (109). [9] System (1) according to one of the preceding claims, wherein the rotor (101) has two partial rotors (T1, T2) on either side of the coils (104) of the stator (100), wherein a part of the coils (104) faces one partial rotor (T1) and another part of the coils (104) faces the other partial rotor (T2), wherein the conductor (131) of the impedance element (13D) runs at least sectionally between at least two of the coils (104) facing one partial rotor (T1) and at least sectionally between at least two of the coils (104) facing the other partial rotor (T2). [10] System (1) according to one of the preceding claims, wherein an insulation of the conductor (108) of the impedance element (13, 13A-13F) has a greater thickness than an insulation of a respective conductor of the coils (104). [11] System (1) according to one of the preceding claims, wherein the impedance element (13B-13D) is arranged such that an electric current flowing through the impedance element (13B-13D) generates a magnetic field which causes the rotor (101) to rotate relative to the stator (100). [12] System (1) according to one of the preceding claims, wherein the coils (104) are electrically connected to connection points (105A-105C), each of the connection points (105A-105C) of the electrical machine (10) being connected via an impedance element (13, 13A-13F) to one of the supply lines (12A-12C), via which the corresponding impedance element (13, 13A-13F) is connected to a respective terminal (112A-112C) of the power electronics (11), and wherein the impedance elements (13, 13A-13F) each have an impedance (Z1) which is greater than the impedance (Z0) of the respective supply line (12A-12C). [13] System (1) according to claim 12, wherein the electric machine (10) has multiphase windings with star points, in particular three sub-circuits (107A-107C) which each comprise at least one of the coils (104) and extend from one of the connection points (105A-105C) of the electric machine (10) to a star point (106) at which the three sub-circuits (107A-107C) are electrically connected to each other. [14] System (1) according to claim 13, wherein each of the sub-circuits (107A-107C) has an impedance (Z2) and the impedance (Z1) of the respective impedance element (13, 13A-13F) is at least 5% of the impedance (Z2) of the respective sub-circuit (107A-107C), in particular at least 20%, wherein the impedance (Z1) of the respective impedance element (13, 13A-13F) is in particular at least 82% and at most 122% of the impedance (Z2) of the respective sub-circuit (107A-107C), in particular equal to the impedance (Z2) of the respective sub-circuit (107A-107C). [15] System (1) according to one of claims 13 or 14, wherein each of the sub-circuits (107A-107C) comprises several coils (104) connected in series and several coils (104) connected in parallel to each other. [16] System (1) according to any one of claims 12 to 15, wherein the impedance elements (13, 13A-13F) have the same impedance (Z1) among themselves. [17] System (1) according to one of the preceding claims, wherein the impedance elements (13, 13A-13F) each comprise a coil (130). [18] System (1) according to one of the preceding claims, wherein the power electronics (11) is arranged spaced apart from the electrical machine (10). [19] System (1) according to one of the preceding claims, further comprising a propeller (14), wherein the rotor (101) of the electric machine (10) is coupled to the propeller (14) for driving the propeller (14). [20] Method for producing a system (1), in particular according to any one of claims 1 to 19, the method comprising: - Providing (S1) an electrical machine (10) with a stator (100) and a rotor (101) rotatable relative to it, wherein coils (104) are fixed to a body (108) of the stator (100), - Determining (S2) the impedance (Z0) of electrical supply lines (12A-12C) via which the coils (104) are connected to a power electronics unit (11), - Providing (S4) one or more impedance elements (13, 13A-13F) for one or each of the supply lines (12A-12C), each with an impedance (Z1) which is greater than the impedance (Z0) of the respective supply line (12A-12C), and - Connecting (S5) the coils (104) via the impedance element (13, 13A-13F) or via each of the impedance elements (13, 13A-13F) to one of the respective supply lines (12A-12C), via which the respective impedance element (13, 13A-13F) is connected to a respective terminal (112A-112C) of the power electronics (11), wherein the impedance element (13, 13A-13F) comprises an electrical conductor (131) which is arranged running at least section by section along the body (108) of the stator (100).

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