Electric motor for an aircraft, and aircraft

Abstract

The invention relates to an electric motor for an aircraft, the electric motor comprising a stator for generating variable magnetic fields, and a rotor that is rotatable with respect to the stator and designed to carry out a rotational movement when the magnetic fields generated by the stator change, wherein the stator has a plurality of, preferably at least three, electrical coils which are each designed to generate a variable magnetic field independently of one another, wherein each of the coils is connected in series between two electrical half-bridges independently of the other coils and can be connected to a current source via the two electrical half-bridges.

Description

[0001] Electric motor for an aircraft and aircraft

[0002] Technical field

[0003] The present invention relates to an electric motor designed for use in an aircraft. The electric motor comprises a stator and a rotor. The stator has several coils that can be connected separately and independently to an electrical power source.

[0004] The invention also relates to an aircraft with such an electric motor.

[0005] State of the art

[0006] Unmanned and manned electrically powered aircraft are known from the prior art. These aircraft can be designed, for example, for vertical takeoff and landing (eVTOL). Such aircraft typically have an electric motor with a rotatable rotor and a stator. The stator comprises several coils that can generate variable magnetic fields. The rotor, which is usually mechanically connected to a propeller of the aircraft, is designed to perform a rotational movement when the magnetic fields of the coils change accordingly.

[0007] It is known to use one or more three-phase electric motors in electric aircraft. A three-phase electric motor has three—or a plurality of three—coils, with each coil connected in parallel to form an electrical half-bridge and a current source. This means that the coils are each connected to a half-bridge and a common electrical ground (star point). This allows the coils to be energized or both electrical connections to be grounded. This results in the generation or non-generation of a magnetic field. The half-bridges are typically grouped within a three-phase inverter. Structurally, the coils are arranged circumferentially around the rotor at 120° intervals.

[0008] Conventional three-phase electric motors have the disadvantage that all coils must be operated via a common three-phase inverter and a single power supply. However, in electric aircraft applications, electrically isolated and redundant controllers are required. Multiple power sources are also mandatory for regulatory reasons. While this problem can be mitigated by using multiple three-phase stators (multi-phase motor), for example, a dual three-phase system (six-phase motor), such solutions are significantly heavier, resulting in increased weight. Increased motor weight reduces the aircraft's payload and is therefore undesirable. Furthermore, the control software for multi-phase motors is considerably more complex, which consequently increases development costs and is also undesirable.

[0009] Description of the invention

[0010] It is therefore an object of the present invention to satisfy the aforementioned needs and / or to eliminate the disadvantages associated with the prior art. In particular, it is an object of the present invention to provide an electric motor and / or an aircraft with an electric motor that is easier to control, has a higher fault tolerance, is lighter, and can be supplied with electrical current from several independent power sources.

[0011] This problem is solved with an electric motor according to claim 1. Advantageous embodiments of the electric motor according to the invention are the subject of the dependent claims and / or are explained in the following description.

[0012] According to the invention, an electric motor is proposed that is suitable for use in and / or on an aircraft, in particular an eVTOL aircraft. The electric motor comprises a rotor and a stator. The rotor is preferably rotatably mounted in and / or on the electric motor. According to the invention, the rotor is configured to perform a rotational movement when the magnetic field around the rotor changes, in particular when several magnetic fields around the rotor change. For this purpose, the rotor can have several permanent magnets, which are preferably arranged circumferentially distributed in and / or on the rotor.

[0013] To generate the variable magnetic fields, the stator comprises several coils. These coils are preferably arranged circumferentially around the rotor's axis of rotation. For example, the electric motor can have three coils arranged circumferentially around the rotor's axis of rotation, each offset by 120°. Particularly preferably, the electric motor comprises a plurality of three coils, for example, six or nine coils.

[0014] Each coil is designed to generate a magnetic field independently of the other coil(s). The magnetic field of each coil can be changed, for example, by switching the power supply to the respective coil on and off, or by supplying the coil with alternating current.

[0015] According to the invention, each individual coil is connected in series with two electrical half-bridges, so that the corresponding coil can be connected to a power source via the half-bridges. Each coil is part of a separate series circuit that is functionally independent of the other coils or the other series circuits.

[0016] The electric motor according to the invention has the advantage that each of the motor's coils can be connected to a power source that differs from the power sources of the other coils. Simultaneously, the control of the coils can be decentralized. This means that each individual coil can be controlled separately and independently of the other coils. As a result, the electric motor according to the invention, compared to known three-phase electric motors of nearly the same weight, has a higher fault tolerance and can be supplied with electrical current from several independent power sources.

[0017] In an exemplary embodiment of the electric motor, the electric motor includes control electronics. Preferably, the control electronics are configured to control the half-bridges such that each coil generates a variable magnetic field such that the combined magnetic fields cause the rotor to rotate. For example, the control electronics can control the half-bridges so that an alternating magnetic field is generated at each coil, which is phase-shifted with respect to the alternating magnetic fields of the other coils.

[0018] In an advantageous further development of the aforementioned embodiments of the electric motor, the control electronics comprise several current measuring elements. Preferably, one of the current measuring elements is provided within a corresponding series circuit. For example, a first current measuring element can be arranged between a first coil and a half-bridge of the corresponding first series circuit. A second current measuring element can be arranged between a second coil and a half-bridge of the corresponding second series circuit. The current measuring elements can be part and / or an integral component of the respective half-bridge and / or coil. For example, a current measuring element can be integrated into a half-bridge of a series circuit.Preferably, the current measuring elements are each designed to generate a current signal that corresponds to a current applied to the corresponding coil.

[0019] Alternatively or in addition to the current measuring elements, the control electronics can include one or more controllers. Preferably, the number of controllers corresponds to the number of coils in the electric motor. This allows each coil or series circuit to be assigned a controller. With a plurality of controllers, each of the multiple controllers can be functionally independent of the others. For example, the controllers can be electrically isolated from each other.

[0020] For the sake of clarity, only the features of a single controller are described below. However, each of the following features can also apply to all or only some of the multiple controllers. Preferably, the controller is connected to the two half-bridges of a series circuit via voltage supply and / or signal communication. This allows the controller to control or regulate the corresponding half-bridges. The controller can, for example, be a pulse-width modulation (PWM) controller and / or be designed as a PWM controller. If the control electronics include a current sensor and a controller, the current sensor and the controller can be connected via signal communication. Preferably, the current signal from the current sensor forms an input signal for the controller. A control electronics system with one controller and one current sensor per series circuit is described below.The ability to control each coil in series can advantageously allow each coil to be individually and precisely controlled by the corresponding controller based on the current signal. This further increases the precision and error tolerance of the electric motor's control while minimizing its own weight.

[0021] In addition to or as an alternative to the current measuring element, a position sensor can be provided. Preferably, the position sensor is configured to detect the rotational angular position of the rotor, in particular the rotational angular position of the rotor relative to the stator. The position sensor can, for example, output a position signal that corresponds to the rotational angular position of the rotor. The position signal can be provided as an input signal for the control electronics, in particular for the controller(s) of the control electronics. A position sensor can advantageously further increase the precision and error tolerance of the electric motor's control. In advantageous embodiments, the electric motor has several position sensors for redundancy reasons.

[0022] In another exemplary embodiment of the electric motor, the number of turns and / or the wire diameter of the coils differs. This means that the number of turns and / or the wire diameter of at least one coil differs from the number of turns and / or the wire diameter of the other coils. This can advantageously allow the respective coils to be optimized for specific operating points of the electric motor, in particular for specific speeds and / or specific rotor load conditions.

[0023] One or more, preferably all, half-bridges of the electric motor can comprise semiconductor elements containing gallium nitride. Preferably, the semiconductor elements are designed as gallium nitride semiconductor elements. Such an embodiment can have the advantage that switching frequencies of over 100 kHz can be achieved. High switching frequencies can advantageously mean that the DC capacitors need to have a lower capacitance. Alternatively or additionally, high switching frequencies can allow the use of structurally smaller capacitors, e.g., ceramic capacitors instead of electrolytic capacitors, i.e., capacitors with less weight, higher temperature resistance, and a longer lifespan. This enables the integration of the semiconductors into the electric motor. Regardless of the above, the current ripple can be kept low.

[0024] In one exemplary embodiment of the electric motor, the half-bridges can be arranged axially next to the coils on a circular circuit board. This can advantageously result in a particularly compact design of the electric motor, requiring as little installation space as possible in the aircraft. It is also conceivable that the half-bridges are implemented as fully integrated units with an integrated driver, current sensor, level shifter, and / or protection circuit. This could advantageously reduce the number of components, lower costs, and allow for an even more compact design.

[0025] The problem stated at the outset of the invention is also solved with an aircraft according to claim 8. Advantageous further developments of the aircraft according to the invention are the subject of the corresponding dependent claims and / or are explained in the following description.

[0026] According to the invention, an aircraft is proposed which has at least one electric motor according to one of the aforementioned embodiments. The electric motor is configured to drive a lift-generating and / or thrust-generating device of the aircraft.

[0027] For the purposes of this invention, the term "lift-generating and / or thrust-generating device" refers to a device that can be configured to generate a lift force—that is, a vertical thrust force—with which the aircraft can take off vertically, land, and / or hover in the air. Alternatively or additionally, the device can be configured to generate an acceleration force—that is, a horizontal thrust force—by which the aircraft is accelerated in a forward direction. Preferably, the device is configured as an aircraft rotor or propeller. Since the aircraft according to the invention has an electric motor corresponding to the aforementioned embodiments, all of the aforementioned features, combinations of features, and their respective advantages are also transferable to the aircraft according to the invention, or at least transferable by analogy.

[0028] The aircraft can be an electric vertical take-off and landing (eVTOL) aircraft. Regardless of this, the aircraft can have multiple electric motors and / or multiple lift-generating and / or thrust-generating devices.

[0029] In an advantageous further development of the aircraft, the rotor of the electric motor is mechanically connected to the lift-generating and / or thrust-generating device, in particular to the aircraft rotor or propeller. This can advantageously result in a rotary motion of the rotor being transmitted directly or indirectly (for example, via a gearbox) to the aircraft rotor or propeller.

[0030] The aircraft may have a flight control system for controlling the lift-generating and / or thrust-generating device. Preferably, the flight control system is connected via signal communication to the control electronics of the electric motor, in particular to the controllers of the electric motor's control electronics. Additionally, the flight control system may be electrically isolated from the electric motor. For example, the signal-communicating, electrically isolated connection between the flight control system and the electric motor may be implemented via an optocoupler. Functionally, the aircraft's flight control system may be configured to control the controllers.

[0031] In one exemplary further development, the flight control device can have several independent flight control computers. Each of the flight control computers can be connected to each of the electric motor controllers via signal communication and preferably electrical isolation. Such a further development can have the advantage of increasing redundancy and thus fault tolerance within the aircraft.

[0032] The aircraft can have multiple independent power sources.

[0033] For example, the aircraft may have a battery, an external power connection, a fuel cell, and / or a generator. The generator may be driven by an internal combustion engine and / or by a turbomachine, such as a gas turbine and / or a jet engine.

[0034] In one exemplary embodiment of the aircraft, the electric motor can be connected to at least two of the aircraft's independent power sources. For example, a first portion of the electric motor's coils can be connected to a first power source. A second portion of the electric motor's coils can be connected to a second power source, different from the first. This allows the electric motor to operate in hybrid mode. This means that if the electric motor is operating in a range where lower power output is required, particularly when the aircraft is in descent, the electric motor can be powered exclusively by a single power source, such as a fuel cell. In this case, only a portion of the coils would generate a variable magnetic field.In operating conditions requiring high power output, particularly during climb, the electric motor can be supplied with electricity from multiple power sources, such as the fuel cell and the battery. In this case, all coils could generate a variable magnetic field. Additionally or alternatively, the electric motor can be operated with unequal power supplies, specifically varying the load drawn by the motor. For example, the electric motor could draw 6 kW of power from one source and 4 kW from another, resulting in a total motor power of 10 kW.

[0035] This can advantageously ensure that the fuel cell can always operate at its ideal operating point and that power peaks from the electric motor can be absorbed by the battery. This allows the aircraft to be operated particularly efficiently.

[0036] The electric motor can be configured to electrically connect multiple independent power sources. For example, an aircraft battery can be electrically connected to a second power source, particularly a fuel cell, via the electric motor. This has the advantage that the electric motor can be powered not only by two independent power sources, but also, in certain operating conditions, that all coils can be powered by a single power source. This is advantageous, for instance, when the aircraft battery is depleted and power is supplied exclusively by the fuel cell. The benefit of such an embodiment is that the probability of aircraft failure in flight is further increased through redundancy.

[0037] Additionally, the electric motor can also be used as a switch between the power sources. This is particularly advantageous if the aircraft's batteries are to be charged via the second power source during flight. Alternatively, or in addition, the batteries can be charged on the ground via an aircraft charging port and / or the second power source if the electric motor is configured as a switch. The switching function of the electric motor can be designed, for example, so that no electrical connection exists between the battery and the charging port and / or the second power source during flight. On the ground, the electric motor can electrically connect the batteries to the charging port and / or the second power source. In other words, the battery can be charged on the ground both via a charging plug and via the second power source.The latter is advantageous, for example, if no external power supply is available at the aircraft's landing site.

[0038] The invention, as well as advantageous embodiments of the invention, can also be described by the following aspects. The features listed in these aspects can be combined with the aforementioned features as desired, provided this is technically sensible and appropriate.

[0039] Aspect 1: Electric motor for an aircraft, the electric motor encompassing:

[0040] (a) a stator for generating variable magnetic fields, and

[0041] (b) a rotor rotatable with respect to the stator, designed to perform a rotational movement when the magnetic fields generated by the stator change, wherein

[0042] (c) the stator has several, preferably at least three, preferably a plurality of three, electrical coils, each independently configured to generate a variable magnetic field, wherein (d) each of the coils is connected in series between two electrical half-bridges independently of the other coils and can be connected to a current source via the two electrical half-bridges.

[0043] Aspect 2 electric motor according to aspect 1, wherein the electric motor has control electronics designed to control the half-bridges in such a way that each of the coils generates an alternating magnetic field.

[0044] Aspect 3 electric motor according to aspect 2, wherein the control electronics are designed to control the half-bridges in such a way that the magnetic fields of the coils change in a phase-shifted manner relative to each other.

[0045] Aspect 4 Electric motor according to one of aspects 2 or 3, wherein the control electronics have several current measuring elements, and each of the several current measuring elements is provided in one of the series circuits, preferably between one of the half-bridges and the corresponding coil, and wherein each of the several current measuring elements is configured to generate a current signal that corresponds to a current applied to the corresponding coil.

[0046] Aspect 5 electric motor according to one of aspects 2 to 4, wherein the control electronics has several controllers, preferably pulse width modulation controllers, and each of the controllers is assigned to a coil, preferably each of the controllers is connected in a signal-communicating manner to the two half-bridges of the respective coil connected in series.

[0047] Aspect 6 electric motor according to aspect 5 in combination with aspect 4, wherein each of the controllers is connected to the respective current measuring element via signal communication and the corresponding current signal is an input signal of the respective controller.

[0048] Aspect 7: Electric motor according to one of the preceding aspects, wherein one of the several coils has a number of turns and / or a wire gauge that differs from the number of turns and / or the wire gauge of the other coils. Aspect 8: Electric motor according to one of the preceding aspects, wherein at least a part of the half-bridges comprises a semiconductor element having gallium nitride or preferably being configured as a gallium nitride semiconductor element.

[0049] Aspect 9 aircraft, preferably eVTOL aircraft, with

[0050] (a) an electric motor according to one of the preceding aspects, wherein

[0051] (b) the electric motor is designed to drive a lift-generating and / or thrust-generating device of the aircraft, preferably an aircraft rotor.

[0052] Aspect 10: Aircraft according to Aspect 9, wherein the rotor of the electric motor is mechanically connected to the lift-generating and / or propulsion-generating device of the aircraft.

[0053] Aspect 11 Aircraft according to one of aspects 9 or 10 in combination with one of aspects 2 to 6, wherein the aircraft has a flight control device for controlling the lift-generating and / or thrust-generating device, which is electrically isolated and communicates signals with the control electronics of the electric motor, preferably with the controllers of the control electronics of the electric motor.

[0054] Aspect 12 aircraft according to aspect 11, wherein the flight control device is connected to the control electronics via optocouplers.

[0055] Aspect 13 Aircraft according to Aspect 12, wherein the flight control device has several independent flight control computers and each of the flight control computers is connected to each of the controllers by means of a signal and preferably each of the flight control computers is electrically isolated from each of the controllers.

[0056] Aspect 14: Aircraft according to one of aspects 9 to 13, wherein the aircraft has several independent power sources, and the electric motor is configured to electrically connect the several power sources. Aspect 15: Aircraft according to one of aspects 9 to 14, wherein the electric motor is connected to a battery and a second power source independent of the battery, the battery being electrically connectable to the second power source via the electric motor.

[0057] Aspect 16 Aircraft according to aspect 15, wherein the electric motor in flight operation of the aircraft can be supplied with electrical current from the battery and / or from the second power source.

[0058] Brief description of the drawings

[0059] The various exemplary features described above can be combined with one another, provided this is technically feasible and appropriate. Further combinable features, advantages, and embodiments of the invention will become apparent from the following description of exemplary embodiments and with reference to the figures. These show:

[0060] Figure 1 shows a schematic side view of an embodiment of an aircraft with multiple electric motors.

[0061] Figure 2 shows a simplified circuit diagram of a 3-phase center-point electric motor known from the prior art.

[0062] Figure 3 shows a simplified partial circuit diagram of an exemplary embodiment of an electric motor.

[0063] Figure 4 shows another simplified partial circuit diagram of the electric motor based on the embodiment in Figure 3.

[0064] Figure 5 shows another simplified partial circuit diagram of the electric motor based on the embodiment in Figure 4, and

[0065] Figure 6 shows a schematic arrangement of several electric motors according to one of the aforementioned embodiments.

[0066] Ways to Implement the Invention Figure 1 shows a schematic side view of an embodiment of an aircraft 1. The aircraft 1 shown is an eVTOL aircraft 1, i.e., an exclusively electrically powered aircraft 1 with the capability for vertical takeoff and landing. In alternative embodiments, the aircraft can also be designed as a hybrid-powered multicopter 1. This means that the alternative multicopter 1 has several different energy sources, for example, a fuel cell, a gas turbine, and / or a battery as an electrical power source.

[0067] The aircraft 1 comprises several lift-generating and / or thrust-generating devices 2, which are designed as aircraft rotors 2. During a vertical takeoff and / or landing maneuver or hovering operation, the aircraft rotors 2 generate a vertical thrust force. When the angle of attack of the aircraft 1 is changed, the aircraft rotors 2 also generate a horizontal thrust component (propulsion-generating). For the sake of clarity, in the embodiment shown in Figure 1, only a portion of the aircraft rotors 2 have been designated with the reference numeral 2.

[0068] Each of the aircraft rotors 2 is driven by an electric motor 10. For clarity, only some of the electric motors 10 are designated with the reference numeral 10. Each electric motor 10 comprises a stator 11 (not shown in Figure 1) and a rotor 24 (not shown in Figure 1). The stator 11 is designed to generate a variable magnetic field. For this purpose, the stator 11 includes several coils 12, the operation of which is explained in more detail below. The rotor 24 is designed to rotate when the magnetic field of the stator 11 changes. The rotor 24 of the electric motor 10 is mechanically connected to the corresponding aircraft rotor 2. Therefore, a rotation of the rotor 24 causes a corresponding rotation of the aircraft rotor 2.Regarding the detailed construction of the electric motors 10, reference is made to the dart divisions shown in Figures 3 to 6 and to the corresponding figure descriptions.

[0069] The aircraft 1 further comprises a flight control unit 3. The flight control unit 3 is preferably connected to a control input device in the cockpit of the aircraft 1 (not shown in Figure 1) via signal communication. This allows control inputs from a pilot in the cockpit of the aircraft 1 to be transmitted to the flight control unit 3. The flight control unit 3 is configured to control the electric motors 10 such that the rotational speed of the aircraft rotors 2 is adjusted so that the aircraft 1 executes a flight movement that corresponds to the pilot's control inputs. The flight control unit 3 is connected to the electric motors 10 via signal communication, in particular to corresponding control electronics for the respective electric motors 10.

[0070] Figure 2 shows a simplified circuit diagram of a 3-phase neutral-point electric motor 100 known from the prior art and not claimed in this patent application. The 3-phase neutral-point electric motor 100 has a stator 110 with three coils 111. The three coils 111 of the stator 110 are each connected at one electrical end to a common electrical ground (center of the 3-phase neutral-point electric motor 100 in Figure 2).

[0071] The 3-phase neutral-point electric motor 100 is controlled by a pulse width modulation controller 200, the simplified structure of which is shown in Figure 2. The coils 111 are connected to the pulse width modulation controller 200 in such a way that they can be electrically connected to a battery 300 via the controller. As shown in Figure 2, the pulse width modulation controller 200 has three half-bridges connected in parallel, each of which is assigned a coil 111 of the 3-phase neutral-point electric motor 100.

[0072] The electric motors 10 of aircraft 1 shown in Figure 1 could each be replaced by a 3-phase neutral-point electric motor 100 and an associated pulse-width modulation controller 200 as shown in Figure 2. However, this would have the disadvantage that, for example, a loose connection at the common ground terminal of the coils 111 would jeopardize the functionality of the entire 3-phase neutral-point electric motor 100 or cause the 3-phase neutral-point electric motor 100 to fail. The same would be the case if the pulse-width modulation controller 200 failed. Furthermore, the coils 111 can only be supplied with electrical energy via a common power source 300 (battery 300). Redundancy in the power supply is therefore not possible with the 3-phase neutral-point electric motor 100 shown in Figure 2. Figure 3 shows a simplified partial circuit diagram of one of the electric motors 10 in Figure 1.For the sake of clarity, only one coil 12 of the stator 11 of the electric motor 10 is shown in Figure 3. However, the stator 11 as a whole comprises several coils 12, preferably at least three coils 12.

[0073] The coil 12 is designed to generate a magnetic field when an electric current flows through it. When the current is disconnected, the magnetic field changes such that the coil no longer generates a magnetic field. When the direction of the current in the coil 12 is reversed, the magnetic field changes such that the magnetic field lines change direction.

[0074] The coil 12 is connected in series with two electrical half-bridges 13, 14, namely a first half-bridge 13 and a second half-bridge 14. The coil 12 is positioned between the two electrical half-bridges 13, 14 and can be connected to the power source 4 via the two electrical half-bridges 13, 14. The power source 4 is shown in Figure 3 as a busbar that is electrically connected to a DC power source, for example, a battery.

[0075] Each of the two half-bridges 13, 14 has two electrical switches 13.1, 13.2, 14.1, 14.2. The first half-bridge 13 comprises, in particular, a first switch 13.1 and a second switch 13.2. The second half-bridge 14 has a first switch 14.1 and a second switch 14.2. The switches 13.1, 13.2, 14.1, 14.2 are shown in Figure 3 as simple switching elements. In preferred embodiments, however, the switches 13.1, 13.2, 14.1, 14.2 are each designed as semiconductor elements 13.1, 13.2, 14.1, 14.2, particularly preferably as gallium nitride semiconductor elements 13.1, 13.2, 14.1, 14.2.

[0076] This electrical configuration of the stator 11 allows coil 12 to be supplied with or disconnected from electrical current completely independently of any other coils 12 of the stator 11. Additionally, the current direction in coil 12 can also be changed independently of any other coils 12 of the stator 11.

[0077] For example, if the first switch 13.1 of the first half-bridge 13 is closed, the second switch 13.2 of the first half-bridge 13 remains open, and the second switch 14.2 of the second half-bridge 14 is closed, while the first switch 14.1 of the second half-bridge 14 remains open, the coil 12 is supplied with electric current such that the current flows clockwise through the series circuit. This generates a first magnetic field through the coil 12.

[0078] When the first switch 13.1 of the first half-bridge 13 is opened and the second switch 13.2 of the first half-bridge 13 is closed, and the second switch 14.2 of the second half-bridge 14 is opened and the first switch 14.1 of the second half-bridge 14 is closed, the coil 12 is supplied with electric current such that the current flows counterclockwise through the series circuit. This generates a second magnetic field in the coil 12, which opposes the first magnetic field. If the switches 13.1, 13.2, 14.1, 14.2 are repeatedly switched back and forth between the two aforementioned positions, the coil 12 generates an alternating magnetic field.

[0079] Additionally or alternatively, switches 13.1, 13.2, 14.1, and 14.2 can also be configured so that coil 12 is completely connected to electrical ground. For this purpose, the first switch 13.1 of the first half-bridge 13 and the first switch 14.1 of the second half-bridge 14 are opened, and the second switch 13.2 of the first half-bridge 13 and the second switch 14.2 of the second half-bridge 14 are closed. In this situation, no magnetic field is generated by coil 12. However, the rotor is actively braked in this switch position.

[0080] When all switches 13.1, 13.2, 14.1, 14.2 are opened, the coil has two unconnected ends and the electric motor 10 is in freewheeling mode.

[0081] Figure 4 shows a simplified partial circuit diagram of the series connection of the electric motor 10 according to the embodiment in Figure 3. The electric motor 10 is arranged in the aircraft 1 according to the embodiment shown in Figure 1. The circuit of one coil 12 of the stator 11 of the electric motor 10, as shown in Figure 3, is modified in Figure 4 such that a current measuring element 15 is arranged in series between the coil 12 and the second half-bridge 14. Otherwise, the circuit corresponds to the embodiment shown in Figure 3.

[0082] The current measuring element 15 is configured to detect the current at the coil 12 and output a current signal 16 that corresponds to the detected current at the coil 12. The current signal 16 is an input signal for a pulse width modulation controller 18. The pulse width modulation controller 18 is preferably arranged inside the electric motor 10. Independently of the foregoing, the pulse width modulation controller 18 is configured to output control signals 19 to the two half-bridges 13, 14 and, in particular, to control the switch positions of switches 13.1, 13.2, 14.1, 14.2 by means of the control signals 19. For controlling the two half-bridges 13, 14, the pulse width modulation controller 18 also receives a voltage signal 17 that corresponds to the voltage at the current source 4 or the bus bar 4.

[0083] The pulse width modulation controller 18 receives control signals 20 from the flight control unit 3 and outputs feedback signals 21 to the flight control unit 3. The pulse width modulation controller 18 and the flight control unit 3 are connected to each other via an optocoupler 22. Simultaneously, the optocoupler 22 electrically isolates the pulse width modulation controller 18 and the flight control unit 3 from each other. Alternative embodiments may use signal transformers or other isolators instead of the optocoupler 22. The technically relevant aspect is that control signals 20 and / or feedback signals 21 can be exchanged between the flight control unit 3 and the pulse width modulation controller 18, while the flight control unit 3 remains electrically isolated from the pulse width modulation controller 18.

[0084] Figure 5 shows the electric motor 10, in particular the stator 11, as already described in Figure 4. In contrast to Figure 4, however, Figure 5 shows four coils 12.1, 12.2, 12.3, 12.4 of the stator 11.

[0085] As can be clearly seen in Figure 5, all coils 12.1, 12.2, 12.3, 12.4 of the stator 11 can be energized independently of the other coils 12.1, 12.2, 12.3, 12.4 and can therefore generate independently variable magnetic fields. In the embodiment shown in Figure 5, two different and independent current sources 4.1, 4.2 are provided. Accordingly, a first coil 12.1 and a second coil 12.2 can each be connected to the first current source 4.1 and a first busbar of the first current source 4.1, respectively, via two half-bridges 13, 14. A third coil 12.3 and a fourth coil 12.4 can each be connected to the second current source 4.2 and a second busbar of the second current source 4.1, respectively, via two corresponding half-bridges 13, 14. Another difference from the embodiment shown in Figure 4 is that the flight control device 3 has three independent flight control computers 3.1, 3.2, 3.3 comprises. Each of the flight control computers 3.1, 3.2, 3.3 is connected via optocouplers 22 to all pulse width modulation controllers 18 for signal communication.

[0086] To further improve the control quality of the pulse width modulation controllers 18, three encoders 23 are provided. Each encoder 23 is configured to output rotary position signals to the pulse width modulation controllers 18. These rotary position signals preferably correspond to the corresponding rotary positions or rotational orientations of the rotor 24 of the electric motor 10 (not shown in Figure 5).

[0087] Figure 6 shows a schematic arrangement of several electric motors 10 according to one of the aforementioned embodiments. When the magnetic fields of the coils 12 of an electric motor 10 change, in particular when they change out of phase with each other, this causes the rotor 24 to rotate. This is due to the fact that the respective rotor 24 has several permanent magnets 25 which are attracted or repelled by the changing magnetic fields.

[0088] Each of the electric motors is electrically connected to a first power source 4.1, in particular a battery 4.1. The battery 4.1 can supply current to at least some of the coils 12 of the respective electric motor 10. In Figure 6, this is shown, by way of example, as the lower coils 12 of the electric motors 10.

[0089] Each electric motor 10 has several track switches 26. Depending on the switching position of the track switches 26, the batteries 4.1 can supply power to all coils 12 of the respective electric motor 10.

[0090] Independently of the above, each of the electric motors 10 is also connected to a second power source 4.2, namely an external charging port 2.2. A further alternative power source 4.3, for example a gas turbine 4.3 and / or a fuel cell 4.3, is also connected to each of the electric motors 10. This allows the electric motor 10 to be supplied with electrical current from several independent power sources 4.1, 4.2, 4.3. The electrical load that each of the electric motors 10 draws from the respective power source 4.1, 4.3 can differ. For example, one of the electric motors 10 can draw 6 kW of electrical power from the alternative power source 4.3 and 4 kW from the corresponding battery 4.1, resulting in a total motor power of 10 kW. The other electric motors 10 can have the same and / or a different power distribution.

[0091] The power distribution between battery 4.1 and alternative power source 4.3 can be adjusted, in particular to maintain a balanced state of charge in the batteries 4.1, to preserve a minimum residual charge in each battery 4.1 for an emergency landing, and / or to load the alternative power source 4.3 sufficiently so that it operates at its most efficient point. In some operating conditions, it would be conceivable for part of the electric motor 10, in particular part of the coils 12, to function as a generator and feed current back into battery 4.1, while the other part of the electric motor 10, in particular the other coils 12, functions as described above and consumes current to change the magnetic field or operates at idle. This is particularly advantageous when the rotational speed of the rotor 24 needs to be reduced rapidly. In this case, for example, the corresponding battery 4.1 can be used to...1 connected coils 12, which act as a generator, slow down the rotor 24.

[0092] Each of the electric motors 10 has busbar switches 26. The lower part of the coils 12 of the corresponding electric motor 10 can also be electrically connected to the second power source 4.2 and / or the alternative power source 4.3 via the busbar switches 26. Conversely, the upper part of the coils 12 of the corresponding electric motor 10 can be electrically connected to the respective battery 4.1. This allows the electric motor 10 to obtain the electrical energy required for operation exclusively from only one of the power sources 4.1, 4.2, 4.3, in particular from the battery 4.1 or the gas turbine 4.3 / fuel cell 4.3.

[0093] In alternative embodiments, the electric motor 10 can also be segmented into three or four segments with three or four power supplies. This is advantageous, for example, if two batteries 4.1 per electric motor 10 and a common alternative power source 4.3 for all electric motors 10 are provided. Independently of the above, the busbar switches 26 of the electric motors 10 allow the power sources 4.1, 4.2, and 4.3 to exchange electrical energy with each other. For example, the batteries 4.1 can thus be charged by the second power source 4.2 and / or the alternative power source 4.3. During operation of the electric motors 10, including during flight of the aircraft 1, the batteries 4.1 can be charged, in particular, by the alternative power source 4.3.

[0094] Once the aircraft has landed and is being refueled / charged, several options are available: Refueling the alternative power source 4.3, i.e., the gas turbine 4.3 and / or the fuel cell 4.3, which can also be used to generate electricity for charging the batteries 4.1. For this, the busbar switches 26 would be closed. Alternatively or additionally, the batteries 4.1 could be charged via the external charging port 2.2 with the busbar switch 26 closed.

[0095] If the batteries 4.1 are at different charge levels (different voltage levels), the track switches 26 cannot simply be closed. To bring all batteries 4.1 to the same charge level, the most discharged battery 4.1 could first be connected to the second power source 4.2 and / or the alternative power source 4.3 via the track switches 26. This charges the corresponding battery 4.1 until it reaches the same voltage as the second most discharged battery 4.1. Once both batteries 4.1 reach the same voltage, the second most discharged battery 4.1 is connected to the corresponding electric motor 10 via the corresponding track switches 26. This process is continued until all batteries have reached the same charge level.

[0096] Reference symbol list

[0097] 1 aircraft

[0098] 2 aircraft rotors

[0099] 3 Flight control system

[0100] 3.1 Flight control computer

[0101] 3.2 Flight control computer

[0102] 3.3 Flight control computer

[0103] 4 Power source

[0104] 4.1 First power source / battery

[0105] 4.2 Second power source / charging port

[0106] 4.3 Alternative power source / fuel cell and / or gas turbine

[0107] 10 Electric motor

[0108] 11 Stator

[0109] 12 coils

[0110] 12.1 first coil

[0111] 12.2 second coil

[0112] 12.3 third coil

[0113] 12.4 fourth coil

[0114] 13 first electric half-bridge

[0115] 13.1 First switch of the first electrical half-bridge

[0116] 13.2 Second switch of the first electrical half-bridge

[0117] 14 second electric half-bridge

[0118] 14.1 First switch of the second electrical half-bridge

[0119] 14.2 Second switch of the second electrical half-bridge

[0120] 15 Current measuring element

[0121] 16 Current signal

[0122] 17 Voltage signal

[0123] 18 pulse width modulation controllers

[0124] 19 Control signal of the pulse width modulation controller

[0125] 20 Control signal of the flight control system

[0126] 21 Feedback signal 22 Optocoupler

[0127] 23 encoders

[0128] 24 Rotor of the electric motor

[0129] 25 Permanent magnet of the electric motor rotor 26 Busbar switch

[0130] 100 electric motor (state of the art)

[0131] 110 Stator (state of the art)

[0132] 111 Coil (state of the art) 200 Pulse width modulation controller (state of the art)

[0133] 300 battery (state of the art)

Claims

1. Patent claims 1. Electric motor for an aircraft, the electric motor comprising: (a) a stator for generating variable magnetic fields, and (b) a rotor rotatable with respect to the stator, designed to perform a rotational movement when the magnetic fields generated by the stator change, wherein (c) the stator has several, preferably at least three, electrical coils, each independently configured to generate a variable magnetic field, wherein (d) each of the coils is connected in series between two electrical half-bridges independently of the other coils and can be connected to a power source via the two electrical half-bridges.

2. Electric motor according to claim 1, wherein the electric motor has control electronics configured to control the half-bridges such that each of the coils generates an alternating magnetic field for rotating the rotor.

3. Electric motor according to claim 2, wherein the control electronics have several current measuring elements, wherein one of the several current measuring elements is provided in one of the series circuits, preferably between one of the half-bridges and the corresponding coil, and wherein each of the several current measuring elements is configured to generate a current signal that corresponds to a current applied to the corresponding coil.

4. Electric motor according to one of claims 2 or 3, wherein the control electronics has several controllers, preferably pulse width modulation controllers, and each of the controllers is assigned to a coil, preferably each of the controllers is connected in a signal-communicating manner to the two half-bridges of the respective coil connected in series.

5. Electric motor according to claims 3 and 4, wherein each controller is connected to the respective current measuring element via signal communication and the corresponding current signal is an input signal of the respective controller.

6. Electric motor according to one of the preceding claims, wherein one of the several coils has a number of turns and / or a wire thickness that differs from the number of turns and / or the wire thickness of the other coils.

7. Electric motor according to one of the preceding claims, wherein at least part of the half-bridges comprises a semiconductor element having gallium nitride, preferably designed as a gallium nitride semiconductor element.

8. Aircraft, preferably an eVTOL aircraft, with (a) an electric motor according to any one of the preceding claims, wherein (b) the electric motor is designed to drive a lift-generating and / or propulsion-generating device of the aircraft, preferably a rotor of the aircraft.

9. Aircraft according to claim 8 in combination with one of claims 2 to 5, wherein the aircraft has a flight control device for controlling the lift-generating and / or thrust-generating device, which is connected in a signal-communicating and electrically isolated manner, preferably via an optocoupler, to the control electronics of the electric motor, preferably to the controllers of the control electronics of the electric motor.

10. Aircraft according to one of claims 8 or 9, wherein the aircraft has several independent power sources and the electric motor is configured to electrically connect the several power sources together.

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