Arrangement for an electric machine

Abstract

An arrangement (1) for an electric machine (2; 2') comprises: an assembly (21) having a body (10) and multiple windings (12A-12C), each of which has a first electrical conductor (120) and a second electrical conductor (121) that are wound at least in one winding section (122) along a winding axis (A) and alternate in at least one direction, in particular in the direction of the winding axis (A); multiple sensors (140) arranged at at least two points (X1, X2, X5, X6) of the first electrical conductor (120) and two points (X3, X4, X7, X8) of the second electrical conductor (121) of at least one of the windings (12A-12C) in order to measure a respective electrical variable; and a unit (131) set up to measure a first difference between the electrical variable at the two points (X1, X2, X5, X6) of the first electrical conductor (120) and a second difference between the electrical variable at the two points (X3, X4, X7, X8) of the second electrical conductor (121) and to output an output signal based on a deviation between the first difference and the second difference.

Description

[0001] Arrangement for an electrical machine

[0002] Description

[0003] The present disclosure relates in particular to an arrangement for an electrical machine, an electrical machine having such an arrangement, an aircraft having such an electrical machine and a method for monitoring an electrical machine.

[0004] Such arrangements comprise an assembly with a body, e.g., in the form of a laminated core, and several windings, which, for example, are wound around the body's teeth. By applying voltages, particularly those that vary over time, to the windings, magnetic fields are generated, which, for example, cause a relative movement between the assembly and another assembly. The assembly is, for example, a stator, and the other assembly is a rotor.

[0005] Especially in multi-phase rotating field machines, especially those with a permanent magnet rotor, it proves problematic when a turn-to-turn short circuit occurs within a winding. The problem with such electrical machines is that a turn-to-turn short circuit during normal operation can induce a large electrical current, which can lead to thermal destruction of the windings. This is particularly relevant, not only but especially, in aircraft, where permanent magnet rotating field machines are used.

[0006] If, for example, such a winding short circuit is detected, the electrical machine, or part of it, can be shut down. However, in the aviation sector, such a shutdown can have far-reaching consequences. It is therefore advisable to only perform such a shutdown when absolutely necessary.

[0007] The object of the present invention is to provide an arrangement for an electrical machine that is as reliable as possible.

[0008] According to one aspect, an arrangement for an electrical machine is specified, comprising an assembly with a body and a plurality of windings (e.g. tooth windings), each of which has a first electrical conductor and a second electrical conductor, which are wound at least on one winding section along a winding axis (e.g. around the same tooth of a plurality of teeth fixed to the body) and in this case, e.g.alternating in the direction of the winding axis; a plurality of sensors arranged at least at two locations on the first electrical conductor and two locations on the second electrical conductor of at least one of the windings, each to detect an electrical quantity; and a unit configured to detect a first difference in the electrical quantity at the two locations on the first electrical conductor and a second difference in the electrical quantity at the two locations on the second electrical conductor and to output an output signal based on a deviation between the first difference and the second difference.

[0009] Such an arrangement makes it possible to detect a turn-to-turn short circuit between adjacent turns of a winding section, i.e. between the corresponding first and second electrical conductors, particularly reliably in order to initiate countermeasures, such as switching off the power supply, and to shut down an electrical machine with the arrangement in safe operation in order to avoid dangerous operating conditions. By detecting the deviation between the first difference and the second difference, it can be determined whether the detected difference or differences are a measurement error resulting from a defective sensor or an actual short circuit. This can prevent unnecessary shutdowns. At least at the winding section or sections (optionally completely), the first electrical conductor and the associated second electrical conductor are electrically insulated from one another.The absolute values ​​of the differences can always be used. The unit can also be referred to as an evaluation unit or analysis unit. The unit can comprise a microcontroller or, alternatively, simply an analog circuit.

[0010] The sensors are designed, for example, as current sensors for measuring the current flowing through the respective electrical conductor. The current sensor includes, for example, a Hall sensor and / or a loop sensor. This enables fault detection based on current signals using two separate electrical conductors. This enables reliable detection of short circuits.

[0011] The at least two points of the respective electrical conductor can be electrically connected to each other via the respective winding section. This enables a differential measurement, which allows for particularly reliable fault detection.

[0012] For example, the unit is configured to output the output signal when the deviation is greater than a predefined deviation threshold, which indicates a sensor fault. A short circuit between turns affects both electrical conductors. By detecting that the two difference values ​​are different, the unit can conclude that there is no short circuit between turns, but rather a sensor fault.

[0013] The unit can be configured to output an output signal indicating a line fault if the first difference and / or the second difference is / are greater than a predefined difference threshold and the deviation is less than a predefined deviation threshold. Thus, if the same difference is measured on both electrical conductors within the measurement accuracy, the unit can conclude that there is no sensor fault, but in fact a short circuit.

[0014] The unit can be configured to output the output signal only if the first difference and / or the second difference is greater than the specified difference threshold over a specified period of time. In this way, short fluctuations in the measured signals, e.g., due to noise from external disturbances, can be filtered out.

[0015] Optionally, the unit is configured to record the first difference and / or the second difference as an average value over a predetermined time window. In this way, fluctuations in the measured signals can be smoothed out. For example, the unit is configured to determine the first difference and / or the second difference as an RMS value. Alternatively or additionally, the unit is configured, for example, to extract a predetermined frequency range from values ​​of the recorded electrical quantity by means of filtering, in particular bandpass filtering, and to further analyze this partial signal, in particular by the described difference formation. The predetermined frequency range is, for example, aligned with one or more characteristic frequencies in the signals.

[0016] Optionally, a sensor is arranged at one of the at least two locations of the first electrical conductor and / or a (further) sensor is arranged at one of the at least two locations of the first electrical conductor and / or a (further) sensor is arranged at one of the at least two locations of the second electrical conductor and / or a (further) sensor is arranged at one of the at least two locations of the second electrical conductor. This enables precise measurement with a simple structure.

[0017] Alternatively or additionally, a sensor for measuring a differential current of the first electrical conductor is optionally arranged at points on the first electrical conductor that are electrically connected to one another via the winding section, and / or a (further) sensor for measuring a differential current of the second electrical conductor is arranged at points on the second electrical conductor that are electrically connected to one another via the winding section. This enables particularly precise measurement with a small number of sensors.

[0018] The arrangement may comprise an inverter, in particular with multiple inverter units, each for one electrical phase of a multi-phase alternating voltage. This allows the use of a DC voltage source such as a battery. The inverter units are optionally electrically connected to the first electrical conductors of each of the windings and / or the inverter units are electrically connected to the second electrical conductors of each of the windings. All inverter units can be powered by the same energy source.

[0019] The arrangement comprises, for example, (in particular, exactly) three windings, each for one phase of a three-phase alternating current. Thus, the arrangement comprises, for example, a total of six (first and second) electrical conductors.

[0020] All first electrical conductors of each of the windings can be electrically connected to one another at a (first) star point. Furthermore, all second electrical conductors of each of the windings can be electrically connected to one another at a (second) star point. This enables a particularly simple design. The arrangement can comprise one or more voltage sensors as sensor(s). Optionally, the voltage sensor (or the voltage sensors) is (are) connected in such a way that it (they) can measure a voltage at one or both star points, e.g. with reference to an earth potential. Alternatively or additionally, a voltage sensor is connected to both star points in order to measure a voltage between the star points.

[0021] The first and second electrical conductors are arranged in particular (at least in at least one winding section) in a bifilar configuration. Because the windings of the first and second electrical conductors are arranged in a bifilar configuration, an interturn short circuit can initially occur between the first and second electrical conductors. If the partial windings formed by the first and second electrical conductors are electrically charged, the effect of an interturn short circuit can thus be significantly reduced.

[0022] For example, each of the first electrical conductors of the windings runs around each of a plurality of teeth and / or each of the second electrical conductors of the windings runs around each of a plurality of teeth, in particular each around the same teeth as the associated first electrical conductor.

[0023] According to one aspect, an arrangement for an electrical machine is specified, in particular according to any of the embodiments described above. The arrangement comprises an assembly with a body and a plurality of windings. The windings each have a first electrical conductor and a second electrical conductor, which are wound at least on one winding section along a winding axis (e.g. around the same tooth of a plurality of teeth fixed to the body) and alternate in at least one direction, in particular in the direction of the winding axis. The first electrical conductors of the windings are electrically connected to one another at a first star point. The second electrical conductors of the windings are electrically connected to one another at a second star point. The arrangement further comprises a first inverter arrangement with inverter units and a second inverter arrangement with further inverter units.The inverter arrangements each have an inverter unit for each phase of a multi-phase (e.g. three-phase) alternating electrical voltage, wherein each of the first electrical conductors of the windings is electrically connected to a.

[0024] Inverter unit of the first inverter arrangement and each of the second electrical conductors of the windings is electrically connected to a

[0025] Inverter unit of the second inverter arrangement is connected. The arrangement further comprises one or more sensors (each) for detecting measured values ​​of an electrical quantity (e.g. current strength) of one or more of the first or second electrical conductors, and a unit. The unit is configured to receive the measured values ​​of the sensor or sensors, to determine at least one value indicative of a sum of the electrical quantity of the first electrical conductors and / or the second electrical conductors based on one or more of the measured values, and to output an output signal based on the determined at least one value.Such an arrangement also makes it possible to detect a turn-to-turn short circuit between adjacent turns of a winding section, i.e. between the corresponding first and second electrical conductors, particularly reliably, in order to initiate countermeasures, such as the aforementioned switching off of the power supply, and to shut down an electrical machine with the arrangement in safe operation in order to avoid dangerous operating conditions. If the sum of the measured values ​​of the electrical quantity, e.g. current intensity (or one of the sums), is significantly different from zero, this can indicate a turn-to-turn short circuit, since the alternating conductors at the short-circuited point can cause current to flow from a conductor connected to one of the inverter arrangements to a conductor connected to the other of the inverter arrangements. In a conventional e.g.In contrast, in a three-phase electrical machine, in the event of an interturn short circuit, only the conductor (forming a loop) is short-circuited with itself, so that a short circuit cannot be easily detected from the sum of the electrical quantities of the first or second electrical conductors (this applies particularly to electrical machines with low inductance). If both sums are equally different from zero, a sensor error can also be ruled out, which would only lead to a result different from zero in one of the two sums. In particular, if the individual sensors have different characteristic curves, the unit can be designed to calibrate one or both sensors.

[0026] The unit can be configured to determine, based on one or more of the measured values, a (first) value indicative of a sum of the electrical quantity of the first electrical conductors and / or, based on one or more of the measured values, to determine a (second) value indicative of a sum of the electrical quantity of the second electrical conductors. The unit can be configured to determine, based on one or more of the measured values, a (first) sum of the currents through the first conductors as the value and / or to determine a (second) sum of the currents through the second conductors as the value (or as a further value). The unit can further be configured, e.g., based on the determined sum (or sums), to determine a first zero-sequence current of the first electrical conductors and / or a second zero-sequence current of the second electrical conductors.For this purpose, the control unit calculates IO = 1 / 3 * (lu+lv+lw), where IO indicates the zero-sequence current, while lu, Iv and Iw indicate the currents of the respective phases (through the respective first or second electrical conductors).

[0027] Furthermore, the unit can be configured to detect a fault in one of the first conductors if the first value and / or the first zero-sequence system current (e.g. the maximum amplitude of the first zero-sequence system current) exceeds a predetermined threshold value. Alternatively or additionally, the unit is configured, for example, to detect a fault in one of the second conductors if the second value and / or the second zero-sequence system current (e.g. the maximum amplitude of the second zero-sequence system current) exceeds a predetermined threshold value. It can be provided that the output signal indicates a fault if the control unit has detected a fault in one of the first conductors and / or has detected a fault in one of the second conductors. In this way, the probability of a false alarm, e.g. due to measurement errors, can be significantly reduced. The two values ​​can therefore be checked for plausibility.If both deviate in the same way (especially from zero) (especially with the same or calibrated sensor characteristics), then there is a fault in one conductor.

[0028] In one embodiment, the unit is configured to detect the presence of a first fault type if either a fault is present in one of the first conductors or sensors (but no fault is detected by the sensors of the second conductors) or a fault is present in one of the second conductors or sensors (but no fault is detected by the sensors of the first conductors). Furthermore, the unit can be configured to detect the presence of a second fault type if a fault is present in one of the first conductors and a fault is present in one of the second conductors (in this case, the same fault can be excluded in both sensors due to the probabilities). In this way, different fault states can be detected and displayed. For example, the output signal indicates a sensor fault if the unit detects the first fault type and an insulation fault if the unit detects the second fault type.If a turn-to-turn short circuit occurs due to an insulation fault, currents flow between the conductors of what are essentially separate conductor systems. This results in non-zero zero-sequence currents (and sums) in both conductor systems. However, if a fault is detected in only one of the two conductor systems, the cause is a measurement error, e.g., due to a defective sensor.

[0029] One of the sensors can be arranged on each of the first and second electrical conductors. The sensors can be arranged in the respective inverter unit or between the respective inverter unit and the respective (in particular the nearest) winding section connected to it. This enables particularly simple connection of the sensors.

[0030] The sensors of the first electrical conductors can be connected in series. Alternatively or additionally, the sensors of the second electrical conductors can be connected in series. The two rows can be electrically connected to each other at one of their ends, i.e., connected in series. A sensor, e.g., a voltage sensor, can be connected to the other ends of the rows. The voltage sensor is, for example, part of a voltage measuring instrument. Thus, reliable detection of an insulation fault can be achieved with a particularly simple circuit using only one sensor.

[0031] The sensor or one of the sensors can encompass several, in particular all, of the first electrical conductors. Alternatively or additionally, the sensor or one of the sensors can encompass several, in particular all, of the second electrical conductors. Thus, with only one sensor (in each case), a value can be determined that is proportional to the zero-sequence current of the respective conductor system. It should be noted at this point that the sensors can be arranged inside the electrical machine or outside the electrical machine.

[0032] The first star point and the second star point can be located on the same side of the body. This facilitates simple assembly. Alternatively, the first star point and the second star point can be located on opposite sides of the body. This can simplify wiring.

[0033] The sensor(s) can be designed as current sensors for measuring a current through the respective electrical conductor(s). The current sensor(s) can (each) comprise a Rogowski coil. This enables simple yet robust measurement of the current. Instead of or in addition to a Rogowski coil, the sensor (or each of several sensors) can be another current transformer, e.g., one that uses the Hall effect for measurement. The sensor (or sensors) can (each) comprise a Hall element and / or a magnetic core that at least partially surrounds the conductor.

[0034] The unit can be configured to determine at least one harmonic of the value over time and to output the output signal based thereon, in particular to output the output signal indicating a fault, in particular an insulation fault, based on a change in the at least one harmonic over time. This allows for particularly reliable fault detection.

[0035] According to one aspect, an electrical machine is provided. The electrical machine comprises the arrangement according to any embodiment described herein, e.g., as a stator. The electrical machine further comprises a further assembly, e.g., as a rotor, wherein the assembly and the further assembly are movable, in particular rotatable, relative to one another.

[0036] In the case of an electric machine, for example, the stator is provided as a stator and has a substantially circular opening to accommodate a rotor designed as a rotor. The rotor is arranged in the opening, for example in a rotatable manner, with an air gap formed between the rotor and the stator. This design is also referred to as an internal rotor. Alternatively, a design is provided in which the rotor radially surrounds the stator. Such designs are also called external rotor. An electric machine is a device which converts electrical energy into mechanical energy, in particular kinetic energy, in motor operation, and / or mechanical energy into electrical energy in generator operation. The movement is, for example, a rotary movement carried out by the rotor. The stator is, for example, arranged in a rotationally fixed manner with respect to a bearing supporting the electric machine.A rotary movement is therefore in particular a rotary movement of the rotor relative to the stator.

[0037] According to one aspect, a vehicle, in particular an aircraft, is provided, comprising the electric machine according to any embodiment described herein, in particular for driving a thrust-generating device, e.g., a propeller. The advantages of the electric machine described herein are particularly evident in a vehicle, in particular in an aircraft. However, it should be noted that the arrangement can also be used, for example, in a gas pump, in a ship's engine, in a wind turbine, or generally in a generator.

[0038] According to one aspect, a method for monitoring an electrical machine is provided. The method comprises the following steps:

[0039] - applying electric current to a plurality of windings, each of which has a first electrical conductor and a second electrical conductor, which are wound at least on one winding section along a winding axis (e.g. around the same one of a plurality of teeth of the electrical machine fixed to a body) and alternate, for example, in the direction of the winding axis;

[0040] - detecting an electrical quantity with each of a plurality of sensors arranged at at least two locations on the first electrical conductor and two locations on the second electrical conductor of at least one of the windings;

[0041] - detecting, by means of a unit, a first difference in the electrical quantity at the two locations of the first electrical conductor and a second difference in the electrical quantity at the two locations of the second electrical conductor and determining a deviation between the first difference and the second difference; and

[0042] - Outputting, by means of the unit, an output signal based on the deviation. The method can utilize the arrangement and / or the electrical machine described above.

[0043] According to one aspect, a method for monitoring an electrical machine is provided. The method comprises the following steps:

[0044] - applying electrical current to a plurality of windings, each of which has a first electrical conductor and a second electrical conductor, which are wound at least on one winding section along a winding axis (e.g. around the same of a plurality of teeth of the electrical machine fixed to a body) and alternate in at least one direction, in particular in the direction of the winding axis, by means of a first inverter arrangement with inverter units and a second inverter arrangement with further inverter units, wherein the inverter arrangements each have an inverter unit for each phase of a multi-phase electrical alternating voltage,wherein each of the first electrical conductors of the windings is electrically connected to an inverter unit of the first inverter arrangement and each of the second electrical conductors of the windings is electrically connected to an inverter unit of the second inverter arrangement, and wherein the first electrical conductors of the windings are electrically connected to one another at a first star point and the second electrical conductors of the windings are electrically connected to one another at a second star point.

[0045] - detecting an electrical quantity of one or more of the first or second electrical conductors with each of one or more sensors.

[0046] - Receive, by means of a unit, the measured values ​​of the sensor or sensors.

[0047] - Determining, by means of the unit, based on one or more of the measured values, at least one value indicative of a sum of the electrical quantities of the first electrical conductors and / or the second electrical conductors. - Outputting, by means of a unit, an output signal based on the at least one value.

[0048] Embodiments will now be described by way of example with reference to the figures, in which:

[0049] Figure 1 is a schematic sectional view of a basic

[0050] Construction of a permanent magnet, three-phase electrical machine as an internal rotor;

[0051] Figure 2 is a schematic, perspective exploded view of a

[0052] Structure of an assembly in the form of a stator of the electrical machine according to Figure 1 with windings;

[0053] Figure 3 is a schematic representation of part of a winding of the

[0054] Assembly according to Figure 2, in which windings of a first and a second electrical conductor are arranged bifilarly;

[0055] Figure 4 is a schematic representation of a permanent magnet electrical machine for operation on a three-phase alternating voltage;

[0056] Figures 5 and 6 are schematic circuit diagrams of windings and inverter units of an inverter of the electrical machine according to Figure 2 and Figure 4 respectively;

[0057] Figure 7 is a circuit diagram of a differential protection device;

[0058] Figure 8 Switching signals for the inverter units;

[0059] Figure 9 is a block diagram of inverter components;

[0060] Figures 10 to 12 Block diagrams of components of

[0061] Differential protection devices for the windings of Figures 5 to 7;

[0062] Figure 13 shows a further schematic diagram of windings and inverter units of an inverter; Figures 14 and 15 show block diagrams of components of differential protection devices for the windings of Figure 13;

[0063] Figure 16 shows a further schematic diagram of windings and inverter units of an inverter;

[0064] Figures 17 and 18 are block diagrams of arrangements for measuring voltage differences between star points, e.g. one of the arrangements according to Figures 5-7 and 14;

[0065] Figure 19 an aircraft in the form of an airplane with an electrically driven propeller and the electric machine;

[0066] Figures 20 to 23 are schematic circuit diagrams of windings and inverter units for the electrical machine according to Figure 2 and Figure 4;

[0067] Figure 24 a Rogowski coil; and

[0068] Figure 25 shows a method for monitoring an electrical machine.

[0069] Figure 1 shows a schematic sectional view of a rotating electrical machine 2 in the form of a permanent-magnet synchronous machine. Figure 1 shows that the electrical machine 2 is designed as an internal rotor. The electrical machine 2 comprises an assembly 1 with a subassembly in the form of a stator 21, which has an opening (not designated), in particular a through-opening, in which a further subassembly in the form of a rotor 20 is rotatably mounted.

[0070] The stator 21 comprises a body 10 in the form of a laminated core, to which teeth are fixed, which are referred to below as stator teeth 11. The stator teeth 11 are aligned with an air gap L between the body 10 of the stator 21 and the rotor 20. The stator teeth 11 protrude radially from the body 10, in this case radially inward. The stator 21 has a stator winding which comprises a plurality of windings, which in the context of the present example are referred to merely as tooth windings 12A-12C. The stator winding is designed for three-phase operation, i.e., it is connected to a three-phase alternating voltage with phases II, V, W. During normal operation of the electrical machine 2, the stator winding is accordingly supplied with the alternating voltage. The electrical machine is a radial flux machine, but it should be noted that the electrical machine can also, for example,It could be designed as an axial flux machine or a transverse flux machine. In particular, the electrical machine can also be designed with a double air gap, whether as an axial flux machine or a transverse flux machine.

[0071] The rotor 20 is designed as a salient-pole rotor, which includes permanent magnets to provide the magnetic flux. In the present embodiment, the rotor 20 has exactly one magnetic north pole N and one magnetic south pole S. In alternative embodiments, more magnetic poles can also be provided alternating in the circumferential direction transverse to a rotational axis of the rotor 20 (relative to the stator 21).

[0072] The rotor 20 is rotatably mounted. During normal operation, the three-phase alternating voltage, whose phases U, V, and W are each phase-shifted by 120°, generates a rotating magnetic field which interacts with the permanent magnet field provided by the rotor 20, so that during motor operation, a corresponding rotary movement of the rotor 20 relative to the stator 21 can be induced. In the present case, the electrical machine 2 is intended to serve as a drive motor for a propeller of an aircraft. The electrical machine 2 is an electric motor. Figure 1 schematically shows the sections of the stator winding which are assigned to the respective phases U, V, and W. One of the tooth windings 12A-12C is assigned to each of the phases U, V, and W.

[0073] The stator winding of the electrical machine 2 is connected to a three-phase inverter 13 of the arrangement 1. Together with the inverter 13 connected to it, the arrangement 1 forms an electrical system. The inverter 13 provides the alternating electrical voltage with the three phases II, V, W. The inverter 13 draws the electrical energy required for its intended operation from an energy source 3 connected to the inverter 13. In the present embodiment, the energy source 3 is a direct voltage source that provides electrical energy from a suitable electrical energy storage device, for example, an accumulator or the like.Alternatively or additionally, a fuel cell and / or the like or, in the case of stationary applications, an energy supply from a public energy supply network may be provided, for which purpose a rectifier may be provided for converting an alternating current from the public energy supply network into direct current.

[0074] The inverter 13 has dedicated inverter units for providing the phases U, V, and W, which are explained in more detail below in connection with, for example, Figure 5. Each inverter unit has its own half-bridge circuit. The half-bridge circuits are connected to a DC intermediate circuit of the inverter 13 (not further shown in Figure 1) in order to be supplied with electrical energy. The DC intermediate circuits can have a voltage of 25 V or more, 100 V or more, or, for example, in the range of 800 to 3000 V.

[0075] It should be noted at this point that the half-bridge circuit comprises a series connection of two electronic switching elements (e.g. transistors) which are connected to the intermediate circuit DC voltage of the inverter 13. The electronic switching elements are operated in a clock mode, as explained in more detail below in connection with Figure 9, which, for example, provides clock patterns in the manner of a PWM signal. The corresponding phase U, V, W of the three-phase AC voltage is then available at a respective center tap of the half-bridge circuits. The inductance of the tooth windings 12A-12C provides appropriate filtering, so that a corresponding AC current is established for each of the phases U, V, W, which can be almost sinusoidal with suitable control of the inverter units. The arrangement 1 further comprises a unit, which is referred to here as control unit 131.In the example shown, the control unit 131 is (also) designed to control the inverter 13, but alternatively it could also be designed separately from an inverter control.

[0076] In this case, the inverter 13 is counted as part of the electrical machine 2, but together they can also be referred to as a machine-inverter system.

[0077] Figure 2 shows a schematic exploded view of the stator 21 of the electrical machine 2. It can be seen that the stator 21 has the body 10, in which the stator teeth 11 can be joined to the annular body 10 by means of a mechanical connection and thus secured thereto, in particular mechanically fixed. Alternatively, the stator teeth 11 are formed integrally with the body 10, for example, and secured thereto in this way.

[0078] The stator teeth 11 are equipped with respective winding sections 122 of the tooth windings 12A-12C. The stator winding has a plurality of tooth windings 12A-12C, specifically three in this case. A respective one of the tooth windings 12A-12C is generally arranged on at least one of the stator teeth 11. In this case, each of the tooth windings 12A-12C extends over several, here two (specifically two opposite), stator teeth 11. For this purpose, the tooth windings 12A-12C generally each have at least one, here several, namely two, winding sections 122. Each winding section 122 surrounds (exactly) one stator tooth 11.

[0079] Each of the tooth windings 12A-12C has a respective first electrical conductor 120, which is arranged on each of the winding sections 122 in a plurality of turns circumferentially around the respective stator tooth 11. Between the winding sections 122, the first electrical conductor 120 comprises one or more corresponding connecting sections, via which the sections of the first electrical conductor 120 at the winding sections 122 are electrically connected to one another. Each of the tooth windings 12A-12C further has a respective second electrical conductor 121, which is also arranged on each of the winding sections 122 in a plurality of turns circumferentially around the respective stator tooth 11.Between the winding sections 122, the second electrical conductor 121 comprises one or more corresponding connecting sections via which the sections of the second electrical conductor 121 at the winding sections 122 are electrically connected to one another.

[0080] The first electrical conductors 120 and the second electrical conductors 121 each have end sections to which they are connected in a manner described in more detail below. Between the respective end sections, the first electrical conductors 120 and the second electrical conductors 121 are electrically insulated from one another. The tooth windings 12A-12C are interconnected accordingly in the electrical machine 2, thus establishing the three-phase connection to the inverter 13.

[0081] Figure 3 shows a schematic representation of a winding section 122 of one of the tooth windings 12A-12C. The first electrical conductor 120 is wound around the stator tooth 11, not shown in Figure 3. The winding on the stator tooth 11 extends around and along a winding axis A. In the present case, the winding is designed in the manner of a coil elongated along the winding axis A. Depending on the design and construction, a multi-layer winding can also be provided, for example, in order to be able to achieve a correspondingly high magnetic flux with a predetermined electrical current.

[0082] Furthermore, the winding section 122 of the tooth winding 12A-12C comprises the respective second electrical conductor 121, which is electrically insulated from the first electrical conductor 120. The second electrical conductor 121 also has a plurality of windings arranged circumferentially around the same stator tooth 11, so that the winding extends on the stator tooth 11 around and along the winding axis A. The respective windings of the first and second electrical conductors 120, 121 are arranged bifilarly. This means that along the winding axis A of the winding section 122 (with the exception of the two outermost windings), one winding of the first electrical conductor 120 is always arranged between two adjacent windings of the second electrical conductor 121 (and vice versa).This has the advantage that in the event of an interturn short circuit between two adjacent turns, the interturn short circuit always occurs between the first electrical conductor 120 and the second electrical conductor 121. An interturn short circuit therefore does not occur within a winding of the same electrical conductor. This prevents large currents in the event of an interturn short circuit, and thus large thermal and electrical stresses.

[0083] Optionally, each first electrical conductor 120 and / or each second electrical conductor 121 consists of at least two individual conductors insulated from one another.

[0084] Figure 4 shows a schematic representation of an electrical machine 2' in the form of a synchronous machine which, in contrast to the electrical machine 2 according to Figures 1 and 2, is not six-pole, but now twelve-pole. The corresponding stator therefore has twelve stator teeth 11. In this case, these are arranged equidistantly in the circumferential direction. The rotor 20 is again arranged in a through-opening formed by the stator; in this embodiment, this rotor is also twelve-pole and thus provides six north poles N and six south poles S in the circumferential direction, which are arranged alternately. Here, too, it is provided that the magnetic flux provided by the rotor 20 is provided by permanent magnets, which are arranged, for example, in the region of the outer circumference of the rotor 20.

[0085] Here, too, each of the stator teeth 11 is equipped with a winding section 122 of one of the three tooth windings. Each of the three tooth windings again has a respective first electrical conductor and a respective second electrical conductor (shown in Figure 4 by different line thicknesses for illustrative purposes only), which are wound bifilarly onto the respective stator teeth 11. This electrical machine 2' is also designed to be supplied with a three-phase alternating electrical voltage, with each of the phases again being designated U, V, W. Figure 5 shows an electrical connection of the tooth windings 12A-12C and the inverter units 130A-130F of the inverter 13 of the electrical machine 2 according to Figure 1.

[0086] The (in this case three) first electrical conductors 120 of the tooth windings 12A-12C form a first winding system, and the (in this case three) second electrical conductors 121 of the tooth windings 12A-12C form a second winding system. The first winding system is connected to three inverter units 130A-130C. The first electrical conductors 120 are each connected by an end section WA2, VA2, UA2 to one of the inverter units 130A-130C. The respective other end sections WA1, VA1, UA1 of the first electrical conductors 120 are electrically connected to one another at a first star point 123. The second winding system is connected to three inverter units 130D-130F. The second electrical conductors 121 are each connected by an end section WB1, VB1, UB1 to one of the inverter units 130D-130F.The respective other end sections WB2, VB2, UB2 of the second electrical conductors 121 are electrically connected to one another at a second star point 124.

[0087] The inverter 13 thus comprises six inverter units 130A-130F, two each for each of the three phases U, V, and W, and of these two, one each for the first winding system and one for the second winding system. As already described, each inverter unit 130A-130D has a half-bridge circuit. An optional capacitor supplements the existing circuit with a low-pass filter.

[0088] A (in this case, the same) DC voltage (marked HV+ and HV-) is applied to the inverter units 130A-130D of inverter 13. For example, the DC voltage is 25 V or more, 100 V or more, or 800 to 3000 V.

[0089] Furthermore, the total of six winding sections 122 for the six stator teeth 11 are shown, wherein each winding of the first and second electrical conductors 120, 121 is only shown schematically. First, the tooth winding 12A for a first phase W will be considered. The tooth winding 12A comprises a first electrical conductor 120 and a second electrical conductor 121. Both electrical conductors 120, 121 extend over the winding sections 122 on the same (two) stator teeth 11, but are insulated from one another. Both electrical conductors 120, 121 have the two end sections WA1, WA2, WB1, WB2 already mentioned. Both electrical conductors 120, 121 are free of branches between their end sections WA1, WA2, WB1, WB2. The electrical conductors 120, 121 each establish an electrical connection between the respective two end sections WA1, WA2, WB1, WB2.The winding sections 122 of the tooth winding 12A lie between the end sections WA1, WA2, WB1, WB2 of the electrical conductors 120, 121.

[0090] The first electrical conductor 120 is electrically connected with one end section WA2 to a first inverter unit 130A of the inverter 13 and is electrically connected with the other end section WA1 to the first star point 123. The second electrical conductor 121 is electrically connected with one end section WB1 to a fourth inverter unit 130D of the inverter 13 and is electrically connected with the other end section WB2 to a second star point 124.

[0091] The end sections of the first electrical conductor 120 of the tooth winding 12B for a second phase V are designated VA1 and VA2. The first electrical conductor 120 is electrically connected to the inverter 13, specifically to a second inverter unit 130B thereof, with one end section VA2, and is electrically connected to the first star point 123 with the other end section VA1.

[0092] Accordingly, the end sections of the second electrical conductor 121 of the tooth winding 12B for the second phase V are designated VB1 and VB2. The second electrical conductor 121 is electrically connected with one end section VB1 to the inverter 13, specifically to a fifth inverter unit 130E thereof, and is electrically connected with the other end section VB2 to the second star point 124. The end sections of the first electrical conductor 120 of the tooth winding 12C for a third phase U are designated UA1 and UA2. The first electrical conductor 120 is electrically connected with one end section UA2 to the inverter 13, specifically to a third inverter unit 130C thereof, and is electrically connected with the other end section UA1 to the first star point 123.

[0093] Accordingly, the end sections of the second electrical conductor 121 of the tooth winding 12C for the third phase U are designated UB1 and UB2. The second electrical conductor 121 is electrically connected with one end section UB1 to the inverter 13, specifically to a sixth inverter unit 130F thereof, and with the other end section UB2 to the second star point 124.

[0094] The arrangement 1 further comprises a protective device, described in more detail below, in the form of a differential protection device. The differential protection device comprises a plurality of sensors for detecting an electrical quantity, in the form of current sensors 140. Each of the current sensors 140 is arranged on the first or second electrical conductor 120, 121 and measures the current intensity of the current flowing therein. In general, a current sensor 140 is arranged at at least two points on the first electrical conductor 120 and at two points on the second electrical conductor 121 of at least one (or each) of the tooth windings 12A-12C. In the example shown, four current sensors are provided per tooth winding 12A-12C. The current sensors 140 each comprise a Hall sensor. Optionally, the Hall sensor is coupled to a ferromagnetic flux concentrator, which, for example,encompasses the respective electrical liner 120, 121 and optionally comprises a V-shaped tapered section, at the pointed end of which the Hall sensor is arranged.

[0095] For each of the tooth windings 12A-12C, a current sensor 140 is arranged at a first location X1 on the (first) electrical conductor 120. This (first) location X1 is located, with respect to the electrical path, between the end section WA2 and the winding section 122 closest to this end section WA2 along the electrical path of the first electrical conductor 120. Another current sensor 140 is arranged at a (second) location X2 on the first electrical conductor 120. This (second) location X2 is located, with respect to the electrical path, between the end section WA1 and the winding section 122 closest to this end section WA1 along the electrical path of the first electrical conductor 120. Another current sensor 140 is arranged at a (third) location X3 on the second electrical conductor 121.This (third) location X3 is located, with respect to the electrical path, between the end section WB2 and the winding section 122 closest to this end section WB2 along the electrical path of the second electrical conductor 121. Another current sensor 140 is arranged at a (fourth) location X4 on the second electrical conductor 121. This (fourth) location X4 is located, with respect to the electrical path, between the end section WB1 and the winding section 122 closest to this end section WB1 along the electrical path of the second electrical conductor 121.

[0096] Thus, with respect to the electrical paths, the winding sections 122 are each located between the current sensors 140. By determining a difference (in particular in comparison with a threshold value) between the current intensities detected by the current sensors 140 at the first location X1 and the second location X2 and / or correspondingly a difference between the third location X3 and the fourth location X4, the control unit 131 can detect a winding short circuit by means of the differential protection device and initiate a countermeasure.

[0097] The control unit 131 is configured to detect a first difference in the current intensities (more generally: the electrical quantity) at the two locations X1, X2 of the first electrical conductor 120 and a second difference in the electrical quantity at the two locations X3, X4 of the second electrical conductor 121 and to output an output signal based on a deviation between the first difference and the second difference.

[0098] In the second and third tooth windings 12B, 12C, the current sensors 140 are arranged corresponding to the first tooth winding 12A.

[0099] Figure 6 shows essentially the same circuitry as Figure 5, but with more winding sections 122 illustrated. It can be seen that the tooth windings 12A-12C can have a smaller or larger number of winding sections 122 depending on the application, e.g., a total of six (see in particular Figures 2 and 5), twelve (see in particular Figure 4), or 18.

[0100] While according to Figures 5 and 6 the tooth windings 12A-12C are arranged between the inverter units 130A-130F, it is pointed out that this arrangement is only exemplary.

[0101] Furthermore, it can be seen that in Figures 5 and 6, the end portions of the first and second conductors 120, 121 of each of the tooth windings 12A-12C connected to the inverter units 130A-130F face away from each other with respect to the common winding portions 122.

[0102] Figure 7 shows a general structure of a differential protection device, such as may be provided in the stator 21. In general, the differential protection device compares two currents measured at different locations.

[0103] A component to be monitored is represented by a block. In this case, this is the portion of the first electrical conductor 120 or the second electrical conductor 121 of one of the tooth windings 12A-12C between its respective end sections. The current sensors 140 are designed here as (optional) measuring coils with one or more turns, which are arranged on the corresponding first / second electrical conductor, so that the current in the electrical conductor induces a current in the measuring coils. The measuring coils (or generally the current sensors 140) are connected in series in a closed circuit. If the current intensities of the currents induced in both current sensors 140 are the same, then no current flows via a cross connection between one and the other electrical connection of the current sensors 140.However, if a portion of the current flows through the monitored electrical conductor into the other bifilar electrical conductor, a difference results which leads to a current in the cross connection. This cross current is monitored by the differential protection device and, for example, compared with a threshold value. Based on this, a countermeasure can be initiated, for example an optional switch (e.g. in the form of a relay) in the electrical conductor can be opened. Furthermore, as a countermeasure, a current introduced into the monitored electrical conductor 120, 121 can be changed, for example reduced or switched off, by changing the control of the transistors of at least the inverter unit 130A-130F connected to it based on the detection of a differential current. The transistors are controlled by means of signals, in this case by means of pulse duration modulated signals, which can also be referred to as PWM signals (pulse width modulation) for short.The PWM signals alternate between two discrete values, e.g. “on” and “off”, which open or close the corresponding transistor.

[0104] Figure 8 shows an example of such PWM signals, where X stands for the respective phase U, V, W. The PWM signals for the individual phases II, V, W, for example, are identical, only shifted in time.

[0105] Furthermore, an inverted PWMX' signal is provided for each PWMX signal, which assumes a different discrete value with respect to the PWMX signal over time.

[0106] As illustrated, for example, in Figures 5 and 6, for each of the tooth windings 12A-12C, the inverted PWM signal PWMW, PWMV', PWMLT is applied to the transistor of the inverter unit 130A, 130B, 130C of the first electrical conductor 120 connected to the positive pole HV+ of the DC voltage. In contrast, the PWM signal PWMW, PWMV, PWMU is applied to the transistor of the inverter unit 130A, 130B, 130C of the first electrical conductor 120 connected to the negative pole HV- of the DC voltage.

[0107] For the second electrical conductors 121, the PWM signals are applied in reverse. The PWM signal PWMW, PWMV, PWMU is applied to the transistor of the inverter unit 130D, 130E, 130F of the second electrical conductor 121 connected to the positive pole HV+ of the DC voltage. In contrast, the reversed PWM signal PWMW, PWMV', PWMU' is applied to the transistor of the inverter unit 130D, 130E, 130F of the second electrical conductor 121 connected to the negative pole HV- of the DC voltage. It is therefore evident that the inverter units 130A-130C of the first electrical conductor 120 are supplied with the same PWM signals as the inverter units 130D-130F of the second electrical conductor 121.

[0108] Figure 9 illustrates the generation of the PWM signals and the reverse PWM signals. The inverter control unit 131 generates signals for the three phases U, V, and W, referred to here as pwmu, pwmv, and pwmw. These are each provided to a power electronics driver 132A-132C, which, based on these signals, generates the PWM signals and the reverse PWM signals for the corresponding phase U, V, and W. The power electronics drivers 132A-132C are connected (e.g., electrically) to the inverter units 130A-130F of the respective phases U, V, and W.

[0109] Figure 10 shows the protective device in the form of the differential protection device 14A of arrangement 1 according to Figure 1. The differential protection device 14A comprises the (12 in total) current sensors 140. The other components shown in Figure 5 are not shown again here for the sake of clarity. Furthermore, the differential protection device 14A comprises a plurality of comparators 141, six in this case. Two current sensors 140 are connected to each comparator 141, which is represented here in a simplified manner by a line. For example, the current sensors 140 are each electrically connected to the respective comparator 141. The respective comparator 141 is connected to the current sensors 140 in such a way that it can detect the current signals provided thereby, which are indicative of the current strength in the corresponding electrical conductor 120, 121.The comparator 141 compares the current signals provided by the two current sensors 140 and provides the comparison result as a differential signal to the control unit 131. If a predetermined condition is met, e.g., if a differential signal exceeds or falls below a threshold value, the control unit 131 detects an error.

[0110] As long as (within the measurement accuracy) the following applies to the currents: IUA1 = IUA2; IUB1 = IUB2; IVA1 = IVA2; IVB1 = IVB2; IWA1 = IWA2; and IWB1 = IWB2, no error is present. By detecting a current IUA1 (at point X2) that is not equal to a current IUA2 (point X1) and / or a current IUB1 (point X4) that is not equal to a current IUB2 (point X3) (or accordingly for one of the other phases V, W), the control unit 131 detects a winding short circuit. If this applies to two phases simultaneously, the control unit 131 (optionally) detects a short circuit between two phases.

[0111] If a fault is detected, control unit 131 optionally switches off all PWM signals (e.g., to zero). Optionally, the positive and / or negative poles HV+, HV- of DC voltage source 3 are disconnected from inverter units 130A-130F.

[0112] In the event of a short circuit between winding sections of the same phase, the control unit 131 optionally causes a three-phase short circuit.

[0113] Thus, the control unit 131 can detect whether (certain) first and second electrical conductors 120, 121 have a turn-to-turn short circuit. In this case, the control unit 131 provides, for example, appropriately modified PWM signals and reversed PWM signals.

[0114] The signals from the current sensors 140 at the first location X1 and at the second location X2 are connected to a comparator 141 (more generally, they are compared with each other). Alternatively or additionally (particularly for redundancy), the signals from the current sensors 140 at the third location X3 and at the fourth location X4 are connected to another comparator 141 (more generally, they are compared with each other). The comparison between one comparator 141 and the other comparator 141 can also be performed by an additional comparator.

[0115] The control unit 131 has an output 133 at which the control unit 131 outputs the output signal.

[0116] The control unit 131 is configured, for example, to output an output signal indicating a line fault (specifically, a winding short circuit) if the first difference and the second difference (in particular, the respective amount) are greater than a predetermined difference threshold and, at the same time, the deviation is smaller than a predetermined deviation threshold. The difference threshold is, for example, 5% of the nominal current value. For example, the control unit detects:

[0117] IUA1 - IUA2 = IUA1 -2 and

[0118] IUB1 - IUB2 = IUB1 -2,

[0119] IWA1 - IWA2 = IWA1 -2 and

[0120] IWB1 - IWB2 = IWB1 -2, and

[0121] IVA1 - IVA2 = IVA1 -2 and

[0122] IVB1 - IVB2 = IVB1 -2.

[0123] If there is no error, the values ​​IUA1 -2, IUB1 -2, IWA1 -2, IWB1 -2, IVA1 -2 and IVB1 -2 are all essentially equal to 0.

[0124] In the event of a turn-to-turn short circuit, the values ​​of ILIA1-2 and ILIB1-2 (or IWA1-2 and IWB1-2 or IVA1-2 and IVB1-2) each have the same values, different from 0. Small or short differences, as well as short peak-shaped differences, can result from measurement inaccuracies or noise. To filter this out, the control unit 131 is configured to only output the output signal if the first difference and / or the second difference is greater than the specified difference threshold over a specified period of time. Alternatively or additionally, the control unit 131 is configured to record the first difference and / or the second difference as an average value (e.g., as a root mean square or by smoothing or filtering) over a moving time window of a specified length.

[0125] In the case of a defective current sensor 140, however, the values ​​of IUA1-2 and IUB1-2 (or IWA1-2 and IWB1-2 or IVA1-2 and IVB1-2) may differ from one another. For example, IUA1-2 is equal to 0 and IUB1-2 is not equal to 0. The control unit 131 is therefore designed to determine a deviation of the first and the second difference (e.g., the values ​​of IUA1-2 and IUB1-2). Since these deviations can also be caused by measurement inaccuracies or noise (or also by offsets, nonlinearities, or temperature dependencies), the control unit 131 is designed to output an output signal indicating a sensor error if the deviation is greater than a predetermined deviation threshold. Alternatively or additionally, the control unit 131 is designed to output the output signal indicating a sensor error only if the deviation is greater than the predetermined deviation threshold over a predetermined period of time.Alternatively or additionally, the control unit 131 is configured to record deviation as an average value over a moving time window of predetermined length.

[0126] In the event of a sensor error, the control unit 131 can be configured to deactivate current monitoring. The output signal can be displayed to a user, e.g., a pilot.

[0127] The control unit 131 can be configured to perform a spectral analysis of the detected electrical variables. For example, instead of a threshold value of the raw signal, or in addition to that, the control unit 131 is configured to analyze predetermined frequency ranges, particularly those in which the signal is more unambiguous. For this purpose, a digital or analog bandpass filter can be used, for example.

[0128] Optionally, the control unit 131 also monitors the inverter units. Furthermore, the control unit 131 can monitor the total current flowing through the three phases. If this value deviates from 0, the control unit 131 can output an error.

[0129] Figure 10 also shows a method for monitoring the electrical machine 2; 2', which comprises:

[0130] - applying electric current to a plurality of tooth windings 12A-12C, each of which has a first electrical conductor 120 and a second electrical conductor 121, which are wound at least on a winding section 122 along a winding axis A around the same one of a plurality of teeth 11 of the electrical machine 2; 2' fixed to the body 10 and alternate in the direction of the winding axis A;

[0131] - detecting an electrical quantity with each of a plurality of sensors 140 arranged at at least two locations X1, X2, X5, X6 of the first electrical conductor 120 and two locations X3, X4, X7, X8 of the second electrical conductor 121 of at least one of the tooth windings 12A-12C;

[0132] - detecting, by means of the control unit 131, a first difference in the electrical quantity at the two locations X1, X2, X5, X6 of the first electrical conductor 120 and a second difference in the electrical quantity at the two locations X3, X4, X7, X8 of the second electrical conductor 121 and determining a deviation between the first difference and the second difference; and

[0133] - Outputting, by means of the control unit 131, an output signal based on the deviation at the output 133.

[0134] Figure 11 shows a differential protection device 14B which can be provided in arrangement 1 and is connected, for example, to the circuit according to Figure 5 or 6. As in Figure 10, the current sensors 140 are connected to the comparators 141. These, however, provide their differential signals to an analog multiplexer 142A. The multiplexer 142A provides the differential signal of the individual comparators at its output, for example, in chronological sequence (with a fixed frequency). This output is connected to an analog-to-digital converter, ADC 143. The ADC 143 converts the analog signals from the comparators into digital signals. These digital signals are output to the control unit 131. The control unit 131 can perform the comparison with the described threshold values ​​and output a "0", a "1", or a "2" accordingly at the output. A “1” then indicates, for example, a line fault, a “2” a sensor fault and a “0” an error-free state.Alternatively, it is possible to compare the outputs of the comparators 141 with another comparator and to connect the output of this comparator to the analog multiplexer (e.g. multiplexer 142A).

[0135] Optionally, the multiplexer 142A, the ADC 143, and / or the control unit 131 are combined into a microprocessor or SoC (system on a chip), e.g., an 8-bit flash microcontroller. The control unit 131 includes, for example, a vector control (field-oriented control, FOC).

[0136] Figure 12 shows a differential protection device 14C that can be provided in arrangement 1 and is connected, for example, to the circuit according to Figure 5 or 6. According to Figure 12, the current sensors are each connected to one of several (here 12) ADCs 143. The outputs of the ADCs 143 are connected to a digital multiplexer 142B, and its output is connected to the control unit 131.

[0137] Figure 13 shows essentially the same structure of the tooth windings 12A-12C and their connection to the inverter 13 as Figure 6. In contrast, however, the sections of the electrical conductors 120, 121 between the end sections and the winding sections 122 are laid such that sections on either side of the winding sections 122 (with respect to the electrical path of the respective electrical conductors 120, 121) run adjacent to one another at one point (in particular, antiparallel with respect to the direction of current flow), e.g., they abut one another. This makes it possible to use only one current sensor 140 per electrical conductor 120, 121. In the present case, therefore, six current sensors 140 are sufficient to monitor all six electrical conductors 120, 121 of phases U, V, W.

[0138] A current through the first electrical conductor 120 at a (first) point X5 of the first electrical conductor 120 (of each phase U, V, W) induces a current in a current sensor 140. A current through the first electrical conductor 120 at a (second) point X6 of the first electrical conductor 120 flows antiparallel to the other (first) point X5 and therefore induces a current in the same current sensor 140 with the opposite sign. If the current intensities at the two points X5, X6 are equal, the effectively induced current is zero. Thus, the current sensor 140 is arranged to measure an effective differential current through the first conductor 120 at points X5, X6 of the first electrical conductor 120, which are electrically connected to one another via the winding section 122.

[0139] Furthermore, a current through the second electrical conductor 121 at a (third) point X7 of the second electrical conductor 121 (of each phase II, V, W) induces a current in another current sensor 140. A current through the second electrical conductor 121 at a (fourth) point X8 of the second electrical conductor 121 flows antiparallel to the other (third) point X7 and therefore induces a current in the same current sensor 140 with the opposite sign. If the currents at the two points X7, X8 are equal, the effectively induced current is zero. Thus, the current sensor 140 for measuring an effective differential current through the second electrical conductor 121 is arranged at points X7, X8 of the second electrical conductor 121, which are electrically connected to one another via the winding section 122.

[0140] Figure 14 shows the corresponding differential protection device 14D, which can be provided in arrangement 1 and is connected to the circuit according to Figure 13. The differential protection device 14D corresponds to the differential protection device 14B according to Figure 12, whereby no comparators are necessary due to the current sensors 140 measuring the effective differential current.

[0141] Figure 15 shows a differential protection device 14E, which can be provided in arrangement 1 and can alternatively be connected to the circuit according to Figure 13. The differential protection device 14E corresponds to the differential protection device 14C according to Figure 13, whereby only six ADCs 143 are required due to the current sensors 140 measuring the effective differential current.

[0142] It should be noted in general that the control unit 131 can initiate countermeasures, but alternatively it can also be provided that the error is first displayed to a user who can then activate one of the described countermeasures via an input means.

[0143] It should also be noted that the current sensors 140 adjacent to the inverter units 130A-130D can optionally be integrated into the respective inverter unit 130A-130D, e.g., arranged in a housing of the inverter unit 130A-130D. Figure 16 shows the same structure of the tooth windings 12A-12C and their connection to the inverter 13 as Figure 13. Current sensors 140 are arranged both according to Figure 6 and sensors according to Figure 13. The control unit 131 can thus detect first and second differences according to Figure 6 and Figure 13 and compare them with one another. For example, the control unit 131 determines a first deviation using the sensors arranged according to Figure 6 and a second deviation using the sensors arranged according to Figure 13. If the two deviations are different from one another, the control unit 131 detects a sensor error and outputs a corresponding output signal.

[0144] Alternatively or additionally, the voltage can be measured at star points 123 and 124. These voltages can be compared with one or more comparators 141, e.g., each with respect to a ground potential or another reference potential, as illustrated in Figure 17. The comparison result of comparator 141 can be output to control unit 131. Alternatively or additionally, the voltage between the two star points 123, 124 can be measured using a voltage sensor 145. This voltage can be output to control unit 131, as illustrated in Figure 18.

[0145] Figure 19 shows an aircraft 4 in the form of an electrically powered airplane. The aircraft 4 comprises a propeller 40, which is driven by the above-described electric machine 2 according to Figure 2 (alternatively by the electric machine 2' according to Figure 4).

[0146] The aircraft 4 further comprises an energy source 3 in the form of an electric battery, fuel cell, and / or generator. The electric machine 2 is supplied with energy by the energy source 3, which is electrically connected to the inverter 13.

[0147] Figure 20 shows a circuit similar to that described above with reference to Figure 5. The circuit comprises several, namely three, tooth windings 12A-12C, each comprising a first electrical conductor 120 and a second electrical conductor 121. The first electrical conductor 120 and the second electrical conductor 121 of each tooth winding are wound along a winding axis A around (each) the same tooth 11 (as described above) at least on one winding section 122, here merely by way of example on each of two (series-connected) winding sections 122. The first and second electrical conductors 120, 121 alternate in the direction of the winding axis A.

[0148] The first electrical conductors 120 of the three tooth windings 12A-12C are electrically connected to each other at a first star point 123. The second electrical conductors 121 of the three tooth windings 12A-12C are electrically connected to each other at a second star point 124.

[0149] The inverter 13 comprises a first inverter arrangement 134A with three inverter units 130A-130C, one each for a phase U, V, W of the three-phase alternating voltage, and a second inverter arrangement 134B, with three further inverter units 130D-130F, also one each for a phase U, V, W of the three-phase alternating voltage.

[0150] The two inverter assemblies 134A, 134B each have an inverter unit 130A-130F for each phase U, V, W of the three-phase AC voltage. Each of the three first electrical conductors 120 of the tooth windings 12A-12C is electrically connected to a respective inverter unit 130A-130C of the first inverter assembly 134A, and each of the three second electrical conductors 121 of the tooth windings 12A-12C is electrically connected to a respective inverter unit 130D-130F of the second inverter assembly 134B.

[0151] The inverter arrangements 134A, 134B can be activated and deactivated independently of one another.

[0152] A sensor 140 for detecting measured values ​​of an electrical quantity of the respective electrical conductor 120, 121 is arranged on at least one of the electrical conductors 120, 121, here on each of the first and second electrical conductors 120, 121. The sensors 140 are each designed in the form of current sensors, which are designed to measure a current flowing through the respective electrical conductor 120, 121. The sensors 140 are each arranged in or between the respectively assigned inverter unit 130A-130F and the winding section 122 connected closest to the respective electrical conductor 120, 121 along the respective electrical conductor 120, 121. The sensors 140 are therefore each arranged on the driver side, i.e. the inverter side, not on the star point side. The sensors 140 may be arranged close to the winding section 122 or close to (or in) the respective inverter unit 130A-130F.Furthermore, the sensors 140 can be integrated into the respective inverter unit 130A-130F.

[0153] The arrangement 1 according to Figure 1 can comprise the circuit according to Figure 20.

[0154] The control unit 131 of the arrangement 1 is configured to receive the measured values ​​of the sensors 140 and, based on one or more of the measured values, to determine at least one value that is indicative of a sum of the electrical quantity of the first electrical conductor 120 and / or the second electrical conductor 121 (here: the current intensity through the respective electrical conductor 120, 121). Furthermore, the control unit 131 is configured to output an output signal based on the at least one value.

[0155] In this case, the control unit 131 records (e.g. periodically) the measured values ​​of the sensors 140. It then adds the measured values ​​of the current intensities of the three first conductors 120. Furthermore, the control unit 131 adds the measured values ​​of the current intensities of the three second conductors 120. The control unit 131 divides the two sums by three (optionally) and thus obtains the respective zero-sequence system current for the first electrical conductor 120 and for the second electrical conductor 121: I0 = 1 / 3 * (lu+lv+lw).

[0156] The control unit 131 then compares the two obtained zero-sequence system currents with a predefined threshold. If neither of the zero-sequence system currents exceeds the threshold, the control unit 131 assumes fault-free operation and optionally outputs a corresponding output signal. If one of the zero-sequence system currents exceeds the threshold and the other does not, the control unit 131 assumes a sensor fault or other measurement error. It outputs this with an output signal indicating a sensor fault. If, however, both zero-sequence system currents exceed the threshold, the control unit 131 assumes a short circuit and outputs this with an output signal indicating an insulation fault.

[0157] Instead of the zero-sequence system currents, the control unit 131 can also evaluate quantities proportional to them, e.g. directly the sums obtained as described above.

[0158] Measuring two zero-sequence system currents enables redundant and verified fault detection, as well as the detection of the fault type. If at least one of the zero-sequence system currents exceeds the threshold value, control unit 131 detects a fault. The use of the zero-sequence system components allows for particularly simple yet reliable fault detection.

[0159] The sensors 140 are, for example, current transformers.

[0160] It should be noted that the sensors 140 may be located inside the electric machine or may be located outside the electric machine.

[0161] Optionally, control unit 131 determines harmonic frequencies of the zero-sequence currents. Control unit 131 can detect a fault based on a change in the harmonic frequencies. An analog or digital bandpass filter can be applied to the measured values.

[0162] Figure 21 shows essentially the same circuit as Figure 20. However, while Figure 20 provides for the star points 123, 124 to be arranged on different (opposite) sides of the body 10, Figure 21 illustrates that the first star point 123 and the second star point 124 are arranged on the same side of the body 10. Such an arrangement can optionally also be provided in the other circuits described herein; alternatively, an arrangement on opposite sides is possible.

[0163] Figure 22 illustrates a circuit essentially constructed as illustrated in Figure 20, with the windings of the first electrical conductors 120 and the second electrical conductors 121 drawn spaced apart for illustrative purposes only. In arrangement 1, these, as in the circuits of Figures 20 and 21, are provided bifilarly on the teeth. Regarding the function and connection of the circuit, reference is made to the above explanations.

[0164] According to Figure 22, a sensor 140, again in the form of a current sensor, surrounds the three first electrical conductors 120. Another sensor 140 surrounds the three second electrical conductors 121.

[0165] Thus, the two current sensors 140 already measure the sum of the currents through the three first electrical conductors 120 and through the three second electrical conductors 121 on the hardware side. The control unit 131 can therefore directly compare the measured value (or a value calculated therefrom) from each of the two sensors 140 with a corresponding threshold value in order to detect an error condition, as described above.

[0166] Figure 23 shows a circuit as described above in connection with Figure 6, so reference is made to the above explanations to avoid repetition. The sensors 140 are arranged as explained above in connection with Figure 20. The sensors 140 are designed, for example, in the form of coils around the respective electrical conductors 120, 121.

[0167] According to Figure 23, it is provided that the sensors 140 of the first electrical conductors 120 are connected in series with one another. Furthermore, it is provided that the sensors 140 of the second electrical conductors 120 are connected in series with one another, but, as shown in Figure 23, with reversed polarity compared to the sensors of the first electrical conductors 120. In this way, the type of interconnection already determines the sum of the measured values.

[0168] Furthermore, it is provided that the two series circuits are electrically connected in series via a connecting line 147. A voltage sensor 145 measures the voltage difference at the two open conductor ends of the series circuit. In fault-free operation, the measured voltage difference is less than a predetermined threshold. If the measured value output by the voltage sensor 145 exceeds the threshold, the control unit 131 assumes an insulation fault.

[0169] Also according to Figures 21, 22 and 23, the sensors 140 are arranged on the driver side.

[0170] The sensors 140 described, for example, with reference to the various figures can each be designed in the form of a Rogowski coil 146, as shown by way of example in Figure 24. The Rogowski coil 146 surrounds the respective electrical conductor (here, merely by way of example, the first electrical conductor 120). The Rogowski coil 146 comprises a coil-shaped wound wire, with the turns of the coil extending around the conductor 120. A return conductor extends around the conductor 120 and back along the coil.

[0171] Figure 25 illustrates a method for monitoring an electrical machine 2; 2', comprising:

[0172] Step S1: Applying electrical current to a plurality of tooth windings 12A-12C, each of which has a first electrical conductor 120 and a second electrical conductor 121, which are wound at least on a winding section 122 along a winding axis A around the same one of a plurality of teeth 11 of the electrical machine 2; 2' fixed to a body 10 and thereby alternate in at least one direction, in particular in the direction of the winding axis A), by means of a first inverter arrangement 134A with inverter units 130A-130C and a second inverter arrangement 134B with further inverter units 130D-130F, wherein the inverter arrangements 134A, 134B each have an inverter unit 130A-130F for each phase U, V, W of a multi-phase electrical alternating voltage,wherein each of the first electrical conductors 120 of the tooth windings 12A-12C is electrically connected to an inverter unit 130A-130C of the first inverter arrangement 134A, and each of the second electrical conductors 121 of the tooth windings 12A-12C is electrically connected to an inverter unit 130D-130F of the second inverter arrangement 134B, and wherein the first electrical conductors 120 of the tooth windings 12A-12C are electrically connected to one another at a first star point 123, and the second electrical conductors 121 of the tooth windings 12A-12C are electrically connected to one another at a second star point 124.

[0173] Step S2: Detecting an electrical quantity of one or more of the first or second electrical conductors 120, 121 with each of one or more sensors 140.

[0174] Step S3: Receive, by means of a control unit 131, the measured values ​​of the sensor 140 or the sensors 140.

[0175] Step S4: Determine, by means of the control unit 131, based on one or more of the measured values, at least one value indicative of a sum of the electrical quantities of the first electrical conductors 120 and / or the second electrical conductors 121. For example, the value is equal to the sum of the current intensities.

[0176] Step S5: Outputting, by means of a control unit 131, an output signal based on the at least one value.

[0177] It is understood that the invention is not limited to the embodiments described above, and various modifications and improvements may be made without departing from the concepts described herein. Any of the features may be used separately or in combination with any other features, provided they are not mutually exclusive, and the disclosure extends to and encompasses all combinations and subcombinations of one or more features described herein. List of Reference Symbols

[0178] I Arrangement

[0179] 10 bodies

[0180] II tooth (column tooth)

[0181] 12A-12C winding (tooth winding)

[0182] 120 first electrical conductor

[0183] 121 second electrical conductor

[0184] 122 winding section

[0185] 123 first star point

[0186] 124 second star point

[0187] 13 inverters

[0188] 130A-130F inverter unit

[0189] 131 Unit (control unit)

[0190] 132A-132C power electronics drivers

[0191] 133 Exit

[0192] 134A, 134B Inverter arrangement

[0193] 14A-14E protective device (differential protection device)

[0194] 140 Sensor (current sensor)

[0195] 141 Comparator

[0196] 142A, 142B multiplexers

[0197] 143 analog-to-digital converters

[0198] 144 totalizers

[0199] 145 Voltage sensor

[0200] 146 Rogowski coil

[0201] 147 connecting line

[0202] 2; 2' electric machine

[0203] 20 Assembly (Runner)

[0204] 21 Assembly (stand)

[0205] 3 Energy source

[0206] 4 aircraft

[0207] 40 propellers

[0208] A winding axis

[0209] L Air gap N North Pole

[0210] S South Pole

[0211] U, V, W phase

[0212] X1-X8 position

Claims

Claims 1 . Arrangement (1 ) for an electrical machine (2; 2'), comprising: an assembly (21 ) with a body (10) and a plurality of windings (12A- 12C), each having a first electrical conductor (120) and a second electrical conductor (121 ), which are wound along a winding axis (A) at least on one winding section (122) and alternate in at least one direction, in particular in the direction of the winding axis (A); a plurality of sensors (140) arranged at least at two points (X1, X2, X5, X6) of the first electrical conductor (120) and two points (X3, X4, X7, X8) of the second electrical conductor (121 ) of at least one of the windings (12A- 12C), each to detect an electrical variable;and a unit (131) configured to detect a first difference in electrical quantity at the two locations (X1, X2, X5, X6) of the first electrical conductor (120) and a second difference in electrical quantity at the two locations (X3, X4, X7, X8) of the second electrical conductor (121) and to output an output signal based on a deviation between the first difference and the second difference; 2. Arrangement (1) according to claim 1, wherein the sensors (140) are designed in the form of current sensors for measuring a current intensity through the respective electrical conductor (120, 121).

3. Arrangement (1) according to claim 1 or 2, wherein the at least two locations (X1-X8) of the respective electrical conductor (120, 121) are electrically connected to one another via the respective winding section (122).

4. Arrangement (1) according to one of the preceding claims, wherein the unit (131) is arranged to output the output signal when the deviation is greater than a predetermined deviation threshold, the output signal indicating a sensor error.

5. Arrangement (1) according to one of the preceding claims, wherein the unit (131 ) is arranged to output an output signal indicating a line fault if: the amount of the first difference and / or the amount of the second difference is / are greater than a predetermined difference threshold and the deviation is less than a predetermined deviation threshold.

6. Arrangement (1 ) according to claim 5, wherein the unit (131 ) is arranged to output the output signal only if the amount of the first difference and / or the amount of the second difference is greater than the predetermined difference threshold value over a predetermined period of time.

7. Arrangement (1) according to one of the preceding claims, wherein the unit (131) is configured to detect the first difference and / or the second difference as an average value over a predetermined time window and / or to extract a predetermined frequency range from values ​​of the detected electrical quantity by means of filtering, in particular bandpass filtering.

8. Arrangement (1) according to one of the preceding claims, wherein: a sensor (140) is arranged at a location (X1) of the at least two locations (X1, X2) of the first electrical conductor (120), a further sensor (140) is arranged at a further location (X2) of the at least two locations (X1, X2) of the first electrical conductor (120), a further sensor (140) is arranged at a location (X3) of the at least two locations (X3, X4) of the second electrical conductor (121), and a further sensor (140) is arranged at a further location (X4) of the at least two locations (X3, X4) of the second electrical conductor (121).

9. Arrangement (1) according to one of the preceding claims, wherein: a sensor (140) for measuring a differential current of the first electrical conductor (120) is arranged at points (X5, X6) of the first electrical conductor (120) that are electrically connected to one another via the winding section (122), and a further sensor (140) for measuring a differential current of the second electrical conductor (121) is arranged at points (X5, X6) of the first electrical conductor (120) that are electrically connected to one another via the winding section (122). electrically interconnected points (X7, X8) of the second electrical conductor (121).

10. Arrangement (1) according to one of the preceding claims, further comprising an inverter (13) with a plurality of inverter units (130A-130F) for each electrical phase (II, V, W) of a multi-phase electrical alternating voltage, wherein each of the first and second electrical conductors (120, 121) of the windings (12A-12C) is electrically connected to the inverter (13).

11. Arrangement (1) according to one of the preceding claims, comprising exactly three or more windings (12A-12C) for each phase of a three- or multi-phase alternating current.

12. Arrangement (1) according to one of the preceding claims, wherein the first electrical conductors (120) and / or the second electrical conductors (121) of the windings (12A-12C) are electrically connected to one another at a star point (123, 124).

13. Arrangement (1) according to one of the preceding claims, wherein the first and second electrical conductors (120, 121) of each of the windings (12A-12C) are arranged bifilarly at least at the winding section (122).

14. Arrangement (1 ) according to one of the preceding claims, wherein each of the first electrical conductors (120) of the windings (12A-12C) extends around a plurality of teeth (11 ) of the body (10) respectively and each of the second electrical conductors (121 ) of the windings (12A-12C) extends around the same teeth (11 ) respectively.

15. Arrangement (1) for an electrical machine (2; 2'), in particular according to one of the preceding claims, comprising: an assembly (21) with a body (10) and a plurality of windings (12A-12C), each having a first electrical conductor (120) and a second electrical conductor (121), which are connected to at least one winding section (122) are wound along a winding axis (A) and alternate in at least one direction, in particular in the direction of the winding axis (A), wherein the first electrical conductors (120) of the Windings (12A-12C) are electrically connected to each other at a first star point (123) and the second electrical conductors (121) of the Windings (12A-12C) are electrically connected to one another at a second star point (124); a first inverter arrangement (134A) with inverter units (130A-130C) and a second inverter arrangement (134B) with further inverter units (130D-130F), wherein the Inverter arrangements (134A, 134B) each have an inverter unit (130A-130F) for each phase (U, V, W) of a multi-phase alternating electrical voltage, wherein each of the first electrical conductors (120) of the windings (12A-12C) is electrically connected to an inverter unit (130A-130C) of the first inverter arrangement (134A) and each of the second electrical conductors (121) of the windings (12A-12C) is electrically connected to an inverter unit (130D-130F) of the second inverter arrangement (134B); one or more sensors (140) for detecting measured values ​​of an electrical quantity of one or more of the first or second electrical conductors (120, 121);and a unit (131) which is configured to o detect the measured values ​​of the sensor (140) or the sensors (140), o determine at least one value indicative of a sum of the electrical quantity of the first electrical conductors (120) and / or the second electrical conductors (121) based on one or more of the measured values, and o output an output signal based on the at least one value; 16. Arrangement (1 ) according to claim 15, wherein the unit (131 ) is arranged to: o the value as a first zero-sequence system current of the first electrical conductors (120) and / or the value or a further value as a second zero-sequence current of the second electrical conductors (121).

17. Arrangement (1) according to claim 15 or 16, wherein the unit (131) is configured to: o detect a fault on one of the first conductors (120) when the first zero-sequence system current exceeds a predetermined threshold value, and o detect a fault on one of the second conductors (121) when the second zero-sequence system current exceeds a predetermined threshold value, wherein the output signal indicates a fault when the control unit (131) has detected a fault on one of the first conductors (120) and / or has detected a fault on one of the second conductors (121).

18. Arrangement (1 ) according to claim 17, wherein the unit (131 ) is arranged to: o detect the presence of a first type of fault when either a fault is present on one of the first conductors (120) or a fault is present on one of the second conductors (121 ), and o detect the presence of a second type of fault when a fault is present on one of the first conductors (120) and a fault is present on one of the second conductors (121 ).

19. The arrangement (1) according to claim 18, wherein the output signal indicates a fault when the unit (131) detects the first fault type and indicates an insulation fault when the unit (131) detects the second fault type.

20. Arrangement (1) according to one of claims 15 to 19, wherein one of the sensors (140) is arranged on each of the first and second electrical conductors (120, 121), wherein the sensors (140) are each arranged between the respective inverter unit (130A-130F) and the respective next winding section (122) connected thereto.

21. Arrangement (1) according to claim 20, wherein the sensors (140) of the first electrical conductors (120) are connected in series and the sensors (140) of the second electrical conductors (121) are connected in series, the two series being electrically connected to one another at one end with reversed polarity and being connected to a voltage sensor (145) at the other end.

22. Arrangement (1) according to one of claims 15 to 21, wherein one of the sensors (140) encompasses all of the first electrical conductors (120) and one of the sensors (140) encompasses all of the second electrical conductors (121).

23. Arrangement (1) according to one of claims 15 to 22, wherein the first star point (123) and the second star point (124) are arranged on the same side of the body (10).

24. Arrangement (1) according to one of the preceding claims, wherein the sensor(s) (140) are designed in the form of current sensors for measuring a current intensity through the respective electrical conductor (120, 121), wherein the current sensors each comprise a Rogowski coil (146).

25. Arrangement (1) according to one of the preceding claims, wherein the unit (131) is configured to determine at least one harmonic of the value over time and to output the output signal based thereon, in particular to output the output signal based on a change in the at least one harmonic.

26. Electrical machine (2; 2') comprising the arrangement (1) according to one of the preceding claims and a further assembly (20), wherein the assembly (21) and the further assembly (20) are rotatable relative to one another.

27. Electrical machine (2; 2') according to claim 26, wherein the assembly (21) is designed as a stator and the further assembly (20) as a rotor.

28. Aircraft (4) comprising the electric machine (2; 2') according to one of claims 26 or 27.

29. A method for monitoring an electrical machine (2; 2'), comprising: Applying electrical current to a plurality of windings (12A-12C), each of which has a first electrical conductor (120) and a second electrical conductor (121), which are wound along a winding axis (A) at least on one winding section (122) and alternate in at least one direction, in particular in the direction of the winding axis (A); Detecting an electrical quantity with each of a plurality of sensors (140) arranged at least at two locations (X1, X2, X5, X6) of the first electrical conductor (120) and two locations (X3, X4, X7, X8) of the second electrical conductor (121) of at least one of the windings (12A-12C); Detecting, by means of a unit (131), a first difference in the electrical quantity at the two locations (X1, X2, X5, X6) of the first electrical conductor (120) and a second difference in the electrical quantity at the two locations (X3, X4, X7, X8) of the second electrical conductor (121) and determining a deviation between the first difference and the second difference; and outputting, by means of the unit (131), an output signal based on the deviation.

30. A method for monitoring an electrical machine (2; 2'), comprising: Applying electrical current to a plurality of windings (12A-12C), each having a first electrical conductor (120) and a second electrical conductor (121), which are wound at least on one winding section (122) along a winding axis (A) and thereby alternate in at least one direction, in particular in the direction of the winding axis (A), by means of a first inverter arrangement (134A) with inverter units (130A-130C) and a second inverter arrangement (134B) with further inverter units (130D-130F), wherein the inverter arrangements (134A, 134B) each have an inverter unit (130A-130F) for each phase (U, V, W) of a multi-phase electrical alternating voltage, wherein each of the first electrical conductors (120) of the windings (12A-12C) is electrically connected to an inverter unit (130A-130C) of the first inverter arrangement (134A) and each of the second electrical conductors (121) of the windings (12A-12C) is electrically connected to an inverter unit (130D-130F) of the second inverter arrangement (134B), and wherein the first electrical conductors (120) of the windings (12A-12C) are electrically connected to one another at a first star point (123) and the second electrical conductors (121) of the windings (12A-12C) are electrically connected to one another at a second star point (124); Detecting an electrical quantity of one or more of the first or second electrical conductors (120, 121) with each of one or more sensors (140); Receiving, by means of a unit (131), the measured values ​​of the sensor (140) or sensors (140); Determining, by means of the unit (131), based on one or more of the measured values, at least one value indicative of a sum of the electrical quantity of the first electrical conductors (120) and / or the second electrical conductors (121); and Outputting, by means of a unit (131), an output signal based on the at least one value.

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