Electric machine comprising a device for correcting a precession motion, aircraft turbomachine and associated methods

Abstract

An electric machine (1), particularly for an aircraft turbomachine (T), comprising a stator (2) having at least three power channels (C1-C4) and a rotor (3) configured to interact magnetically with the power channels (C1-C4), a control device (4) configured to determine a control parameter for each power channel (C1-C4) based on a control command (Com), and a correction device (5) configured to correct a precession motion of the rotor (3) relative to the stator (2), the correction device (5) being configured to determine the control command (Com) of the control device (4) from a setpoint command (Com_cons) and a precession level (NP), the control command (Com) being configured to generate an overall magnetic force (FG) opposing the precession motion (P+) of the rotor (3) so as to dampen it. Abstract figure: Figure 4

Description

Title of the invention: Electric machine comprising a device for correcting a precession movement, aircraft turbomachine and associated method Technical field

[0001] The present invention relates to the field of electrical machines, in particular, on board a turbomachine of an aircraft. The invention is particularly advantageous for an electrical machine driven in rotation by a propulsion shaft of an aircraft turbomachine to generate electrical energy. The invention also applies to an electrical machine used in engine operation.

[0002] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies both to new types of aircraft and those in circulation requiring the implementation of technological solutions in order to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to make a contribution to the fight against climate change.

[0003] Technological research efforts have already made it possible to significantly improve the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental consequences with the aim of improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work focuses both on new generations of aircraft engines and the development of electrical technologies to provide propulsion.

[0006] It is known in the prior art to mount an electric machine on a propulsion shaft of an aircraft turbomachine, for example, a fan shaft. The electric machine is configured to operate in a generator mode in order to draw mechanical power from the propulsion shaft so as to generate electrical power. The electric machine is also configured to operate in a motor mode in order to provide mechanical power to the propulsion shaft by drawing electrical power, for example, from an electric battery.

[0007] With reference to [Fig.l], there is shown schematically an electric machine 101 comprising a stator 102 fixedly mounted in a turbomachine and a rotor 103 secured to a propulsion shaft of the turbomachine. The rotor 103 is rotatably mounted relative to the stator 102. In this example, the rotor 103 rotates in the clockwise direction R+ relative to an electric machine axis X. In a known manner, the stator 102 comprises power channels C1-C4, distributed at the periphery of the stator 102, which interact magnetically with the rotor 103. Preferably, as power channel C1-C4 is in the form of a stator star.

[0008] Theoretically, when generating electrical power, each power channel C1-C4 generates a resistive magnetic force F1-F4 on the rotor 103 which opposes the rotation of the rotor 103.

[0009] In theory, the rotor 103 remains perfectly aligned with the electric machine axis X. In practice, a propulsion shaft of a turbomachine undergoes vibrations during its rotation around the electric machine axis X which induce a precessional movement on the rotor 103. Such a precessional movement can lead to performance losses or even premature wear of the turbomachine. With reference to [Fig. 2], a precessional movement of the rotor 103 is shown between time instants t1, t2, t3. In this example, the precessional movement P+ is in the clockwise direction but it goes without saying that it could also be in the counterclockwise direction.

[0010] To reduce the precessional movement, it is known in the prior art to provide a damping film, known to those skilled in the art under the designation "Squeeze Film Damper" or SFD. A damping film, positioned between the rotor 103 and the stator 102, makes it possible to dampen the vibrations passively, in particular, at the level of a bearing of the turbomachine. Thus, the damping film exerts a damping force which depends mainly on the following parameters: the eccentricity of the rotor 103, the rotational speed of the rotor 103, the characteristics of the damping film (viscosity, etc.) and the boundary conditions (power supply, sealing, etc.). In fact, the damping film is dimensioned so as to dampen as effectively as possible a predetermined vibration mode of the rotor 103.It is thus not very effective on the other vibration modes present in the operating range of the electric machine 101, which presents a drawback.

[0011] The invention aims to eliminate at least some of these drawbacks. PRESENTATION OF THE INVENTION

[0012] The invention relates to an electrical machine, in particular for an aircraft turbomachine, comprising: • A stator comprising at least three power channels and a rotor configured to magnetically interact with the power channels, • The electrical machine being configured, on the one hand, to operate in a generator mode in order to draw mechanical power from the rotor to generate electrical power and to operate, on the other hand, in a motor mode in order to consume electrical power to generate mechanical power and drive the rotor, • A control device configured to determine a control parameter for each power channel as a function of a control command, each control parameter defining the currents flowing in a power channel, each power channel generating a magnetic force on the rotor which is a function of its control parameter, all of the magnetic forces applied by the power channels on the rotor defining an overall magnetic force, and • A correction device configured to correct a precessional movement of the rotor relative to the stator, the correction device being configured to: • determine a level of precession of the rotor relative to the stator, • determine the control command of the control device from a setpoint command and the precession level, the control command being configured to generate an overall magnetic force opposing the precession movement of the rotor so as to dampen it.

[0013] Thanks to the invention, the correction device makes it possible to modify the control command of the power channels, used to generate a mechanical torque or generate electrical power, in order to correct a precession movement of the rotor. It is thus not necessary to use additional means to act on the rotor, which reduces the mass and the size. Furthermore, such a correction device allows dynamic damping that can respond to various vibrations. Its field of application is thus broader than a damping film that performs only for a few vibration modes. Advantageously, the damping intensity can be adjusted precisely.

[0014] Finally, the electric machine allows for damping while continuing to achieve its primary function of generating mechanical torque or generating electrical power, which is very advantageous.

[0015] Preferably, the correction device is configured, during operation in generator mode, to determine a control command consisting of injecting or modulating a current into only one power channel at a given instant, the other power channels being configured to collect currents at the given instant.

[0016] Thus, in the absence of current flowing in the power channel, a current is injected into the power channel to achieve damping. In the presence of a current flowing in the power channel, the current flowing in the power channel is modulated to achieve damping, for example, punctually increased.

[0017] Such a correction device makes it possible to achieve damping while continuing to perform its primary function of generating electrical power. The control of a single power channel is modified, which only slightly reduces the efficiency.

[0018] Preferably, the correction device is configured to determine a control command consisting of successively injecting or modulating a current into several power channels so as to generate an overall rotating magnetic force opposing the precession movement over time.

[0019] A rotating overall magnetic force makes it possible to effectively oppose a precessional movement while maximizing the efficiency of the electrical machine.

[0020] Preferably, the correction device is configured to determine a control command consisting of injecting or modulating a current according to a phase advance relative to the precession movement of the rotor. A phase advance correction makes it possible to apply an overall magnetic force which directly opposes the precession movement, the damping being optimal.

[0021] More preferably, the correction device is configured, during operation in motor mode, to determine a control command consisting of collecting or modulating a current in only one power channel at a given instant, the other power channels being configured to inject currents at the given instant. In general, the motor operation is deduced from the generator operation. In the presence of a current flowing in the power channel, the current flowing in the power channel is modulated to achieve damping, for example, punctually reduced.

[0022] According to one aspect of the invention, the stator comprises at least one pair of diametrically opposed power channels. This makes it possible to apply a magnetic force along an axis orthogonal to the alignment axis of the power channels of a pair. direction of the overall magnetic force is thus determined rigorously.

[0023] Preferably, the stator comprises at least four power channels spaced angularly by 90°. This makes it possible to adjust the magnetic force precisely in order to position the rotor relative to the stator. The damping is thus efficient.

[0024] The invention also relates to an aircraft turbomachine comprising at least one propulsion shaft and an electrical machine as presented previously, the rotor of which is securely connected to the propulsion shaft. Integration into an aircraft turbomachine is relevant given that a propulsion shaft is subjected to numerous vibration modes. Such an electrical machine makes it possible to ensure mechanical torque generation / electrical generation while damping the vibrations.

[0025] Preferably, the propulsion shaft is integral with a fan comprising a plurality of fan blades. The fan is mounted in a fan casing. Mounting an electrical machine on a fan shaft is advantageous because a precessional movement increases wear and presents discomfort to the passengers of the aircraft.

[0026] Preferably, the rotor is mounted at the free ends of the fan blades, the stator being mounted on the fan casing. Such integration makes it possible to correct a precession movement which is significant at the free ends of the fan blades given the bending forces applied to the fan shaft which amplify the precession movement. This also makes it possible to use several power channels to achieve progressive damping.

[0027] The invention relates to a method for monitoring an electrical machine as presented previously, a setpoint command being defined, the method comprising steps consisting of: • determine a level of precession of the rotor relative to the stator, • determine the control command of the control device from a setpoint command and the precession level, the control command generating an overall magnetic force opposing the precession movement of the rotor so as to dampen it.

[0028] Preferably, the step of determining the level of precession of the rotor is only implemented when the vibrations measured on the propulsion shaft exceed a predetermined threshold. This makes it possible to maximize the use of the electrical machine on its primary function (generator or motor).

[0029] Preferably, the monitoring method comprises steps consisting of: • Record the overall magnetic forces generated over time and • estimate a state of wear of the turbomachine from the magnetic forces global recorded over time.

[0030] Advantageously, by monitoring the evolution of the overall magnetic forces applied, the need for correction and, consequently, a state of wear of the turbomachine is estimated. If the overall magnetic force applied becomes too high, a maintenance step of the turbomachine must be carried out. PRESENTATION OF FIGURES

[0031] The invention will be better understood on reading the description which follows, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects.

[0032] [Fig.l] is a schematic representation of an electrical machine and the magnetic forces applied to the rotor.

[0033] [Fig.2] is a schematic representation of a precessional movement of a rotor of an electric machine.

[0034] [Fig. 3] is a schematic representation of an aircraft turbomachine equipped with an electric machine.

[0035] [Fig.4] is a schematic representation of an electrical machine according to one embodiment of the invention.

[0036] [Fig.5] is a representation of a plurality of control modules of a control device for controlling each power channel.

[0037] [Fig.6] is a schematic representation of a first control module of the control device receiving switching orders from a first switching member.

[0038] [Fig.7] is a schematic representation of the determination of switching orders by the first switching member.

[0039] [Fig.8] is a schematic representation of the electrical machine of [Fig.4] and the magnetic forces applied to the rotor in the absence of a precessional movement.

[0040] [Fig.9] is a schematic representation of the electric machine of [Fig.4] and the magnetic forces applied to the rotor having a precessional movement at a first instant.

[0041] [Fig. 10] is a schematic representation of the electric machine of [Fig.4] and the magnetic forces applied to the rotor having a precessional movement at a second instant.

[0042] [Fig. 11] is a schematic representation of the steps of a method for monitoring an electrical machine.

[0043] [Fig. 12] is another schematic representation of the electric machine of [Fig.4] and the magnetic forces applied to the rotor having a movement of precession at a first instant.

[0044] [Fig. 13] is a schematic representation of a turbomachine comprising an electric machine mounted on the periphery of a fan.

[0045] It should be noted that the figures set out the invention in detail to implement the invention, said figures can of course be used to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0046] The invention will be presented for an electrical machine for an aircraft turbomachine. Such an application is particularly advantageous given that an aircraft turbomachine is subject to vibrations. Nevertheless, the invention applies to any electrical machine, particularly in the industrial field.

[0047] In this example, with reference to [Fig. 3], there is shown an aircraft turbomachine T comprising at least one propulsion shaft A on which an electric machine 1 is mounted. Preferably, the propulsion shaft A is a fan shaft F, in particular, a low pressure shaft of a twin-body turbomachine T comprising a low pressure shaft A and a high pressure shaft 103.

[0048] In this example, [Fig. 3] also schematically shows a low pressure compressor 101, a high pressure compressor 102, a high pressure turbine 104 and a low pressure turbine 105. The low pressure propulsion shaft A connects the low pressure compressor 101 to the low pressure turbine 105. The high pressure shaft 103 connects the high pressure compressor 102 to the high pressure turbine 104.

[0049] Such a propulsion shaft A is likely to be subject to vibrations during its operation which can disturb the rotation of the fan F.

[0050] With reference to [Fig. 3], the electric machine 1 comprises a stator 2 mounted fixedly in the turbomachine T and a rotor 3 mounted integrally with the propulsion shaft A, the rotor 3 being mounted rotatably relative to the stator 2 along an electric machine axis X. In this example, the electric machine axis X merges with the axis of the propulsion shaft A. It goes without saying that this could be different.

[0051] With reference to [Fig. 4], the stator 2 comprises four power channels C1-C4. The stator 2 could comprise a different number of power channels, preferably a number greater than 3. Each power channel C1-C4 is preferably in the form of a winding in order to circulate a current which is injected by a control device 4 (presented subsequently) or collect a current which is generated by magnetic induction. The use of several power channels C1-C4 makes it possible to increase redundancy and limit the risk of critical failure. In this example, with reference to [Fig. 5], each power channel C1-C4 is in the form of an independent stator star generating alternating currents three-phase in generator operation and receiving three-phase alternating currents in motor operation.

[0052] In this embodiment, the stator 2 comprises four power channels C1-C4 angularly spaced by 90°. The presence of pairs of diametrically opposed power channels C1-C3, C2-C4 is advantageous as will be presented later in order to exert a controlled magnetic force on the rotor 3.

[0053] The rotor 3 comprises a plurality of magnetic elements, in particular magnets, in order to interact magnetically with the power channels C1-C4 of the stator 2, in particular, inductively.

[0054] The electrical machine 1 is configured, on the one hand, to operate in a generator mode in order to draw mechanical power from the rotor 3 (and therefore from the fan F) to generate electrical power. The electrical machine 1 is configured, on the other hand, to operate in a motor mode in order to consume electrical power to generate mechanical power and drive the rotor 3 and therefore the fan F.

[0055] Generally speaking, with reference to [Fig. 3], the electrical machine 1 comprises a control device 4 configured to collect, inject or modulate a current into each power channel C1-C4 according to a control command Com. In particular, as presented previously, the control device 4 makes it possible to define three-phase currents for each power channel C1-C4.

[0056] Subsequently, the three-phase currents controlled by the control device 4 at each power channel C1-C4 are designated “control parameter P1-P4”. Thus, each power channel C1-C4 can be controlled individually according to its control parameter P1-P4.

[0057] The control device 4 is connected to an electrical network of the aircraft, in particular, to an electrical distribution unit 6 in the form of a distribution bus having a distribution voltage VDC ([Fig.6]). The electrical distribution unit 6 is connected to electrical loads to be supplied and / or to electrical sources (batteries, etc.).

[0058] According to the invention, the electrical machine 1 further comprises a correction device 5 configured to correct a precession movement of the rotor 3 relative to the stator 2 by modifying the control command Com received by the control device 4. The different components of the invention will now be presented.

[0059] In this example, with reference to [Fig. 5], the control device 4 comprises several control modules 4-1, 4-2, 4-3, 4-4 and a plurality of switching members 40-1, 40-2, 40-3, 40-4 configured to respectively control the power channels C1-C4 from a plurality of elementary commands Com1, Com2, Com3, Com4 from the Com control command. In this example, the Com control command is presented in the form of a vector.

[0060] Preferably, each control module 4-1, 4-2, 4-3, 4-4 is in the form of an AC / DC converter, in particular an inverter, which connects a power channel C1-C4 to the electrical distribution unit 6. With reference to [Fig. 6], each control module 4-1, 4-2, 4-3, 4-4 comprises a plurality of switches, in particular transistors, which are configured to receive switching orders Q1-Q6 so as to modify the three-phase currents Ia, Ib, Ie supplied to a power channel C1-C4.

[0061] Each control module 4-1, 4-2, 4-3, 4-4 is associated with a switching member 40-1, 40-2, 40-3, 40-4 configured to convert an elementary control command Com1, Com2, Com3, Com4 into switching orders Q1-Q6.

[0062] A switching member 40-1, 40-2, 40-3, 40-4 determines the switching orders Q1-Q6 by generating pulse width modulation (PWM) signals by comparing a reference voltage Vref, corresponding to an elementary control command Coml, Com2, Com3, Com4, with a triangular reference voltage Vtri as illustrated in [Fig.7].

[0063] As illustrated in [Fig.5], each control module 4-1, 4-2, 4-3, 4-4 of the control device 4 determines, for its power channel C1-C4, a control parameter P1-P4. Thus, each power channel C1-C4 can be controlled individually. Unlike the prior art according to which all the power channels C1-C4 are used either to inject current or to collect current, the control device 4 allows a hybrid use in which some power channels C1-C4 are used to inject current while others are used to collect current (modulation of the current in the power channels).

[0064] In this example, with reference to [Fig.4], the control device 4 is electrically connected to an electrical distribution unit 6 in order to be able to inject current in motor mode and supply the electrical distribution unit 6 in generator mode.

[0065] As illustrated in [Fig.8], each power channel C1-C4 generates a magnetic force F1-F4 on the rotor 3 which is a function of its control parameter P1-P4 defined in the control command Com. For example, in generator mode, the magnetic force F1-F4 is a resistive force which opposes the rotation of the rotor 3. Conversely, in motor mode, the magnetic force F1-F4 is a force which accompanies the rotation of the rotor 3. Advantageously, the magnetic force F1-F4 depends on the control parameters P1-P4 of the control command Com. Thus, each magnetic force F1-F4 can be parameterized precisely and dynamically by updating the control command Com as will be presented later.

[0066] All the magnetic forces F1-F4 applied by the power channels C1-C4 to the rotor 3 define an overall magnetic force FG applied to the rotor 3. Conventionally, as illustrated in [Fig.8], the magnetic forces compensate each other so that the overall magnetic force FG is substantially zero. According to the invention, in the absence of precessional movement, the overall magnetic force FG is substantially zero.

[0067] With reference to [Fig.4], the electrical machine 1 comprises a correction device 5 making it possible to correct the precession movement by applying an overall force FG which is a function of the control command Com. By dynamically adapting the control command Com, the precession movement of the rotor 3 is dynamically corrected.

[0068] According to the invention, still with reference to [Fig. 4], the electrical machine 1 comprises a correction device 5 configured to correct a precession movement of the rotor 3 relative to the stator 2. The correction device 5 is configured to determine a precession level NP of the rotor 3 relative to the stator 2. By precession level NP, is meant in particular a direction of precession and a precession intensity, for example, a distance of separation of the rotor 3 relative to the electric machine axis X (eccentricity). Preferably, the precession level NP comprises the current position of the rotor 3 in its precession movement P+, that is to say, the precession position. This advantageously makes it possible to dynamically correct a precession movement P+ as a function of the precession position.Preferably, the correction device 5 comprises at least one sensor 51 for measuring the eccentricity (also called orbiting) and the direction of rotation. Preferably, the correction device 5 comprises at least two displacement measuring sensors 51 which are phase-shifted relative to each other to precisely measure the eccentricity and the direction of rotation. A phase shift of 90° is suitable, for example.

[0069] The correction device 5 is configured to determine a control command Com from a setpoint command Com_cons and the precession level NP. The control command Com is configured to generate an overall magnetic force FG opposing the precession movement of the rotor 3 so as to dampen it.

[0070] In other words, the correction device 5 makes it possible to adapt the setpoint command Com_cons so as to allow the setpoint to be partially achieved while correcting the precession movement of the rotor 3 so as to dampen it. The control command Com makes it possible to modulate the setpoint command Com_cons to obtain damping while allowing the electrical machine 1 to perform its primary function.

[0071] An example of implementation of a method for monitoring an electrical machine 1 will be presented with reference to FIGS. 8 to 11.

[0072] In this example, the electrical machine 1 operates in generator mode and its rotor 3 rotates clockwise R+. The control device 4 receives a setpoint command Com_cons which is provided by a computer (not shown) of the turbomachine T. This setpoint command Com_cons commands each power channel C1-C4 to collect currents (operation in generator mode).

[0073] In the absence of precessional movement, the control command Com is equal to the setpoint command Com_cons. With reference to [Fig.8], each power channel C1-C4 generates a resistive magnetic force F1-F4 on the rotor 3 which is a function of its control parameter P1-P4. In this example, the resistive magnetic forces F1-F4 are of the same value. This results in an overall magnetic force FG which is substantially zero. Thus, the rotor 3 is not moved magnetically.

[0074] During operation of the turbomachine T, the correction device 5 performs a step consisting of determining E1 the precession level NP of the rotor 3, in particular, by monitoring the eccentricity of the rotor 3 and the direction of precession via the sensors 51. In this example, with reference to FIGS. 9 and 10, due to the vibrations of the fan shaft A, the rotor 3 has a precession movement. In this example, the precession level NP corresponds to a clockwise precession (direct precession P+) with a degree of precession which corresponds to the separation of the rotor 3 from the electric machine axis X (eccentricity). Preferably, the step consisting of determining E1 the precession level NP of the rotor 3 is only implemented when the vibrations measured on the propulsion shaft A exceed a predetermined threshold. This makes it possible to avoid monitoring the precession level NP continuously.

[0075] With reference to [Fig. 11], if the precession level NP exceeds a predetermined threshold SI, the correction device 5 performs a step E2 consisting of determining a control command Com from the setpoint command Com_cons and the determined precession level NP. In the present case, the correction device 5 determines a control command Com to generate an overall magnetic force FG opposing the precession movement of the rotor 3 so as to damp it. In particular, an overall magnetic force FG is applied which opposes a clockwise precession with an amplitude which is a function of the eccentricity.

[0076] The control command Com can be determined in several ways in order to create an imbalance of the magnetic forces and generate a non-zero overall magnetic force FG.

[0077] Preferably, the correction device 5 is configured, during a func operation in generator mode, to inject a correction current into only one power channel C3 at a given time t, the other power channels C1, C2, C4 being configured to collect currents at the given time t. The power channels C1-C4 are used in a hybrid manner.

[0078] As an example, with reference to [Fig.9], at a first instant t1, the rotor 3 is offset relative to the electric machine axis X and is located at 12 o'clock, i.e. close to the power channel C1. As the rotor 3 follows a clockwise precession movement P+, it will move at a second instant t2 at 3 o'clock towards the power channel C2. In other words, the rotor 3 will move to the right with reference to [Fig.10].

[0079] In this example, still with reference to [Fig.9], the correction device 5 has received a setpoint command Com_cons imposing generator operation in which each control parameter P1-P4 of a power channel C1-C4 corresponds to a current collection.

[0080] To take into account the precession level NP, the correction device 5 determines a control command Com in which the control parameter P3 is modified to command a current injection on the power channel C3. As a result, the power channel C3 applies a magnetic force F3 which accompanies the rotation of the rotor 3 (direction opposite to the setpoint), that is to say, in the same direction as the magnetic force F1 applied by the power channel C1. The magnetic forces F2, F4 compensate each other while the magnetic forces F1, F3 add up to generate an overall magnetic force FG which tends to move the rotor 3 to the left, that is to say, in a manner opposite to the precession movement P+. As a result, the precession movement P+ of the rotor 3 is damped between the times t1 and t2. The power channels C1, C2, C4 continue to collect current.

[0081] Advantageously, a new overall magnetic force FG is determined each time the rotor 3 passes in front of a power channel C1-C3. For this purpose, with reference to [Fig. 10], at the second instant t2, the rotor 3 is offset relative to the electric machine axis X and is located at 3 o'clock, i.e. close to the power channel C2. As the rotor 3 follows a clockwise precession movement, it will move at the third instant t3 at 6 o'clock towards the power channel C3. In other words, the rotor 3 will move downwards.

[0082] As already presented previously, the correction device 5 has received a setpoint command Com_cons imposing generator operation in which each control parameter P1-P4 of a power channel C1-C4 corresponds to a current collection.

[0083] To take into account the precession level NP, the correction device 5 determines a control command Com in which the control parameter P4 is modified. to control a current injection on the power channel C4. As a result, the power channel C4 applies a magnetic force F4 which accompanies the rotation of the rotor 3, i.e., in the same direction as the magnetic force F2 applied by the power channel C2. The magnetic forces F1, F3 compensate each other while the magnetic forces F2, F4 add up to generate an overall magnetic force FG which tends to move the rotor 3 upwards, i.e., in a manner opposite to the precession movement P+. The power channels C1, C2, C3 continue to collect current.

[0084] Each time the rotor 3 approaches a power channel C1-C4, the precession movement P+ can be gradually compensated while continuing to collect current in accordance with the setpoint command Com_cons.

[0085] Preferably, the correction device 5 is configured to circulate a correction current successively in several power channels C1-C4 so as to generate an overall magnetic force FG opposing the precession movement over time. Preferably, the current injections are carried out successively following the precession movement P+, that is to say, in a clockwise direction. The overall magnetic force FG is thus rotating to optimally compensate for the precession movement.

[0086] Preferably, the correction device 5 is configured to circulate a correction current with a phase advance relative to the precession movement of the rotor 3 so as to modify the trajectory and achieve damping. Preferably, the phase advance is determined by feedback or learning. According to a particular implementation, the phase advance corresponds to the angular spacing between two consecutive power channels C1-C4.

[0087] It goes without saying that an overall magnetic force FG could also be obtained by adjusting the control parameters P1-P4 as illustrated in [Fig. 12], for example, by increasing the collection of the first power channel Cl so as to increase the resistive magnetic force Fl in order to obtain an overall magnetic force FG equivalent to that presented in [Fig.9] (modulation of the setpoint current).

[0088] An organization by pair of diametrically opposed power channels C1-C4 makes it easier to determine an overall magnetic force FG. When a single power channel is used, the others can continue to perform their collection / injection function. It goes without saying that several control parameters could be modified in order to generate the desired overall magnetic force FG.

[0089] The precession level NG is preferably monitored in a current manner in order to dynamically adapt the control command Com and the resulting overall magnetic force FG. Preferably, as soon as the precession level NG is below a predetermined threshold, the correction is stopped and the setpoint command Com_cons is no longer modified. Preferably, a control loop is implemented to allow the correction to be adapted.

[0090] Preferably, the control commands Com are recorded as well as the associated rotation speeds of the propulsion shaft A. This makes it possible to determine, at a given speed, whether the overall magnetic force FG is consistent with past corrections. Advantageously, a malfunction of the electrical machine can be determined if the overall magnetic force FG is higher than anticipated. Advantageously, a state of wear of the turbomachine T can be estimated by knowing the overall magnetic force FG, which makes it possible to carry out predictive maintenance operations.

[0091] An electrical machine 1 operating in generator mode has been presented. It goes without saying, however, that the invention applies in a similar manner to an electrical machine operating in motor mode. For this purpose, one power channel can collect current while the others inject current.

[0092] With reference to [Fig. 13], an integration of an electrical machine at the free ends of the blades of a fan F of a turbomachine T comprising a fan casing 9 is presented. In this example, the rotor 3 is positioned at the free ends of the blades of the fan F while the stator 2 is mounted on the fan casing 9. Such an electrical machine 1 makes it possible to collect electrical energy but also to drive the fan F in rotation. The positioning of the electrical machine 1 makes it possible to correct any orbiting movement of the fan F, which improves the comfort of the passengers in the aircraft. The wear of the turbomachine is also reduced. In this example, the sensor 51 of the correction device 5 is mounted on the fan casing 9.Such integration of the electric machine 1 makes it possible to use a large number of power channels at the periphery of the fan casing 9 and thus allow progressive damping.

[0093] By means of the invention, a precessional movement of a rotor of an electric machine can be dynamically damped for various types of vibration. Advantageously, the damping can be carried out during operation of the electric machine, which only slightly affects its efficiency during both motor operation and generator operation.

Claims

Claims

1. Electrical machine (1), in particular for an aircraft turbomachine (T), comprising: • A stator (2) comprising at least three power channels (C1-C4) and a rotor (3) configured to magnetically interact with the power channels (C1-C4), • The electrical machine (1) being configured, on the one hand, to operate in a generator mode in order to draw mechanical power from the rotor (3) to generate electrical power and to operate, on the other hand, in a motor mode in order to consume electrical power to generate mechanical power and drive the rotor (3), • A control device (4) configured to determine a control parameter (P1-P4) for each power channel (C1-C4) as a function of a control command (Com), each control parameter (P1-P4) defining the currents flowing in a power channel (C1-C4), each power channel (C1-C4) generating a magnetic force (F1-F4) on the rotor (3) which is a function of its control parameter (P1-P4), all of the magnetic forces (F1-F4) applied by the power channels (C1-C4) on the rotor (3) defining an overall magnetic force (FG), and • A correction device (5) configured to correct a precession movement of the rotor (3) relative to the stator (2), the correction device (5) being configured to: • determine (El) a precession level (NP) of the rotor (3) relative to the stator (2), • determine (E2) the control command (Com) of the control device (4) from a setpoint command (Com_cons) and the precession level (NP), the control command (Com) being configured to generate an overall magnetic force (FG) opposing the precession movement of the rotor (3) so as to dampen it.

2. Electrical machine (1) according to claim 1, in which the correction device (5) is configured, during operation in generator mode, to determine a control command (Com) consisting of injecting or modulating a current into only one power channel at a given instant, the other power channels being configured to collect currents at the given instant.

3. Electrical machine according to one of claims 1 to 2, in which the correction device (5) is configured to determine a control command (Com) consisting of successively injecting or modulating a current into several power channels (C1-C4) so ​​as to generate a global rotating magnetic force (FG) opposing the precession movement (P+) over time.

4. Electrical machine according to one of claims 1 to 3, in which the correction device (5) is configured to determine a control command (Com) consisting of injecting or modulating a current according to a phase advance relative to the precession movement (P+) of the rotor (3).

5. Electrical machine according to one of claims 1 to 4, in which the stator (2) comprises at least one pair of diametrically opposed power channels (C1-C4).

6. Electrical machine according to one of claims 1 to 5, in which the stator (2) comprises at least four power channels (C1-C4) angularly spaced by 90°.

7. Aircraft turbomachine (T) comprising at least one propulsion shaft (A) and an electric machine (1) according to one of claims 1 to 6, the rotor (3) of which is securely connected to the propulsion shaft (A).

8. Aircraft turbomachine (T) according to claim 7 in which the propulsion shaft (A) is integral with a fan (F) comprising a plurality of fan blades, the fan (F) being mounted in a fan casing (9).

9. Aircraft turbomachine (T) according to claim 8 in which the rotor (3) is mounted at the free ends of the fan blades, the stator (2) being mounted on the fan casing (9).

10. Method for monitoring an electrical machine (1) according to one of claims 1 to 6, a setpoint command (Com_cons) being defined, the method comprising steps consisting of:

11. • determine (El) a precession level (NP) of the rotor (3) relative to the stator (2), • determine (E2) the control command (Com) of the control device (4) from a setpoint command (Com_cons) and the precession level (NP), the control command (Com) generating an overall magnetic force (FG) opposing the precession movement (P+) of the rotor (3) so as to dampen it. Monitoring method according to claim 10, comprising steps consisting of: • Record the global magnetic forces (GMF) generated over time and • estimate a state of wear of the turbomachine (T) from the global magnetic forces (FG) recorded over time.

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