TURBOMACHINE MODULE EQUIPPED WITH AN ELECTRIC MACHINE

Abstract

The invention relates to a module for a turbomachine comprising a shaft in an axial direction and an electric machine (110), the electric machine comprising a system (150) for detecting a balance defect adapted to measure a parameter representative of the vibrations of the rotor of the electric machine and to determine a mechanical force (F1) representative of the balance defect from the measurements of these vibrations; and at least one of the coils (134) of the stator of the electric machine, called the balancing coil, is adapted to be supplied with a balancing supply current dependent on the determined mechanical force (F1), said balancing supply current generating a magnetic field so as to apply to the rotor of the electric machine a magnetic force (F2) opposing the determined mechanical force (F1). Figure for abstract: Figure 4

Description

Title of the invention: TURBOMACHINE MODULE EQUIPPED WITH AN ELECTRIC MACHINE Technical field

[0001] The technical field of the invention is that of turbomachines equipped with an electric machine.

[0002] The present invention relates in particular to an aircraft turbomachine module equipped with an electric machine. Prior art

[0003] The aeronautical world is currently asking itself many questions about the relevance of using hybrid engines for commercial aviation. The use of electrical energy is currently being considered not only to meet aircraft functions but also to electrify turbomachine functions.

[0004] This observation leads to the study of hybrid engine architecture solutions, combining fossil fuel energy and electrical energy to ensure the drive of the propulsion part (fan or turbine of the turbomachine) and the power supply of certain engine and / or aircraft functions.

[0005] These architectures can in particular be based on a high dilution ratio and reducer type architecture, but also on multiple bodies (two or three). In these architectures, the turbomachine comprises a low pressure body and a high pressure body, each body comprising a shaft connecting a rotor of a compressor to a rotor of a turbine.

[0006] It is known to equip an aircraft turbomachine with an electric machine. It is recalled that an electric machine is an electromechanical device based on electromagnetism allowing the conversion of electrical energy for example into work or mechanical energy. This process is reversible and can be used to produce electricity.

[0007] Thus, depending on the final use of an electric machine, the terms: - generator to designate an electrical machine producing electrical energy from mechanical energy, - motor for an electric machine producing mechanical energy from electrical energy.

[0008] An electrical machine can also behave in motor mode according to a first operating phase and in generator mode according to a second operating phase distinct from the first.

[0009] Thus, the electrical machines in question here are electricity generators or reversible machines that can also work as an electric motor and which are then capable of starting a turbine or fan shaft or at least of providing it with additional power. They can complement the electricity generator that is usually found on the accessory box (AGB) and which draws power from the high-pressure body if the electrical machine is integrated on the low-pressure body of a turbomachine.

[0010] Several installation zones are possible but the advantages and disadvantages of each are numerous and diverse (problem of mechanical integration of the machine, temperature resistance of the machine, accessibility of the machine, etc.). For example, patent application FR 3 087 823 A1 describes the installation of an electrical machine downstream of a blower. In addition, the electrical machine can also be installed downstream of a turbine shaft and driven by this shaft.

[0011] The electrical machine has a generally annular shape and comprises a rotor and a stator. The rotor and the stator each have a generally cylindrical shape extending around the axis of the turbomachine. The rotor generally comprises a disk and magnetic elements (for example, permanent magnets) arranged regularly around the periphery of the disk while the stator comprises a ring supporting coils distributed regularly in an annular manner inside the stator ring. The stator surrounds the rotor. In other words, the stator ring and the rotor disk are concentric and the stator ring is radially outside the rotor disk. In other words, the coils are arranged radially outside relative to the magnetic elements.

[0012] Parts rotating around an axis of rotation, such as the rotors of a compressor, a turbine or an electrical machine, generally have, following their manufacture, a balancing defect called unbalance, which is due to a non-coincidence of the axis of rotation of a part with its axis of inertia. This non-coincidence leads to the appearance of mechanical forces which can damage the equipment in which the rotating parts are present, and cause vibrations and / or noise.

[0013] These eccentricity defects are of static or dynamic origin. Static eccentricity is linked to assembly defects (assembly between parts) whereas dynamic eccentricity is a defect that commonly appears in overall dynamics. It is linked to the presence of mechanical imbalance. More specifically, a commonly encountered static unbalance is one in which the part's axis of inertia is parallel to, but distinct from, the part's axis of rotation. Another known balance defect is torque unbalance (otherwise known as torque unbalance), in which the center of gravity is located on the axis of rotation but the axis of inertia forms a non-zero angle with the axis of rotation. The combination of a static unbalance and an unbalance torque is called dynamic unbalance. The unbalance torque is, however, negligible when the diameter of the part is large compared to the length of the part, and the dynamic unbalance is equivalent to the static unbalance.

[0014] In the particular case of an electrical machine rotor, these defects modify the width of the air gap and consequently the permeance of the magnetic circuit. The electromagnetic efficiency of the machine is therefore locally greater and creates a radial return force oriented along the azimuth of the closing of the air gap clearance. It is therefore a so-called magnetic unbalance force which is added to the already existing mechanical unbalance and at the origin of the initial eccentricity.

[0015] To correct mechanical unbalance, current manufacturing processes include a balancing step, in which mass is added to or removed from the part, in particular a rotor, so as to bring the axis of inertia closer to the axis of rotation. More precisely, mass is added to the rotating part or the rotor at the axial station closest to the unbalance defect to be corrected and at the azimuth opposite the identified defect. This traditional balancing requires providing a position for adding the mass with a flange with a fairly fine angular discretization. In addition, it is also necessary to provide the definition of the parts allowing the addition of the mass: screw, nut, weight, clips, etc. which are parts dedicated to balancing the rotating part but greatly increase the mass of the turbomachine concerned.

[0016] However, certain parts may have an unbalance that worsens during operation, due to changes in the part over time (for example wear) and / or due to the environment (for example a change in temperature, pressure, etc.). This unbalance is therefore not correctable by conventional balancing methods (addition or removal of material). Furthermore, during operation of the turbomachine and even in full flight of the aircraft equipped with said turbomachine, a significant unbalance may appear in the event of a limit load, for example following the ingestion of a bird in the turbomachine or the loss or damage to a blade of the fan disk. This unbalance may cause a significant imbalance causing an eccentricity which results in the local closing of the air gap of the electric machine. The eccentricity linked to the loss of blade being greatly greater than the clearance between the magnetic elements of the rotor and the coils of the stator of the electric machine, there is then contact between said magnetic elements and said coils of the electric machine. Today, the air gap of an electrical machine is calculated to avoid any contact between the magnetic elements of the rotor and the stator coils. This imposes several constraints: - either a large air gap to respond to significant maneuvering or failure cases, - or the most complete mechanical decoupling possible between the electric machine and the rest of the turbomachine, which imposes integration constraints as described in patent FR 3 087 823.

[0017] However, a large air gap is detrimental to the performance of the electrical machine and mechanical decoupling imposes significant integration constraints (addition of decoupling elements, positioning of the assembly downstream of the turbomachine, etc.).

[0018] Solutions for eliminating this imbalance, which worsens during operation, have been proposed, using balancing systems comprising movable masses so as to modify the balancing of the part. However, these solutions are either suboptimal or expensive, and sometimes difficult to adapt to rotating parts of small size and at high rotation speed.

[0019] The objective of the present invention is to overcome at least some of the problems mentioned in the above. In particular, the present invention proposes a solution making it possible to balance a turbomachine rotor comprising an electric machine without adding additional mass which could degrade the performance of the turbomachine. Summary of the invention

[0020] For this purpose, the invention relates to a module for a turbomachine, in particular for an aircraft turbomachine, comprising a shaft extending in an axial direction and an electrical machine comprising: - a rotor coupled in rotation with the shaft of the module, the rotor comprising a disk and magnetic elements arranged regularly around the periphery of the disk, and - a stator secured to a module casing comprising a ring and coils distributed in an annular manner inside the stator ring, the coils are arranged outside the magnetic elements of the rotor in a radial direction. According to the invention, the electrical machine comprises a system for detecting a balancing defect adapted to measure a parameter representative of the vibrations of the rotor and to determine a mechanical force representative of the balancing defect from the measurements of these vibrations; and at least one of the coils, called the balancing coil, is adapted to be supplied with a balancing supply current dependent on the determined mechanical force, said balancing supply current generating a magnetic field so as to apply to the rotor a magnetic force opposing the determined mechanical force.

[0021] A rotor is understood to mean a part that can be rotated, via a magnetic field, by an electric rotating machine comprising a stator. The rotor is held and guided in rotation by bearings, for example of the rolling bearing type.

[0022] Thus, the invention proposes to exploit the electrical machine installed in the turbomachine for hybridization problems in order to achieve the balancing of a rotor of the turbomachine. Thanks to the invention, the balancing is adapted to the balancing defect (or unbalance) detected during the rotation of the rotor in operating condition, and can therefore compensate for any degradation of balancing over time, for example expansions due to temperature, pressure, wear, or the ingestion of birds in the turbomachine or damage to a blade of the fan disk. We can thus speak of self-adaptive rotor balancing. Thanks to the measurement of the vibrations, the system can progressively balance the rotor by learning, so as to reduce as much as possible the vibrations of the rotor due to the unbalance. This reduction of vibrations makes it possible to reduce the wear of the rotor and the bearings holding the rotor, as well as the noise of the rotor in operation.

[0023] More specifically, the invention proposes to control the magnetic fluxes generated by the coils to limit or even cancel the magnetic unbalance forces induced by an ex-centering of the rotor. Indeed, the invention advantageously proposes to control the power by magnetic pole individually to thus limit the magnetic force on the side of the eccentricity. The use of a magnetic field to compensate for the mechanical force due to the lack of balance (also called unbalance force), makes it possible not to add additional friction.

[0024] Thus, in the event of damage resulting in an eccentricity of the rotor of the electrical machine in operation, such as the ingestion of a bird in the turbomachine or the loss or damage to a blade of the fan disk, the invention advantageously makes it possible to limit the imbalance. The invention limits the performance of the electrical machine during the time necessary to make the electrical machine and therefore the turbomachine safe by allowing the aircraft to land. Thus, the temporary degradation of the performance of the electrical machine makes it possible to protect it while waiting for maintenance action by limiting the risks of contact between the rotor and the stator of the electrical machine.

[0025] The invention thus makes it possible to balance a turbomachine rotor comprising an electric machine by making use of the parts already available in the turbomachine and consequently without adding additional mass which could degrade the performance of the turbomachine in the long term.

[0026] The module for a turbomachine according to the invention may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another according to all technically possible combinations: - the electric machine includes a suitable coil feed device to supply the coils with supply current, each coil being supplied individually by the supply device, and in that the detection device is adapted to transmit to the supply device an instruction indicating the frequency, the phase and the amplitude of the balancing supply current as a function of the mechanical force determined for the or each balancing coil; - the balance fault detection system comprises a vibration sensor adapted to generate a vibration signal representative of the amplitude of the vibrations measured as a function of time, and in that the balance fault detection system comprises a calculation unit adapted to calculate a Fourier transform of said vibration signal and to determine the balance fault from said Fourier transform and the rotational speed of the rotor; - the calculation unit is configured to determine the setpoint indicating the frequency, phase and amplitude of the balancing supply current as a function of the mechanical force determined for the or each balancing coil.

[0027] The invention also relates to a turbomachine, in particular an aircraft turbomachine, comprising at least one module according to the invention and as described previously.

[0028] Preferably, the module is a blower module comprising a blower and the electrical machine is mounted coaxially with the axis of the blower and downstream of the blower, the rotor of the electrical machine being rotationally coupled with the blower.

[0029] Alternatively, the module is a turbine module and the electric machine is mounted coaxially with the turbine module and downstream of a turbine housing.

[0030] According to another embodiment, the electric machine is integrated into the heart of the turbomachine. It is for example mounted on the high pressure body of the turbomachine.

[0031] The invention also relates to a method for balancing a rotor of a module according to the invention and as described previously, comprising at least the following steps: - detect a balancing defect by measuring a parameter representative of rotor vibrations; - determine a mechanical force representative of the balance defect from vibration measurements; - determining the at least one balancing coil adapted to be supplied with a balancing supply current depending on the determined mechanical force and determining the balancing supply current as a function of the mechanical force determined for the or each balancing coil; - individually supplying the at least one balancing coil with the balancing supply current. Brief description of the drawings

[0032] The present invention will be better understood and other details, characteristics and advantages of the present invention will appear more clearly on reading the description of a non-limiting example which follows, with reference to the appended drawings in which: - [Fig.l] is a schematic axial sectional view of an example of an aircraft turbomachine to which the invention applies, the example illustrated is a turbomachine with a high bypass ratio and reduction gear; - [Fig.2] is a schematic sectional view of an electrical machine equipping a module according to the invention, along a plane perpendicular to the axis of rotation of the rotor, in a nominal case where the rotor is balanced; - [Fig.3] represents a schematic cross-sectional view of the electric machine of [Fig.2] in a case where the rotor is unbalanced; - [Fig.4] is a schematic view of the electrical machine equipping a module according to the invention; - [Fig.5] is a schematic cross-sectional view of the electric machine of [Fig.2] after rebalancing of the rotor; and - [Fig.6] represents a block diagram illustrating a method of balancing a rotor of a module according to the invention.

[0033] Elements having the same functions in different implementations have the same references in the figures.

[0034] In the figures, the scales and proportions are not strictly respected, for the purposes of illustration and clarity. Description of the embodiments

[0035] Reference is first made to [Fig. 1] which schematically represents a twin-spool, twin-flow aircraft turbomachine 10 to which the invention applies. Of course, the invention can be applied to other types of turbomachine equipped with an electric machine, for example a turboprop, without departing from the scope of the invention.

[0036] The turbomachine 10 has a longitudinal axis denoted C around which its various components extend.

[0037] The turbomachine 10 conventionally comprises a gas generator 12 upstream of which a fan 14 is arranged. The fan 14 is surrounded by a fan casing 16 which is surrounded by a nacelle 18 which extends around and along a major part of the gas generator 12.

[0038] The gas generator 12 here comprises two bodies, namely a low pressure body 12a or LP and a high pressure body 12b or HP. Each body comprises a com- presser and a turbine.

[0039] In the present invention, and generally, the terms “upstream” and “downstream” are defined with respect to a main direction F of circulation of the fluids inside the turbomachine, and here along the longitudinal axis C, that is to say from left to right with reference to [Fig. 1].

[0040] From upstream to downstream, the gas generator 12 comprises a low pressure compressor 20, a high pressure compressor 22, a combustion chamber 24, a high pressure turbine 26 and a low pressure turbine 28.

[0041] The longitudinal axis C is the axis of rotation of the moving elements of the turbomachine 10, and in particular, of the turbines 26, 28.

[0042] The fan 14 comprises an annular row of blades 30 driven in rotation by a fan shaft 32 which is connected to the rotor of the low-pressure body 12a via a reducer 33. The gas flow which passes through the fan (arrow F) is separated upstream of the gas generator 12 by an annular nozzle 34 into a radially internal annular flow, called primary flow 36 which feeds the gas generator 12, and into a radially external annular flow, called secondary flow 38 which flows between the gas generator 12 and the nacelle 18 and provides the majority of the thrust of the turbomachine.

[0043] An inlet casing 40 structurally connects the gas generator 12 to the fan casing 16 and to the nacelle 18. The inlet casing 40 comprises an annular row of radially internal arms 42 extending into the primary flow 36, and an annular row of radially external rectifier vanes 44 (OGV type) extending into the secondary flow 38. The arms 42 are generally limited in number (less than ten) and are tubular and crossed by services. The number of vanes 44 (OGV) is generally greater than ten.

[0044] The turbomachine comprises a module according to the invention comprising a shaft extending in an axial direction A, parallel to the longitudinal axis of the turbomachine and an electric machine 110. Zone ZI represents an area located between the fan disc 32 and the reducer 33, in which the electric machine can be installed. Zone Z2 represents another zone located downstream of the low pressure turbine 28 in which the electric machine can also be installed.

[0045] Alternatively, the electric machine can be integrated into the heart of the turbomachine, for example mounted on the high pressure body of the turbomachine.

[0046] In the description, the expressions “internal” or “interior” and “external” or “exterior” are used without limitation in reference to the radial distance from the longitudinal axis C around which the turbomachine extends, the expression “internal” defining a zone radially closer to the longitudinal axis of the nacelle, as opposed to the expression “external”. Furthermore, in the description and the claims, the terminology axial, radial and transverse will be adopted without limitation with reference to the trihedron A, R, T indicated in the figures, the axial axis A being parallel to the longitudinal axis C of the turbomachine.

[0047] Figures 2, 3 and 5 schematically represent a section of an electrical machine 110 equipping a module according to the invention.

[0048] Figures 2, 3 and 5 respectively illustrate a nominal state, an unbalanced state and a rebalanced state of the electrical machine, according to a section plane perpendicular to the axis of rotation of the rotor 120.

[0049] The electrical machine 110 has a generally annular shape and comprises a rotor 120 and a stator 130.

[0050] The rotor 120 has a generally cylindrical shape extending circumferentially around an axis of rotation coinciding with the axis C of the turbomachine. The rotor is coupled with the shaft of the module, that is to say the shaft of the fan if the electric machine is installed downstream of the fan (Zone Z1) or the shaft of the low-pressure turbine if the electric machine is installed downstream of the latter (Zone Z2).

[0051] The rotor 120 comprises an annular disk 122 and magnetic elements 124 arranged regularly on the periphery of the disk 122. The magnetic elements 124 are, for example, permanent magnets. The annular disk 122 is delimited by an inner circumferential surface 122A and an outer circumferential surface 122B. The magnetic elements 124 are radially inward relative to the outer circumferential surface 122B. By “arranged regularly on the periphery of the disk 122” is meant that the magnetic elements 124 are close to the outer circumferential surface 122B, that is to say that they are closer to the outer circumferential surface 122B than to the inner circumferential surface 122A in a radial direction.

[0052] Generally, the magnetic elements 124 are shrunk onto the disc 122 of the rotor 120. In other words, the rotor 120 comprises an inner annular shroud 126A forming the inner circumferential surface 122A of the rotor disc 122 and an outer annular shroud 126B arranged radially outside the magnetic elements 124 and radially inside the stator 130 and forming the outer circumferential surface 122B of the rotor disc 122. Preferably, the inner 126A and outer 126B shrouds are made of non-magnetic materials, for example non-magnetic forged steel.

[0053] The rotor 120 here comprises six magnetic elements 124 for the purposes of illustration and clarity, but may comprise a higher or lower number of magnetic elements 124, depending on the desired characteristics of the electrical machine (rotation speed in particular),

[0054] The stator 130 comprises a ring 132 also having a generally cylindrical shape extending circumferentially around the axis C of the module and the turbomachine. The stator 130 is integral with a casing of the module, for example the fan casing 16 (zone Z1). The ring 132 of the stator 130 is delimited by an internal surface 132A, that is to say a radially inner surface and an external surface 132B, that is to say a radially outer surface. The stator ring 132 supports a winding (not shown) distributed in an annular manner within the ring. The winding is formed of a plurality of magnetic poles or coils 134. More specifically, the stator ring 132 includes notches in which the coils are arranged. Each coil 134 is formed of a conductive wire wound around a support, the support being attached to the stator ring 132.

[0055] In the example illustrated, the stator 130 here comprises thirteen notches, and therefore thirteen coils 134, for the purposes of illustration and clarity, but may comprise a higher or lower number of notches and coils 134, depending on the desired characteristics of the electrical machine (rotation speed in particular), the number of pairs of poles of the winding, the frequency of the supply current of the winding, etc.

[0056] The stator 130 surrounds the rotor 120. In other words, the ring 132 of the stator and the disc 120 of the rotor are concentric and the ring 132 of the stator is radially outside the disc 120 of the rotor. The coils are arranged opposite the magnetic elements 124 of the rotor 120 in a radial direction R. In other words, the magnetic elements 124 of the rotor 120 are radially inside the coils of the stator 130.

[0057] Furthermore, the air gap of the electrical machine defined by the distance in a radial direction between the magnetic elements and the coils is between 0.5 mm and 10 mm.

[0058] As indicated previously, [Fig. 2] illustrates a nominal state of the electrical machine, that is to say in which the rotor has been previously balanced before being put into operation. Balancing can be carried out for example by a conventional method in which mass is added or removed from the rotor so as to bring the axis of inertia closer to the axis of rotation or by other methods. Thus, in this nominal operating state of the electric machine, the axis of rotation of the rotor 120 of the electric machine coincides with its axis of inertia. The stator 130 and the rotor 120 are coaxial. The rotor 120 is driven in rotation (represented by the arrow W), this being generated by a stator magnetic field Bs generated by the stator 130 of the electric machine and a rotor magnetic field BR generated by the rotor 120.

[0059] During operation of the turbomachine, and even in full flight of the aircraft equipped with said turbomachine, a significant imbalance may appear in the event of a limit load, for example following the ingestion of a bird in the turbomachine or the loss or damage to a blade of the fan disk. This imbalance may cause a significant imbalance causing an eccentricity of the rotor of the electric machine as illustrated in [Fig. 3]. In other words, there is a non-coincidence of the axis of rotation of the rotor with its axis of inertia; the rotor 120 and the stator 130 are no longer coaxial. The eccentricity of the rotor 120 causes the local closing of the air gap of the electric machine. This eccentricity can be greatly greater than the clearance between the magnetic elements of the rotor and the coils of the stator of the electric machine, there is then a high risk of contact between said magnetic elements and said coils of the electric machine.

[0060] The rotor 120 has an unbalance of mechanical and magnetic origin due to the eccentricity of the rotor. With reference to [Fig. 3] (and to FIGS. 2 and 5), in an orthogonal OXYZ reference frame where the line OZ is the axis of rotation of the rotor 120, which coincides with the longitudinal axis C of the turbomachine, the section is made along the plane XOY. Thus, the rotor has a balance defect corresponding to an axis of inertia of the rotor 120 parallel and not coincident with the axis OZ of rotation of the rotor 120. During rotation of the rotor 120, this unbalance manifests itself by a force perpendicular to the axis OZ of rotation of the rotor 120. In addition, the electromagnetic efficiency of the machine is locally greater due to the modification of the air gap dimension and creates a radial restoring force oriented according to the azimuth of the air gap clearance closure. These two efforts are symbolized in [Fig.3] by a mechanical force Fl. This force Fl is oriented along the OX axis in the figures.

[0061] According to the invention, to enable the reduction or cancellation of the unbalance and thus rebalance the rotor, at least one of the coils 134, called the balancing coil, is adapted to be supplied with a balancing supply current dependent on the mechanical force FL. The balancing supply current is adapted and configured to generate a magnetic field so as to apply to the rotor 120 a magnetic force F2 opposing the mechanical force Fl and preferably canceling it.

[0062] For this purpose, the electrical machine comprises a device 140 for supplying the coils 134 individually. The supply device 140 is adapted to supply the coils with supply current. The supply device 140 may comprise several inverter-type electrical power sources, each configured to supply polyphase current to an associated coil 134.

[0063] The electrical machine according to the invention further comprises a system 150 for detecting a balancing fault adapted to measure a parameter representative of the rotor vibrations and to determine a mechanical force Fl representative of the balance defect from measurements of these vibrations. Preferably, the system 150 for detecting an unbalance or balance defect comprises a vibration sensor 152 adapted to measure the amplitude of the vibrations as a function of time due to the unbalance of the rotor 120 and to generate a vibration signal representative of this amplitude of the vibrations measured as a function of time. The vibration sensor 152 is arranged close to the rotor 120, preferably at the level of the bearings (not shown) for holding and guiding the rotation of the rotor 120, or on any other fixed part of the machine. The measurement of the vibrations by the vibration sensor makes it possible to form a vibration signal representative of the amplitude of the vibrations measured as a function of time. This vibration signal is transmitted to a calculation unit 154 of the device 150 for detecting a balance defect, as represented by the arrow 153.

[0064] The calculation unit 154 is adapted to receive and process this vibration signal so as to extract from the vibration signal information representative of the unbalance and therefore of the force FL.

[0065] For example, the calculation unit 154 is adapted to calculate a Fourier transform of said vibration signal and to determine the balance defect, therefore the characteristics of the force Fl, from said Fourier transform and the rotation speed of the rotor 120. The Fourier transform of the vibration signal makes it possible to obtain a frequency spectrum of the vibrations measured by the vibration sensor 152. By analyzing the Fourier transform, in particular on certain frequencies depending on the rotation speed of the rotor 120, it is possible to determine in particular the amplitude of the unbalance, representative of the mechanical force Fl, and the phase of the unbalance, representative of the position of the unbalance. The rotation speed of the rotor 120 can for example be determined by a dedicated sensor arranged near the rotor.

[0066] The calculation unit 154 is further configured to determine a setpoint indicating the frequency, the phase and the amplitude of the balancing supply current as a function of the force Fl determined for the or each balancing coil from the determined unbalance characteristics.

[0067] The power supply instructions are transmitted to the power supply device 140, as represented by the arrow 155, and said power supply device 140 applies these power supply instructions to power the coils 134 including the balancing coils.

[0068] By balancing supply current is meant a supply current different from the supply current applied to a coil in the nominal case ([Fig.2]). This corrected supply current depends on the force Fl determined to limit or even cancel the unbalance. A balancing coil is a coil supplied with a balancing supply current, i.e. corrected with respect to the nominal case to correct the balancing defect.

[0069] The balancing instructions are different from one balancing coil to another.

[0070] The calculation unit 154 being configured to determine a setpoint called setpoint balancing for each balancing coil, it is therefore also configured to determine said balancing coil(s).

[0071] Indeed, all the coils can be balancing coils, that is to say they can all be supplied by an associated balancing supply current, that is to say corrected with respect to the nominal case.

[0072] Alternatively, only one coil may be a balance coil.

[0073] According to another variant, only a few coils are balancing coils, denoted 134E. In the example illustrated in [Fig.5], there are three balancing coils, i.e. powered by an associated balancing supply current, i.e. corrected with respect to the nominal case. In the example illustrated in [Fig.5], the three balancing coils 134E are separated from each other by at least one coil powered by a nominal supply current of the nominal case ([Fig.2]). Alternatively, the balancing coils may be adjacent to each other, i.e. close to each other.

[0074] According to one embodiment, the balancing coils 134E are deactivated. In other words, they are supplied with a zero balancing current.

[0075] The set of coils 134, including the balancing coils 134E, thus supplied by the supply device 140, generates a balancing magnetic field, that is to say modified compared to the nominal case. This balancing magnetic field applies to the rotor a magnetic force F2 opposing the force F1 representative of the unbalance, and therefore makes it possible to greatly limit the unbalance during the rotation of the rotor. Preferably, the magnetic force F2 is opposed to the force F1 representative of the unbalance, making it possible to compensate for the unbalance in order to balance the rotor 120 during its rotation.

[0076] Taking into account the rotation of the rotor 120, the polyphase current supply is variable so as to follow the rotation of the rotor 120, to apply the magnetic field so that the magnetic force F2 follows the direction of the force FL. Thus, the coils 134 will be alternately supplied or not depending on the position of the rotor 120.

[0077] This compensating force F2 is shown with reference to [Fig. 3], where the rebalanced rotor 120 of FIGS. 2 and 3 is shown in section. The force Fl due to the unbalance and the force F2 generated by the balancing system are such that the unbalance is greatly reduced ([Fig. 3]) or even cancels out. A greatly reduced residual unbalance is illustrated by the arrow F3 resulting from the difference between the force Fl and the force F2.

[0078] A method of balancing a rotor of a module according to the invention and as described previously will now be detailed with reference to [Fig.6] which illustrates a block diagram of this method.

[0079] This method comprises a step S100 of detecting a balance defect by measuring a parameter representative of the vibrations of the rotor 120. During this step S100, the vibration sensor 152 of the detection system 150 measures the vibrations of the rotor during its rotation. If the amplitude of the vibrations is greater than a predetermined threshold, a vibration signal representative of the amplitude of the vibrations measured as a function of time is generated by the vibration sensor 152 which transmits it to the calculation unit 154 of the detection system 150.

[0080] The method then comprises a step S200 of determining a force Fl representative of the balance defect from the vibration measurements. During this step S200, the calculation unit 154 calculates the unbalance to be corrected. For example, it calculates a Fourier transform of the transmitted vibration signal and determines the characteristics of the force Fl, from said Fourier transform and the rotation speed of the rotor 120. The Fourier transform of the vibration signal makes it possible to obtain a frequency spectrum of the vibrations measured by the vibration sensor 152. By analyzing the Fourier transform, in particular on certain frequencies depending on the rotation speed of the rotor 120, it is possible to determine in particular the amplitude of the unbalance, representative of the mechanical force Fl, and the phase of the unbalance, representative of the position of the unbalance.

[0081] Then, the calculation unit 154 determines the balancing coil(s) suitable for being supplied with a balancing supply current, as well as the latter, as a function of the mechanical force Fl determined during a step S300. During this step S300, the calculation unit 154 determines a setpoint indicating the frequency, the phase and the amplitude of the balancing supply current as a function of the force Fl determined for the or each balancing coil from the determined unbalance characteristics and transmits it or them to the supply device 140.

[0082] The method further comprises a step S400 of individually supplying the at least one balancing coil with the balancing supply current. During this step S400, the supply device 140 applies these supply instructions to supply the coils 134 including the balancing coils 134E.

[0083] The set of coils 134, including the balancing coil 134E, thus supplied by the supply device 140, generates a balancing magnetic field, i.e. a field modified compared to the nominal case. This balancing magnetic field applies to the rotor a magnetic force F2 opposing the force Fl representative of the unbalance, and therefore makes it possible to significantly limit or even cancel the unbalance during rotation of the rotor.

[0084] The method may further comprise a verification step S500 in which the vibration sensor 152 of the detection system 150 measures the vibrations of the rotor during its rotation. If the amplitude of the vibrations is greater than or equal to the amplitude of the vibrations measured in step S100, steps S200 to S400 are repeated until the amplitude of the vibrations after correction is less than the amplitude of the vibrations initially measured in step S100. This measurement of the vibrations is preferably carried out in real time in order to be able to adjust the unbalance correction in real time.

Claims

Claims

1. Module for a turbomachine, in particular for an aircraft turbomachine, comprising a shaft extending in an axial direction and an electrical machine (110) comprising: - a rotor (120) coupled in rotation with the shaft of the module, the rotor comprising a disc (122) and magnetic elements (124) arranged regularly on the periphery of the disc, and - a stator (130) secured to a casing of the module comprising a ring (132) and coils (134) distributed in an annular manner inside the ring of the stator, the coils are arranged outside the magnetic elements of the rotor in a radial direction, characterized in that the electrical machine comprises a system (150) for detecting a balance defect adapted to measure a parameter representative of the vibrations of the rotor and to determine a mechanical force (Fl) representative of the balance defect from the measurements of these vibrations;and in that at least one of the coils (134) called the balancing coil is adapted to be supplied with a balancing supply current dependent on the determined mechanical force (Fl), said balancing supply current generating a magnetic field so as to apply to the rotor (120) a magnetic force (F2) opposing the determined mechanical force (Fl).;

2. Module according to claim 1, in which the electrical machine comprises a device (140) for supplying the coils (134) adapted to supply the coils with supply current, each coil being supplied individually by the supply device (140), and in that the detection device (150) is adapted to transmit to the supply device (140) an instruction indicating the frequency, the phase and the amplitude of the balancing supply current as a function of the mechanical force (Fl) determined for the or each balancing coil.

3. Module according to claim 1 or 2, in which the balance fault detection system (150) comprises a vibration sensor (152) adapted to generate a vibration signal representative of the amplitude of the vibrations measured as a function of time, and in that the balance fault detection system (150) comprises a calculation unit (154) adapted to calculate a Fourier transform of said vibration signal and to determine the balance fault from of said Fourier transform and the rotational speed of the rotor (120).

4. Module according to claim 3 in combination with claim 2, wherein the calculation unit (154) is configured to determine the setpoint indicating the frequency, the phase and the amplitude of the balancing supply current as a function of the mechanical force (Fl) determined for the or each balancing coil.

5. Turbomachine, in particular aircraft turbomachine, comprising at least one module according to one of the preceding claims.

6. Method for balancing a rotor of a module according to one of the preceding claims 1 to 4, comprising at least the following steps: - detecting (S 100) a balancing defect by measuring a parameter representative of the vibrations of the rotor (120); - determining (S200) a mechanical force (Fl) representative of the balancing defect from the vibration measurements; - determining (S300) the at least one balancing coil adapted to be supplied with a balancing supply current dependent on the determined mechanical force (Fl) and determining the balancing supply current as a function of the mechanical force (Fl) determined for the or each balancing coil; - individually supplying (S400) the at least one balancing coil with the balancing supply current.

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