Synchronous electric machine for aircraft, associated propulsion device, turboshaft engine and method

Abstract

The invention relates to a synchronous electric machine (10) for aircraft, which comprises a stator (13) and a wound rotor (38) inserted into the stator, the stator comprising two sets of stator coils (47, 49) intended to be connected to different power converters, and the wound rotor comprising a rotor shaft (11) and two rotor coils (39, 40) each intended to be supplied with a different supply current. The two sets of stator coils are arranged in the stator in such a way that when a first set of stator coils (47) fails, the second set of stator coils (49) cooperates with at least the second rotor coil (40) supplied with the associated supply current in order to generate a mechanical torque on the rotor shaft, and so that the power converter connected to the first set of stator coils does not deliver any electrical power.

Description

[0001] DESCRIPTION

[0002] TITLE: Synchronous electric machine for aircraft, propulsion device, turboshaft engine and associated process

[0003] Technical field of the invention

[0004] The invention relates to rotating electrical machines for aircraft, and more particularly to wound rotor synchronous electrical machines for aircraft.

[0005] The invention further relates to a propulsion device and a propulsion system comprising such an electric machine, an aircraft comprising such a propulsion device or such a propulsion system, and a method for controlling such an electric machine.

[0006] State of the prior art

[0007] An aircraft, for example a twin-engine helicopter, of the vertical takeoff and landing (VTOL) type, comprises a propulsion system comprising two turbine engines, each turbine engine comprising a gas generator and a free turbine driven in rotation by the gas generator, and secured to an output shaft. The output shaft of each free turbine is adapted to set in motion a power transmission box, which itself drives the rotor of the helicopter. It is known that when the helicopter is in cruising flight (i.e. when it is operating under normal conditions, during all phases of flight, excluding transient phases of takeoff, climb, landing or hovering), the turbine engines develop low powers lower than the maximum continuous powers.These low power levels result in a specific consumption (hereinafter, Cs), defined as the ratio between the hourly fuel consumption by the combustion chamber of the turboshaft engine and the mechanical power supplied by this turboshaft engine, higher by around 30% than the Cs of the maximum take-off power, and therefore an excess fuel consumption in cruise flight. In order to reduce the fuel consumption of the helicopter, it is known in cruise flight situation to put one of the two turbines on standby, so that the other engine operates at high speed and therefore benefits from a much lower Specific Consumption.

[0008] In order to overcome critical situations, particularly in the event of failure of the gas turbine which is not on standby or in the event of an avoidance maneuver, it is necessary to quickly reactivate the standby turbine.

[0009] As this is a critical procedure, it is necessary to ensure a high level of reliability of the standby turbine reactivation procedure to guarantee the helicopter's flight safety.

[0010] Document FR3027058 discloses a helicopter comprising at least one turboshaft engine as described above, and a hybrid turboshaft engine comprising a turboshaft engine as described and a rapid reactivation system comprising two reactivation chains.

[0011] Each reactivation chain comprises a rotating electrical machine and a power conversion device controlling said machine.

[0012] The helicopter also includes an electrical energy storage unit and an on-board network supplying the power conversion devices.

[0013] Each electric machine allows the hybrid turbo engine to be quickly reactivated when it is on standby.

[0014] The redundancy of the reactivation chains ensures a high level of fallibility of the “rapid reactivation” function.

[0015] However, the redundancy of the reactivation chains increases the mass of the helicopter, thereby reducing the helicopter's payload and increasing the bulk of the rapid reactivation system.

[0016] Furthermore, it is known to replace at least one turbomachine intended to produce the thrust of a conventional take-off and landing (CTOL) type aircraft with an electric motor driving a propeller to reduce the high consumption of fossil fuel, in particular kerosene, of the aircraft.

[0017] Generally the electric motor includes a rotor equipped with permanent magnets

[0018] However, when the rotor is rotated by the propeller driven by an incident airflow, "windmilling" in English, the magnets generate an excitation flux in the motor which can induce short-circuit currents in the stator windings of the motor.

[0019] Short circuit currents heat the motor and can damage the motor.

[0020] Additionally, when a stator winding fails, the excitation flux generated by the permanent magnets induces a current in the failed stator winding that may propagate the failure.

[0021] Statement of the invention

[0022] The aim of the invention is to overcome all or part of these drawbacks.

[0023] In view of the above, the subject of the invention is a synchronous electrical machine for aircraft, comprising a stator and a wound rotor inserted in the stator, the stator comprising two sets of stator coils intended to be connected to different power converters, and the wound rotor comprising a rotor shaft and two rotor coils each intended to be supplied by a different supply current.

[0024] The two sets of stator coils are arranged in the stator such that when a first set of stator coils fails, the second set of stator coils cooperates with at least the second rotor coil supplied by the associated supply current to generate electrical energy at the terminals of the second set of stator coils or generate a mechanical torque on the rotor shaft, and such that the power converter connected to the first set of stator coils does not deliver electrical power. The faulty first set of stator coils is no longer supplied with electrical power in order to prevent the propagation of a fault by inducing a short-circuit current in the set of stator coils of the faulty converter in said machine and in the power converter connected to said faulty set of coils.

[0025] Despite the failure of the first set of coils, the second set of coils ensures the operation of the machine so that it delivers on its rotor shaft a mechanical torque equal to the nominal operating torque of the electrical machine or delivers an electrical power to its terminals equal to the nominal electrical power delivered by said machine, making it possible to increase the operational reliability of said electrical machine.

[0026] Preferably, the two rotor coils are arranged in series on the rotor shaft, the first set of stator coils and the second set of stator coils being arranged in the stator such that the first rotor coil and the first set of stator coils form a first electromagnetic converter, and such that the second rotor coil and the second set of stator coils form a second electromagnetic converter.

[0027] Advantageously, the rotor comprises two identical rotor magnetic half-masses extending in a longitudinal direction of the rotor and the stator comprises two identical stator magnetic half-masses extending in a longitudinal direction of the stator, each rotor coil being inserted into a different rotor magnetic half-mass and each set of stator coils being inserted into a different stator magnetic half-mass.

[0028] Preferably, the rotor comprises two sets of power supply rings, each set being connected to a different rotor coil, and in which the stator comprises two sets of brushes each supplying a different set of rings, each set of brushes being intended to be connected to one of the second power converters. Also provided is an aircraft propulsion device comprising an electrical machine as defined above, and a propulsion propeller connected to the rotor shaft.

[0029] Also proposed is a hybrid aircraft turbine engine comprising an electric machine as defined above and a turbine engine comprising a free gas turbine, the free turbine being further connected to the rotor shaft of the electric machine.

[0030] An aircraft comprising a propulsion device as defined above or a hybrid turboshaft engine as defined above is also proposed.

[0031] Also provided is a method for controlling a synchronous electrical machine for an aircraft, the electrical machine comprising a stator and a wound rotor inserted in the stator, the stator comprising two sets of stator coils connected to different power converters, and the wound rotor comprising a rotor shaft and two rotor coils each supplied with a different supply current.

[0032] The method comprises deactivating the faulty first set of stator coils by controlling the power converter connected to said first set so that said converter does not deliver electrical power to said set of coils, supplying electrical power to the second set of stator coils by the associated power converter, and at least supplying the second coil with the associated supply current to generate a mechanical torque on the rotor shaft or generating electrical energy across the second set of stator coils.

[0033] Preferably, the rotor comprising two identical rotor magnetic half-masses extending in a longitudinal direction of the rotor and the stator comprising two identical stator magnetic half-masses extending in a longitudinal direction of the stator, each rotor coil being inserted in a different rotor magnetic half-mass and each set of stator coils being inserted in a different stator magnetic half-mass, the method comprising controlling the supply currents so that the amplitude of the supply current supplying the rotor coil of a rotor half-mass covering the first set of stator coils decreases, so that said current is substantially zero when said rotor half-mass covers the entire first set of stator coils, and so that the amplitude of said current increases when said rotor half-mass uncovers the first set of stator coils,the effective value of said current being non-zero.,

[0034] Advantageously, each supply current is sinusoidal.

[0035] Brief description of the drawings

[0036] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

[0037] [Fig 1] schematically illustrates a first example of an aircraft according to the invention;

[0038] [Fig 2] illustrates an electrical diagram of a first example of an electrical machine according to the invention;

[0039] [Fig 3] schematically illustrates a section of the first example of the electric machine according to the invention;

[0040] [Fig 4] illustrates an electrical diagram of a second example of an electrical machine according to the invention;

[0041] [Fig 5] schematically illustrates a radial section of the second example of the electric machine according to the invention,

[0042] [Fig 6] illustrates a schematic modeling of the second example of the electrical machine according to the invention,

[0043] [Fig 7] schematically illustrates the evolution of the rotor currents of the second example of the electrical machine according to the invention, and

[0044] [Fig 8] schematically illustrates a first example of an aircraft according to the invention.

[0045] Detailed description of at least one embodiment We refer to figure 1 which schematically illustrates an example of an aircraft 1 of the twin-engine VTOL type comprising a propeller 2, a gearbox 3, a turboshaft engine 4 and a hybrid turboshaft engine 5.

[0046] The turboshaft engine 4 and the hybrid turboshaft engine 5 drive the propeller 2 via the gearbox 3.

[0047] The turboshaft engine 4 comprises a gas generator 6 producing hot gases from the combustion of a fuel such as kerosene, and a free turbine 7 connected to a primary inlet of the gearbox 3.

[0048] The hot gases generated by the gas generator 6 drive the free turbine 7 which in turn generates a mechanical torque driving the propeller 2.

[0049] The hybrid turbine engine 5 comprises a gas generator 8 producing hot gases from the combustion of a fuel such as kerosene, a free turbine 9 connected to a first input of the gearbox 3, an electric machine 10 comprising a rotor shaft 11 connected to the free turbine 9, and control means 12 of the machine 10.

[0050] The hot gases generated by the gas generator 8 drive the free turbine 9 which in turn generates a mechanical torque driving the propeller 2.

[0051] The machine 10 can operate in a motor mode so as to deliver a mechanical driving torque to drive the free turbine 9 or in a generator mode so that the free turbine 9 drives the rotor shaft 11 and the machine 10 produces electrical energy.

[0052] When the helicopter is in cruising flight condition, the gas generator 8 of the hybrid turboshaft engine 5 is shut down to save fuel.

[0053] When reactivation of the hybrid turboshaft engine 5 is necessary, for example during an obstacle avoidance maneuver in flight or when the turbomachine 4 is faulty, the machine 10 drives the free turbine 9 to facilitate the starting of the hybrid turboshaft engine 5.

[0054] Machine 10 is of the polyphase synchronous type with wound rotor. It is assumed in the following that machine 10 is three-phase.

[0055] Figure 2 illustrates an electrical diagram of a first example of the machine 10 and the control means 12.

[0056] The machine 10 comprises a stator 13 comprising a first set of stator coils and a second set of stator coils (not shown in this figure).

[0057] The coils of the first set form a first set of three phases coupled for example in star or delta, each phase having the same number of poles.

[0058] The coils of the second set form a second set of phases coupled for example in star or delta, each phase having the same number of poles as the phases formed by the first set of coils.

[0059] Each set of coils is powered by a different reversible 14, 15 power converter.

[0060] Each converter 14, 15 comprises supply terminals 16, 17, 18, 19 and output terminals 180, 190, 200, 210, 220, 230.

[0061] The first converter 14 is connected to a first electrical power supply network RI of the helicopter, and the second converter 15 is connected to a second electrical power supply network R2 of the helicopter.

[0062] The RI and R2 networks are independent so that if one of the networks fails, the other network is functional.

[0063] Each of the phases of the first set of three phases comprises a connection terminal 24, 25, 26 connected to a different output terminal 180, 190, 200 of a first power converter 14, and each of the phases of the second set of three phases comprises a connection terminal 27, 28, 29 connected to a different output terminal 210, 220, 230 of the second power converter 15.

[0064] Since the architecture of the converters 14, 15 is identical, only a first converter 14 supplying the first set of stator coils is detailed.

[0065] The first converter 14 comprises as many switching arms 30, 31, 32 as there are phases of the machine 10. Each switching arm 30, 31, 32 comprises a first switching cell 33 comprising for example a field effect transistor 34 and a diode 35. The gate of the transistor 35 is controlled by control means 240 comprising for example a controller.

[0066] The drain of transistor 34 is connected to a first supply terminal 16 and to the cathode of diode 35, the source of transistor 34 is connected to the anode of diode 35 and to an output terminal 180, 190, 200.

[0067] Each switching arm 30, 31, 32 further comprises a second switching cell 36 comprising for example the field effect transistor 34 and the diode 35 arranged so that the drain of the transistor 34 is connected to an output terminal 180, 190, 200 and to the cathode of the diode 35, and the source of the transistor 34 is connected to the anode of the diode 35 and to the second supply terminal 17.

[0068] The first converter 14 further comprises one or more filter capacitors 37 extending between the supply terminals 16, 17.

[0069] The machine 10 further comprises a wound rotor 38 comprising two rotor coils 39, 40 comprising power supply terminals 41, 42, 43, 44.

[0070] The power supply terminals 41, 42 of a first rotor coil 39 are connected to a third electrical power supply network R3, and the power supply terminals 43, 44 of the second rotor coil 40 are connected to a fourth electrical power supply network R4.

[0071] Networks R3 and R4 are independent so that if one network fails, the other network is functional.

[0072] The first set of stator coils, the second set of stator coils, the first rotor coil 38 and the second rotor coil 40 are arranged in the machine 10 such that the first set of stator coils and the first rotor coil 39 cooperate to deliver a mechanical torque to the rotor shaft 11 or to deliver electrical power to the connection terminals 24, 25, 26, and such that the second set of stator coils and the second rotor coil 40 cooperate to deliver a mechanical torque to the rotor shaft 11 or to deliver electrical power to the connection terminals 27, 28, 29.

[0073] The control means 12 comprise the first and second converters 14, 15 and the piloting means 240.

[0074] The control means 240 are produced for example from a controller.

[0075] The first set of stator coils and the first rotor coil 39 form a first electromagnetic converter 45 (not shown), and the second set of stator coils and the second rotor coil 40 form a second electromagnetic converter 46 (not shown) independent of the first electromagnetic converter.

[0076] The control means 240 control the power converters 14, 15 so that when one of the first and second electromagnetic power converters is faulty, the power converter 14, 15 connected to the set of stator coils of said faulty converter does not deliver electrical power and so that the other electromagnetic converter is functional to generate a mechanical torque or generate electrical energy at the terminals of the set of stator coils of the functional electromagnetic converter.

[0077] Furthermore, the control means 240 deactivate the power supply to the rotor coil of the faulty converter to de-energize the rotor of the faulty converter so as to prevent the propagation of the fault by inducing a short-circuit current in the set of stator coils of the faulty converter.

[0078] The stator coils and rotor coil of the functional electromagnetic converter are energized despite the failure of the other electromagnetic converter.

[0079] Each electromagnetic converter 45, 46 is sized so that it ensures rapid reactivation of the hybrid turboshaft engine 5, increasing the reliability of the reactivation function. When the networks RI, R2, R3 and R4 are all independent, the reliability of the reactivation function is improved.

[0080] Figure 3 schematically illustrates a section of the machine 10 according to the first example.

[0081] The machine 10 comprises a casing 46 housing the electromagnetic converters 45, 46.

[0082] The first electromagnetic converter 45 comprises the first set of stator coils 47 connected to the connection terminals 24, 25, 26, a magnetic mass 48 enclosing the rotor shaft 11 and housing the first rotor coil 39.

[0083] The second electromagnetic converter 46 comprises the second set of stator coils 49 connected to the connection terminals 27, 28, 29, a magnetic mass 50 enclosing the rotor shaft 11 and housing the second rotor coil 40.

[0084] The magnetic masses 48, 50 of the electromagnetic converters 45, 46 are mounted in series on the rotor shaft 11.

[0085] The stator coil assemblies 47, 49 form the stator 13, and the rotor shaft 11 and the magnetic masses 48, 50 comprising the rotor coils 39, 40 form the rotor 38.

[0086] The rotor 38 further comprises two sets of supply rings 51, 52.

[0087] A first set of conductive rings 51 comprises two rings 53, 54 arranged on the rotor shaft 11 and connected to the first rotor coil 39.

[0088] Each ring 53, 54 cooperates with a brush 55, 56 different from a first set of brushes of the stator 13.

[0089] The brushes 55, 56 are connected to the supply terminals 41, 42 to supply the first rotor coil 39.

[0090] The second set of rings 52 comprises two rings 57, 58 arranged on the rotor shaft 11 and connected to the second rotor coil 40.

[0091] Each ring 57, 58 cooperates with a brush 59, 60 different from a second set of brushes of the stator 13. The brushes 59, 60 are connected to the power supply terminals 43, 44 to power the second rotor coil 40.

[0092] Figure 4 illustrates an electrical diagram of a second example of the machine 10 and the control means 12.

[0093] We find the first and second power converters 14, 15.

[0094] The machine 10 comprises a stator 61 comprising a first set of stator coils and a second set of stator coils (not shown in this figure).

[0095] The coils of the first set of stator coils form three first phases coupled for example in star or delta, each phase having the same number of poles.

[0096] The coils of the second set of stator coils form three second phases coupled for example in star or delta, each phase having the same number of poles as the phases formed by the first set of coils.

[0097] Each set of coils is powered by a different reversible 14, 15 power converter.

[0098] The output terminals 180, 190, 200 of a first converter 14 are each connected to a terminal 62, 63, 64 for connecting a different first phase, and the output terminals 210, 220, 230 of the second converter 15 are each connected to a terminal 65, 66, 67 for connecting a different second phase.

[0099] The machine 10 further comprises a wound rotor 68 comprising two independent rotor coils 69, 70 each powered by auxiliary power converters 71, 72.

[0100] The auxiliary power converters 71, 72 are produced from switching cells 35, 36 and comprise input terminals 73, 74, 75, 76.

[0101] The power supply terminals 73, 74 of a first auxiliary power converter 71 are connected to the third network R3 and the power supply terminals 75, 76 of a second auxiliary power converter 72 are connected to the fourth network R4. The control means 12 comprise the first and second converters 14, 15, the first and second auxiliary converters 71, 72, and control means 250 controlling the gate of the transistors of the first and second converters 14, 15 and of the first and second auxiliary converters 71, 72 so that the machine 10 delivers a mechanical torque to the rotor shaft 11 or generates electrical power at its terminals.

[0102] The control means 250 are produced for example from a controller.

[0103] Figure 5 schematically illustrates a radial section of the second example of the machine 10.

[0104] The machine 10 comprises a casing 80 in which the stator 61 and the rotor 68 are housed.

[0105] The stator 61 comprises two identical stator magnetic half-masses 81, 82 extending in a longitudinal direction of the stator 61, and connected together to form the stator 61.

[0106] The first set of stator coils is inserted into a first stator magnetic half-mass 81 and comprises nine coils 83 to 91 inserted between stator teeth of said stator half-mass, extending in a longitudinal direction of the stator and forming three poles per phase.

[0107] A first phase of the first stator half-mass 81 comprises the coils 83, 86 and 89 and is powered by the connection terminal 62, a second phase of the first stator half-mass 81 comprises the coils 84, 87 and 90 and is powered by the connection terminal 63, and the third phase of the first stator half-mass 81 comprises the coils 85, 88 and 81 and is powered by the connection terminal 64.

[0108] The second set of stator coils is inserted into the second stator magnetic half-mass 82 and comprises nine coils 92 to 100 inserted between stator teeth of said stator half-mass, extending in a longitudinal direction of the stator and forming three poles per phase. A first phase of the second stator half-mass 82 comprises the coils 92, 95, 98 and is powered by the connection terminal 65, a second phase of the second stator half-mass 82 comprises the coils 93, 96 and 99 and is powered by the connection terminal 66, and the third phase of the second stator half-mass 82 comprises the coils 94, 97, 100 and is powered by the connection terminal 67.

[0109] The windings of the stator half-masses 81, 82 are distributed to optimize the torque distribution in the machine 10 by attenuating torque variations.

[0110] Alternatively, the windings of the stator half-masses 81, 82 are concentric.

[0111] Of course, the first and second sets of stator coils may comprise more than three phases, each phase being able to comprise more than three poles.

[0112] Each pole can further be formed by several stator coils.

[0113] The rotor 68 comprises two identical rotor magnetic half-masses 101, 102 extending in a longitudinal direction of the rotor, and fixed on the rotor shaft 11 and between them to form the rotor 68.

[0114] A first rotor magnetic half-mass 101 comprises the first rotor coil 69 wound around rotor pads of the half-mass 101.

[0115] The rotor pads are arranged in the half-mass 101 so that they are perpendicular.

[0116] The turns of the coil 69 arranged on a first pad forming a north pole noted NI and the turns arranged on the second pad forming a south pole noted SI of the first coil 69 are arranged perpendicular to each other.

[0117] The second rotor magnetic half-mass 102 comprises the second rotor coil 70 wound around rotor pads of the half-mass 102. The rotor pads are arranged in the half-mass 102 so that they are perpendicular.

[0118] The turns of the coil 70 arranged on a first pad forming a north pole denoted N2 and the turns arranged on the second pad forming a south pole denoted S2 of the second coil 70 are arranged perpendicular to each other.

[0119] The poles NI, SI, N2, S2 are arranged perpendicular to each other in the double-wound rotor 68.

[0120] The machine 10 further comprises the first and second sets of rings 51, 52 (not shown in this figure) arranged on the rotor shaft 11 and cooperating with the brushes 55, 56, 59, 60 (not shown in this figure) so that the first set of rings 51 powers the first coil 69 from the first auxiliary converter 71, and so that the second set of rings 52 powers the second coil 70 from the second auxiliary converter 72.

[0121] When the two sets of stator windings are functional, the control means 250 control the auxiliary converters 71, 72 so that they each deliver a continuous supply current, and also control the power converters 14, 15 so that the machine 10 delivers a mechanical torque on the rotor shaft 11 or generates electrical power at its terminals 61 to 67 reinjected by the converters 14, 15 into the networks RI, R2 of the helicopter.

[0122] When one of the first and second sets of stator windings is faulty, the control means 250 control the power converter 14, 15 connected to said faulty set of stator coils so that said converter no longer supplies said faulty set and also control the auxiliary converters 71, 72 so that the amplitude of the supply current supplying the rotor coil 69, 70 of a rotor half-mass covering the faulty set of stator coils decreases, so that said current is substantially zero when said rotor half-mass covers the entire faulty set of stator coils, and so that the amplitude of said current increases when said rotor half-mass uncovers the faulty set of stator coils.

[0123] The effective value of the supply current is non-zero.

[0124] The instantaneous value of the magnetic field created in the air gap of the machine 10 between the faulty stator coil assembly and the rotor coils is minimal, thus preventing the propagation of the fault to the functional stator coil assembly.

[0125] In order to prevent the occurrence of an excessively high short-circuit parasitic current in the faulty stator coil assembly induced by the magnetization of the air gap by the rotor winding opposite that in front of the faulty stator winding assembly, dead times can be created.

[0126] Figure 6 illustrates a schematic modeling of the second example of the machine 10 illustrated in Figure 5.

[0127] We find the two identical stator magnetic half-masses 81, 82 and the two rotor coils 69, 70 supplied respectively by the supply current II and the supply current 12.

[0128] A reference frame is defined comprising an origin located at the center of the rotor shaft 11, a first fixed X axis and a second Y axis passing through the center of the rotor coils 69, 70 and defining an angle α with the first X axis.

[0129] It is assumed that the first stator half-mass 81 extends from 0 to n along the first axis X, and the second stator half-mass 82 extends from n to 0 along the first axis X.

[0130] Figure 7 illustrates the evolution of the sinusoidal supply currents II, 12 delivered by the auxiliary power converters when the first set of stator coils integrated in the first half-mass 81 is faulty.

[0131] Figure 8 illustrates an example of an aircraft 200 of the CTOL type, for example a twin-engine aircraft comprising two identical propulsion devices 201 arranged on either side of a longitudinal axis of the aircraft. Each propulsion device 201 comprises a propeller 202 and a machine 10 as previously described in figures 2 to 5, and the control means 12 connected to the machine 10.

[0132] The rotor shaft 11 is connected to the propeller 10 so that the propeller rotated by the engine 10 propels the aircraft.

Claims

DEMANDS 1. Synchronous electric machine (10) for aircraft (1, 200), comprising a stator (13, 61) and a wound rotor (38, 68) inserted in the stator, the stator comprising two sets of stator coils (47, 49, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100) intended to be connected to different power converters (14, 15), and the wound rotor comprising a rotor shaft (11) and two rotor coils (39, 40, 69, 70) each intended to be supplied by a different supply current (11, 12), characterized in that the two sets stator coils are arranged in the stator such that when a first set of stator coils (47) fails, the second set of stator coils (49) cooperates with at least the second rotor coil (40,70) powered by the associated supply current (12) to generate electrical energy across the terminals of the second set of stator coils or to generate mechanical torque on the rotor shaft, and such that the power converter connected to the first set of stator coils does not deliver electrical power.

2. Electric machine according to claim 1, in which the two rotor coils (39, 40) are arranged in series on the rotor shaft (11), the first set of stator coils (47) and the second set of stator coils (49) being arranged in the stator such that the first rotor coil and the first set of stator coils form a first electromagnetic converter, and such that the second rotor coil and the second set of stator coils form a second electromagnetic converter.

3. Electric machine according to claim 1, in which the rotor (68) comprises two identical rotor magnetic half-masses (101, 102) extending along a longitudinal direction of the rotor and the stator (61) comprises two identical stator magnetic half-masses (81, 82) extending along a longitudinal direction of the stator, each rotor coil being inserted into a different rotor magnetic half-mass and each set of stator coils being inserted into a different stator magnetic half-mass.

4. Electric machine according to any one of claims 1 to 3, wherein the rotor (38, 68) comprises two sets of feed rings (51, 52), each set being connected to a different rotor coil (39, 40, 69, 70), and wherein the stator comprises two sets of brushes (55, 56, 59, 60) each feeding a different set of rings, each set of brushes being intended to be connected to one of the second power converters.

5. Propulsion device (201) for aircraft (200) comprising an electric machine (10) according to any one of claims 1 to 4, and a propulsion propeller (202) connected to the rotor shaft (11).

6. Hybrid turboshaft engine (5) for aircraft (1) comprising an electric machine (10) according to any one of claims 1 to 4 and a turboshaft engine comprising a free gas turbine (9), the free turbine being further connected to the rotor shaft (11) of the electric machine.

7. Aircraft (1, 200) comprising a propulsion device (201) according to claim 5 or a hybrid turboshaft engine (5) according to claim 6.

8. Method for controlling a synchronous electric machine (10) for an aircraft (1, 200), the electric machine comprising a stator (13, 61) and a wound rotor (38, 68) inserted in the stator, the stator comprising two sets of stator coils (47, 49, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100) connected to different power converters (14, 15), and the wound rotor comprising a rotor shaft (11) and two rotor coils (39, 40, 69, 70) each supplied by a different supply current (11, 12), characterized in that the The method includes deactivating the first faulty set of stator coils (47, 83, 84, 85, 86, 87, 88, 89, 90, 91) by controlling the power converter (14) connected to said first set so that said converter does not deliver electrical power to said set of coils, a power supply electrical of the second set of stator coils (49, 92, 93, 94, 95, 96, 97, 98, 99, 100) by the associated power converter (15), and at least one supply of the second rotor coil (40, 70) by the associated supply current (12) to generate mechanical torque on the rotor shaft (11) or the generation of electrical power at the terminals of the second set of stator coils.

9. A method according to claim 8, the rotor (68) comprising two identical rotor magnetic half-masses (101, 102) extending along a longitudinal direction of the rotor and the stator (61) comprising two identical stator magnetic half-masses (81, 82) extending along a longitudinal direction of the stator, each rotor coil (69, 70) being inserted in a different rotor magnetic half-mass and each set of stator coils being inserted in a different stator magnetic half-mass, the method comprising controlling the supply currents (II, 12) such that the amplitude of the supply current supplying the rotor coil of a rotor half-mass covering the first set of stator coils decreases, such that said current is substantially zero when said rotor half-mass covers the entire first set of stator coils,and such that the amplitude of said current increases when said rotor half-mass uncovers the first set of stator coils, the RMS value of said current being non-zero.

10. Method according to claim 9, wherein each supply current (II, 12) is sinusoidal.

Images