Aircraft turbomachine and its in-flight restart method

Abstract

An aircraft turbomachine comprising an electric restart machine (ME2) configured to drive a high-pressure shaft (22) in rotation from an alternating restart current (CA2) supplied by an electrical power supply system (3) comprising: - an electric generator (ME1) of an alternating supply current (CA1) by taking torque from a low-pressure shaft, - an electrical rectifier (31) connected to the electric generator (ME1), - an electrical converter (32) connected to the electric restart machine (ME2), - an electrical switching device (33) configured to prohibit the flow of current between the electrical rectifier (31) and the electrical converter (32) in an open state and to permit it in a closed state (F1),a control device (4) being configured to control the closed state (F1) and to activate an electrical power modulation device (D) of the restart alternating current (CA2) during an in-flight restart. Abstract figure: Figure 4,

Description

Title of the invention: Aircraft turbomachine and its method for restarting in flight. Technical field

[0001] The present invention relates to the in-flight restart of an aircraft turbomachine.

[0002] Climate change is a major concern for many legislative and regulatory bodies worldwide. 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 to those currently in service, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been mobilizing for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors that impact all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have moderate environmental impacts, with the aim of improving the energy efficiency of aircraft. Consequently, the Applicant is constantly working to reduce its climate impact by employing methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0004] This sustained research and development work focuses in particular on new generations of aircraft engines, aircraft weight reduction, notably through the materials used and lighter onboard equipment, and aviation biofuels. Finally, this work focuses on developing the use of electrical technologies for propulsion, including electric machines for injecting or drawing power from the rotating components of engines.

[0005] In a known manner and with reference to [Fig. 1], a turbomachine 100 of the twin-spool turbojet type comprises, from upstream to downstream in the direction of gas flow, a propulsion unit 110, a low-pressure compressor 111, a high-pressure compressor 112, a combustion chamber 113, a high-pressure turbine 114, a low-pressure turbine 115 and an exhaust nozzle 116. The rotation The low-pressure turbine 115 drives, via a low-pressure shaft 121, the low-pressure compressor 111 and the propulsion unit 110. A reduction gear (not shown) can be conventionally integrated to reduce the rotational speed transmitted by the low-pressure turbine 115 to the propulsion unit 110. The high-pressure turbine 114 drives the high-pressure compressor 112 via a high-pressure shaft 122.

[0006] In the event of an in-flight shutdown of the turbomachine 100, caused for example by environmental disturbances such as bird strikes, the turbomachine must be able to be restarted independently of the aircraft's power sources, within a certified restart range characterized by a maximum altitude of approximately 30,000 feet and a minimum speed of approximately 230 knots. The restart must ensure the following functions: fuel injection into the combustion chamber, power supply to the control units, power supply to the spark plugs, and preferably control of the blade pitch in a position facilitating restarting, particularly on turbomachines with a linked turbine.

[0007] A conventional descent phase is thus carried out by the aircraft from its cruising altitude of approximately 40,000 feet, during which the low-pressure shaft 121 and the high-pressure shaft 122 unscrew until they stabilize in an autorotation regime, known in English as "windmilling". In the autorotation regime, the low-pressure shaft 121 and the high-pressure shaft 122 are driven at low speed, solely by the action of the wind.

[0008] As is known, restarting the turbomachine 100 can be assisted by an electric starter ME mounted in the accessory gearbox, known as the "Accessory Gear Box (AGB)". The electric starter ME is electrically powered by drawing power from the other turbomachines of the aircraft, via the aircraft's electrical network, and is configured to inject torque onto the high-pressure shaft 122 in this example, or onto the low-pressure shaft 121. However, such a restart is not functional during an in-flight shutdown of all the turbomachines 100 ("total engine flame out").

[0009] In practice, restarting can also be prevented by a high-pressure shaft 122 blockage phenomenon known as "corelock," which can occur, in particular, during the aircraft's descent phase. During this phase, the temperature of the turbomachine 100 casing decreases more rapidly than that of the high-pressure compressor rotor 112, resulting in a difference in the thermal expansion of the materials and potentially blocking the rotation of the rotor blades due to friction against the casing. To avoid this phenomenon, one solution is to maintain the high-pressure shaft 122 at a sufficient rotational speed to force wear of the casing's abradable surface by the high-pressure compressor rotor blades. pressure 112 and thus ensure their rotation. This also requires a power supply via the aircraft's electrical network, which is not functional during an in-flight shutdown of all 100 turbomachines.

[0010] Furthermore, the autorotation of the turbomachine 100 does not allow the lubrication system to be driven, which can cause damage. To remedy this, it is known to use an auxiliary pump powered electrically via the aircraft's electrical network, which presents the same drawback as before and adds the mass of the turbomachine.

[0011] The invention thus aims at restarting an aircraft turbomachine in flight, in particular in the event of a stoppage in flight of all the aircraft's turbomachines. PRESENTATION OF THE INVENTION

[0012] The invention relates to an aircraft turbomachine comprising a low-pressure shaft, a high-pressure shaft and an electric restart machine configured, when powered by an alternating restart current, to drive the high-pressure shaft into rotation.

[0013] The invention is remarkable in that the aircraft turbomachine comprises: • a power supply system for the restarting electric machine comprising: • an electric generator configured to produce an alternating current supply by drawing rotary torque from the low-pressure shaft, • an electrical rectifier connected to the electrical generator and configured to provide direct current from the alternating current supply, • an electrical converter configured to supply the restart alternating current to the restarting electrical machine from the direct current, • an electrical switching device configured, in an open state, to prohibit the flow of direct current between the electrical rectifier and the electrical converter, and in a closed state, to allow the flow of direct current between the electrical rectifier and the electrical converter, • an electrical power modulation device configured to modulate the restart alternating current from at least one modulation setpoint, and • a control device configured, during an in-flight restart of the aircraft turbomachine, to control the closed state of the device switching and issuing the modulation command, so that the restart electric machine drives the high-pressure shaft into rotation.

[0014] The invention advantageously allows torque to be injected onto the high-pressure shaft to facilitate the restart of a turbomachine in flight, by drawing power from the low-pressure shaft. The turbomachine can thus restart autonomously and independently, in particular without drawing power from the aircraft's electrical system or from another turbomachine. The invention is particularly well-suited for use during an in-flight shutdown of any turbomachine, where the aircraft's electrical system is unavailable.

[0015] The method according to the invention is thus particularly suited to a situation of in-flight shutdown of all the aircraft's turbomachines ("total engine flame out"), in that it allows an autonomous and independent restart of the turbomachine, preferably only by drawing power from the low-pressure shaft.

[0016] Preferably, the modulation setpoint is a function of a measurement of the rotational speed of the high-pressure shaft. Thanks to the electrical power modulation device, it is possible to drive the restarting electric machine according to two or more distinct operating modes. This makes it possible to adapt the power supplied according to the requirements during a restart.

[0017] According to one aspect of the invention, the aircraft turbomachine comprises a lubrication device coupled to the electric restart machine, the electrical power modulation device having at least: • a low transmission state suitable for driving the lubrication device, • a high transmission state suitable for driving the high-pressure shaft.

[0018] Advantageously, a low transmission state is controlled during the transient phase when the aircraft is entering restart conditions, particularly during the autorotation regime of the aircraft turbomachine, known as "windmilling," and then a high transmission state is controlled for the restart phase. This ensures continued lubrication of the turbomachine during the transient phase and prevents the occurrence of a high-pressure shaft blockage in the turbomachine.

[0019] According to one aspect of the invention: • The power supply system includes at least one low electrical resistance and one high electrical resistance connected in parallel between the electrical rectifier and the electrical converter, together forming the electrical power modulation device, and • The switching device includes a first closed state, in which the direct current is modulated by the low electrical resistance, and a second closed state, in which the direct current is modulated by the high electrical resistance.

[0020] Such a binary electrical power modulation device is advantageously uncomplicated, therefore inexpensive and easy to control.

[0021] According to one aspect of the invention, the power supply system comprises at least one variable resistor mounted between the electrical rectifier and the electrical converter, forming the electrical power modulation device. Such an electrical power modulation device makes it possible to adapt the power transmission according to requirements, in a simple and practical manner.

[0022] According to one aspect of the invention, the electrical converter is configured to provide a restart alternating current with a frequency controllable by the control device and forms the electrical power modulation device. Such a solution is advantageously compact. This facilitates integration into the aircraft turbomachine.

[0023] According to one aspect of the invention, the electric generator is a wound-rotor synchronous type and forms the electrical power modulation device, the control device being configured to control the magnetic excitation of the wound rotor of the electric generator. Such a solution is advantageously compact. This facilitates integration into the aircraft turbomachine.

[0024] According to one aspect of the invention, the control device is configured to control the closed state of the switching device when a measurement of the rotational speed of the low-pressure shaft is below a predetermined threshold.

[0025] The invention also relates to a method for restarting an aircraft turbomachine as described above in flight, wherein the switching device is initially in the open state and, during an in-flight restart of the aircraft turbomachine: • The control device controls the closed state of the switching device, • the control device provides at least one modulation setpoint to the electrical power modulation device, then • The electric restart machine drives the high-pressure shaft into rotation from the restart alternating current supplied by the power supply system.

[0026] According to one aspect of the invention, the aircraft turbomachine comprises a lubrication device coupled to the electric restart machine and the control device provides: • A first instruction to modulate a low transmission state of the electrical power modulation device adapted for driving the lubrication device, then • A second modulation instruction for a high transmission state of the electrical power modulation device adapted for driving the high-pressure shaft,

[0027] The high transmission state is preferably operated when the aircraft is at an altitude of 30,000 feet or less and allows the turbomachine to be restarted. The low transmission state is activated during the preparatory phase of the restart to maintain sufficient lubrication and prevent the high-pressure shaft from seizing. PRESENTATION OF THE FIGURES

[0028] The invention will be better understood upon reading the following description, 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.

[0029] Fig. 1 is a schematic representation of an aircraft turbomachine according to the prior art.

[0030] Fig. 2 is a schematic representation of an aircraft turbomachine according to one embodiment of the invention.

[0031] Fig. 3 is a schematic representation of a first embodiment of the invention with an open-state switching device and an electrical power modulation device in the form of a low resistance and a high resistance mounted in parallel.

[0032] Fig. 4 is a schematic representation of the first embodiment of Fig. 3 with the switching device in a first closed state.

[0033] Fig. 5 is a schematic representation of the first embodiment of Fig. 3 with the switching device in a second closed state.

[0034] Fig. 6 is a schematic representation of a second embodiment of the invention, in which a variable resistor forms the electrical power modulation device.

[0035] Fig. 7 is a schematic representation of a third embodiment of the invention, in which the electrical converter forms the electrical power modulation device.

[0036] Fig. 8 is a schematic representation of a fourth embodiment of the invention, in which the electric generator forms the electrical power modulation device.

[0037] Fig. 9 is a schematic representation of an in-flight restart method according to one embodiment of the invention.

[0038] It should be noted that the figures set out the invention in detail to implement the invention, said figures being of course able to serve to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0039] With reference to [Fig. 2], the invention relates to a twin-spool aircraft turbomachine T conventionally comprising, from upstream to downstream in the direction of gas flow, a propulsion unit 10 (fan or propeller), a low-pressure compressor 11, a high-pressure compressor 12, a combustion chamber 13, a high-pressure turbine 14, a low-pressure turbine 15, and an exhaust nozzle 16. The rotation of the low-pressure turbine 15 drives, via a low-pressure shaft 21, the low-pressure compressor 11 and the propulsion unit 10. A reduction gear (not shown) conventionally reduces the rotational speed transmitted by the low-pressure turbine 15 to the propulsion unit 10. The high-pressure turbine 14 drives the high-pressure compressor 12 via a high-pressure shaft 22.

[0040] According to the invention and as illustrated in Figures 2 and 3, the aircraft turbomachine T also comprises: • an electric restart machine ME2 coupled to the high-pressure shaft 22 and configured, when powered by a restart alternating current CA2, to drive the high-pressure shaft 22 in rotation, • a power supply system 3 for the ME2 electric restart machine comprising: • an electric generator ME1 coupled to the low-pressure shaft 21 and configured to produce an alternating current supply CAI by drawing a rotary torque from the low-pressure shaft 21, • an electric rectifier 31 electrically connected to the electric generator ME1 and configured to supply a direct current DC from the alternating current supply CAI, • an electrical converter 32 electrically connected to the ME2 restart electric machine and configured to supply the AC restart current CA2 to the ME2 restart electric machine from the DC direct current, • an electrical switching device 33 electrically connecting the electrical rectifier 31 and the electrical converter 32 and configured, in an open state O, to prohibit the DC current flow between the electrical rectifier 31 and the electrical converter 32, and in a closed state Fl, F2 (see figures 4 and 5), to allow the DC current flow between the electrical rectifier 31 and the electrical converter 32, and • an electrical power modulation device D configured to modulate the restart alternating current CA2 from one or more modulation setpoints, and • a control device 4 configured, during an in-flight restart of the aircraft turbomachine T, to control the closed state Fl, F2 (see figures 4 and 5) of the switching device 33 and to issue the modulation command(s), so that the electric restart machine ME2 drives the high-pressure shaft 22 in rotation.

[0041] The invention advantageously allows a mechanical torque R to be injected onto the high-pressure shaft 22 in order to facilitate the restart of the aircraft turbomachine T following a stop in flight, caused for example by environmental disturbances such as the ingestion of birds.

[0042] The invention is particularly advantageous in that the electrical power supply for the ME2 restarting electric machine is provided by drawing mechanical power from the low-pressure shaft 21, thus enabling an autonomous and independent restart of the turbomachine T, without drawing power from the aircraft's electrical network RA. The sizing of certain equipment, such as the fuel supply system, can advantageously be reduced. The invention is particularly suited to a situation involving the in-flight shutdown of all the aircraft's turbomachines, known to those skilled in the art as "total engine flameout."

[0043] According to a preferred aspect illustrated in [Fig.3], the electric restart machine ME2 is also electrically connected to the aircraft RA electrical network, in this example by electrical connection to the terminals of the switching device 33. This allows the power taken from the low pressure shaft 21 to be injected into the aircraft RA electrical network and conversely, the electric restart machine ME2 to be electrically supplied with power from the aircraft RA electrical network.

[0044] As illustrated in [Fig. 3], the electrical rectifier 31 and the electrical converter 32 enable the transfer of power from the electric generator ME1 to the restarting electric machine ME2 despite their difference in rotational speed. The switching device 33 allows or prevents the power transfer and is controlled by a switching signal SI from the control device 4, which may be, for example, a computer. of the aircraft. The closed state Fl, F2 is preferably triggered when the speed M of the low pressure shaft 21 decreases below a threshold value, for example measured by a speed sensor 5. Other parameters can be checked, such as the absence of fire or the altitude of the aircraft.

[0045] According to a preferred aspect illustrated in [Fig.3], the electrical power modulation device D comprises two modulation states, namely a low transmission state suitable for driving the lubrication device 8 of the turbomachine T and a high transmission state suitable for driving the high-pressure shaft 22.

[0046] In practice, the high transmission state is suitable for restarting the turbomachine T, while the low transmission state is suitable for a transient phase following the shutdown of the turbomachine T and preceding the restart. The low transmission state is particularly sufficient to drive the aircraft turbomachine in an autorotation regime known as "windmilling." The high transmission state allows the high-pressure shaft 22 to be driven at a sufficient rotational speed for restarting and thus for fuel injection. The high transmission state also allows the lubrication device 8 to be driven.

[0047] During the transitional phase, the aircraft enters a certified restart range with conditions conducive to restarting, namely a maximum altitude of approximately 30,000 feet and a minimum speed of approximately 230 knots. This transitional phase typically takes the form of a descent from its cruising altitude of approximately 40,000 feet, during which the low-pressure shaft 21 and the high-pressure shaft 22 unscrew until they stabilize in autorotation. The low transmission state of the electrical power modulation device D advantageously allows the electric restart machine ME2 to supply torque R' to the lubrication device 8 during this phase to continue lubricating the turbomachine T.

[0048] The low transmission state also makes it possible to maintain a minimum rotational speed of the high-pressure shaft 22, which prevents the occurrence of a blockage phenomenon of the high-pressure shaft 22, known in English as "corelock", caused by a difference in thermal expansion of the materials which can block the rotation of the blades.

[0049] The ME2 electric restart machine is, for example, mounted in the accessory relay box of the turbomachine T (not shown). The ME1 electric generator is, for example, mounted in the inter-core compartment. The ME1 electric generator is, for example, mechanically coupled to the low-pressure shaft 21 downstream of the chamber combustion 13 and upstream of the low pressure turbine 15. The ME2 electric restart machine and the ME1 electric generator are, for example, in the form of permanent magnet or wound rotor synchronous machines.

[0050] According to a first embodiment of the invention illustrated in Figures 3 to 5, the power supply system 3 comprises a low electrical resistance 34 and a high electrical resistance 35 connected in parallel between the electrical rectifier 31 and the electrical converter 32, together forming the electrical power modulation device D. Preferably, the low electrical resistance 34 has an electrical resistance between 500 Ohms and 10,000 Ohms. The high electrical resistance 35 is greater than the low electrical resistance 34 and preferably between 1,000 Ohms and 10,000 Ohms.

[0051] In this example, the power supply system 3 also includes a first switch 331 mounted on the branch of the low electrical resistance 34, and a second switch 332 mounted on the branch of the high electrical resistance 35. These two switches together form the switching device 33. The switching device 33 could have been in another form, for example a switch selecting one or neither of the parallel branches on which the electrical resistances 34, 35 are arranged.

[0052] With reference to [Fig. 3], the switching device 33 includes an open state O in which both switches 331, 332 are open. No direct current then flows between the electrical rectifier 31 and the electrical converter 32, and no restart alternating current CA2 is then transmitted to the restart electrical machine ME2. The open state O is suitable for normal in-flight operation of the aircraft turbomachine T, characterized, for example, by a measurement M of the rotational speed of the low-pressure shaft 21 exceeding a predetermined threshold.

[0053] With reference to [Fig.4], the switching device 33 includes a first closed state Fl, in which the DC current is modulated by the low electrical resistance 34. The DC current flowing between the electrical rectifier 31 and the electrical converter 32 is then high, and the restart alternating current CA2 supplied by the electrical converter 32 to the restart electrical machine ME2 is sufficient to drive the high-pressure shaft 22 to a restart speed of the aircraft turbomachine T.

[0054] With reference to [Fig. 5], the switching device 33 includes a second closed state F2, in which the DC current is modulated by the high electrical resistance 35. The DC current flowing between the electrical rectifier 31 and the electrical converter 32 is then lower than in the first closed state F1, and the restart AC current CA2 supplied by the electrical converter 32 to the restart electrical machine ME2 is sufficient to power the device lubrication 8 and to drive the high-pressure shaft 22 at a minimum speed to avoid the occurrence of the high-pressure shaft 22 blocking phenomenon.

[0055] In the first embodiment of figures 3 to 5, the control of switches 331 and 332 ensures both the switching from the open state O to a closed state Fl, F2 and the modulation between a low transmission state (first closed state Fl) and a high transmission state (second closed state F2).

[0056] According to a second embodiment illustrated in [Fig.6], the power supply system 3 comprises a variable resistor 36 mounted between the electrical rectifier 31 and the electrical converter 32, as well as a switch forming the switching device 33. The variable resistor 36 forms the electrical power modulation device D and allows the direct current DC, and therefore the restart alternating current CA2, to be modulated.

[0057] As illustrated in [Fig. 6], the variable resistor 36 is configured, based on the modulation signal S2, to select an electrical resistance value within a predetermined range, preferably between 500 Ohms and 10,000 Ohms. This range of variation advantageously allows the power supply system 3 to provide a restart AC current CA2 whose value is adapted depending on whether a low or high transmission state is desired.

[0058] According to a third embodiment illustrated in [Fig. 7], the electrical power modulation device D is formed by the electrical converter 32, whose output frequency of the restart AC current CA2 is controllable via the modulation signal S2. The switching device 33 is in the form of a switch. Preferably, the control device 4 determines the modulation signal S2 from a measurement M' of the rotational speed of the high-pressure shaft 22, measured, for example, by a high-pressure rotational speed sensor 6.

[0059] Controlling the frequency of the restart alternating current CA2 advantageously allows control of the slip of the restart electric motor ME2, so as to precisely control the power transferred from the low pressure shaft 21 to the high pressure shaft 22. This makes it possible to adapt the power transferred according to whether a low transmission state or a high transmission state is desired.

[0060] Alternatively, the electrical power modulation device D takes the form of the electrical rectifier 31, which is then in the form of an electrical converter, that is to say, a device comprising a three-phase voltage rectifier with transistor control on each of the diode branches. The duty cycle of the transistors in the rectifier is then controlled so as to vary the AC supply current CAI, and thus indirectly the AC restart current CA2.

[0061] According to a fourth embodiment illustrated in [Fig. 8], the electric generator ME1 is preferably of the wound-rotor synchronous type and forms the electrical power modulation device D. The switching device 33 is in the form of a switch. The control device 4 is configured to control the magnetic excitation of the wound rotor of the electric generator ME1 via the modulation signal S2. Controlling the magnetic excitation of the wound rotor of the electric generator ME1 allows control of the AC supply current CAI generated by the electric generator ME1, and thus modulates the DC current DC and therefore the AC restart current CA2.

[0062] The control of the magnetic excitation of the wound rotor of the electric generator ME1 is preferably achieved by controlling the induction in the electric generator ME1. Preferably, the control device 4 determines the modulation signal S2 from a measurement M' of the rotational speed of the high-pressure shaft 22, measured for example by a high-pressure rotational speed sensor 6. Preferably, the control device 4 includes a PID (proportional-integral-derivative) controller configured to control the magnetic excitation of the wound rotor of the electric generator ME1 from a predetermined setpoint or one given by the control computer and from the measurement M'.

[0063] With reference to [Fig. 9], the invention also relates to a method for restarting an aircraft turbomachine T (preferably corresponding to the turbomachine described above) in flight following an in-flight shutdown, caused, for example, by environmental disturbances such as bird strikes. As illustrated in [Fig. 9], the switching device 33 is initially in the open state O and the control device 4 controls the closed state F of the switching device 33 and provides E2 one or more modulation commands S2 to the electrical power modulation device D.

[0064] The method is implemented in practice during a transient phase following the shutdown of the turbomachine T and preceding its restart, specifically during the autorotation of the turbomachine T, during which the aircraft descends to reach a certified restart range. During such a phase, the low-pressure shaft 21 and the high-pressure shaft 22 unscrew until they stabilize in an autorotation regime. With the low-pressure shaft 21 rotating at a speed below the predetermined threshold Mrefl, the control device 4 determines a switching signal SI to switch the switching device 33 to a closed state F, Fl, F2, and preferably a first modulation signal S2 to command a low transmission state to the power modulation device D. This allows, from of the ME2 electric restart machine, to provide a torque R' to the lubrication device 8 to continue to ensure the lubrication of the turbomachine T.

[0065] When the aircraft reaches an altitude suitable for restarting the aircraft turbomachine T, the control device 4 provides a second modulation signal S2 to the power modulation device D to control the high transmission state. This allows the electric restart machine ME2 to be driven at a speed sufficient to provide a torque R to the high-pressure shaft 22 suitable for restarting.

[0066] When the restart of the aircraft turbomachine T is completed, for example when the low-pressure shaft speed is greater than a second predetermined threshold Mref2, the control device 4 commands El' the open state O of the switching device 33, so as to stop the drive of the electric restart machine ME2.

[0067] The method according to the invention is particularly suited to a situation of in-flight shutdown of all the aircraft's turbomachines ("total engine flame out"), in that it allows an autonomous and independent restart of the turbomachine T solely by drawing power from the low-pressure shaft 21.

Claims

Demands

1. Aircraft turbomachine (T) comprising a low-pressure shaft (21), a high-pressure shaft (22) and an electric restart machine (ME2) configured, when powered by an alternating restart current (CA2), to rotate the high-pressure shaft (22), the aircraft turbomachine (T) comprising a lubrication device (8) coupled to the electric restart machine (ME2), the aircraft turbomachine (T) being characterized in that it comprises: a power supply system (3) for the electric restart machine (ME2) comprising: • an electric generator (ME1) configured to produce an alternating current supply (ACS) by drawing a rotary torque from the low-pressure shaft (21), • an electrical rectifier (31) connected to the electrical generator (ME1) and configured to supply direct current (DC) from the alternating current supply (ACS), • an electrical converter (32) configured to supply the restart alternating current (AC2) to the restart electrical machine (ME2) from the direct current (DC), • an electrical switching device (33) configured, in an open state (O), to prohibit the flow of direct current (DC) between the electrical rectifier (31) and the electrical converter (32), and in a closed state (F, Fl, F2), to permit the flow of direct current (DC) between the electrical rectifier (31) and the electrical converter (32), and • an electrical power modulation device (D) configured to modulate the restart alternating current (AC2) from at least one modulation setpoint (S2), the electrical power modulation device (D) having at least one transmission state low suitable for driving the lubrication device (8), and a high transmission state suitable for driving the high pressure shaft (22), • a control device (4) configured, during an in-flight restart of the aircraft turbomachine (T), to command the closed state (F, Fl, F2) of the switching device (33) and issue the modulation setpoint (S2), so that the electric restart machine (ME2) drives the high pressure shaft (22) in rotation.

2. Aircraft turbomachine (T) according to claim 1, wherein the modulation setpoint (S2) is a function of a measurement (M') of the rotational speed of the high-pressure shaft (22).

3. Aircraft turbomachine (T) according to any one of claims 1 and 2, wherein: • the power supply system (3) comprises at least one low electrical resistance (34) and one high electrical resistance (35) mounted in parallel between the electrical rectifier (31) and the electrical converter (32) and together forming the electrical power modulation device (D), and • the switching device (33) comprises a first closed state (F1), in which the direct current (DC) is modulated by the low electrical resistance (34), and a second closed state (F2), in which the direct current (DC) is modulated by the high electrical resistance (35).

4. Aircraft turbomachine (T) according to any one of claims 1 and 2, wherein the power supply system (3) comprises at least one variable resistor (36) mounted between the electrical rectifier (31) and the electrical converter (32) and forming the electrical power modulation device (D).

5. Aircraft turbomachine (T) according to any one of claims 1 and 2, wherein the electrical converter (32) is configured to provide a restart alternating current (AC2), of frequency controllable by the control device (4), and forms the electrical power modulation device (D).

6. Aircraft turbomachine (T) according to any one of claims 1 and 2, wherein the electric generator (ME1) is of the wound-rotor synchronous type and forms the electric power modulation device (D), the control device (4) being configured to control the magnetic excitation of the wound rotor of the electric generator (ME1).

7. Aircraft turbomachine (T) according to any one of claims 1 to 6, wherein the control device (4) is configured to control the closed state (F, Fl, F2) of the switching device (33) when a measurement (M) of the rotational speed of the low-pressure shaft (21) is less than a predetermined threshold (Mrefl).

8. A method for restarting an aircraft turbomachine (T) in flight according to any one of claims 1 to 7, wherein the switching device (33) is initially in the open state (0) and, during an in-flight restart of the aircraft turbomachine (T): • the control device (4) controls (E1) the closed state (F) of the switching device (33), • the control device (4) provides (E2): • the first modulation command (S2) from the low transmission state to the electrical power modulation device (D) adapted for driving the lubrication device (8), then • the second modulation command (S2) from the high transmission state to the electrical power modulation device (D) adapted for driving the high-pressure shaft (22),• The electric restart machine (ME2) drives the high-pressure shaft (22) in rotation using the restart alternating current (CA2) supplied by the power supply system (3).

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