Alternator with voltage doubler circuit

Abstract

The invention relates to a power supply system configured to supply power to a load, comprising an electrical generator (4) comprising a rotor (6) and a stator (8) comprising three windings (10a, 10b, 10c) each comprising a first end (P1, P2, P3) and a second end (N1, N2, N3), the power supply system comprising a matching circuit (1) in parallel with a load (2) and comprising three rectifier circuits (30a, 30b, 30c) in series, each comprising in parallel a first branch (31a, 31b, 31c) coupled to a first end (P1, P2, P3) and a second branch (32a, 32b, 32c) coupled to a second end (N1, N2, N3), the matching circuit (1) being configured to switch from a first operating mode in which only the first branch (31a, 31b, 31c) is conducting, to a second operating mode in which the first branch (31a, 31b, 31c) and the second branch (32a, 32b, 32c) are conducting.

Description

[0001] Alternator with voltage doubler circuit

[0002] DOMAIN

[0003] The present invention relates to the field of electric generators and power conversion circuits, and more specifically relates to an electric generator provided with a circuit making it possible to choose as output voltage between a nominal rectified voltage or a voltage twice the nominal rectified voltage. Such a device can particularly find application in aeronautics, for turbine engines having an electric generator driven by a motor shaft.

[0004] STATE OF THE ART

[0005] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various carbon emission restrictions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new aircraft types and those currently in operation, requiring the implementation of technological solutions to comply with current regulations. Civil aviation has been mobilizing for several years now to contribute to the fight against climate change.

[0006] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental impacts with the aim of improving the energy efficiency of these aircraft.

[0007] Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0008] This ongoing research and development work focuses on new generations of aircraft turbomachines, lighter aircraft, particularly through the materials used and lighter onboard equipment, the development of the use of electrical technologies to provide propulsion, and, as an essential complement to technological progress, aeronautical biofuels. Certain elements of an aircraft require a permanent supply of electricity to ensure continuity of essential services. This electricity can be generated by an electric generator, or alternator, driven by a turbomachine drive shaft. The drive shaft is, for example, connected to a low-pressure turbine, a high-pressure turbine, or any other element rotating during the operation of a turbomachine.However, it may happen that combustion in the turbomachine stops in flight, in which case the electric generator is no longer driven by the combustion of fuel by the turbomachine.

[0009] Even if the turbomachine is stopped, it is necessary for the electric generator to continue producing electricity to at least supply essential services of the turbomachine, such as the power supply of the full-authority digital electronic engine control system, better known by the acronym FADEC for "full-authority digital engine control", or even to provide electrical power to a possible motor pump for fuel metering.

[0010] If the turbomachine stops operating, the electric generator is driven only by the dynamic pressure of the aircraft's forward motion acting on the turbomachine's components, a process known as autorotation or "windmilling" in English.

[0011] The dynamic pressure which drives the motor shafts in autorotation is limited by the following phenomena:

[0012] - at high altitude, the available dynamic pressure is lower as the air density becomes low,

[0013] - at restart altitude (~25000 feet), the aircraft's Mach number is lower, also limiting dynamic pressure,

[0014] - the shaft driving the generator generally drives other equipment (aircraft pumps, lubrication, etc.), which induces torque draws further reducing this autorotation regime.

[0015] Since the rectified voltage obtained from the electric generator depends on the rotational speed of the motor shaft that drives it, this voltage may become too low to provide a power supply that allows the operation of certain electronic components. The electric generator may then be unable to supply essential services of the turbomachine.

[0016] Conventionally known, in particular from US7327113, is a power supply system configured to electrically supply a load comprising a three-phase electric generator configured to be driven in rotation by a motor shaft, the electric generator comprising a rotor and a stator, the stator comprising three windings each corresponding to a phase of the electric generator, each winding comprising a first end and a second end opposite the first end.

[0017] Patent application FR3050083 mentions that power conversion circuits are known from the state of the art, comprising an inverter coupled downstream of a synchronous rectification DC / DC converter, also known in English as PAM for "Pulse Amplitude Modulation", which can be of the voltage step-down (or "buck" in English), voltage step-up (or "boost" in English), or voltage step-down-step-up (or "buck-boost" in English) type.

[0018] However, such voltage-boosting circuits typically use components such as transformers, inductors, and capacitors, and require high-frequency, high-power switches. These requirements can result in complex, bulky, and expensive circuits.

[0019] Therefore, the electric generator is usually oversized to be able to provide sufficient voltage in autorotation mode, and more specifically at restart altitude. As a result, the electric generator is usually heavy, bulky, and provides too high a voltage in normal operation, requiring additional electronic components.

[0020] PRESENTATION OF THE INVENTION

[0021] The aim of the present invention is to make it possible to obtain a sufficient supply voltage from a generator even when the motor shaft driving the generator is rotating at low speed, by limiting the oversizing of the electric generator, in particular in the case of autorotation operation of an aircraft turbomachine, in a compact, simple and economical manner.

[0022] In this regard, there is provided a power supply system configured to electrically supply a load comprising a three-phase electrical generator configured to be rotated by a motor shaft, the electrical generator comprising a rotor and a stator, the stator comprising three windings each corresponding to a phase of the electrical generator, each winding comprising a first end and a second end opposite the first end, wherein the power supply system comprises a matching circuit configured to be connected in parallel to the load and comprising three rectifier circuits coupled in series, each rectifier circuit comprising a first branch and a second branch in parallel with the first branch, the first branch being coupled to the first end of a respective winding, and the second branch being coupled to the second end of said winding,the adaptation circuit being configured to switch from a first operating mode in which only the first branch is conductive and where an output voltage of nominal value is supplied to the load, to a second operating mode in which the first branch and the second branch are conductive and where an output voltage of double the nominal value is supplied to the load.,

[0023] The invention makes it possible to adapt the rectified supply voltage obtained from a three-phase generator in order to enable the power supply at a sufficient voltage even in the event of a decrease in the rotation speed of the voltage generator, while limiting the supply voltage when the electric generator is driven at a higher speed, without requiring complex and expensive or bulky components. It is then possible to use an electric generator with a lower generation capacity, which is less expensive and less bulky.

[0024] The power supply system is advantageously supplemented by the following characteristics, taken alone or in any technically possible combination:

[0025] - for each rectifier circuit:

[0026] • the first branch comprises a first diode and a second diode of the same forward direction and is coupled to the first end of the respective winding between the first diode and the second diode,

[0027] • the second branch comprises a first diode and a second diode of the same forward direction, and a switch between the first diode and the second diode, the second diode being downstream of the first diode in the forward direction, the second branch being coupled to the second end of said winding between the switch and the first diode;

[0028] - in the first operating mode, the switches are blocking, and in the second operating mode, the switches are passing;

[0029] - none of the ends of the stator windings is connected to any other end of the stator windings;

[0030] - each winding extends radially relative to an axis of rotation of the rotor, and the first end of a winding is between the rotor and the second end of said winding;

[0031] - the second ends of the windings of the electric generator would correspond to a neutral phase if said second ends were connected together;

[0032] - the matching circuit comprises a first terminal and a second terminal which are configured to be connected to the load, the three rectifier circuits being connected in series between the first terminal and the second terminal.

[0033] The invention also relates to a turbomachine comprising a motor shaft configured to be driven in rotation during operation of the turbomachine, and a power supply system according to the invention, comprising a three-phase electric generator configured to be driven in rotation by the motor shaft.

[0034] The invention also relates to an aircraft comprising a turbomachine according to the invention, the turbomachine being attached to a wing or to a fuselage of said aircraft.

[0035] The invention also relates to a method for adapting an electrical power supply to a load by a power supply system according to the invention, in which when a condition causing a drop in rotation of the motor shaft or a drop in the output voltage below a voltage threshold is determined, the adaptation circuit switches from a first operating mode in which only the first branch is conductive and where an output voltage of nominal value is supplied to the load, to a second operating mode in which the first branch and the second branch are conductive and where an output voltage of twice the nominal value is supplied to the load.

[0036] PRESENTATION OF FIGURES

[0037] The invention will be better understood from the following description, which relates to a preferred embodiment, given as a non-limiting example and explained with reference to the appended schematic drawings, in which:

[0038] - Figure 1 is a simplified electrical diagram of an electrical power supply system according to a possible embodiment of the invention;

[0039] - Figure 2 shows an example of the voltages across the voltage rectifier circuits and the nominal output voltage when the switches are open according to a possible embodiment of the first operating mode of the invention;

[0040] - Figure 3 shows an example of the phase voltages and the doubling of the nominal output voltage when the switches are on according to a possible embodiment of the second operating mode of the invention;

[0041] - figure 4 shows an example of an aircraft equipped with turbomachines according to a possible embodiment of the invention

[0042] In the various figures, identical numerical references designate similar or equivalent elements.

[0043] DETAILED DESCRIPTION

[0044] With reference to Figure 1, an example of a power supply system 1 configured to electrically supply a load 2 is described. The power supply system 1 may advantageously be part of a turbomachine. The load 2 may in particular be an element of an aircraft, and preferably be an element linked to essential services of a turbomachine, such as the full-authority digital electronic engine control system, better known by the acronym FADEC for "full-authority digital engine control", or even a possible motor pump for fuel metering.

[0045] The power system 1 comprises a three-phase electric generator 4 comprising a rotor 6 configured to be rotated by a motor shaft, and a stator 8. The electric generator 4 is typically a synchronous machine, and more precisely an alternator. The electric generator 4 converts mechanical rotational energy into electrical energy in the form of an alternating electric current.

[0046] The stator 8 comprises three windings 10a, 10b, 10c each corresponding to a phase of a three-phase current. More precisely, the three windings 10a, 10b, 10c are distributed at 120° from each other in a plane orthogonal to the axis of rotation of the rotor, and therefore each deliver a phase current that is 120° out of phase with respect to the other phase currents.

[0047] Each winding 10a, 10b, 10c comprises a first end PI, P2, P3 and a second end NI, N2, N3 opposite the first end PI, P2, P3. Usually, a winding 10a, 10b, 10c is a conductive coil or a solenoid winding around an axis extending radially from the rotor 6, and each winding 10a, 10b, 10c extends radially with respect to the axis of rotation of the rotor 6, and the first end PI, P2, P3 of a winding is between the rotor 6 and the second end NI, N2, N3 of said winding. The first end PI, P2, P3 of a winding is on the side of the rotor 6 and the second end NI, N2, N3 is opposite the rotor 6. Thus, a first winding 10a comprises a first end PI and a second end NI, a second winding 10b comprises a first end P2 and a second end N2, and a third winding 10c comprises a first end P3 and a second end N3.

[0048] This is the non-limiting embodiment which is illustrated and which is described below, but conversely, it would also be possible for the first end to be on the side of the rotor 6, and for the second end to be on the side opposite the rotor 6, in which case it is sufficient to reverse the terms "first end" and "second end" in the remainder of the description.

[0049] In this configuration, the second ends N1, N2, N3 can also be designated as cold points, as opposed to the first ends P1, P2, P3 designated as hot points. Usually, the second ends N1, N2, N3 are connected to each other and form the neutral of the electric generator 4. In this power system, none of the ends of the windings 10a, 10b, 10c of the stator 8 is connected to another end of the windings 10a, 10b, 10c of the stator 8. Thus, the second ends N1, N2, N3 are not connected to each other and do not form a neutral. Similarly, the first ends P1, P2, P3 are not connected to each other.

[0050] The power supply system 1 comprises an adaptation circuit 1 configured to be connected in parallel to the load 2, and the first ends P 1 , P2, P3 and the second ends NI, N2, N3 of the windings 10a, 10b, 10c are connected to this adaptation circuit 1. The adaptation circuit 1 is configured to switch from a first operating mode in which a voltage of nominal value is supplied to the load 2 to a second operating mode in which a voltage of double the nominal value is supplied to the load 2.

[0051] To do this, the matching circuit 1 comprises three rectifier circuits 30a, 30b, 30c coupled in series, each rectifier circuit 30a, 30b, 30c comprising a first branch 31a, 31b, 31c and a second branch 32a, 32b, 32c in parallel, the first branch 31a, 31b, 31c being coupled to the first end PI, P2, P3 of a respective winding 10a, 10b, 10c, and the second branch 32a, 32b, 32c being coupled to the second end NI, N2, N3 of said winding.

[0052] In detail, the first branch 31a of the first rectifier circuit 30a is connected to the first end PI of the first winding 10a, the second branch 32a of the first rectifier circuit 30a is connected to the second end NI of the first winding 10a, the first branch 31b of the second rectifier circuit 30b is connected to the first end P2 of the second winding 10b, the second branch 32b of the second rectifier circuit 30b is connected to the second end N3 of the second winding 10b, the first branch 31c of the third rectifier circuit 30c is connected to the first end P3 of the third winding 10c, the second branch 32c of the third rectifier circuit 30c is connected to the second end N3 of the third winding 10c.

[0053] The matching circuit 1 comprises a first terminal 12 and a second terminal 14 which are configured to be connected to the load 2, the three rectifier circuits 30a, 30b, 30c being connected in series between the first terminal 12 and the second terminal 14. Each branch 31a, 31b, 31c, 32a, 32b, 32c of the rectifier circuits 30a, 30b, 30c comprises diodes with the same forward direction in the series connection of the rectifier circuits 30a, 30b, 30c, thus defining a downstream and an upstream for the electric current in the matching circuit 1. The forward direction of a diode is understood to mean the direction in which this diode lets the current pass when the diode is conducting.

[0054] In detail, the first branch 31a and the second branch 32a of the first rectifier circuit 30a are on the upstream side coupled to the first terminal 12 and therefore to the load 2, and are on the downstream side coupled to the upstream of the first branch 31b and the second branch 32b of the second rectifier circuit 30b. The downstream of the first branch 31b and the second branch 32b of the second rectifier circuit 30b is coupled to the upstream of the first branch 31c and the second branch 32c of the third rectifier circuit 30c. The downstream of the first branch 31c and the second branch 32c of the third rectifier circuit 30c is connected to the second terminal 14 of the matching circuit 1, and therefore to the load 2.

[0055] More specifically, for each rectifier circuit 30a, 30b, 30c, the first branch 31a, 31b, 31c, comprises a first diode 311a, 311b, 311c and a second diode 312a, 312b, 312c of the same forward direction and is coupled to the first end P1, P2, P3 of the respective winding 10a, 10b, 10c between the first diode 311a, 311b, 311c and the second diode 312a, 312b, 312c. For example, the first end P2 of the second winding 10b is coupled to the first branch 31b of the second rectifier circuit 30b between a first diode 311b and the second diode 312b.

[0056] For each rectifier circuit 30a, 30b, 30c, the second branch 32a, 32b, 32c comprises a first diode 321a, 321b, 321c and a second diode 322a, 322b, 322c of the same forward direction, and a switch S1, S2, S3 between the first diode 321a, 321b, 321c and the second diode 322a, 322b, 322c, the second diode 322a, 322b, 322c being downstream of the first diode 321a, 321b, 321c in the forward direction, the second branch 32a, 32b, 32c being coupled to the second end N1, N2, N3 of a respective winding between the switch S1, S2, S3 and the first diode 321a, 321b, 321c.For example, for the second rectifier circuit 30b, the second branch 32b comprises a first diode 321b and a second diode 322b of the same forward direction, and a switch S2 between the first diode 321b and the second diode 322b, the second diode 322b being downstream of the first diode 321b in the forward direction, the second branch 32b being coupled to the second end N2 of the second winding 10b between the switch S2 and the first diode 321b.

[0057] Due to the coupling of the first end PI, P2, P3, and the second end NI, N2, N3 with the branches 31a, 31b, 31c, 32a, 32b, 32c of the rectifier circuits 30a, 30b, 30c, these are bidirectional when the switches S 1 , S2, S3 are conducting, and unidirectional when the switches SI, S2, S3 are blocking.

[0058] The switches SI, S2, S3 are configured to change state according to a command, between a closed state in which an electric current can flow through them, and an open state in which the electric current cannot flow through them. The switches SI, S2, S3 are typically transistors, for example insulated-gate bipolar transistors (or IGBT, from the English "insulated-gate bipolar transistor"), insulated-gate field-effect transistors more commonly called MOSEET for the English "metal-oxide-semiconductor field-effect transistor", but the switches SI, S2, S3 can also be thyristors or electromechanical relays.

[0059] The adaptation circuit 1 is configured to switch from a first operating mode in which a voltage of nominal value is supplied to the load 2 to a second operating mode in which a voltage of twice the nominal value is supplied to the load 2. To do this, the switches SI, S2, S3 are used:

[0060] - when the switches SI, S2, S3 are open, only the first branches 31a, 31b, 31c of the rectifier circuits 30a, 30b, 30c, connected to the first ends PI, P2, P3 allow the current to pass when it is in the forward direction, the second branches 32a, 32b, 32c being interrupted by the switches SI, S2, S3; and due to the presence of the diodes 311a, 311b, 311c, 312a, 312b, 312c of the first branches 31a, 31b, 31c, the current of each phase coming from the first ends P 1 , P2, P3 of the windings 10a, 10b, 10c is positiveized (only the positive values ​​are retained) to give an output current with a voltage at a nominal value corresponding to the sum of the positive voltages of the phase voltages at each instant;

[0061] - when the switches SI, S2, S3 are closed, both the first branches 31a, 31b, 31c of the rectifier circuits 30a, 30b, 30c and the second branches 32a, 32b, 32c allow the current to pass when it is in the forward direction; and since in each rectifier circuit 30a, 30b, 30c the first branch 31a, 31b, 31c is connected to a first end PI, P2, P3 of a winding while the second branch 32a, 32b, 32c is connected to the second end NI, N2, N3 opposite to the first end PI, P2, P3, the first branch 31a, 31b, 31c and the second branch 32a, 32b, 32c alternately conduct the current in the forward direction, resulting in an output voltage corresponding to the sum of the absolute values ​​of the phase voltages, i.e. to a value twice the nominal value corresponding to the sum of the positive voltages of the phase voltages which would be obtained in the first operating mode.

[0062] The coupling of the second ends NI, N2, N3 of the windings 10a, 10b, 10c to the second branches 32a, 32b, 32c in fact makes it possible to implement a rectification of the negative parts of the sinusoidal voltages of the windings 10a, 10b, 10c. The switches SI, S2, S3 make it possible to choose whether or not to implement this rectification of these negative parts.

[0063] Figure 2 shows, in volts as a function of time, an example of the positive voltages 20a, 20b, 20c and the output voltage 22 at a nominal value when the switches are open, i.e. in the first operating mode. The positive voltages 20a, 20b, 20c correspond to the voltages across each rectifier circuit 30a, 30b, 30c. The positive voltages 20a, 20b, 20c have a sinusoidal shape over half their period and are milliseconds over the other half of their period. More precisely, due to the diodes 311a, 311b, 311c, 312a, 312b, 312c, only the positive values ​​of each phase voltage of the coils 10a, 10b, 10c are retained.Due to the series connection of the rectifier circuits 30a, 30b, 30c in parallel with the load 2, the positive voltages 20a, 20b, 20c add up to an output voltage 22 whose nominal value remains close to the maximum value taken by each positive voltage 20a, 20b, 20c, of value 1 in this example.

[0064] Figure 3 shows, in volts as a function of time, an example of the phase voltages 24a, 24b, 24c and the output voltage 26 at a value corresponding to the sum of the absolute values ​​of the phase voltages, when the switches S1, S2, S3 are closed. The phase voltages 24a, 24b, 24c correspond to the voltages of the coils 10a, 10b, 10c, and therefore have a sinusoidal shape. These phase voltages 24a, 24b, 24c are rectified by the effect of the diodes, and the series connection of the rectifier circuits 30a, 30b, 30c causes the summation of the voltages. The output voltage 26 whose value corresponds to the sum of the absolute values ​​of the voltages of phases 24a, 24b, 24c at each instant, of double value to maximum value taken by each phase voltage 24a, 24b, 24c, that is to say to a value close to 2 in this example for a maximum value of 1 for each phase voltage 24a, 24b, 24c.

[0065] Thus, by a simple command closing the switches SI, S2, S3, it is possible to double the value of the output voltage at the terminals 12, 14 of the adaptation circuit 1. Consequently, when the drive speed of the electric generator is sufficient, the switches SI, S2, S3 can be left open, limiting possible overvoltages. When the drive speed of the electric generator becomes insufficient, the switches SI, S2, S3 can be closed to ensure a sufficient supply voltage. The command to close the switches SI, S2, S3 can be implemented by a computer or by simpler means, for example analog or mechanical. The command to close the switches SI, S2, S3 can in particular result from the determination of a state causing a drop in rotation of the motor shaft or a passage of the rectified voltage below a voltage threshold.It is possible to measure the mechanical speed of the motor shaft, for example with a tachometer or a centrifugal force sensor such as an electromechanical centrifugal force relay. The output voltage or a value related to it can be measured by suitable sensors (voltmeter, etc.). The measurement is compared to a first threshold (related to the voltage or speed) below which the closing command of the switches S 1 , S2, S3 is sent to the switches.

[0066] With the closing command, the switches SI, S2, S3 of the second branches 32a, 32b, 32c of the three rectifier circuits 30a, 30b, 30c are turned on in order to cause a doubling of the output voltage value.

[0067] Similarly, it is possible to implement an opening command of the switches SI, S2, S3, for example by comparing a measurement related to the voltage or the speed with a corresponding second threshold, preferably different from the first threshold. With the opening command, the switches SI, S2, S3 of the second branches 32a, 32b, 32c are of the three rectifier circuits 30a, 30b, 30c are made blocking in order to divide the output voltage value by two.

[0068] This strategy is particularly advantageous for dealing with an autorotation regime of a turbomachine: in the event of autorotation and therefore a significant drop in the output voltage at terminals 12, 14 of the adaptation circuit 1, closing the switches SI, S2, S3 makes it possible to regain an output voltage high enough to guarantee the correct supply of most of the essential loads.

[0069] Previously, it was necessary to size the electric generator 4 so that it provided sufficient output voltage (generally between 10 and 20 V) to the essential loads in the autorotation regime, which required a heavy, bulky and expensive electric generator 4, with an oversizing which in normal operation resulted in too high a voltage (for example greater than 100-150 V).

[0070] Thanks to the proposed power supply system, the electric generator 4 can be of smaller size, since a doubling of the output voltage by the adaptation circuit 1 is possible in the autorotation regime, resulting in lower costs, reduced size, and a lower output voltage in normal operation. Advantageously, the power supply system is installed in a turbomachine 101 of an aircraft 100, as illustrated in FIG. 4.

[0071] The invention is defined by the claims, and is not limited to the embodiments described and shown in the attached figures. Modifications remain possible, in particular from the point of view of the constitution of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims

CLAIMS 1. Power supply system configured to electrically supply a load (2) comprising a three-phase electric generator (4) configured to be rotated by a motor shaft, the electric generator (4) comprising a rotor (6) and a stator (8), the stator (8) comprising three windings (10a, 10b, 10c) each corresponding to a phase of the electric generator (4), each winding comprising a first end (PI, P2, P3) and a second end (NI, N2, N3) opposite the first end, characterized in that the power supply system comprises an adaptation circuit (1) configured to be connected in parallel to the load (2) and comprising three rectifier circuits (30a, 30b, 30c) coupled in series, each rectifier circuit (30a, 30b, 30c) comprising a first branch (31a, 31b, 31c) and a second branch (32a, 32b, 32c) in parallel with the first branch (31a, 31b, 31c), the first branch (31a, 31b,31c) being coupled to the first end (PI, P2, P3) of a respective winding (10a, 10b, 10c), and the second branch (32a, 32b, 32c) being coupled to the second end (NI, N2, N3) of said winding, the matching circuit (1) being configured to switch from a first operating mode in which only the first branch (31a, 31b, 31c) is conductive and where an output voltage of nominal value is supplied to the load (2), to a second operating mode in which the first branch (31a, 31b, 31c) and the second branch (32a, 32b, 32c) are conductive and where an output voltage of double the nominal value is supplied to the load., 2. Power supply system according to claim 1, wherein for each rectifier circuit (30a, 30b, 30c): • the first branch (31a, 31b, 31c) comprises a first diode (311a, 311b, 311c) and a second diode (312a, 312b, 312c) of the same forward direction and is coupled to the first end (PI, P2, P3) of the respective winding (10a, 10b, 10c) between the first diode and the second diode, • the second branch (32a, 32b, 32c) comprises a first diode (321a, 321b, 321c) and a second diode (322a, 322b, 322c) of the same forward direction, and a switch (SI, S2, S3) between the first diode (321a, 321b, 321c) and the second diode (322a, 322b, 322c), the second diode (322a, 322b, 322c) being downstream of the first diode (321a, 321b, 321c) in the forward direction, the second branch (322a, 322b, 322c) being coupled to the second end (NI, N2, N3) of said winding (10a, 10b, 10c) between the switch (SI, S2, S3) and the first diode (321a, 321b, 321c).

3. Power supply system according to claim 2, wherein in the first operating mode, the switches (SI, S2, S3) are blocking, and in the second operating mode, the switches (SI, S2, S3) are conducting.

4. Power supply system according to any one of the preceding claims, wherein none of the ends (PI, P2, P3) of the windings (10a, 10b, 10c) of the stator (8) is connected to another end (NI, N2, N3) of the windings (10a, 10b, 10c) of the stator (8).

5. A power supply system according to any preceding claim, wherein each winding (10a, 10b, 10c) extends radially relative to an axis of rotation of the rotor (6), and the first end of a winding (10a, 10b, 10c) is between the rotor (6) and the second end (N1, N2, N3) of said winding.

6. Power supply system according to any one of the preceding claims, wherein the second ends (NI, N2, N3) of the windings (10a, 10b, 10c) of the electric generator (4) would correspond to a neutral phase if said second ends (NI, N2, N3) were connected together.

7. Power supply system according to any one of the preceding claims, wherein the adaptation circuit (1) comprises a first terminal (12) and a second terminal (14) which are configured to be connected to the load (2), the three rectifier circuits (30a, 30b, 30c) being connected in series between the first terminal (12) and the second terminal (14).

8. Turbomachine (101) comprising a motor shaft configured to be driven in rotation during operation of the turbomachine, and a power supply system according to any one of the preceding claims, comprising a three-phase electric generator (4) configured to be driven in rotation by the motor shaft.

9. Aircraft (100) comprising a turbomachine (101) according to the preceding claim, the turbomachine being attached to a wing or to a fuselage of said aircraft.

10. A method of adapting a power supply to a load (2) by a power supply system according to any one of claims 1 to 7, wherein when a condition causing a drop in rotation of the motor shaft or a drop in the output voltage below a voltage threshold is determined, the adaptation circuit (1) switches from a first operating mode in which only the first branch (31a, 31b, 31c) is conductive and where an output voltage of nominal value is supplied to the load (2), to a second operating mode in which the first branch (31a, 31b, 31c) and the second branch (32a, 32b, 32c) are conductive and where an output voltage of twice the nominal value is supplied to the load.

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