Electric machine for aircraft comprising at least one means for preventing short circuit between two stator phases, and method for protecting same

Abstract

The invention relates to an electric machine for an aircraft, comprising a stator (1) comprising at least three phases (10), each phase comprising a winding (12), a control branch (11) and a neutral branch (13), each neutral branch (13) being connected together at a neutral point (14), the electric machine (3) comprising at least one protection (5) mounted on the neutral branch (13) of at least one phase (10), each protection member (5) has an inactive state (P1) in which the protection member (5) allows current to flow in the phase (10) in which the protection member (5) is mounted, and a protection state (P2) in which the protection member (5) interrupts current flow in the phase (10) in which the protection member (5) is mounted, thereby protecting the electric machine in the event of a short circuit (CC).

Description

Technical Field

[0001] The invention relates to the field of electric machines for aircraft, for protecting the electric machine in the event of a short circuit between two phases of the stator of the electric machine. Background Art

[0002] As is known, electric motors are installed in aircraft such as helicopters to provide torque, for example, to propel the aircraft (motor operation mode), or to generate electrical energy (generator operation mode). Electric motors used in electric propulsion aircraft and thermal / electric hybrid aircraft are usually permanent magnet synchronous motors, because the high power density of permanent magnet synchronous motors can reduce the onboard weight of the aircraft.

[0003] Figure 1 An example of a permanent magnet synchronous motor 300 on a helicopter is schematically shown. As is known, the permanent magnet synchronous motor 300 comprises a stator 100 mounted on an aircraft housing element, and a rotor 200 rotatably mounted relative to the stator 100. In this example, the permanent magnet synchronous motor 300 is a radial flux type, that is, the rotor 200 is cylindrical, and the stator 100 extends around the outside of the rotor 200 in an annular shape.

[0004] refer to Figure 1 and Figure 2 As is known, the rotor 200 comprises permanent magnets and the stator comprises a number of phases 110, typically three phases. Each phase 110 comprises a winding 130, a control branch 120 and a neutral branch 140. The control branch 120 is connected to a power converter 400, typically an inverter / rectifier, and the neutral branches 140 are connected together at a point called a neutral point 150. During operation of the generator, the rotation of the rotor 200 relative to the winding 130 of the stator 100 generates an excitation flux, so that an AC voltage is generated between the phases 110.

[0005] In fact, if Figure 2 As shown, when two windings 130 of the stator 100 touch at a point called the short-circuit point CC, a short circuit may occur in the motor 300. The rotation of the rotor 200 then permanently provides a current circulation between the short-circuit point CC and the neutral point 150. Since the impedance of the winding 130 is generally low, the current increases rapidly, which may cause overheating and damage to the components of the stator 100.

[0006] To reduce this risk, it is known from patent application FR3057029A1 to stop the rotation of the motor rotor if a short circuit is detected by adding a mechanical decoupling device (for example by disengagement or by a clutch). Such a device is massive, expensive and difficult to integrate.

[0007] Another solution is to size the motor to withstand the short circuit for a long time, ie until the aircraft lands. Therefore, it has been proposed to strengthen the windings and / or the insulation, but this increases the overall size and mass of the motor, undesirably reducing the yield of the motor.

[0008] It is also known from patent application FR3091060A1 to collect hot air from a thermal power generation system and inject it into the rotor of the electric machine. This makes it possible to reach the Curie temperature of the permanent magnets, rendering them ferromagnetic. The disadvantage of this solution is that it exposes the electric machine to undesirably high temperatures.

[0009] It is also known from patent application US20140268460A1 to add a protection element, such as a fuse, between the neutral point and the coil of each phase or alternatively on one side of the terminal connector, which cuts off the current path in the event of a short circuit. In practice, it has proven difficult to integrate the protection element into the motor, and it is also difficult to control and maintain the protection element. Summary of the invention

[0010] The present invention aims to at least partially eliminate the above-mentioned drawbacks and protect the electric machine in the event of a short circuit between two phases of the stator.

[0011] The present invention relates to a motor for an aircraft, which comprises a stator and a rotor rotatably mounted relative to the stator, wherein the rotor comprises at least one permanent magnet, and the stator comprises at least three phases, each phase comprises a winding, a control branch and a neutral branch, wherein the control branch is configured to be connected to a power conversion device, and each neutral branch is connected together at a neutral point.

[0012] The invention is notable in that the motor comprises at least one protection element mounted on the neutral branch of at least one phase, each protection element comprising:

[0013] - an inactive state, in which the protection element allows current to flow in the phase on the neutral branch in which the protection element is installed, and

[0014] A protection state in which the protection element interrupts the flow of current in the phase on the neutral branch in which it is installed, in order to protect the motor in the event of a short circuit.

[0015] Thanks to the invention, the circulation of current in one or more phases of the stator is controlled by means of protection elements, making it possible to protect the electric machine in the event of a short circuit, in particular between two phases of the stator. Each protection element is able to interrupt the circulation of current in one or more given phases in a targeted, simple and rapid manner, compared to rotor decoupling devices and hot air circuits of the prior art. Protection elements such as these make it possible to interrupt a short circuit between two phases, thereby effectively avoiding overheating and damage to the stator elements.

[0016] According to one aspect of the invention, the stator comprises a housing, and at least a portion of the neutral branch of the phase on which the protection element is mounted extends outwardly to the housing of the stator. Preferably, the neutral point is located outside the housing of the stator. This makes it easier to integrate, control and maintain the protection element.

[0017] According to one aspect of the present invention, the neutral branch of each phase in the plurality of phases is equipped with a protective element. Preferably, when N represents the number of phases of the stator, the neutral branches of at least (N-1) phases are equipped with protective elements. No matter where the short circuit between the two phases occurs, targeted and effective protection can be provided for the motor. The current can be interrupted in at least one of the two phases where the short circuit point is located.

[0018] According to a first aspect of the present invention, the electric machine comprises a plurality of bipolar protection members, each of which is mounted on a neutral branch of one phase. Advantageously, the bipolar protection members are simple, high quality and low cost.

[0019] According to a second aspect of the invention, the electric machine comprises a single multi-pole protection element mounted on the neutral branch of each of the plurality of phases of the stator, preferably of all phases. The term "multi-pole" is used to describe an element having more than two poles. Advantageously, only one protection element is required to interrupt the flow of current in each phase.

[0020] According to a preferred aspect of the invention, each protection element comprises a switch for each phase on which the protection element is mounted. Preferably, the switch is in the form of an electromechanical contactor (EMR), a static contactor (SSR) or a pyrotechnic fuse (PSS). Preferably, the switch is in the form of a solid-state power controller (SSPC). Such a protection element enables simple and effective interruption of the current in the phase or phases on which the protection element is mounted.

[0021] According to a preferred aspect of the invention, the motor comprises at least one control element configured to activate the protection state of each protection element. The control element ensures the control of the protection elements.

[0022] According to a preferred aspect of the invention, the electric machine comprises at least one detection member for detecting the current circulating in at least one phase of the stator, preferably detecting the sum of the currents circulating in all phases of the stator. It is advantageous to use such a detection member to detect short circuits and their location at an early stage. Advantageously, a single detection member for detecting the sum of the currents of the phases is sufficient to monitor all phases, which reduces the required overall size.

[0023] According to one aspect of the invention, the detection element is in the form of a magnetic current sensor comprising a magnetic ring around the neutral branch or control branch of at least one phase of the stator, preferably all phases of the stator. This type of detection element has very small overall dimensions, making it easy to assemble on the motor.

[0024] The magnetic current sensor is preferably of the Hall effect type, providing high detection accuracy and ease of integration.

[0025] Preferably, the detection means is connected to the control means so that the protection means can be automatically controlled as a function of monitoring the currents in the phases of the stator.

[0026] The invention also relates to an assembly comprising an electric machine as described above and a power conversion device connected to a control branch of each phase of the stator. Advantageously, the protection element is also capable of protecting the electric machine in the event of a short circuit in the power conversion device.

[0027] Preferably, the power conversion means is in the form of an inverter / rectifier.

[0028] In one aspect of the invention, the power conversion device comprises a housing, and the neutral point is located inside the housing of the power conversion device. This makes it easier to integrate the protection element into the neutral branch and make it easier to access during maintenance. The control is also simplified by the control element and the detection element.

[0029] The invention also relates to an aircraft comprising an electric motor as described above. Preferably, the aircraft is in the form of a helicopter. Advantageously, the protection element is able to protect the electric motor in the event of a short circuit in flight, thereby avoiding any risk of overheating and damage until the aircraft has landed.

[0030] The present invention also relates to an aircraft, comprising the assembly of the electric machine and the power conversion device as described above.

[0031] The present invention also relates to a method for protecting a motor as described above, wherein the initial state of each protection element is an inactive state so that current flows in each phase of the stator, the method comprising:

[0032] - a step of detecting a short circuit between two phases of the stator, and

[0033] - A step of activating a protection state of at least one protection element in order to interrupt the flow of current in at least one phase of the stator affected by the short circuit, thereby protecting the electric machine.

[0034] The present invention also relates to a method for protecting an assembly comprising a motor and a power conversion device as described above, wherein the initial state of each protection element is an inactive state so that current flows in each phase of the stator, the method comprising:

[0035] - steps to detect short circuits, and

[0036] - A step of activating a protection state of at least one protection element in order to interrupt the flow of current in at least one phase of the stator affected by the short circuit, thereby protecting the electric machine.

[0037] The protection method can advantageously be implemented simply and quickly, so that the electric machine can be protected without waiting in the event of a short circuit between two stator phases. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The invention will be better understood on reading the following description, given by way of example, and with reference to the following drawings, given by way of non-limiting example, in which like references indicate similar objects.

[0039] Figure 1 is a schematic diagram of a permanent magnet synchronous motor connected to a power converter according to the prior art.

[0040] Figure 2 yes Figure 1 Schematic diagram of a short circuit between two phases of a permanent magnet synchronous motor stator.

[0041] Figure 3 Schematic diagram of a permanent magnet synchronous motor connected to a power converter and equipped with a protection element according to an embodiment of the present invention.

[0042] Figure 4 yes Figure 3 Schematic diagram of a permanent magnet synchronous motor, wherein the rotor is not shown.

[0043] Figure 5 An embodiment of the present invention is used to protect the stator from short circuits between two phases. Figure 3 A schematic diagram of the method for a permanent magnet synchronous motor is shown.

[0044] Figure 6 It is used to protect against short circuit in power conversion device. Figure 3 A schematic diagram of the method for a permanent magnet synchronous motor is shown.

[0045] Figure 7 Schematic diagram of a permanent magnet synchronous motor according to another embodiment of the present invention, wherein the rotor is not shown.

[0046] Figure 8 Schematic diagram of a permanent magnet synchronous motor according to another embodiment of the present invention, wherein the rotor is not shown.

[0047] It should be noted that the accompanying drawings illustrate the invention in detail in order to implement the invention and, if necessary, said drawings can of course serve to better define the invention. DETAILED DESCRIPTION

[0048] The invention relates to an aircraft comprising one or more electric machines connected to one or more power conversion devices in order to provide torque, for example to propel the aircraft (motor operating mode), or to generate electrical energy (generator operating mode). The aircraft is of electric propulsion or thermal / electric hybrid architecture type. The aircraft is, for example, a helicopter.

[0049] Figure 3 An example of a permanent magnet synchronous motor 3 on a helicopter is schematically shown. Advantageously, the motor has a high power density, thereby reducing the onboard weight of the aircraft. The motor is preferably connected to a power conversion device 4 of the inverter / rectifier type.

[0050] As mentioned above and Figure 3 As shown, the permanent magnet synchronous motor 3 comprises a stator 1 mounted on an aircraft shell element, and a rotor 2 rotatably mounted relative to the stator 1. In this example, the permanent magnet synchronous motor 3 is of radial flux type, i.e. the rotor 2 is cylindrical and the stator 1 extends in an annular shape around the outer surface of the rotor 2. The present invention is also particularly applicable to synchronous motors with reverse radial flux type permanent magnets, wherein the stator 1 is cylindrical and the rotor 2 extends in an annular shape around the outer surface of the stator 1. The present invention is also applicable to synchronous motors with axial flux type permanent magnets, wherein the stator 1 and the rotor 2 are cylindrical and extend towards each other in the axial direction.

[0051] As mentioned above and Figure 3 As shown, the rotor 2 comprises permanent magnets and the stator 1 comprises a number of phases 10, usually three phases. Figure 4 (where the rotor 2 is not shown for the sake of clarity), each phase 10 comprises a winding 12, a control branch 11 and a neutral branch 13. The control branch 11 and the neutral branch 13 extend to the ends of the winding 12 respectively. The control branch 11 is connected to the inverter / rectifier 4 and is used to power the motor 3 or transmit the generated current to the inverter / rectifier 4 depending on whether it is in the motor operation mode or the generator operation mode. The neutral branches 13 are connected together at a point called the neutral point 14 to form the main part of the motor 3. In the generator operation mode, the rotation of the rotor 2 relative to the winding 10 of the stator 1 generates an excitation flux, thereby generating an AC voltage between the phases 10.

[0052] According to the present invention and Figure 3 and Figure 4 As shown, the motor 3 includes one or more protection elements 5. Each protection element 5 is installed on one or more phases 10 of the stator, more specifically, on the neutral branch 13 of one or more phases 10. Each protection element 5 has an inactive state P1 (see Figure 3 ) and protection state P2 (see Figure 5). In the inactive state P1, the protection element 5 allows the current to flow in the phase 10 where the protection element is installed. In the protection state P2, the protection element 5 interrupts the flow of current in the phase 10 where the protection element is installed. In other words, the protection element 5 enables one or more neutral branches 13 to be electrically connected to the neutral point 14 (inactive state P1), or enables one or more neutral branches 13 to be electrically disconnected from the neutral point 14 (protection state P2). The protection element 5 thus acts as a switch.

[0053] The integration of the protection element 5 in the electric machine 3 advantageously makes it possible to protect the electric machine 3 in the event of a short circuit CC, in particular between two phases 10 of the stator 1 (see Figure 5 ) or even in the power conversion device 4 (see Figure 6 ) protects the motor when a short circuit occurs. More specifically, activation of the protection state P2 enables the neutral point 14 to be disconnected when a short circuit occurs, thereby avoiding the risk of overheating and damage to the components of the motor 3 and / or the power conversion device 4 caused by the short circuit.

[0054] For all intents and purposes, a short circuit between two phases 10 of the stator 1 of the electric machine 3 means that the two phases 10 of the stator 1 are Figure 5 The windings 12 shown are in contact at a position called the short-circuit point CC. The rotation of the rotor 2 then permanently provides a current circulation between the short-circuit point CC and the neutral point 14. Since the impedance of the windings 12 is generally low, the current builds up rapidly and can damage components of the motor 3. The invention makes it possible to interrupt the short circuit by disconnecting the neutral point 14 to prevent damage. The invention also makes it possible to prevent other types of short circuits, such as a short circuit between the supply harnesses of two different phases 10 of the stator 1, or a short circuit between two different power transistors of the inverter / rectifier 4.

[0055] according to Figure 3 , Figure 4 and Figure 8 In one aspect of the invention shown, it should be noted that the number of phases 10 of the stator 1 is N, and (N-1) or N neutral branches 13 are equipped with protection elements 5. This effectively enables the protection of the elements of the stator 1 wherever a short circuit occurs, by preventing the formation of current loops. Preferably, the (N-1) neutral branches 13 are equipped with protection elements 5 so as to provide optimal protection while minimizing mass and overall size requirements. In practice, a short circuit affects two phases 10 of the stator 1 and therefore necessarily affects at least one phase 10 equipped with a protection element 5 sufficient to interrupt the flow of the current causing the short circuit. In Figure 3 and Figure 4 In the example shown of an electric machine 3 with three phases 10, only two neutral branches 13 are equipped with protection elements 5. Figure 8In the example shown, all neutral branches 13 are equipped with protection elements 5 in order to stop the circulation of current in all phases 10 .

[0056] according to Figure 3 , Figure 4 and Figure 8 In one aspect of the present invention shown, at least a portion of the neutral branch 13 on which the protection member 5 is mounted extends outward to the housing 15 of the stator 1. In other words, the protection member 5 as a functional element of the stator 1 physically extends outside the stator 1. Figure 3 , Figure 4 and Figure 8 As shown, this is preferably achieved by positioning the neutral point 14 outside the housing 15 of the stator 1. The neutral branch 13 thus comprises at least one external portion extending outside the stator 1 and connected together at the neutral point 14. Mounting the protection element 5 on the outside is advantageously simple and quick, has no overall size restrictions, and protects the protection element 5 from high temperatures. In addition, this type of mounting makes maintenance easier.

[0057] Preferably, if Figure 3 and Figure 4 As shown, the neutral point 14 extends inwardly to the outside 40 of the inverter / rectifier 4. In other words, the neutral point 14, the functional elements of the stator 1, are physically extended into the inverter / rectifier 4. Therefore, each neutral branch 13 includes a first end connected to the winding 12 in the stator 1 of the motor 3 and a second end connected to the neutral point 14 in the inverter / rectifier 4. Between the first end and the second end, each neutral branch 13 has an outside where the protective member 5 is installed. In other words, for easier access and installation, the protective member 5 extends to the outside of the stator 1 and the outside of the inverter / rectifier 4.

[0058] according to Figure 3 and Figure 4 In the first aspect of the invention shown, each protection element 5 is in the form of an electric dipole mounted on a single phase 10 of the stator 1. Preferably, the motor 3 comprises (N-1) or N protection elements 5 mounted on the phases 10 of the stator 1. Each protection element 5 controls the circulation of current in the phase 10 where the protection element is mounted.

[0059] according to Figure 8 In the second aspect of the invention shown, the electric machine 3 comprises a single protection element 5 in the form of an electrical multipole. Multipole refers to a component having more than two poles. The protection element 5 is installed in several phases 10 of the stator 1, preferably in all phases, and is configured so that each phase 10 in which the protection element is installed can be interrupted. Figure 8 In the example shown, the protection element 5 is in the form of a six-pole with three connections for mounting on three phases 10 of the stator 1 .

[0060] like Figure 3 , Figure 4 and Figure 8 As shown, each protection element 5 is a commutator having two different states, namely, an inactive state P1 and a protection state P2. The protection state P2 is configured to be triggered only when a short circuit occurs, otherwise the protection element 5 is in the inactive state P1.

[0061] According to a preferred aspect, each protection element 5 comprises a switch for installing each phase 10. Figure 3 and Figure 4 In the embodiment shown, each double-pole protection element 5 is in the form of a single switch. Figure 8 In the illustrated embodiment of a multi-pole protection element 5 for a plurality of phases 10, each multi-pole protection element 5 comprises a switch assembly, one switch per phase, the switches being configured to be triggered simultaneously. In a preferred aspect, each switch is in the form of a solid-state relay (SSR), an electromechanical relay (EMR), or a pyrotechnic fuse (also known as a pyrotechnic fuse). Preferably, the switch is in the form of a solid-state power controller (SSPC), which advantageously reduces mass and volume. Such switches are known to those skilled in the art and are therefore not described further.

[0062] according to Figure 3 and Figure 4 In one aspect of the invention schematically shown in FIG. 1 , the motor 3 further comprises a control member 7 for controlling each protection member 5. The control member 7 enables the protection state P2 of each protection member 5 to be activated, otherwise the protection member 5 is in the inactive state P1. Preferably, the control member 7 provides the same control to each protection member 5 and is configured to activate the protection state P2 of each protection member 5 simultaneously to protect all phases 10. Preferably, the control member 7 is in the form of a computer. Preferably, the control member 7 switches on each protection member 5 so as to transmit a control signal thereto.

[0063] According to one aspect of the present invention, the motor 3 further comprises one or more detection members 6, which are configured to detect parameters of the motor 3, such as the current flowing in the phase 10, the rotation speed of the rotor 2 or the position of the rotor 2. Figure 3 , Figure 4 , Figure 7 and Figure 8 In the preferred aspect shown, the motor 3 comprises one or more detection members 6 for detecting the current flowing in the phases 10 of the stator 1. The detection member 6 is installed in a control branch 11 (see Figure 3 and Figure 4 ) or at the neutral branch 13 (not shown).

[0064] according to Figure 3 and Figure 4In the first aspect shown, each phase 10 of the stator 1 is equipped with a detection member 6. Alternatively, one or more phases 10 may be provided which are not equipped with a detection member 6. Figure 7 and Figure 8 In the second aspect shown, the electric machine 3 comprises a single detection member 6 for detecting the sum of the currents circulating in all the phases 10 of the stator 1 .

[0065] Preferably, reference Figure 3 , Figure 4 , Figure 7 and Figure 8 The detection element 6 is in the form of a magnetic current sensor, which includes branches 11, 13 ( Figure 7 ) or the branches 11, 13 of all phases 10 of the stator 1 ( Figure 8 ) of the magnetic ring. Preferably, the detection member 6 is in the form of a Hall effect sensor.

[0066] according to Figure 3 and Figure 4 In the preferred aspect shown, the control member 7 is connected to each detection member 6 and is configured to detect the occurrence of a short circuit based on a detection parameter (such as current). Preferably, the control member 7 is configured to compare the detection value with a predetermined threshold value as stored in a database of the control member 7 to detect whether the threshold value has been exceeded. Preferably, the control of the protection member 5 in the protection state P2 is automatically performed based on the analysis of the detection parameters, thereby achieving fast and effective protection. Preferably, parameter detection is performed continuously or periodically for automatic early detection of the occurrence of a short circuit. Alternatively or additionally, the control of the state of the protection member 5 can be performed manually by an operator.

[0067] refer to Figure 5 and Figure 6 The present invention also relates to a protection method, wherein the initial state of each protection element 5 is an inactive state P1 to allow current to flow in each phase 10 of the stator 1 of the motor 3, the method comprising:

[0068] - a step E1 of detecting a short circuit CC between two phases 10 of the stator 1 , and

[0069] A step E2 of activating the protection state P2 of the protection element 5 in order to interrupt the flow of current in the phase 10 of the stator 1 affected by the short circuit CC.

[0070] The protection method is performed when the electrical machine 3 is operated in motor or generator mode. Before the detection step E1 , the integration of the protection element 5 is in an inactive state P1 , so that the current in each phase 10 of the stator 1 flows normally.

[0071] refer to Figure 5, the detection step E1 is preferably performed based on one or more parameter detection values ​​of the motor 3 (for example, the current flowing in each phase 10 of the stator 1 or the sum of the currents flowing in all phases 10). Other parameters can be detected, such as the rotational speed and the rotor position. The detection member 6 transmits these detected values ​​that have been acquired to the control member 7, and the control member 7 compares these detected values ​​with a predetermined threshold value, and a detection value exceeding the threshold value corresponds to a short circuit. Advantageously, such detection is automatic and pre-determined. Alternatively or supplementally, the detection can also be performed by an operator.

[0072] refer to Figure 6 , the activation step E2 is performed after the detection step E1, preferably immediately after the detection step. Figure 6 In the first aspect of the invention shown, the control means 7 sends a control signal to the protection means 5 of the phase 10 affected by the short circuit CC to activate the protection state P2. The other protection means 5 remain in the inactive state P1. Activating the protection state P2 of a single protection means 5 located on the short circuit loop is advantageously sufficient to interrupt the current generated by the short circuit. Figure 5 In the example shown, the short circuit CC affects two phases 10 of the stator 1, one of which is equipped with a protection element 5 and the other is not, in order to minimize the overall size. The activation step E2 is therefore performed only on a single protection element 5 on the short circuit loop. When the short circuit affects two phases 10, both of which are equipped with a protection element 5, the activation step E2 can be performed only on one of the two protection elements 5 and is sufficient to properly isolate the faulty phase. When the motor 3 has more than three phases 10, for example five or six phases, if one of the N phases of the motor is faulty, this enables continued operation in a degraded manner on the remaining (N-1) phases 10. This enables the motor 3 to be designed so that the motor 3 continues to operate once the missing phase is properly insulated.

[0073] Preferably, the detection step E1 also enables the determination of the phase 10 of the stator 1 affected by the short circuit, namely Figure 5 The short-circuit point CC between the two windings 12 shown is located in two phases. Figure 5 In the example shown of a dedicated detection element for each phase 10 , this is advantageously done as a function of the position of the detection element 6 in which the anomaly detection has been carried out. Figure 6 An example is shown in which a short-circuit point occurs between two power transistors of the inverter / rectifier 4 .

[0074] According to the second aspect of the invention, during the activation step E2, the current is interrupted in all phases 10 equipped with protection means 5. It is not necessary to locate the short circuit CC, which makes the protection more rapid and reliable. In other words, the use of Figure 6 In the example shown in FIG. 1 , the protection state P2 of each protection element 5 is activated. Figure 8 In the example shown, only the protection state P2 of the multi-pole protection element 5 is activated to achieve the interruption of the current in all phases 10 .

[0075] After the activation step E2 has been carried out, the current circulating in the phase 10 of the stator 1 in which the protection element 5 is installed is interrupted. The short-circuit loop is broken, thereby eliminating the risk of overheating and damage to the components of the stator 1. The advantage of this solution is that it can be implemented in advance, simply and quickly, thus avoiding any undesired heating of the components. In addition, this solution is low-cost and easy to integrate, especially because the neutral point 14 is located outside the electric machine 3.

Claims

1. An electric motor (3) for an aircraft, comprising a stator (1) and a rotor (2) rotatably mounted relative to the stator (1), the rotor (2) comprising at least one permanent magnet, the stator (1) comprising a housing (15) and at least three phases (10), each phase (10) comprising a winding (12), a control branch (11) and a neutral branch (13), the control branch (11) being configured to be connected to a power conversion device (4), the neutral branches (13) being connected together at a neutral point (14), the electric motor (3) being characterized in that it comprises at least one protective member (5) mounted on the neutral branch (13) of at least one phase (10), at least a portion of the neutral branch (13) of the phase (10) on which the protective member (5) is mounted extending outwardly to the housing (15) of the stator (1), and each protective member (5) having: - an inactive state (P1) in which the protection element (5) allows current to flow in the phase (10) on the neutral branch in which the protection element (5) is installed, and - a protection state (P2) in which the protection element (5) interrupts the circulation of current in the phase (10) on the neutral branch where the protection element (5) is installed, in order to protect the motor (3) in the event of a short circuit (CC).

2. The motor (3) according to claim 1, characterized in that The neutral point (14) is located outside the housing (15) of the stator (1).

3. The electric motor (3) according to claim 1 or 2, characterized in that The neutral branch (13) of each phase of a plurality of phases (10) is equipped with a protection element (5), preferably the neutral branches (13) of at least (N-1) phases (10) are equipped with protection elements (5), wherein N represents the number of phases (10) of the stator (1).

4. The motor (3) according to any one of claims 1 to 3, characterized in that The motor comprises a plurality of bipolar protection elements (5), each protection element (5) being mounted on a neutral branch (13) of a phase (10).

5. The motor (3) according to any one of claims 1 to 3, characterized in that: The electric machine (3) comprises a single multi-pole protection element (5) mounted on the neutral branch (13) of each phase of a plurality of phases (10), preferably of all phases (10) of the stator (1).

6. The electric machine (3) according to any one of claims 1 to 5, characterized in that Each protection element (5) comprises a switch for each phase (10) on which the protection element (5) is mounted, the switch preferably being in the form of an electromechanical contactor, a static contactor or a pyrotechnic fuse.

7. An assembly comprising a motor (3) and a power conversion device (4) as claimed in any one of claims 1 to 6, characterized in that: The power conversion device (4) is connected to a control branch (11) of each phase (10) of the stator (1).

8. The assembly according to claim 7, characterized in that The power conversion device (4) comprises a housing (40), and the neutral point (14) is located inside the housing (40) of the power conversion device (4).

9. An aircraft, characterized in that: It comprises the motor (3) according to any one of claims 1 to 6.

10. A method for protecting an electric machine (3) as claimed in any one of claims 1 to 6, wherein the initial state of each protection element (5) is an inactive state (P1) so as to allow current to flow in each phase (10) of the stator (1), characterized in that: The method comprises: - a step (E1) of detecting a short circuit (CC) between two phases (10) of said stator (1), and - a step (E2) of activating the protection state (P2) of at least one protection element (5) in order to interrupt the flow of current in at least one phase (10) of the stator (1) affected by said short circuit (CC), thereby protecting said electric machine (3).

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