Stator element for electric machine of aircraft

Abstract

The present disclosure is a stator element (200) comprising:-an electrical conductor (202) that is elongated and hollow to define a flow channel (308) enabling coolant to flow from one end to the other of the conductor (202), the conductor (202) being designed to pass an electrical current; and-a connecting element (208; the invention relates to an electrical connector (200) comprising a conductor (202) having a channel (308), a connection element (901, 902) located at one of the ends of the conductor (202), the connection element comprising: a fluid connection terminal (210) designed to enable coolant to enter the channel (308) or to enable coolant to exit from the channel (308), and an electrical connection terminal (210) designed to electrically connect the conductor (202). The conductor (202) and the connecting element (208; 902) is formed from a single unitary piece.

Description

Technical Field

[0001] The invention relates to a stator element for an electric machine for an aircraft, as well as to an electric machine comprising such an element and to an aircraft comprising such an electric machine. Background Art

[0002] The development of "more electric" aircraft and the subsequent need for high-power, compact electric machines requires that thermal considerations be taken into account during the design phase of the electric machine. In fact, for power requirements of around 100 kW or even MW, the current density can reach very high values.

[0003] In this case, the stator windings are usually the main source of losses in the motor. The maximum temperature of the windings (determined by the maximum temperature of the conductor insulation) limits the current density and thus the torque density of the motor. The resistivity of the conductors and the subsequent Joule losses increase with temperature, which reduces the efficiency of the motor. Therefore, it is crucial to improve heat transfer as close to the windings as possible.

[0004] Common solutions for cooling electric motors include natural convection, forced air convection, and forced liquid convection.

[0005] Natural convection is the simplest solution, where most of the heat is dissipated through the motor's housing. Fins are often added to the housing to increase the convection surface area and thus the heat dissipation.

[0006] Forced air convection cooling systems typically include fans, which increase the overall heat exchange coefficient, but have disadvantages in terms of reliability and overall weight reduction. "Water jacket" type liquid forced convection cooling systems provide good heat removal compared to air cooling methods.

[0007] One of the limitations of the above cooling solutions is that the heat is dissipated via the housing of the motor located at the periphery of the motor. Therefore, the heat generated in the windings must pass through multiple areas of the motor (slot paper, yoke, etc.) before being discharged.

[0008] New solutions, known as direct winding cooling, are currently being proposed. These solutions allow the heat generated by the winding to be dissipated at its source. For example, a fluid can be circulated in a hollow conductor, or in a tank immersed or with oil circulation.

[0009] The present invention belongs to the first category.

[0010] For example, it is known to use a stator element of an electric machine, the stator element comprising:

[0011] an electrical conductor, the electrical conductor being elongated and hollow so as to define a flow channel for a coolant to flow from one end of the conductor to the other end, the conductor being designed to pass an electric current; and

[0012] a connecting element, the connecting element being located at one of the ends of the conductor, the connecting element comprising:

[0013] a fluid connection terminal designed to enable coolant to enter the channel or to enable coolant to leave the channel, and

[0014] Electrical connection terminals, which are designed to be electrical connection conductors.

[0015] In the prior art, the connection element is attached to the end of the conductor. This requires welding or soldering between the connection element and the conductor, while generally adhering to the temperature limit of the conductor (about 180°C for painted conductors). In addition, it must be ensured that the assembly is waterproof, which can be difficult, especially because of the previous constraints of not overheating the conductor and the small size of the conductor and its internal conduit (e.g., 2mm×3mm conductor and 0.3mm internal conduit).

[0016] It would therefore be desirable to provide a stator element for an electric machine that avoids at least some of the above-mentioned problems and constraints. Summary of the invention

[0017] Therefore, a stator element of an electric machine is proposed, comprising:

[0018] an electrical conductor, the electrical conductor being elongated and hollow so as to define a flow channel for a coolant to flow from one end of the conductor to the other end, the conductor being designed to pass an electric current; and

[0019] a connecting element, the connecting element being located at one of the ends of the conductor, the connecting element comprising:

[0020] a fluid connection terminal designed to enable coolant to enter the channel or to enable coolant to leave the channel, and

[0021] Electrical connection terminals, which are designed to be electrical connection conductors.

[0022] Characterized in that the conductor and the connecting element are formed from a single integral piece.

[0023] The invention may also include one or more of the following optional features in any technically possible combination.

[0024] Optionally, the one-piece is made by one of the following methods: additive manufacturing, wire drawing, machining and molding.

[0025] Optionally, the one-piece is made of copper, aluminum or an alloy of either of these two materials.

[0026] Also optionally, the flow channel has an inner diameter, the inner diameter of the fluid connection element is larger than the inner diameter of the flow channel, and the constriction is located between the diameter of the connection element and the diameter of the flow channel.

[0027] Also optionally, the constriction is gradual.

[0028] Also optionally, the constriction has rounded edges.

[0029] Also optionally, the electrical connection terminal comprises an electrical connection hole, which is, for example, provided on the tab, for example, to be used for tightening.

[0030] Also optionally, the electrical connection terminal comprises a threaded rod, which is, for example, arranged on the tab.

[0031] Also optionally, the fluid connection terminal comprises a male or female end piece, for example for connection to a flexible hose.

[0032] Also optionally, the stator element further comprises another connecting element located at the other end of the conductor, the other connecting element comprising:

[0033] a fluid connection terminal for letting coolant into the flow channel or letting coolant out of the flow channel, and

[0034] - electrical connection terminals, which are used for electrically connecting conductors;

[0035] The conductor and the two connecting elements are formed from a single integral piece.

[0036] A motor is also proposed, comprising:

[0037] - a rotor; and

[0038] - a stator for driving a rotor, the stator comprising a stator element according to the invention.

[0039] An aircraft is also proposed, comprising an electric machine according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The invention will be better understood with the aid of the following description, given by way of example only and with reference to the accompanying drawings, in which:

[0041] - Figure 1 is a three-dimensional view of an example of an electric machine in which the present invention may be implemented,

[0042] - Figure 2 According to the present invention, it can be used Figure 1 A three-dimensional view of an example of a stator element in an electric machine,

[0043] - Figure 3 It can be formed Figure 2 A cross-sectional view of an example of a connecting element of a part of a stator element,

[0044] - Figure 4 Is set in Figure 3 Cross-sectional view of a first alternative for a coolant duct in a connecting element,

[0045] - Figure 5 Is set in Figure 3 Cross-sectional view of a second alternative for the coolant duct in the connecting element,

[0046] - Figure 6 According to the present invention, it can be used Figure 1 A three-dimensional view of another example of a stator element in an electric machine,

[0047] - Figure 7 It can be used for Figure 2 A three-dimensional view of an example of a hollow electrical conductor in a stator element,

[0048] - Figure 8 yes Figure 7 A cross-sectional view of a hollow electrical conductor in FIG.

[0049] - Fig. 9 is a 3D view of the alternative connection element, and

[0050] - Fig.10 yes Fig. 9 Three-dimensional transparent view of the variant shown. DETAILED DESCRIPTION

[0051] refer to Figure 1 , an example of an electric machine 100 in which the present invention may be implemented will now be described.

[0052] The electric machine 100 firstly comprises a stator 102 in the form of a cylinder centered on an axis of rotation AA′.

[0053] The stator 102 includes, for example, longitudinal slots 104 and windings 106 (for clarity, Figure 1 Only one winding is shown in the figure), a longitudinal portion of the winding 106 is inserted into the slot 104. The winding 106 can be a distributed winding or a concentric winding.

[0054] The motor 100 further includes a rotor 108 that extends into the interior space of the stator 102 (at Figure 1 , the rotor 108 is shown outside the stator 102).

[0055] Each winding 106 is designed to have a current flowing through the winding 106 , in particular to generate a magnetic field for driving the rotor 108 about the rotation axis AA′ when the electric machine 100 is operated as a motor.

[0056] refer to Figure 2 Now, the method according to the present invention which can be used for Figure 1 A stator element 200 in an electric machine is shown.

[0057] In general, a stator element according to the invention may form all or part of the winding 106. In the example shown, a stator element 200 forms the winding 106.

[0058] The stator element 200 first includes an electrical conductor 202, which is elongated and hollow to define a flow channel for a coolant (a liquid, such as water, glycol water, silicone oil, a bearing lubricating fluid (such as BP oil 380), or a gas, such as air, nitrogen, helium) to flow from one end of the conductor 202 to the other end. For example, the conductor 202 has a plurality of longitudinal portions 204 connected by curved portions 206, and the longitudinal portions 204 are designed, for example, to be inserted into the slots 104. Therefore, the conductor 202 forms one or more turns (two turns in the example shown).

[0059] The stator element 200 further comprises a connecting element 208 at at least one of the ends of the conductor 202. For example, Figure 2 In FIG. 2 , a connecting element 208 is provided at each end of the conductor 202 .

[0060] The connection element 208 firstly comprises a fluid connection terminal 210, which is designed to allow the coolant to enter the channel or to allow the coolant to leave the channel. The fluid connection terminal 210 is, for example, in the form of an end piece, which is, for example, cylindrical, which is, for example, male, for example, to be inserted into a flexible hose of a cooling system, for example a hydraulic or pneumatic one, or is, for example, female, for example, to allow the flexible hose to be inserted into the end piece.

[0061] Typically, the fluid connection terminal 210 can be threaded to a liquid or gas standard thread (e.g., BSP (British Standard Pipe Thread), NPT (National Pipe Taper Thread), etc.) or other thread (e.g., quick connector). The fluid connection terminal 210 can be male or female.

[0062] The connection element 208 further comprises an electrical connection terminal 212, which is designed to electrically connect the conductor 202. For example, the electrical connection terminal 212 comprises a hole into which the lug is intended to be screwed (e.g., Figure 2 ).

[0063] In general, the electrical connection terminals can be standard (e.g., lugs) or other (e.g., military connectors). Other terminals can be provided on the body 302, such as connectors required for electrical measurements (e.g., voltage). If the hole in the connection terminal 212 is a through hole, a lug can be connected to transmit current to one end of the hole, and one or more sensors (e.g., voltage sensors) can be arranged at the other end of the hole. When the hole in the connection terminal 212 is not a through hole, the lug and one or more sensors can be connected to the only open end of the hole.

[0064] According to the invention, the conductor 202 and the one or more connecting elements 208 are formed from a single integral piece. This makes it possible to obtain:

[0065] - simpler assembly (lower costs and fewer assembly steps) and reduced risk of blockage: in fact, when the conductor is soldered or brazed to the connecting element, tin (or other materials) may seep out and block the passage of the fluid;

[0066] - a reduction in the electrical resistance between the connecting element 208 and the conductor 202;

[0067] - better sealing between the connecting element 208 and the conductor 202; and

[0068] - Reduction of the risk of damage to the lacquer of the conductor 202 : in fact, during welding / soldering between the conductor and the connection element, the components are heated, so that if the temperature becomes too high (for example, exceeding 180° C.), the lacquer of the conductor may be damaged.

[0069] For example, the single integral piece can be produced by additive manufacturing. However, other manufacturing methods are conceivable, such as drawing, machining or molding, for example, depending on the geometry of the conductor 202 (in particular the length of the conductor 202). A manufacturing method that enables the production of curved conductors 202 (instead of straight conductors) enables the risk of blockage to be limited, since when bending a straight conductor, the deformation of the passage cross section of the fluid may be difficult to control in some cases (for example, small / short radii of curvature).

[0070] The single integral piece may be made of copper, aluminum, or an alloy of either material.

[0071] The flow channel may have a circular, rectangular, diamond or other shaped cross section. The outer shape of the conductor 202 may differ from the shape of the cross section of the flow channel: for example, the cross section of the flow channel may be circular within a conductor 202 having a rectangular outer cross section.

[0072] refer to Figure 3 , examples of connection elements 208 will now be described in more detail.

[0073] The connection element 208 has a body 302 at the end of the electrical conductor 202, the body 302 carrying the terminals 210, 212. In the example shown, the electrical connection terminals 212 are in the form of tabs 304 with screw holes 306, for example for connection to a busbar.

[0074] Preferably, a chamfer 307 is provided between the body 302 and the electrical conductor 202 to mechanically strengthen the connection between the body 302 and the electrical conductor 202 .

[0075] The wiring channel denoted by reference numeral 308 has an inner diameter d, and the inner diameter D of the hydraulic connection terminal 210 is generally larger than the inner diameter d of the wiring channel 304 .

[0076] Thus, a constriction 310 is provided in the body 302 between the diameter D and the diameter d.

[0077] Preferably, the constriction 310 is gradual to reduce the pressure drop. In fact, according to Barlow's law, the maximum pressure that a pipeline can withstand depends on the size and material of the pipeline, so that the maximum pressure drop is given by the following formula:

[0078] [Formula 1]

[0079]

[0080] Where P is the voltage drop [Pa], σ is the elastic limit [Pa], S is the wall thickness of the conductor 202 [m], and D 外 is the outer diameter of the conductor 202 .

[0081] exist Figure 3 In the example shown, the constriction 310 is stepped with a straight slope between the steps. As a result, it is easier to machine since a drill bit with a reduced diameter can be used.

[0082] refer to Figure 4 , the constriction 310 may be abrupt. In this case, the pressure drop is given by the following formula:

[0083] [Formula 2]

[0084]

[0085] Where P is the pressure drop [Pa], ρ is the mass density of the coolant [kg / m 3 ], V is the average velocity of the fluid after contraction [m / s].

[0086] refer to Figure 5 , the constriction 310 may be circular. In this case, the pressure drop is given by:

[0087] [Formula 3]

[0088] P=0.025ρV 2

[0089] Where P is the pressure drop [Pa], ρ is the mass density of the coolant [kg / m 3 ], V is the average velocity of the fluid after contraction [m / s].

[0090] refer to Figure 6 , conductor 202 can also be straight.

[0091] refer to Figure 7 and Figure 8 The conductor 202 may also include fins or pins 702 extending into the transport conduit to improve heat transfer between the fluid and the conductor 202 , particularly when the stator element 200 is produced by additive manufacturing.

[0092] Fig. 9 and Fig.10 A variation of the connecting element 208 from the previous figures is shown, which variation has the reference number 902 .

[0093] The connection element 902 is identical to the connection element 208, except that the screw hole 306 is replaced by a threaded rod 904 protruding from the tab 304. The threaded rod 904 is designed, for example, to be inserted into a hole in a busbar and tightened by a bolt or the like.

[0094] In summary, it should be noted that the present invention is not limited to the embodiments described above. In fact, it is obvious to those skilled in the art that various modifications can be made to the embodiments described above based on the teachings just disclosed.

[0095] In the above detailed description of the present invention, the terms used should not be interpreted as limiting the present invention to the embodiments disclosed in this specification, but should be interpreted as including all equivalents that a person skilled in the art can anticipate by applying his common sense to the embodiments just disclosed.

Claims

1. A stator element (200) for an electric machine (100) for an aircraft, comprising: - an electrical conductor (202) which is elongated and hollow to define a flow channel (308) enabling a coolant to flow from one end of the conductor (202) to the other end, the conductor (202) being designed to pass an electric current; as well as - a connecting element (208; 902), the connecting element is located at one of the ends of the conductor (202), and the connecting element comprises: a fluid connection terminal (210) designed to allow the coolant to enter the channel (308) or to allow the coolant to leave the channel (308), and An electrical connection terminal (210), the electrical connection terminal being designed to electrically connect the conductor (202); Characterized in that the conductor (202) and the connecting element (208; 902) are formed from a single integral piece.

2. The stator element (200) according to claim 1, wherein: The one-piece is made by one of the following methods: additive manufacturing, wire drawing, machining and molding.

3. The stator element (200) according to claim 1 or 2, wherein: The integral piece is made of copper, aluminum or an alloy of these two materials.

4. The stator element (200) according to any one of claims 1 to 3, wherein: The flow channel (308) has an inner diameter (d), the inner diameter (D) of the fluid connection element (210) is larger than the inner diameter (d) of the flow channel, and the constriction (310) is located between the diameter (D) of the connection element and the diameter (d) of the flow channel (308).

5. The stator element (200) according to claim 4, wherein: The contraction portion (310) is gradual.

6. The stator element (200) according to claim 5, wherein: The constriction (310) has rounded edges.

7. The stator element (200) according to any one of claims 1 to 6, wherein: The electrical connection terminal (212) comprises an electrical connection hole (306), which is, for example, arranged on the tab (304), for example, to be used for tightening.

8. The stator element (200) according to any one of claims 1 to 6, wherein: The electrical connection terminal (212) includes a threaded rod (904), which is disposed on the tab (304), for example.

9. The stator element (200) according to any one of claims 1 to 8, wherein: The fluid connection terminal (210) comprises a male or female end piece, for example for connection to a flexible hose.

10. The stator element (200) according to any one of claims 1 to 9, further comprising a further connection element (208; 902) at the other end of the conductor (202), the further connection element comprising: a fluid connection terminal (210) for allowing the coolant to enter the flow channel (308) or to leave the coolant from the flow channel (308), and - an electrical connection terminal (212), the electrical connection terminal being used for electrically connecting the conductor (202); The conductor (202) and the two connecting elements (208; 902) are formed from a single integral piece.

11. An electric machine (100), comprising: - a rotor (108); as well as A stator (102) for driving the rotor (108), the stator (102) comprising a stator element (200) according to any one of claims 1 to 10.

12. An aircraft comprising the electric machine (100) according to claim 11.

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