FOIL-WRAPPED ROTOR FOR ELECTRIC MACHINES

Description

[0001] The invention relates to the field of rotor winding, and more particularly to the winding of multi-pole rotors comprising four poles. More specifically, the invention relates to a winding of conductors in an innovative material that allows for a reduction in mass. This mass reduction issue is particularly relevant to the field of rotating electrical machines in aircraft, where mass is a critical factor. However, the invention can be applied to any field of rotating electrical machines where reducing the machine's mass is a priority. The invention also relates to a cooling device for the rotor winding according to the invention, which improves heat extraction from the rotor winding.

[0002] Rotating electrical machines generally comprise a stator and a rotor that are electromagnetically coupled, with the rotor being driven in rotation by the stationary stator. The rotor may include one or more poles extending radially from the rotor and may include one or more coil windings mounted on the rotor pole.

[0003] Copper coil windings are commonly used in the rotors of synchronous electric machines. Indeed, the physical characteristics of copper, and particularly its low electrical resistance, make it an excellent electrical conductor in the case of electrical induction in a rotating electric machine. Therefore, copper windings take the form of thin copper wires wound around each pole to create turns.

[0004] However, the current mass of enameled copper wire conductors is a disadvantage for high-speed salient-pole rotors. Indeed, rotors wound with copper wire, due to their mass, limit rotor speeds, thus restricting the electrical performance of alternators and motors. Yet, for aircraft electrical machines, increasing mass to increase power is costly and problematic, since this increase in mass limits the rotational speed, which also hinders efficiency optimization.

[0005] Furthermore, the electrical resistance of the copper windings (although low according to conventional measurements) is sufficient to contribute to substantial rotor heating and reduce the machine's energy efficiency. However, attempting to lighten the windings around the poles to increase rotor speed and thus electrical induction also leads to increased heating of the windings.

[0006] Documents thus deal with the problem of thermal management in the rotor such as documents DE 28 26 607 A1, GB 1 046 145 A or EP 3 509 193 A1 without however determining a solution presenting sufficient characteristics in terms of heat evacuation.

[0007] The invention aims to overcome all or part of the problems mentioned above by proposing a replacement of the copper winding with an oxidized aluminum foil. This allows for a lighter pole, and therefore a lighter rotor, and provides better pole filling due to the absence of gaps between each layer of the conductor. Furthermore, the heat exchange surface between turns is greater with foil, which has a flat surface, than with wire. The invention also proposes a V-shaped spacer for extracting heat from the foil windings.

[0008] To this end, the invention relates to a rotating electrical machine rotor according to claim 1. The rotor comprises, in particular: a plurality of poles each extending along a first radial axis with respect to the rotor and along a second axis parallel to the rotor with respect to the rotor, each pole comprising a pole body, a rotor winding per pole, positioned against the pole body, the rotor winding taking the form of a strip extending over the length of said pole body along the first radial axis wound against the pole body, a plurality of locking wedges, a locking wedge of the plurality of locking wedges being in contact with a rotor winding associated with a pole body, said locking wedge being configured to exert pressure on said rotor winding in the direction of said pole body.

[0009] According to one aspect of the invention, the rotor winding is an oxidized aluminum strip.

[0010] According to one aspect of the invention, the rotor winding is a copper strip.

[0011] According to one aspect of the invention, the closing wedge is a V extending along two intersecting planes, a first plane of the two planes being in contact with the rotor winding of a first pole of the plurality of poles and a second plane of the two planes being in contact with the rotor winding of a second pole of the plurality of poles, the second pole being adjacent to the first pole.

[0012] According to one aspect of the invention, the V comprises an inlet opening positioned along a first end of the V along the second axis, a first outlet opening positioned along a second end of the V along the second axis, different from the first end, and a second outlet opening positioned along the second end of the V along the second axis, the inlet opening being connected to the first outlet opening and the second outlet opening by means of a conduit network.

[0013] According to one aspect of the invention, the conduit network successively takes a straight shape and a curved shape.

[0014] The invention also relates to a rotating electrical machine, comprising the rotor, the rotor winding of the pole being electrically connected to an electrical power source, via electrical connections, the electrical connections being obtained by cold pressure welding, friction stir welding, pressure brazing or pressure welding, the electrical power source being made of copper.

[0015] The invention will be better understood and other advantages will become apparent upon reading the detailed description of an embodiment given by way of example, a description illustrated by the accompanying drawing in which: [ Fig.1 ] there figure 1 represents a schematic cross-sectional view of a rotating electrical machine rotor according to the invention; [ Fig.2 ] there figure 2 represents a schematic view of a closing wedge according to the invention; [ Fig.3 ] there figure 3 represents a schematic view of the internal structure of the closing wedge of the figure 2 ; Fig.4 ] there figure 4 represents an electrical connection between a pole winding and an electrical component of a stator of a rotating electrical machine;

[0016] For the sake of clarity, the same elements will bear the same references in the different figures.

[0017] There figure 1 represents a schematic cross-sectional view of a rotor 1 of a rotating electrical machine according to the invention. The rotor 1 of the rotating electrical machine comprises a plurality of poles 22, and preferably four poles 22, each extending along a first axis A1 radial with respect to the rotor 1, and more precisely with respect to an axis of rotation of the rotor 1, and along a second axis A2 parallel to the rotor 1 with respect to the rotor 1, and more precisely with respect to the axis of rotation of the rotor 1. In other words, pole 22A extends along axis A1a and pole 22B extends along axis A1b. Each pole 22 comprises a pole body 220 extending along the first axis A1 and the second axis A2, and a rotor winding 222 per pole 22, positioned against the body 220 of the pole 22. The rotor winding 222 takes the form of a strip extending over the length L of said pole body 220 along the first radial axis A1 wound against the pole body 220.Per rotor pole, the strip wraps around the body 220 and is wound around the body forming a superposition of strip layers around the body 220.

[0018] The rotor 1 also includes a plurality of locking wedges 4. One locking wedge 4 of the plurality of locking wedges is in contact with a rotor winding 222 associated with a pole body 220, and said locking wedge 4 is configured to exert pressure on said rotor winding 222 in the direction of said pole body 220. The term "in the direction" means that the winding 222 is positioned against the pole body 220 by the pressure action of the locking wedge 4. This pressure action of the locking wedge 4 can preferably be carried out perpendicular to the length of the pole body 220, that is, perpendicular to the first radial axis A1 or about an axis having a component along an axis perpendicular to the first radial axis A1 and perpendicular to the second axis A2.

[0019] As stated previously, the winding 222 takes the form of a strip wrapped around the pole body 220, thus utilizing the entire available volume around the pole body 220, unlike wire windings according to the prior art. Therefore, a strip winding 222 has the advantage of being more compact than a conductor wire winding.

[0020] Indeed, the contact between two planar zones, namely two zones of the 222 winding of the strip, winding one around the other, is perfect. Conversely, the contact between two wire zones of a wire winding according to the prior art occurs only at a point of contact, thus creating a volume inaccessible to the conductor and therefore unsuitable for electrical induction.

[0021] In addition, as is known, heat is generated in the windings due to ohmic losses related to electric currents.

[0022] However, the permanent contact between two layers of the 222 winding of the strip also has the advantage of generating a perfect thermal bridge between the two layers, facilitating heat transfer and the extraction of heat to the outside. Conversely, imperfect contact between the conductor wires of a state-of-the-art winding allows air, which is a thermal insulator, to occupy the available volume between each conductor wire, thus hindering heat extraction from the state-of-the-art winding.

[0023] The rotor winding 222 is preferably made of oxidized aluminum foil. Oxidized aluminum foil has the advantage of lightening the winding and therefore the rotor pole 22, thus increasing the rotational speed of pole 22. Furthermore, the oxidation of the aluminum also provides electrical insulation between the different layers of the foil in winding 222, while simultaneously reducing the distance between each layer of the foil, thereby promoting thermal bridging between the layers. Indeed, the anodic oxidation of the foil allows for winding with very thin insulating layers, approximately 8 µm, optimizing the filling of the winding by the 222 winding and heat exchange.

[0024] Alternatively, the rotor winding 222 is a copper strip. A copper strip has the advantage of being a better electrical conductor compared to oxidized aluminum strip, but also has the disadvantage of being heavier, limiting the rotor's rotational speed.

[0025] As stated previously, the rotor 1 includes a plurality of locking wedges 4. More precisely, the rotor 1 includes a necessary number of locking wedges 4 to hold each winding 222 against the pole body 220 associated with said winding 222. Each locking wedge 4 has a shape that promotes pressure on the winding 222 in contact with said locking wedge 4 against the pole body 220 around which the winding 222 is located. Therefore, the locking wedge 4 can have a planar shape extending over the length L of the pole body 220 and over the length of the winding 222 along the first axis A1 and along the second axis A2.

[0026] According to a preferred embodiment, the rotor 1 has as many locking wedges 4 as poles 22. Thus, a rotor 1 with four poles comprises four locking wedges 4. Each locking wedge 4 is in contact with two adjacent poles 22 so as to induce pressure on each winding 222 in the direction of each pole body 220. To achieve this, the locking wedge 4 takes the form of a V, as shown in figure 2 extending along two intersecting planes, the first plane P1 of the two planes, which extends parallel to the first axis (A1a for pole 22A) and parallel to the second axis A2, being in contact with the rotor winding 222A of a first pole 22A of the plurality of poles 22, and the second plane P2 of the two planes, which also extends parallel to the first axis (A1b for contact with pole 22B) and parallel to the second axis A2, being in contact with the rotor winding 222B of a second pole 22B of the plurality of poles 22, the second pole 22B being adjacent to the first pole 22A, as shown in figure 1 .

[0027] This arrangement has the advantage of reducing the number of closing wedges 4 and therefore reducing the overall mass of the closing wedges 4 on the rotor 1.

[0028] Furthermore, any shape of the locking wedge 4 that allows pressure to be applied to windings 222 in the direction of two adjacent pole bodies 220 can be considered. For example, a triangular locking wedge can be considered if two faces of the locking wedge are in contact with two adjacent pole windings 22.

[0029] In the rest of the description, the closing wedge 4 is referred to as a V-block 4.

[0030] The closing wedge 4 is obtained from a material allowing good heat conduction in order to induce good heat extraction from the windings 222. As an indicative example, the closing wedge is obtained from a metallic material.

[0031] The use of a ve 4 extending along two distinct planes, the first plane P1 and the second plane P2 allowing perfect contact between the winding 222 and one of the first plane P1 or second plane P2 has the advantage of having better cooling of the windings 222 due to the increase in the heat exchange surface compared to the potential heat exchange surface of the wires of a winding according to the state of the art.

[0032] Furthermore, the closing wedge 4, shown in figure 2 , understand : an inlet opening 42 positioned along a first end 420 of the closing wedge 4 along the second axis A2, a first outlet opening 44A positioned along a second end 440 of the closing wedge 4 along the second axis A2, different from the first end 420, and a second outlet opening 44B positioned along the second end 440 of the closing wedge 4 along the second axis A2, so as to allow a coolant to pass through the closing wedge 4 from the inlet opening 42 to the first outlet opening 44A or to the second outlet opening 44B and to facilitate heat exchange between the winding 222 and the coolant passing through the closing wedge 4. As an indicative example, the coolant is a heat transfer fluid, for example oil.However, any liquid that promotes heat extraction and therefore has good thermal characteristics can be used as a coolant.

[0033] The inlet opening 42 is connected to the first exhaust opening 44A and the second exhaust opening 44B via a conduit network 48, shown in figure 3 The conduit network 48, which is included in the closing wedge 4, therefore allows the cooling fluid to circulate in the closing wedge 4.

[0034] Furthermore, the inlet opening 42 can be positioned randomly relative to the first end 420 of the closing wedge 4. Thus, the inlet opening 42 is in contact with the first plane P1 of the two planes. According to one variant, the inlet opening 42 is in contact with the second plane P2 of the two planes. According to another preferred variant, and shown in figure 2 The inlet opening 42 is in contact with both planes P1 and P2. The first outlet opening 44A can be positioned randomly along the second end 440 and is, in turn, in contact with the first plane P1. The second outlet opening 44B can be positioned randomly along the second end 440 and is in contact with the second plane P2. According to a variant of the invention, the first outlet opening 44A and the second outlet opening 44B coincide at the second end 440.

[0035] According to a preferred embodiment of the invention, the first evacuation opening 44A is distinct from the second evacuation opening 44B.

[0036] According to a preferred aspect of the invention, the radial distance between the rotor 1 and the inlet opening 42 is greater than the radial distance between the rotor 1 and the first discharge opening 44A. And, similarly, the radial distance between the rotor 1 and the inlet opening 42 is greater than the radial distance between the rotor 1 and the second discharge opening 44B.

[0037] Furthermore, the duct network 48 can successively take a straight form 480 and a curved form 482. The overall shape of the duct network 48 can be likened to a serpentine shape starting from the inlet opening 42 and ending either at the first discharge opening 44A or the second discharge opening 44B. Moreover, the straight form 480 is defined by a slope αinclined with respect to the second axis A2. More precisely, the line defining the shape of line 480 intersects the second axis A2 at an angle forming the slope α. As an indicative example, the slope α is between 1° and 3°. The duct network 48 thus takes the form of a channel within the cooling bay 4, extending between the first discharge opening 44A and the second discharge opening 44B. The succession of straight lines and curves, as well as the slope of each straight line, has the advantage of optimizing the flow of the cooling fluid inside, resulting in a high flow rate in the duct network 48. Consequently, heat extraction is improved. It can also be considered that each straight line 480 be defined by a slope α specific and different in order to further optimize the flow.

[0038] Thus, the positioning of the inlet opening 42 in the radial proximity of the rotor coupled with the radial separation of the first discharge opening 44A and the second discharge opening 44B, the presence of the slope α Combined with the centrifugal force due to the rotation of rotor 1, this improves the circulation of coolant in the closing chamber 4 by increasing the flow rate. Therefore, with a significant flow rate of coolant in the closing chamber 4, this configuration increases the heat extraction capacity of V 4 and, particularly, of the coolant passing through the closing chamber 4.

[0039] It should be noted that the figure 3 The purpose is to schematically represent the conduit network 48 in order to show its shape in accordance with the claimed invention. However, the arrangement of the inlet opening 42 and that of the first outlet opening 44A in the figure 3 does not correspond to the invention as claimed.

[0040] There figure 4 Figure 6 represents an electrical connection between a winding 222 of pole 22 and a power supply 80 of a rotating electrical machine. Specifically, the rotor winding 222 of pole 22 is electrically connected to the power supply 80 via electrical connections 6. Generally, the power supply 80 is made of copper. However, the winding 222 is, according to a previously stated variant, an oxidized aluminum strip. And the electrical connection between a copper component and an oxidized aluminum component is relatively poor.

[0041] Therefore, to ensure a reliable electrical connection between the power supply 80 and the winding 222, the electrical connections 6 are made by cold pressure welding, friction stir welding, pressure brazing, or pressure welding. As a preferred example, cold pressure welding is the method used to connect the electrical connections 6 to the winding 222, ensuring electrical continuity between the aluminum foil winding 222 and the copper power supply 80. Furthermore, this connection method, namely cold pressure welding, is economical. According to this method, the power supply 80 is brazed and then crimped to the oxidized aluminum foil winding 222.

Claims

1. Rotor (1) for a rotating electrical machine comprising: - a plurality of poles (22a, 22b) which each extend along a first radial axis (A1a, A1b) relative to a rotation axis of rotation of the rotor (1) and along a second axis (A2) parallel with the rotor (1) relative to the rotation axis of the rotor (1), each pole (22) comprising a pole body (220), - one rotor winding (222) per pole (22), positioned against the body (220) of the pole (22), the rotor winding (222) being in the form of a strip which extends over the length (L) of the pole body (220) along the first axis (A1) which is radially wound against the pole body (220), - a plurality of closure wedges (4), a closure wedge (4) from the plurality of closure wedges (4) being in the form of a "V" and being in contact with a rotor winding (222) which is associated with a pole body (220), the closure wedge (4) being configured to apply pressure to the rotor winding (222) in the direction of the pole body (220), characterized in that the closure wedge (4) comprises an inlet opening (42) which is positioned along a first end (420) of the closure wedge (4) along the second axis (A2), a first discharge opening (44A) positioned along a second end (440) of the closure wedge (4) along the second axis (A2), which is different from the first end (420) and a second discharge opening (44B) which is positioned along the second end (440) of the closure wedge (4) along the second axis (A2), the inlet opening (42) being connected to the first discharge opening (44A) and to the second discharge opening (44B) along a conduit network (48) which is intended to circulate a cooling fluid in the closure wedge (4), the conduit network (48) having a serpentine shape and successively assuming a shape of a straight line (480) and a shape of a curve (482).

2. Rotor (1) of a rotating electrical machine according to claim 1, wherein the rotor winding (222) is a strip of oxidized aluminum.

3. Rotor (1) of a rotating electrical machine according to claim 1, wherein the rotor winding (222) is a strip of copper.

4. Rotor (1) of a rotating electrical machine according to any one of claims 1 to 3, wherein the closure wedge (4) is a "V" which extends along two secant planes (P1, P2), of which a first plane (P1) of the two planes is in contact with the rotor winding (222A) of a first pole (22A) of the plurality of poles (22) and of which a second plane (P2) of the two planes is in contact with the rotor winding (222B) of a second pole (22B) of the plurality of poles (22), the second pole (22B) being adjacent to the first pole (22A).

5. Rotating electrical machine comprising the rotor (1) according to any one of the preceding claims, the rotor winding (222) of the pole (22) being electrically connected to an electrical supply source (80), via electrical connections (6), the electrical connections (6) being obtained by means of cold pressure welding, friction stir welding, pressure soldering or pressure welding, the electrical power supply source (80) being made of copper.