Electronic modules for rotating electrical machines

Abstract

The present invention relates to an electronic module (36) for a rotating electric machine (10), comprising: a housing (40) including a base (41); a power module assembly mounted on the base (41) of the housing, the assembly being capable of rectifying a multiphase current system obtained from the phases of the stator of the electric machine and being capable of optionally supplying power to the stator phases in the multiphase current system; a positive terminal (43) and a negative terminal (44) for supplying current to the power module assembly, the positive terminal being electrically connected to the power module assembly via a positive trace (45) placed spaced apart from the base of the housing, the negative terminal being electrically connected to the power module assembly via a negative trace (46) placed spaced apart from the base of the housing, characterised in that the negative trace and the positive trace at least partially overlap each other.

Description

Technical Field

[0001] The invention relates to an electronic module for supplying power to a rotating electric machine of a vehicle, in particular a motor vehicle, and to an electric machine equipped with such a module.

[0002] The invention has application in the field of rotating electrical machines such as alternators and alternator-starters, the voltage of which is greater than 48V, for example. Background Art

[0003] It is known in the art to use power module assemblies comprising electronic switches of the MOSFET type in order to rectify a multiphase current system obtained from the phases of the stator of an electrical machine in generator mode and to supply the same phases of this stator in motor mode.

[0004] Each of these power modules is electrically connected to one phase of the stator and to one of the two supply terminals B+ and B-.

[0005] These supply terminals of the electronic module are electrically connected to the battery and must be electrically connected to the power module. Positive and negative traces passing through the housing of the electronic module in which the power module is housed are designed to distribute current to the module.

[0006] Due to their switching, the power modules are responsible for raising the temperature in the housing. In order to dissipate the heat to the outside, it is known to mount a heat sink at the base of the housing. In EP1556940A1, the outer surface of the housing comprises fins in order to improve the exchange surface between the inside and the outside of the housing. Electronic modules cooled by water are also known in the prior art. However, these solutions are only curative.

[0007] There is a need for an electronic module having a power module with limited heating. Summary of the invention

[0008] The object of the present invention is to effectively eliminate these drawbacks by proposing an electronic module for a rotating electrical machine, comprising:

[0009] - a housing comprising a base;

[0010] - a power module assembly mounted on the base of the housing, which assembly can rectify a multiphase current system obtained from the phases of the stator of the electric machine and can optionally supply power to the stator phases in the multiphase current system;

[0011] - a positive terminal and a negative terminal for supplying current to the power module assembly, the positive terminal being electrically connected to the power module assembly via a positive trace placed spaced apart from the base of the housing, and the negative terminal being electrically connected to the power module assembly via a negative trace placed spaced apart from the base of the housing, characterized in that the negative trace and the positive trace at least partially overlap each other.

[0012] The superposition of the positive and negative tracks (also called tracks B+ and B-) makes it possible to reduce the inductance of these tracks. This makes it possible to increase the switching speed of the power modules, thereby reducing the losses during switching. Therefore, the heating of these power modules is reduced.

[0013] Traces spaced apart from the base are not supported on the base.

[0014] The power module can be placed axially between the base and the tracks B+ and B-. This improves the heat dissipation of the power module, in particular due to the better structural order. The axial dimensions of the housing are also used in an optimal way.

[0015] According to one aspect of the invention, the negative and positive traces may be overmolded. A housing made of insulating material, in particular plastic, surrounds a conductive material, such as copper. The positive and negative traces may have a rectangular cross section.

[0016] According to an aspect of the invention, the base may be substantially flat. The plane may be perpendicular to an axis of the module defining an axial direction. The base may be substantially circular, in particular substantially circular around the axis of the module. The axis of the module may be parallel to an axis of rotation of the motor, in particular in conjunction with an axis of rotation of the motor, on which the electronic module may be placed.

[0017] The base may have a surface inside the housing and a surface outside, the surface outside may face the stator of a motor in which the electronic module may be mounted. The thickness of the base may be in the range of 5 mm to 20 mm. The base may dissipate heat generated by the power module during operation.

[0018] According to one aspect of the invention, an overlap may exist when a straight line having an axial direction passes through each of the traces.

[0019] According to one aspect of the invention, the track is spaced apart from the base portion, meaning that there is a space between the track and the base portion, at least locally, in particular in the axial direction.

[0020] The positive or negative trace may extend in a plane parallel to the base. The positive and negative traces may be in flat contact with each other. As a variant, there is a lower space, the length of which is axially shorter than the length of one of the traces. The axial distance between the trace and the base may be greater than twice, in particular three times, in particular four times, the axial thickness of one of the traces.

[0021] According to one aspect of the invention, the positive and negative tracks may overlap over more than half the length of one of the two tracks, in particular over more than 75%, in particular over more than 90%.The length is the sum of the lengths of the straight sections of the tracks.

[0022] According to one aspect of the invention, the positive track can be placed axially between the base and the negative track. As a variant, the negative track is placed axially between the base and the positive track.

[0023] According to one aspect of the invention, the positive and negative traces extend linearly, as opposed to traces extending across a surface and in multiple directions. "Linearly" means that the extending direction is overwhelming relative to the other two directions.

[0024] According to one aspect of the invention, one of the two positive and negative traces is curved and the other is straight. The curved trace may include at least two straight portions forming a bend at their intersection. The angle of the bend measured between the straight portions may be less than 60°, preferably less than 45°. The bend may have a circular shape. The axis of the module may pass through the bend. The two portions may extend radially. The curved trace may have only two straight portions.

[0025] According to one aspect of the invention, the positive trace is straight and the negative trace is curved. As a variant, the positive trace is curved and the negative trace is straight.

[0026] As a variant, each track may be curved. Also as a variant, all or part of the two tracks may have a global rounded form.

[0027] The positive and negative traces may be separated from one another in a central region of the housing, which may be centered about an axis of the housing.

[0028] According to one aspect of the invention, the housing may include a generally cylindrical wall extending from a base. The positive terminal and the negative terminal may be disposed in a first region of the wall. The positive trace may extend from the first region of the wall to the second region. The negative trace may extend from the first region to a third region of the wall spaced apart from the second region. Thus, each trace may extend from one edge of the housing to another edge of the housing through the center of the housing.

[0029] The second region may be substantially equidistant from the first region and the third region.

[0030] The wall may be partially non-conductive, and preferably completely non-conductive. The wall may be continuous. The wall may extend axially beyond the positive and negative traces. The wall is substantially cylindrical.

[0031] According to one aspect of the invention, the electronic module may include a plurality of phase connectors, in particular three, each of which may be connected to a stator phase. For each phase connector, the power module assembly may include at least one positive module electrically connected to a positive terminal and the phase connector, and at least one negative module electrically connected to a negative terminal and the phase connector.

[0032] Thus, the present system can be three-phase. The assembly of positive power modules forms a positive half-bridge. The assembly of negative power modules forms a negative half-bridge. The phase connectors make it possible to introduce the phases from the outside of the housing into the inside by passing through the wall.

[0033] According to an aspect of the invention, the power module may be a controlled switch, for example of the MOSFET type.

[0034] According to one aspect of the invention, each phase connection may pass through the wall. The first, second and third regions associated with the positive and negative traces alternate with the phase connection regions. When viewed circumferentially around the wall, there is an alternation between the positive and negative traces on the one hand and between the phase connections on the other hand.

[0035] The power module assembly may comprise two positive modules and two negative modules, or respectively three positive modules and three negative modules, for each phase connection.

[0036] According to another aspect of the invention, the electronic module may include a second positive trace and a second negative trace, the second positive trace and the second negative trace being mounted on the base and electrically insulated from the base. The second positive trace may electrically connect the positive trace and some or all of the positive power modules. The second negative trace may electrically connect the negative trace and some or all of the negative power modules.

[0037] Each second positive and negative track may in particular extend circumferentially from the second region or the third region.

[0038] To avoid electrical contact, a first insulating layer may be provided between each of the second positive and negative traces and the base.

[0039] Each positive and negative trace may be in contact with an associated trace surface to allow current to pass.

[0040] Each positive and negative trace may be fixed by screwing onto the second associated trace. A first fixing unit, such as a screw, may be screwed into each positive or negative trace, into the second associated trace and into the base of the housing. A first protrusion may be provided on the exterior of the housing to accommodate the first fixing unit. Each first protrusion may be integral with the base of the housing. Each first protrusion may be in the form of a stud.

[0041] According to one aspect of the invention, the electrical contact between the track and the second track is made via a surface contact, in particular only via this surface contact.The first associated fixing unit does not conduct electrical current.

[0042] According to one aspect of the invention, some or all of the positive modules are mounted on the second positive trace.

[0043] According to one aspect of the invention, for each phase connector, a phase trace may be mounted on the base to electrically connect the phase connector and a power module associated with the phase connector.

[0044] According to one aspect of the invention, each phase trace may be placed axially between one of the phase connections and the base.

[0045] Each phase trace may be fixed by being screwed into the associated phase connector. A fixing unit (e.g. a screw) may be screwed into each phase connector, into the associated phase trace and into the base of the housing. A protrusion may be provided on the exterior of the housing to accommodate the fixing unit. Each protrusion may be integral with the base of the housing. Each protrusion may be in the form of a stud.

[0046] According to one aspect of the invention, an insulating layer may be provided between each phase track and the base to avoid electrical contact. The thickness of the insulating layer or layers may be equal to 200 μm or less, in particular less than 150 μm.

[0047] According to one aspect of the invention, some or all of the negative modules associated with the phase connection are mounted on the phase trace.

[0048] According to one aspect of the invention, the electrical contact between each phase connector and the second track is made via a surface contact, in particular exclusively via this surface contact. The associated fixing unit does not conduct electrical current.

[0049] According to one aspect of the invention, the second positive trace, the second negative trace and the power trace may belong to a common electronic board. The board may be fixed to the base of the housing by the first fixing unit and / or by other dedicated fixing units. The traces are insulated from each other by the insulating material of the electronic board. The assembly of the traces in the housing is thus simplified.

[0050] According to one aspect of the invention, the module may include a unit for controlling the power module assembly. The housing may include a cover parallel to the base, in which a recess is provided. The control unit may be placed in the recess. Placing the control unit in the recess may effectively dissipate the heat released by the control unit due to the increased exchange surface. The recess may have a substantially square form. The control unit may be completely housed in the recess. As a variant, it may be only partially in the recess.

[0051] According to one aspect of the invention, the positive and negative traces are axially located between the base and the cover. The wall, base and cover may define an enclosed space. Once all electronic components are placed in the enclosed space, the cover may be sealed to the wall, in particular by an adhesive.

[0052] The invention also relates to a rotating electrical machine comprising: a stator, which is fixed in rotation and comprises a plurality of phases; a rotor, which can rotate about the rotation axis of the electrical machine; and an electronic module as described above. The electronic module is fixed relative to the stator.

[0053] The rotation axis of the motor can be combined with the axis of the module. In this case, the electronic module is placed axially on one side of the stator.

[0054] As a variant, the two axes may be substantially perpendicular to each other. The electronic module is placed radially outside the stator.

[0055] Each phase of the stator may be connected to a phase connection of the electronic module. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Other advantages and features of the present invention will become apparent from a reading of the description shown in the accompanying drawings, in which:

[0057] Figure 1 A schematic cross-sectional view of an electric machine equipped with an electronic module according to the present invention is shown;

[0058] Figure 2 Schematically and partially shown Figure 1 A view of a portion of an electric machine with separated components;

[0059] Figure 3 shows schematically and partially the front part of the body of an electronic module according to the invention;

[0060] Figure 4 Details of an electronic module according to the invention are shown schematically and partially. DETAILED DESCRIPTION

[0061] DETAILED DESCRIPTION Figure 1 A multiphase rotating electrical machine 10 is shown, in particular for a motor vehicle. The rotating electrical machine 10 converts mechanical energy into electrical energy in alternator mode and can be operated in electric motor mode to convert electrical energy into mechanical energy. The rotating electrical machine 10 is, for example, an alternator, an alternator-starter or a reversible electrical machine.

[0062] The rotating electrical machine 10 comprises a housing 11. Inside the housing 11, it also comprises a shaft 13, a rotor 12 rotating integrally with the shaft 13 and a stator 15 surrounding the rotor 12. The stator and the housing are fixed in rotation. The rotational movement of the rotor 12 occurs around the axis of rotation X of the electrical machine.

[0063] In this example, the housing 11 comprises assembled together a front bearing 16 and a rear bearing 17. The bearings 16, 17 are of hollow form and each supports centrally a respective ball bearing 18, 19 for rotatably fitting the shaft 13.

[0064] A pulley 20 is fixed to the front end of the shaft 13, at the front bearing 16, for example by a nut supported on the base of the cavity of the pulley. The pulley 20 makes it possible to transmit a rotational movement to the shaft 13, or for the shaft 13 to transmit its rotational movement to the belt.

[0065] The rear end of the shaft 13 supports a collector 22. The collector includes a body made of an electrically insulating material and a slip ring 21 overmolded in the body. The slip ring 21 is in the form of an annular ring and rotates with the rotor 12. Brushes 23 belonging to a brush holder 24 are arranged to rub on the slip ring 21. The brush holder 24 is electrically connected to an electronic component 36, which controls the voltage applied to the brushes.

[0066] The front bearing 16 and the rear bearing 17 may include substantially lateral openings for the passage of air to allow the rotary electric machine to be cooled by the circulation of air generated by the rotation of a front fan 25 located on the front axial face of the rotor 12 (i.e. at the front bearing 16) and by the rotation of a rear fan 26 located on the rear axial face of the rotor (i.e. at the rear bearing 17). Alternatively, the bearings may include ducts allowing the passage of a cooling liquid.

[0067] In this example, the rotor 12 is a rotor with claws. It includes two magnetic wheels 31. Each magnetic wheel 31 is formed by a flange 32 and a plurality of claws 33 forming magnetic poles. The flange 32 has a transverse orientation and has, for example, a substantially annular form. The rotor 12 also includes a cylindrical core 34, which is axially interposed between the magnetic wheels 31. In this case, the core 34 is formed by two half-cores, each half-core belonging to one magnetic wheel. Between the core 34 and the claws 33, the rotor 12 includes a coil 35, in this case, the coil 35 includes a winding hub and an electrical winding on the hub. For example, a collector ring 21 belonging to the collector 22 is connected to the coil 35 by a wired connection. The rotor 12 may also include a magnetic element between two adjacent claws 33.

[0068] In this embodiment, the stator 15 comprises a body 27 in the form of a set of metal plates, provided with recesses, for example of semi-closed or open type, provided with recessed insulation for fitting an electrical winding 28. The winding 28 passes through the recess in the body 27 and forms a front bun 29 and a rear bun 30 on both sides of the body of the stator. The winding 28 is connected, for example, in the form of a star or a triangle.

[0069] Furthermore, the winding 28 is formed by one or more phases, in this case three phases. Each phase comprises at least one conductor passing through a recess in the stator body 27 and forming a chignon with all the phases. The winding 28 is electrically connected to an electronic module 36 fixed relative to the stator and is referred to Figure 3 and Figure 4 Describe in more detail.

[0070] In the example considered, the electronic module 36 comprises a housing 40 having a base 41 , a power module assembly mounted on the base of the housing which can rectify a multiphase current system obtained from the phases of the stator 15 and can supply the phases of the multiphase current system.

[0071] In the example considered, the base 41 is substantially flat and perpendicular to the axis of the module which joins with the axis of the electric machine 10. The base is substantially circular around the axis of the module.

[0072] The base has an inner surface 50 on the housing 40 and an outer surface 51 facing the stator 15. The thickness of the base may be in the range of 5 mm to 20 mm.

[0073] In the example considered, the housing also comprises a substantially cylindrical continuous wall 54 extending from the base 41 in a direction opposite to the stator 15. In this case, the wall 54 is non-conductive. The wall extends axially beyond the positive and negative tracks.

[0074] Although not shown, the housing further comprises a unit for controlling the power module assembly, and a cover parallel to the base, in which a recess is provided. The control unit is placed in the recess. The recess may have a substantially square form.

[0075] In the example considered, the wall 54 , the base 41 and the cover define an enclosure. Once all the electronic components are placed in the enclosure, the cover can be sealed on the wall 54 .

[0076] The electronic module 36 also includes a positive terminal 43 and a negative terminal 44 to provide current to the power module assembly. The positive terminal 43 is electrically connected to the power module assembly through a positive trace 45 spaced apart from the base 41 of the housing, and the negative terminal 44 is electrically connected to the power module assembly through a negative trace 46 spaced apart from the base of the housing.

[0077] In the example considered, the positive and negative traces at least partially overlap each other, in this case over more than half the length of the negative trace 46 .

[0078] The positive track 45 and the negative track 46 are axially located between the base 41 and the cover. More specifically, in this case, the negative track 46 is placed between the base 41 and the positive track 45.

[0079] The positive and negative tracks 45 and 46 are overmolded. A housing made of insulating material, in particular plastic, surrounds a conductive material, for example made of copper. In this case, the positive and negative tracks have a rectangular cross section.

[0080] In the example considered, the positive track 45 and the negative track 46 extend in a plane parallel to the base 41 and are in flat contact with each other. The axial distance between the negative track 46 and the base may be greater than twice the axial thickness of one of the tracks.

[0081] In the example considered, the positive track 45 is curved and the negative track is straight. The positive track comprises two straight portions with radial extension, which form a bend at their intersection. The angle of the bend measured between the straight portions is less than 60° and substantially equal to 45°. The bend 56 has a circular form and passes through the axis X.

[0082] In the example considered, the positive terminal 41 and the negative terminal 42 are arranged in a first region of the wall. The positive trace 45 extends from the first region of the wall to the second region. The negative trace 46 extends from the first region to a third region of the wall spaced apart from the second region. Thus, each trace extends from one edge of the housing to the other edge of the housing through the center of the housing 41. In this case, the second region is substantially equidistant from the first region and the third region.

[0083] In the example considered, the electronic module 36 comprises three phase connections 60, each connectable to a phase of the winding 28 of the stator 15. Each phase connection 60 passes through the wall 54 so as to bring a phase from the outside of the housing 40 to the inside by passing through the wall 54.

[0084] For each phase connector 60, the power module assembly comprises at least one positive module, for example two positive modules, electrically connected to the positive terminal 43 and the phase connector, and at least one negative module, for example two negative modules, electrically connected to the negative terminal 44 and the phase connector 60. The assembly of positive power modules forms a positive half-bridge. The assembly of negative power modules forms a negative half-bridge. The power modules may be controlled switches, for example of the MOSFET type.

[0085] In the example considered, the first, second and third zones associated with the positive track 45 and the negative track 46 alternate with the connected zones 60 .

[0086] In the example considered, the electronic module 36 comprises a second positive track and a second negative track mounted on the base 41 and electrically insulated from said base 41. These tracks are not Figure 3 and 4. The second positive trace electrically connects the positive trace 45 and some or all of the positive power modules. The second negative trace electrically connects the negative trace 46 and some or all of the negative power modules. Each second positive and negative trace may extend circumferentially, in particular, from the second region or the third region. In order to avoid electrical contact, a first insulating layer may be provided between each second positive and negative trace and the base 41. Each positive and negative trace may be in contact with the associated trace surface to allow current to pass.

[0087] In the example considered, each positive trace 45 and negative trace 46 can be fixed by tightening the associated second positive or negative trace. A first fixing unit, such as a screw, can be screwed into each positive or negative trace, the associated second trace and the base 41. A first protrusion can be provided on the outside of the housing to accommodate the first fixing unit. Each first protrusion can be integral with the base of the housing. Each first protrusion can be in the form of a stud. The first fixing unit passes through the first threaded opening 62 of the positive trace 45 and the negative trace 46.

[0088] In the example considered, for each phase connection 60 , a phase track 61 is mounted on the base 41 in order to electrically connect the phase connection 60 and the power module associated with this phase connection.

[0089] like Figure 4 As shown, each phase trace 61 is disposed axially between the base 41 and one of the phase connectors 60 .

[0090] In the example considered, the module comprises three fixing units 65, which are screws for example. Each fixing unit is screwed into one of the phase connections 60, into one of the phase traces 61 and into the base 41 of the housing. A single fixing unit can achieve mutual fastening. For each phase connection 60, a single fixing unit 65 is provided to fix the phase trace 61 on the phase connection 60.

[0091] In the example considered, each phase connection 60 has a hole 67 for the passage of one of the fixing units 65. Each phase track 61 also has a hole 68 for the passage of one of the fixing units 65. The through holes are aligned in pairs.

[0092] In the example considered, the housing 40 comprises three protrusions 70 that house the fixing units 65. Each protrusion 70 is arranged in the base 41 of the housing. Each protrusion 70 is integral with the base 41 of the housing and is placed outside the housing 40. In this case, each protrusion 70 has the form of a frustoconical stud. The first protrusions may be identical.

[0093] In the example considered, each phase connector 60 comprises an insulating portion 72 and a conductive portion 73. The insulating portion 72 contacts the fixing unit 65 and the conductive portion 73 contacts the surface of the phase track 61 to electrically connect the phase and the phase track 61. The conductive portion does not contact the fixing unit 65.

[0094] In the example considered, an insulating layer 75 is provided between each phase track 60 and the base 41 to avoid electrical contact. The insulating layer may be mutual for all phases 60. The thickness of the insulating layer or layers 75 may be equal to 200 μm or less, in particular less than 150 μm.

[0095] In the example considered, each phase track 61 can be insulated relative to the fixing unit. Each phase track can be insulated by an insulating insert 76 surrounding the fixing unit 75. In this case, the insulating insert 76 is independent. Each insulating insert 76 is fitted in one of the openings 68 of the phase track 61.

[0096] As a variant, each insulating insert 76 may be integral with the insulating portion of the phase connection.Each insert may be an axial extension in the direction of the base.

[0097] As a variant, each insulating insert 76 may belong to the insulating layer. Each insert may be an axial extension in the direction of the phase connection.

[0098] Also as a variant, the fixing unit can be made of a non-conductive material, for example plastic.

Claims

1. An electronic module (36) for a rotating electrical machine (10), comprising: A housing (40) comprising a base (41); A power module assembly mounted on a base (41) of the housing, the assembly being capable of rectifying a multi-phase current system obtained from the phases of the stator of the motor and being capable of optionally supplying power to the phases of the stator in the multi-phase current system; a positive terminal (43) and a negative terminal (44) for supplying current to the power module assembly, the positive terminal being electrically connected to the power module assembly via a positive trace (45) disposed spaced apart from the base of the housing, and the negative terminal being electrically connected to the power module assembly via a negative trace (46) disposed spaced apart from the base of the housing, The invention is characterized in that the negative trace and the positive trace at least partially overlap each other, the housing (40) includes a generally cylindrical wall (54) extending from the base (41), the positive terminal and the negative terminal are arranged in a first area of ​​the wall, the positive trace (45) extends from the first area to a second area of ​​the wall, and the negative trace (46) extends from the first area to a third area of ​​the wall spaced apart from the second area.

2. The electronic module (36) according to claim 1, characterized in that The positive trace (45) and the negative trace (46) overlap over more than half the length of one of the two traces.

3. The electronic module (36) according to claim 1 or 2, characterized in that The positive trace (45) is placed axially between the base (41) and the negative trace (46).

4. The electronic module (36) according to claim 1 or 2, characterized in that One of the two positive and negative traces is curved and the other is straight.

5. The electronic module (36) according to claim 1 or 2, comprising a plurality of phase connectors (60), each connectable to a stator phase, and for each phase connector (60), the power module assembly comprises at least one positive module electrically connected to the positive terminal and the phase connector, and at least one negative module electrically connected to the negative terminal and the phase connector.

6. The electronic module (36) according to claim 5, comprising a second positive trace and a second negative trace mounted on the base (41) and electrically insulated relative to the base, the second positive trace electrically connecting the positive trace (45) and some or all positive power modules, and the second negative trace (46) electrically connecting the negative trace and some or all negative power modules.

7. The electronic module according to claim 5, comprising, for each phase connection (60), a phase trace mounted on the base so as to electrically connect the phase connection and the power module associated with the phase connection.

8. The electronic module (36) according to claim 1 or 2, comprising a control unit for controlling the power module assembly, the housing comprising a cover parallel to the base, a recess being provided in the cover, the control unit being placed in the recess.

9. The electronic module (36) according to claim 2, wherein: The positive trace (45) and the negative trace (46) overlap over more than 75% of the length of one of the two traces.

10. The electronic module (36) according to claim 2, wherein: The positive trace (45) and the negative trace (46) overlap over more than 90% of the length of one of the two traces.

11. The electronic module (36) according to claim 5, comprising three phase connections.

12. A rotating electrical machine (10), comprising: a stator (15), the rotation of which is fixed, comprising a plurality of phases; a rotor (12) rotatable about an axis of rotation (X); And an electronic module (36) according to any one of claims 1 to 8, the electronic module being fixed relative to the stator.

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