Rotating polyphase electric machine with axial electromagnetic flux

Abstract

The rotating, polyphase, axially electromagnetic flux electric machine (2) comprises: - a rotor axially interposed between first and second stators (6, 7), each with N phases, each stator comprising a set of coils (12), each belonging to one of the N phases; - an interconnector comprising N annular busbars (14) supplying the N phases, at least one of the coils of each phase being connected to one of the busbars. The busbars are common to the first and second stators. (See Figure 6 for abbreviations)

Description

Title of the invention: Rotating polyphase electrical machine with axial electromagnetic flux Technical field of the invention

[0001] The present invention relates to a rotating, multiphase, axially driven electromagnetic flux electric machine. The invention also relates to a transmission module comprising an electric machine according to the invention and a mechanical reducer. Finally, the invention relates to a method for manufacturing an electric machine. Technical background

[0002] A polyphase rotating electrical machine used to convert electrical energy into mechanical energy in order, for example, to power a motor vehicle is known from the prior art. Typically, a rotating electrical machine is of either the axial electromagnetic flux type or the radial electromagnetic flux type. For example, in the case of an axial electromagnetic flux electrical machine, the machine comprises a rotor, generally disc-shaped, arranged between two stators, also generally disc-shaped. The stators have the same predetermined number of phases, and each stator comprises a set of coils, each connected to one of the phases. For each stator, the electrical machine includes an interconnector comprising a set of busbars for supplying electrical current to the stator coils. The number of busbars in each interconnector corresponds to the number of phases in the stator.

[0003] The use of two interconnectors and therefore two sets of busbars respectively for the two stators has the disadvantage of being bulky, costly and increasing the weight of the electrical machine. Summary of the invention

[0004] The invention thus aims in particular to provide an electrical machine that is less bulky, lighter and less expensive to manufacture.

[0005] To this end, the invention relates to a rotating, multiphase, axially electromagnetic flux rotating electrical machine comprising: - a rotor axially interposed between first and second stators, each with N phases, each stator comprising a set of coils, each belonging to one of the N phases, - an interconnector comprising N annular busbars supplying the N phases, at least one of the coils of each phase being connected to one of the busbars, characterized in that the omnibus bars are common to the first and second stators.

[0006] Sharing the bus bars, and therefore the interconnector, of the first and second stators makes it possible to retain only one set of bus bars, and therefore only one interconnector, in order to reduce the size of the electrical machine, as well as its weight and manufacturing cost.

[0007] The number of phases in the rotating electrical machine varies depending on the embodiment. For example, this number of phases is three in the case of a three-phase rotating electrical machine. Depending on the embodiment, the number of phases may be greater than three, for example, six, nine, or twelve.

[0008] The invention may include one or more of the following optional features, taken alone or in combination.

[0009] Advantageously, the rotating electrical machine further comprises at least one electrically insulating busbar bracing element for maintaining a predetermined axial spacing between the busbars. This bracing element allows, in a simple manner, the maintenance of a predetermined axial spacing between the busbars while electrically insulating them from each other. The electrically insulating bracing element can have different shapes depending on the embodiment. Preferably, this bracing element has a comb-like shape, the teeth of which, arranged between the busbars, allow the predetermined axial spacing between the busbars to be maintained.

[0010] Advantageously, each busbar includes common connection terminals for one of the coils of the first stator and one of the coils of the second stator. Using a common connection terminal for both stators reduces the overall size of the rotating electrical machine. Preferably, all the connection terminals of each busbar are common to one of the coils of the first stator and one of the coils of the second stator. This further reduces the overall size of the rotating electrical machine.

[0011] Advantageously, the connection terminals include a notch that defines a first connection level at one end of one of the coils of the first stator and a second connection level at one end of one of the coils of the second stator. This notch facilitates, in particular, the connection of the terminal to the ends of the coils of the first and second stators. More specifically, the presence of the notch facilitates the connection of the terminal to the end of one of the coils of the first stator by preventing the coil from being crushed against the terminal, for example, by allowing it to extend at least partially through the space formed by the notch. The first and second connection levels are axially offset.

[0012] Advantageously, the ends of the coils are arranged on the sides axial of the first and second stators which are opposite the rotor. Thus, the connection at the first and second level of connection is facilitated between a connection terminal and the end of one of the coils of the first stator and the end of one of the coils of the second stator.

[0013] According to one embodiment, the connection terminals and the ends of the coils of each stator are joined at the first and second levels of connection, in particular by welding. This provides a simple, stable, and reliable connection between the connection terminals and the coil ends. Furthermore, welding offers good vibration resistance properties.

[0014] Advantageously, each busbar includes a ring arranged around the first stator from which the connection terminals extend towards the second stator. This configuration reduces the overall size and facilitates the manufacturing process of the electric machine. It is understood, in particular, that no busbar includes a ring arranged around the second stator, thus freeing up space and lightening the electric machine.

[0015] According to one embodiment, the electric machine further comprises a first housing and a second housing, fixed together, in which the first and second stators, the rotor, and the interconnector are arranged. The interconnector and the first stator are fixed to the first housing, and the second stator is fixed to the second housing. The second housing includes access openings, with each connection terminal extending through one of the access openings. This facilitates the manufacturing process of the electric machine by allowing access to the connection terminals extending through one of the access openings when the first and second housings are fixed together.In particular, it is possible to easily achieve the fixing, for example by welding, between a connection terminal extending through an access opening and a coil end of the second stator also extending into this same access opening, when the two housings are fixed together, by maneuvering the necessary tools through the access opening.

[0016] According to one embodiment, the second housing comprises as many access openings as connection terminals. This results in a second housing with good mechanical resistance properties since the access openings are more numerous but smaller in size and separated by material contributing to the mechanical strength of the housing.

[0017] According to another embodiment, the second housing comprises fewer access openings than connection terminals. This results in a second, lighter housing since the access openings are larger to accommodate several connection terminals, thus reducing the total amount of material used to form the second housing.

[0018] Advantageously, the first housing carries a connector linked to a power supply terminal of each busbar, the power supply terminals extending in an axial direction opposite to the extension direction of the connection terminals. Such a configuration further reduces the overall size of the electrical machine.

[0019] The invention also relates to a transmission module comprising at least one electrical machine as described above and a mechanical reducer fixed to the electrical machine.

[0020] Advantageously, the transmission module comprises an electrical machine as described above comprising a first housing and a second housing, fixed to each other, in which are arranged the first and second stators, the rotor and the interconnector, the interconnector and the first stator being fixed to the first housing, the second stator being fixed to the second housing, the second housing comprising access openings, each connection terminal extending through one of the access openings, and in which the mechanical reducer comprises a housing fixed to the second housing, the housing and the second housing defining a fixing chamber around the access openings so as to isolate all the access openings from the outside of the transmission module.This configuration allows us to take advantage of the presence of access openings while simply isolating these access openings from the outside of the transmission module in order to guarantee the safe use of the transmission module.

[0021] The mounting chamber can be defined by the second housing and a cover fixed to the second housing. The casing may not be part of the definition of the mounting chamber.

[0022] Finally, the invention also relates to a method for manufacturing an electrical machine as described above comprising a first housing and a second housing, fixed together, in which are arranged the first and second stators, the rotor and the interconnector, the interconnector and the first stator being fixed on the first housing, the second stator being fixed on the second housing, the second housing comprising access openings, each connection terminal extending through one of the access openings, the manufacturing method comprising the following steps: - The first stator and the N busbars are arranged in the first box. - The second stator and rotor are arranged in the second housing, which includes access openings for the busbar connection terminals and the ends of the second stator coils. - the connection terminals of the bus bars are electrically connected to the ends of the coils of the second stator, for example by welding.

[0023] Alternatively, the rotor can be arranged on the first housing.

[0024] This method simplifies the manufacture of the electrical machine by facilitating the connection between the busbar connection terminals and the ends of the coils of the second stator. In particular, it is understood that the operations performed to make this connection can take place via the access openings. Brief description of the figures

[0025] The invention will be better understood upon reading the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which:

[0026] [Fig-1] is a perspective view of a transmission module according to the invention;

[0027] [Fig.2] is a perspective view of an electrical machine according to the invention, included in the transmission module of [Fig.1], for which the first and second boxes are detached and spaced apart from each other;

[0028] [Fig.3] is an exploded perspective view of the electrical machine of [Fig.2];

[0029] [Fig.4] is a perspective view of bus bars of an interconnector of the electrical machine of [Fig.2] for which one body of the interconnector is not shown;

[0030] [Fig.5] is a perspective view of part of the electrical machine of [Fig.2]; And

[0031] [Fig.6] is a perspective view of part of the electrical machine of the [Fig.2] on which a first and second housing of the electrical machine as well as the body of the interconnector are not shown. Detailed description

[0032] Figure 1 shows a transmission module 1 according to the invention, comprising in particular a rotating polyphase electric machine 2 and a mechanical reducer 3. According to the present embodiment, the transmission module 1 is intended to be mounted on a vehicle (not shown) in order to convert electrical energy into mechanical energy to drive the vehicle. The mounting of such a transmission module 1 on a vehicle is known per se and will not be described in further detail here. The transmission module 1 according to the invention can be used for applications other than driving a vehicle.

[0033] In the present case, the conversion of electrical energy into mechanical energy is carried out by the rotating electric machine 2, which is therefore used here as an electric motor. According to other embodiments, the rotating electric machine 2 of the invention can be used as a generator to convert mechanical energy into electrical energy.

[0034] According to the present embodiment, the electrical machine 2 includes in particular a first housing 4, a second housing 5, a first stator 6, a second stator 7, a rotor 8 and an interconnector 9.

[0035] The rotor 8 has a general disc shape and comprises permanent magnets 10 on each of its faces (Figures 2 and 3). The rotor 8 is free to rotate about the axis A of the electrical machine 2. The rotor 8 further comprises an axial shaft 11 for transmitting the rotational motion of the rotor 8 to the mechanical reducer 3.

[0036] The stators 6, 7 each have a general disk shape (see [Fig. 3]). The first and second stators 6, 7 each have a predetermined number N of phases. In the present embodiment, the first and second stators 6, 7 are three-phase, that is, they each have three phases. According to other embodiments, the number of phases may be different, for example, six, nine, or twelve. Each stator 6, 7 comprises a set of coils 12, each belonging to one of the three phases.

[0037] The rotor 8 is axially interposed between the first stator 6 and the second stator 7. In a conventional manner, when the three phases of the stators 6, 7 are supplied by an alternating electric current, an axially flux electromagnetic field is generated and, by acting on the permanent magnets 10 of the rotor 8, makes it possible to drive the rotor 8 in rotation, and therefore also to drive its axial shaft 11 in axial rotation.

[0038] The interconnector 9, also called the interconnecting element, allows the connection of the coils 12 of the stators 6, 7. It comprises an annular body 13 made, in this case, of plastic overmolded onto N annular busbars 14 supplying the N phases and onto an annular neutral bar 15. In this case, the interconnector 9 therefore comprises three busbars 14 supplying the three phases. In this embodiment, the coils 12 of each stator 6, 7 are electrically connected in a star configuration by the interconnector 9. Thus, each coil 12 is connected either to one of the busbars 14, or to another coil 12, or to the neutral bar 15. According to another embodiment, the electrical connection of the coils of each stator 6, 7 is achieved in a different configuration, for example, in a known delta configuration. At least some of the 12 coils can be connected in series.In all cases, at least one of the coils 12 of each phase is connected to one of the phase supply busbars 14.

[0039] Each busbar 14 comprises a ring of the same diameter arranged, in this case, around the first stator 6. Each busbar 14 further comprises connection terminals 16 common to one of the coils 12 of the first stator 6 and to one of the coils 12 of the second stator 7 ([Fig. 6]). These connection terminals 16 all extend axially in projection from an outer peripheral edge of the busbar rings towards the second stator 7 (see Figures 3, 4 and 6). Similarly, the neutral bar 15 comprises a ring, of the same diameter as those of the busbars 14, from which extend axially in projection neutral connection terminals 22 common to one of the coils 12 of the first stator 6 and to a coils 12 of the second stator 7 (see figures 3, 4 and 6).

[0040] The interconnector 9 further comprises several electrically insulating bracing elements 17 for the bus bars 14 and the neutral bar 15 so as to maintain a predetermined axial spacing between the bus bars 14 and each other and with the neutral bar 15. In this case, the electrically insulating bracing element 17 has a comb-like shape, the teeth of which, arranged between the bus bars 14 and the neutral bar 15, maintain a predetermined axial spacing between them ([Fig. 4]). According to the present embodiment, the interconnector 9 comprises six bracing elements 17 regularly spaced at angles. This number varies according to the embodiment and is, for example, between one and twenty, preferably between three and nine. It can be made of any material that allows it to perform both its bracing and electrical insulation functions. For example, it is made of plastic.

[0041] According to the invention, the electric machine 2 comprises a single interconnector 9, common to the two stators 6, 7. In other words, the bus bars 14 of the interconnector 9 are common to the first and second stators 6, 7. This advantageously reduces the weight, manufacturing costs and size of the electric machine 2.

[0042] In the present case, all the connection terminals 16 of the busbars 14 include a notch 18 which defines a first level of connection to one end 19 of one of the coils 12 of the first stator 6 and a second level of connection to one end 20 of one of the coils 12 of the second stator 7. The connection terminals 16 thus have a free end in the shape of an L. Alternatively, the connection terminals 16 could be provided without a notch and, for example, have a generally rectangular shape. Alternatively still, the connection terminals 16 could be provided with a through-hole defining a first level of connection with one end of one of the coils 12 of the first stator 6.

[0043] In the present case, each busbar 14 comprises six connection terminals 16 regularly spaced at an angle. The number of connection terminals 16 per busbar 14 varies depending on the embodiment and may be less than or greater than six. Furthermore, since the electrical connection is here in a star configuration, the neutral busbar 15 comprises eighteen neutral connection terminals 21 regularly spaced at an angle, i.e., one neutral connection terminal 21 for each connection terminal 16 of the busbars 14. The neutral connection terminals 21 have the same shape as the connection terminals 16 of the busbars 14; they therefore include a step 22 which also defines a first connection level at one end 19 of one of the coils 12 of the first stator 6 and a second connection level at one end 20 of one of the coils 12 of the second stator 7 (Figures 4, 5 and 6). [Fig. 6] shows that the ends 19, 20 of the coils 12 are arranged on the axial sides of the first and second stators 6, 7 which are opposite the rotor 8. This makes it possible to reduce the size of the electric machine 2 by allowing in particular the use of small connection terminals 16 of the bus bars 14 and small neutral connection terminals 21.

[0044] The connection terminals 16 and the ends 19, 20 of the coils 12 of each stator 6, 7 are joined at the first and second levels of connection. This joining is achieved, for example, by welding with or without filler material, such as electric or laser welding, or by any other means enabling electrical communication between the connection terminals 16 and the ends of the coils 12 of each stator 6, 7. In alternative embodiments, the joining is achieved by means of a clip.

[0045] The busbars 14 further each include a power supply terminal 25 connected to an electrical connector 26 for supplying alternating current. Each power supply terminal 25 extends axially from a peripheral edge of the ring of one of the busbars 14 in an axial direction opposite to the extension direction of the connection terminals 16. The three power supply terminals 25 are adjacent in order to optimize the overall dimensions and size of the electrical connector 26 ([Fig. 6]). The electrical connector 26 is supported by the first housing 4 and extends axially from an end face thereof so as to limit the radial dimensions of the electrical machine 2 (Figures 2 and 3).It is understood that using a single interconnector 9 advantageously allows for the use of a single electrical connector 26, which further reduces the overall size and allows, for example, the use of more cooling oil to contribute to the cooling of the electric machine 2. Furthermore, using a single electrical connector 26 is economical. Finally, using a single electrical connector 26 frees up space in the housings 4, 5, which notably allows for better control of the air gap between the rotor 8 and the stators 6, 7.

[0046] The first housing 4 and the second housing 5 are fixed together, for example by screwing. The first and second stators 6, 7, the rotor 8 and the interconnector 9 are arranged in these first and second housings 4, 5. More specifically, the interconnector 9 and the first stator 6 are fixed to the first housing 4 and the second stator 7 is fixed to the second housing 5.

[0047] Each of the first and second housings 4, 5 has a general circular shape, comprising protrusions extending radially outwards from a circumferential edge of the housing, these protrusions being used for screw fixing between the first and second housings 4, 5.

[0048] The second housing 5 includes access openings 23, each terminal of connection 16 and each neutral connection terminal 21 extend through one of the access openings 23 ([Fig. 5]). Thus, these access openings 23 allow, during the manufacture of the electrical machine 2, access to the connection terminals 16 of the busbars 14 and to the neutral connection terminals 21 after the two parts of the housing 4, 5 have been fixed together. In this way, a person skilled in the art can easily proceed to secure, for example by welding, the ends 19, 20 of the coils 12 to the connection terminals 16 or the neutral connection terminals 21.

[0049] According to the embodiment presented, the second housing 5 comprises as many access openings 23 as there are connection terminals 16 of the busbars and neutral connection terminals 21 of the neutral busbar 15. In other words, the second housing 5 comprises two access openings 23 per coil 12. Reinforcing ribs 24 are present between some of the access openings 23 in order to improve the mechanical resistance of the housing, which is reduced by the presence of the access openings 23. The number of access openings 23 varies according to the embodiment. For example, according to one embodiment, the second box 5 includes as many access openings 23 as there are coils 12. In this case, it can be provided that a connection terminal 16 of an omnibus busbar 14 and an adjacent neutral connection terminal 21 extend into the same access opening 23.Furthermore, it can be anticipated that two or more of the coils 12 are connected in series, which reduces the number of connection terminals 16 required and therefore reduces the number of access openings 23 required.

[0050] The second housing 5 further includes an axial opening allowing the passage of the axial shaft 11 of the rotor 8 (figures 2 and 3) in order to transmit the rotational movement of the rotor 8 to the mechanical reducer 3.

[0051] The first housing 4 is blind or closed by a position sensor of the axial shaft 8. The axial shaft is carried by the first housing by means of a bearing.

[0052] The interconnector 9, in particular the body of the interconnector 13, has fixing openings on the first housing.

[0053] The mechanical reducer 3 comprises a housing 27 fixed to the second housing 5, for example by screwing ([Fig. 1]). The housing 27 and the second housing 5 define a mounting chamber around the access openings 23 so as to isolate all the access openings 23 from outside the transmission module 1. This mounting chamber is isolated from the rest of the mechanical reducer 3. The mounting chamber is isolated from the rest of the mechanical reducer by a contact, in particular a planar-to-planar contact, to which a seal may be added, between the second housing 5 and the housing 27. Active parts of the mechanical reducer on the one hand, and on the other hand, the rotor 8, the first stator 6, and the second stator 7, are not in fluidic contact. Thus, the machine electrical 2 allows both simplified assembly thanks to the presence of access openings 23 while maintaining good safety conditions simply by isolating these access openings from outside the transmission module 1 thanks to the housing 27 of the mechanical reducer 3.

[0054] A method for manufacturing the electrical machine 2 as described above is described below.

[0055] The manufacturing process comprises the following steps:

[0056] - The first stator 6, the three omnibus bars 14 and the neutral bar 15 are arranged in the first housing 4. The fixing of these various elements in the first housing 4 can be carried out using standard methods. As for the interconnector 9, it is advantageous to screw it to the first housing 4 by screwing directly through the body 13 of the interconnector. Alternatively, the interconnector 9 can be glued to the first housing 4.

[0057] - The second stator 7 and the rotor 8 are arranged in the second housing 5 comprising the access openings 23. The second stator 7 is arranged in the second housing 5 so that the ends 20 of the coils 12 of the second stator 7 extend respectively into one of the access openings 23.

[0058] - The ends 19 of the coils 12 of the first stator 6 are electrically connected to connection terminals 16 of the busbars 14 or to the neutral connection terminals 21 of the neutral busbar 15. The ends of the coils 19 of the coils 12 are connected to the connection terminals 16, 21 at the respective notches 18, 22 of the latter ([Fig. 6]). This connection is made, for example, by welding.

[0059] - The second housing 5 is attached to the first housing 4, the second housing being arranged so that, in a given access opening 23, extend both a connection terminal 16 of a busbar 14 or a neutral connection terminal 21, an end 19 of a coil 12 of the first stator 6 and an end 20 of a coil 12 of the second stator 7 ([Fig.5]).

[0060] - The connection terminals 16 of the bus bars 14 and the Neutral connection terminals 21 of the neutral bar 15 to the ends 19, 20 of the coils of the second stator 7, for example by welding. The presence of access openings 23 allows this welding operation to be carried out via these access openings 23, after the second housing 5 has been fixed to the first housing 4, thus enabling a simpler and more precise assembly of the electrical machine 2.

[0061] In order to manufacture the transmission module 1, the housing 27 of the mechanical reducer 3 is then fixed to the second housing 5 as previously indicated, i.e. by defining together a fixing chamber around the access openings 23 so as to isolate all the access openings 23 from the outside of the transmission module 1.

[0062] The invention is not limited to the embodiments presented, and other embodiments will be obvious to those skilled in the art. In particular, those skilled in the art will easily be able to adapt the characteristics of the three-phase electrical machine as described in this embodiment to an electrical machine comprising a different number of phases, for example, a six-phase electrical machine. List of references

[0063] 1: transmission module 2: electrical machine 3: Mechanical reducer 4: First case 5: Second case 6: first stator 7: second stator 8: rotor 9: interconnector 10: permanent magnet 11: rotor axial shaft 12: coil 13: Interconnector body 14: omnibus bars 15: neutral bar 16: Connection terminals 17: Electrically insulating bracing element for bus bars 18: Disconnection of a busbar connection terminal 19: end of a coil of the first stator 20: end of a coil of the second stator 21: Neutral connection terminal 22: Neutral connection terminal disconnection 23: Access opening 24: Reinforcing rib 25: power supply terminal 26: electrical connector 27: crankcase

Claims

Claims

1. Polyphase rotating electrical machine (2) with axial electromagnetic flux comprising: - a rotor (8) axially interposed between first and second stators (6, 7) with N phases each, each stator (6, 7) comprising a set of coils (12) each belonging to one of the N phases, - an interconnector (9) comprising N annular bus bars (14) for supplying the N phases, at least one of the coils (12) of each phase being connected to one of the bus bars (14), characterized in that the bus bars (14) are common to the first and second stators (6, 7).

2. An electrical machine (2) according to claim 1, further comprising at least one electrically insulating spacer member (17) for the bus bars (14) so as to maintain a predetermined axial spacing between the bus bars (14).

3. An electrical machine (2) according to claim 1 or 2, wherein each bus bar (14) comprises connection terminals (16) common to one of the coils (12) of the first stator (6) and to one of the coils (12) of the second stator (7).

4. Electrical machine (2) according to the preceding claim, in which the connection terminals (16) comprise a step (18) which defines a first connection level at one end (19) of one of the coils (12) of the first stator (6) and a second connection level at one end (20) of one of the coils (12) of the second stator (7).

5. Electrical machine (2) according to the preceding claim, in which the ends (19, 20) of the coils (12) are arranged on the axial sides of the first and second stators (6, 7) which are opposite the rotor (8).

6. Electrical machine (2) according to claim 4 or 5, in which the connection terminals (16) and the ends (19, 20) of the coils (12) of each stator (6, 7) are secured at the first connection level and at the second connection level, in particular by welding.

7. An electrical machine (2) according to any one of claims 3 to 6, wherein each bus bar (14) comprises a ring arranged around the first stator (6) from which the connection terminals (16) extend towards the second stator (7).

8. Electrical machine (2) according to any one of claims 3 to 7, further comprising a first housing (4) and a second housing (5), fixed together, in which the first and second stators (6, 7), the rotor (8) and the interconnector (9) are arranged, the interconnector (9) and the first stator (6) being fixed to the first housing (4), the second stator (7) being fixed to the second housing (5), the second housing (5) comprising access openings (23), each connection terminal (16) extending through one of the access openings (23).

9. Electrical machine (2) according to the preceding claim, in which the first housing (4) carries a connector (26) connected to a power supply terminal (25) of each bus bar (14), the power supply terminals (25) extending in an axial direction opposite to the direction of extension of the connection terminals (16).

10. Transmission module (1) characterized in that it comprises at least one electrical machine (2) according to any one of the preceding claims and a mechanical reducer (3) fixed to the electrical machine (2).

11. A transmission module (1) according to the preceding claim, comprising an electrical machine (2) according to claim 8 or 9, wherein the mechanical reducer (3) comprises a casing (27) fixed to the second housing (5), the casing (27) and the second housing (5) defining a fixing chamber around the access openings (23) so as to isolate all the access openings (23) from the outside of the transmission module (1).

12. A method of manufacturing an electrical machine (2) according to claim 8 or 9, characterized in that it comprises the following steps: - arranging the first stator (6), and the N bus bars (14) in the first housing (4), - arranging the second stator (7) and the rotor (8) in the second housing (5) comprising the access openings (23) to the connection terminals (16) of the bus bars (14) and to the ends (19, 20) of the coils (12) of the second stator (7), - electrically connecting the connection terminals (16) of the bus bars (14) to the ends (20) of the coils (12) of the second stator (7), for example by welding.

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