EP3602755A1

EP3602755A1 - Rotating electrical machine with optimised arrangement

Info

Publication number: EP3602755A1
Application number: EP18712219.7A
Authority: EP
Inventors: Radu Fratila; Jérome Legranger; Radhouane KHLISSA
Original assignee: Valeo Equipements Electriques Moteur SAS
Current assignee: Valeo Equipements Electriques Moteur SAS
Priority date: 2017-03-29
Filing date: 2018-03-22
Publication date: 2020-02-05
Also published as: FR3064834B1; CN110462996A; KR102362548B1; FR3064834A1; WO2018177896A1; US20210111614A1; KR20190120336A; JP2020512806A

Abstract

The invention relates mainly to a rotating electrical machine of a motor vehicle, comprising a rotor (12) having an axis (X) comprising at least one permanent magnet (20) and a stator (11) surrounding the rotor and comprising a body (24) provided with a plurality of slots (30) and an electrical winding (25), the winding comprising phase windings (26) arranged in the slots, each phase winding being formed by at least one conductor (35). The rotor (12) comprises 3, 4 or 5 pairs of poles. The stator comprises two three-phase systems, each formed by three delta connected phase windings (26). The number of conductors (35) per slot (30) is strictly greater than 2 and each conductor has an active portion (40) inserted in a corresponding slot (30), the active portion with a substantially rectangular section being of a radial length (L2) smaller than or equal to 3.6 mm.

Description

ROTARY ELECTRICAL MACHINE WITH OPTIMIZED CONFIGURATION

The present invention relates to a rotating electrical machine with optimized configuration. The invention finds a particularly advantageous, but not exclusive, application with high power reversible electrical machines that can operate in alternator mode and in motor mode coupled with a host element, such as a gearbox.

In known manner, the rotating electrical machines comprise a stator and a rotor secured to a shaft. The rotor may be integral with a driving shaft and / or driven and may belong to a rotating electrical machine in the form of an alternator, an electric motor, or a reversible machine that can operate in both modes. In alternator mode, when the rotor is rotating, it induces a magnetic field to the stator which transforms it into electric current to power the vehicle's electrical consumers and recharge the battery. In motor mode, the stator is electrically powered and induces a magnetic field driving the rotor in rotation to starter the engine and / or participate in the traction of the vehicle, independently or in combination with the engine.

The stator is mounted in a housing configured to rotate the shaft on bearings by bearings. Furthermore, the stator comprises a body consisting of a stack of thin sheets forming a ring, whose inner face is provided with notches open inward to receive an electrical coil formed by phase windings. These windings pass through the notches of the stator body and form buns protruding from both sides of the stator body. The phase windings are obtained for example from a continuous wire covered with enamel or from conductive elements in the form of pins connected together by welding. These windings are polyphase windings connected in star or delta whose outputs are connected to an inverter also operating as a bridge rectifier.

With this type of machine, the speed of rotation of the machine affects the voltage supplied and thus the power of the machine. So, the faster the speed rotation is high and the power is important. For synchronous machines, beyond a certain speed of rotation to maximize the power of the machine, it is important to be able to deflux the machine. FIG. 1 represents characteristic curves of torque and power as a function of the rotational speed of such a rotating electrical machine respectively in the motor mode M_mth (see characteristic curve of torque C1 and power characteristic curve C2) and in FIG. generator mode M_gen (see characteristic curve of torque C3 and power characteristic curve C4). A defluxing range P_def is defined by reference to a ratio between a maximum rotation speed at constant torque N1 divided by the maximum rotational speed N2 of the electric machine. This defluxing ratio being high (greater than 2.5), the machine can operate at high speed while being in a state of quasi-short circuit. In order to optimize the operation of the machine, in particular to achieve high operating speeds and therefore high power, it is necessary that the machine has a good steady state short-circuit current. This optimization of the machine must also take into account other parameters such as the compactness of the machine which is an important parameter for the integration of said machine into the vehicle, as well as the thermal behavior of the machine which is also a parameter important both for the safety of the users and not to damage the machine. The invention therefore aims to guarantee the holding of the short-circuit current in steady state while optimizing the compactness and the thermal characteristics of the electric machine.

To this end, the present invention relates to a rotating electric machine of a motor vehicle. According to the invention, the machine comprises a rotor extending along an axis of rotation and comprising at least one permanent magnet and a stator surrounding the rotor and comprising a body provided with a plurality of notches and an electric winding, the winding comprising phase windings arranged in the notches, each phase winding being formed by at least one conductor. In addition according to the invention, the rotor comprises 3 or 4 or 5 pairs of poles and the stator comprises two three-phase systems each formed by three coupled phase windings. in triangle. In addition according to the invention, the number of conductors per notch is strictly greater than 2 and each conductor has an active portion inserted into a corresponding notch, the active portion of substantially rectangular section having a radial length less than or equal to 3.6 mm.

Having two three-phase systems simplifies the arrangement of the power modules and thus allows to have a machine that can be more compact. In addition, the coupling of the windings in a triangle makes it possible to have no neutral point and thus improves the compactness of the machine. The fact of having a substantially rectangular section of wire makes it possible to improve the coefficient of filling of the conductors in the notches and thus to improve the power of the machine. By substantially rectangular section is meant that the corners of the conductors may be slightly rounded for manufacturing issues. A number of conductors per notch strictly greater than two allows to have a greater degree of latitude in terms of choice of the number of turns per winding. In addition, the fact that the radial width of the conductors is less than or equal to 3.6 mm associated with a number of pairs of rotor poles of between 3 and 5 makes it possible to minimize the resistance of the conductors, thereby limiting the Joule losses of the conductors. All these parameters taken together therefore lead to a better thermal resistance, a better resistance of the short-circuit current in steady state and a better compactness of the rotating electrical machine. The rotating electrical machine can thus operate at a higher speed in a secure manner. In one embodiment, the two three-phase systems are independent of one another and the rotating electrical machine comprises an inverter comprising two independent modules each connected to a three-phase system.

In one embodiment, the inverter is connected to a DC bus having a voltage of between 30 and 60 volts. According to one embodiment, an orthoradial length of an active portion of a conductor is greater than or equal to 1 .4 mm. According to one embodiment, an outer diameter of the stator body is between 80 mm and 180 mm. For example, the outer diameter of the stator body is selected from one of the following values: 80, 90, 100, 110, 153, 161 and 180 millimeters. According to one embodiment, a maximum power of said rotary electrical machine is between 8 kW and 30 kW.

In one embodiment, the number of conductors per slot is even.

According to one embodiment, the number of conductors per notch is 4. Alternatively, the number of conductors per notch may be equal to 6, 8 or 10.

In one embodiment, the conductors are aligned radially with each other within a corresponding notch.

According to one embodiment, each phase winding is formed from a plurality of conductors in particular in the form of pins electrically connected to each other. For example, the pins extend in the form of a U comprising two active parts extending in respective notches and a connecting portion connecting the two active parts. Preferably, a phase winding is formed by welding together the free ends of the active parts of different pins. By free ends is meant the ends of the active parts that are not connected to the connecting portion.

In one embodiment, each phase winding is formed from a continuous conductor. This continuous conductor is for example a wire.

According to one embodiment, the conductive wire comprises active portions of substantially rectangular section and connecting portions between two adjacent active portions of rounded section, in particular substantially round.

In one embodiment, the conductors have a rectangular section with rounded corners. In one embodiment, said rotating electrical machine comprises a coolant circuit.

In one embodiment, the machine is a synchronous machine.

In one embodiment, the machine is a permanent magnet machine. In one embodiment, said rotating electrical machine takes the form of a motor, a generator, or a reversible electric machine.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given for illustrative but not limiting of the invention. FIG. 1, already described, shows the characteristic curves of torque and power as a function of the speed of rotation of a rotating electrical machine used in the context of the invention.

Figure 2 is a longitudinal sectional view of a rotating electrical machine according to an exemplary embodiment of the present invention. FIG. 3 is a perspective view of the wound stator and the rotor of the rotary electric machine of FIG.

Fig. 4 is a partial cross-sectional view of the rotor and wound stator according to an exemplary embodiment of the present invention.

FIG. 5 shows graphical representations of the evolution of the ratio between the resistance of a high frequency electric stator conductor and the resistance of a low frequency electric stator conductor as a function of the radial dimension of an active portion of a stator conductor respectively for a rotor with 3 and 5 pairs of poles.

FIG. 6 represents the evolution of the total axial height of the rotating electrical machine as a function of the number of pole pairs of the rotor.

Identical, similar or similar elements retain the same reference from one figure to another. In the remainder of the description, a "front" element is understood to mean an element situated on the side of the driving part such as on the side of the pinion carried by the machine shaft and by "rear" element an element situated on the side opposite to the axis of rotation X of the machine. FIG. 2 shows a rotating electrical machine 10 comprising a stator

1 1 polyphase surrounding a rotor 12 mounted on a shaft 13 extending along an axis X corresponding to the axis of the machine. The stator 1 1 surrounds the rotor

12 with presence of an air gap between the inner periphery of the stator January 1 and the outer periphery of the rotor 12. The stator January 1 is mounted in a housing 14 provided with a front bearing 15 and a rear bearing 16 bearing rotatably the tree 13.

This electric machine 10 may be intended to be coupled to a gearbox belonging to a motor vehicle traction chain. In another configuration, the electric machine 10 may be coupled to a crankshaft of the vehicle or directly to the wheel drive chain of the vehicle. For example, the machine 10 may be coupled to a portion of the vehicle by a pinion 17 as shown in Figure 2. Alternatively, the machine 10 may be coupled to a portion of the vehicle by a pulley or other coupling means.

The machine 10 is able to operate in an alternator mode to supply, in particular, energy to the battery and to the on-board vehicle network, and in a motor mode, not only to start the engine of the vehicle, but also to participate in pulling the vehicle alone or in combination with the engine. Alternatively, the electric machine 10 may be implanted on a motor vehicle axle, in particular a rear axle. Alternatively, the electric machine 10 takes the form of an electric motor or a non-reversible generator. The power of the electric machine 10 is advantageously between 8kW and 30kW.

In the example of Figure 2, the rotor 12 comprises a body 19 in the form of a package of sheets. Permanent magnets 20 may be implanted inside cavities 21 in a V-shaped configuration, as shown in FIG. 4, or may be implanted radially inside the pack of sheets, the lateral faces two consecutive magnets can be be the same polarity, as shown in Figure 3. The rotor 12 is then the flux concentration type. Alternatively, the permanent magnets 20 extend ortho-radially inside the cavities 21 of the body 19. The magnets 20 may be of rare earth or ferrite depending on the applications and the desired power of the machine 10.

Moreover, as can be seen in FIGS. 3 and 4, the stator 1 1 comprises a body 24 constituted by a bundle of sheets and an electric coil 25. The body 24 is formed by a stack of sheets of independent sheets from each other and held in pack form by means of a suitable fastening system. As can be seen in FIG. 4, the body 24 is provided with teeth 28 delimiting two by two notches 30 for mounting the stator winding 25. Thus, two successive notches 30 are separated from each other by a tooth 28. Preferably , an outer diameter L1 of the stator body 24 is between 80 and 180mm. Advantageously, the outside diameter L 1 of the stator body 24 is selected from one of the following values: 80, 90, 100, 1 10, 153, 161 and 180 mm.

The coil 25 comprises a set of phase windings 26 passing through the notches 30 and forming bunches 33 projecting on either side of the stator body 24, as shown in FIGS. 2 and 3. The outputs of the phase windings 26 are connected to an inverter 34 which can also operate as a rectifier bridge. For this purpose, the inverter 34 comprises power modules provided with power switching elements, such as MOS transistors, connected to the phase outputs.

Each phase winding 26 may be formed from a plurality of conductors 35 constituted by pins 37. These pins 37 may have a U-shaped whose ends of the branches are interconnected for example by welding. Alternatively, each phase winding 26 is formed from a continuous conductive wire wound inside the stator January 1 in the notches 30 to form one or more turns. In all cases, there are active portions 40 of a conductor 35 located inside the notches 30 and connecting portions 41 interconnecting two active portions 40 adjacent. The active portions 40 thus correspond to the portions of the conductors 35 extending axially inside the notches 30, while the connecting portions 41 extend circumferentially inside the buns 33 to interconnect the active portions 40. The conductors 35 may for example be made of a material based on enamelled copper.

The phase windings 26 are each associated with a series of notches 30, so that each notch 30 receives several times the conductors 35 of the same phase. Advantageously, the stator January 1 comprises two three-phase systems, preferably independent, A1, B1, C1 and A2, B2, C2 each formed by three phase windings 26, as shown in Figure 4. This ensures the compactness of the inverter 34 by facilitating the arrangement of the power modules of the inverter 34 in a cylinder located at the rear of the machine for the integrated systems (see Figure 2) or in a substantially parallelepipedic space on the side of the machine 10.

Each three-phase system A1, B1, C1; A2, B2, C2 is coupled in a triangle to optimize the compactness of the electrical machine 10. In fact, compared to a double star type coupling, the double-triangle coupling makes it possible to avoid the integration of the neutral bars into the wound stator 1 1 which are relatively bulky.

Each three-phase system A1, B1, C1; A2, B2, C2 is electrically connected to a module independent of the inverter 34. Each independent module comprises power elements and a control module dedicated to the corresponding three-phase system. The two independent modules are housed in the same housing of the inverter 34 covering the rear bearing. The inverter 34 is preferably connected to a DC bus having a voltage of between 30 and 60 volts.

In this example, two consecutive notches of a series associated with one phase are separated by adjacent notches 30 each corresponding to another series of notches associated with one of the other phases. Thus, when there are K phases, the conductors 35 of the same phase winding 26 are inserted every K + 1th notches. For example, if the winding of the phase A1 is inserted into the notch 1, it is then inserted into the 7th notch for a machine with two three-phase systems, ie K = 6. It should be noted that in the configuration shown in FIG. 4, the phases of the two systems are alternated according to the circumference of the stator 11. In this example, considering the circumferential direction, the first notch comprises the phase A1, the second notch comprises the phase A2, the third notch comprises the phase B1, the fourth notch comprises the phase B2, the fifth notch comprises the phase C1 and the sixth notch includes phase C2. In an alternative embodiment another phase configuration can be envisaged.

The conductors 35 advantageously have a substantially rectangular section at least in their active portion 40 and are aligned radially with respect to each other within the corresponding notch 30. Such a winding configuration stored with conductors 35 of substantially rectangular section reduces the height of the buns 33 and promotes the compactness of the machine with respect to a random winding round wire. According to a particular embodiment of continuous wire winding, the conductive son may be stamped only in the active portions 40 and have a round section in the connecting portions 41. The substantially rectangular section of the active portions 40 may have rounded corners so as not to damage the enamel. Alternatively, the conductors 35 may have a substantially square section.

The number of conductors 35 inside each notch 30 is advantageously strictly greater than two in order to have a degree of freedom in terms of choice of the number of turns per phase winding 26. Preferably, the number of conductors 35 by notch is even. It is here equal to 4 but could alternatively be different, and especially equal to 6, 8 or 10. At high electrical frequency and therefore at high rotational speed, the conductors 35 are subjected to film and proximity effects which lead to make the current density in the conductor 35 non-uniform. This results in an increase in the apparent resistance of the It is customary to quantify this increase in resistance by a ratio between the high frequency resistance AC and the DC resistance of the same conductor 35 at a very low frequency of a few Hertz.

The electrical resistance therefore depends on the temperature, the dimensions of the stator 1 1, the dimensions of the conductors, and the electric frequency fe, which is related to the speed of rotation N in revolutions per minute of the machine by the following formula: = (Nxp) / 60, where p is the number of pole pairs of the rotor 12.

Increasing this resistance produces additional joules losses and involves increasing the size of the electrical machine 10 in order to be able to evacuate the calories, for example by increasing the size of a coolant chamber 44 described in more detail. below.

The main factor influencing the resistance AC is the radial length L2 of the conductor 35 inside the notch 30, as well as the electric frequency fe linked to the polarity of the rotor 12 for the same speed of rotation.

FIG. 5 represents, for an electrical machine 10 having a stator diameter L1 of the order of 160 mm and a rotational speed of 20000 revolutions / min, the evolution of the ratio between the resistance AC of a stator conductor at high frequency and the DC resistance of this low frequency stator conductor as a function of the radial length L2 of the active portion 40 of a conductor 35 respectively for a rotor with 3 pole pairs (see curve C5) and 5 pairs of poles (see curve C6).

It emerges that, for a given limit Lim of evacuable losses by the electrical machine 10, the maximum radial length L2 of the conductor 35 is 3.6 mm for a machine with five pairs of poles. Such a value guarantees a suitable behavior for a machine with three pairs of poles whose AC / DC ratio is generally lower than that of the machine with five pairs of poles. Moreover, the orthoradial length L3 of an active portion 40 is greater than or equal to 1 .4 mm. This length L3 has little effect on the AC resistance of the conductors 35. Indeed, as can be seen in FIG. 5 by the various points C7, for a given radial length L2 and by varying the orthoradial length L3 of the conductors 35, the value of the AC / DC ratio varies only very slightly. FIG. 6 represents the evolution of the total axial height L4 of the stator 1 1 of the electric machine 10 (see FIG. 2) as a function of the number of pairs of poles p of the rotor 12. By axial height is meant the distance between the two ends of the front and rear buns 33. This figure shows that a rotor 12 having less than three pairs of poles leads to increase the total height L4 of the machine, since the height of the buns 33 is substantially proportional to the polarity. Indeed, the fewer poles in the machine and the greater the distance between the poles. Thus, the notches traversed by the same phase winding are further apart from each other and the portions of the conductors forming the buns must therefore be larger. On the contrary, a polarity of more than five pairs of poles generates too many losses. Under these conditions, the optimum polarity is between 3 and 5 pairs of poles, that is to say that the rotor 12 may comprise 3 or 4 or 5 pairs of poles.

The rotating electrical machine 10 may comprise a coolant circuit having an inlet and a liquid cooling outlet for circulating the liquid in a chamber 44 arranged at the outer periphery of the stator January 1, as shown in FIG. electrical 10 may be cooled by water or oil. In an alternative embodiment, the machine can be cooled by air, for example by means of a fan.

Of course, the foregoing description has been given by way of example only and does not limit the scope of the invention which would not be overcome by replacing the different elements by any other equivalent.

In addition, the various features, variations, and / or embodiments of the present invention may be associated with each other in various combinations, to the extent that they are not incompatible or exclusive of each other.

Claims

1. Rotating Electric Motor Vehicle Machine Featuring

a rotor (12) extending along an axis of rotation (X) comprising at least one permanent magnet (20), and

a stator (1 1) surrounding the rotor and comprising a body (24) provided with a plurality of notches (30) and an electric winding (25), the winding (25) comprising phase windings (26) arranged in the notches (30), each phase winding (26) being formed by at least one conductor (35),

the machine being (10) characterized in that:

the rotor (12) has 3 or 4 or 5 pairs of poles,

the stator (1 1) comprises two three-phase systems (A1, B1, C1, A2, B2, C2) each formed by three phase windings (26) coupled in a triangle,

- The number of conductors (35) per notch (30) is strictly greater than 2 and each conductor (35) has an active portion (40) inserted in a corresponding notch (30), the active portion (40) of substantially rectangular section having a radial length (L2) less than or equal to 3.6 mm. 2. Rotating electrical machine according to claim 1, characterized in that the two three-phase systems are independent of one another and in that it comprises an inverter (34) comprising two independent modules each connected to a three-phase system ( A1, B1, C1, A2, B2, C2).

3. A rotary electric machine according to claim 2, characterized in that the inverter (34) is connected to a DC bus having a voltage of between 30 and 60 volts.

4. rotary electric machine according to any one of claims 1 to 3, characterized in that an orthoradial length (L3) of an active portion (40) of a conductor is greater than or equal to 1 .4 mm.

5. Rotating electric machine according to any one of claims 1 to 4, characterized in that an outer diameter (L1) of the stator body (24) is between 80 mm and 180 mm.

6. Rotating electric machine according to claim 5, characterized in that the outer diameter (L1) of the stator body (24) is selected from one of the following values: 80, 90, 100, 1 10, 153, 161 and 180 millimeters .

7. rotary electric machine according to any one of claims 1 to 6, characterized in that a maximum power of said rotating electrical machine (10) is between 8 kW and 30 kW.

8. rotary electric machine according to any one of claims 1 to 7, characterized in that the number of conductors (35) per notch (30) is even.

9. rotary electric machine according to claim 8, characterized in that the number of conductors (35) per notch (30) is equal to 4.

10. Rotating electrical machine according to any one of claims 1 to 9, characterized in that the conductors (35) are aligned radially relative to each other within a notch (30) correspondingly. 1 1. Rotary electric machine according to any one of claims 1 to 10, characterized in that each phase winding (26) is formed from a plurality of conductors in particular in the form of pins (37) electrically connected to each other.

12. Rotating electric machine according to any one of claims 1 to 10, characterized in that each phase winding

(26) is formed from a continuous conductor.

13. A rotary electric machine according to any one of claims 1 to 12, characterized in that it takes the form of a motor, a generator, or a reversible electric machine.