FR3084793A1 - ROTATING ELECTRICAL MACHINE HAVING A WINDING WITH OPTIMIZED CONFIGURATION - Google Patents

Abstract

The invention relates mainly to a rotary electrical machine in particular for a motor vehicle, comprising: - a rotor with permanent magnets, - a stator provided with a winding (16) comprising a plurality of phases each formed by windings (A1 -A2, B1 -B2, C1 -C2), characterized in that said rotary electrical machine further comprises: - a first power inverter (24.1) comprising a plurality of bridge arms (BP1-BP3), - a second power inverter ( 24.2) comprising a plurality of bridge arms (BP1'-BP3 '), - and in that at least one group of two windings (A1-A2, B1-B2, C1-C2) of one phase has one end connected to a bridge arm (BP1-BP3) of the first power inverter (24.1) and one end connected to a bridge arm (BP1'-BP3 ') of the second power inverter (24.2).

Description

ROTATING ELECTRIC MACHINE WITH AN OPTIMIZED CONFIGURATION COIL

The invention relates to a rotary electrical machine provided with an optimized configuration winding. The invention finds a particularly advantageous, but not exclusive, application with rotary electrical machines used in motor vehicles, in particular of the electric or hybrid type, for which optimum efficiency is sought over a large range of rotational speeds.

In a manner known per se, rotary electrical machines comprise a stator and a rotor secured to a shaft. The rotor may be integral with a driving and / or driven shaft and may belong to a rotating electrical machine in the form of an alternator, an electric motor, or a reversible machine capable of operating in both modes.

In the case of an electric machine of the synchronous type, the rotor comprises a body formed by a stack of sheets of sheets as well as poles formed by permanent magnets.

Furthermore, the stator is mounted in a casing configured to rotate the rotor shaft, for example by means of bearings. The stator comprises a body provided with a plurality of teeth defining notches, and a winding inserted in the notches having a plurality of phases.

Rotating electric machines with permanent magnets have the advantage of having a high torque density, a high efficiency, a high power factor and a compact structure, in particular when permanent magnets are used of rare earths generating an intense magnetic field.

However, the magnetic field produced by the permanent magnets is constant, so that a defluxing current is necessary to operate the electric machine beyond its nominal speed. This reduces efficiency and the power factor in areas of operation at high rotational speed.

The presence of permanent magnets, a continuously excited winding to generate the defluxing current, and an alternately excited winding makes the topology of the electric machine quite complex. In addition, manufacturing and assembly are generally difficult and time-consuming to perform, which has limited the industrial applications of this type of rotary electrical machine.

The invention aims to propose a new configuration of rotary electrical machine having a simple structure making it possible to maintain a high level of torque over a large range of rotational speeds.

More specifically, the subject of the invention is a rotary electrical machine, in particular for a motor vehicle, comprising:

- a permanent magnet rotor,

- a stator provided with a winding comprising a plurality of phases each formed by windings, characterized in that said rotary electrical machine further comprises:

- a first power inverter comprising a plurality of bridge arms,

- a second power inverter comprising a plurality of bridge arms,

- And in that at least one group of two windings of a phase has one end connected to a bridge arm of the first power inverter and one end connected to a bridge arm of the second power inverter.

The invention thus makes it possible to simultaneously apply an alternating excitation and a continuous excitation to the winding so as to selectively increase the flux to maximize the torque of the electric machine at start-up, or reduce the flux of the electric machine in order to deflux the rotor at high speed. In addition, the stator notch openings can be increased, which facilitates the stator winding process.

According to one embodiment, a number of teeth of the stator is equal to 6 times k, k being an integer.

According to one embodiment, a number of poles of the rotor is different from 3 times k, k being an integer.

According to one embodiment, the rotor has a radial flow.

According to one embodiment, the rotor is with surface magnets.

According to one embodiment, the rotor is with buried magnets.

According to one embodiment, the rotor has two radial layers of permanent magnets.

According to one embodiment, a pole of the rotor is formed by at least two permanent magnets forming a non-zero angle between them.

According to one embodiment, an air gap extending between an external periphery of the rotor and an internal periphery of the stator is variable.

According to one embodiment, an external periphery of the permanent magnets has a domed shape.

According to one embodiment, an external periphery of portions of the rotor extending between the permanent magnets has a domed shape.

According to one embodiment, the winding is of the concentrated type.

According to one embodiment, the winding is formed from spools of continuous wire wound around teeth of the stator.

The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given only by way of illustration but in no way limit the invention.

Figure 1 is a cross-sectional view of a rotary electrical machine according to the invention;

Figure 2 is a schematic representation of the electrical connection of the winding of the electrical machine according to the invention to power inverters;

Figures 3 to 5 are cross-sectional views illustrating alternative embodiments of rotors of rotary electrical machines according to the present invention;

FIGS. 6a to 6c are representations of the distribution of the magnetic flux respectively for a zero continuous excitation current, a positive continuous excitation current, and a negative continuous excitation current;

FIG. 7a shows graphical representations of the counterelectromotive force as a function of the position of the rotor for different DC excitations of the winding;

Figure 7b shows the spectra corresponding to the different curves of Figure 7a;

FIG. 8 is a graphic representation of the evolution of the amplitude of the fundamental frequency of the counterelectromotive force as a function of a density of the continuous excitation current;

FIG. 9a shows graphical representations of the electromagnetic torque as a function of the position of the rotor for different excitations in direct current;

Figure 9b shows the spectra corresponding to the different curves of Figure 9a;

FIG. 10 is a graphical representation of the average torque as a function of copper losses for various direct current excitations;

FIG. 11 shows a 3D graphic representation of the average torque as a function of the total copper losses and of a ratio of the copper losses in direct current divided by the total losses;

FIG. 12 is a graphic representation of the average torque with respect to the total copper losses respectively without continuous excitation and with optimal continuous excitation;

Figures 13a and 13b are graphic representations of alternative embodiments of a variable gap rotor.

Identical, similar or analogous elements keep the same reference from one figure to another.

FIG. 1 shows a rotary electric machine 10 comprising a wound stator 11 of the polyphase type, surrounding co-axially a rotor 12 having an axis of rotation X corresponding to the axis of the machine. The stator 11 and the rotor 12 are separated from each other by a gap 13 extending between the external periphery of the rotor 12 and the internal periphery of the stator 11.

Furthermore, the stator 11 comprises a body 15 and a winding 16. The stator body 15 consists of an axial stack of flat sheets. The body 15 includes teeth 18 from a cylinder head 20 which are angularly distributed in a regular manner. These teeth 18 delimit notches 21, such that each notch 21 is delimited by two successive teeth 18. The notches 21 open axially into the axial end faces of the stator body 15 and are also open radially towards the inside of the stator body 15.

The coil 16 is advantageously of the concentrated type by being formed from coils 23 of continuous wire wound around teeth 18 of the stator 11. The coil wire is for example made of copper and covered with a layer of insulating material, such as enamel. The winding 16 comprises a plurality of phases formed by windings. For example, the winding 16 comprises a three-phase system formed by the windings A1-A2 for phase A, B1-B2 for phase B, and C1-C2 for phase C. Of course, the number of phases can be adapted by depending on the application.

As can be seen in Figure 2, a first power inverter

24.1 has a plurality of bridge arms BP1, BP2, BP3 and a second power inverter 24.2 has a plurality of bridge arms ΒΡΓ, BP2 ', BP3'.

A group of two windings of the same phase, respectively ΑΙΑΣ, B1-B2, and C1-C2, has one end connected to a bridge arm BP1-BP3 of the first power inverter 24.1 and one end connected to a bridge arm corresponding ΒΡΓ-ΒΡ3 'of the second power inverter 24.2. The connections are made between the switching elements of the bridge arms BP1-BP3; BP1 '-BP3'.

A BP1-BP3 bridge arm; ΒΡΓ-ΒΡ3 'is formed by two controlled switching elements, namely an IHS switching element (called High side in English) and an ILS switching element (said Low side in English) for selectively connecting one end of a group d '' windings at positive potential B + power supply to machine 10 or to earth. BP1-BP3 bridge arms; ΒΡΓ-ΒΡ3 'connected to the different phases of the electric machine are controlled by a control module. Each IHS and ILS switching element may consist of a power transistor, for example of the MOS type, preferably associated with a freewheeling diode.

As can be seen in FIG. 1, the rotor 12 of the salient pole type may include a body 26 formed by an axial stack of flat sheets in order to reduce the eddy currents as well as poles formed by permanent magnets 27, in particular ferrite or rare earth.

Advantageously, a number of teeth Ns of the stator 11 is equal to 6 times k, k being an integer, ie Ns = 6k. In addition, a number of poles of the rotor 12 Nr is different from 3 times k, that is Ns ^ 3.

The rotor 12 may have a radial flux configuration, that is to say that the permanent magnets 27 may be oriented orthoradially so as to generate a magnetic flux of radial orientation relative to the X axis of the electric machine 10 .

In the embodiment of Figure 1, the rotor 12 is with surface magnets, that is to say that it comprises permanent magnets 27 arranged in housings 28 open at the outer periphery or fixed on an outer periphery of the body rotor 26.

In the embodiment of FIG. 3, the rotor 12 is with buried magnets, that is to say that it comprises permanent magnets 27 arranged in housings 28 closed along all their faces, including at their external periphery . Such a configuration makes it possible to effectively maintain the permanent magnets 27 inside the housings 28, even at high speeds.

In the embodiment of Figure 4, the rotor 12 has two radial layers of permanent magnets 27. The magnets 27 of a given layer are arranged along the same diameter.

In the embodiment of Figure 5, the rotor 12 has poles formed by permanent magnets 27 which define a V shape. These magnets 27 are arranged inside corresponding housings 28 closed, along all their faces. By V-shape is meant the fact that in cross section, the longitudinal axes X1 of at least one set of two magnets 15 of a pole form a non-zero angle between them. The housings 28 associated with a pole are in this case distinct from each other. Alternatively, the housings 28 could meet at the point of the V.

The permanent magnets 27 can be made of ferrite or rare earth depending on the applications and the desired power of the machine. Alternatively, the permanent magnets 27 may be of a different shade to reduce costs.

An exemplary non-limiting embodiment of the electric machine 10 according to the invention is provided below, presenting the parameters listed in the table below. This electric machine 10 has been optimized so as to maximize the torque for fixed AC copper losses.

Setting notation Unit Value External radius of rso mm 45 stator Length of body Lsk mm 25 rotor Length of g mm 0.5 the air gap Split Ratio Sr - 0.65 Thickness of the H _b mm 4

stator yoke

Stator tooth width mm 6.5 Height of one Hpm permanent magnet mm 5 Remanence B _r a permanent magnet T 0415 Coercivity of a permanent magnet H _c kA / m 255 Number of turns Ne per coil - 106 Wire diameter D _w mm 0.63 Factor of k _p - 0.4

filling

The magnetic flux distribution for different DC excitations is shown in Figures 6a to 6c respectively for zero DC excitation (see Figure 6a with an excitation current density Jc = 0), a positive DC excitation. (cf. FIG. 6b), and a negative DC excitation (cf. FIG. 6c).

In the event of positive direct current excitation, in this case for an excitation current density equal to Jdc = 5A / mm2, the magnetic flux passing through phase A is increased.

In the event of negative direct current excitation, in this case for a density of the excitation current equal to Jdc = -5A / mm2, the flux passing through phase A is reduced.

Thus, it is observed that the magnetic flux can be regulated by direct current excitations of different values.

FIG. 7a shows, for a rotation speed of 400 rpm, graphical representations of the counter-electromotive force B_EMF as a function of the position of the rotor Pos_rot expressed in electrical angle for different excitations in direct current.

Curve C_1 was obtained for zero direct current excitation. The curve C_2 obtained for a positive DC excitation exhibits an increased electromotive force. The curve C_3 obtained for a negative DC excitation has a reduced counterelectromotive force.

Figure 7b shows the spectra corresponding to the different curves C_1, C_2, C_3 as a function of the order of the harmonic. It is thus observed that the counter-electromotive force can be regulated by direct current excitations of different values.

Figure 8 shows the evolution of the amplitude of the fundamental frequency of the counter-electromotive force Fond_EMF according to the density of the continuous excitation current Dens_lexc_DC. It is observed that the increase in flux is greater than the reduction in flux for the same value of current density Dens_lexc_DC. In addition, when the excitation current Dens_lexc_DC is too large, the magnetic field is saturated, so that the amplitude of the fundamental frequency Fond_EMF tends to decrease.

FIG. 9a shows, for AC copper losses equal to Pac = 20W, graphic representations of the electromagnetic torque C_em as a function of the position of the rotor Pos_rot expressed in electrical angle for different excitations in direct current.

The C_T curve was obtained for zero DC current excitation. The curve C_2 'obtained for a positive DC excitation has a level of electromagnetic torque C_em aumenté. The curve C_3 'obtained for a negative DC excitation has a reduced level of electromagnetic torque C_em. It is thus observed that the electromagnetic couple C_em can be regulated by direct current excitations of different values.

Figure 9b shows the spectra corresponding to the different curves as a function of the order of the harmonic. There is a significant third order torque component which is caused by the second order harmonic of the counter-electromotive force B_EMF as shown in Figure 7b.

FIG. 10 represents the evolution of the average torque C_moy as a function of the copper losses Little respectively without direct current (cf. curve C_1), with a positive direct current excitation increasing the magnetic flux (cf. curve C_2), and with an excitation in negative direct current reducing the magnetic flux (see curve C_3).

Figure 11 shows a graphic representation of the average torque as a function of the total copper losses (Pdc + Pac) and of a ratio of the copper losses in direct current Pdc divided by the total losses AC and DC either (Pdc / (Pdc + Pac) ).

FIG. 12 is a graphic representation of the mean torque C_moy as a function of the total copper losses respectively without continuous excitation (cf. curve C_4) and with optimal continuous excitation (cf. curve C_5).

The torque improvement ratio for the hybrid excitation is defined as follows: (Topt -Tnon) / Tnon,

- Topt being the torque obtained with optimal continuous excitation and

- Tnon being the torque obtained without continuous excitation.

We observe that with the increase in copper losses, the torque improvement ratio increases.

Copper losses Torque improvement ratio [(T opt T no) / T no] 1 * pcu 10.2% 2 * Little 18.2% 3 * Little 21.3% 4 * Little 24.0% 5 * Little 25.2%

Furthermore, in order to limit the variations in torque, an air gap 13 extending between an external periphery of the rotor 12 and an internal periphery of the stator 11 may be variable, in particular according to its radial thickness relative to the axis X of the machine.

In the embodiment of FIG. 13a, an external periphery of the permanent magnets 27 has a domed shape, in particular in a radial direction.

In the embodiment of FIG. 13b, an external periphery of 5 portions of the rotor 30 extending between the permanent magnets 27 has a domed shape, in particular in a radial direction.

Of course, the foregoing description has been given by way of example only and does not limit the scope of the invention from which one would not depart by replacing the various elements with any other equivalent.

ίο In addition, the different features, variants, and / or embodiments of the present invention can be associated with each other in various combinations, insofar as they are not incompatible or mutually exclusive of each other.

Claims (13)

1. Rotating electric machine (10) in particular for a motor vehicle, comprising: - a rotor (12) with permanent magnets (27), - a stator (11) provided with a winding (16) comprising a plurality of phases (A, B, C) each formed by windings (A1-A2, B1-B2, C1-C2), characterized in that said rotary electrical machine (10) further comprises: - a first power inverter (24.1) comprising a plurality of bridge arms (BP1-BP3), - a second power inverter (24.2) comprising a plurality of bridge arms (BP1 '-BP3'), - And in that at least one group of two windings (A1-A2, B1B2, C1-C2) of a phase has one end connected to a bridge arm (BP1-BP3) of the first power inverter (24.1) and one end connected to a bridge arm (ΒΡΓ-ΒΡ3 ') of the second power inverter (24.2). 2. Rotating electric machine (10) according to claim 1, characterized in that a number of teeth (Ns) of the stator (11) is equal to 6 times k, k being an integer. 3. Rotating electric machine (10) according to claim 1 or 2, characterized in that a number of poles of the rotor (Nr) is different from 3 times k, k being an integer. 4. Rotating electric machine (10) according to any one of claims 1 to 3, characterized in that the rotor (12) is in radial flux. 5. Rotating electric machine (10) according to any one of claims 1 to 4, characterized in that the rotor (12) is with surface magnets. 6. Rotating electric machine (10) according to any one of claims 1 to 4, characterized in that the rotor (12) is buried magnets. 7. Rotating electric machine (10) according to any one of claims 1 to 6, characterized in that the rotor (12) comprises two radial layers of permanent magnets (27). 8. Rotating electric machine (10) according to any one of claims 1 to 3, characterized in that a pole of the rotor (12) is formed by at least two permanent magnets (27) forming a non-zero angle between them. 9. rotary electric machine (10) according to any one of claims 1 to 8, characterized in that an air gap (13) extending between an external periphery of the rotor (12) and an internal periphery of the stator (11) is variable. 10. Rotating electric machine (10) according to claim 9, characterized in that an external periphery of the permanent magnets (27) has a curved shape. 11. Rotating electric machine (10) according to claim 9 or 10, characterized in that an external periphery of portions of the rotor (30) extending between the permanent magnets (27) has a domed shape. 12. Rotating electric machine (10) according to any one of claims 1 to 11, characterized in that the winding (16) is of the concentrated type. 13. rotary electric machine (10) according to any one of claims 1 to 12, characterized in that the winding (16) is formed from coils (23) of continuous wire wound around teeth (18) of the stator ( 11).