FR3084789A1 - ROTATING ELECTRIC MACHINE WITH ADAPTED ELECTRIC RESISTANCE - Google Patents

Abstract

The invention relates mainly to an assembly for a motor vehicle comprising: - a battery (24) comprising an internal resistance (r), and - at least one rotary electrical machine (19) associated with a power inverter (21), the machine rotary electrical unit (19) and the associated power inverter (21) having an equivalent electrical resistance (R), characterized in that a ratio between the internal resistance (r) of the battery (24) and the equivalent electrical resistance ( R) of the rotary electrical machine (19) and of the associated power inverter (21) is between 0.8 and 1.2.

Description

ROTATING ELECTRIC MACHINE WITH ADAPTED ELECTRIC RESISTANCE

The present invention relates to a rotary electrical machine with suitable electrical resistance.

In a manner known per se, an electric or hybrid type motor vehicle comprises a rotary electric machine integrated in the traction chain, in particular in the gearbox or in the clutch, or installed on one of the trains of the motor vehicle. The electric machine is generally a reversible machine capable of operating in a generator mode to recharge a vehicle battery as well as in an engine mode to ensure traction of the vehicle.

Hybrid or recharging vehicles on an external network (architecture called plug-in in English) make it possible to significantly reduce the emission of polluting particles in approval cycles or outside cycles, that is to say in real driving life of the motor vehicle.

A significant part of these gains is obtained in energy recovery mode during a braking or deceleration phase of the vehicle. The energy recovery phase most often occurs in areas of low speed and full load operation of the electric machine, for short periods of the order of 5 to 20 seconds.

The invention aims to optimize the configuration of the electric machine at these operating points in energy recovery mode by adapting the resistance of the electric machine and of the associated inverter according to the internal resistance of the battery. The invention is particularly well suited to electric machines having an operating voltage of 48V, since the electrical resistances of the windings of this type of electric machine are particularly low.

More specifically, the subject of the invention is an assembly for a motor vehicle comprising:

- a battery comprising an internal resistance, and

- at least one rotating electrical machine associated with a power inverter, the rotating electrical machine and the associated power inverter having an equivalent electrical resistance, characterized in that a ratio between the internal resistance of the battery and the equivalent electrical resistance of the rotating electric machine and the associated power inverter is between 0.8 and 1.2.

According to one embodiment, the ratio between the internal resistance of the battery and the equivalent electrical resistance of the rotary electrical machine and the power inverter is equal to 1.

According to one embodiment, said assembly comprises a second rotating electrical machine associated with a second power inverter, a ratio between the internal resistance of the battery and the equivalent electrical resistance of the two rotating electrical machines and their corresponding power inverters being between 0.8 and 1.2 and is preferably 1.

According to one embodiment, the two rotary electrical machines are electrically connected in series.

According to one embodiment, the two rotating electrical machines are electrically connected in parallel.

According to one embodiment, an electromotive force of the battery is equal to half of a voltage of the battery.

According to one embodiment, an operating voltage of the rotary electric machine is 48 Volts.

According to one embodiment, the rotary electric machine has a power of between 10 kW and 30 kW.

According to one embodiment, the internal resistance of the battery is between 20 mOhms and 40 mOhms.

The invention also relates to a motor vehicle characterized in that it comprises an assembly as previously defined.

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 schematic representation of a motor vehicle according to the invention comprising a rotating electrical machine / battery assembly according to the invention;

Figure 2 is an electrical diagram of connection between the battery and the rotating electrical machine;

FIG. 3 is a schematic representation of the electric power as a function of the battery current;

FIGS. 4a and 4b are electrical diagrams of alternative connections for embodiments of the invention to two electrical machines.

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

FIG. 1 shows a motor vehicle 10 comprising a traction chain 11 installed on a front axle. This traction chain 11 comprises a heat engine 13 coupled to a gearbox 14 by means of a clutch 16. The gearbox 14 is mechanically connected to a differential 17.

A rotary electrical machine 19 may be coupled to the heat engine via a movement transmission device 20, in particular with a belt, or integrated in the gearbox 14, or even integrated in the clutch 16.

The electric machine 19 is capable of operating in a generator mode for recharging a vehicle battery as well as in an engine mode for ensuring starting of the thermal engine 13 while the vehicle is stopped or during a transition from a electric driving mode towards a thermal driving mode. This electric machine 19 can also be used to supply energy to the battery during a regenerative braking phase.

The electrical machine 19 is connected, via its associated power inverter 21, to a first electrical network 23 to which a battery 24 is also connected. This electrical network 23 has an operating voltage of less than 60 volts. Advantageously, the operating voltage of the electrical network is 48 Volts. Other electrical charges 25 may also be connected to the electrical network 23.

The electric machine 19 may have a power between 10 kW and 30 kW and provide a torque between 55Nm and 100Nm depending on its length. The electric machine 19 could for example be of the synchronous type with permanent magnets or with excitation. The cooling circuit of the electric machine 19 may be based on water or oil. As a variant, it is also possible to use an electric machine 19 of the asynchronous type. Alternatively, the electric machine 19 operates under high voltage, that is to say at a voltage of the order of 300 Volts.

The electrical network 23 is interfaced with a second low voltage electrical network 27 by means of a DC / DC converter 28. The engine computer as well as the electrical consumers 29 of the vehicle of the lighting type, window or seat actuators are connected to the electrical network 27. This electrical network 27 called on-board network is associated with a battery 30 having an operating voltage lower than that of the first electrical network 23. The operating voltage of the electrical network 27 is preferably of the order of 12 volts.

As can be seen in FIG. 2, the electric battery 24 has an internal resistance denoted r, while the electric machine 19 and the associated inverter have an equivalent electric resistance R. The internal resistance r of the battery 24 is for example between 20 mOhms and 40 mOhms.

A ratio between the internal resistance r of the battery 24 and the equivalent electrical resistance R of the electric machine 19 and the associated inverter 21 is between 0.8 and 1.2. Advantageously, in order to maximize the electrical power stored by the battery 24 during a regenerative braking phase, the ratio between the internal resistance r of the battery 24 and the equivalent electrical resistance R of the electric machine 19 and of the inverter 21 is worth 1.

Indeed, as can be seen in Figure 3, the power P of the battery 24 tends to increase to a maximum and then decrease to zero. In other words, in the case where the current I is low, very little power P is recovered during the braking phase. In the case where the current I is high, the power P decreases due to the increase in the voltage drop across the internal resistance r. An intermediate current Imax optimizes the power of the battery 24.

Furthermore, the voltage Ubatt across the terminals of the battery 24 verifies the following relationship: Ubatt = Rl = E-r * l

E being the empty electromotive force (fem) of the battery 24,

- r being the resistance of the battery 24,

R being the equivalent electrical resistance of the electrical machine 19, in particular the winding and of the associated inverter 21, and

-1 being the direct current of the battery 24.

The electric power P is worth P = Ubatt * l = (Er * l) * l = E * i -r * l ² , Ubatt being the DC voltage across the battery 24.

This electrical power P reaches a maximum corresponding to an optimal current Imax when its derivative with respect to the current is zero (cf. FIG. 3), that is to say dP / dl = 0, 0 = E-2 * rlmax

Imax = E / 2 * r

E- r * lmax = R * lmax

E-r * E / 2 * r = R * E / 2 * r

E (1 -1/2) = R * E / 2 * r

The maximum electrical power value P is therefore obtained for R = r, i.e. a ratio R / r = 1.

Furthermore Ubatt = E- r * lmax = E-r * E / 2 * r = E-1/2 E = E / 2. There is therefore optimum operation when the electromotive force E of the battery 24 is equal to half the voltage Ubatt of the battery 24, ie E = Ubatt / 2.

It should be noted that this calculation is valid at low speed, that is to say at a speed of rotation of the electric machine 19 less than 1000 revolutions / min. Indeed, in this case, the inductive component (Lw) of the winding is low because the pulsation w is low. This is valid whatever the configuration of the winding of the electric machine 19 (triangle, star, or mixed).

We can use a second rotating electric machine 19 'associated with a second power inverter 21'. The second electric machine 19 ′ may for example be installed on the rear axle of the vehicle.

A ratio between the internal resistance r of the battery 24 and the equivalent electrical resistance of the two electric machines 19, 19 'and their corresponding inverters 21, 21' is between 0.8 and 1.2 and is preferably 1.

As shown in Figure 4a, the two electrical machines 19, 19 'can be electrically connected in series. In this case, the equivalent resistance Requ of the two electric machines 19, 19 'and the inverters 21, 21' is equal to the sum of equivalent resistance R of the first electric machine 19 and its inverter 21 thus and the equivalent resistance R 'of the second electric machine 19' and its 2Γ inverter, ie Requ = R + R '.

Alternatively, as shown in FIG. 4b, the two electric machines 19, 19 ′ can be electrically connected in parallel. In this case, the equivalent resistance Requ of the two electric machines 19, 19 'and their inverters 21, 21' is equal to Requ = R * R7 (R + R ').

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.

Furthermore, the various features, variants, and / or embodiments of the present invention can be combined with one another in various combinations, insofar as they are not incompatible or mutually exclusive of one another.

Claims (10)

1. Motor vehicle assembly comprising: - a battery (24) comprising an internal resistance (r), and - at least one rotating electrical machine (19) associated with a power inverter (21), the rotating electrical machine (19) and the associated power inverter (21) having an equivalent electrical resistance (R), characterized in that a ratio between the internal resistance (r) of the battery (24) and the equivalent electrical resistance (R) of the rotary electrical machine (19) and of the associated power inverter (21) is between 0.8 and 1.2. 2. Assembly according to claim 1, characterized in that the ratio between the internal resistance (r) of the battery (24) and the equivalent electrical resistance (R) of the rotary electric machine (19) and of the power inverter (21) is 1. 3. Assembly according to claim 1 or 2, characterized in that it comprises a second rotary electric machine (19 ') associated with a second power inverter (21') and in that a ratio between the internal resistance (r ) of the battery (24) and the equivalent electrical resistance (Requ) of the two rotating electrical machines (19, 19 ') and their corresponding power inverters (21, 21') is between 0.8 and 1.2 and is preferably 1 . 4. An assembly according to claim 3, characterized in that the two rotary electrical machines (19, 19 ') are electrically connected in series. 5. An assembly according to claim 3, characterized in that the two rotary electrical machines (19, 19 ') are electrically connected in parallel. 6. An assembly according to any one of claims 1 to 5, characterized in that an electromotive force (E) of the battery (24) is equal to half of a voltage (Ubatt) of the battery (24). 7. Assembly according to any one of claims 1 to 6, characterized in that an operating voltage of the rotary electric machine (19) is 48 Volts. 8. An assembly according to any one of claims 1 to 2, 5 characterized in that the rotary electric machine (19) has a power between 10kW and 30kW. 9. An assembly according to any one of claims 1 to 2, characterized in that the internal resistance (r) of the battery (24) is between 20 mOhms and 40 mOhms. ίο 10. Motor vehicle characterized in that it comprises an assembly as defined according to any one of the preceding claims.