FR3059172A1 - COOLING SYSTEM OF AN ELECTRIC MACHINE. - Google Patents

Abstract

The invention relates to an electric machine (1) comprising a stator (13) installed in a housing (11), the stator (13) having a plurality of stator windings (18) forming at each longitudinal end of the stator (13) a plurality coil heads (14), said stator windings (18) being electrically connected to power electronics members by electrical connection means (16); said machine further comprising means for projecting (21) a cooling fluid installed facing at least one of the longitudinal ends of the stator (13), said projection means (21) are oriented so as to project simultaneously said cooling fluid on the coil heads (14) of said at least one longitudinal end of the stator (13) and on the electrical connection means (16).

Description

® FRENCH REPUBLIC

NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY © Publication number:

(to be used only for reproduction orders)

©) National registration number

059 172

61299

COURBEVOIE © IntCI ⁸ : H 02 K 9/19 (2017.01)

PATENT INVENTION APPLICATION

A1

©) Date of filing: 21.11.16. (© Applicant (s): RENAULT S.A.S Joint-stock company ©) Priority: simplified - FR and NISSAN MOTOR CO., LTD - JP. @ Inventor (s): TAVERNIER GUILLAUME, MIKATI KARIM and PARIS FRANÇOIS. (43) Date of public availability of the request: 25.05.18 Bulletin 18/21. ©) List of documents cited in the report preliminary research: Refer to end of present booklet (© References to other national documents ©) Holder (s): RENAULT S.A.S Société par actions sim- related: NISSAN MOTOR CO., LTD. ©) Extension request (s): © Agent (s): RENAULT SAS.

Q4) COOLING SYSTEM OF AN ELECTRIC MACHINE.

FR 3 059 172 - A1 _ The invention relates to an electric machine (1) comprising a stator (13) installed in a casing (11), the stator (13) having a plurality of stator windings (18) forming at each longitudinal end from the stator (13) a plurality of coil heads (14), said stator windings (18) being electrically connected to power electronics members by electrical connection means (16); said machine further comprising projection means (21) of a cooling fluid installed opposite at least one of the longitudinal end of the stator (13), said projection means (21) are oriented so as to simultaneously project said coolant on the coil heads (14) of said at least one longitudinal end of the stator (13) and on the electrical connection means (16).

Cooling system of an electric machine

The present invention relates to a cooling system of an electric machine.

Electric machines are made up of a stator and a rotor. The stator is wound so that under the effect of an electric current, it produces a magnetic field causing the rotor to rotate.

A well-known problem relates to the heating of the stator windings.

îo Indeed, under the effect of the current flow, the stator windings heat up by Joule effect, which can damage their electrical insulation with the stator. Also it is generally necessary to cool the stator windings.

Particularly known from document CN202034859 is a device for cooling an engine comprising a circuit for circulating coolant supplying nozzles housed in a casing and opening into the engine. The nozzles spray coolant onto the stator coil heads so that the coolant spills inside the engine. The liquid is then collected in a tank under the engine, then is led outside the casing by a pipe. It is then cooled in a heat exchanger and is reinjected into the top of the engine by a pump.

In fact, knowing that a large proportion of the heating of the stator windings is concentrated in the vicinity of the coil heads also called "chignon", it is known to cool these coil heads in particular.

However, the heating produced by the stator windings also propagates in the casing of the electric machine, which can damage the other components of the machine.

In particular, the electric machine is powered by power electronics components 30 which supply electric current to the stator coils. More specifically, the stator coils are connected to these power electronics components by bus bars making the link between the electrical machine and the power electronics components.

However, the temperature above which the components of the power electronics deteriorate is generally lower than that above which the components of the stator and of the rotor deteriorate.

In addition, the reduction in the size of the electrical machines, which is accompanied by a reduction in the heat exchange surface, complicates the cooling of the electrical machines whose increasing mechanical power increases the current density in the motor and hence the heat radiated by the engine.

Consequently, there is an increase in the amount of heat îo transmitted by the electric machine to the power electronics components, especially via the bus bar connection.

There is therefore a need to improve the cooling system of electric machines, having a smaller size and a higher mechanical power, in particular in order to reduce the risk of damage to the power electronic components.

An electric machine is proposed comprising a stator installed in a casing, the stator having a plurality of stator windings forming at each longitudinal end of the stator a plurality of coil heads, said stator windings being electrically connected to electronic power members by electrical connection means; said machine further comprising means for projecting a cooling fluid installed facing at least one of the longitudinal ends of the stator so as to project said cooling fluid onto the coil heads of said at least one longitudinal end of the stator.

Said projection means are further oriented to simultaneously project said cooling fluid onto said electrical connection means.

Thus it is possible to simultaneously cool the stator coil heads and the electrical connection means, which makes it possible to limit the heat transmitted to the power electronics components in particular to the current sensors and to protect them from a potential deterioration caused by excessive heating of the stator windings.

Advantageously and in a nonlimiting manner, the electrical connection means comprise for each stator winding a bus bar connecting a free end of said stator winding to said power electronics.

Thus, the use of a bus bar ensures a good electrical connection 5 between the stator windings and the components of the power electronics. They also allow easy assembly and disassembly.

Advantageously and in a nonlimiting manner, the means for projecting the cooling fluid are fixed to a wall of the casing.

Thus, a compact cooling system is obtained since it does not require the addition of an external device to the casing.

Advantageously and in a nonlimiting manner, the wall of the casing where the projection means are fixed is located in the vicinity of the electrical connection means.

Thus, this arrangement makes it possible to better target the areas to be cooled and not to spray the coolant on areas which do not need to be cooled.

Advantageously and without limitation, the cooling means comprise a spray nozzle.

Thus, the use of a spray nozzle is a compact and rapid means 20 of spraying a large amount of fluid into the housing.

Advantageously and without limitation, the spray nozzle is adapted to vaporize the cooling fluid.

Thus, spray spraying provides a very large projection area. Consequently, the heat exchange surface with the fluid also increases. This makes the cooling of the electrical connections and the stator coil heads more efficient.

Advantageously and in a nonlimiting manner, the cooling fluid is a dielectric liquid.

Thus, the fluid being insulating, it protects from short circuits.

Advantageously and in a nonlimiting manner, the dielectric liquid can be oil.

Oil is therefore an expensive and easy to use dielectric liquid.

Advantageously and in a nonlimiting manner, the electric machine is supplied by a three-phase current.

Thus this supply by a three-phase current makes it possible to rotate the rotor in the stator continuously, thus creating mechanical energy.

Other particularities and advantages of the invention will emerge on reading the description given below of particular embodiments of the invention, given by way of non-limiting indication, with reference to the appended drawings in which:

- Figure 1 is a perspective view of an engine according to an embodiment of the invention;

- Figure 2 is a longitudinal section of an electric machine according to an embodiment of the invention.

By substantially horizontal, longitudinal or vertical is meant a direction / plane forming an angle of at most ± 20 °, or even at most 10 ° or at most 5 ° with a direction / horizontal, longitudinal or vertical.

By substantially parallel, perpendicular or at right angles is meant a direction / angle deviating by at most ± 20 °, or even at most 10 ° or at most 5 ° from a parallel, perpendicular or at a right angle.

Figures 1 and 2 relate to the same embodiment of the invention, they will be commented on simultaneously.

An electric machine 1 comprises a rotor 12 and a stator 13 installed in a casing 11.

The casing 11 comprises an upper wall 11a and a lower wall

11b.

Under the lower wall 11b is installed a coolant recovery tank 23.

The casing 11 further comprises two side walls 11c and 11d facing each other. These two side walls 11c and 11d define two opposite faces each of a longitudinal end of the stator 13.

The stator 13 has a substantially cylindrical shape whose axis of revolution is designated by its longitudinal axis.

The rotor shaft 12 is placed along the longitudinal axis of the stator 13.

The rotor shaft 12 crosses the two opposite walls 11c and 11d of the casing 11 substantially in their middle and extends outside the casing 11.

The stator 13 has a circumferential plurality of stator windings 18 which extend along the longitudinal axis of the stator 13.

The stator windings 18 are obtained by winding wires of extended phases of cables 17 then bus bars 16 via lugs. In particular, in the case of a three-phase supply of the stator, the stator windings 18 wound so as to define the stator poles, are terminated by three phase cables 17.

Each stator winding 18 forms a coil head 14 at each of the longitudinal ends of the stator 13.

The coil heads 14 project at each longitudinal end of the stator 13.

The set of coil heads 14 grouped at each of the longitudinal ends of the stator 13 forms a stator bun.

In Figure 1, only a stator bun is shown.

The stator windings 18 are electrically connected to a power electronics unit (not shown in FIGS. 1 and 2) via a connector 15 formed from three plastic housings housing three bus bars connected to the bus bars 16 coming out of the machine casing electric via screws. It is the heating of the bus bars via the joule losses of the stator but also via their own heating which brings heat to the power electronics.

Connection means 16, here bus bars 16, provide the electrical connection between the connector 15 and the stator windings 18. In particular, a bus bar 16 allows the electrical connection between a phase cable 17 and the connector 15.

The electric machine 1 being in this embodiment a three-phase machine, the connection means 16 comprise at least one bus bar

16 per phase, i.e. 3 busbars.

Each bus bar 16 is on the one hand connected to a free end of a phase cable 17 and on the other hand screwed to the connector 15.

The phase cable 17 connected to a bus bar 16 is connected to phase wires wound around the stator in order to form a stator winding 18.

Each bus bar is therefore associated with a particular phase of the three-phase electrical supply supplied by a power inverter, not shown.

The stator 13 is supplied with three identical currents and phase shifted by 2tt / 3 which generates a rotating electromagnetic field capable of driving the rotor 12 in rotation.

However, an electrical machine could be provided with N pairs of electromagnetic poles, where N is an integer greater than or equal to 1.

When the electric machine 1 is in operation, the stator windings 18 heat up under the effect of the passage of electric current. In particular, 30% to 40% of the energy losses of the coils due to the Joule effect are concentrated at the level of the coil heads 14.

This heat then propagates to the power electronics.

In order to avoid the transmission of the heat produced by the Joule effect from the stator 13 to the power electronics, the coil heads 14 where the heat is concentrated are cooled as well as the bus bars 16 which provide the electrical connection with power electronics.

The bus bars 16 are fixed to an edge of the side wall 11d of the casing, for example screwed to the side wall 11d. Thus, the bus bars 16 are installed at a longitudinal end of the casing and consequently opposite a longitudinal end of the stator 13.

For example, when a phase cable 17 is screwed onto the corresponding bus bar 16, the fixing screw is inserted into the edge of the side wall 11d.

The cooling of the electric machine 1 is ensured by a cooling device comprising a circuit for circulating the coolant 20, a tank for recovering the coolant 23, a pump, not shown, and means 21 for projecting the coolant. cooling.

The cooling fluid circulation circuit 20 extends at least partially in the upper wall 11 a and the side wall 11 c of the casing 11.

In this embodiment, the coolant is oil.

However, the coolant can also be any suitable fluid 5 for cooling the windings of an electric machine, in particular any dielectric coolant.

The circulation circuit 20 supplies the projection means 21 with the cooling fluid.

Here, the means 21 for projecting the coolant comprise a nozzle 21 for projecting the coolant.

The nozzle 21 is installed in the upper wall of the casing 11a so that it is supplied by the circulation circuit 20 and that it projects the coolant inside the casing 11.

The nozzle 21 vaporizes the cooling fluid in the form of fine droplets distributed in a spray cone 22.

The nozzle 21 is installed in the upper wall of the casing 11a, in the vicinity of the bus bars 16. Thus, the nozzle 21 is installed in the upper wall of the casing 11a, in the vicinity of a longitudinal end of the stator 13.

A hole drilled in the upper wall of the casing 11a makes it possible to install the connector housing 15 there and to connect the power electronics members to the distributor 15.

The nozzle 21 is oriented so that the spray cone 22 is aimed at at least one coil head 14 of the stator windings 18 at the longitudinal end in the vicinity of which the nozzle 21 is installed, and also the bus bars 16 installed in the vicinity of this same longitudinal end.

In other words, the nozzle 21 is oriented at an angle, between a descending vertical axis and a horizontal axis, so as to spray the coolant on the stator coil heads 18 and on the bus bars 16 simultaneously.

Spraying the coolant, in this case oil, allows a larger contact surface between the fluid and the electrical components, and therefore a larger heat exchange area, thus improving the cooling of the electrical connections.

The cooling fluid then flows on the stator bun, and on the side wall on which the bus bars 16 are installed, towards the bottom of the casing 11 and is recovered in the tank 23. Thus, the oil can be recovered then reinjected into the coolant circulation circuit.

In an alternative embodiment and not shown, it is possible to install several nozzles 21, for example two to four, in the upper wall of the casing 11a, so that each of these nozzles 21 sprays the coolant liquid on both the coil heads 14 and on the bus bars 16.

All the nozzles 21 are thus oriented at an angle towards the coil heads and the bus bars 16. By increasing the number of nozzles 21, the quantity of cooling fluid which can be vaporized is increased and the cooling of the electric machine is thus improved.

In an alternative embodiment, air can be used as the coolant.

Claims (9)

1. Electric machine (1) comprising a stator (13) installed in a casing (11), the stator (13) having a plurality of stator windings (18) forming at each longitudinal end of the stator (13) a plurality of heads coils (14), said stator windings (18) being electrically connected to power electronic components by electrical connection means (16); said machine further comprising projection means (21) of a cooling fluid installed opposite at least one of the longitudinal ends of the stator (13) so as to spray said cooling fluid onto the coil heads (14 ) of said at least one longitudinal end of the stator (13), characterized in that said projection means (21) are further oriented to simultaneously project said cooling fluid onto said electrical connection means (16). 2. Electric machine (1) according to claim 1, characterized in that the electrical connection means (16) comprise for each stator winding (18) a bus bar (16) connecting a free end of said stator winding (18) to said members power electronics. 3. Electric machine (1) according to claim 1 or 2, characterized in that the projection means (21) of the cooling fluid are fixed on an upper wall of the casing (11). 4. Electric machine (1) according to claim 3, characterized in that said electrical connection means are installed in the vicinity of said projection means (21) of the cooling fluid. 5. Electric machine (1) according to any one of claims 1 to 4, characterized in that said cooling means comprise a spray nozzle (21). 6. Electric machine (1) according to claim 5, characterized in that said spray nozzle (21) is adapted to vaporize the cooling fluid. 7. Electric machine (1) according to any one of claims 1 to 6, 5 characterized in that the cooling fluid is a dielectric liquid. 8. Electric machine (1) according to claim 7, characterized in that said dielectric liquid is oil. îo 9. Electric machine (1) according to any one of claims 1 to 8, characterized in that it is supplied by a three-phase current; said stator windings (18), wound so as to define the stator poles, being terminated by three phase cables (17). 1/1