STATOR IMPREGNATION METHOD

Abstract

Method for impregnating a stator of a rotary electric machine comprising slots, electrical conductors accommodated in the slots, at least two electrical conductors being electrically connected by an electrical connection, the method comprising the following steps: a) heating the stator to a first temperature; b) applying a resin close to the slots of the stator; c) heating the stator to a second temperature; d) applying the resin to the one or more electrical connections of the electrical conductors, application steps b) and d) being achieved through flow of the resin.

Claims

1. A method for impregnating a stator of a rotary electric machine comprising slots, electrical conductors accommodated in the slots, and at least two electrical conductors being electrically connected by an electrical connection, the method comprising the following steps: a) heating the stator to a first temperature, b) applying a resin close to the slots of the stator, c) heating the stator to a second temperature, d) applying the resin to the electrical connections of the electrical conductors, application steps b) and d) being achieved through flow of the resin, the longitudinal axis of the stator being substantially horizontal or slightly inclined with respect to the horizontal.

2. A method for impregnating a stator of a rotary electric machine comprising slots, electrical conductors accommodated in the slots, at least two electrical conductors being electrically connected by an electrical connection, the method comprising the following steps: a) heating the stator to a first temperature, b) applying a resin close to the slots of the stator, c) heating the stator to a second temperature higher than the first temperature, d) applying the resin to the electrical connection of the electrical conductors, application steps b) and d) being carried out by flowing of the resin, step c) of heating to a second temperature beginning before step d) of application to the electrical connections.

3. The method according to one of the two claim 1, comprising the following step: c′) heating the stator to a third temperature.

4. The method according to claim 1, the stator being heated by thermal conduction during steps a) and/or c) of heating.

5. The method according to claim 1, step b) of application close to the slots and step d) of application on the electrical connections being carried out by means of at least one nozzle, different nozzles being used to carry out step b) of application in the slots and step d) of application on the electrical connections.

6. The method according to claim 5, further comprising a step of translation of the nozzle(s) which is carried out between step b) of application close to the slots and step d) of application on the electrical connections.

7. The method according to claim 5, step b) of application close to the slots being carried out by means of two nozzles, a first nozzle being located at a first axial end of the stator inside the electrical conductors and a second nozzle being located at the other axial end of the stator outside the electrical conductors, step b) of application close to the slots comprising the following steps: b1) applying the resin close to the slots, b2) moving the nozzles so that the first nozzle is located outside the electrical conductors and the second nozzle is located inside the electrical conductors, b3) applying the resin close to the slots.

8. The method according to claim 1, the stator being driven in rotation.

9. The method according to claim 1, comprising the following step: e) polymerizing the resin deposited on the stator.

10. The method according to claim 1, the first temperature being between 80 and 160° C.

11. The method according to claim 1, the second temperature being between 110 and 190° C.

12. The method according to claim 1, a layer of resin with a thickness of between 0.05 mm and 2 mm being applied to the electrical connections.

13. The method according to claim 1, at least some of the electrical conductors, if not a majority of the electrical conductors, being in pin form, in particular in the form of U-pins or I-pins.

14. The method according to claim 1, the viscosity of the resin at the second temperature being higher than the viscosity of the resin at the first temperature.

15. The method according to claim 1, the resin comprising at least one polyester.

16. An electrical machine stator impregnated by a method according claim 1.

17. A stator for a rotary electric machine comprising a stator mass comprising slots, electrical conductors accommodated in the slots, at least two electrical conductors being electrically connected defining electrical connections, and comprising a resin comprising at least one polyester filling the slots and covering the electrical connections.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0153] FIG. 1 is a schematic and partial perspective view of a stator produced in accordance with the disclosed method,

[0154] FIG. 2 is a schematic and partial perspective view of the stator of FIG. 1,

[0155] FIG. 3 is a detail perspective view of the stator of FIG. 1,

[0156] FIG. 4 is a diagram illustrating the different steps of the method,

[0157] FIG. 5a is a perspective view of the stator during the step of applying the resin in its slots,

[0158] FIG. 5b is a perspective view of the stator during the step of applying the resin to the electrical connection(s) of the electrical conductors,

[0159] FIG. 6 is a sectional view of the stator,

[0160] FIG. 7a is a view similar to FIG. 5a of an alternative embodiment,

[0161] FIG. 7b is a view similar to FIG. 5b of an alternative embodiment,

[0162] FIG. 8a is a view similar to FIG. 7a of an alternative embodiment,

[0163] FIG. 8b is a view similar to FIG. 7b of an alternative embodiment,

[0164] FIG. 9a is a view similar to FIG. 5a of an alternative embodiment,

[0165] FIG. 9b is a view similar to FIG. 5a of an alternative embodiment,

[0166] FIG. 9c is a view similar to FIG. 5b of an alternative embodiment.

DETAILED DESCRIPTION

[0167] FIGS. 1 to 3 show a stator 2 of a rotary electric machine 1 also comprising a rotor, not shown. The stator makes it possible to generate a rotating magnetic field for driving the rotating rotor, in the context of a synchronous motor, and in the case of an alternator, the rotation of the rotor induces an electromotive force in the electrical conductors of the stator.

[0168] The examples illustrated below are schematic and the relative dimensions of the various component elements have not necessarily been observed.

[0169] The stator 2 comprises electrical conductors 22, which are arranged in slots 21 formed between teeth 23 of a stator mass 25. The slots 21 are closed.

[0170] The electrical conductors 22 comprise strands 33. The strands 33 have a generally rectangular cross-section, in particular with rounded corners. In the described example, the strands 33 are superimposed radially in a single row.

[0171] The thickness e of a strand 33 is its dimension in the radial direction of the machine. The width/of a strand 33 is defined as its dimension in the circumferential direction about the axis of rotation of the machine. The width L of the section to be welded corresponds to the sum of the thicknesses e of each strand.

[0172] The electrical conductors 22 are for the most part in the form of pins, namely U or I pins, and extend axially in the slots. A first electrical conductor accommodated in a first slot is electrically connected to a second electrical conductor accommodated in a second slot, at the outlet from said slots.

[0173] The first and second slots are non-consecutive. In the illustrated example, they are separated by 7 other slots. In a variant, the first and second slots are separated by 3, 4, 5, 6, 8, 9, 10 or 11 other slots, for example.

[0174] The electrical connection is formed on the electrical conductors just after they exit the two slots, at one axial end of the stator mass. The two electrical conductors each comprise an oblique portion 22b, which converge toward one another.

[0175] The electrical connection between two conductors is done in a plane perpendicular to the axis of rotation of the machine, causing the free ends 22a of the strands of the two electrical conductors to melt.

[0176] FIG. 4 is a diagram illustrating the various steps of the method implemented to impregnate the stator.

[0177] After the stator has been wound, it is placed on a workstation dedicated to its impregnation during a step 10. After the stator is positioned, it is heated to a first temperature during the heating step 11. During this step, the stator is rotated, for example at a speed of rotation on the order of 15 rpm.

[0178] When the stator has reached a temperature substantially equal to the first temperature, the resin is applied close to the slots during a first application step 12. During this application step, the applied resin flows into the slots 21 by capillary action in order to fill them.

[0179] This first application step 12 is followed by a first polymerization step 13 of the resin applied in step 12. During this first polymerization step 13, the stator continues to be heated to reach a second temperature higher than the first temperature. During this first polymerization step 13, the resin applied in step 12 begins to polymerize and thus begins its transformation toward the solid state. Polymerization of the resin is possible owing to the heat from the stator. The first polymerization step 13 lasts between 0 and 20 min, more preferably between 5 and 15 min, for example on the order of 10 min. At the end of the first polymerization step 13, substantially all of the resin is polymerized, and its flow into the slots 21 of the stator has stopped. At the end of the polymerization step 13, there is no more resin applied close to the slots of the stator.

[0180] After the polymerization step 13, that is to say, when the flow of resin has stopped, the stator continues to be heated during a new heating step 14 up to a third temperature, higher than the second.

[0181] Once the stator has reached a temperature substantially equal to the third temperature, a second application step 15 takes place. During this second application step 15, the resin is applied to the electrical connection(s) of the electrical conductors 22.

[0182] Finally, a second polymerization step 16 of the resin applied to the stator is carried out by heating the stator to a fourth temperature higher than or equal to the third temperature. The second polymerization step 16 is preferably carried out in a suitable oven. The fourth polymerization temperature is for example between 130 and 280° C., more preferably between 135 and 205° C., more preferably between 130 and 200° C., more preferably between 135 and 195° C., more preferably between 140 and 190° C., more preferably between 145 and 185° C., more preferably between 150 and 180° C., more preferably between 155 and 175° C., for example on the order of 170°. The polymerization time can be between 15 and 60 minutes, more preferably between 25 and 45 minutes, for example on the order of 35 minutes. This second polymerization step 16 makes it possible to change the state of the resin applied to the electrical connections. In the case where the resin used is thermosetting, it thus makes it possible to make it irreversibly solid.

[0183] The application steps 12 and 15 will now be detailed with reference to FIGS. 5a and 5b.

[0184] FIG. 5a illustrates the first application step 12, during which the resin is applied close to the slots 21 of the stator. In the example shown, this application step 12 is carried out by flow by means of two nozzles 30, 30′. The two nozzles 30, 30′ are arranged at substantially 180° from each other. The nozzle 30 is arranged inside the electrical conductors, in the lower part of the cross-section located at the end of the stator, when the stator is observed along its longitudinal axis X. The other nozzle 30′ is arranged outside the electrical conductors, in the upper part of the cross-section located at the end of the stator, when the stator is observed along its longitudinal axis X.

[0185] During the first application step 12 shown in FIG. 5a, the two nozzles 30, 30′ allow the deposition of streams 31, 31′ of resin close to the entrance to the slots 21 of the stator. The resin thus deposited will penetrate the slots 21, in particular due to capillary action. The resin will also spread over the coil heads without necessarily reaching the electrical connections.

[0186] The nozzle 30 deposits the stream 31 of resin at the inner circumference of the slots. The nozzle 30′ deposits the stream 31′ of resin at the inner circumference of the slots.

[0187] The second application step 15 is illustrated in FIG. 5b. To go from the first application step 12 to the second application step 15, the nozzles 30, 30′ are translated, for example in a direction parallel to the longitudinal axis X of the stator, in order to separate them from the stator. For example, the nozzles 30, 30′ are translated along the longitudinal axis X of the stator by a distance of between 0.3 and 10 cm, better still between 0.5 and 5 cm, for example by a distance on the order of 2 or 4 cm. The nozzles 30, 30′ thus translated are each suitable for depositing a stream 32, 32′ of resin on the electrical connections of the electrical conductors 22.

[0188] In the example of FIG. 5b, the arrangement of the nozzles 30, 30′ relative to each other during the second application step 15 is identical to that of the first application step 12 illustrated in FIG. 5a.

[0189] During the second application step 15 shown in FIG. 5b, the two nozzles 30, 30′ allow the deposition of streams 32, 32′ of resin on the electrical connections of the electrical conductors 22.

[0190] In this embodiment, the same nozzles 30, 30′ are used to apply the same resin close to the slots of the stator and on the electrical connections. Using the same nozzles makes it possible to reduce the size of the resin application device. Using the same resin makes it possible not need to modify the supply of the nozzles 30, 30′ with resin between the first application step 12 and the second application step 15.

[0191] FIG. 6 shows the stator obtained by the impregnation method detailed with reference to FIGS. 4, 5a and 5b. This stator has a layer of resin 34 on the electrical connections of thickness er. As illustrated in FIG. 6, the thickness er of the resin layer 34 is measured from the free ends 22a of the electrical conductors 22. The thickness er of the resin layer 34 covering the electrical connections of the electrical conductors 22 is between 0.05 mm and 2 mm, more preferably between 0.25 and 1 mm, for example on the order of 0.5 mm. The resin layer 34 covers almost the entire surface of the electrical conductors 22, which is devoid of insulating enamel. The resin layer 34 of the stator is regular over its entire thickness er. The resin layer 34 of thickness er improves the electrical and mechanical rigidity of the assembly.

[0192] As visible in FIG. 6, a layer of resin 35 is deposited close to the slots 21. This layer makes it possible to mechanically retain the electrical conductors 22 in the slots by filling the empty spaces before impregnation.

[0193] FIGS. 7a and 7b illustrate an alternative embodiment of the method. In this embodiment, the first and second application steps 12, 15 are carried out by means of four nozzles 40, 40′,41, 41′. Preferably, the four nozzles 40, 40′,41, 41′ are arranged at the same end of the longitudinal axis X of the stator. The nozzles 40, 40′ are arranged at substantially 180° from each other. Similarly, the nozzles 41, 41′ are arranged at substantially 180° from each other. The nozzles 40 and 41 on the one hand and 40′ and 41′ on the other hand are arranged at substantially 20° from each other. The nozzles are inclined with respect to the longitudinal axis X of the stator by an angle substantially on the order of 45°. The nozzles are arranged in such a way that two nozzles 40, 41 are arranged inside the electrical conductors and the other two nozzles 40′,41′ are arranged outside when the stator is observed along its longitudinal axis X.

[0194] In this embodiment, the resin is not applied by the same nozzles during the first 12 and the second 15 application steps. Two of the nozzles 40, 40′ serve for example to apply the resin close to the slots of the stator, and the other two 41, 41′ serve for example to apply the resin to the electrical connections.

[0195] The two nozzles 40, 40′ allow streams 31, 31′ of resin to be deposited at the entrance to the slots 21 of the stator. The resin thus deposited will penetrate the slots 21, in particular by capillary action. The resin will also spread over the coil heads without necessarily reaching the electrical connections.

[0196] The nozzle 40 can deposit the stream 31 of resin at the inner circumference of the slots. The nozzle 40′ can deposit the stream 31′ at the inner circumference of the slots.

[0197] The second application step 15 of this four-nozzle embodiment is illustrated in FIG. 7b.

[0198] The arrangement of the nozzles 40, 40′,41, 41′ with respect to one another during the second application step 15 is identical to that of the first application step 12 illustrated in FIG. 7a.

[0199] During the second application step 15 shown in FIG. 7b, the two nozzles 41, 41′ allow the deposition of streams 32, 32′ of resin on the electrical connections of the electrical conductors 22.

[0200] This embodiment with four nozzles, each pair of which is dedicated to the application of the resin either close to the slots of the stator or on the electrical connections, has the advantage that it is not necessary to translate the nozzles between the two application steps. This makes it possible to implement the method more quickly.

[0201] The embodiment shown in FIGS. 8a and 8b is a variant of the embodiment with four nozzles, each pair of which is dedicated to the application of the resin to a given area of the electrical conductors of the stator.

[0202] In this variant, the nozzles 50, 50′ used for application close to the slots of the stator and the nozzles 51, 51′ used for application on the electrical connections are different. For example, the nozzles 51, 51′ dedicated to applying the resin to the electrical connections are duckbill nozzles 510. In the illustrated embodiment, the longer side of the rectangular cross-section extends parallel to the longitudinal axis of the stator. Such a nozzle makes it possible to apply streams 32, 32′ of resin that are wider than those of the nozzles 50, 50′ of rectangular cross-section. The resin leaving the nozzles 51, 51′ then covers substantially the entire surface of the electrical connections to be covered.

[0203] The nozzles 50, 50′ used for resin application close to the slots of the stator, for their part, are for example of circular cross-section. It is not necessary to use duckbill nozzles for application of the resin to the entrance of the slots since it will migrate to fill the slots. In addition, the nozzles of circular cross-section are less bulky than the duckbill nozzles; it is therefore advantageous to use these two types of nozzles to implement the impregnation method.

[0204] In the embodiment of FIGS. 9a, 9b and 9c, the resin is applied by three nozzles 60, 60′,61. Two first nozzles 60 and 60′ are dedicated to applying a resin in the slots of the stator to carry out the impregnation. The second nozzle 61 is dedicated to applying a resin to the electrical connections.

[0205] The first two nozzles 60, 60′ are arranged at each of the two axial ends of the stator. One of the nozzles is arranged inside the electrical conductors when the stator is observed along its longitudinal axis and the other is arranged outside the electrical conductors. For example, in a first step, illustrated in FIG. 9a, the nozzle 60′ is placed outside the electrical conductors and the nozzle 60 is placed inside the electrical conductors. Then, in a second step, illustrated in FIG. 9b, the arrangement of the nozzles is reversed, that is to say, the nozzle 60′ is arranged inside the electrical conductors and the nozzle 60 is arranged outside the electrical conductors. This displacement of the nozzles makes it possible to improve the filling of the slots.

[0206] After the resin is applied in the slots, the second nozzle 61, visible in FIG. 9c, is put into operation to apply resin to the electrical connections. This second nozzle 61 is arranged on the side of the stator that comprises the electrical connections.

[0207] In the embodiment that has just been described, the same nozzles are not used to apply the resin in the slots and to apply it on the electrical connections. These steps can thus be done simultaneously on two different stators to reduce production time.

[0208] Of course, the claimed invention is not limited to the embodiments that have just been described, and the rotor associated with the described stator can be wound, with a squirrel cage or with permanent magnets, or else with variable reluctance.