FR2843246A1 - Fixing procedure for three-phase electrical winding in star configuration to support uses polymerizable varnish in support slots - Google Patents

Abstract

The procedure, in which conductors are fixed in receiving slots in a support, especially a stator of a rotary machine, consists of coating the inner surfaces of the slots with an insulator including a polymerizable varnish, preferably made from a thermoplastic polymer with a melting point above the maximum operating temperature of the machine. The conductors are then fitted into the slots and the varnish is heated by Joule effect to a temperature at which it is fluid and allows it to polymerize as it cools. The phase windings (P1 - P3; P4 - P6) are fitted in a star-shaped configuration between the terminals of an electrical power source.

Description

The invention relates to a method of mounting an electric winding to the

  less three-phase in star configuration formed by a plurality of pin-shaped electrical conductors electrically connected to each other, on a winding support body, for a rotary electrical machine, in particular the stator of such a machine, with immobilization of the conductors in the conductor receiving slots, provided in the

support body.

  By French patent NO 2 809 546 there is known a method of immobilizing between them a large number of conductors of circular cross section and covered with a connecting material inside the notches of a stator of a machine rotating electric, according to which the electrical conductors are heated by the Joule effect by circulating an electric current through the winding. Thanks to the heating thus obtained of the conductors, the bonding material heated to its melting temperature fills the gap between the conductors. This bonding material serving as

  glue while cooling immobilizes the conductors.

  It has proved necessary for Joule heating to properly control the temperature of the copper of the conductors and the best method is to measure the temperature by the variation of the resistance during

their warming up.

  It is then necessary to ensure that all the conductors are traversed by the same current. However, this requirement is difficult to satisfy when the winding is of the at least three-phase and pin type and

  has a star configuration.

  The object of the present invention is to propose a method enabling the problem caused by

the star coupling of the winding.

  To achieve this object, the method according to the invention is characterized in that the internal faces of the notches are covered with an electrical insulator provided with a polymerizable varnish, in that the conductors which constitute the winding are placed in the notches covered with insulation, in that, by means of the winding, the polymerisable varnish is heated by the Joule effect by mounting the phase windings (Pl to P3 P4 to P6) in star configuration in series between the terminals of an electrical energy source, at a temperature which allows polymerization of the varnish during

of its cooling.

  According to a characteristic of the invention, for a configuration of star phase winding before the establishment of the neutral point by connecting the inputs of the three phase windings, the output of a phase winding is connected to the positive terminal of the source of electrical energy, connects the input of this phase winding to the input of another phase winding, establishes an electrical connection between the output of this last phase winding and the input of the third phase winding whose output is connected to the

source negative terminal.

  According to another characteristic of the invention, for a hexaphase winding formed by two three-phase star configurations, the windings of each star configuration are connected in series between the positive and negative terminals of the electric power source. According to yet another characteristic of the invention, for a hexaphase winding formed by two three-phase star configurations, without constitution of the neutral point, the phase windings of the two star configurations are mounted in series between the terminals

  positive and negative of the electric power source.

  According to yet another characteristic of the invention, the outputs of two phase windings of a star configuration are connected to the positive and negative terminals of the electric power source, interconnects the input of one of the two windings to the input of the third phase winding of this star configuration, establishes a link between the output of this third winding and the output of a phase winding of the other star configuration, connects the input of this winding to the input of a second winding of this other configuration, establishes a connection between the output of this second winding at the input of the third winding and establishes a connection between the output of this third winding and the input of the winding of the first star configuration whose output is connected to

  the other terminal of the electric power source.

  According to yet another characteristic of the invention, the conductors are produced, the end portions of which must serve as inputs in the form of a

  single pin of special shape, in the winding.

  According to yet another characteristic of the invention, the neutral point is established after the operation of immobilizing the conductors in the notches by polymerization of the varnish, by connection of the end of the pin constituting the inlet of the third winding to

  the pin joining the two other entrances.

  According to yet another characteristic of the invention, for a winding formed by two three-phase star configurations whose inputs of the phase windings are combined to form the neutral point, the neutral of a configuration is connected to a terminal of the source d electrical energy and the neutral of the other configuration to the other terminal of the source and establishes an electrical connection between each output of a configuration to an output of the other configuration in star. The invention will be better understood, and other aims, characteristics, details and advantages thereof

  will appear more clearly in the description

  Explanatory which will follow made with reference to the attached schematic drawings given solely by way of example illustrating several embodiments of the invention and in which: - Figure 1 is a view in axial section of a rotary electric machine, namely an alternator, to which the invention is applicable; - Figure 2 is a perspective view of a hexaphase winding stator for a rotary electric machine according to Figure 1; - Figure 3 is a schematic electrical representation of a hexaphase winding as shown in Figure 2; - Figure 4 is a portion of an axial sectional view of a stator according to Figure 2; - Figure 5 is a view illustrating a first embodiment of the method according to the invention for a hexaphase winding of a stator for a rotary electric machine of the type of Figure 1; - Figure 6 is a schematic and simplified view of a stator provided with a winding of which only three inputs are shown and which is suitable for the method according to Figure 5; - Figure 7 illustrates, schematically, a second embodiment of the method according to the invention for a hexaphase winding for a stator of a rotary electric machine according to Figure 1; - Figure 8 illustrates a third embodiment of a method according to the invention, for a stator of a rotary electric machine of the type of

figure 1.

  Before specifically describing the subject of the invention, we will first describe, briefly, with reference to FIG. 1, the general structure of a rotary electric machine to which the invention is applicable. The electric machine comprises, going from left to right of FIG. 1, that is to say from front to back, a drive pulley 1 secured to the front end of the shaft 2, the end of which rear carries slip rings (not referenced) belonging to a manifold 3. The axis of the shaft 2 constitutes the axis of

machine rotation.

  Centrally, the shaft supports the rotor 4 with an excitation winding 5, the ends of which are connected by electrical connections to the collector 3 in contact with brushes (not referenced) belonging to a brush holder (partially visible ) connected to a non visible voltage regulator. The rotor 4 is here a claw rotor comprising two front and rear pole wheels 6, 7 each carrying a front fan 8 and rear respectively 9. The references 11 and 13 designate the front and rear bearings of the machine. These bearings are interconnected, for example by means of tie rods, to form a casing carrying at its outer periphery a stator 10. The bearings 11, 13 each carry a ball bearing centrally for

  rotary mounting of shaft 2 and rotor 4.

  The fans create cooling air flows such as, for example, indicated by arrow lines, the bearings 11, 13 being provided

  air inlet and outlet openings therefor.

  The rotor 4 is mounted coaxially and rotatable inside the stator 10 of the hexaphase type, comprising in the example shown in FIG. 2 a cylindrical body 12 of axis XX 'carried by the bearings 11, 13 supporting two series of three phases P1 to P3 and P4 to P6, in a manner known per se, as shown in FIG. 3. Each phase P1 to P6 is formed by a plurality of electrically conductive elements 14 electrically connected to each other by being here connected in series along the periphery of the stator 10 between an input respectively El to E6 and an output respectively Si to S6, to form at least one winding per phase. The outputs 51 to 56 are connected to a diode rectifier bridge (not referenced) for

  rectify the alternating current produced by the stator.

  As can be seen in FIG. 2, the cylindrical body 12, in the form of a pack of sheets, comprises in its radially internal face radial notches L for receiving at least four phase 14 conductive elements. The conductive elements are juxtaposed in the notch L in the radial direction to form at least four layers of conductive elements C1 to C4, as seen in Figure 4. The four conductive elements engaged in a notch constitute two pairs of conductive elements. For more details on the mounting of the conductive elements, see

in document FR-A-2 819 117.

  Thus, with reference to FIG. 2, it can be seen that each conductive element 14 has the shape of a U-shaped pin 14 which extends between two notches L, L ', each of which receives a branch of the pin. This arrangement of the conductive elements is obtained by twisting the pins, with the heads 14c being on the same axial side 12a of the stator 12 and forming a bun 16. In a manner also known per se, the free ends of the branches of each conductive element in pins 14 protrude from the second axial side 12b of the body 12 and are electrically each connected to the free end of another hairpin conductive element, advantageously by welding, thus forming a second

bun 18.

  FIG. 2 shows that the outputs S1 to S6 extend in the axial direction of the stator out of the bun 16 and thus constitute portions of a conductor which does not have the shape of a U-shaped pin but the shape of a special pin, in a manner known per se. The inputs E1 to E6 also constitute end portions of conductors also of specific shape. The inputs are electrically connected to form the neutral points in Figure 3. The types of connection and the shapes of the input ends can

-2843246

  be different and determine the different modes of implementing the invention which are described in

referring to Figures 5 to 10.

  The object of the invention is to propose a method which makes it possible to immobilize the conductors 14 inside their notch L of the stator so as to eliminate any relative movement between the copper of the conductors and the iron of the stator. Indeed, the slightest movement leads to degradation of the insulation and a

  risk of short circuit to ground.

  To achieve this goal, an impregnation varnish is provided on the insulator here prepreg indicated at 19 in Figure 4, which covers the internal face of the notch. The immobilization of the conductors is obtained by polymerization of the impregnation varnish. In order to carry out the polymerization, the stator is heated to a temperature making the varnish fluid so that it can fill the gaps between the copper of the conductors and the iron of the stator inside each notch. By polymerizing when the stator cools, the varnish hardens and ensures perfect immobilization of the conductors in the notch,

  which ensures good mechanical resistance to vibrations.

  It has been found that the best method of heating the stator is to pass an electric current through the conductors. This current, by Joule effect, causes the conductors and consequently the stator to heat up. However, for this purpose a good control of the temperature of the copper and thus of the current flowing through it is essential. The difficulty comes from the fact that the winding is in star coupling on the stator

as shown in Figure 3.

  The invention proposes a method which solves the problem which has just been explained. This process will be described

  below in different versions of implementation.

  FIGS. 5 and 7 illustrate the application of the method to a hexaphase winding system with two configurations of star phase winding, electrically offset by 300, the neutral points of which are not connected. Indeed, as seen in FIGS. 5 and 7, only the inputs E2 and E3 of a star configuration, and E5 and E4 of the other configuration are

  connected while the inputs El and E4 are isolated.

  FIG. 6 schematically shows a winding produced according to this concept. It is noted that the conductors intended to constitute the inputs E2 and E3 are produced in the form of a single pin of specific U-shaped shape while the input El is formed by the output end of the bun, of another pin special. The end E1 can be connected by soldering to the pin comprising the inputs E2 and E3, at 22. It is the same for the inputs E4 to EG; the inputs E5 and E6 being produced in the form of a U-shaped pin. To ensure the immobilization of the conductors of the winding system illustrated in FIG. 5 in their notches, before the connection by welding of the pin input El on the common pin of the inputs E2 and E3 together, the six phase windings Pl to P6 are mounted in series between the + and - terminals of an electrical power source using two power connections 24 and 25. Since the inputs E2 and E3 of the first phase winding configuration Pi to P3 and the inputs E5 and E6 of the second phase winding configuration P4-P6 are already connected, the series connection of the the set of phase windings consists in establishing between the output S3 of the phase winding P3 and the output S5 of the phase winding P5 an electrical connection 26, between the output S6 of the phase winding P6 and the input E5 of the phase winding P5 a link sound 27 and finally between the output S4 of the phase winding P4 and the input El of the winding

phase Pl a bond 28.

  The implementation of the method according to the invention in accordance with FIG. 5 involves the establishment of two power connections and six series connection connections, namely the connections of outputs S2 and Sl at the terminals of the source and two connections for the establishment of each link 26, 27 and 28. This implementation has the advantage that the circuit in series of flow of the electric heating current has a fairly high resistance which is therefore easy to measure. This ensures very good temperature control during the heating process of the stator for the subsequent polymerization of the impregnation varnish. The implementation of the method applied to a winding as shown in FIG. 7 consists in connecting in series only the three phase windings of each star constellation between the + and - terminals of the power source, namely windings Pl to P3 and P4 to P6. More precisely, the output S2 is connected at 30 to the positive terminal of the electric power source and the output Sl to the negative terminal of this source at 31 and a connection 32 is established between the output S3 and the input El by two connections. In parallel with this heating current circuit of the first star configuration, a series circuit for the second star configuration is correspondingly established by connecting the output S5 at 33 to the positive terminal of the power source, and the output S4 at 34 to the negative terminal of this power source and by establishing two connections

  link 34 between output S6 and input E4.

  The implementation of the method according to FIG. 7 requires making four power connections, that is to say connections to the power source, and four connection in series. Compared to the implementation according to FIG. 5, that of FIG. 7 requires the establishment of two circuits in series but only

of four connections.

  The method in its implementations shown in Figures 5 and 7 has the advantage that there is only one weld to be made to achieve the neutral point. This weld 22 is made at the end of the process, for example when the stator is loaded. So, for finishing the stator, at the end of the process, it suffices to

  make a bend and weld and isolate the neutral point.

  FIG. 8 illustrates another embodiment of the invention, which involves the winding of the stator with a neutral point already welded. A piece of wire protrudes from the bun and makes the electrical connection. In Figure 6 there is shown in broken lines the end noted 37 of the pin. At the end of the heating and polymerization process, it suffices

  cut the end of the wire and establish the insulation.

  Since the neutral point is already established for each star configuration by interconnection of the inputs El to E3 and E4 to E6, the implementation of the method according to the invention according to FIG. 8 implies the connection at 39 of the neutral point of a configuration at the positive terminal of the power source and the connection at 40 of the neutral point of the other star configuration to the negative terminal of the power source and the establishment of a connection 41 between the output S2 and the output S6, an electrical connection 42 between the output S3 and the output S5 and a connection 43 between the outputs

Sl and S4.

  This implementation requires two power connections and six serial connection connections. The finish of the stator is simple since it suffices to cut the wire of the

  neutral point and protect it after welding.

  Of course in the context of FIG. 8, with the neutral point already established, the inputs can be connected in different ways. For example, the inputs are identical and linked together by a piece of electrical connection as shown in FIG. 2, this piece being extended circumferentially to carry

  the tip 37, of axial orientation, of FIG. 6.

  The above description clearly highlights

  the particularity of the invention and the advantage it provides. Thanks to the invention, the electrical insulator is provided in advance (prepreg) with a polymerization varnish, the final temperature of which is well controlled because the conductors

  electric are traversed by the same current.

  The polymerization varnish is advantageously a polymer of the thermoplastic type, the melting point of which is higher than the maximum temperature of

  operation of the rotating electric machine.

  In one embodiment, the stator equipped with electrical conductors and electrical insulators is immersed in a varnish in the liquid state, the temperature of which is then increased by means of controlled heating by means of the winding. This temperature is chosen to allow polymerization of the varnish when it cools. In other words, the equipped stator is immersed in a varnish whose temperature is lower than that of the prior art, which corresponded to the final temperature. This is possible thanks to

  electrical conductors traversed by the same current.

  As a variant, the insulators and the electrical conductors are prepregs as described for example in the document FR-A-2 809 546 cited above, and heating is carried out using a winding to bring it to its final temperature. which allows its polymerization during

its cooling.

  In all cases, the polymerization varnish is heated to a final temperature below the

  melting temperature of electrical insulators.

Claims (11)

  1. A method of mounting an electrical winding at least three-phase in a star configuration, formed by a plurality of electrical conductors in the form of a pin electrically connected to each other, on a support body of the winding, for a rotary electrical machine, in particular the stator of such a machine, with immobilization of the conductors in the notches for receiving the conductors, provided in the support body, characterized in that the internal faces of the notches (2) are covered with an electrical insulator (19) provided with a polymerizable varnish, in that the conductors which constitute the winding are placed in the notches covered with the insulation, and in that, using the electric winding, the polymerizable varnish is heated by Joule effect at a temperature which allows a polymerization of the varnish during its cooling, by mounting the phase windings (Pl to P3; P4 to P6) in star configuration in series between   the terminals of an electric power source.   2. Method according to claim 1, for a configuration of star phase winding before the establishment of the neutral point by connection of the inputs of the three phase windings, characterized in that one connects the output (S2) of a phase winding (P2) at the positive terminal (+) of the electric power source, connects the input (E2) of this phase winding (P2) to the input (E3) of another winding of phase (P3), establishes an electrical connection between the output (S3) of this last phase winding to the input (El) of the third phase winding (Pi) whose output (Si) is connected to the negative terminal (- ) of the source.   3. Method according to claim 2 for a hexaphase winding formed by two three-phase star configurations, characterized in that the windings (Pi to P3; P4 to P5) of each star configuration are connected in series between the positive terminals and   negative of the electric power source.   4. Method according to claim 1 for a hexaphase winding formed by two three-phase star configurations, without constitution of the neutral point, characterized in that the phase windings (Pi to P6) of the two star configurations are mounted in series between the positive and negative terminals of the source of electrical energy.   5. Method according to claim 4, characterized in that the outputs (S2), (Si) of two phase windings (P2), (Pl) of a star configuration are connected to the positive and negative terminals of the electric power source, interconnects the input of one of the two windings (P2) to the input (E3) of the third phase winding (P3) of this star configuration, establishes a link (26) between the output ( S3) from this third winding (P3) to the output (S5) of a phase winding (P5) of the other star configuration, connect the input (E5) of this winding to the input (E6) d '' a second winding (P5) of this other configuration, establishes a connection (27) between the output (S6) of this second winding at the input (E4) of the third winding and establishes a connection (28) between the output (S4 ) of this third winding (P4) and the input (El) of the winding (Pl) of the first star configuration whose output (Si) is connected to   the other terminal of the electric power source.   6. Method according to one of claims 2 to 5,   characterized in that the conductors are produced, the end portions of which must serve as inputs (E2), (E3); (E5), (E6) in the form of a single pin of special shape, in the winding.   7. Method according to claim 6, characterized in that the neutral point is established after the operation of immobilizing the conductors in the notches by polymerization of the varnish, by connection of the end of the pin constituting the inlet (E1, E4) of the third winding with the pin joining the two other inputs (E2, E3; E5, E6). 8. Method according to claim 1, for a winding formed by two three-phase star configurations whose inputs of the phase windings are combined to form the neutral point, characterized in that the neutral of a configuration is connected to a terminal from the source of electrical energy (at 39) and the neutral of the other configuration at the other terminal of the source (at 40) and establishes an electrical connection (41, 42, 43) between each output (S2), (S3), (S4) from one configuration to one output (S6), (S5), (S4) from the other star configuration.   9. Method according to one of claims 1 to 7,   characterized in that the electrical insulator is provided with a polymerization varnish, advantageously formed by a polymer of the thermoplastic type whose melting temperature is higher than the maximum temperature of   operation of the rotating electric machine.   10. Method according to one of claims 1 to 9,   characterized in that the stator equipped with the electrical conductors and electrical insulators is immersed in a varnish in the liquid state, the temperature of which is then increased by the above-mentioned Joule effect at a temperature allowing polymerization of the varnish during the cooling of it.   11. Method according to one of claims 1 to 9,   characterized in that electrical conductors preimpregnated with a polymerization varnish are used, provides heating by the above-mentioned Joule effect by virtue of the circulation of a current through the winding, at a temperature allowing the varnish to polymerize during cooling.