MULTI-LAYER CONNECTOR WITH CONDUCTORS INSULATED BY

ENAMELING

Technical field of the invention

The invention relates to the technical field of electrical installations, conductors and power distribution, as well as to the field of apparatus and methods for manufacturing such devices.

More particularly, the invention relates, inter alia, on the one hand to a multilayer connector, also called an electrically insulated laminated "busbar", and on the other hand to the method of manufacturing said connector.

Prior art

The term “laminated busbar” is usually understood to mean an electrical interconnection device, which has the functions of electrically connecting the constituent elements of a static converter of electrical energy; but also to ensure the connection connectors provided outside said converter.

This connection occurs in several contexts, for example:

• between power modules such as: insulated gate bipolar transistors (IGBT: Insulated Gâte Bipolar Transistor), integrated gate-switched thyristors (IGCT: Integrated gate-switched thyristor), diodes, and passive components such as capacitors or filters; implemented within this static converter of electrical energy, in particular in the typical power range from 50kW (kilowatt) to 8 MW (megawatt),

• when the "busbar" is directly encapsulated inside the power modules: between semiconductor circuits, and / or between semiconductor circuits and external connections (connection terminals),

especially in the typical power range from 50kW (kilowatt) to 200 kW (kilowatt).

The laminated multilayer connector also has the function of mechanically supporting the various elements involved.

Laminated connectors are generally made of a complex of flat conductors and insulating material (s). However, a "busbar" can also consist of a single flat conductor.

By flat conductor is meant a conductor such that one of its dimensions (preferably its thickness) is much smaller than the others. Such a conductor can be flat or bent.

This stack of flat conductors of different electrical phases justifies the main purpose of the laminated connector compared to connection bars or conventional electrical cables; namely a low inductance.

By way of example, a laminated connector can consist of an assembly of several conductive plates, each plate corresponding to an electrical phase. Lights made in the plates allow the connection of the components arranged on one side with the other plates located below. The components are most often assembled by screwing. There are also connection lugs for connection with the outside of the converter.

Most often, the electrical insulation between the various conductive plates is produced by electrical insulating films of the polyethylene terephthalate (PET), polyethylene terephthalate) (PEN), polyimide (PI) type. . .

Usually, the said insulating film (s) is either stacked (interposed between conductors, one speaks of a stacked or “stacked” laminated “busbar”), or laminated to the flat conductor (laminated busbar laminated).

These technologies have several drawbacks presented below.

In the case of a “stacked” or stacked “busbar”, the films are not glued, and it is necessary to provide a geometric retaining device for its elements at least until it is mounted in the converter. This device is generally in the form of additional fasteners made of an electrically insulating material. Moreover, the isolation distances in the air limit the service voltage level of converters made from such connectors (to approximately 1000 volts).

In the case of laminating, the sheets are most often heat-sealed, which requires, for example, the use of a heating press, a shaping tool and flexible pressure distribution membranes. Such a device consumes a lot of energy, which represents a major technical drawback. Indeed, only about 1% of the energy consumed is used to secure the flat conductors and the film (s), the rest of the energy being dissipated at the level of the metal frame of the press and the tool. .

Due to the thermal inertia of the system and the thermal barrier formed by the flexible membranes, the production time is also long (of the order of 1 to 2 hours) and therefore the hourly productivity low; while future needs for static converters are on the rise (renewable energies, electric vehicles, smart-grid, etc.)

Another technical problem encountered during the lamination of insulating films concerns the quality of insulation of the device and more specifically the quality of insulation of its edges (periphery of the conductor, edges of the openings provided in the conductors, etc.). Indeed, ideally, the laminated "busbars"

with heat-sealed film are produced flat and are then folded if necessary. Posterior folding presents multiple risks: cracking of the film, cracking of the surface coating (for example: nickel plating). In addition, when installing the insulating film (s), care must be taken not to create an air pocket (air-filled cavity between the film and the conductor) or interstices (poor film. glued or unstuck) at the edges, because such defects generate the appearance of parasitic and highly damaging phenomena such as partial discharge phenomena (all the more important as the dielectric field is high), which cause more or less long term the piercing of the insulating film, and consequently the appearance of short circuits. The design of multilayer connectors with a threshold of

Furthermore, the growing need for speed at the circuit level requires the implementation of suitable electronic components with increasing performance, for example based on silicon carbide or gallium nitride. These introduce severe constraints for “busbars”, such as:

• required inductance values ​​even lower than those currently achieved,

• an ability to withstand an operating voltage higher than the voltages currently encountered,

• an ability to withstand a switched current greater than the switched currents currently encountered,

• an ability to withstand an operating temperature higher than the temperatures currently reached.

Thus, in order to meet the constraints mentioned above, film (s) of increasingly efficient materials are currently used, for example films made of PolyEtherEtherKetone (PEEK) or of Polyimide (PI), but which are

much more expensive. Also, the rise in temperature poses the problem of finding films and adhesives resistant to it.

Also, the main technical advantage of these devices, namely: low inductance (compared to traditional wiring), is a consequence of their flattened shape. Thus, obviously, the current technological evolution is based on the principle of downscaling: it is known to achieve increasingly low inductance values ​​by reducing the thickness of the conductors and the films of insulation. This solution nevertheless has an obvious limit, since thinner films are also more fragile and delicate to handle and / or stick.

Knowing in addition that a low inductance makes it possible to limit the overvoltages during the switching of the current in the electronic switches and that an increasingly high threshold for the appearance of partial discharges is required, it is all the more obvious that the he improvement of the performance of multilayer connectors, by the choice of high-performance materials, easily removable and inexpensive, is a technical challenge of importance for the industry.

Insulating conductors by depositing thermosetting colored insulating powder (for example epoxy) which, after curing, forms an insulating barrier, is also known (cn205264989). The minimum thickness of the insulation layer obtained is of the order of 100 microns. Unfortunately, the insulating barrier can crack or crack, causing insulation defects. This phenomenon being common, manufacturers add a flexible insulating film.We know us 6265666 the implementation of an insulating layer obtained

by electrostatic spraying of a thermoplastic powder.

Description of the invention

As demonstrated previously, there is a real need to provide a solution in response to the technical problem of improving the insulation of the flat conductors constituting laminated multilayer connectors (in particular at the edges) and of the application of the chosen insulating material, while maintaining reasonable manufacturing cost and increasing productivity.

The invention described in the present application responds to this need, by proposing an economically attractive solution and increased performance for multilayer connectors produced according to the prescribed method, which does away with the use of films;

To do this, the invention relates first of all to a method of manufacturing a connector device capable, among other things, of making an inter or intra static converter (s) connection of electrical energy (power module circuits, capacitors , filters, connectors,...), said device comprising at least two flat conductors and at least one insulating material, said method being remarkable in that:

• each flat conductor is prepared individually,

• a layer of enamelling varnish in liquid form is deposited on each conductor with a thickness less than the desired final thickness,

• crosslinking of the enamelling varnish layer,

• the application of a layer of enamel varnish and crosslinking is started again until the chosen thickness is reached,

• the conductors of said connector device are assembled by means of a jig and connecting means.

To prepare the conductors, one begins by carrying out a surface treatment such as degreasing and / or deoxidation.

Then a savings is placed on each area of ​​the conductor where an electrical contact must be established before depositing the varnish in liquid form.

These savings are for example chosen from the group comprising: stoppers (for example: in elastic material resistant to heat, and / or waterproof, and / or mechanically fixed, and / or in non-adherent material), adhesives (for example: adhesives peelable). The savings can all be of the same nature or be mixed. They can be reusable or single use. Nevertheless, those skilled in the art know how to choose the nature of the savings, and their number according to the needs of the device to be manufactured.

The conductors can be suspended from a support or maintained via the spare (s), the time necessary for the application of the varnish and its crosslinking.

For the application of the enamel varnish, this is done for example by spraying in thin layers using air as the vehicle carrying the varnish or by projecting only the enamel varnish in liquid form in microdroplets, therefore by spraying.

The installation can also be done by soaking or sprinkling varnish, the viscosity of the enamel varnish which is in liquid form and the roughness of the conductor then dictating the thickness of the deposited layer.

The installation can also be done by centrifugal coating by means of a spinner rotating at high speed the conductor to be enameled. The final thickness of the insulating layer deposited depends on the quantity of initial insulating material, its viscosity and the conditions of rotation (duration, speed of rotation and acceleration)

By depositing thin layers, the risk of an accidental localized lack of varnish is reduced because the layers are deposited independently of each other. The risk of microcavity is reduced. Crosslinking takes place according to the nature of the varnish.

The crosslinking can be done by evaporation of solvent or by chemical reaction with a curing agent. A heat input starts or accelerates the most

often this crosslinking. Crosslinking can also be done by UV for photosensitive resins.

In an alternative embodiment, the layers may not be of the same thickness, nor of the same type of resin. For example, the varnish of the first thin layer can be of polyurethane nature, characterized by good adhesion on a copper surface, and the following ones in more resistant epoxy type varnish. And the last in varnish loaded with colored pigments.

The conductors can be prepared one by one or in batches depending on the means used to deposit the varnish.

When the conductors are ready, they need to be assembled.

To assemble them, we use a mounting jig which will allow the connectors to be positioned relative to each other and to immobilize the conductors relative to each other.

According to a first embodiment, use is made of mechanical components (screw, clip, insert, rivet, etc.) made of insulating material.

According to a second embodiment, adhesives are used in all forms, for example: spots of glue, layer of glue, adhesive film.

In an alternative embodiment, spacers made of insulating material such as a mica sheet or a mat of glass fibers are inserted between two conductors previously covered with an enameled varnish. It is also possible to use a silicone sheet which will be said to be thick (1 to 5 mm, typically 3 mm) in order to compensate for differences in thickness.

Preferably, the mounting jig has means for lateral wedging of the conductors.

The invention also relates to any connector device that can be obtained by implementing the method described. Said connector device is, among other things, suitable for making an inter or intra static converter (s) of electrical energy connection (power module circuits, capacitors, filters, connectors, etc.), that is to say that it is suitable and likely to be used to make a connection:

• Intra-converter, ie for example:

o between at least two power modules (as defined above) belonging to the same converter, or o inside a power module, for example: between at least two semiconductor chips, or between a semi-conductor chip -conductor and an external connection, or

• Inter-converters, ie between at least two converters, for example.

As previously described, the devices (busbar) are generally made up of a complex of flat conductors and of insulating material (s).

According to the invention, the flat conductors are preferably made of copper or aluminum. Advantageously (but not necessarily) the conductors are protected by a surface treatment, such as among others: tinning, nickel plating, silver plating. Preferably, the conductors have a thickness of between 1 and 4 millimeters.

The conductor manufacturing process (for example: punching, bending, injection, casting) is irrelevant, and a person skilled in the art knows how to choose the process best suited to the intended application.

Finally, the invention can be used for various purposes, such as laminated busbars of static electric energy converters, internal laminated busbars of power semiconductor modules, and the Applicant claims in particular the use of the proposed connector device, obtained by the implementation of the method presented, as connector inter or intra static converter (s) of electrical energy.

Description of the drawings

The invention will be clearly understood with the aid of the following description (by way of non-limiting example) of the drawings illustrating the interconnection device and the associated manufacturing method.

FIG. 1 represents two independent conductors, provided with savings to protect the electrical connection areas.

FIG. 2 shows two conductors, still independent and which have undergone the enamelling operations provided for by the process. The savings have been withdrawn. An enlarged section shows the detail of the stacking of the varnish layers.

FIG. 3 shows the two conductors previously enamelled and assembled by pads of adhesive, to form the multilayer connector with conductors insulated by enameling.

Description of general embodiments of the invention

According to the figures, the method according to the invention allows the manufacture of a multilayer connector device 1. This device 1, in accordance with FIG. 1, is made from at least one flat conductor 2, on which is optionally placed a savings 3 in each zone of said conductor 2 where an electrical contact is to be established. The savings 3 can be deposited on one face of the conductor 2, or pass through, at the level of a slot 4 made in said conductor 2. According to the manufacturing process, the installation (s) savings (s) takes place. before applying the varnish (10). In accordance with FIG. 2, one or more layers (11, 12) of enamel varnish 10 are deposited on the conductors 2 prepared and possibly provided with savings 3. Once the savings 3 have been removed,

Preferably, each conductor is individually coated with at least two layers of enamel varnish 10 in liquid form, the layers subsequent to the preceding one are created only if the preceding layer is crosslinked.

The term “enamel varnish 10” is understood to mean a resin which exhibits particular aptitudes of adhesion to the electrical conductor, of electrical resistance, of thermal stability.

Quite preferably, the enamel varnish 10 comprises at least one filler in the form of inorganic particles of size preferably less than 150 μιη, such as for example: silica (Si02), alumina (A1203), magnesia (MgO). Thanks to this inorganic filler, the resin exhibits less deterioration of its electrical characteristics under partial discharge stresses.

This technical possibility makes it possible to obtain a controlled lifetime in the presence of partial discharges, unlike current technology which requires the absence of partial discharges.

Advantageously, the characteristic parameters of said enamelling varnish 10 are chosen from:

- dynamic viscosity: 100 to 4000 mPa.s, and / or

- temperature class: 120 ° C to 240 ° C (120/140/155/180/200/220/240 ° C), according to standard IEC 60085: 2007, and / or

- dielectric strength greater than or equal to 30 kV / mm, and / or

- more preferably the chemical nature is chosen from: polyurethane (PUR), thermoplastic elastomer (TPE).

By way of example, the enamel varnish 10 can be chosen from the VOLTATEX WIRE® range (Dupont).

The enamelling varnish can be crosslinked by the action of heat or by the action of Ultra Violet rays. For the latter, we can retain as an example the company Green Isolight International:

- GII 206 which has a class of 280 ° C and which is based on polyester acrylate;

- GII 200 which has a class of 120 ° C and which is polyalcohol modified acrylate.

For the installation of the varnish 10, the conductor 2 can for example be suspended by means of a hook gripping at the level of a savings 3.

The varnish 10 can then be sprayed onto the conductor 2.

The projection can be carried out in the form of fine particles, by aerosol effect by means of a propellant gas (air or neutral gas such as nitrogen for example) or by pressure.

It is also possible to dip the conductor 2 in a bath or spray it with varnish 10. Another possibility consists in depositing the varnish by centrifugal coating. Preferably, one proceeds by depositing thin layers in order to multiply them. Those skilled in the art will know how to determine the parameters necessary to achieve the desired thicknesses according to the characteristics of the varnishes used. Preferably, according to the method, the step of assembling said device 1 comprises at least one step from: step (s) of bonding, step (s) of mechanical clamping.

Bonding (bonding step) comprises, for example: bonding by press and / or hot bonding and is carried out using an adhesive such as: transfer film adhesive, liquid adhesive.

Advantageously, the method according to the invention is remarkable in that:

• firstly, a layer of enamelling resin 10 of thickness A is deposited, preferably by soaking followed by draining (nevertheless, any

another suitable method - depending on the varnish 10 chosen - can be implemented, such as deposition by spraying or centrifugation),

• then crosslinked said enamel varnish 10 and the removal and crosslinking are repeated.

Those skilled in the art know how to choose the number of iterations of the step cycle presented previously, so as to obtain a final desired thickness B of enamelling varnish 10, coating said flat conductors 2. Among other things, the number of iterations (and therefore the final thickness B) is chosen according to the voltage that the device 1 must withstand - Preferably, said thickness B is between 30 and 200 microns, in order to allow the device to operate at a voltage between 300 and 1250 volts. Preferably, said thickness A is between 3 and 15 microns. A first advantage of these different stages A of deposition of enamelling resin (varnish) 10 is to avoid the creation of microcavities in the thickness of the

A second advantage is to reduce the risk of an accidental localized lack of varnish 10 because the layers are deposited independently of one another. A third will be to take advantage of characteristics specific to each type of varnish 10, for example a first layer with a high adhesion capacity on the conductive surfaces, a following layer with higher mechanical performance, or even a layer of colored varnish 10. identification (for example: varnish including colored pigments; this technical possibility allows unambiguous identification of one conductive layer in relation to another).

The crosslinking of the enamel varnish 10 can for example be carried out spontaneously at room temperature or in an oven, by evaporation of

solvent, by chemical reaction with a hardening agent, or under the action of UV radiation.

According to a variant of the process, the various layers of varnish 10 deposited are of different nature and / or thickness.

Advantageously, according to a variant (assembly step) of the method, the conductors 2 coated with enamel varnish 10 are assembled by means of mechanical parts made of insulating material.

According to another variant (assembly step) of the method, the conductors 2 coated with enamel varnish 10 are assembled by means of adhesive in all forms.

Preferably, as provided in FIG. 3, is inserted between two conductors 2 coated with enamel varnish 10 one (or more) insulating spacers, such as a sheet of insulating material 15 (for example of mica).

Advantageously, the method according to the invention is remarkable in that in advanced variants of the step for preparing the flat conductors 2, this further comprises at least one step for preparing the surfaces, chosen for example among others from: degreasing, dust removal.

Also, the proposed process makes it easier to envision a global ecological approach, by offering the possibility of using aqueous solvents instead of organic solvents in the varnishes.

Finally, the invention relates to any device obtained by the method described above, comprising at least two flat conductors 2 and at least one insulating material: varnish 10 (optionally in multilayer form 11, 12), spacer 15.
CLAIMS

1. A method of manufacturing a connector device (1) capable of making an inter or intra static converter (s) connection of electrical energy, said device (1) comprising at least two flat conductors (2) and minus one insulating material (10, 11, 12, 15), said method being remarkable in that:

• each flat conductor (2) is prepared individually, · a layer of enamelling varnish (10) is deposited on each conductor (2) in liquid form with a thickness less than the desired final thickness,

• the crosslinking of the enamelling varnish layer (10) is carried out,

• the application of a layer of enameling varnish (10) and the crosslinking is started again until the chosen thickness is reached,

• the conductors (2), coated with varnish (10), of said connector device (1) are assembled by means of a template and of connecting means.

2. A method of manufacturing a connector device (1) according to claim 1 characterized in that a savings (3) is placed on each zone of the conductor (2) where an electrical contact must be established before depositing the varnish. (10) in liquid form.

3. A method of manufacturing a connector device (1) according to one of the preceding claims characterized in that the layer of varnish (10) is deposited in fine particles, using a gas as propellant, or by pressure.

4. A method of manufacturing a connector device (1) according to one of claims 1 or 2, characterized in that the layer of varnish (10) is deposited by dipping or spraying.

5. A method of manufacturing a connector device (1) according to one of claims 1 or 2, characterized in that the layer of varnish (10) is deposited by centrifugal coating.

6. A method of manufacturing a connector device (1) according to any one of the preceding claims, characterized in that one proceeds to a crosslinking of the varnish (10), for example by evaporation of solvent or by chemical reaction with a hardening agent or by UV action.

7. A method of manufacturing a connector device (1) according to any one of the preceding claims, characterized in that the different layers of varnish (10) deposited are of different nature and / or thickness.

8. A method of manufacturing a connector device (1) according to any one of the preceding claims, characterized in that the conductors are assembled.

(2) coated with varnish (10) enamelled by means of mechanical parts made of insulating material.

9. A method of manufacturing a connector device (1) according to any one of claims 1 to 7, characterized in that assembles the conductors (2) coated with varnish (10) enameled by means of adhesive under all shapes.

10. A method of manufacturing a connector device (1) according to any one of claims 1 to 9, characterized in that a sheet of insulating material (15) is inserted between two conductors (2) coated with enamel varnish.

11. Connector device (1) capable of making an inter or intra static converter (s) of electrical energy connection, said device (1) comprising at least two flat conductors (2) and at least one insulating material (5). ), this

device (1) being characterized in that it is obtained according to any one of claims 1 to 10.

12. A connector device according to claim 11, characterized in that the enamel varnish (10) comprises at least one filler in the form of inorganic particles.

13. Connector device (1) according to claim 11 or 12, characterized in that the enamel varnish (10) comprises colored pigments.

14. Use of the connector device (1) according to one of claims 11 to 13 as connector inter or intra converter (s) static (s) of electrical energy.