Device having a housing with a drainage opening and an elongated terminal passing through an insulating interface for connecting a servomotor to an electrical cable

A device for connecting a servomotor to at least one electrical cable includes an external housing with at least one cable input, blocked by the cable in operation, and an opening closed by an electrical connection element and forming an interface with the servomotor. The electrical connection element includes a wall of an insulating material and elongate electrical contacts that extend through the wall in a direction substantially orthogonal to the wall, each electrical contact including an inner end inside the device for connection to an electrical cable, and outer end outside the device for being connecting to a corresponding electrical contact of the servomotor. The external housing includes an opening for draining fluid from inside the device in the operational configuration device, and the wall of the electrical connection element extends along a portion of the inner end of the electrical contacts.

FIELD OF THE INVENTION

The present invention relates to a device for connecting a servomotor to at least one electrical cable. It also relates to a servomotor provided with such a device.

BACKGROUND

A servomotor is designed to generate a precise movement of a mechanical component, for example an industrial valve, according to an external control. A servomotor is thus a motorized system capable of achieving predetermined positions, then maintaining them. The position is, in the case of a rotary servomotor, a corner position, and, in the case of a linear servomotor, a distance position. The start-up and preservation of the predetermined position are controlled by the external control via at least one electrical cable.

To connect the servomotor to the cable, it is known to use a connector. A connector for this type of application typically comprises at least one cable input, as well as an opening intended to be closed by an electrical connection element suitable for being connected to the servomotor.

In certain cases, for example in the case of an incident in a nuclear power plant, the servomotor can be located in a high steam pressurized housing. Due to the pressure gradient between the outside and the inside of the connector, steam risks penetrating the cable and migrating through the sheath of the cable to the inside of the connector and then penetrating the servomotor, which risks greatly damaging the electrical equipment of the servomotor.

One known solution for preventing this steam migration consists of pouring resin in the connector, as well as inside the sheath of the cable, so as to submerge the wires of the cable in the resin.

This technique is, however, difficult to implement and is very expensive. Moreover, due to the presence of the resin, it becomes impossible to intervene in the cable.

The invention aims to resolve these drawbacks.

SUMMARY OF THE INVENTION

The invention proposes a device for connecting a servomotor to at least one electrical cable, making it possible to greatly limit the migration of liquid from the sheath of the cable towards the connecting device, the connecting device being simple and cost-effective to produce.

The invention thus relates to a device for connecting a servomotor to at least one electrical cable, the device comprising an external housing with at least one cable input, blocked by the cable in the operational configuration of the device, and an opening intended to be closed by an electrical connection element forming an interface with the servomotor, the electrical connection element consisting of a wall made from an insulating material and provided with elongate electrical contacts that extend through the wall in a direction substantially orthogonal to the wall, each electrical contact including one end inside the device suitable for being connected to an electrical cable, an end outside the device capable of being connected to a corresponding electrical contact of the servomotor.

In the device according to the invention, the external housing includes an opening for draining fluid from inside the device in the operational configuration of the device, and the wall of the electrical connection element extends along a portion of the inner end of the electrical contacts.

The presence of the fluid drain opening in the external housing enables an instantaneous pressure balancing between the outside and the inside of the connection device, which limits the risks of steam migration from the sheath of the cable to the inside of the device.

Moreover, the particular arrangement of the wall makes it possible to increase the travel distance of the electrical current between the electric contacts.

In order to reinforce the sealing of the device, each electrical contact can comprise an intermediate portion situated between the inner end and the upper end and provided with an annular slot, and said wall extends so as to fill in said slots.

To also increase the travel distance, at least one separating element protruding from the wall of the metal connection element can be positioned between inner ends of electrical contacts.

The outer end of the electrical contacts of the device can constitute a female plug, suitable for being connected to a male plug of the corresponding electrical contact of the servomotor.

The female plug can be surrounded by a coaxial element made from an insulating material, which improves the electrical insulation thereof.

The external housing can comprise a power cable input and a data transfer cable input.

The invention also relates to a servomotor connected to a device described above.

The invention lastly relates to the use of such a servomotor in a nuclear power plant.

DETAILED DESCRIPTION

As illustrated in1, the connection device1according to the invention is connected to a servomotor2. The device1comprises an external housing9comprising two cable inputs3,4. The input3is for example suitable for receiving a power cable of the motor, while the input4is suitable for receiving a data transfer cable. Although two cables3,4are shown, the device1can comprise only one input, suitable for receiving either of the electrical cables. The inputs3,4are advantageously provided with a cable gland in order to ensure sealing between the cable and the input3,4.

The device1also comprises a sealed electrical connection element5, for example in the form of a plate, made primarily from plastic material, suitable for being connected to an electrical connection element6, for example in the form of a plate, of the servomotor2. The electrical connection element6is connected to an external housing12of the servomotor2.

The connection element5comprises a wall11and electrical contacts7extending through the wall11. The electrical contacts7are intended to receive electrical wires coming from the electrical cable(s) and to connect them to the corresponding electrical contacts8of the electrical connection element6of the servomotor2.

According to the invention, the external housing9of the device1comprises an opening10, positioned in the lower area of the external housing9in the operational configuration of the device1and making it possible to drain liquid in the event liquid is present in the device1. For example, in the case of a nuclear accident, water can penetrate inside the device1coming from the electrical cable(s). During the accident, the steam pressure increases abruptly, but the opening10enables an instantaneous pressure balancing between the outside and the inside of the device1, which limits the steam migration from the cable(s) towards the device1. Indeed, if there was no opening10, the inside of the device1would be at atmospheric pressure, which would promote the steam migration towards the inside of the device1due to the large pressure deviation between the outside and the inside of the device1.

If steam penetrates the device1via the opening10, the steam will condensate inside the device1. The water thus formed then flows towards the outside of the device via the opening10.

FIGS. 2 and 3are detailed views of the electrical contacts7and8respectively. The electrical contact7is longitudinal and extends in a direction substantially orthogonal to the wall11of the electrical connection element5. The contact7comprises an end inside the device comprising an inner orifice, not shown, and an outer end of the device comprising an outer orifice7b. The inner and outer orifices7bare made in a substantially cylindrical metal portion of the electrical contact7. The metal portion is surrounded by plastic material of the wall11.

The inner orifice is made on the inner side of the device1. A wire coming from the power cable is introduced into the inner orifice and is fastened to the contact7by gripping using a screw. The orifice7bis made on the outer side of the device1. The orifice7bconstitutes a female contact in which a corresponding male contact8bof the connection element6of the servomotor2is introduced. The orifice7bis surrounded by a coaxial element11cmade from a plastic material.

To reinforce the sealing between the inner orifice and the outer orifice7bof the wall11, the electrical contact7advantageously comprises a slot15, situated between the inner end and the outer end of the electrical contact7, and preferably positioned on the entire perimeter of the metal portion7, in the form of a groove15. During molding of the plastic material of the wall11, the shrinking leads to an expansion of material longitudinally and radially relative to the axis of the electric contact7. Owing to the presence of the groove15, the plastic material bears on faces perpendicular to the axis of the contact7. The groove15thus formed is filled with plastic material and ensures sealing of the wall11, even after shrinking.

It is also possible, to reinforce the sealing, to position a sheath, for example a thermoshrinkable sheath, on the wires coming from the cable and on the inner end of the contacts7. The device1can also be filled with a filling material, advantageously a resin. The filling can be done using a filling opening, not shown, positioned in the external housing9of the device1.

The wall11extends, via a portion11a, over a portion of the inner end of the electrical contact7. In this way, the travel distance of the electrical current between two electrical contacts7is increased. Subsequently, the electrical insulation distance between the electrical contacts7is increased.

Moreover, a separating element11bprotruding from the wall11is intended to increase the travel distance of the electrical current between the electrical contacts7.

The electrical contact element6, as illustrated in3, comprises a wall13and metal electrical contacts8positioned substantially orthogonal to the wall13, and extending on either side of the wall13. Each electrical contact8comprises, on the side of the connection device1, a male contact8bsuitable for being introduced into a corresponding female contact7bof the electrical connection element5of the device1. To facilitate the insertion of the male contacts8binto the female contacts7b, the male contacts8bare in floating contact with the wall13of the electrical connection element6. The internal connection to the servomotor2is done using connection elements16, for example cylindrical lugs, with or without insulation, that are for example plugged in or clipped on the inner end of the electrical contacts8.

FIG. 4is a front view of the electrical connection element5. The electrical connection element5comprises three concentric rows of electrical contacts7. The two external rows of electrical contacts7are intended to transmit data from the servomotor2to an external command, in particular data concerning the position of the mechanical element actuated by the servomotor2and/or data concerning the torque applied to the mechanical element. The inner row of electrical contacts7comprises three contacts7intended to power a triphase motor, as well as an electrical contact7intended to be grounded. The electrical connection element5also comprises orifices17for fastening the electrical connection element5by screwing on the external housing9of the device1.

FIG. 5illustrates the fastening of the electrical connection element5to the external housing9of the device1. After connecting the electrical cables to the electrical connection element5, the latter part is fastened to the housing9using screws18, with o-ring seals19,20. The device1is then connected to the electrical connection element6of the servomotor2. A mistake-proofer ensured by the shape of the electrical connection element5advantageously prohibits any incorrect assembly. Lastly, the external housing9of the device1is screwed to the external housing12of the servomotor2.