Short circuit detection device and vehicle with it

Description

[0001] The present invention relates to a short-circuit detection device, comprising a power supply terminal, a powered terminal, a connecting element of the power supply terminal and the powered terminal, the power supply terminal, the powered terminal and the connecting element forming an electrical connection section, which is devoid of electrical insulation, the power supply terminal and the powered terminal each comprising an insulated section provided with electrical insulation, and the short-circuit detection device comprising an element for detecting electric arc emanating from the electrical connection section.

[0002] The electrical connection of the motor to its power supply is known via a terminal box. This allows for simple coupling and decoupling of the motor from its power supply while ensuring, within the terminal box, the detection of non-insulated electrical connections in a closed enclosure accessible only by opening the terminal box cover.

[0003] Degraded operation can occur in the terminal box, introducing short circuits and arcs that can lead to the destruction of the terminal box or even the winding. Short circuits generally occur between two phases. In some cases, such as with an asynchronous motor, disconnecting the power supply will stop the short circuit.

[0004] For motors using permanent magnets, switching off the power supply does not always stop a short circuit. Indeed, if the power disconnection point is upstream of the short circuit, the short circuit will continue to propagate if the motor continues to rotate, driven by the load, as in the case of a railway vehicle with multiple traction motors.

[0005] A detection device is known from patent application FR2737615A1. Other devices are known from US6512444B1, DE2644422A1, US2021143629A1, DE102015016696A1 and US4067052A.

[0006] EP3595123 describes a power distribution system. DE19631088 describes a device for protecting an electrical installation. US2019 / 319451 describes a window heating control system.

[0007] The invention aims to provide a short-circuit detection device that is simple and economical, while also being reliable.

[0008] To this end, the invention relates to a detection device as indicated above, characterized in that the detection element comprises an electrically conductive element, having a detection section, and a detection coating which is electrically insulating and thermally degradable and which surrounds the detection section, and in that the detection section extends to a detection distance from the electrical connection section.

[0009] Depending on specific embodiments of the detection device, it may include one or more of the following characteristics: the detection distance is less than the range distance of an electric arc emanating from the electrical connection section and suitable to thermally degrade the detection coating, and / or the detection distance is such that on the one hand the breakdown voltage between the detection section and the electrical connection section in the presence of the detection coating is greater than a nominal voltage of the supply terminal, and on the other hand the breakdown voltage between the detection section and the electrical connection section, in the absence of the detection coating, is less than a nominal voltage of the supply terminal, and / or the detection distance is less than a distance between the electrical connection section and an additional electrical circuit element, which is the electrical circuit element closest to this electrical connection section;the detection coating is a coating adapted to degrade under the effect of heat generated by an electric arc, preferably in which the detection coating comprises or is made of heat-sensitive polymer(s), such as PVC, fluoropolymer or polypropylene, chemically doped leading to a decrease in electrical resistance in the case of an increase in temperature; the electrically conductive element is connected to electrical earth or electrical ground; the short-circuit detection device includes a short-circuit detection module, which is adapted to detect an electrical grounding of the supply terminal and the supplied terminal via the electrically conductive element;the electrically conductive element of the detection element has a circular, elliptical, square or rectangular cross-section and / or in which the electrically conductive element is in the form of a wire, bar or sheet; the detection element either consists of a single branch or forms a two-branch loop; the short-circuit detection device includes a terminal box, the supply terminal is disposed in the terminal box, the supplied terminal is disposed in the terminal box, the connecting element is disposed in the terminal box, and the detection section is disposed in the terminal box;The detection device includes an additional power supply terminal disposed in the terminal box, an additional powered terminal disposed in the terminal box, an additional connecting element connecting the additional power supply terminal and the additional powered terminal and disposed in the terminal box, the additional power supply terminal, the additional powered terminal and the additional connecting element defining an additional electrical connection section, devoid of electrical insulation, and the detection distance is less than the distance between the electrical connection section and the additional electrical connection section, and preferably wherein the terminal box includes a separating wall between the electrical connection section and the additional electrical connection section.

[0010] The invention also relates to a vehicle comprising an electric motor having at least two phases and a short-circuit detection device connected to the electric motor, characterized in that the short-circuit detection device is a device as defined above.

[0011] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the attached drawings, in which: [ Fig 1 ] There Figure 1 schematically illustrates a vehicle comprising a detection device according to the invention; Fig 2 ] There Figure 2 shows a cross-section of the detection device along line II-II of the Figure 1 ; And [ Fig 3 ] There Figure 3 shows a variant of a detection device Figures 1 And 2 the view of the Figure 3 corresponding to the view of the Figure 2 .

[0012] In what follows, expressions such as "connected", "linked", "isolated" refer, unless otherwise indicated, to electrical characteristics and not to mechanical characteristics.

[0013] On the Figure 1 is represented a vehicle designated by the general reference 2. Vehicle 2 is in this case a railway vehicle such as a locomotive and is represented very schematically.

[0014] The vehicle 2 comprises a chassis 4, connected to electrical ground or to the electrical chassis, and at least one electric motor 6, which may be a synchronous or asynchronous motor. The electric motor 6 has two or three phases, one phase P1 being shown in more detail and an additional phase P2 being shown schematically (see below). The electric motor 6 is adapted to drive the vehicle's traction wheels. The vehicle 2 includes an electrical voltage source 8, which may be a direct current (DC) or alternating current (AC) voltage source, and which is adapted to supply electricity to the electric motor 6. For this purpose, the electric motor 6 is connected to the electrical voltage source 8 by an electrical connection circuit 9.

[0015] The electrical connection circuit 9 includes a short-circuit detection device 10.

[0016] The short-circuit detection device 10 includes a power supply terminal 12, connected to the electrical voltage source 8, a powered terminal 14, connected to the electric motor 6, in this case to the winding of a stator 16 of the electric motor.

[0017] The short-circuit detection device 10 includes a connecting element 18 between the supply terminal and the supplied terminal. This connecting element 18 mechanically and electrically links the supply terminal and the supplied terminal and is, for example, a screw, bolt, or other mechanical fastening element.

[0018] The power supply terminal 12 includes in this case one end of a cable 20 and the powered terminal 14 includes a winding connection tip 22.

[0019] The power supply terminal 12, the powered terminal 14 and the connecting element 18 form an electrical connection section 24 which is devoid of electrical insulation and therefore exposed.

[0020] The supply terminal 12 includes an insulated section 26 provided with electrical insulation and the supplied terminal 14 includes an insulated section 28 provided with electrical insulation.

[0021] The short-circuit detection device 10 includes a terminal box 30. The terminal box 30 is provided with a terminal box support 32 and a terminal box cover 34. The supply terminal 12, the supplied terminal 14, and the connecting element 18 are located in the terminal box. The insulated sections 26 and 28 are extended, and the extension passes through the terminal box support 32.

[0022] The short-circuit detection device 10 further includes a detection element 36 for an electric arc emanating from the electrical connection section 24. This detection element 36 includes an electrically conductive element 38 having a detection section 40.

[0023] The electrically conductive element 38 is connected to the electrical mass or to the electrical ground, in this case to the chassis 4.

[0024] The electrically conductive element 38 is, for example, made of copper, aluminum, or steel.

[0025] The detection element 36 includes a detection coating 42 which is electrically insulating and thermally degradable ( Figure 2 The detection coating 42 surrounds the detection section 40, in particular along its entire length and / or the entire length of the detection section. In this case, the detection coating surrounds the electrically conductive element along its entire length within the terminal box, along a section passing through a wall of the terminal box 30, and a portion of its length extending from the terminal box 30. Only a section extending outside the terminal box 30 of the detection element 36 is devoid of detection coating 42.

[0026] The sensing coating 42 is a coating designed to degrade under the heat generated by an electric arc. The sensing coating may comprise or be made of heat-sensitive polymer(s), such as PVC, fluoropolymer, or polypropylene, chemically doped to decrease electrical resistance when the temperature increases. The thermal degradation temperature, i.e., the temperature at which the thermal coating degrades, can range from 80°C to 240°C, and specifically from 100°C to 200°C.

[0027] The electrically conductive element 38 of the detection element may have a circular, elliptical, square, or rectangular cross-section. The electrically conductive element may be in the form of a wire, a bar, or a ribbon.

[0028] In the case of the method of implementation of Figures 1 And 2, the detection element 36 consists of a single branch extending inside the terminal box 30.

[0029] The detection section 40 extends, in particular along its entire length and / or extent, to a detection distance DD of the electrical connection section 24.

[0030] The detection distance DD is chosen such that, when an electric arc occurs at the electrical connection section 24, this electric arc thermally degrades the detection coating 42 and establishes an electrical connection by arc between the connection section and the electrically conductive element 38. This connection to electrical mass or earth is then detected, for example by a short-circuit detection module 50 forming part of the detection device. This detection module 50 is, for example, a module suitable for detecting a current difference between two phases, for example P1 and P2 of the electric motor 6 supply circuit, or for detecting a leakage current between the phase and electrical mass or earth (generally including the vehicle chassis 4) ( Figure 1 ). Depending on the detection of a short circuit by the detection module 50, the detection module can emit a detection signal or cut off the power supply to the electric motor 6. The short-circuit detection module 50 can, for example, include a residual current switch or a residual current circuit breaker.

[0031] The detection distance DD can be determined, for example, as follows: a) the detection distance is less than the range of an electric arc emanating from the electrical connection section 24 and suitable for thermally degrading the detection coating 42; and / or b) the detection distance DD is such that, on the one hand, the breakdown voltage between the detection section 40 and the electrical connection section 24 in the presence of the detection coating is greater than a nominal voltage of the supply terminal, and on the other hand, the breakdown voltage between the detection section and the electrical connection section in the absence of the detection coating is less than a nominal voltage of the supply terminal; and / or c) the detection distance DD is less than a distance between the electrical connection segment 24 and an additional electrical circuit element, which is the electrical circuit element closest to that electrical connection segment.

[0032] For case c), the additional electrical circuit element is for example an additional connection section of another phase of the same electric motor 6 (see below).

[0033] For nominal electrical voltages between 1kV and 5kV, the detection distance is, for example, between 1 mm and 5 mm. Generally speaking, the detection distance can therefore be between 1.0 mm and 5.0 mm.

[0034] In this case, the detection section 40 is located in the terminal box 30.

[0035] As this is visible on the Figure 2 The short-circuit detection device 10 may include an additional power supply terminal 112, which may be located in the terminal box, an additional powered terminal 114, which may also be located in the terminal box, and an additional connecting element 118. The additional connecting element 118 connects the additional power supply terminal and the additional powered terminal and may also be located in the terminal box. These additional elements—the additional power supply terminal 112, the additional powered terminal 114, and the additional connecting element 118—may be identical to the elements 12, 14, and 18 described previously. These additional elements, for example, form part of an additional phase P2 for supplying electricity to the electric motor 6. The electric motor 6 includes an additional stator winding 116 for this purpose.

[0036] The additional power supply terminal 112, the additional powered terminal 114 and the additional connecting element 118 define an additional electrical connection section 124 without electrical insulation.

[0037] Detection distance DD is less than the segment distance DT between the electrical connection section 24 and the additional electrical connection section 124.

[0038] The terminal box 30 includes in this case a separation wall 130 between the electrical connection section and the additional electrical connection section.

[0039] The method of implementation of the Figure 3 differs from the embodiment described above only in the following. Analogous elements bear the same references.

[0040] In the case of the implementation method of the Figure 3 , the detection element 36 forms a two-branch loop.

[0041] The detection device according to the invention makes it possible to detect the appearance of an electric arc using simple and economical means. The detection device is also suitable for retrofitting existing electrical circuits.

[0042] The preceding description contains technical features of the invention. These technical features, although presented in a technical context and possibly in combination with other technical features, can each time be used individually, without the other technical features, insofar as this is technically possible.

Claims

1. Short-circuit detection device, comprising a power supply terminal (12), a powered terminal (14), an element (18) for linking the power supply terminal and the powered terminal, the power supply terminal, the powered terminal and the linking element forming an electrical connection section (24), which is devoid of electrical insulation, the power supply terminal and the powered terminal each comprising an insulated section (26, 28) provided with electrical insulation, the short-circuit detection device comprising an element (36) for detecting electric arcs originating from the electrical connection section, characterised in that the detection element comprises an electrically conductive element (38), having a detection section (40), and a detection coating (42) which is electrically insulating and thermally degradable and which surrounds the detection section, and in that the detection section (40) extends at a detection distance (DD) from the electrical connection section.

2. Short-circuit detection device according to claim 1, wherein the detection distance (DD) is less than a range distance of an electric arc from the electrical connection section (24) and adapted to thermally degrade the detection coating (42), and / or the detection distance (DD) is such that, on the one hand, the breakdown voltage between the detection section (40) and the electrical connection section (24) in the presence of the detection coating (42) is greater than a nominal voltage of the power supply terminal, and, on the other hand, the breakdown voltage between the detection section and the electrical connection section, in the absence of the detection coating, is less than a nominal voltage of the power supply terminal, and / or the detection distance (DD) is shorter than a distance (DT) between the electrical connection section (24) and an additional electric circuit element, which is the electric circuit element the closest to this electrical connection section.

3. Short-circuit detection device according to claim 1 or 2, wherein the detection coating (42) is a coating adapted to be degraded under the effect of heat generated by an electric arc, preferably wherein the detection coating (42) comprises or consists of heat-sensitive polymer(s), such as PVC, fluoropolymer or polypropylene, chemically doped resulting in a decrease in electrical resistance in the case of an increase in temperature.

4. Short-circuit detection device according to any of the preceding claims, wherein the electrically conductive element (38) is connected to the electrical earth or to the electrical ground.

5. Short-circuit detection device according to any one of the preceding claims, wherein the short-circuit detection device comprises a short-circuit detection module (50), which is adapted to detect electrical grounding of the power supply terminal and of the powered terminal via the electrically-conductive element (38).

6. Short-circuit detection device according to any of the preceding claims, wherein the electrically conductive element (38) of the detection element has a circular, elliptical, square or rectangular cross-section and / or wherein the electrically conductive element is in wire, bar or ribbon form.

7. Short-circuit detection device according to any one of the preceding claims, wherein the detection element either consists of a single arm, or forms a two-armed loop.

8. Short-circuit detection device according to one of the preceding claims, wherein the short-circuit detection device comprises a terminal box (30), the power supply terminal (12) is disposed in the terminal box, the powered terminal (14) is disposed in the terminal box, the linking element (18) is disposed in the terminal box, and the detection section (40) is disposed in the terminal box.

9. Short-circuit detection device according to claim 8, wherein the detection device comprises an additional power supply terminal (112) which is disposed in the terminal box, an additional powered terminal (114) which is disposed in the terminal box, an additional linking element (118) connecting the additional power supply terminal and the additional powered terminal and which is disposed in the terminal box (30), the additional power supply terminal, the additional powered terminal and the additional linking element defining an additional electrical connection section (124), devoid of electrical insulation, and wherein the detection distance is less than the distance (DT) between the electrical connection section and the additional electrical connection section, and preferably wherein the terminal box comprises a separating wall (130) between the electrical connection section and the additional electrical connection section.

10. Vehicle (2), particularly a railway vehicle, of the type comprising an electric motor (6) having at least two phases (P1; P2) and a short-circuit detection device (10) connected to the electric motor, characterised in that the short-circuit detection device is a device according to any of the preceding claims.