Electrical protection device with high direct voltage by means of a fuse

Abstract

Electrical protection device (D, D', D") comprising: - A fuse (2) comprising: o a first end (20a) and o a second end (20b) opposite the first end (20a), o a fusible conductor (21) extending from the first end (20a) to the second end (20b), - at least one block of fins (3) comprising: o a first fin (30a), a last fin (30n) and intermediate fins (30) spaced from each other between the first fin (30a) and the last fin (30n), - an arc guide (4) comprising: o a first conductor (4a) extending from the first end (20a) of the fuse (2) towards the first fin (30a) and o a second conductor (4b) extending from the second end (20b) of the fuse (2) towards the last fin (30n) - at least one magnet (6) oriented relative to the fuse (2) to attract an electric arc formed between the first and second conductors (4a,4b) at the fuse (2) in a molten state,towards the fin block (3), - a second fin block mounted opposite the first fin block to guide the electric arc into the second fin block in the event of current flowing in the other direction.,

Description

DOMAINE TECHNIQUE DE L'INVENTION

[0001] The technical field of the invention is that of high-voltage direct current electrical protection devices.

[0002] The present invention relates to an electrical protection device comprising a fuse. ARRIERE-PLAN TECHNOLOGIQUE DE L'INVENTION

[0003] Electrical protection devices are usually circuit breakers or fuses. There are voltage lines protected by a circuit breaker and a fuse to increase a level of safety through dissimilar redundancy. In aeronautics, this redundancy is very important.

[0004] The use of industrial high voltage direct current (HVDC) fuses to protect on-board aeronautical equipment has the disadvantage of longitudinal bulk and significant mass.

[0005] For example, fuses generally have an oversized breaking capacity to be able to be used and in fact very different compared to circuits whose electrical line impedances are shorter with lower value inductances.

[0006] The fuse must be able to contain the overpressure induced by the electric arc when the fuse blows. When the two contact ends of the fuse blow, one or more electric arcs appear, accompanied by high thermal stress and difficulty in extinguishing the electrical connection. It is therefore necessary that these arcs extinguish quickly.

[0007] Indeed, when clarifying a fault by a conventional HVDC fuse, the arc voltage in the fuse when it melts must be able to increase until it reaches and exceeds the value of the network voltage in order to cancel the current. Conventionally this is possible by using different sections in the fuse throughout the latter. figure 1 represents a schematic diagram of a fuse 1 according to the prior art comprising two connectors 10a, 10b, a ceramic body 11 extending between the two connectors 10a, 10b. The fuse 1 further comprises a fusible conductor 12 housed in the body 11, formed by conductive blades 120 connected to each other by a reduced section 121. The fuse 1 further comprises silica 13 in the body 11 surrounding the fusible conductor 12. These conductive blades 120 cause, when the fusible conductor 12 melts, a sectioning of the arc by the reduced sections 121 making it possible to increase the arc voltage and thus to extinguish it when it is above the network voltage at the terminals of the two connectors 10a, 10b.However, the higher the network voltage, the greater the number of sections, increasing the number of blades, a significant volume of silica in the body 11 to absorb the energy of the electric arc and therefore an increasingly long fuse length which can reach, for example, 10cm long, leading to an increase in the mass of the fuse.

[0008] The main disadvantage of these technical solutions, apart from their significant longitudinal dimension, is that the structure must be structurally sufficiently mechanically resistant to the internal pressure during the melting of the fusible conductor. One of the failure modes of the fuse can occur when the electric arc is no longer confined in the enclosure of the fuse during the melting of the fusible conductor 12, a gas release occurs generating a pressure which can damage the body 11 of the fuse. The deterioration of the body 11 can be a crack or even an explosion of the fusible body. During this explosion, incandescent particles can be projected and cause a fire. In addition, during the deterioration of the body 11 by the gas release, metallic particles and vapors, coming from the melting fusible conductor 12, can participate in projecting an electric arc outside the damaged body 11 and cause a fire to start.

[0009] There is therefore a need for a high-voltage continuous electrical protection device of the fuse type but less bulky longitudinally and more robust and of reduced mass. RESUME DE L'INVENTION

[0010] The invention provides a solution to the problems mentioned above, by making it possible to split the electric arc formed between the two connectors of a fuse whose conductor has melted, by means of separating fins, called in the application the Deion principle. This principle makes it possible to reduce the longitudinal size while splitting the electric arc to extinguish it without a fuse body to absorb the energy of the arc, thus making it mechanically more robust and less heavy.

[0011] A first aspect of the invention thus relates to an electrical protection device comprising: a fuse comprising: a first end, a second end opposite the first end, a fusible conductor extending from the first end to the second end, at least one fin block having: a first fin, a last fin and intermediate fins spaced apart from each other between the first fin and the last fin, an arc guide comprising: a first conductor extending from the first end of the fuse to the first fin and a second conductor extending from the second end of the fuse to the last fin at least one magnet oriented relative to the fuse to attract an electric arc formed between the first and second conductors at the fuse in a molten state, to the fin block, a second fin block mounted opposite the first fin block to guide the electric arc into the second fin block in the event of current flowing in the other direction.

[0012] Thus, the invention makes it possible to control the cut-off by splitting the electric arc when the fuse melts using the Deion principle. This makes it possible to avoid a crack or explosion projecting particles outside the protection device by splitting the electric arc. Thus the device makes it possible to have a non-oversized fusible conductor, more compact longitudinally and above all a very simple device and not subject to the explosion problem of the fuse bodies of the prior art. The block of fins makes it possible to split the electric arc without retaining its energy unlike the case of the fuse body described previously. The number of fins and the inter-fin spacing are chosen according to the network voltage, for example around thirty fins for a voltage of 900 volts. All of the inter-fin electric arcs are called the split electric arc in the description.The greater the number of fins, the greater the extinguishing voltage. The sum of the inter-fin arc voltages will be equal to or greater than the network voltage. In addition, the second block and the permanent magnet generate a magnetic field perpendicular to the direction of the current flowing in the fuse to force the electric arc to move towards the corresponding fin block regardless of the mounting direction of the device and therefore the direction of current flow in the fuse.

[0013] In addition to the characteristics which have just been mentioned in the preceding paragraph, the protection device according to one aspect of the invention may have one or more additional characteristics among those mentioned in the following paragraphs, considered individually or according to all technically possible combinations:

[0014] According to one embodiment, the magnet may comprise samarium cobalt. The composition of the permanent magnet is thus chosen so as to be resistant to the temperature of the device, particularly in the event of an electric arc.

[0015] According to one embodiment, the device comprises a gaseous space delimited on the one hand between the fusible conductor and the fin block, and on the other hand between the first and second conductors allowing an electric arc to move from the fusible conductor to the fin block.

[0016] According to one embodiment, the device comprises at least one magnet oriented relative to the fuse to attract an electric arc formed between the first and second conductors at the fuse in a molten state, towards the fin block.

[0017] According to an example of this embodiment, the device comprises a permanent magnet magnetic circuit for generating a magnetic field perpendicular to the direction of the current flowing in the fuse.

[0018] According to one embodiment, the first conductor is distant from the first fin forming a space. This makes it possible to use this space as a gap to help extinguish the split electric arc.

[0019] According to one embodiment, the second conductor is distant from the last fin forming a space. This makes it possible to use this space as a gap to help extinguish the split electric arc.

[0020] According to one embodiment, the intermediate fins comprise a notch together forming a groove. The notches make it possible to predetermine the area where the split electric arc will be guided and contained to be extinguished.

[0021] According to one embodiment, the fusible conductor has a reduced section compared to the section of the first end and the second end which are each conductive.

[0022] According to one embodiment, the first end and the second end of the fuse have the same material as the fusible conductor and are each welded respectively to the first and second conductors.

[0023] According to one embodiment, the first end and the second end are each a connector mounted against the first and second arc guide conductors, respectively.

[0024] A second aspect of the invention relates to a method for cutting a voltage line by an electrical protection device according to the first aspect of the invention, with or without the different characteristics described previously in the different examples and embodiments, the method comprising a step of melting the fusible conductor, a step of guiding an electric arc formed following the melting of the fuse, from the ends of the fuse towards the block of fins and a step of splitting the electric arc in the block of fins until it is extinguished.

[0025] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BREVE DESCRIPTION DES FIGURES

[0026] The figures are presented for information purposes only and in no way limit the invention. [ Fig.1 ] is a schematic diagram of a fuse according to the prior art. [ Fig.2 ] is a schematic diagram of an electrical protection device according to the invention. [ Fig.3 ] is the schematic diagram of the electrical protection device of the figure 2 representing the path of an electric arc following a blown fuse. Fig.4a ] is a schematic diagram of an electrical protection device according to a first example of a second embodiment representing the path of an electric arc following a blown fuse. [ Fig.4b ] is a schematic diagram of an electrical protection device according to a second example of the second embodiment representing the path of an electric arc following a blown fuse. [ Fig.5 ] is an electrical diagram comprising the electrical protection device according to the first embodiment of the invention. DESCRIPTION DETAILLEE

[0027] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0028] The invention relates to an electrical protection device D represented according to a block diagram in figure 2 . The electrical protection device D comprises a fuse 2 comprising a first end 20a, a second end 20b longitudinally opposite the first end 20a and a fusible conductor 21 extending longitudinally from the first end 20a to the second end 20b. In this example, the first end 20a is a first connector and the second end 20b is a second connector of the fuse 2. The fuse 2 may be made of a single material, in this case the first and second ends 20a, 20b form a single piece with the fusible conductor 21, for example by cutting from a sheet metal, or extrusion.

[0029] Fuse 2 has no body enclosing fusible conductor 21, in other words fusible conductor 21 is in the open air.

[0030] The first and second ends 20a, 20b are each shown according to a block diagram on the figure 2 , but are each electrically and physically connected to a different electrical terminal (not shown) of the electrical protection device D intended to be connected each to a different conductor.

[0031] The fusible conductor 21 has a section smaller than a first and second conductor intended to be connected respectively to the first end 20a and to the second end 20b. The fusible conductor 21 can for example be made of a material having a faster melting than copper with isosection or can be made of copper having a section smaller than the section of the first end 20a and the section of the second end 20b as well as the conductor (conductive trace or core of an electric wire) connected to the device D. Thus, a current I flows in one direction of electric current for example, from the first end 20a to the second end 20b through the fusible conductor 21, or in the opposite direction. According to another example the first end 20a and the second end 20b of the fusible conductor 21 have the same section as the section

[0032] The electrical protection device D further comprises at least one fin block 3 shown according to a block diagram, comprising a first fin 30a, a last fin 30n and intermediate fins 30 of which only one is referenced. The intermediate fins 30 are spaced from each other between the first fin 30a and the last fin 30n. Each fin 30a, 30, 30n of the fin block 3 is directly electrically insulated from the neighboring fin (for the first and last fin) or from the two neighboring fins (for the intermediate fins) by an inter-fin space 32. In this example, the inter-fin spaces 32 between two neighboring fins 30a, 30, 30n are identical. Each fin 30a, 30, 30n is a plate of which one edge is shown and comprises a first planar surface and a second planar surface opposite the first planar surface.Each intermediate fin 30, and the last fin 30n of the fin block 3, has its first planar surface facing the second planar surface of the nearest neighboring fin of the first fin 30a. Each intermediate fin 30 and the first fin 30a of the fin block 3, has its second planar surface facing the first planar surface of the nearest neighboring fin of the last fin 30n.

[0033] The electrical protection device D further comprises an arc guide 4 comprising a first conductor 4a extending from the first end 20a of the fuse 2 towards the first fin 30a, in this case spaced apart by a distance less than or identical to the space 32 between two intermediate fins 30.

[0034] The arc guide 4 further comprises a second conductor 4b extending from the second end 20b of the fuse 2 towards the last fin 30n, in this case distant by a distance less than or identical to the space 32 between two intermediate fins 30.

[0035] The first conductor 4a and second conductor 4b comprise for example a first and second plug for receiving respectively each the first and second end 20a, 20b which can each be a connector adapted to be plugged into respectively the first and second plug. For example, the first and second plug are of the elastically deformable Ω type and the first and second ends 20a, 20b are each of cylindrical shape fitted into the corresponding plug. According to another example the first and second ends 20a and 20b are male or female plugs fitted into respectively female or male plugs of the device.The device may further comprise, for example, a terminal block comprising at least a first contact and a second contact which are each electrically connected respectively to the first and second conductors, and are each adapted to be attached to a conductor which may be an electrical wire comprising a conductive core and an insulator or even an electrical trace, for example made of copper.

[0036] The fin block 3 comprises a number N of fins 30 depending on the network voltage applied to the device corresponding to the voltage between the two ends 20a and 20b when the fusible conductor 21 has melted, as shown in figure 3 in which the fusible conductor 21 is not shown.

[0037] The first conductor 4a and the second conductor 4b each comprise arms extending away from each other in a flared manner, to allow an electric arc to be displaced when the fusible conductor 21 has melted.

[0038] On this figure 3 , an electric arc 5 is shown schematically at different positions between the first conductor 4a and the second conductor 4b which then splits into a plurality of electric arcs, represented by ovals, between on the one hand the first conductor 4a and the first fin 30a, on the other hand between the different fins 30a, 30, 30n, and finally between the last fin 30n and the second conductor 4b.

[0039] The separation of the electric arc into a plurality of electric arcs will extinguish all of the electric arcs and thus ensure the protection of the devices connected in series with the electrical protection device D. In the following, the plurality of electric arcs is called the split electric arc.

[0040] According to another embodiment, a first example of which is shown in figure 4a , the electrical protection device D' is identical to that of the first embodiment except in that it comprises at least a first magnet 6 and in that the first and second conductors 4a, 4b are in physical and electrical contact with the first and last fin 30a, 30n respectively. The permanent magnet, called first magnet 6, may comprise samarium cobalt. The composition of the permanent magnet 6 is thus chosen so as to be resistant to the temperature of the device, particularly in the event of an electric arc.

[0041] In this example, the first end 20a is connected to a main conductor Ca of a circuit connected to the positive polarity of the network and the second end 20b is connected to a main conductor Cb connected to the negative polarity of the network.

[0042] The first magnet 6 has a north pole opposite the first and second conductors 4a, 4b next to the first and second ends 20a, 20b. Thus the first magnet 6 generates a magnetic field of constant direction from the first magnet 6 to the first and second conductors 4a, 4b next to the first and second ends 20a, 20b.

[0043] The magnetic field forces the electric arc 5 to move towards the fin block 3 according to Laplace's law.

[0044] So, d F → = I . d l → ∧ B →

[0045] With F , the force applied to the electric arc 5, I the current flowing through the electric arc 5, l the length element of the electric arc 5 crossed by the current I And B the magnetic field to which it is subjected.

[0046] There figure 4b illustrates another example of this embodiment, in which the device D" comprises a second magnet 6' located opposite the first magnet 6 such that the electric arc during the melting of the fuse (represented on the figure 4b ) and the arc guide 4 are located between the first magnet 6 and the second magnet 6'. The second magnet 6' has a South pole facing the first and second conductors 4a, 4b next to the first and second ends 20a, 20b. The permanent magnets 6, 6' may have the same composition so as to be resistant to the temperature of the device, particularly in the event of an electric arc. For example, the permanent magnets 6, 6' comprise samarium cobalt. In this configuration, the electric arc 5 propagates from the first and second ends 20a, 20b and moves by a magnetic force generated by the magnetic field towards the fin block 3. The electric arc 5 is guided by the first conductor 4a of the arc guide 4 towards the first fin 3a and by the second conductor 4b towards the last fin 30n.

[0047] In the various examples of the various embodiments, the insulating housing (not shown) of the electrical protection device D may comprise a housing accommodating each fin 30a, 30, 30n and comprise notches or ribs each supporting a fin 30a, 30, 30n according to a gap corresponding to the space 32 with the neighboring fin 30a, 30, 30n.

[0048] Each flat fin surface 30a, 30, 30n has a surface value at least twice that of the end surfaces 20a, 20b of the fuse 2. This makes it possible to improve its heat dissipation and therefore to reduce the heating of the electrical protection device D.

[0049] Each fin 30a, 30, 30n may also have a notch forming together a groove. The notches make it possible to predetermine the exact location where the split electric arc will be guided and contained to be extinguished.

[0050] Other solutions are also possible, for example a second fin block can be mounted opposite, allowing the electric arc to be guided into the second fin block in the event of the device being mounted upside down with the magnet 6.

[0051] There figure 5represents an electrical diagram comprising in series, a high voltage DC source 7, a contactor 8, a load 9 and the protection device D, of the first embodiment but could be the protection device D' of the second embodiment. In this example, the contactor 8 is connected in series between the positive terminal of the voltage source and a terminal of the device D connected directly to the first end 20a of the fuse 2. The load 9 is connected in series directly electrically between a terminal of the device D connected directly to the second end 20b of the fuse 2 and the negative terminal of the HVDC voltage source. In the event of an overload (load fault, for example a short circuit), the fusible conductor 21 melts, and if an electric arc appears, it is guided by the arc guide 4 towards the fin block 3 which extinguishes it.

Claims

1. Electrical protection device (D, D', D") comprising: - A fuse (2) comprising: ∘ a first end (20a) and ∘ a second end (20b) opposite the first end (20a), ∘ a fusible conductor (21) extending from the first end (20a) to the second end (20b), - at least one block of fins (3) comprising: ∘ a first fin (30a), a last fin (30n) and intermediate fins (30) spaced from each other between the first fin (30a) and the last fin (30n), - an arc guide (4) comprising: ∘ a first conductor (4a) extending from the first end (20a) of the fuse (2) towards the first fin (30a) and ∘ a second conductor (4b) extending from the second end (20b) of the fuse (2) towards the last fin (30n) - at least one magnet (6) oriented relative to the fuse (2) to attract an electric arc formed between the first and second conductors (4a,4b) at the fuse (2) in a molten state,towards the fin block (3), - a second fin block mounted opposite the first fin block to guide the electric arc into the second fin block in the event of current flowing in the other direction., 2. Electrical protection device (D', D") according to the preceding claim, comprising a second magnet (6') located opposite the first magnet (6) generating with the first magnet (6) a magnetic field in the same direction, the arc guide (4) being located between the first magnet (6) and the second magnet (6).

3. Electrical protection device (D, D") according to one of the preceding claims, in which the first conductor (4a) is distant from the first fin (30a) forming a space.

4. Electrical protection device (D, D', D") according to one of the preceding claims, in which the intermediate fins (30) comprise a notch together forming a groove.

5. Electrical protection device (D, D', D") according to one of the preceding claims, in which the fusible conductor (21) has a constant section from the first end (20a) to the second end (20b).

6. Electrical protection device (D, D', D") according to one of the preceding claims, in which the first and second ends (20a, 20b) of the fuse (2) have the same material as the fusible conductor (21) and are each welded respectively to the first and second conductor (4a, 4b).

7. Electrical protection device (D, D', D") according to one of claims 1 to 6, in which the first end (20a) and the second end (20b) are each a connector mounted against the first and second conductors (4a, 4b) respectively.

8. Method for cutting a voltage line by an electrical protection device (D, D', D") according to any one of the preceding claims, the method comprising: - a step of melting the fusible conductor (21), - a step of guiding an electric arc formed following the melting of the fusible conductor (21), the ends (20a, 20b) of the fuse (2) towards the block of fins (3) and - a step of splitting the electric arc in the block of fins (3) until it is extinguished.

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