FR2989512A1 - CONTROL UNIT FOR CUTTING A LINE IN CASE OF OVERCURRENT IN THIS LINE AND CIRCUIT BREAKER AGAINST OVERCURRENT IN A LINE - Google Patents

Abstract

This control assembly comprises an electromagnetic actuator (22, 27) having a winding (22) to be connected in a line to be monitored which is capable of producing a driving magnetic field and having a movable element (27) movable under it. action of this driving magnetic field, from a waiting zone to a trigger zone. An elastic member recalls the moving equipment to the waiting area. An electronic monitoring and control device (5) actuates a switch (7) in the direction of a cut of the line (2) in the case where a detection device (23, 30) has detected the passage of the mobile equipment (27) from the waiting area to the trip zone.

Description

BACKGROUND OF THE INVENTION The invention relates to the field of protection against overcurrents. More specifically, it relates to a control assembly which is of the control unit type of a cut of a line in the event of overcurrent in this line, by transmission of an electrical control signal to a control device. 'a break switch of the line.

The invention also relates to an overcurrent protection circuit breaker in a line, of the type comprising a line breaking switch, a device for operating this switch in response to an electrical control signal, and a control unit. a cut of the line in case of overcurrent in this line, by sending the electrical control signal to the operating device. STATE OF THE ART Electromechanical circuit breakers are well known and constitute a particular type of overcurrent protection circuit breaker. An electromechanical circuit breaker conventionally comprises a coil connected in the line to be protected, and a movable ferromagnetic core which is exposed to the magnetic field produced by the coil when it is energized.

The moving part of a cut-off switch of the line to be protected is mechanically coupled to the mobile core. In the event of a short-circuit, this mobile core is driven by the magnetic field produced by the coil and its movement is transmitted to the moving part of the switch, which is thus open.

An electromechanical circuit breaker is not flexible for use in single use: electromechanical circuit breakers only fulfill their only protection function in the event of a short circuit, without being able to cooperate with other devices or being triggered by a control. exterior. In addition, electromechanical circuit breakers are not equipped with a self test, that is to say they can not conduct tests on themselves to check their condition. There are also electronic circuit breakers, which are more flexible than electromechanical circuit breakers, but have the disadvantage of being less reliable. In these electronic circuit breakers, the current to be monitored is analyzed continuously. The current analysis is used in a test to decide whether or not to cut a line to protect.

In particular, it is known to make electronic circuit breakers digitally performing a so-called 12t protection, which avoids a cut in the case of current spikes sufficiently fugitive not to be sources of destructive heating. In a protection 12t, the overcurrent protection resulting from a current i is triggered when the integral of the square of this current i over a predetermined duration d, that is to say the integral t + d .2 ft. dt, exceeds a certain threshold. Examples of circuit breakers providing 12t protection are proposed in French patent application FR-2,540,303 and US-5,220,478 of the United States of America.

In a 12t protection performed numerically, a continuous measurement of the current i to be monitored is sampled and digitized. Also, one squares the sampled values continuously, then one computes numerically a value of the integral W = ftt + d i2dt. This last value W recalculated permanently, in real time, is constantly compared to a threshold and a cut of the line to protect occurs when this threshold is exceeded. Overcurrent protection is only effective if it is responded to in a very short time after the occurrence of this overcurrent. The squaring of a sample of the current i to be monitored and the numerical integration can be done quickly only by means of electronics that are fairly energy-consuming and cost-intensive, including the cost calculation and acquisition devices for intensity measurements, as well as the cost of power supply. Electronic circuit breakers providing 12t protection are therefore expensive.

SUMMARY OF THE INVENTION The object of the invention is at least to make it possible to propose a circuit breaker which provides the same or comparable protection as a 12t protection and which, without being too expensive, is flexible in use and can be used in one or more other features besides protecting against overcurrent. According to the invention, this object is achieved by means of a control assembly which is of the abovementioned type and which comprises: an electromagnetic actuator whose winding to be connected in the line is able to produce a driving magnetic field and a crew of which mobile is movable under the action of this magnetic driving field, from a waiting zone at least to a trigger zone, an elastic member for returning the moving equipment to the waiting zone, in the direction opposite to the trip zone, a device for detecting a passage of the moving equipment from the waiting zone to the trigger zone, and an electronic device for monitoring the detection and control device at the operating device to actuate the switch in the direction of a cut of the line in the case where the detection device has detected the passage of the mobile crew from the waiting zone to the trigger zone . As combined as specified in the definition above, the electromagnetic actuator and the elastic member together define a trigger threshold which corresponds to a globally constant value of W = rd i2dt. In case of overcurrent, the rate of increase of the intensity i of the current in the monitored line influences the tripping time. However, regardless of this rate of increase, the level determining a break in the line is reached by W = ftt + d i2dt since the mobile unit has moved sufficiently to reach the trigger zone and that this can be detected by the detection device.

It follows from the above that the circuit breaker defined above performs 12t protection. Furthermore, the operating device of the switch is controlled by an electronic device which can perform several different functions, in particular easily communicate with the outside. This electronic device can in particular receive from outside and implement orders to open or close the switch, for example in the context of an installation control applying a load shedding strategy. Thanks to its ability to exchange with the outside, the electronic device therefore allows the circuit breaker is used in a new feature.

The electronic device of the circuit breaker according to the invention does not have to perform a large sum of calculations in a very short time and can be cheap.

The control assembly defined above may incorporate one or more other advantageous characteristics, alone or in combination, in particular from those defined below.

Advantageously, the control assembly comprises a reception input of an external control and is adapted to control the operating device to actuate the switch according to this external command.

Advantageously, the detection device comprises a magnetic field variation detection coil, as well as a magnet driven by the moving element so as to modify the magnetic field inside the detection coil during a period of time. inversion of the position of the moving equipment between the waiting and trigger zones.

Advantageously, the winding of the actuator and the detection coil delimit respectively a first and a second axial passage opening towards one another. Preferably, the moving element is axially slidable in the first passage and drives the magnet towards and away from an axial inlet of the second passage. Advantageously, the control assembly comprises first and second magnetic circuits. Preferably, the first magnetic circuit comprises at least one loop which passes through the winding of the actuator. Preferably, the second magnetic circuit comprises at least one loop which passes through the detection coil. Preferably, the or each loop of the second magnetic circuit is angularly offset from the or each loop of the first magnetic circuit, around said second axial passage, so as to be substantially magnetically decoupled from the first magnetic circuit.

Advantageously, the control assembly comprises a partition wall dividing the space locally into a first region, where the winding of the actuator is located, and a second region, where the detection coil is located. Preferably, this partition wall is made of ferromagnetic material in order to channel the driving magnetic field and a deflection of this field away from said detection coil. Advantageously, the magnet passes the separation wall when the moving equipment passes from the waiting zone to the trigger zone. Advantageously, said partition wall is part of a carcass which is made of ferromagnetic material, which forms part of a first magnetic circuit passing through the winding of the actuator and forms part of a second magnetic circuit passing through. in the detection coil. Advantageously, the control assembly comprises a hollow support shaft which is engaged in the first and second passages and which supports the winding of the actuator and the detection coil. Advantageously, the support shaft encloses the moving element. Advantageously, the carcass comprises two parts which are fixed to one another and which retain axially between them the support shaft.

The invention also relates to a circuit breaker which is of the aforementioned type and whose control assembly is as defined above.

BRIEF DESCRIPTION OF THE DRAWINGS Other advantages and features will emerge more clearly from the following description of a particular embodiment of the invention given by way of non-limiting example and represented in the appended drawings, among which: FIG. 1 is a diagram of the general architecture of a circuit breaker according to the invention and also represents the connection of this circuit breaker in a line to be protected against overcurrent, Figure 2 is a perspective view of a constituent electromechanical subassembly. FIG. 3 is a perspective view of an assembly casing forming part of the subassembly of FIG. 2; FIG. 4 is a perspective view, broken away, which represents the same subassembly. 2 and in which this subassembly is in a first configuration, at rest, FIG. 5 is a diagram of electrical circuits present in the circuit breaker. 1, and FIG. 6 is a cut-away perspective view similar to FIG. 4 and in which the subassembly of FIG. 2 is in a second configuration, namely in a triggered configuration, Following an overcurrent condition. DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION In FIG. 1, the reference numeral 1 designates a circuit breaker which is in accordance with the invention and which is connected in an electrical line 2 to provide protection against electric shock. accidental over-currents. The circuit breaker 1 comprises an electromechanical subassembly 3, whose function is to react to an overcurrent and which is under the observation of an electronic monitoring and control device. Advantageously consisting of a microcontroller 5 as in the example shown, this electronic device controls a device 6 for maneuvering a switch 7 for cutting line 2. The electromechanical subassembly 3 and microcontroller 5 are part of a set control according to the invention.

The microcontroller 5 can communicate with the outside. In the example shown, this microcontroller 5 has indeed an input 8 for receiving an external control, which it is able to apply to the operating device 6 and which can be the order to cut the line 2 or the reverse order to close this line 2. The operating device 6 may have several forms. For example, the assembly that it forms with the switch 7 may be constituted by an electromechanical relay. In the example shown, the operating device 6 comprises an electromechanical actuator known in itself and shown schematically, the coil and the movable magnetic circuit are respectively referenced 10 and 11. Still in Figure 1, the reference 12 designates the terminals of circuit breaker 1 connection in line 2.

The electromechanical subassembly 3 is shown alone in FIG. 2. It comprises a hollow support shaft 20, made of polymer and mounted in an assembly casing 21. With a longitudinal axis X-X ', this hollow shaft 20 supports a winding 22 and a sensing coil 23 axially offset from one another and substantially coaxial, being centered on the axis X-X '. Represented alone in Figure 3, the assembly carcass 21 results from the attachment of two parts 24 and 25 to each other. Each of the pieces 24 and 25 is obtained by U-folding a blank of ferromagnetic material, for example of suitable steel. Each wing of the U defined by the piece 25 is crimped or welded or otherwise assembled on one of two opposite edges of a partition wall 26 that forms one of the wings of the U defined by the piece 24. The wings of the 24 are traversed by the axis X-X ', which passes through the bottom of the U formed by the part 25. The partition wall 26 locally divides the space: on one side of the partition wall 26 is located a first region, that the part 24 partially surrounds and where there is the winding 22. On the other side of the partition wall 26 is a second region that the part 25 partially surrounds and where there is the coil of detection 23. The partition wall 26 provides a magnetic isolation function of the first and second regions relative to each other, channeling any magnetic field generated from one of these first and second regions and by deviating radially towards the rest of the carcass of a 21. The part 24 forms a part of a first magnetic circuit, which is referenced C1 and symbolized by a dashed line in FIG. 3. In the example shown, this first magnetic circuit C1 has only one passing loop. in the winding 22.

The partition wall 26 is common to the first magnetic circuit Ci and to a second magnetic circuit, which further comprises the part 25. This second magnetic circuit is referenced C2 and symbolized by a dashed line in Figure 3. In the example shown it comprises two loops passing through the detection coil 23. The magnetic circuit C2 may also comprise only one loop passing through the detection coil 23. Each loop of the magnetic circuit C2 is angularly offset by 90 ° relative to the loop of the magnetic circuit C1, about the axis X-X ', so as to be substantially magnetically decoupled from this magnetic circuit C1. The winding 22 and the part 24 constitute the static part of an actuator, of which a movable plunger 27 is visible in FIG. 4. Intervening in the detection of a possible overcurrent, this actuator does not have to be powerful and its winding 22 may advantageously comprise only a single turn, as in the example shown, or that a few turns.

Made of a ferromagnetic material such as steel, the plunger core 27 is part of a moving element which is slidably mounted along the axis X-X ', in the axial passage delimited internally by the coil 22. A coil spring The compression member 28 forms a resilient member reminding said movable member towards the detection coil 23, against a stop constituted by an internal shoulder 29 of the support shaft 20. The plunger core 27 has an end which is directed towards the delimited axial passage by the detection coil 23 and carrying a permanent magnet 30.

The support shaft 20 encloses the spring 28, the magnet 30, as well as the plunger 27, of which it guides the axial sliding. In addition to the piece 24, the magnetic circuit C1 comprises the plunger 27 and a fixed core 31 engaged in one end of the support shaft 20. In addition to the partition wall 26 and the part 25, the magnetic circuit C2 comprises a static core 32 in ferromagnetic material. This static core 32 is engaged in one end of the support shaft 20, so as to extend in the axial passage delimited by the detection coil 23. The parts 24 and 25 of the assembly carcass 21 hold together. the support shaft 20, in the direction defined by the axis X-X '. In addition to this, the fixed core 31 and the static core 32 laterally retain the ends of this support shaft 20, each having a pin which is engaged through the corresponding part 24 or 25 and which is crimped or welded or fastened by fitting by force to this piece.

It follows from the foregoing that the assembly carcass 21, the fixed core 31 and the static core 32 maintain assembled the components of the electromechanical subassembly 3, at the same time that they form the major part of two magnetic circuits. In doing so, they simultaneously perform two functions, which is advantageous especially in terms of simplification, lightening, reduced size, ease of industrial assembly and lower cost. In a first step of assembling the electromechanical subassembly 3, the support shaft 20 is provided with the detection coil 23 and with different components that this support shaft 20 is intended to enclose, and among which notably include the core plunger 27 provided with the magnet 30, as well as the spring 28. The assembly thus formed is engaged through the partition wall 26 and then in the winding 22, and it is put in place in the part 24 already provided with the core fixed 31, but not yet of the piece 25. The installation of this piece 25 and its attachment to the piece 24 take place only then. Alternatively, the part 25 can be assembled at one end of the support shaft 20 before the latter is placed in the room 24. From the foregoing, it follows that the assembly of the electromechanical subassembly 3 is an operation that the arrangement of this subset 3 greatly simplifies, which is advantageous. As can be seen in FIG. 1, the winding 22 is intended to be connected in the line 2 to be monitored. For this purpose, this winding 22 and the breaking switch 7 are connected in series between the two connection terminals 12 of the circuit breaker 1 in the line 2. Visibly in Figure 1 as in Figure 5, the terminals of the detection coil 23 are connected to an input of the microcontroller 5, which monitors the voltage between them. The microcontroller 5 is furthermore adapted to perform itself, at regular intervals, an automated test for checking the electrical continuity of the detection coil 23, for which a test circuit shown in FIG. 5 is provided. this test circuit, the detection coil 23 and a bias resistor 40 of this coil 23 are connected in series between two points to which different electrical potentials Vo and Vref are applied.

The detection coil 23 has a much lower electrical resistance than that of the bias resistor 40. Therefore, when there is a break in the electrical continuity of the detection coil 23, the potential at a point between this coil of detection 23 and the bias resistor 40 changes significantly, passing substantially from Vo to Vref in the example shown, which monitors the automated test.

Also shown in Figure 5, a supply circuit of the coil 10 of the operating device 6 comprises two electronic cutoff switches, which controls the microcontroller 5 and each of which may be in the form of a transistor 41 or 42. The transistor 41 and the coil 10 are connected in series in a branch connected to a DC power supply. In a branch connected in parallel with the coil 10, a freewheeling diode 43 and a zener diode 44 are connected in series, so as to be in opposite directions. The transistor 42 and the zener diode 44 are connected in parallel.

In the absence of overcurrent, the electromechanical subassembly 3 is as shown in FIG. 4, in which the compressed spring 28 holds the immobilized plunger 26 in abutment against the shoulder 29 in a waiting zone. The magnet 30 is then within the magnetic circuit C2 passing through the detection coil 23. The magnetic field it produces therefore reigns inside this detection coil 23. In the event of overcurrent in the line 2, the current flowing in the winding 22 produces a magnetic field such that it manages to drive the plunger 27 against the action of the spring 28, to its position in Figure 6, where the plunger 27 has reaches a protection trip zone. More precisely, as it passes from its position in FIG. 4 to that of FIG. 6, the plunger core 27 carries with it the magnet 30 away from the magnetic circuit C2, by causing it to pass through the partition wall 26. and bringing it into the first aforesaid region, i.e., in a region where the magnetic field produced by this magnet 30 is not or hardly present within the sense coil 23. The The passage of the plunger core 27 between its position in FIG. 4 and that of FIG. 6 thus results in a variation of the magnetic flux generated by the magnet 30 through the detection coil 23. The decrease of the magnetic flux through the coil detection 23 leads to that, at its terminals, this coil 23 produces a voltage that detects the microcontroller 5 and informed about the occurrence of the overcurrent. The voltage detected by the microcontroller 5 depends on the rate of variation of the magnetic flux and therefore on the speed of the moving element, which is itself a function of the rate of increase di / dt of the intensity i of the current in line 2. The detection coil 23 is dimensioned such that the voltage induced in this coil 23 is sufficiently high, for example of the order of a volt, to be detected by the microcontroller 5 without having to be amplified beforehand, which allows the economy of an expensive amplification.

The plunger core 27 is driven axially from the waiting zone to the trigger zone by compression of the spring 28 and the storage of a potential energy by this spring 28. In these conditions, its driving up to the trigger zone implies the satisfaction of a condition, which is globally the triggering condition of a 12t protection. More specifically, for the plunger core 27 to reach the trip zone, the integral ftt + d i2dt must reach a minimum value that is substantially constant regardless of the change in intensity i of the current in the line 2 on the fixed duration of integration d. Being substantially constant, this minimum value is comparable to a threshold and is considered to constitute such a threshold in the definition and use of the protection conferred by the circuit breaker 1.

To set the tripping threshold of the protection conferred by the circuit breaker 1, it is possible to vary the stiffness of the spring 28. As long as the two transistors 41 and 42 are closed, that is to say, they are passing, the coil 10 is under voltage and the operating device 6 holds the switch 7 in the closed position. In response to detection of an overcurrent, the microcontroller 5 opens the switch 7. When it thus results in the detection of an overcurrent in the line 2, the opening of the switch 7 must be performed very quickly after this detection. If a fast opening of the switch 7 is desired as in the case of detection of an overcurrent, the microcontroller 5 simultaneously opens the transistors 41 and 42. In this way, a strong counter-voltage is established across the coil 10, which leads to a rapid demagnetization of the latter. It follows a rapid displacement of the mobile magnetic circuit 11 under the action of a spring, not shown, of the return of the switch 7 to its open position.

A quick opening of the switch 7 is also brutal for the hardware. It may not be useful to quickly open this switch 7, for example when the command to cut the line 2 comes from the outside through the input 8 and does not result in detection of an overcurrent. The microcontroller 5 can control a slower opening of the switch 7. To do this, it opens the transistor 42 and leaves the transistor 41 closed, so that the zener diode is bypassed and the coil 10 can be discharged slowly because the low-voltage imposed by the freewheeling diode 43. Advantageously, the transistor 41 can also serve to regulate the supply current of the coil 10 by chopping the supply voltage, which can then be wide range, it that is, likely to fluctuate over a wide range. The circuit breaker 1 has the advantage of being designed to provide protection against low overcurrent, for example against overcurrent of less than ten amperes. The circuit breaker 1 has other advantages of having high reliability, low cost and space saving. The invention is not limited to the embodiment described above. In particular, the detection of a passage of the plunger core 27 from the waiting zone to the trip zone can be performed by a device other than that described above. For example, this detection can be performed by means of a microswitch, or a Hall effect sensor, or even any other electronic or mechanical sensor capable of detecting a position. However, the detection device comprising the magnet 30 and the detection coil 23 as shown in FIGS. 2, 4 and 6 has the advantages of being reliable and of being able to be tested automatically so that its operating state is verified, as well as this has been explained above.

In addition, the electronic device controlling the operating device 6 is a control logic that can have various forms, in particular not be in the form of a microcontroller 5. For example, a customer integrated circuit, also designated by the acronym CIC and still called "specific application integrated circuit" (named ASIC or "Application-Specific Integrated Circuit" in English), can be used in place of the microcontroller 5. A programmable gate array (designated by the terms "field programmable gate array" And by the acronym FPGA in English) may also be suitable for the same purposes. According to yet another possibility, the microcontroller 5 can be replaced or supplemented by comparators associated with logic.

Claims (12)

REVENDICATIONS1. Control unit for a cut of a line (2) in the event of overcurrent in this line (2), by transmission of an electrical control signal to a device (6) for operating a switch ( 7) for cutting the line (2), characterized in that it comprises: an electromagnetic actuator (22, 24, 27, 31), a winding (22) to be connected in the line is able to produce a magnetic field a moving element (27) is movable under the action of this driving magnetic field, from a waiting zone at least up to a trigger zone, an elastic member (28) for the moving element (27) towards the waiting zone, in the direction opposite to the trigger zone, a device (23, 25, 30, 32) for detecting a passage of the moving element (27) of the the waiting zone at the trip zone, and an electronic device (5) for monitoring the detection device (23, 25, 30, 32) and controlling the operating device (6) to actuate the switch (7) in the direction of a cut of the line (2) in the case where the detection device (23, 25, 30, 32) has detected the passage of the mobile assembly (27) from the waiting area to the trip zone. 2. Control assembly according to claim 1, characterized in that the control assembly comprises an inlet (8) for receiving an external control and is adapted to control the operating device (6) to actuate the switch (7) according to this external command. 3. Control assembly according to any one of the preceding claims, characterized in that the detection device (23, 25, 30, 32) comprises a coil (23) for detecting a magnetic field variation, and a magnet (30) driven by the moving element (27) so as to modify the magnetic field inside the detection coil (23) during a reversal of the position of the moving element (27) between the waiting and trigger zones. 4. Control assembly according to claim 3, characterized in that the winding (22) of the actuator and the detection coil (23) respectively define a first and a second axial passage opening towards one another, the moving element (27) being axially slidable in the first passage and driving the magnet (30) towards and away from an axial inlet of the second passage. 5. Control assembly according to claim 4, characterized in that it comprises first and second magnetic circuits (C1, C2), the first magnetic circuit (C1) comprising at least one loop which passes through the winding (22). of the actuator, the second magnetic circuit (C2) comprising at least one loop which passes through the detection coil (23), the or each loop of the second magnetic circuit (C2) being angularly offset from the or each loop of the first circuit magnetic (C1), around said second axial passage, so as to be substantially magnetically decoupled from the first magnetic circuit (C1). 6. Control assembly according to any one of claims 4 and 5, characterized in that it comprises a partition wall (26) locally dividing the space into a first region, where is the winding (22) of the actuator, and a second region, where the detection coil (23) is located, this partition wall (26) being made of ferromagnetic material in order to channel the driving magnetic field and a deflection of this field to the distance from said detection coil (23). 7. Control assembly according to claim 6, characterized in that the magnet (30) crosses the partition wall (26) when the moving element (27) passes from the waiting zone to the trigger zone. 8. Control assembly according to any one of claims 6 and 7, characterized in that said partition wall (26) is part of a carcass (21) which is made of ferromagnetic material, which forms part of a first magnetic circuit (C1) passing through the winding (22) of the actuator and which forms a part of a second magnetic circuit (C2) passing through the detection coil (23). 9. Control assembly according to any one of claims 4 to 8, characterized in that it comprises a hollow support shaft (20) which is engaged in the first and second passages and which supports the winding (22) of the actuator and the sensing coil (23). 10. Control assembly according to claim 9, characterized in that the support shaft (20) encloses the moving element (27). 11. Control assembly according to claim 8 and any one of claims 9 and 10, characterized in that the carcass (21) comprises two parts (24, 25) which are fixed to one another and which hold axially between them the support shaft (20). 12. Overcurrent protection circuit breaker in a line (2), comprising: - a switch (7) for breaking the line (2), a device (6) for operating this switch (7) in response to a signal electrical control unit, and a control unit of a cut of the line (2) in case of overcurrent in this line (2), by transmission of the electrical control signal to the operating device (6), characterized in that that the control assembly is according to any one of the preceding claims.