A control device for an automatic reset apparatus

Abstract

 A control device for an automatic reset apparatus has a plurality of electromechanical units, each electrically connected to a phase of an electrical system. The electromagnetic units are kinematically connected to an actuation mechanism of a microswitch that drives an electronic control device of a reset apparatus associated with a protection device of the system. Each of the electromechanical units operates independently of the others and uses an electromagnetic field that is generated by the fault current of the phase connected thereto in order to act on the mechanism that acts on the microswitch, which is functionally connected to the electronic control device of the reset apparatus in order to inhibit its operation.

Description

[0001] The present invention relates to a control device for an automatic reset apparatus.

[0002] As is known, domestic and industrial electrical systems are provided with protection devices adapted to prevent a fault current from causing danger to the users and to loads connected to the electrical line.

[0003] Upon detecting the presence of the fault current, the protection device releases the line, thus interrupting the power supply to the load or loads arranged downstream.

[0004] After intervention, and once the correct operating conditions for the system have been restored, the protection device must be reset.

[0005] Apparatuses have been developed that allow to automatically reset a protection device after its release, after checking the correct operation of the system.

[0006] Within the scope of the development of these automatic reset apparatuses with fault control in the system before reclosure of the associated protection device, the need arises to use circuit solutions that are reliable, simple and cheap in order to identify ground isolation faults (ground leakage currents) and overcurrent faults (overload or short-circuit currents).

[0007] EP-1569314 discloses a method for detecting ground isolation faults.

[0008] Currently commercially available automatic resetting devices, capable of detecting faults due to overcurrents, verify the presence of a short circuit in the downstream system by measuring the current that circulates therein.

[0009] This measurement is performed only following the automatic opening due to a fault of the associated protection device.

[0010] The current is generated by the automatic reset device by means of an electronic control circuit, supplying power to the downstream circuit by means of a single-phase isolating transformer with an extremely low safety voltage.

[0011] The value of the circulating current depends of course on the value of the impedance of the downstream circuit.

[0012] At this point the manufacturer establishes a so-called "reset current threshold", above which the automatic reset device recloses the associated protection device and below which automatic reclosure of the associated protection device is inhibited.

[0013] Such automatic reset devices in practice are used only with two-pole switches.

[0014] In three-phase or three-phase + neutral (L1, L2, L3, N) distribution systems, the above system in fact encounters considerable difficulties in application in automatic reset devices to be associated with three- and four-pole protection devices (3P, 3P+N, 4P), due to the bulky dimensions and the high costs that it would assume.

[0015] It becomes in fact necessary to use a three-phase transformer with three separate measurement circuits, one for each phase, or as an alternative a system that has a single-phase transformer with alternating switching of relays to check all possible fault combinations (L1-L2, L1-L3, L2-L3, L1-N, L2-N, L3-N).

[0016] The aim of the present invention is to provide a control device which, applied to an automatic reset apparatus, overcomes the drawbacks of the cited prior art.

[0017] Within the scope of this aim, an object of the invention is to provide a device which, associated with a protection device of a system, is capable of detecting faults due to overcurrents without incurring the problems and drawbacks of systems of the prior art.

[0018] Another object of the invention is to provide a device that is reliable, cheap and easy to manufacture.

[0019] Another object is to provide a device that allows to considerably reduce the detection times of an overcurrent fault, in practice being activated simultaneously with the opening of the protection device.

[0020] Another object of the invention is to provide a device that allows to perform a fine adjustment of the fault current threshold that causes the actuation of the device, discriminating any overload current values from short-circuit current values.

[0021] Another object of the invention is to provide a device that can be associated with any type of protection device and allows to detect any combination of faults in the circuit.

[0022] Another object of the present invention is to provide a device which, by virtue of its particular constructive features, is capable of giving the greatest assurances of reliability and safety in use.

[0023] This aim and these and other objects, which will become better apparent hereinafter, are achieved by a control device for an automatic reset apparatus, characterized in that it comprises a plurality of electromechanical units, each of said units being electrically connected to a phase of an electrical system, said units being kinematically connected to an actuation mechanism of a microswitch that is adapted to drive an electronic control device of a reset apparatus associated with a protection device of the system; each of said unit operating independently of the other units and being adapted to use an electromagnetic field that is generated by the fault current in the phase connected thereto in order to act on said mechanism that acts on said microswitch, which is functionally connected to said electronic control device of said reset apparatus.

[0024] Further characteristics and advantages will become better apparent from the description of preferred but not exclusive embodiments of the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a perspective view of the control device according to the present invention;

Figure 2 is a rear perspective view of the control device;

Figure 3 is an exploded perspective view of the control device;

Figure 4 is a sectional front view of the control device with the electromechanical assemblies in the inactive condition;

Figure 5 is a view that is similar to the preceding one but illustrating the device in the condition of activation of one phase;

Figure 6 is a perspective view of an electromechanical assembly and of the corresponding terminal.

[0025] With reference to the cited figures, the control device according to the invention, generally designated by the reference numeral 1, comprises a casing constituted by a base 2 that is closed by a cover 3 with the interposition of an intermediate base 7.

[0026] The base 2, the cover 3 and the intermediate base 7 form a plurality of seats 4 for respective electromechanical units 5, that are associated with respective terminals 6.

[0027] A microswitch 8 is actuated by an actuation lever 9, which has a plurality of engagement seats 10 for respective transmission linkages 11.

[0028] Each transmission linkage 11 is associated with the respective electromechanical unit 5 by a crossbar 12, which connects the moving core 13 of the electromechanical unit to the linkage.

[0029] Each electromechanical unit 5 has a jacket 14, which is constituted by a folded metal plate and contains the movable core 13, a fixed core 15, a coil 16 and a spool 17.

[0030] The axial movement of the moving core 13 is contrasted by a contrast spring 18. The preloading of the contrast spring 18 is adjustable by means of an adjustment screw 19 in order to adjust the magnetic threshold, as described hereinafter.

[0031] Each adjustment screw 19 can be accessed from the outside by means of a respective opening 21 provided in the base 2 and equipped with a plug 22.

[0032] The electromechanical assembly is connected to the respective terminal 6 by means of a double L-shaped terminal body 20.

[0033] The microswitch 8 is connected to a card 23 that is wired for connection to the outside.

[0034] According to the present invention, each electromechanical unit utilizes the electromechanical field generated by the fault current. Each unit comprises two main components: a first component, constituted by the two electromagnetic members, the fixed core 15 and the moving core 13, that are affected by the electromagnetic field generated by the fault current, and an actuation mechanism, which includes the lever 9, the linkages 11 and the crossbars 12.

[0035] The force generated by the electromagnetic field, by interaction between the fixed electromagnetic member and the movable electromagnetic member, causes the movement of the movable electromagnetic member 13, which acts on the lever system that acts directly on the microswitch 8, which is functionally connected to the electronic control device of the reset apparatus, not visible in the figures.

[0036] In this manner, the electronic control device detects the signal that originates from the microswitch 8 and immediately inhibits the automatic reclosure of the protection device associated with the reset apparatus.

[0037] Such a device, in addition to being reliable, cheap and easy to manufacture, allows to considerably reduce the overcurrent fault detection times, bacause it becomes active simultaneously with the opening of the protection device.

[0038] The magnetic adjustment screw 19 allows to perform a fine adjustment of the fault current threshold that causes the activation of the device, discriminating any overload current values from short-circuit current values.

[0039] The electromechanical fault detection units 5 are also mutually independent and do not interfere, and therefore do not hinder each other, on the internal actuation mechanism.

[0040] In this manner, all the fault combinations described above can be detected by the device, which can be associated with any type of protection device (1P, 1P+N, 2P, 3P, 3P+N, 4P).

[0041] In practice it has been found that the invention achieves the intended aim and objects.

[0042] This application claims the priority of Italian Patent Application No. MI2008A001092, filed on June 17, 2008, the subject matter of which is incorporated herein by reference.

Claims

1. A control device for an automatic reset apparatus, characterized in that it comprises a plurality of electromechanical units, each of said units being electrically connected to a phase of an electrical system, said units being kinematically connected to an actuation mechanism of a microswitch that is adapted to drive an electronic control device of a reset apparatus associated with a protection device of the system; each of said unit operating independently of the other units and being adapted to use an electromagnetic field that is generated by the fault current in the phase connected thereto in order to act on said mechanism that acts on said microswitch, which is functionally connected to said electronic control device of said reset apparatus.

2. The control device according to claim 1, characterized in that it comprises a means for the fine adjustment of the fault current threshold that causes the actuation of said device.

3. The control device according to claim 1 or 2, characterized in that each of said units comprises a component that is constituted by two electromagnetic members, a fixed member and a movable member, that are affected by the electromagnetic field generated by said fault current, and a mechanical component that is connected to said actuation mechanism.

4. The control device according to one or more of the preceding claims, characterized in that each of said units comprises a jacket, constituted by a folded metal plate, and contains a moving core, a fixed core, a coil and a spool.

5. The control device according to one or more of the preceding claims, characterized in that said adjustment means comprises a contrast spring, which acts in contrast with said moving core, the preloading of said spring being adjustable by an adjustment screw in order to adjust the magnetic threshold.

6. The control device according to one or more of the preceding claims, characterized in that each of said units is connected to a respective terminal by means of a double L-shaped terminal body.

7. The control device according to one or more of the preceding claims, characterized in that said actuation mechanism comprises an actuation lever adapted to actuate said microswitch, said actuation lever comprising a plurality of engagement seats for respective transmission linkages; each of said transmission linkages is associated with a respective unit of said units by means of a crossbar that connects said movable core of the electromechanical assembly to said linkage.

8. The control device according to one or more of the preceding claims, characterized in that it comprises a casing constituted by a base that is closed by a cover.

9. The control device according to claim 8, characterized in that said base comprises a plurality of seats for said units, which are associated with said respective terminals by means of an intermediate base member.

Drawing