COMPACT CONTROL MODULE FOR AUTOMATIC RESET DEVICES

Abstract

 A control module for automatic reset devices, including a containment body crossed by a conductor connected to an electrical circuit and a micro-switch connected to a reset device; the module being characterized in that it includes a fixed core and a movable member which are subjected to an electromagnetic field generated by a current flowing in the conductor; the movable member being movable from an active position of the micro-switch to an inactive position of the micro-switch; the movable member being movable in contrast with a spring; a force generated by the electromagnetic field causing the movement of the movable member.

Description

[0001] The present invention relates to a compact control module for automatic reset devices.

[0002] As is known, an automatic reset device allows to automatically reset a residual current operated circuit breaker following a release thereof, after checking the correct operation of the system.

[0003] Residual current operated circuit breakers are normally provided in domestic and industrial systems to prevent a fault current from causing danger for users and loads connected to the electrical line.

[0004] Essentially, the residual current operated circuit breaker, upon detecting the presence of the fault current, releases the line, thus interrupting the supply of power to the load or loads arranged downstream.

[0005] After the release of the residual current operated circuit breaker, and once the correct operating conditions for the system have been restored, the residual current operated circuit breaker must be reset.

[0006] The operating conditions often reset by themselves because the fault is of the transient type caused by overvoltages.

[0007] This reset normally occurs manually by acting on an adapted reset lever.

[0008] However, if the user resets the breaker after an opening or release of the residual current operated circuit breaker, he cannot be sure that the fault has been removed. Therefore, when the user resets the breaker, a subsequent immediate release of the residual current operated circuit breaker may occur because the problem has not been solved correctly.

[0009] In designing automatic reset devices that perform fault checking in the system, prior to the re-closure of the associated protection device, the need arises to use circuit structures which are reliable, simple and of low cost while capable of identifying earth insulation faults (earth leakage currents) and overcurrent faults (overload or short-circuit currents).

[0010] A method for detecting earth insulation faults is disclosed for example in EP1569314, while an example of a system for detecting overcurrent faults is disclosed in EP2136383.

[0011] With reference to overcurrent fault detection, currently commercially available automatic reset devices, that may be associated exclusively with two pole breakers, check for the presence of a short-circuit in the downstream system by measuring the current that circulates therein. This measurement is performed only after an automatic opening due to a fault of the associated protection device. 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 insulation transformer with an extremely low safe voltage.

[0012] The value of the circulating current depends on the value of the impedance of the downstream circuit. The manufacturer sets at this point a reset current threshold, above which the automatic reset device recloses the associated protection device and below which the automatic re-closure of the associated protection device is inhibited.

[0013] In three-phase distribution systems with neutral (L1, L2, L3, N), such a solution, however, is considerably difficult to apply in automatic reset devices to be associated with three-pole and four-pole breakers (3P, 3P+N, 4P), due to the bulky dimensions and the high costs that it would entail.

[0014] It is in fact necessary to use a three-phase transformer with three distinct measurement circuits, one for each phase, or, as an alternative, a solution which provides a single-phase transformer with alternating relay switching to check all the possible fault combinations (L1-L2, L1-L3, L2-L3, L1-N, L2-N, L3-N).

[0015] The aim of the present invention is to provide a control module for reset devices that overcomes the drawbacks of the cited prior art.

[0016] Within the scope of this aim, an object of the invention is to provide a control module that is extremely compact.

[0017] Another object of the invention is to provide a module that can be combined with any type of protection device.

[0018] A further object of the present invention is to provide a control module that allows to considerably reduce the detection times of the overcurrent fault.

[0019] Another object of the invention is to provide a control module that is capable of performing an independent fault detection of each pole so that all the fault combinations, for example 1 P, 1 P+N, 2P, 3P, 3P+N, 4P, can be detected by the module.

[0020] Another object is to provide a control module that is reliable, of low cost and easy to manufacture.

[0021] This aim and these and other objects which will become better apparent hereinafter are achieved by a compact control module for automatic reset devices as claimed in the appended claims.

[0022] 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 a control module according to the present invention;

Figure 2 is a view, similar to the preceding one, showing the external cable with multiple turns;

Figure 3 is a cutout front view of the control module shown in the inactive condition;

Figure 4 is a cutout front view of the control module shown in the active condition.

[0023] With reference to the cited figures, the control module according to the invention, generally designated by the reference numeral 1, has a containment body 2 provided with a passage 3 in which an electric cable 4 is inserted.

[0024] Inside the containment body 2, a micro-switch 5 is provided with a control lever 6 which is actuated by a movable armature 7.

[0025] A fixed core or yoke 8, at least partially arranged around the cable 4, attracts the movable armature 7 in contrast with the action of a return spring 9.

[0026] The control module 1 according to the present invention is combined with a reset device, which is not shown in the figures.

[0027] The electric cable 4 is inserted in the passage 3, like a sort of TA, and the consequent magnetic field generates an attraction force between the movable armature 7 and the core 8.

[0028] When the attraction force exceeds the value of the spring 9 and the activation force of the micro-switch 5, the micro-switch 5 opens the contact which, monitored by the electronic board of the associated reset device, inhibits the optional re-closure operation of the circuit breaker.

[0029] The activation threshold of the device is adjusted to an initial value by means of the return spring 9.

[0030] The installation technician may adjust the activation threshold of the device by providing different numbers of turns 41 of the external cable 4.

[0031] The number of turns is selected as a function of the nominal current and of the magnetic intervention curve of the breaker with which the module 1 is associated.

[0032] The control module according to the present invention is an electromechanical device that utilizes the electromagnetic field generated by the fault current and is constituted essentially by the two magnetic members, the fixed core 8 and the movable armature 7, which are crossed by the magnetic field generated by the fault current, and the actuation mechanism. The force generated by the electromagnetic field, due to the interaction between the fixed member and the movable member, causes the movement of the movable member, i.e., the armature 7, which acts directly on the micro-switch 5, which can be interfaced with the electronic control device.

[0033] In this manner, the electronic control device detects the signal that arrives from the micro-switch 5 and immediately inhibits the automatic re-closure of the associated protection device.

[0034] In practice it has been found that the invention achieves the intended aim and objects, providing a control module which, with respect to control systems of the background art, has no electrical wiring with box terminals and, inside the device, no solenoid generating the electromagnetic attraction force for the movement of the metallic components for the activation of the micro-switch but utilizes directly the electromagnetic field generated by the current that flows through the electric cable 4 inserted in the passage 3.

[0035] The control module according to the present invention is reliable, low in cost and easy to manufacture.

[0036] Also, the present control module allows to reduce considerably the overcurrent fault detection times, since it is activated simultaneously with the opening of the protection device.

[0037] The present control module is arranged on each phase and allows the independent detection of the fault of one pole with respect to the other.

[0038] In this manner all the fault combinations (1 P, 1P+N, 2P, 3P, 3P+N, 4P) can be detectable by the module.

[0039] The control module according to the present invention is associable with any type of protection device.

Claims

1. A control module for automatic reset devices, comprising a containment body having a conductor and a micro-switch, said conductor being connected to an electrical circuit, said micro-switch being connected to a reset device; said module further comprising a fixed core and a movable element which are subjected to an electromagnetic field generated by a current flowing in said conductor; said movable member being movable from an active position of said micro-switch to an inactive position of said micro-switch; said movable member being movable in contrast with a spring; a force generated by said electromagnetic field causing the movement of said movable member; said module being characterized in that said containment body comprises at least one passage through which said conductor, constituted by an electric cable, is inserted.

2. The module according to claim 1, characterized in that said micro-switch is arranged inside said containment body and comprises an actuation lever operated by said movable member.

3. The module according to claim 2, characterized in that said movable member is constituted by a movable armature.

4. The module according to claim 3, characterized in that said fixed member is constituted by a fixed core which at least partially surrounds said electric cable.

5. The module according to claim 4, characterized in that said electric cable inserted in said passage generates a magnetic field when it is crossed by a current; said magnetic field generating a magnetic attraction force between said movable armature and said fixed core; when said attraction force exceeds the force of said spring and the activation force of said lever of said micro-switch, said micro-switch opens a contact which, monitored by a reset device, inhibits the possible operation of a protection device associated with said reset device.

6. The module according to claim 5, characterized in that the activation threshold of said micro-switch is adjusted to an initial value by means of said spring.

7. A method of adjusting the activation threshold of said micro-switch, according to claim 1, characterized in that said activation threshold is adjusted by providing a different number of turns of said cable outside said containment body depending on the nominal current and on the magnetic tripping curve of the protection device.

Drawing