Switching apparatus for electrical systems and control method thereof

Abstract

A switching apparatus for electrical applications comprising: - one or more electric poles; - for each electric pole, one or more fixed contacts and one or more movable contacts, wherein said movable contacts are reversibly movable between an uncoupled position, at which said movable contacts are decoupled from said fixed contacts, and a coupled position, at which said movable contacts are coupled with said fixed contacts; - an actuation assembly including an electromagnetic actuator and one or more opening springs operatively coupled to said movable contacts, wherein said electromagnetic actuator is adapted to provide actuation forces directed in such a way to move said movable contacts towards said coupled position, wherein said opening springs are adapted to provide actuation forces directed in such a way to move said movable contacts towards said uncoupled position, - a driving unit electrically connected to said electromagnetic actuator and adapted to feed said electromagnetic actuator with an excitation current to operate said electromagnetic actuator; - a control unit operatively coupled to said driving unit to control said driving unit, wherein said control unit is configured to determine whether said movable contacts are subject to undesired movements away from said coupled position, when said switching apparatus is in a closed state, based on the behaviour of an excitation current feeding said electromagnetic actuator, wherein said control unit is configured to command said driving unit to change the feeding of said electromagnetic actuator, if it is determined that said movable contacts are subject to undesired movements, when the switching apparatus is in closed state.

Description

[0001] The present invention concerns a switching apparatus for electrical systems, such as a circuit breaker, a contactor, a disconnector, or the like. More specifically, the present invention concerns a switching apparatus of the electromagnetic type, which is particularly adapted for installation in medium voltage electrical systems, especially in the railway sector.

[0002] In a further aspect, the present invention relates to a control method for controlling such a switching apparatus.

[0003] Switching apparatuses of the electromagnetic type are widely used in electrical systems, particularly in electric grids or switchgears operating at medium voltage levels.

[0004] As is known, these switching apparatuses are equipped with an electromagnetic actuator and one or more opening springs to actuate the movable contacts of the electric poles.

[0005] Typically, the electromagnetic actuator is designed to actuate the movable contacts during a closing manoeuvre of the switching apparatus and to maintain the movable contacts coupled to the corresponding fixed contacts when the switching apparatus is a closed state subsequently a closing manoeuvre. The opening springs are instead adapted to actuate the movable contacts during an opening manoeuvre of the switching apparatus.

[0006] Traditional electromagnetic switching apparatuses have some aspects to improve, particularly in relation to the behaviour in certain operating conditions, namely when they are in a closed state and the movable contacts of the electric poles are subject to undesired movements away from the corresponding fixed contacts, to which they are coupled.

[0007] These accidental movements of the movable contacts, which are normally rather unusual, are typically due to mechanical phenomena of exogenous nature, for example to vibrations of the mechanical parts operationally connected to the mobile contacts (as it frequently occurs in railway installations).

[0008] As a matter of fact, switching apparatuses of the state of the art are not designed to manage these specific situations effectively and in a reliable manner.

[0009] In a traditional switching apparatus, when they are subject to undesired movements away from the coupled position, the movable contacts of the electric poles reach an unstable position, in which they are not coupled to the corresponding fixed contacts anymore and are not travelling towards an uncoupled position.

[0010] The switching apparatus thus falls in a sort of undetermined state, which is different from a closed state and from an open state. This circumstance may lead to undesired and uncontrolled opening manoeuvres of the switching apparatus or to the raise of sudden and repeated arcing phenomena between the coupled contacts of the electric poles.

[0011] The main aim of the present invention is to provide a switching apparatus of the electromagnetic type, which allows overcoming or mitigating the drawbacks of the known art.

[0012] Within this aim, a purpose of the present invention is to provide switching apparatus of the electromagnetic type, which can manage effectively possible events, in which the movable contacts of the electric poles are subject to undesired movements, when said electromagnetic actuator is in a closed state.

[0013] It is a further object of the present invention to provide a switching apparatus of the electromagnetic type having high levels of reliability for the intended electrical applications. Still another object of the present invention is to provide a switching apparatus of the electromagnetic type, which can be easily manufactured at industrial level, at competitive costs with respect to the solutions of the state of the art.

[0014] In order to fulfill these aim and objects, the present invention provides a switching apparatus for electrical applications, according to the following claim 1 and the related dependent claims. In a general definition, the switching apparatus of the invention comprises: one or more electric poles; for each electric pole, one or more fixed contacts and one or more movable contacts. The movable contacts are reversibly movable between an uncoupled position, at which said movable contacts are decoupled from said fixed contacts, and a coupled position, at which said movable contacts are coupled with said fixed contacts; an actuation assembly including an electromagnetic actuator and one or more opening springs operatively coupled to the movable contacts of the electric poles.

[0015] The above-mentioned electromagnetic actuator is adapted to provide actuation forces directed in such a way to move the movable contacts of the electric poles towards the aforesaid coupled position while the above-mentioned opening springs are adapted to provide actuation forces directed in such a way to move the movable contacts of the electric poles towards aforesaid uncoupled position.

[0016] The switching apparatus further comprises a driving unit electrically connected to the aforesaid electromagnetic actuator and adapted to feed said electromagnetic actuator with an excitation current to operate said electromagnetic actuator.

[0017] The switching apparatus further comprises a control unit operatively coupled to the aforesaid driving unit to control said driving unit.

[0018] Advantageously, the control unit of the switching apparatus is configured to control the driving unit in such a way to make the switching apparatus operate as a monostable switch.

[0019] The control unit is configured to command the driving unit to feed the electromagnetic actuator with a launch current to move the movable contacts of the electric poles from the aforesaid uncoupled position to the aforesaid coupled position, during a closing manoeuvre of the switching apparatus.

[0020] The control unit is configured to command the driving unit to feed the electromagnetic actuator with a hold current to maintain the movable contacts of the electric poles in the aforesaid coupled position (in contrast with the actuation forces provided by the opening springs), when the switching apparatus is in a closed state.

[0021] Advantageously, the above-mentioned launch current and hold current are excitation currents having different intensity. In particular, the above-mentioned launch current is higher than the above-mentioned hold current.

[0022] The control unit is configured to command the driving unit to stop feeding the electromagnetic actuator during an opening manoeuvre of the switching apparatus. In this way, the movable contacts of the electric poles can be moved by the opening springs from the aforesaid coupled position to the aforesaid uncoupled position.

[0023] According to the invention, the control unit of the switching apparatus is configured to determine whether the movable contacts of the electric poles are subject to undesired movements away from the aforesaid coupled position when said switching apparatus is in a closed state, based on the behaviour of a hold current provided to the electromagnetic actuator by the driving unit to maintain said movable contacts in the aforesaid coupled position. According to the invention, the control unit is configured to command the driving unit to change the feeding of the electromagnetic actuator, if it is determined that the movable contacts of the electric poles are subject to undesired movements, when the switching apparatus is in closed state.

[0024] According to an aspect of the invention, the control unit is configured to command said driving unit to carry out one of the following alternative operations: a) stop feeding the electromagnetic actuator with said hold current (I H ) in such a way to allow the opening springs to move the movable contacts of the electric poles to the aforesaid uncoupled position; or b) feed the electromagnetic actuator with a launch current, which is higher than said hold current, to move the movable contacts of said electric poles back to the aforesaid coupled position and feed again the electromagnetic actuator with said hold current to maintain the movable contacts of the electric poles in said coupled position (B), once said movable contacts have moved back to said coupled position; if it is determined that the movable contacts of the electric poles are subject to undesired movements away from the aforesaid coupled position, when the switching apparatus is in closed state.

[0025] According to an aspect of the invention, the control unit is configured to determine that the movable contacts of the electric poles are subject to undesired movements away from the aforesaid coupled position, if said hold current or a derivative over time of said hold current exceeds a predefined threshold value.

[0026] According to an aspect of the invention, the control unit is configured to acquire detection data indicative of the behaviour of an excitation current (i.e. a launch current or a hold current) provided to the electromagnetic actuator by the driving unit.

[0027] Conveniently, the switching apparatus comprises sensing means operatively coupled to the electromagnetic actuator and configured to provide said detection data.

[0028] According to an aspect of the invention, the control unit is configured to count the number of events over a predefined time window, in which the movable contacts of the electric poles are subject to undesired movements away from the aforesaid coupled position, when the switching apparatus is in closed state.

[0029] According to an aspect of the invention, the control unit is configured to command the driving unit to feed the electromagnetic actuator with a hold current having a higher intensity when the switching apparatus is in closed state, if the counted number of events exceeds a predefined count value.

[0030] Preferably, the switching apparatus of the invention is a medium voltage switching apparatus. Preferably, the switching apparatus of the invention is adapted to be installed in railway electrical systems.

[0031] In a further aspect, the present invention provides a control method for controlling a switching apparatus for electrical applications, according to the following claim 8 and the related dependent claims.

[0032] Further characteristics and advantages of the present invention will become more apparent from the detailed description of preferred embodiments illustrated only by way of non-limitative example in the accompanying drawings, in which: Figures 1-2 are block diagrams that schematically show the switching apparatus of the invention; and Figures 3-5 are block diagrams that schematically show the structure and operation of an actuation assembly in the switching apparatus of the invention, according a possible embodiments; and Figure 6 is a block diagram that schematically show an embodiment of a control method for controlling a switching apparatus, according to the present invention.

[0033] Referring to the cited figures, the present invention is related to switching apparatus 1 for electrical systems, such as electric grids or switchgears.

[0034] Preferably, the switching apparatus 1 is a circuit breaker. In principle, however, it may be a switching apparatus of different type, such as a contactor, a disconnector, or the like.

[0035] The switching apparatus 1 is particularly adapted for installation in medium voltage electrical systems, especially in the railway sector. In principle, however, it may be employed in electrical systems of different type, such as in low voltage electrical systems or in electrical systems dedicated to other industrial sectors.

[0036] For the purpose of the present application, the term low voltage (LV) relates to operating voltages lower than 2 kV AC and 2.5 kV DC while the term "medium voltage" (MV) relates to higher operating voltages up to some tens of kV, e.g. up to 72 kV AC and 100 kV DC.

[0037] The switching apparatus 1 comprises one or more electric poles, each of which includes one or more movable contacts 11 and one or more fixed contacts 10.

[0038] When the switching apparatus is installed, the electric contacts 10, 11 of each electric pole are electrically connected to corresponding conductors (e.g. a phase conductors or neutral conductors) of an electrical system (not shown).

[0039] Figures 1, 2 schematically show the switching apparatus 1 according to the invention.

[0040] The movable contacts 11 are reversibly movable between an uncoupled position A, at which they are decoupled from the corresponding fixed contacts 10, and a coupled position B, at which they are coupled to said fixed contacts.

[0041] When the movable contacts 11 are in the uncoupled position A, the switching apparatus is in an open state (figure 1). In this situation, electric currents cannot flow through the electric poles. The switching apparatus is in a closed state (figure 2), when the movable contacts 11 are in the coupled position B. In this situation, electric currents can flow through the electric poles.

[0042] The switching apparatus 1 is configured to carry our switching operations in order to electrically connect or disconnect different circuit sections of an electrical system, e.g., for protection purposes or maneuvering purposes.

[0043] A switching operation may be a closing manoeuvre, during which the movable contacts of the electric poles are moved from the uncoupled position A to the coupled position B, or an opening manoeuvre, during which the movable contacts of the electric poles are moved from the coupled position B to the uncoupled position A.

[0044] The switching apparatus 1 comprises an actuation assembly 3 to move the movable contacts of the electric poles between the aforesaid coupled and uncoupled positions.

[0045] The actuation assembly 3 includes an electromagnetic actuator 4 and one or more opening springs 5 operatively coupled to the movable contacts 11.

[0046] According to the invention, these components of the actuation assembly 3 are arranged to actuate the movable contacts 11 in such a way that the switching apparatus behaves as monostable switch.

[0047] The electromagnetic actuator 4 provides actuation forces directed in such a way to move the movable contacts 11 from the uncoupled position A and to the coupled position B. In practice, the electromagnetic actuator 4 provides actuation forces (of the magnetic type) directed in such a way to carry out a closing manoeuvre of the switching apparatus or to maintain the switching apparatus in a closed state.

[0048] The opening springs 5 provide actuation forces directed in such a way to move the movable contacts 11 from the coupled position B to the uncoupled position A. In practice, the opening springs 5 provide actuation forces (of the mechanical type) directed in such a way to carry out an opening manoeuvre of the switching apparatus.

[0049] Figures 3, 4 schematically show the actuation assembly 3 according to a possible embodiment of the invention. As mentioned above, the actuation assembly 3 comprises an electromagnetic actuator 4 and one or more opening springs 5.

[0050] The electromagnetic actuator 4 includes a magnetic yoke having a fixed yoke member 41 and a movable yoke member 43 mechanically coupled to the movable contacts 11 through a suitable kinematic chain (not shown).

[0051] The movable yoke member 43 is reversibly movable between a first position C, at which it is coupled to the fixed yoke member 41, and a second position D, at which it is decoupled from the fixed yoke member 41.

[0052] The first position C of the movable yoke member 43 corresponds to the uncoupled position A of the movable contacts 11 coupled thereto (figure 3) while the second position of the movable yoke member corresponds to the coupled position B of the movable contacts 11 (figure 4). The electromagnetic actuator 4 further includes an excitation arrangement 42 comprising at least an excitation winding wound around the fixed yoke member 41.

[0053] The excitation arrangement 42 is fed with an excitation current I L , I H to move the movable yoke member 43 from the first position C to the second position D (closing manoeuvre of the switching apparatus) or to maintain the movable yoke member in the second position D (closed state of the switching apparatus).

[0054] The excitation current I L , I H circulates in the excitation winding 42 and generates a magnetic flux flowing along a magnetic circuit formed by the magnetic core 41 and the movable plunger 43. The excitation current I L , I H is directed in such a way that the movable yoke member 43 is actuated by a magnetic force directed to move the movable yoke member 43 towards the coupled position B as explained above.

[0055] The opening springs 5 are operatively coupled to the movable yoke member 42 to move this latter from the second position D to the first position C.

[0056] The opening springs 5 store elastic energy when the movable yoke member 42 moves from the first position C to the second position D (closing manoeuvre of the switching apparatus).

[0057] When the movable yoke member 43 is free to move away from the second position D (i.e. when the fixed yoke member 41 and the movable yoke member 43 stop magnetically interacting upon the interruption of the excitation current feeding the excitation arrangement 42), the opening springs 5 release the stored elastic energy and move the movable yoke member 42 from the second position D to the first position C (opening manoeuvre of the switching apparatus). Preferably, the opening springs 5 are structurally integrated with the electromagnetic actuator 4. As shown in figures 3, 4, they can be mechanically coupled between the movable yoke member 43 and a fixed support (not shown).

[0058] In general terms, the actuation assembly 3 may be arranged to solutions (even of known type), which may be different from those shown in figures 3, 4. Therefore, it will be described in the following in relation to the sole aspects of interest of the invention, for the sake of brevity. The switching apparatus 1 further comprises a driving unit 6 electrically connected to the electromagnetic actuator 4 and adapted to feed the electromagnetic actuator with an excitation current I L , I H upon receiving suitable control signals CS from a control unit of the switching apparatus.

[0059] Preferably, the driving unit 6 comprises power supply means 61 to harvest the electric power necessary to operate the electromagnetic actuator 4.

[0060] The power supply means 61 may comprise a capacitor bank to store electric energy for operating the electromagnetic actuator 4 and a power supply circuit electrically connected to a power source (for example the electric line on which the switching apparatus is installed) and capable of continuously charging the aforesaid capacitor bank.

[0061] Preferably, the driving unit 6 comprises a driving circuit 62 electrically connected to the electromagnetic actuator 4, namely to the excitation arrangement 42, and to the power supply means 61.

[0062] The driving circuit 62 is adapted to provide the excitation currents I E , I H to operate the electromagnetic actuator upon receiving suitable control signals CS from an electronic device, for example a control unit of the switching apparatus.

[0063] The driving circuit 62 may include one or more suitable switching circuits and other electronic circuits controllable by a suitable control unit.

[0064] Preferably, the switching apparatus 1 comprises sensing means 8 operatively coupled to the electromagnetic actuator 4 and adapted to provide detection data D indicative of the behaviour of an excitation current I L , I H provided to the electromagnetic actuator by the driving unit 6. Preferably, the sensing means 8 includes one or more current sensors (e.g., current transformers, Hall sensors, shunt circuits, and the like) operatively coupled to the excitation winding 42 of the electromagnetic actuator 4 and suitable interface circuits adapted to process the detection signals provided by these in order to provide the above-mentioned detection data D.

[0065] In general terms, the driving unit 6 and the sensing means 8 may be arranged to solutions different from those explained above (even of known type). Therefore, they will be described in the following in relation to the sole aspects of interest of the invention, for the sake of brevity. The switching apparatus 1 comprises a control unit 7 for controlling the operations of the switching apparatus.

[0066] Preferably, the control unit 7 comprises suitable digital processing devices (e.g. one or more microprocessors) adapted to execute software instructions to generate control / data signals to manage the operating life of the switching apparatus 1. In principle, however, the control unit 7 may include electronic circuits of the analogic type suitably configured to carry out the requested functionalities.

[0067] The control unit 7 is operatively coupled to the driving unit 6 and is configured to control the latter by providing suitable control signals CS, for example to the driving circuit 62. Conveniently, the control unit 7 is operatively coupled also to the sensing means 8 to receive the above-mentioned detection data D from the latter.

[0068] The control unit 7 is conveniently configured to control the operation of the driving unit 6 in such a way to make the switching apparatus operate as a monostable switch.

[0069] Figures 5 shows the excitation current provided to the electromagnetic actuator 4 by the driving unit 6 during closing-opening cycle of the switching apparatus.

[0070] The switching apparatus 1 is supposed to be initially in an open state. In this situation, the control unit 7 commands the driving unit 6 to provide no excitation currents to the electromagnetic actuator 4. The movable yoke portion 43 of the electromagnetic actuator 4 is in the first position C and the movable contacts 11 of the electric poles can stably maintain the uncoupled position A. The opening springs 5 are in a released condition or, preferably, in a precharged condition, so that they can exert actuation forces on the movable contacts 11, which are directed to maintain the latter in the uncoupled position A.

[0071] During a closing manoeuvre of the switching apparatus, the control unit 7 commands the driving unit 6 to feed the electromagnetic actuator 4 with a launch current I L to move the movable contacts 11 from the uncoupled position A to the coupled position B.

[0072] By virtue of the magnetic flux generated by the circulation of the launch current I L along the excitation arrangement 42, the movable yoke portion 43 moves from the first position C to the second position D against the mechanical forces exerted by the opening springs 5 that can thus store elastic energy.

[0073] When the switching apparatus is in a closed state, the control unit 7 commands the driving unit 6 to feed the electromagnetic actuator 4 with a hold current I H to maintain the movable contacts 11 in the coupled position B. The coupled position B of the movable contacts 11 is not a stable position. The movable yoke portion 43 of the electromagnetic actuator 4 is, in fact, maintained in the second position D by the magnetic forces generated by the magnetic flux induced by the circulation of the hold current I H along the excitation arrangement 42. However, the movable yoke portion 43 maintains this position against the mechanical forces exerted by the opening springs 5.

[0074] As the movable yoke portion 43 has to be simply maintained in a static position, the hold current I H , which is provided to the electromagnetic actuator 4 when the switching apparatus is a closed state, is generally (very) lower than the launch current I L , which is provided to the electromagnetic actuator 4 during a closing manoeuvre of the switching apparatus. As an example, in a medium voltage switching apparatus, the launch current I L may be about 9A while the hold current I H may be about 600 mA.

[0075] During an opening manoeuvre of the switching apparatus, the control unit 7 commands the driving unit 6 to stop feeding the electromagnetic actuator 4.

[0076] As there are no magnetic actuation forces generated by the electromagnetic actuator 4, the opening springs 5 are free to move the movable yoke portion 43 from the second position D to the first position C and the movable contacts 11 from the coupled position B to the uncoupled position A, which can be stably maintained.

[0077] Preferably, the control unit 7 comprises a regulator block 71 configured to control the driving unit 6 based on the detection data D provided by the sensor means 8.

[0078] The regulator block 71 may include, for example, a PID regulator.

[0079] Preferably, the above-mentioned switching circuits of the driving unit 6 and the sensor means 8 implement a control loop configured to carry out a PWM regulation of the excitation current provided to the electromagnetic actuator. The electromagnetic actuator can thus be fed as described above during the operation of the switching apparatus.

[0080] The regulator block 71 may be digitally implemented. In this case, a microcontroller of the control unit 7 can execute suitable software instructions for carrying out the functionalities requested to the regulator block. In principle, however, the regulator block 71 may be implemented analogically. In this case, the control unit 7 may include suitable electronic circuits suitably configured to carry out the functionalities of the regulator block.

[0081] An important feature of the present invention consists in that the control unit 7 is configured to manage the behaviour of the switching apparatus, when this latter is in a closed state and the movable contacts 11 of the electric poles are subject to undesired movements away from the above-mentioned coupled position B.

[0082] The control unit 7 can advantageously determine whether the movable contacts 11 of the electric poles are subject to undesired movements based on the behaviour of the hold current I H provided to the electromagnetic actuator 4 by the driving unit 6, when the switching apparatus is in closed state.

[0083] As mentioned above, the level of the hold current I H provided to the electromagnetic actuator 4 is set by a closed control loop formed by the regulator block 71, the driving circuit 62 and the sensing means 8 in such a way to maintain the movable contacts 11 in the coupled position B. The occurrence of undesired movements of the movable contacts 11 when the switching actuator is in closed state, generates a perturbation on the hold current I H , which naturally tends to increase in order to move back the movable contacts 11 in the coupled position B. Therefore, it is possible to understand whether the movable contacts 11 are subject to undesired movements away from the coupled position B by observing the behavior of the hold current I H , in particular by checking whether the hold current I H raises over a predefined threshold or shows a sharp raise.

[0084] Preferably, the control unit 7 determines that the movable contacts 11 are subject to undesired movements, if the hold current I H or its derivative over time exceeds a predefined threshold value.

[0085] Preferably, the control unit 7 checks the behaviour of the hold current I H by processing the detection data D received from the sensing means 8. The control unit 7 can calculate the absolute value of the hold current I H or its derivative over time based on the received detection data D and compare the calculated current value with a predefine threshold value.

[0086] If it is determined that the movable contacts 11 are not subject to undesired movements, the control unit 7 does not take any further initiative and continues to observe the behaviour of the hold current I H while the switching apparatus is in a closed state.

[0087] Instead, if it is determined that the movable contacts 11 are subject to undesired movements, the control unit 7 intervenes and commands the driving unit 6 to change the feeding of electromagnetic actuator 4.

[0088] This solution provides relevant advantages.

[0089] As explained above, when they are subject to undesired movements away from the coupled position B, the movable contacts 11 reach an unstable position, which may lead to the above-mentioned inconveniences. The intervention of control unit 7 allows clearing this uncontrolled and dangerous operating condition of the switching apparatus, which increases remarkably the reliability levels of the switching apparatus.

[0090] Preferably, if it is determined that the movable contacts 11 of the electric poles are subject to undesired movements away from the coupled position B, the control unit 7 commands the driving unit 6 to carry out one of two alternative operations described in the following. According to a possible alternative, the control unit 7 commands the driving unit 6 to stop feeding the electromagnetic actuator 4 with the hold current I H in such a way to allow the opening springs 5 to move the movable contacts 11 to the uncoupled position B.

[0091] In practice, according to this option, the control unit 7 commands to carry out an opening manoeuvre of the switching apparatus starting from the above-mentioned transient position of the movable contacts 11.

[0092] According to another possible alternative, the control unit 7 commands the driving unit 6 to feed the electromagnetic actuator 4 with a launch current I L (which is higher than the hold current I H ) to move the movable contacts 11 back to the coupled position and to feed again the electromagnetic actuator 4 with the hold current I H to maintain the movable contacts 11 in the coupled position B, once the movable contacts have moved back to this position.

[0093] In practice, according to this option, the control unit 7 commands to carry out a closing manoeuvre starting from the transient position of the movable contacts 11. Once, the closing manoeuvre is completed, the control unit 7 commands the driving unit 6 to feed the electromagnetic actuator 4 in such a way to maintain the closed state of the switching apparatus.

[0094] According to some embodiments of the invention, when installed on the field, the control unit 7 is configured to command the driving unit 6 to carry out always only one of the above-described alternative operations.

[0095] According to other embodiments of the invention, however, the control unit 7 can dynamically select from time to time one of the above-described alternative operations and command the driving unit 6 to carry out the selected operation.

[0096] In this case, the selection by control unit 7 can be based on additional detection data (not shown) indicative of physical quantities characterising the behaviour of the switching apparatus, such as the currents circulating along the electric poles, the operating temperatures of the electric poles, vibrations of mechanical parts, and so on. Conveniently, these additional detection data may be provided by further sensing means (not shown) arranged in the switching apparatus and operatively coupled to the control unit 7.

[0097] According to an aspect of the invention, the control unit 7 is configured to command the driving unit 6 to increase the level of the hold current I H , if there occur frequent events in which the movable contacts 11 of the electric poles are subject to undesired movements.

[0098] Preferably, the control unit 7 counts the number of events, in which the movable contacts 11 are subject to undesired movements over a predefined time window, and it commands the driving unit 6 to feed the electromagnetic actuator 4 with a hold current I H having a higher intensity (when the switching apparatus is in a closed state), if the counted number of events exceeds a predefined count value.

[0099] The above-described solution is quite advantageous as it allows to increase adaptively the immunity level of the switching apparatus to mechanical phenomena of exogenous nature, for example to undesired vibrations of the mechanical parts operationally connected to the mobile contacts.

[0100] Preferably, the control unit 7 of the switching apparatus comprises a supervisor block 72 configured to carry out the functionalities described above by interacting with the regulator block 71.

[0101] The supervisor block 72 may be digitally or analogically implemented. In the first case, a microcontroller of the control unit 7 can execute suitable software instructions for carrying out the functionalities the functionalities of the supervisor block. In the second case, the control unit 7 may include suitable electronic circuits suitably configured to carry out the functionalities of the supervisor block.

[0102] The control unit 7 may be obviously configured to carry out different functionalities of known type in addition to those described above. For example, it is conveniently configured to manage the standard opening and closing manoeuvres of the switching apparatus as explained above, or carry out other data processing functionalities or communication functionalities. According to some embodiments of the invention, the control unit 7 may be structurally integrated with the driving unit 6 in a same power and control unit.

[0103] As it is apparent from the above, in another aspect, the present invention relates to a control method 100 for controlling a switching apparatus 1 for electrical applications.

[0104] Preferably, the control method 100 comprises a step 101 of acquiring detection data D indicative of the behaviour of an excitation current I L , I H provided to the electromagnetic actuator 4 by the driving unit 6. As mentioned above, the detection data D are provided by suitable sensing means 8 of the switching apparatus.

[0105] Preferably, the control method 100 comprises a step 102 of determining whether the movable contacts 11 of the electric poles are subject to undesired movements away from the coupled position B when said switching actuator is in a closed state. Such a determination step is carried out based on the behaviour of the hold current I H provided to the electromagnetic actuator 4 by said driving unit 6 to maintain said movable contacts in the coupled position B.

[0106] Preferably, the movable contacts 11 of the electric poles are determined to be subject to undesired movements if the hold current I H or its derivative over time exceeds a predefined threshold value.

[0107] Preferably, the control method 100 comprises a step 103 of commanding the driving unit 6 to change the feeding of the electromagnetic actuator 4, if it is determined that the movable contacts 11 of the electric poles are subject to undesired movements away from the coupled position B.

[0108] Preferably, this last step of the method of the invention includes commanding the driving unit 6 to carry out one of the following alternative operations: a) stop feeding the electromagnetic actuator 4 with the hold current I H in such a way to allow the opening springs 5 of the actuation assembly to move the movable contacts 11 to the uncoupled position A; or b) feed the electromagnetic actuator 4 with a launch current I L (higher than the hold current I H ) to move the movable contacts 11 back to the coupled position B and feed again the electromagnetic actuator 4 with the hold current I H to maintain the movable contacts 11 in the coupled position B, once the movable contacts 11 have moved back to said coupled position.

[0109] Preferably, the control method 100 comprises a step 104 of counting, over a predefined time window, the number of events, in which the movable contacts 11 of the electric poles are subject to undesired movements, when the switching apparatus is in a closed state.

[0110] Preferably, the control method 100 comprises a step 105 of commanding the driving unit 6 to feed the electromagnetic actuator 4 with a higher hold current I H when the switching apparatus is in a closed state, if the counted number of events exceeds a predefined count value.

[0111] The control method 100 is particularly adapted to be carried out by an electronic device included in or operatively associated to the switching apparatus.

[0112] Advantageously, the control method 100 is carried out by a control unit 7 of the switching apparatus, for example by a supervisor block 72 of said control unit, which may be digitally or analogically implemented as illustrated above.

[0113] The switching apparatus and the control method, according to the present invention, provides remarkable advantages with respect to the solutions of the state of the art.

[0114] The switching apparatus of the invention can manage effectively possible events, in which the movable contacts of the electric poles are subject to undesired movements, when said switching apparatus is in a closed state.

[0115] This allows preventing or avoiding undesired events, such as sudden arcing phenomena between the coupled contacts of the electric poles or uncontrolled opening manoeuvres of the switching apparatus.

[0116] The switching apparatus of the invention can therefore ensure higher levels of reliability compared to traditional switching apparatuses of the state of the art.

[0117] The switching apparatus of the invention is of relatively easy manufacturability at industrial levels, at competitive costs with respect to the solutions of the state of the art.

Claims

1. A switching apparatus (1) for electrical applications comprising: - one or more electric poles; - for each electric pole, one or more fixed contacts (10) and one or more movable contacts (11), wherein said movable contacts (11) are reversibly movable between an uncoupled position (A), at which said movable contacts are decoupled from said fixed contacts (10), and a coupled position (B), at which said movable contacts are coupled with said fixed contacts; - an actuation assembly (3) including an electromagnetic actuator (4) and one or more opening springs (5) operatively coupled to said movable contacts (11), wherein said electromagnetic actuator (4) is adapted to provide actuation forces directed in such a way to move said movable contacts (11) towards said coupled position (B), wherein said opening springs (5) are adapted to provide actuation forces directed in such a way to move said movable contacts (11) towards said uncoupled position (A), - a driving unit (6) electrically connected to said electromagnetic actuator (4) and adapted to feed said electromagnetic actuator with an excitation current (IL, IH) to operate said electromagnetic actuator; - a control unit (7) operatively coupled to said driving unit (6) to control said driving unit; characterised in that said control unit (7) is configured to determine whether said movable contacts (11) are subject to undesired movements away from said coupled position (B), when said switching apparatus is in a closed state, based on the behaviour of a hold current (IH) provided to said electromagnetic actuator (4) by said driving unit (6) to maintain said movable contacts in said coupled position (B), wherein said control unit (7) is configured to command said driving unit (6) to change the feeding of said electromagnetic actuator (4), if it is determined that said movable contacts (11) are subject to undesired movements, when the switching apparatus is in closed state.

2. Switching apparatus according to claim 1, characterised in that said control unit (7) is configured to command said driving unit (6) to carry out one of the following alternative operations: a) stop feeding said electromagnetic actuator (4) with said hold current (IH) in such a way to allow said opening springs (5) to move said movable contacts (11) to said uncoupled position (A); or b) feed said electromagnetic actuator (4) with a launch current (IL), which is higher than said hold current (IH), to move said movable contacts (11) back to said coupled position (B) and feed again said electromagnetic actuator with said hold current (IH) to maintain said movable contacts (11) in said coupled position (B), once said movable contacts have moved back to said coupled position; if it is determined that said movable contacts (11) are subject to undesired movements away from said coupled position (B), when the switching apparatus is in closed state.

3. Switching apparatus according to one of the previous claims, characterised in that said control unit (7) is configured to determine that said movable contacts (11) are subject to undesired movements away from said coupled position (B), if said hold current (IH) or a derivative over time of said hold current exceeds a predefined threshold value.

4. Switching apparatus according to one of the previous claims, characterised in that said control unit (7) is configured to acquire detection data (D) indicative of the behaviour of an excitation current (IL, IH) provided to said electromagnetic actuator (4) by said driving unit (6), wherein said detection data are provided by sensing means (8) operatively coupled to said electromagnetic actuator (4).

5. Switching apparatus according to one of the previous claims, characterised in that said control unit (7) is configured to count the number of events over a predefined time window, in which said movable contacts (11) are subject to undesired movements away from said coupled position (B), when the switching apparatus is in closed state, wherein said control unit (7) is configured to command said driving unit (6) to feed said electromagnetic actuator (4) with a hold current (IH) having a higher intensity when the switching apparatus is in closed state, if the counted number of events exceeds a predefined count value.

6. Switching apparatus according to one of the previous claims, characterised in that it is a medium voltage switching apparatus.

7. Switching apparatus according to one of the previous claims, characterised in that it is adapted to be installed in railway electrical systems.

8. A control method (100) for controlling a switching apparatus (1) for electrical applications, wherein said switching apparatus comprises: - one or more electric poles; - for each electric pole, at least a fixed contact (10) and a corresponding movable contact (11) reversibly movable between an uncoupled position (A), at which said movable contact is decoupled from said fixed contact, and a coupled position (B), at which said movable contact is coupled with said fixed contact; - an actuation assembly (3) including an electromagnetic actuator (4) and one or more opening springs (5) operatively coupled to said movable contacts (11), wherein said electromagnetic actuator (4) is adapted to provide actuation forces directed in such a way to move said movable contacts (11) towards said coupled position (B), wherein said opening springs (5) are adapted to provide actuation forces directed in such a way to move said movable contacts (11) towards said uncoupled position (A), - a driving unit (6) electrically connected to said electromagnetic actuator (4) and adapted to feed said electromagnetic actuator with an excitation current (IL, IH) to operate said electromagnetic actuator; characterised in that said control method (100) comprises the following steps: - determining (102) whether said movable contacts (11) are subject to undesired movements away from said coupled position (B) when said switching actuator is in a closed state, based on the behaviour of an excitation current (IH) provided to said electromagnetic actuator (4) by said driving unit (6) to maintain said movable contacts in said coupled position (B); - if it is determined that said movable contacts (11) are subject to undesired movements, commanding (103) said driving unit (7) to change the feeding of said electromagnetic actuator (4).

9. Control method according to claim 8, characterised in that the step of commanding (103) said driving unit (6) to change the feeding of said electromagnetic actuator (4) includes commanding said driving unit to carry out one of the following alternative operations: a) stop feeding said electromagnetic actuator (4) with said hold current (IH) in such a way to allow said opening springs (5) to move said movable contacts (11) to said uncoupled position (A); or b) feed said electromagnetic actuator (4) with a launch current (IL), which is higher than said hold current (IH), to move said movable contacts (11) back to said coupled position (B) and feed again said electromagnetic actuator with said hold current (IH) to maintain said movable contacts (11) in said coupled position (B), once said movable contacts have moved back to said coupled position;10. Control method according to one of the claims from 8 to 9, characterised in that said movable contacts (11) are determined to be subject to undesired movements away from said coupled position (B), if said hold current (IH) or a derivative over time of said hold current exceeds a predefined current value.

11. Control method according to one of the claims from 8 to 10, characterised in that it comprises acquiring (101) detection data (D) indicative of the behaviour of an excitation current (IL, IH) provided to said electromagnetic actuator (4) by said driving unit (6) from sensing means (8) operatively coupled to said electromagnetic actuator (4).

12. Control method according to one of the claims from 8 to 11, characterised in that it comprises the following steps: - counting (104), over a predefined time window, the number of events, in which said movable contacts (11) are subject to undesired movements away from said coupled position (B), when the switching apparatus is in a closed state; - commanding (105) said driving unit (6) to feed said electromagnetic actuator (4) with a higher hold current (IH) when the switching apparatus is in a closed state, if the counted number of events exceeds a predefined count value.

13. Control method according to one of the claims from 8 to 12, characterised in that said switching apparatus (1) is a medium voltage switching apparatus.

14. Control method, according to one of the claims from 8 to 13, characterised in that said switching apparatus (1) is adapted to be installed in railway electrical systems.

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