Method for protecting a contactor and associated contactor

Abstract

This contactor (2) comprises a main switch (10) connected between an upstream connection point (6) and a downstream connection point (8), and, in parallel, an assembly (16) comprising a secondary switch (20), connected in series with a unidirectional conductive component (18). A processing unit (30) is configured to receive switching commands, control a sequence of opening and / or closing of the main switch and the secondary switch, the secondary switch being closed during a time range for processing the switching command, the main switch being operated when the secondary switch is closed.The computing unit performs a voltage level monitoring at an intermediate point (28), and when the voltage level is above a value of a first predetermined voltage threshold, outside a time range for processing a switching command, detects a malfunction of the secondary switch, and commands a closure of the main switch.

Description

[0001] The present invention relates to a method for protecting a contactor intended to establish, in the closed position, or to interrupt, in the open position, a circulation of a main electric current between a source of electrical energy and at least one electrical load, the electrical energy being supplied under an alternating electrical voltage.

[0002] The invention also relates to a contactor implementing such a protection method.

[0003] The invention lies in the field of electrical contactors, usually applied to establish or interrupt a flow of electric current between an electrical energy source and one or more electrical loads. In other words, a contactor is used for energizing electrical loads, such loads being able to be any type of electrical device, for example motor, heating device or lighting device.

[0004] Such contactors open and close on command, for example manually or remotely. Advantageously, the control is electrical.

[0005] The opening and closing operation uses electrical contacts comprising contact pads, which are likely to wear out physically after a certain number of operations.

[0006] In addition, it is preferable to design contactors with reduced dimensions, allowing them to occupy as little space as possible in a cabinet or electrical panel, while reducing wear in order to increase their lifespan.

[0007] Patent FR 3 099 289 describes a contactor with improved electrical endurance, comprising two switches, a first switch which is a main switch, connected between an upstream connection point intended for connection to the electrical energy source and a downstream connection point intended for connection of the electrical load(s) and an assembly formed by a second switch, which is a secondary switch, connected in series with a unidirectional conductive component, the assembly being connected in parallel with the main switch. This patent describes a method for controlling the main and secondary switches, ensuring, in nominal operation, that the main switch is switched open or closed when the secondary switch is closed, and consequently the switching of the main switch is carried out without switching electric current, therefore without any notable effect on the contacts of this switch.Similarly, the switching of the secondary switch is carried out without switching electric current, therefore without any noticeable effect on the contacts of this switch, thanks to the unidirectional conductive component and a switching command during the blocked state of this component.

[0008] Thus, in nominal operation, such a contactor is more robust and has an increased service life.

[0009] To ensure a small overall footprint, and to obtain a contactor with reduced dimensions, it is interesting to choose switches with different specifications, in particular a main switch which supports the main current, and a secondary switch which supports a lower current, given that the secondary switch is intended to support the main current for a very short duration, for example a duration less than half a period of the main current (i.e. less than 10 milliseconds for a 50 Hz current).

[0010] However, for such a contactor, a possible electrical fault or malfunction can cause damage to one or other of the switches, and more particularly to the secondary switch, which can then no longer perform the functionality initially intended.

[0011] There is therefore a need to improve the protection of such a contactor against malfunctions, while retaining the advantages of robustness and compactness.

[0012] For this purpose, the invention relates to a method for protecting a contactor intended to establish, in the closed position, or to interrupt, in the open position, a circulation of a main electric current between an electrical energy source and at least one electrical load, the electrical energy being supplied under an alternating electrical voltage, the contactor having an upstream connection point intended for a connection to the electrical energy source and a downstream connection point intended for a connection of said at least one electrical load, the contactor comprising a main switch connected between the upstream connection point and the downstream connection point, and an assembly comprising a secondary switch, connected in series with a unidirectional conductive component, said assembly being connected between the upstream connection point and the downstream connection point in parallel with the main switch,the contactor further comprising a calculation unit configured to receive switching commands from the contactor and to control an opening and / or closing sequence of the main switch and the secondary switch, depending on the switching command received and a direction of polarity of the alternating electrical voltage, the secondary switch being closed during a time range for processing the switching command, the main switch being controlled to open or close when the secondary switch is closed.,

[0013] This method involves the implementation by the calculation unit of steps of: monitoring a voltage level at an intermediate point located between the secondary switch and the unidirectional conductive component, when said voltage level is greater than a value of a first predetermined voltage threshold, outside a time range for processing a switching command, detecting a malfunction of the secondary switch, and controlling a closing of the main switch.

[0014] Advantageously, monitoring the voltage level makes it possible to detect abnormal closure of the secondary switch, and to take immediate measures to avoid subsequent damage to the contactor.

[0015] The method for protecting a contactor according to the invention may have one or more of the characteristics below, taken independently or in any acceptable combination.

[0016] Voltage level monitoring is performed continuously or with a chosen time frequency.

[0017] The method further comprises: following a reception of a switching command, a comparison of the voltage level at the intermediate point with a value of a second voltage threshold, and if the voltage level at the intermediate point is lower than the value of the second voltage threshold during the time range of processing of the switching command, detection of malfunction of the secondary switch; following a reception of a switching command, the steps of: determining a voltage difference between an input voltage, as measured at the upstream connection point, and an output voltage, as measured at the downstream connection point, comparing said voltage difference with a predetermined voltage difference threshold, and, if said voltage difference is greater than the predetermined voltage difference threshold, detecting a malfunction of the secondary switch;following detection of a malfunction of the secondary switch, a command to block the contactor; following detection of a malfunction of the secondary switch, implementation of an indicator of the malfunction state of the contactor; following reception of a command to switch to the open position, monitoring of a voltage level at the downstream connection point, and if said voltage level at the downstream connection point is greater than a value of a third voltage threshold during the time range for processing the command, implementation of a predetermined number N of opening attempts, and an indication of an error state of the contactor. if after N opening attempts, the voltage level at the downstream connection point remains greater than the value of the third voltage threshold, a command to block the contactor and implementation of an indication of a malfunction state of the contactor;following receipt of a command to switch to the closed position, monitoring of a voltage level at the downstream connection point, and if said voltage level at the downstream connection point is lower than a value of a fourth voltage threshold during the time range for processing the command, implementation of a predetermined number M of closing attempts, and an indication of an error state of the contactor; if after M closing attempts, the voltage level at the downstream connection point remains lower than the value of the fourth voltage threshold, control of blocking of the contactor and implementation of an indication of a malfunction state of the contactor. ;

[0018] The invention also relates to a contactor intended to establish, in the closed position, or to interrupt, in the open position, a circulation of a main electric current between an electrical energy source and at least one electrical load, the electrical energy being supplied under an alternating electrical voltage, the contactor having an upstream connection point intended for a connection to the electrical energy source and a downstream connection point intended for a connection of said at least one electrical load, the contactor comprising a main switch connected between the upstream connection point and the downstream connection point, and an assembly comprising a secondary switch, connected in series with a unidirectional conductive component, said assembly being connected between the upstream connection point and the downstream connection point in parallel with the main switch,the contactor further comprising a calculation unit configured to receive switching commands from the contactor and to control an opening and / or closing sequence of the main switch and the secondary switch, depending on the switching command received and a direction of polarity of the alternating electrical voltage, the secondary switch being closed during a time range for processing the switching command, the main switch being controlled to open or close when the secondary switch is closed, the calculation unit being configured to implement a protection method as briefly described above.,

[0019] This contactor further comprises a first voltage measurement module at the upstream connection point, a second voltage measurement module at the downstream connection point and a third voltage measurement module at the intermediate point, each of said modules being connected to the calculation unit.

[0020] In one embodiment, the primary switch is a bistable electromechanical relay and the secondary switch is a monostable electromechanical relay.

[0021] Other characteristics and advantages of the invention will emerge from the description given below, for information purposes only and in no way limiting, with reference to the appended figures, among which: there figure 1 is a block diagram of a contactor according to one embodiment; the figure 2 is a diagram illustrating a sequence of switch states following a command to close the contactor in nominal operation; figure 3 is a diagram illustrating a sequence of switch states following a command to open the contactor in nominal operation; the figure 4 is a synopsis of the main steps of a contactor protection method for detecting a malfunction of the secondary switch; figure 5 represents another embodiment of certain steps of a method for protecting a contactor for detecting a malfunction of the secondary switch; figure 6 is a synopsis of the main steps of a contactor protection process for detecting a malfunction of the main switch.

[0022] There figure 1 illustrates a contactor 2 intended to establish, in the closed position, or to interrupt, in the open position, a circulation of a main electric current I between an electrical energy source 4 and at least one electrical load 5, the electrical energy being supplied under an alternating electrical voltage.

[0023] In the figure 1 , a single electrical load 5 has been shown, it being understood that the electrical load 5 may consist of one or more electrical devices such as motors, heating resistors, lighting devices, or any other device requiring a connection to an electrical energy source.

[0024] The electrical energy source 4 is for example an electrical energy distribution network or an electrical energy generator, and provides a predefined alternating voltage Ug, for example 240 Volt and 50 Hertz.

[0025] The contactor 2 comprises an upstream connection point 6 and a downstream connection point 8, the upstream connection point 6 being intended to be connected to the electrical energy source 4 and the downstream connection point 8 being intended to be connected to the electrical load 5.

[0026] The electrical energy source 4 is connected on the one hand to the upstream connection point 6 and on the other hand to the electrical load 5. The connection between the electrical energy source 4 and the electrical load 5 is for example a phase line or a neutral line.

[0027] In order to clarify the description, the alternating electrical voltage Ug is referenced relative to a potential reference point 12 which may or may not be integrated into the contactor.

[0028] The contactor 2 also includes a main switch 10 connected between the upstream connection point 6 and the downstream connection point 8.

[0029] The contactor 2 also comprises an assembly 16 connected in parallel with the main switch 10 between the upstream connection point 6 and the downstream connection point 8, the assembly 16 comprising a secondary switch 20 connected in series with a unidirectional conductive component 18.

[0030] In the embodiment of the figure 1 , the unidirectional conductive component 18 is a diode, the anode of which is arranged on the side of the electric current source 4 and the cathode on the side of the electric load 5. Alternatively, the unidirectional conductive component 18 may be a thyristor.

[0031] The contactor 2 further comprises a first module 22 for measuring voltage at the upstream connection point 6, a second module 24 for measuring voltage at the downstream connection point 8 and a third module 26 for measuring voltage at an intermediate point 28, located between the secondary switch 20 and the unidirectional conductive component 18, and more precisely downstream of the secondary switch 20 and upstream of the unidirectional conductor 18.

[0032] The contactor 2 also comprises a calculation unit 30, produced for example in the form of one or more microprocessors or microcontrollers, or in the form of logic circuits, or discrete components, for example in an ASIC (from the English Application Spécifie Integrated Circuit ) .

[0033] The first, second and third voltage measurement modules provide the voltage measurements to the computing unit 30.

[0034] The computing unit 30 is configured to receive switching commands from the contactor, from a remote device 35, via a wired or wireless communication link. For example, the communication link is wireless and the remote device 35 is a remote control.

[0035] In one embodiment, the computing unit 30 is programmed, remotely via an application or locally via a human-machine interface, to implement switching commands, for example triggered by the internal clock of the computing unit 30.

[0036] In one embodiment, the first voltage measurement module 22, the second voltage measurement module 24 and the third voltage measurement module 26 are each implemented by a circuit comprising a voltage divider bridge, an additional calculation to obtain the measurement of a corresponding voltage level being performed by the calculation unit 30.

[0037] In nominal operation, upon receipt of a switching command from the contactor 2, the calculation unit 30 is configured to command an opening and / or closing sequence of the secondary switch 20 and the main switch 10, as a function of the switching command received and a direction of polarity of the alternating electrical voltage Ug, by performing opening and closing operations of each of the switches 10, 20 with low electrical current at their terminals in order to protect them from mechanical wear. This nominal operation is detailed below, more particularly with reference to figures 2 And 3 .

[0038] In one embodiment, the main switch 10 is an electromechanical relay comprising at least one movable contact, controlled by a coil, for establishing contact with a fixed contact. Such an electromechanical relay is a compact, inexpensive component and the mechanical resistance between the closed contacts is low.

[0039] Preferably, the secondary switch 20 is also an electromechanical relay.

[0040] In a preferred embodiment, the main switch 10 is a bistable electromechanical relay and the secondary switch 20 is a monostable electromechanical relay, which has a smaller footprint than a bistable electromechanical relay. Thus, the overall volume of the contactor 2 is smaller.

[0041] Furthermore, preferably, the main switch 10 is an electromechanical relay capable of switching a nominal current less than or equal to, for example, 20 or 25 Amperes at a voltage of 240 Volts. The secondary switch 20 may advantageously be smaller than the size of the main switch 10, for example five to ten times smaller in volume / size, because it is intended to support the main electric current I for a very short duration, for example less than half a period of the main electric current I (i.e. a duration less than 10 ms for a current at 50 Hz), whereas the main switch 10 must support the main electric current I for an indefinite duration, depending on the duration between a closing and opening command of the switch.

[0042] There figure 2 illustrates the sinusoidal alternating voltage signal Ug as a function of time on a first graph 50, as well as the direction of polarity of the alternating voltage, indicated by the symbols “+” and “-”. The sinusoidal alternating voltage signal has a period of duration T. During a half-period T1 (respectively T3), the alternating voltage Ug is positive, and the direction of polarity is positive. During a following half-period T2 (respectively T4), the alternating voltage Ug is negative, and the direction of polarity is negative. The sum of the half-periods T1 and T2 is equal to the period T.

[0043] There figure 2 illustrates the open or closed states of the main switch 10 and the secondary switch 20 over the half-periods T1, T2, T3, T4, forming a sequence of states following a closing switching command of the contactor 2, i.e. a command to switch from an open state to a closed state of the contactor 2.

[0044] In order to better protect the contacts of the switches 10, 20 from electrical wear (wear of the contact pads), it is provided that the secondary switch 20 is operated when the unidirectional conductive component 18 is in a blocked state, that is to say when the direction of polarity of the alternating electrical voltage Ug imposes an inverse voltage at the terminals of the unidirectional conductive component 18.

[0045] During the half-period T1, the polarity direction of the alternating electric voltage Ug is positive, the two switches 10, 20 are open. During the following half-period T2, the polarity direction of the alternating electric voltage Ug is negative, the unidirectional conductive component 18 is in a blocked state, and the secondary switch 20 is closed. Thanks to the blocked state of the unidirectional conductive component 18, the closing operation of the secondary switch 20 has no notable effect on the contacts of this switch. This secondary switch 20 is kept in the closed position during a time range called the time range for processing the switching command TC.Following the closing of the secondary switch 20, during the half-period T3, when the polarity direction of the alternating electric voltage Ug is positive, the main electric current flows through the secondary switch 20 and the unidirectional conductive component 18, which is then conducting, and the voltage across the terminals of the main switch 10 is low. The computing unit 30 then commands the closing of the main switch 10, the main electric current I then flowing in the main switch 10. During the following half-period T4, the polarity direction of the alternating electric voltage Ug is negative, the unidirectional conductive component 18 is in a blocked state, and the secondary switch 20 is then open without degradation of its contacts, the electric current being zero because blocked by the element 18. The contactor 2 is then in the closed position, in accordance with the command received.

[0046] There figure 2 also schematically illustrates in a second graph 52 the opening / closing state of the secondary switch 20 as a function of time, and in a third graph 54 the opening / closing state of the main switch 10 as a function of time, in the case of processing a contactor closing command.

[0047] Similarly, the figure 3 illustrates the open or closed states of the main switch 10 and the secondary switch 20, in nominal operation, over half-periods T5, T6, T7, T8, forming a sequence of states following a command to switch the contactor 2 to open, i.e. a command to switch the contactor 2 from a closed state to an open state. Initially, the main switch 10 is closed and the secondary switch 20 is open.

[0048] There figure 3 illustrates the sinusoidal alternating voltage signal Ug as a function of time on a first graph 56, as well as the direction of polarity of the alternating voltage, indicated by the symbols “+” and “-”. The sinusoidal alternating voltage signal has a period of duration T. During a half-period T5 (respectively T7), the alternating voltage Ug is positive, and the direction of polarity is positive. During a following half-period T6 (respectively T8), the alternating voltage Ug is negative, and the direction of polarity is negative. The second graph 58 schematically illustrates the open / close state of the secondary switch as a function of time, and the third graph 60 the open / close state of the main switch as a function of time, in the case of processing a contactor opening command, in nominal operation.

[0049] During the half-period T5, the polarity direction of the alternating electric voltage Ug is positive, the main switch 10 is closed, the secondary switch 20 is open. During the following half-period T6, the polarity direction of the alternating electric voltage Ug is negative, the unidirectional conductive component 18 is in a blocked state. Thanks to the blocked state of the unidirectional conductive component 18, the closing operation of the secondary switch 20 has no notable effect on the contacts of this switch. This secondary switch 20 is maintained in the closed position during a time range for processing the switching command TC.Following the closing of the secondary switch 20, during the half-period T7, when the polarity direction of the alternating electric voltage Ug is positive, the calculation unit 30 then commands the opening of the main switch 10, the main electric current I then flowing in the secondary switch 20 and in the unidirectional conductive component. During the following half-period T8, the polarity direction of the alternating electric voltage Ug is negative, the unidirectional conductive component 18 is in a blocked state, and the secondary switch 20 is then open. The contactor 2 is then in the open position, in accordance with the command received.

[0050] As is clear from the description of the figures 2 And 3above, in nominal operation, the main switch 10 is controlled to open or close when the secondary switch 20 is closed, during the time range for processing the switching command and in the positive alternation of the voltage.

[0051] The contactor protection process aims to detect and protect the contactor in the event of a malfunction of one of the switches, i.e. when one of the switches does not behave as in nominal operation.

[0052] In particular, the protection method detects malfunctions of the secondary switch which are of two types: either a first-type malfunction in which the secondary switch is abnormally closed, or a second-type malfunction in which the secondary switch is abnormally open.

[0053] Indeed, the secondary switch 20 may remain abnormally closed following a mechanical or electrical fault, for example following an electrical current overload, or because one of its contacts has become resistive due to a shock wave for example. In this case, in particular when the secondary switch 20 is not sized to withstand the main electrical current over a long period, the secondary switch 20 may be damaged.

[0054] The secondary switch 20 may remain abnormally open, for example, if it is damaged due to a mechanical or electrical fault. In this case, the secondary switch 20 cannot perform the preservation function (zero current / voltage switching) against wear of the contacts of the main switch in nominal operating mode.

[0055] Similarly, the protection process detects malfunctions of the main switch which are of two types: either a third-type malfunction in which the main switch is abnormally closed, or a fourth-type malfunction in which the main switch is abnormally open.

[0056] There figure 4 is a synopsis of the main stages of a method for protecting a contactor of the type described with reference to the figure 1 , implemented by the calculation unit 30 of the contactor. These steps concern the detection of a malfunction of the secondary switch and a protection activation accordingly.

[0057] The method comprises monitoring 80 of a voltage level at the intermediate point 28 (i.e. voltage downstream of the secondary switch 20), this voltage level being provided by the third voltage measurement module 26.

[0058] The monitoring 80 of the voltage level at the intermediate point 28 is carried out continuously or with a given time frequency, asynchronously to any processing 100 of the switching command of the contactor, that is to say independently of any processing 100 in progress of a received switching command. For example, the monitoring 80 of the voltage level at the intermediate point 28 is carried out with a time frequency of the order of 10 to 30 ms. A filtering (or time delay) of 30 to 50 ms can be carried out to avoid the detection of a false fault (such as a temporary shock wave).

[0059] Then it is checked whether the voltage level V int at the intermediate point 28 is greater than a value of a first predetermined voltage threshold V th-F1, outside a time range for processing a switching command, therefore outside a closing in an opening and closing sequence following receipt of a command.

[0060] In the mode of realization of the figure 4 , this verification is carried out in two stages, on the one hand it is verified in step 82 whether the voltage level V int at the intermediate point 28 is greater than the value of the first predetermined voltage threshold V th-F1 , and if V int >V th-F1 , it is also verified (step 84) whether a processing range of a switching command is in progress. The value of the first predetermined voltage threshold V th-F1 is for example between 20V and 50V.

[0061] Exceeding the first predetermined voltage threshold V th-F1 indicates the presence of voltage at the terminals of the secondary switch 20.

[0062] If voltage is present at the terminals of the secondary switch 20, outside a processing range of a switching command, it is deduced that the secondary switch is abnormally closed, it is in a state of first type malfunction.

[0063] Step 84 is then followed by a step 86 of commanding the closing of the main switch, then by command 88 of blocking the contactor. Blocking the contactor results in the refusal to process any switching command from the contactor.

[0064] Furthermore, preferably, the method comprises the implementation 90 of an indicator of the malfunction state, and therefore of the blocking state of the contactor. In this case, the blocking is a blocking in the closed state. For example, the indicator is a warning light located on a visible face of the housing containing the contactor, preferably the front face visible to the user, and the malfunction indicator, here of a malfunction of the first type, is a chosen color of the warning light, for example red, and / or a flashing state of the warning light. Of course, other variants of indicator of a malfunction state of the contactor are conceivable.

[0065] The method also comprises, in the switching command processing 100, following reception of a switching command 102, in addition to implementing the sequence of opening and / or closing the main switch and the secondary switch as a function of the command received, a step 104 of comparing the voltage level V int at the intermediate point 28 with a value of a second voltage threshold V th-O2, and if the voltage level V int at the intermediate point 28 is lower than the value of the second predetermined voltage threshold V th-O2 during the time range of processing of the switching command, a second type of malfunction state is detected, i.e. the secondary switch is abnormally open.

[0066] The value of the second predetermined voltage threshold V th-O2 is for example also between 20V and 50V.

[0067] The fact that the voltage level V int at the intermediate point 28 is lower than the second predetermined voltage threshold V th-O2 indicates an absence of voltage at the terminals of the secondary switch 20, whereas it should be closed according to the control sequence in nominal operation.

[0068] In one embodiment, the first voltage threshold and the second voltage threshold take the same value, also called internal voltage reference, this value being for example equal to 20V.

[0069] In another embodiment, the first voltage threshold and the second voltage threshold take different values.

[0070] According to an alternative embodiment of the invention, during step 104, the voltage difference between an input voltage, as measured at the upstream connection point 6 (V 6 ), and an output voltage, as measured at the downstream connection point 8 (V 8 ), is determined. This voltage difference is compared with a predetermined voltage difference threshold V th . If this voltage difference between the two voltages V 6 and V 8 is greater than this predetermined voltage difference threshold V th then a second type malfunction state is detected, i.e. the secondary switch is abnormally open. The value of this predetermined voltage difference threshold V th is for example also between 20V and 50V.

[0071] Then test 104 is followed by control step 88 for blocking the contactor.

[0072] According to a preferred embodiment of the invention, the main switch remains in the position in which it was before receiving the switching command so as not to risk being damaged during a switchover.

[0073] According to an alternative embodiment of the invention, the main switch is switched to its open position, if it was not already in the open position. The contactor is then locked in the open position. Advantageously, the contactor is thus locked in an open state, which is generally safer.

[0074] According to another alternative embodiment of the invention, the main switch is switched to its closed position. This is particularly advantageous when a problem is detected during the closing operation of the contactor because it avoids re-using the main switch. This may also be more suitable depending on the load connected to the contactor (for example, a load such as smoke extraction ventilation for which it is better for the ventilation to operate continuously rather than being stopped in the event of a problem being detected on the contactor).

[0075] Furthermore, preferably, step 88 is followed by the implementation 90 of an indicator of a malfunction state of the contactor (here malfunction of the second type), and therefore of the blocking state of the contactor.

[0076] It should be noted that according to variants, it is possible to implement separate indicators to indicate a blocking state following a malfunction of the first type (secondary switch abnormally closed) and a blocking state following a malfunction of the second type (secondary switch abnormally open).

[0077] There figure 5 illustrates a variation of detecting a secondary switch malfunction.

[0078] In this embodiment, the method comprises monitoring 80 of the voltage level at the intermediate point 28 and comparing 82 to the first predetermined voltage threshold V th-F1 , which takes a reference voltage threshold value, for example 20V.

[0079] The method then comprises a filtering 83, of predetermined duration, for example 2 ms, making it possible to validate the exceeding of the first predetermined voltage threshold V th-F1 , during the predetermined duration, which makes it possible to avoid detection on a point fault. It is then detected that the sinusoidal voltage signal at the intermediate point has a positive peak value greater than or equal to the value of the first voltage threshold during the predetermined duration (eg 2 ms). Then a peak counter is incremented, in the counter increment step 85.

[0080] It is then checked (step 87) whether the peak counter exceeds a predetermined number of overshoot periods NP, for example NP=3 or NP=5.

[0081] If this is the case, it is deduced that the peak value of the voltage signal at the intermediate point was detected higher than the value of the first voltage threshold during NP periods of the alternating voltage signal, i.e. for a duration greater than 15 ms, preferably a duration greater than 40 ms, and therefore greater than the duration of processing a switching command, which indicates that the secondary switch remained closed outside a time range for processing a switching command. A malfunction of the first type (i.e. secondary switch abnormally closed) is then detected. Step 87 is then followed by step 86 of closing command of the main switch, then command 88 of blocking of the contactor previously described.

[0082] The peak counter is reset to zero if the peak value of the voltage signal at the intermediate point remains below the value of the first voltage threshold for at least one period.

[0083] There figure 6 is a synopsis of the main stages of a method for protecting a contactor of the type described with reference to the figure 1 , implemented by the calculation unit 30 of the contactor for the detection of a malfunction of the main switch and a protection activation accordingly.

[0084] The steps described with reference to the figure 6 are implemented in addition to the steps for detecting a malfunction of the secondary switch.

[0085] Starting from the reception 102 of a switching command from the switch, the method comprises monitoring 106 of the voltage level V out at the downstream connection point 8.

[0086] A distinction is made between an opening command and a closing command.

[0087] In the event of an opening command, the method further comprises a step 108 of comparing the voltage level V out at the downstream connection point with the value of a third predetermined voltage threshold V th-F3 during the time range for processing the command.

[0088] The value of the third voltage threshold is for example greater than or equal to 50 V, preferably greater than or equal to 200 V which is a value close to the peak amplitude of the voltage signal.

[0089] If the voltage level V out at the downstream connection point is higher than the value of the third predetermined voltage threshold V th-F3 during the time range of processing of the command, then the main switch 10 is abnormally closed. If this is not the case, the contactor continues the nominal operating mode 200.

[0090] In one embodiment, a nominal operation indicator is implemented, for example, the indicator is a light located on a visible face (eg the front face) of the housing containing the contactor, and the nominal operation indicator is a chosen color of the light, for example green.

[0091] If the voltage level V out at the downstream connection point is greater than the value of the third predetermined voltage threshold V th-F3 , step 108 is then followed by a step 110 of a new attempt to open the contactor, by implementing the sequence for moving to the open position. An opening attempt counter is initialized.

[0092] As an optional addition, an error indicator is implemented, for example, the indicator is a light located on a visible face of the housing containing the contactor, and the error indicator is a chosen color of the light, for example orange.

[0093] It is tested again in step 112 if the main switch is open, and if the response is positive, the method returns to the nominal operating mode 200.

[0094] In the event of a negative response, the opening attempt counter is incremented (step 114), then compared (step 116) to a predetermined number N of opening attempts.

[0095] For example, N is equal to 10.

[0096] If the opening attempt counter has not reached the predetermined number N of opening attempts, steps 110 to 116 are repeated.

[0097] If after N opening attempts, the main switch has not been opened, then a third type malfunction (main switch abnormally closed) is detected, and the control unit commands 118 the blocking of the contactor. Blocking the contactor results in the refusal to process any switching command from the contactor.

[0098] Furthermore, preferably, the method comprises the implementation 120 of an indicator of the state of malfunction, and therefore of blocking of the contactor.

[0099] Steps 118, 120 are analogous to steps 88, 90 previously described.

[0100] In the event of a closing command, the method further comprises a step 122 of comparing the voltage level V out at the downstream connection point with a fourth predetermined voltage threshold V th-O4 during the time range for processing the command.

[0101] The value of the fourth voltage threshold is for example less than or equal to 50 V.

[0102] In one embodiment, the third voltage threshold and the fourth voltage threshold take the same value, for example between 50V and 100V, for example equal to 50V.

[0103] In another embodiment, the third voltage threshold and the fourth voltage threshold take different values.

[0104] If the voltage level V out at the downstream connection point is lower than the fourth predetermined opening voltage threshold V th-O4 during the time range for processing the command, then the main switch 10 is abnormally open. If this is not the case, the contactor continues the nominal operating mode 200.

[0105] Step 122 is then followed by a step 124 of a new attempt to close the contactor, by implementing the sequence for moving to the closed position. A closing attempt counter is initialized.

[0106] As an optional addition, an error indicator is implemented, for example, the indicator is a light located on a visible face of the housing containing the contactor, and the error indicator is a chosen color of the light, for example orange.

[0107] It is tested again in step 126 if the main switch is closed, and if the response is positive, the method returns to the nominal operating mode 200.

[0108] In the event of a negative response, the closing attempt counter is incremented (step 128), then compared (step 130) to a predetermined number M of closing attempts.

[0109] For example, M is equal to 3.

[0110] If the opening attempt counter has not reached the predetermined number M of closing attempts, steps 124 to 130 are repeated.

[0111] If after M closing attempts, the main switch has not been closed, then a fourth type malfunction (main switch abnormally open) is detected, and the control unit 30 commands 118 the blocking of the contactor. The blocking of the contactor results in the refusal to process any switching command from the contactor.

[0112] Furthermore, preferably, the method comprises the implementation 120 of an indicator of the state of malfunction, and therefore of blocking of the contactor.

[0113] Steps 118, 120 are analogous to steps 88, 90 previously described.

[0114] According to variants, it is envisaged to implement separate indicators to indicate a blocking state following a third type malfunction (main switch abnormally closed) and a blocking state following a fourth type malfunction (main switch abnormally open).

[0115] Advantageously, the protection method described provides protection in the event of malfunctions, for example following a mechanical or electrical fault, of the secondary switch or the main switch, without the need to add numerous electronic components, and therefore while maintaining the compactness of the contactor.

Claims

1. Method for protecting a contactor (2) intended to establish, in the closed position, or to interrupt, in the open position, a circulation of a main electric current between an electrical energy source (4) and at least one electrical load (5), the electrical energy being supplied under an alternating electrical voltage, the contactor (2) having an upstream connection point (6) intended for a connection to the electrical energy source (4) and a downstream connection point (8) intended for a connection of said at least one electrical load (5), the contactor (2) comprising a main switch (10) connected between the upstream connection point (6) and the downstream connection point (8), and an assembly (16) comprising a secondary switch (20), connected in series with a unidirectional conductive component (18), said assembly (16) being connected between the upstream connection point (6) and the downstream connection point (8) in parallel with the main switch (10),the contactor (2) further comprising a calculation unit (30) configured to receive switching commands from the contactor (2) and to control an opening and / or closing sequence of the main switch (10) and the secondary switch (20), as a function of the switching command received and a direction of polarity of the alternating electrical voltage, the secondary switch (20) being closed during a time range for processing the switching command, the main switch (10) being controlled to open or close when the secondary switch is closed, the method being, characterized in thatit comprises an implementation by the calculation unit (30) of steps of: - monitoring (80) of a voltage level at an intermediate point (28) located between the secondary switch (20) and the unidirectional conductive component (18), - when said voltage level is higher (82) than a value of a first predetermined voltage threshold, outside a time range for processing a switching command, detection (84, 87) of a malfunction of the secondary switch, and - command (86) of a closing of the main switch (10).

2. Method according to claim 1, in which the monitoring (80) of the voltage level is carried out continuously or with a chosen time frequency.

3. Method according to any one of claims 1 or 2, further comprising, following reception (102) of a switching command, a comparison (104) of the voltage level at the intermediate point with a value of a second voltage threshold, and if the voltage level at the intermediate point is lower than the value of the second voltage threshold during the time range for processing the switching command, detection of malfunction of the secondary switch.

4. Method according to any one of claims 1 or 2, further comprising, following reception (102) of a switching command, the steps of: - determining a voltage difference between an input voltage, as measured at the upstream connection point (6), and an output voltage, as measured at the downstream connection point (8), - comparing said voltage difference with a predetermined voltage difference threshold, and, if said voltage difference is greater than the predetermined voltage difference threshold, detecting a malfunction of the secondary switch.

5. Method according to any one of claims 1 to 4, further comprising, following the detection of a malfunction of the secondary switch, a control (88) for blocking the contactor.

6. Method according to any one of claims 1 to 5, further comprising, following detection of malfunction of the secondary switch, implementation (90) of an indicator of the malfunction state of the contactor.

7. Method according to any one of claims 1 to 6, further comprising, following reception (102) of a command to switch to the open position, monitoring (106, 108) a voltage level at the downstream connection point (8), and if said voltage level at the downstream connection point (8) is greater than a value of a third voltage threshold during the time range for processing the command, implementation of a predetermined number N of opening attempts, and an indication of the error state of the contactor.

8. Method according to claim 7, in which if after N opening attempts, the voltage level at the downstream connection point remains higher than the value of the third voltage threshold, control (118) for blocking the contactor and implementation (120) of an indication of a malfunction state of the contactor.

9. Method according to one of claims 1 to 8, further comprising, following reception (102) of a command to switch to the closed position, monitoring (106, 122) a voltage level at the downstream connection point (8), and if said voltage level at the downstream connection point (8) is lower than a value of a fourth voltage threshold during the time range for processing the command, implementing a predetermined number M of closing attempts, and an indication of the error state of the contactor.

10. Method according to claim 9, in which if after M closing attempts, the voltage level at the downstream connection point (8) remains below the value of the fourth voltage threshold, control (118) for blocking the contactor and implementation (120) of an indication of a malfunction state of the contactor.

11. Contactor (2) intended to establish, in the closed position, or to interrupt, in the open position, a circulation of a main electric current between an electrical energy source (4) and at least one electrical load (5), the electrical energy being supplied under an alternating electrical voltage, the contactor (2) having an upstream connection point (6) intended for a connection to the electrical energy source (4) and a downstream connection point (8) intended for a connection of said at least one electrical load (5), the contactor comprising a main switch (10) connected and between the upstream connection point (6) and the downstream connection point (8), and an assembly (16) comprising a secondary switch (20), connected in series with a unidirectional conductive component (18), said assembly (16) being connected between the upstream connection point (6) and the downstream connection point (8) in parallel with the main switch (10),the contactor further comprising a calculation unit (30) configured to receive switching commands from the contactor (2) and to control an opening and / or closing sequence of the main switch (10) and the secondary switch (20), as a function of the switching command received and a direction of polarity of the alternating electrical voltage, the secondary switch (20) being closed during a time range for processing the switching command, the main switch (10) being controlled to open or close when the secondary switch is closed, , characterized in that the computing unit (30) is configured to implement a protection method according to claims 1 to 10.

12. Contactor according to claim 11, further comprising a first voltage measurement module (22) at the upstream connection point (6), a second voltage measurement module (24) at the downstream connection point (8) and a third voltage measurement module (26) at the intermediate point (28), each of said modules being connected to the calculation unit (30).

13. Contactor according to claims 10 to 12, wherein the main switch (10) is a bistable electromechanical relay and the secondary switch (20) is a monostable electromechanical relay.

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