Method for operating a contactor and electrical operating environment with a contactor

Abstract

In various embodiments, a method for operating a contactor (S3, S4) is provided, comprising: adjusting the switching current flowing through the contactor (S3, S4) during the switching process to a regeneration value that is greater than the switching current during the regular operation of the contactor (S3, S4). Furthermore, an electrical operating environment with a contactor is provided.

Description

[0001] The present invention relates to a method for operating a contactor and an electrical operating environment with a contactor.

[0002] A contactor, also known simply as a contactor, is an electromechanical switch designed for switching particularly high loads. A key characteristic of a contactor is its monostable switching behavior, meaning it remains in only one switching state—the off state—without requiring a control signal. The on state, however, requires a control current in the contactor's control circuit, which electromagnetically maintains the on state.

[0003] Contactors are generally used to protect electrical components and play a particularly important role in electric vehicles, for example, between the traction battery and the inverter of the electric motor. Contactors are also installed in wallboxes and charging stations for electric vehicles and are responsible for switching the charging current to the electric vehicle when charging is authorized.

[0004] When contactors are switched, a voltage difference typically exists between the two components or circuit parts that are to be electrically connected by the contactor, for example, between a traction battery and the DC link capacitors in the drive circuit or the auxiliary circuit of an electric vehicle. Due to this voltage difference, a compensating current flows when the contactor is switched on. The magnitude of this current depends on the capacitance and the voltage difference. This compensating current, which is usually greater than the current flowing through the contactor after the switch-on process, can damage the contactor over its service life (material erosion, corrosion, etc.). This can have the adverse effect of a contactor being damaged before the end of its nominal service life and having to be replaced.To counteract this effect, pre-charging circuits are used to pre-charge the circuit part with the lower voltage, thus reducing the voltage difference driving the equalizing current.

[0005] In this context, German patent application DE 10 2022 205 387 A1 discloses a method for determining a surface regeneration parameter of a contact surface of an electrical contactor, in particular a contactor in a vehicle, wherein the surface regeneration parameter is representative of the regeneration of the contactor's contact surface during a closed state of the contactor. The method includes determining a load current flowing through the closed contactor, determining the duration during which the contactor is closed, and determining the surface regeneration parameter based on the determined load current and the determined duration.

[0006] In light of the aforementioned prior art, the object of the present invention can be seen as providing a measure by which the service life of a contactor can be extended.

[0007] This problem is solved by means of the subject matter of the independent claims. Further preferred embodiments are found in the dependent claims.

[0008] The present invention is based on the finding that a high equalization current in contactors can also have positive effects on contactors that have already aged. This finding is based on switching tests carried out with contactors. A higher switching current can lead to the removal of deposits and a reduction in the contactor's contact resistance.

[0009] The voltage drop across a contactor, which sometimes determines the magnitude of the equalizing current when switching on, can be adjusted by appropriately pre-charging the circuit section with the lower voltage, which may even be zero before switching on. In the case of an electric vehicle, the circuit section can include an auxiliary load path that is pre-charged to a target voltage by means of a DC / DC converter.

[0010] The present invention aims to deliberately set a higher voltage differential than usual for each xth switching operation, resulting in an increased switching current. This measure can extend the service life of the contactor.

[0011] Although the present description is geared towards a contactor, what has been said here and in particular the principle of the invention naturally applies to the contactors that are usually installed in pairs, one of which is arranged in the supply line and one in the return line of a circuit.

[0012] According to the invention, a method for operating a contactor is provided, comprising adjusting the switching current flowing through the contactor during the switching process to a regeneration value that is greater than the switching current during regular operation of the contactor. A switching current (also referred to as inrush current) is understood to be the current that flows immediately after the contactor is switched on and is generally greater than the rated or operating current flowing after the switching phase has ended. Adjusting the switching current to the regeneration value therefore involves its intended increase compared to a regularly set switching current.

[0013] The switching current during regular operation of the contactor can correspond to the switching current during the last switching operation. In a further embodiment, the switching current during regular operation can correspond to the higher switching current during at least the last two switching operations. More than two switching operations can also be considered to determine the switching current level during regular operation. The present method involves an intentional and substantial increase in the switching current to utilize its beneficial effect on the service life of the power contactor.

[0014] The regeneration value of the switching current can correspond to a deliberate "outlier" in a series of switching current values, which includes at least one previous, preferably two, three or more switching operations and at least one subsequent, preferably two, three or more switching operations.

[0015] According to further embodiments of the method according to the invention, the adjustment of the switching current flowing through the contactor during the switching process to the regeneration value can be carried out at a recurring interval, wherein the interval includes a predetermined number of switching processes.

[0016] According to further embodiments of the method according to the invention, adjusting the switching current flowing through the contactor during the switching process can involve setting a pre-charge voltage to which a current path connected to the contactor is pre-charged. As already explained, the magnitude of the equalizing current depends on the voltage difference and on the capacitance values, such as the capacitance values ​​of DC link capacitors, in the current path connected to the contactor, in the direction of which the energy transfer through the contactor takes place.

[0017] According to further embodiments of the method according to the invention, a first terminal of the contactor can be connected to a first current path, which in turn is coupled to or has an energy source (e.g. a traction battery in an electric vehicle), and a second terminal of the contactor can be connected to a second current path, which has a pre-charging device for providing the pre-charging voltage.

[0018] According to the invention, an electrical operating environment with a contactor is further provided in which the previously described method is implemented. The electrical operating environment comprises a first current path, which includes a power source and is connected to a terminal of the contactor; a second current path, which includes a pre-charging device and is connected to a second terminal of the contactor; and a control unit, which is configured to activate the pre-charging device before the contactor is switched on, in order to pre-charge the second current path and limit the switching current flowing during switching. The control unit is also configured to execute the method according to one of the previously described embodiments.

[0019] According to another embodiment of the electrical operating environment, it can be located in an electric vehicle, wherein the first current path connects a traction battery to the contactor and the second current path has an intermediate circuit capacitor.

[0020] The features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0021] Further advantages and embodiments of the invention will become apparent from the following description of exemplary embodiments and the accompanying drawing.

[0022] In Fig.Figure 1 shows an exemplary electrical operating environment in which the method according to the invention can be applied. However, it should be emphasized that this is only an exemplary application scenario, which should not be understood as limiting the fundamental scope of application of the invention.

[0023] The electrical operating environment is located within an electrical infrastructure 1 in an electric vehicle. The central element is the traction battery 2, which here comprises a first bank 21 and a second bank 22, connected in series by means of a safety contactor S0. The traction battery 2 can be connected to different circuits via pairs of contactors S1-S6.

[0024] The first circuit 3 corresponds to the drive path and includes an inverter 31, which may, for example, be a pulse inverter, connected upstream of an electric machine 31. A first intermediate circuit capacitor C1 is connected between the inputs of the inverter 31. The first circuit 3 can be connected to the traction battery 2 by closing the first contactor S1 and the second contactor S2.

[0025] The second circuit 4 corresponds to an auxiliary load path and comprises a series connection of an auxiliary load 41 (e.g., the vehicle electrical system) and a second intermediate circuit capacitor C2. A DC-DC converter 42 is connected in parallel. The second circuit 4 can be connected to the traction battery 2 by closing the third contactor S3 and the fourth contactor S4.

[0026] The DC-DC converter 42 corresponds to a pre-charging unit with which the second circuit 4 can be pre-charged to a predetermined pre-charging voltage before the third and fourth contactors S3 and S4 are switched on. In order to avoid or at least minimize a switching current, the second circuit 4 is pre-charged to a predetermined voltage by means of the DC-DC converter, which is usually close to the voltage of the energy source supplying the second circuit 4 – in the example shown, the traction battery 2.

[0027] The present invention involves deliberately adjusting the switching current flowing through the third and fourth contactors S3 and S4 during the switching process to a regeneration value that is higher than the value of the normally set switching current. For this purpose, the pre-charging voltage can be reduced compared to its normally set value or even left at zero.

[0028] By means of the DC-DC converter 42 in the second circuit 4, the first intermediate circuit capacitor C1 can be pre-charged to a predetermined pre-charge voltage in the same way, by connecting the first circuit 3 and the second circuit to each other via the corresponding contactors S1-S4 (the safety contactor remains open). By reducing the normally set pre-charge voltage or (more generally) by omitting the pre-charge process, the switching current when connecting the first circuit 3 to the traction battery 2 can be deliberately increased.

[0029] In the electrical infrastructure 1, a third circuit 5 is additionally shown, which represents the charging station path, essentially comprising charging station 51. By closing the fifth contactor S5 and the sixth contactor S6, the traction battery can be charged by charging station 51. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2022 205 387 A1

[0005]

Claims

[1] Method for operating a contactor (S3, S4), comprising: Adjusting the switching current flowing through the contactor (S3, S4) during the switching process to a regeneration value that is greater than the value of the switching current in the regular operation of the contactor (S3, S4). [2] Method according to claim 1, wherein the value of the switching current in the regular operation of the contactor (S3, S4) corresponds to the value of the switching current during the last switching operation of the contactor (S3, S4). [3] Method according to claim 1 or 2, wherein the value of the switching current in the regular operation of the contactor (S3, S4) corresponds to the higher value of the switching current during at least the last two switching operations of the contactor (S3, S4). [4] Method according to any one of claims 1 to 3, wherein the adjustment of the switching current flowing through the contactor (S3, S4) during the switching process to the regeneration value takes place at a recurring interval, wherein the interval includes a predetermined number of switching processes. [5] Method according to any one of claims 1 to 4, wherein the adjustment of the switching current flowing through the contactor (S3, S4) during the switching process comprises: Setting a pre-charge voltage to which a current path (3, 4) connected to the contactor (S3, S4) is pre-charged. [6] Method according to claim 4, wherein a first terminal of the contactor (S3, S4) is connected to a first current path which is in turn coupled to or has a power source (2), and a second terminal of the contactor (S3, S4) is connected to a second current path (4) which has a pre-charging device (42) for providing the pre-charging voltage. [7] Electrical operating environment comprising a contactor (S3, S4): a first current path which has a power source (2) and is coupled to a terminal of the contactor (S3, S4); a second current path (4) which includes a pre-charging device (42) and is coupled to a second terminal of the contactor (S3, S4); a control unit which is configured to control the pre-charging device (42) before the switching contactor (S3, S4) is switched on, in order to pre-charge the second current path (4) in order to limit the switching current flowing when switching on, wherein the control unit is further configured to execute the method according to one of the preceding claims. [8] Electrical operating environment according to claim 6, which is located in an electric vehicle; wherein the first current path connects a traction battery (2) to the contactor (S3, S4); and wherein the second current path (4) has an intermediate circuit capacitor (C2).

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