WO2024105010A1

WO2024105010A1 - Method for determining a holding voltage nominal value of a relay, method for switching a relay using a holding voltage nominal value determined in this manner, computing unit, assembly, and charging cable

Info

Publication number: WO2024105010A1
Application number: PCT/EP2023/081708
Authority: WO
Inventors: Michael Scholl
Original assignee: Robert Bosch Gmbh
Priority date: 2022-11-14
Filing date: 2023-11-14
Publication date: 2024-05-23
Also published as: DE102022212030A1

Abstract

The invention relates to a method for determining a holding voltage nominal value (UHN) of a relay (112), which has at least two gates (201) and a signalling device (203), wherein the relay (112) can be switched by applying a voltage to the at least two gates (201) in a first switching position and by not applying voltage to the at least two gates (201) in a second switching position, wherein the signalling device (203) is configured to signal whether the relay (112) is in the first or the second switching position, the method comprising: switching the relay (112) into the first switching position by applying a voltage at a first voltage value (UP) to the at least two gates (201); reducing the value of the applied voltage until the signalling device (203) signals that the relay (112) is in the second switching position; and determining a value (UH1) of the applied voltage; determining the holding voltage nominal value (UHN) on the basis of the determined value (UH1) of the applied voltage. The invention also relates to a method for switching a relay (112) using a holding voltage nominal value (UHN) determined in this manner.

Description

Title

Method for determining a holding voltage rating of a relay, method for switching a relay using a holding voltage rating determined in this way, computing unit, arrangement and charging cable

The present invention relates to a method for determining a holding voltage rating of a relay and a method for switching a relay using a holding voltage rating determined in this way, as well as a computing unit, an arrangement, a charging cable and a computer program for carrying out the method.

Background of the invention

Battery-electric or hybrid vehicles can be charged at publicly accessible charging columns or charging stations or at a normal socket in private areas. There are two different principles underlying this.

On the one hand, charging can be done at permanently installed charging stations (charging columns or so-called wall boxes). For this purpose, either a charging cable is plugged into the charging station or the charging cable is already permanently connected to the charging station. Such a charging cable is also called a passive charging cable. It only serves to conduct the current from the charging station to the energy storage unit located in the vehicle.

On the other hand, charging can be done at so-called permanent power sockets. For this purpose, a charging cable with integrated control (e.g. an ICCB: In-Cable-Control-Box) is required. The control or the ICCB has the function of verifying the vehicle's readiness for charging via communication with the electric vehicle and switching on the power when required. and to permanently monitor the safe electrical connection to the electric vehicle and also switch it off in the event of a fault.

DE 102021 203 363 A1 shows a charging cable that can be used with appropriate adapters on charging stations and permanent power sockets. For this purpose, the charging cable has a bypass switch that loops an integrated control of the charging cable into the current path or not, depending on the adapter used. If, for example, an adapter for connecting to a household socket is connected to the charging cable and the control is activated using the bypass switch, the control can release the flow of current from the household socket to the vehicle by switching a pass-through switch.

Such pass switches can be designed as electromechanical relays. One or more of these relays can - as described in DE 102021 203 363 A1 - be arranged directly in the housing of a connector of the charging cable or an adapter of the charging cable. In other cases where an ICCB is provided in a line of the charging cable, the at least one relay can be arranged in the ICCB.

The use of electromagnetic relays for such pass-through switches may be prescribed by norms or industry standards, for example, so that semiconductor switches are not permitted.

The disadvantage of such electromagnetic relays is that they have a significant power requirement when they are activated.

Disclosure of the invention

According to the invention, a method for determining a holding voltage nominal value of a relay and a method for switching a relay using a holding voltage nominal value determined in this way as well as a computing unit, an arrangement, a charging cable and a computer program for carrying out the method with the features of the independent patent claims are proposed. Advantageous embodiments are the subject of the subclaims and the following description. With the invention, a holding voltage nominal value can be determined for each relay and used in operation, which is particularly energy-saving and gentle on materials.

In addition to the possible nominal operating voltage, standard electromechanical relays are usually characterized by the parameters pull-in voltage (minimum voltage required to pull the relay in), holding voltage rating (minimum voltage required to keep the relay switched) and drop-out voltage (voltage at which a relay safely drops out) in the data sheet by the manufacturer. These values are specified taking into account the possible manufacturing tolerances so that the relays supplied can all be safely operated at the specified values. This means that these values can be over-dimensioned for individual relays, possibly even for the majority of relays supplied, which can lead to unnecessarily high power consumption during operation.

The PWM method has been established for energy-saving operation. After switching on the relay, the control voltage is set to at least the nominal holding voltage value (from the data sheet) using PWM (pulse width modulation). A constant or temperature-dependent temperature reserve can be added. The reason for this is that the copper winding (the copper resistance has a positive temperature coefficient) of the relay coil heats up during operation and thus the coil current drops at a constant voltage. However, the coil current is the actually relevant value for the electromagnetic force in the relay that attracts the relay's armature. For temperature-critical applications, a current control can be provided in which the coil current is regulated, but this involves more circuitry and additional costs, since the coil current must be measured with a measuring device.

The data sheet value for the holding voltage rating specified by the relay manufacturer is given at a specified temperature and indicates the voltage required to hold the relay in the energized state. The specified value depends on the type and - as described above - is independent of whether the relay has a high or low coil resistance within the tolerance. However, current flows through relays with low coil resistance, a significantly higher current at the specified voltage is produced than by relays with high coil resistance. This results in an unnecessarily high power requirement, particularly for relays with low coil resistance and operation with the holding voltage rating specified in the data sheet.

There may therefore be a need to operate relays of a certain type safely on the one hand, so that no undesirable switching occurs due to insufficient coil current, and on the other hand to keep the energy consumption of the relay used in the voltage-energized state as low as possible. Furthermore, it should be possible to operate the relay in such an energy-saving mode as easily as possible and, if necessary, to take subsequent changes in the relay characteristics (e.g. due to aging effects, etc.) into account in the energy-saving control or to recognize in good time that a relay is reaching the end of its service life.

This need can be met by the proposed method, the computing unit, the arrangement, the charging cable and the computer program.

According to one aspect of the invention, a method is proposed for determining a holding voltage nominal value of a relay, in particular an electromagnetic relay, which has at least two control terminals and a signaling device, wherein the relay can be switched or moved or brought into a first switching position by applying a voltage to the at least two control terminals and into a second switching position by not applying a voltage to the at least two control terminals, wherein the signaling device is designed to signal whether the relay is in the first or the second switching position.

The method comprises switching the relay into the first switching position by applying a voltage with a first voltage value to the at least two control terminals. In other words, the first voltage value is large enough for the relay to switch. This can in particular be the above-mentioned pull-in voltage (e.g. as can be found in the data sheet). The method then comprises reducing the value of the applied Voltage until the signaling device signals that the relay is in the second switching position, determining a value of the applied voltage and determining the holding voltage rating as a function of the determined value of the applied voltage.

According to a further aspect of the invention, a method for switching such a relay as mentioned above is proposed, comprising switching the relay into the first switching position by applying a voltage with a first voltage value to the at least two control terminals. In other words, here too, the first voltage value is large enough for the relay to switch. This can in particular be the pull-in voltage mentioned above. The method then comprises setting, in particular reducing, the value of the applied voltage to a holding voltage value, which is determined or ascertained as a function of a holding voltage nominal value, which in turn has been determined according to a method according to the first aspect of the invention.

This advantageously makes it possible to operate a large number of relays of a certain type from a batch safely and reliably with a lower voltage than the holding voltage nominal value specified in the data sheet (in particular relays with a lower coil resistance compared to the high-impedance relays assumed in the data sheet). This advantageously makes it possible to permanently reduce the inherent energy requirement of the respective relay (and the device equipped with it) in a simple manner. The method can also advantageously be used automatically, e.g. in the manufacture of devices that have at least one such relay. In principle, it is also advantageously possible to use the method during operation of such a device and in this way to repeatedly determine the holding voltage nominal value and, for example, to adapt it over the service life of the relay. A further advantage is that such a change in the holding voltage nominal value can be used to determine whether and/or when a relay has reached or will reach the end of its service life and can no longer be operated safely (predictive maintenance).

Since the current strength in the coil is the decisive factor for the relay function, the method can be used to indirectly determine the individual Coil resistance can be determined or the holding voltage nominal value can be determined individually and reduced compared to the holding voltage nominal value specified in the data sheet, for example.

Another advantage of this is that a power supply unit required to operate the relay can be used with a lower power consumption compared to the situation in which the power supply unit is designed for the values specified in the relay's data sheet. In other words: it is advantageous that the power-side requirements for the voltage supply can be reduced. This can advantageously save installation space in a device in which the power supply unit for the relay is arranged, furthermore the waste heat of such a power supply unit is reduced and costs can be saved for an otherwise oversized power supply unit.

Within the scope of the invention, methods are proposed for determining the individual holding voltage rating of a relay and for using it for operation, thereby minimizing the power requirement during holding. Because a signaling device provided in the relay is used to determine the current switching position when determining the relay-specific or individual holding voltage rating, the invention can also be used very easily in the production of devices with such relays, in operation or in the field. With the aid of the signaling device, the individual holding voltage rating of a relay is determined, and with this individual holding voltage rating, the current or energy consumption for operating the relay in holding mode is further reduced beyond the state of the art.

Holding losses are reduced, which leads to lower power consumption of the circuit. The self-heating of the electronics can be reduced, which in turn results in lower energy consumption. This means less thermal stress, which advantageously increases reliability and service life. The lower self-heating also reduces the probability that an over-temperature protection device will intervene at increased ambient temperatures, since the lower self-heating of the The shutdown threshold is not reached. The power consumption and thus also CCh emissions are advantageously reduced. The power requirement is reduced, which can lead to savings in the voltage supply. The shutdown process is accelerated because less coil energy needs to be dissipated. This is particularly advantageous in the event of a fault, where rapid shutdown is desired.

The invention can be advantageously implemented with corresponding relays without additional circuitry, since all necessary components are usually available anyway.

It is advisable to determine the holding voltage nominal value as an individual parameterization during the production of a product or device containing the relay, such as a charging cable, since relatively constant and known temperatures prevail here. In one embodiment, the holding voltage nominal value can also be determined (alternatively or additionally) once or several times during the product runtime, provided the operating strategy allows this.

If the holding voltage rating is determined during production or after a relay has been installed in a product, such as a charging cable, it is also advantageous to detect a batch-dependent jump in the holding voltage rating at an early stage, which may indicate quality problems with the relays, which would otherwise only become apparent in the field.

In one embodiment, the determined holding voltage nominal value is stored in a memory device so that it is available during operation and can be used very easily without having to be determined anew each time. Such a memory device can be arranged in a computing unit that serves to control the relay. Such a memory device can also be arranged as a so-called electronic nameplate in or on the relay itself.

It may be intended to change the holding voltage rating occasionally, regularly, when one or more specific conditions occur and/or to be (re)determined on external instigation, e.g. by a user. In this way, temporal changes in the holding voltage nominal value, which can be caused in particular by age, can be taken into account. Possible embodiments include that a new determination is carried out depending on the age of the relay, and/or depending on an operating time (in particular the duration of current flowing through the coil winding), and/or depending on a number of switching operations (how often the relay is switched on), and/or depending on a load collective (e.g. power/energy transmitted by the relay, and/or integral of the current flowing through the coil winding over time) and/or depending on a temperature collective. Other possible embodiments include, in the event that the relay is part of a charging cable, that both plugs of the charging cable are plugged in or electrically connected to a mating plug (in the vehicle, charging station, a quality test bench in production, etc.).

In one embodiment, determining the holding voltage nominal value as a function of the specific value of the applied voltage includes determining the holding voltage nominal value as a function of the specific value of the applied voltage and a safety value (safety margin). In a simple embodiment, this can be an addition or multiplication. This can, for example, take temperature-dependent resistances, in particular also outside the relay, e.g. in supply lines, etc., into account. Such a safety value can also be used to compensate for temperature-dependent resistances in the relay, here in particular the coil winding. This can be useful, for example, when using a relay in a charging cable in order to compensate for expected heating during charging/discharging (= continuous operation of the relay) and/or increased ambient temperatures (e.g. in summer). For example, the safety value can be used to scale a holding voltage nominal value determined at a defined temperature (e.g. room temperature, e.g. at a production site) to a maximum permissible or expected temperature.

In one embodiment, determining the holding voltage rating in dependence on the determined value of the applied voltage comprises a plurality of determined values (at least two values) of the applied voltage to be offset against each other. For example, a mean or median of the multitude, or a maximum of the multitude can be determined. This can be used to take into account outliers in measurements or general measurement inaccuracies. This result can then be offset against the above-mentioned safety value.

In one embodiment, the value of the applied voltage is only set to the holding voltage value, in particular reduced, when the signaling device signals that the relay is in the first switching position. The signaling device can therefore also be used advantageously during operation to detect successful switching of the relay before the voltage is set to the holding voltage value, in particular reduced. This can improve the operation of the relay.

In one embodiment, the holding voltage value is equal to the holding voltage nominal value. Such an embodiment is very easy to implement. Changes in electrical resistance that may occur during operation, e.g. temperature-dependent, age-dependent or other changes, can be neglected here if the above-mentioned safety value is sufficiently large.

In an alternative embodiment, the holding voltage value is determined depending on the holding voltage nominal value and a temperature compensation value. This can include, for example, an addition or multiplication. The temperature compensation value can be constant and thus fulfill the function of the above-mentioned safety value and/or completely replace it. In other words, the replacement corresponds in particular to taking temperature changes into account not when determining the holding voltage nominal value, but only when determining the holding voltage value. However, the temperature compensation value is specified in particular depending on the temperature, e.g. as a function or characteristic curve, and serves to compensate for temperature-dependent (resistance) changes in the relay, in particular its coil winding. This leads to energy savings, since higher holding voltages (which mean a higher loss) are only necessary at high temperatures and the relay does not have to be operated permanently with the higher voltage for high temperatures. must. If a temperature sensor is available near the relay, this can be used to determine the temperature compensation value depending on the temperature. Alternatively, the current temperature in the relay or its coil winding can also be determined using a (calculation) model. If a temperature sensor is provided, it can be provided, for example, to calculate the temperature compensation value from a function depending on a temperature value determined by the temperature sensor or to read it from a characteristic map.

In one embodiment, the relay has at least two working connections that are electrically connected either in the first switching position or in the second switching position, and are not electrically connected in the other switching position. In other words, it can be a relay that conducts when activated, or a relay (or an opener) that does not conduct when activated. The invention can be used advantageously for both.

In one embodiment, applying a voltage to the at least two control terminals includes applying a pulse width modulated (PWM) voltage. However, it should be emphasized that any other adjustable voltage source can be used instead of a PWM control. However, a PWM control is advantageous because it makes it easy to determine the nominal holding voltage in the product and this is the established control method anyway. Using a PWM control, any (effective) voltage can be applied to the relay or the control terminals within the supply voltage range and the PWM resolution.

In one embodiment, the signaling device has at least two signal connections and is designed to signal whether the relay is in the first switching position by either electrically connecting the at least two signal connections or by not electrically connecting the at least two signal connections. For example, for safety-critical applications, such as charging cables, relays can be used that report the switching state by means of a signaling device in the form of a signal contact with two signal connections. This can also be done in Standards may require this to detect welded relay contacts, for example. This type of functionality is now used to particularly advantage in order to reduce the power consumption of the relay.

A computing unit according to the invention, e.g. a control device or a controller or an electronic circuit of a charging cable or another device which has at least one relay, is set up, in particular in terms of programming, to carry out a method according to the invention.

An arrangement according to the invention comprises (at least) one above-mentioned relay and a computing unit according to the invention.

A charging cable according to the invention is designed in particular for charging (and/or discharging) an energy storage device of an electric vehicle and has two plugs, a connecting line arranged between the two plugs, and an arrangement according to the invention.

In one embodiment, the computing unit is set up to only carry out a method according to the invention if both plugs of the charging cable are plugged in or electrically connected, e.g. with respective mating plugs, whereby this electrical connection can also be established during the manufacture of the charging cable, e.g. for testing purposes. This can in particular increase safety and prevent exposed contacts in the plug from being live due to the determination of the holding voltage nominal value or due to the switching of the relay, which could endanger the user or bystanders. In particular, the computing unit can be set up to only carry out a method according to the invention if the vehicle-side plug is plugged into a vehicle and/or if the infrastructure-side plug is plugged into a charging partner (energy source or energy sink), such as in particular a charging station, wall box, household socket or another vehicle. This state is particularly easy for the computing unit to recognize due to the signals then present, since it is set up for this anyway with a conventional charging cable. During the manufacture of the charging cable, for example, a test bench can be used into which the two plugs of the charging cable are plugged (or to which only the connectors of the plugs are connected) can simulate such a vehicle or an infrastructure connection. In this way, the holding voltage rating of at least one relay arranged in the charging cable or in a plug adapter can be determined during the manufacture of the charging cable or the plug adapter.

The implementation of a method according to the invention in the form of a computer program or computer program product with program code for carrying out all method steps is also advantageous, since this causes particularly low costs, in particular if an executing control device or an electronic circuit, etc. is also used for other tasks and is therefore already present. Finally, a machine-readable storage medium is provided with a computer program stored on it as described above. Suitable storage media or data carriers for providing the computer program are in particular magnetic, optical and electrical storage devices, such as hard disks, flash memories, EEPROMs, DVDs, etc. It is also possible to download a program via computer networks (Internet, intranet, etc.). Such a download can be wired or cable-bound or wireless (e.g. via a WLAN network, a 3G, 4G, 5G or 6G connection, etc.).

Further advantages and embodiments of the invention emerge from the description and the accompanying drawings.

The invention is illustrated schematically in the drawing using embodiments and is described below with reference to the drawing.

Short description of the drawings

Figure 1 shows an embodiment of a charging cable according to an embodiment of the invention.

Figure 2 shows a relay that can be used in the context of the invention in a schematic view. Figure 3 shows an exemplary profile of the relay control voltage, on the one hand, in a method for determining a holding voltage nominal value of a relay and, on the other hand, in a method for switching a relay according to embodiments of the invention.

Embodiment(s) of the invention

In Figure 1, a charging cable according to an embodiment of the invention is shown schematically and designated overall by 100. The charging cable 100 has a first, e.g. vehicle-side, plug 110, a connecting line or cable 120 and a second, e.g. infrastructure-side or consumer-side, plug 130. Such a charging cable 100 is used, for example, to connect a charging partner or a consumer (in the case of bidirectional charging) to a vehicle. The plugs 110, 130 can in particular be so-called CSS plugs or Type 2 plugs. The infrastructure-side plug can simply be, for example, a conventional household plug or SchukoO plug or a CEE plug, etc. The charging partner (not shown here) can in particular be a charging station, such as a charging column or so-called wall box, a household socket or a consumer (i.e. energy flows away from the vehicle), such as an energy storage device, the power grid, a lamp or a garden tool or the like, or another vehicle.

In the present example, a computing unit 111 is provided in the first plug 110, wherein this is arranged in particular in a housing of the plug 110 or is integrated into the housing. The computing unit 111 is programmed to carry out an embodiment of a method according to the invention, as is described below, for example, with reference to Figures 2 and 3. The computing unit 111 comprises in particular computing and storage means or storage devices or storage units, such as CPU, RAM, flash, etc. and preferably a power supply source, for example a battery or a rechargeable battery, wherein it can also be provided that the computing unit 111 is only supplied with energy when the charging cable 100 is connected, so that no internal charging cable energy supply is necessary. The computing unit 111 can be a distributed computing unit, which, for example, has several modules. These modules can all be arranged in a single one of the two connectors 110, 130, or can also be distributed in the cable 120 and/or the connectors 110, 130.

Furthermore, the charging cable has at least one relay 112 which, together with the computing unit 111, is part of an arrangement according to an embodiment of the invention. A relay 112 which can be used advantageously within the scope of the invention is shown schematically in Figure 2. The relay 112 has two control connections 201 and a signaling device 203, wherein the relay 112 can be switched to a first - here closed or conductive - switching position by applying a voltage to the two control connections 201 and to a second - here open or non-conductive - switching position by not applying a voltage to the two control connections 201. The relay 112 has two working connections 202 which are electrically connected in the first switching position and are not electrically connected in the second switching position. The signaling device 203 is designed to signal whether the relay is in the first or second switching position. For this purpose, the signaling device 203 has two signal connections 203a and is designed to signal whether the relay 112 is in the first switching position by - in the example shown - the two signal connections 203a not being electrically connected.

Figure 3 shows an exemplary curve of a voltage U applied to the control terminals 201 over time t according to embodiments of the invention, on the one hand in a method for determining a holding voltage nominal value UHN of a relay (between times t0 and t4) and on the other hand in a method for switching a relay (from t4).

A method for determining a holding voltage rating of a relay (such as relay 112 from Figs. 1 or 2) according to an embodiment of the invention begins at a time t0 by switching the relay into the first - here conductive - switching position by applying a voltage with a first voltage value UP to the two control terminals 201. The first voltage value UP can correspond to a rated voltage of the relay, but must correspond to at least a so-called pull-in voltage - this voltage can be taken from a data sheet of the corresponding relay, for example. A voltage level can be adjusted in particular by a PWM method in which a supply voltage is switched on and off at a certain duty cycle.

The first voltage value UP is present until a time h at which it can be assumed, for example based on empirical values or on a signal from the signaling device 203, that the switching process is completed.

At time h, the applied voltage U is initially reduced to a known holding voltage type value UHO - in particular taken from a data sheet. Such a holding voltage type value UHO is specified in particular by the manufacturer for all relays of a type and thus covers all tolerances (e.g. for coil resistance). It is therefore larger than necessary in many cases or for the majority of relays placed on the market.

Starting at time t2, the value of the applied voltage U is thus reduced until the signaling device 203 signals at time _t3 that the relay 112 is (again) in the second (here non-conductive) switching position. A measurement or direct monitoring of the current flowing through the relay is advantageously not necessary for this. The method also works in particular with open or unconnected working connections.

The associated value UHI of the applied voltage is determined and, depending on this, a relay-specific holding voltage nominal value UHN is determined, which can be stored in particular in a memory unit or in a storage device or in a storage means, in particular in a non-volatile memory (NVM), of the computing unit 111.

In the embodiment shown, determining the holding voltage nominal value UHN as a function of the determined value UHI of the applied voltage involves adding the determined value UHI of the applied voltage and a safety value (safety margin). This can be used to take temperature-dependent resistances into account, for example. The described method can be carried out, for example, during the manufacture of a device in which the relay 112 is arranged, e.g. during the manufacture of a charging cable 100 or a plug 110, 130 for a charging cable 100 or an ICCB of a charging cable 100. The method can be carried out at least once for each relay 112 in the device.

In regular operation after production, for example, the computing unit 111 can now read the individual holding voltage nominal value UHN from the storage unit or the storage device or the storage medium and operate the relay, for example, with this holding voltage nominal value UHN or with a holding voltage value depending on the holding voltage nominal value UHN.

In principle, the method can also be carried out during operation of the device in which the at least one relay 112 is arranged, e.g. repeatedly at regular intervals or depending on the situation, etc.

Figure 3 further shows a method for switching a relay 112 (such as the relay 112 from Figs. 1 or 2) according to an embodiment of the invention. This method for switching a relay 112 begins at a time t4 in which the relay 112 is switched to the first - here conductive - switching position by applying an electrical voltage with a first voltage value UP to the two control terminals 201. The first voltage value UP can correspond to a nominal voltage of the relay, but must correspond to at least a so-called pull-in voltage. A voltage level can be set in particular by a PWM method in which a supply voltage is switched on and off at a certain duty cycle.

The first voltage value UP is present until a time ts at which it can be assumed, for example based on empirical values or on a signal from the signaling device 203, that the switching process is completed.

At time ts, the applied voltage U is reduced to a holding voltage value UH, which depends on the previously determined

rated holding voltage UHN is determined, in this case corresponds to this. The Relay 112 remains in the first position even if the holding voltage value UH is smaller than the holding voltage type value UHO, but the energy consumption is lower. This means that a battery or

Battery life can be increased and on the other hand emissions (CO2 etc.) can be reduced.

Instead of the identity UH=UHN described here between the nominal holding voltage value UHN and the holding voltage value UH used, a temperature-dependent (T) relationship Un=f(UHN, T) can be selected, for example. The relationship can, for example, include a calculation with a temperature compensation value, for example an addition or multiplication. The temperature compensation value can be specified in particular as a function of the temperature, e.g. as a function or characteristic curve, and is used to compensate for temperature-dependent (resistance) changes in the relay, in particular its coil winding. The temperature compensation value can also be constant and thus fulfill the function of the safety value mentioned above and/or replace it completely. In other words, the replacement corresponds in particular to taking temperature changes into account not when determining the nominal holding voltage value UHN from UHI, but only when determining the holding voltage value UH from UHN.

If a temperature sensor is available near the relay, this can be used to determine the temperature compensation value depending on the temperature. Alternatively, the current temperature in the relay or its coil winding can also be determined using a (calculation) model. If a temperature sensor is provided, it can be provided, for example, to calculate the temperature compensation value from a function or read it from a characteristic map depending on a temperature value determined by the temperature sensor.

Claims

Expectations

1. Method for determining a holding voltage nominal value (UHN) of a relay (112) which has at least two control terminals (201) and a signaling device (203), wherein the relay (112) can be switched into a first switching position by applying a voltage to the at least two control terminals (201) and into a second switching position by not applying a voltage to the at least two control terminals (201), wherein the signaling device (203) is designed to signal whether the relay (112) is in the first or the second switching position, comprising the following steps:

-- Switching the relay (112) into the first switching position by applying a voltage with a first voltage value (UP) to the at least two control terminals (201),

-- reducing the value of the applied voltage until the signaling device (203) signals that the relay (112) is in the second switching position and determining a value (UHI) of the applied voltage, -- determining the holding voltage rating (UHN) as a function of the determined value (UHI) of the applied voltage.

2. The method of claim 1, further comprising storing the determined holding voltage rating (UHN) in a storage device.

3. Method according to one of the preceding claims, wherein determining the holding voltage rating (UHN) as a function of the determined value (UHI) of the applied voltage comprises determining the holding voltage rating (UHN) as a function of the determined value (UHI) of the applied voltage and a safety value.

4. Method for switching a relay (112) having at least two control terminals (201) and a signaling device (203), wherein the relay (112) can be switched into a first switching position by applying a voltage to the at least two control terminals (201) and into a second switching position by not applying a voltage to the at least two control terminals (201), wherein the signaling device (203) is designed to signal whether the relay (112) is in the first or the second switching position, comprising the following steps:

-- Adjusting, in particular reducing, the value of the applied voltage to a holding voltage value (UH) which is determined as a function of a holding voltage nominal value (UHN), wherein the holding voltage nominal value (UHN) has been determined according to a method according to one of the preceding claims.

5. Method according to claim 4, wherein the value of the applied voltage is set, in particular reduced, to the holding voltage value (UH) when the signaling device (203) signals that the relay (112) is in the first switching position.

6. The method according to claim 4 or 5, wherein the holding voltage value (UH) is the holding voltage nominal value (UHN), or wherein the holding voltage value (UH) is determined as a function of the holding voltage nominal value (UHN) and a temperature compensation value.

7. Method according to one of the preceding claims, wherein the relay (112) has at least two working terminals (202) which are electrically connected either in the first switching position or in the second switching position, and are not electrically connected in the other switching position.

8. Method according to one of the preceding claims, wherein the application of a voltage to the at least two Control connections (201) comprises the application of a pulse width modulated voltage. Method according to one of the preceding claims, wherein the signaling device (203) has at least two signal connections (203a) and is designed to signal whether the relay (112) is in the first switching position by either electrically connecting the at least two signal connections (203a) or by not electrically connecting the at least two signal connections (203a). Computing unit (111) which is designed to carry out all method steps of a method according to one of the preceding claims. Arrangement, the arrangement comprising:

-- a relay (112),

-- a computing unit (111) according to the preceding claim, wherein the relay (112) has at least two control connections (201) and a signaling device (203), wherein the relay (112) can be switched into a first switching position by applying a voltage to the at least two control connections (201) and into a second switching position by not applying a voltage to the at least two control connections (201), wherein the signaling device (203) is designed to signal whether the relay (112) is in the first or the second switching position. Charging cable (100), in particular designed for charging an energy storage device of an electric vehicle, the charging cable comprising: -- two plugs (110, 130),

-- a connecting line (120) arranged between the two plugs, and

-- an arrangement (111, 112) according to the preceding claim. Charging cable (100) according to the preceding claim, wherein the computing unit (110) is set up to carry out the method according to one of claims 1 to 9 only when both plugs (110, 130) of the charging cable (100) are plugged in. Computer program which causes a computing unit to carry out all method steps of a method according to one of claims 1 to 9 when it is executed on the computing unit. Machine-readable storage medium with a computer program according to the preceding claim stored thereon.