Measuring device for measuring a current provided for supplying energy

Abstract

The invention relates to a measuring device for measuring a current provided for supplying energy, comprising a measuring circuit having two connection contacts (X3, X4; X5, X6) via which a current (I1) provided for supplying energy is conducted through the measuring circuit via a current input and current output in order to measure said current, wherein the measuring circuit is equipped with a voltage limiter (DX) and comprises a shunt (RX), characterised in that adjacent to the connection contacts (X3, X4; X5, X6) first the shunt (RX) is arranged as the first component of the measuring circuit and electrically interconnects the current input and current output, in particular such that as a result the signal input of the measuring circuit has a low-ohmic design. The invention also relates to a charging station which has a measuring device according to one of claims 1 to 8 and a control unit for controlling a process of charging with electric current.

Description

[0001] Measuring device for measuring a current intended for energy supply

[0002] Description

[0003] The invention relates to a measuring device for measuring a current intended for energy supply and to a charging station with such a measuring device.

[0004] Such a measuring device is typically designed to measure the current supplied via an electrical line, whereby the current must usually flow through the measuring device for measurement and recording. If a voltage is also detected in this context, the electrical energy supplied via the electrical line for power supply can thus also be recorded or measured.

[0005] Such a measuring device is therefore often used in an electricity metering unit, often referred to as an electricity meter or power meter, which records the electrical energy transmitted at a metering point. The metering point can be located between a power grid and a household or industrial facility, for example, but can also be between two power grids. The use of the extracted energy is sometimes referred to as energy consumption. In this sense, it is also an energy meter.

[0006] Typically, such measuring devices are also installed on a mounting plate (e.g., in a domestic installation) or using DIN rail systems. If measurements are taken in accordance with MID, i.e., in accordance with the EU Measuring Instruments Directive (Measuring Instruments Directive) applicable at the time of registration, i.e., Directive 2014 / 32 / EU (effective April 20, 2016), the measuring device must also be regularly inspected / replaced. This entails increased effort.

[0007] An ever-increasing area of ​​application for such measuring devices can be found, for example, in various charging stations, particularly in the wake of growing e-mobility, such as in the wall boxes or other e-mobility charging stations required for this purpose. For example, AC (alternating current) charging stations typically achieve charging capacities of up to 22 kW, whereas DC (direct current) charging stations can achieve significantly higher charging capacities of up to 500 kW. Short circuits can be particularly problematic for such measuring devices, as they subsequently result in significantly larger short-circuit currents at the measuring device, as well as short-term overcurrents caused by other factors.

[0008] The object of the invention is to create an overload-capable measuring device, in particular to create an overload-capable measuring device suitable for high currents such as those encountered during the charging process using charging stations in the field of e-mobility.

[0009] The solution to the problem of creating an overload-capable measuring device is represented according to the invention by a measuring device with the features according to claim 1 and by a charging station with the features according to claim 9.

[0010] Appropriate refinements and further developments are the subject of the respective further dependent claims.

[0011] The invention proposes a measuring device for measuring a current intended for energy supply, which comprises a measuring circuit with two connection contacts, via which a current intended for energy supply can be or is then conducted through the measuring circuit for its measurement via a current input and current output, wherein the measuring circuit is equipped with a voltage limiter and comprises a shunt. The measuring device according to the solution of the invention is characterized in particular in that the shunt is arranged adjacent to the connection contacts as the first component of the measuring circuit and electrically connects the current input and current output, so that the signal input of the measuring circuit is expediently designed with low resistance.

[0012] If the shunt is connected in parallel with the rest of the measuring circuit, a significant portion of the current can be diverted or the measuring range of the measuring device can be expanded without causing damage. This has the advantage that even high nominal currents, especially high nominal DC charging currents, can be measured. Depending on the shunt's dimensions, only a reduced portion of the current is conducted through the rest of the measuring circuit, while at the same time, a potentially higher current, particularly short-circuit or short-time current, can be permitted without causing damage. Voltage limitation, in turn, can protect the rest of the measuring circuit connected in parallel with the shunt from extreme overcurrent.

[0013] As voltage limiters, a suppressor diode, an active switchable overvoltage limiter, a spark gap or anti-parallel diodes, in particular two anti-parallel diodes as part of the measuring circuit have proven particularly useful.

[0014] If not only this voltage limitation is connected in parallel to the shunt, but at least one resistor is connected in series with the voltage limitation, in particular a resistor is connected in series to the current input or current output between the shunt and the voltage limitation, the currents fed to the voltage limitation can be limited again and thus in particular the dimensioning, e.g. the size, of a respective voltage limitation can be reduced.

[0015] According to a particularly expedient embodiment, the measuring circuit of a measuring device according to the invention further comprises two, ie in particular several, circuit parts connected in series in a cascade manner, in which the voltage limitation connected in parallel to the shunt and in series with at least one resistor forms a first circuit part of these two circuit parts and the second circuit part has a further voltage limitation connected in parallel to the shunt and in series with at least one further resistor.

[0016] This can result in a gradual signal attenuation and consequently a gradual limitation of the signal values ​​present in the measuring circuit, ie in particular current and / or voltage values.

[0017] In practical implementation, the measuring device also has a measuring transformer arranged downstream of the measuring circuit, which converts a measuring signal representing the current provided for the energy supply into a low-voltage signal, wherein the measuring circuit and the measuring transformer are galvanically isolated in a practical design.

[0018] In order to minimise the risk to the environment, particularly in the event of a short circuit and / or a possible or expected explosion, through open live parts and / or to minimise the damage to the environment by bridging insulation gaps and thus also to minimise the damage to any user, the encapsulation of the measuring transformer within a housing that excludes the measuring circuit and / or the encapsulation of the measuring circuit wholly or partially within a housing that excludes the measuring transformer is provided.

[0019] In addition to or as an alternative to the encapsulation shown above, the measuring circuit can also be encapsulated separately within a housing in a suitable design, whereby the connection contacts are accessible from outside this housing for the purpose of connecting electrical cables.

[0020] The invention therefore also proposes a charging station with a measuring device designed according to the above statements, which expediently also has a control device for controlling a charging process with electrical current.

[0021] Further features and advantages of the invention will become apparent from the following description of some preferred embodiments with reference to the accompanying drawings, in which:

[0022] Fig. 1 shows a highly simplified circuit diagram of a possible internal electrical wiring structure of a charging station connected to a vehicle according to the invention, together with a measuring device with a first embodiment of a measuring circuit according to the invention for carrying out a charging process with electrical current;

[0023] Fig. 2 shows a highly simplified circuit diagram of a possible internal electrical wiring structure of a measuring device with a further embodiment of a measuring circuit according to the invention, which can be or is used within a charging column that can be connected or is connected to a vehicle for carrying out a charging process with electrical current.

[0024] Fig. 3A shows a greatly simplified further embodiment of a measuring circuit according to the invention;

[0025] Fig. 3B shows a highly simplified first embodiment of a measuring circuit according to the invention with two circuit parts connected in series in a cascade manner;

[0026] Fig. 30 shows a highly simplified second embodiment of a measuring circuit according to the invention with two circuit components connected in series in a cascade; and Fig. 4 shows a highly simplified several embodiments of different encapsulation variants within the measuring device according to the invention.

[0027] A measuring device for measuring a current provided for the energy supply according to the invention is described in more detail below, wherein the measuring device comprises a measuring circuit with, for example, two connection contacts X3, X4, via which a current 11 provided for the energy supply is passed through the measuring circuit for its measurement via a current input and current output, is equipped with a voltage limiter DX and comprises a shunt RX, which is arranged adjacent to the connection contacts X3, X4 as the first component of the measuring circuit and electrically connects the current input and current output. A charging station is also described in more detail which, within the scope of the invention, has such a measuring device and a control device for controlling a charging process with electrical current.

[0028] First, reference is made to Fig. 1, which shows a highly simplified circuit diagram of a possible internal electrical wiring structure of a charging column according to the invention connected to a vehicle, together with a measuring device with a first embodiment of a measuring circuit according to the invention for carrying out a charging process with electrical current.

[0029] Such a charging station has, as shown in the charging station sketched in Fig. 1 and designated there with controller 1, a control device for controlling a charging process with electrical current. In particular, since charging stations, in particular wall boxes or other e-mobility charging stations, such as the charging station sketched in Fig., are usually part of a larger system, the control device of the charging station can, as can be seen in Fig. 1, be connected to another, higher-level controller, with the connection expediently being made via a bus, via which extensive data can then also take place. Such a bus can, for example, be set up as a CAN bus or Profibus, although other suitable buses are certainly known to those skilled in the art. According to or.By connecting the charging station to a vehicle, the control device of the charging station is also known to exchange data with a control device located in the vehicle, designated as controller 2 in Fig. 1. This data exchange can also take place via a bus, as is conventional.

[0030] Furthermore, as outlined in Fig. 1, part of the charging station is usually a charge controller which is connected to a power source, in particular to an alternating or three-phase network, and which regulates the charging current under the control of the controller 1, e.g. via the control line marked ST2 in Fig. 1. Such a charge controller can, for example, also comprise an analog-to-digital converter or digital-to-analog converter, depending on whether an alternating current or direct current source is used as the power source and whether the charging current is or should be alternating current (AC) or direct current (DC). If, as shown in Fig. 1, an alternating current or three-phase source is used as the power source and a direct current is used as the charging current, which is then accordingly conducted via a DC network, the charge controller therefore expediently also comprises an analog-to-digital converter, also referred to below as ADC.

[0031] At least a portion of the direct current provided or made available by the charging station, in particular by its charge controller, via the line marked L+ on the charge controller as shown in Fig. 1 is used as charging current for an energy storage device provided in the vehicle and thus, according to the example outlined, for supplying energy to the vehicle.

[0032] For measuring a current 11 intended for energy supply, the charging station outlined in Fig. 1 comprises a possible embodiment of a measuring device, referred to as an energy meter in Fig. 1 for the sake of clarity, with a first embodiment of a measuring circuit according to the invention. For measuring the current 11 intended for energy supply, at least two connection contacts X3 and X4 are provided on the measuring device, via which this current 11 intended for energy supply can be or is passed through a measuring circuit of the measuring device for its measurement via a current input and current output.

[0033] 1, the current 11 provided for the energy supply is thus first passed through the measuring circuit of the measuring device before it is fed wholly or partly, according to the embodiment according to Fig. 1 via section D, to the vehicle as charging current for the energy storage device provided there. The circuit according to the embodiment according to Fig. 1 is ultimately closed via the line marked L-. By means of the measuring circuit of the measuring device, at least one measuring signal I representing the current provided for the energy supply can then be made available, which signal can, however, be converted again into a low-voltage signal by means of a measuring transformer downstream of the measuring circuit (cf. all Figs. 1 to 4), in particular for monitoring and evaluating the energy supply. According to the embodiments shown in Figs.In the exemplary embodiments outlined, in which direct current is used as the charging current, a digital-to-digital converter is therefore preferably used for this purpose.

[0034] As further shown in the embodiment sketched in Fig. 1, the measuring circuit of the measuring device contains a voltage limiter DX and a shunt RX or the measuring circuit is also made up of these components, among others. In particular, as shown, it can be seen that the shunt RX is arranged adjacent to the connection contacts X3 and X4 as the first component of the measuring circuit and electrically connects the current input and current output. As a result, the signal input of the measuring circuit can preferably be designed with low impedance and thus, in particular due to this low impedance of the signal input, the measuring device can also be advantageously used within the framework of or in the field of e-mobility applications as a suitable overload-capable measuring device.Depending on the shunt's dimensions, only a reduced current can be conducted through the rest of the measuring circuit, while simultaneously allowing a potentially higher current, particularly short-circuit or short-time current, without causing damage. Voltage limitation, in turn, can protect the rest of the measuring circuit connected in parallel with the shunt from extreme overcurrents. This can, in particular, protect the voltage measurement path marked U3 in the event of an extreme overcurrent. Providing a resistance value for the shunt RX in the mOhm range or lower has proven particularly useful.

[0035] If not only this voltage limiter DX is connected in parallel to the shunt RX, but at least one resistor R3 and / or R4 is connected in series with the voltage limiter DX, which also absorbs voltage in the event of an overload, in particular a resistor is connected in series to the current input or current output between the shunt RX and the voltage limiter DX, the current fed to the voltage limiter DX can be limited again and thus, in particular, the dimensioning, e.g. the size, of a respective voltage limiter can be reduced. As outlined in Fig. 1, a suppressor diode as a component of the measuring circuit has proven particularly useful as the voltage limiter DX. Alternatively, the use of two anti-parallel diodes, an active, switchable overvoltage limiter or spark gap is also possible. The activation of such an active, switchable voltage limiter DX can, for example,by means of a further circuit accommodated by the charging station or the measuring device, e.g. in the form of a processor, in the embodiment sketched in Fig. 1, e.g. by the microprocessor pp sketched there. Accordingly, in the embodiment sketched in Fig. 2 of a further possible internal electrical circuit structure of a measuring device, which can be or is used within a charging column connectable or connected to a vehicle for carrying out a charging process with electrical current, the voltage limitation DX is shown in dashed lines as a box. Also, as in particular in Fig.2, the energy measuring device according to the invention not only comprises one measuring circuit, but can also have one or more further measuring circuits, each with two connection contacts X5 and X6, via which a further current I2 provided for the energy supply is then conducted through the further measuring circuit. In addition to measuring a current provided for the energy supply, a voltage U1 present therein is also expediently determined, as further sketched in the embodiments according to Figs. 1 and 2. A measuring transformer is then preferably arranged downstream of a measuring circuit provided for this purpose, which in this case then converts a measuring signal U representing the voltage U1 present therein into a low-voltage signal.

[0036] This voltage surge at the RX caused by extreme overcurrent, especially large short-circuit current, can only be stopped by a suitable power cutoff. Since the power cutoff can also be very slow in terms of time, additional components may be necessary, such as the one outlined in Fig. 1, a switch K2 arranged in the vehicle to protect the energy storage device, in particular a so-called pyroswitch, and / or a fuse S1 upstream in the charging station.

[0037] These aforementioned components generally have a response time of approximately 100ps to approximately 5ms. In addition or alternatively, if current monitoring takes place by means of a monitoring module IDC1 arranged in the charging station, as outlined in the embodiment according to Fig. 1, the corresponding shutdown of a switch K1 arranged in the charging station for "current shutdown" can also be initiated. This can result in response times of between 10 and 30ms. If a charge controller is used, as outlined in Fig. 1, for example, the shutdown time can generally be shortened again to a shutdown time in the ps range, because the power electronics internal to the charge controller can then be deactivated.

[0038] Furthermore, in order to optimally cover the measuring range of the measuring device, particularly the measuring transformer included in the practical design for low-voltage conversion, the shunt RX and, if present, the resistor R3 and / or R4 connected in series with the voltage limiter DX are preferably designed so that a nominal current plus an overcurrent factor, e.g., a factor of magnitude 10 or greater, can be measured. The overcurrent factor can also be based, for example, on a protective fuse arranged in the charging station for current limitation or shutdown, such as the fuse S1 shown in Fig. 1.

[0039] If, for example, the measuring device according to the invention is to be used to measure nominal charging currents of, for example, 500A, i.e. the (nominal) current I1 provided for the energy supply is 500A, and at the same time a possible short-circuit current of 70kA, i.e. the (short-circuit) current I1 provided for the energy supply is 70kA, can be permitted without destruction, a possible suitable dimensioning, in particular based on an embodiment according to Fig. 1, 2 or 3, would be to use a voltage limiter which responds at approx. 1V and to provide a resistance value of approx. 0.1 mOhm for the shunt RX. In this case, given the (nominal) current I1 of 500A, the voltage U2 dropped across the shunt RX would be approx. 50mV. Correspondingly, approx. 50mV would drop across the rest of the measuring circuit connected in parallel to the shunt.In this case, the voltage limiter would therefore not yet respond, and approximately 50 mV could be present or dropped across the voltage measuring path U3. However, if a short-circuit current of 70 kA is present, the voltage drop across shunt RX would therefore be approximately 7 V. This would also result in approximately 7 V dropping across the rest of the measuring circuit connected in parallel with the shunt. In this case, the voltage limiter would respond at approximately 1 V. In order to ensure that the short-circuit current of 70 kA can still be permitted without causing destruction, it must therefore be possible to additionally absorb approximately 6 V via resistors R3 and R4 in a practical design. In the case of this example requirement, a total resistance value of approximately 1000 ohms would therefore be required for resistors R3 and R4.

[0040] In principle, the voltage present or dropped across the voltage measuring path of the measuring device can also be further reduced by providing circuit components connected in series in a cascade manner in the measuring device according to the invention, as is sketched, for example, in the embodiments according to Figs. 3B, 3C and 4.

[0041] Thus, the voltage limiter DX, connected in parallel to the shunt RX and in series with at least one resistor, can form a first circuit section of two circuit sections connected in series in accordance with the invention, and the second circuit section can have a further voltage limiter DX2 connected in parallel to the shunt RX and in series with at least one further resistor R3', R4'. Such embodiments can be seen, for example, in Figs. 3B and 3C. The voltage ultimately present or dropped across the voltage measurement path of the measuring device is designated U3' in Figs. 3B and 3C.

[0042] In detail, Fig. 3B shows, for example, an embodiment in which the first circuit part Y1' outlined therein comprises the shunt RX and, in parallel thereto, the voltage limiter DX connected in series with at least one resistor R3, R4, and a second circuit part Y2 comprises a further voltage limiter DX2 connected in parallel to the shunt DX and in series with at least one further resistor R3', R4'. As an alternative to the embodiment according to Fig. 3B, Fig. 3C outlines an embodiment in which the voltage limiter DX connected in series with the at least one resistor R3, R4 in parallel to the shunt RX forms a first circuit part Y1 of these two circuit parts, and the second circuit part Y2 has a further voltage limiter DX2 connected in series with at least one further resistor R3', R3' in parallel to the shunt RX.

[0043] The first circuit section Y1 or Y1', which is connected to the shunt RX or is formed together with it, thus limits the voltage U3 to a first level in the event of an overload. The second circuit section Y2 then attenuates the voltage U3 applied there at the input by a further amount in a further stage, whereby further current limitation is achieved by the resistors R3' and R4', thus resulting in a lower second level at the voltage U3' compared to the voltage U3. Since the voltage U3' is thus further reduced at the voltage limiter DX2, its dimensions can also be designed smaller than the voltage limiter DX due to the cascade structure.

[0044] Referring to an embodiment as sketched in Fig. 1, a causal short-circuit fault for an overcurrent acting on the measuring device, ie for a very large current value I1 and consequently for a large value LI3 / DX, assuming that the switch K1 is switched on, can occur essentially in each of the sections A, B, C, D, E and F.

[0045] If the causal fault lies in section A or B, the energy from the energy storage device is routed via the RX shunt. If the causal fault lies in section C, the grid or the energy storage device is short-circuited via the RX shunt. If the causal fault lies in section D, E, or F, the energy storage device will be primarily discharged at the short-circuit point, with additional current from the charging station being supplied to this point via the RX shunt. If switch K1 is off, however, the current flow can only be maintained by the energy storage device in the vehicle, in which case sections B and C are supplied via the RX shunt and are particularly critical.

[0046] In order to minimize the risk to the environment in the event of a short circuit, the resulting destruction, or even a potentially expected explosion, and thus to protect all users / persons / operators from danger, various measures have been integrated into the measuring device according to the invention in a practical further development. Since the hazards can be very diverse, e.g. hazards from flying parts, hazards from open live parts and / or hazards, including indirect hazards, from parts that internally bridge insulation gaps to 24V, complementary but also alternative measures are preferably provided. Hazards and their risk assessment are defined in the IEC 61010 standard or the corresponding EN 61010, in particular IEC 61010-1:2010 or.EN 61010-1:2010, whereby the invention is of course based on the standard applicable at the time of application.

[0047] Furthermore, printed circuit boards have often been used to fulfill wiring tasks for current measurement inputs. However, this also entails significant disadvantages with regard to short-circuit loading. A short-circuit load on a printed circuit board can cause, in particular, delamination of the layers, complete separation of the individual layers, so that excess pressure from the interior is transferred to the surface, complete melting of conductive layers, especially copper layers, the formation of a plasma cloud, uncontrolled arcing, and / or extreme overpressure in the affected circuit area, to name just a few of the possible effects.

[0048] In particular, it must be ensured that no insulation gaps are compromised by the effects of a short circuit. Consequently, no components, especially those exposed to increased mechanical and electrical stress, may be blown off and subsequently form a bridge to the low-voltage area, i.e., in particular, bridge section G as shown in Figures 1 and 2. Furthermore, in the event of a measuring device or measuring device area being destroyed by a short circuit, no live parts may be freely accessible to the user / person / operator.

[0049] According to a first preferred development, at least the measuring circuit and the measuring transformer are galvanically isolated from each other, as outlined in all figures and designated by the reference symbol GT in Fig. 1.

[0050] The areas bordered by dashed lines in particular in Figs. 2, 3B, 3C and 4, cf. in particular those marked Y1, YT Y2, Y3, Y4, Y5, Y6, represent various expedient possibilities for mechanical encapsulation. If, for example, the measuring transformer is encapsulated within a housing that excludes the measuring circuit and / or the measuring circuit is completely or partially encapsulated within a housing that excludes the measuring transformer, this can also prevent live parts from entering the 24V area and bridging section G. In addition or alternatively, a further preferred embodiment provides for the measuring circuit to be encapsulated separately within at least one housing, the connection contacts being accessible from outside this housing for the purpose of connecting electrical lines.

Claims

1. Measuring device for measuring a current intended for energy supply, comprising a measuring circuit with two connection contacts (X3, X4; X5, X6), via which a current intended for energy supply (11) is guided through the measuring circuit for its measurement via a current input and current output, wherein the measuring circuit is equipped with a voltage limiter (DX) and comprises a shunt (RX), characterized in that adjacent to the connection contacts (X3, X4; X5, X6) the shunt (RX) is arranged as the first component of the measuring circuit and electrically connects the current input and current output to one another, in particular so that the signal input of the measuring circuit is designed to be low-impedance.

2. Measuring device according to claim 1, wherein a suppressor diode, two anti-parallel diodes, an active switchable overvoltage limiter or a spark gap is part of the measuring circuit for voltage limitation (DX).

3. Measuring device according to claim 1 or 2, wherein the voltage limiter (DX) is connected in series with at least one resistor (R3, R4) in parallel to the shunt (RX), in particular a resistor (R3, R4) is connected between the shunt and the voltage limiter in series with the current input or current output.

4. Measuring device according to claim 3, wherein the measuring circuit comprises two circuit parts (Y1, Y2; Y1, Y2) connected in series in a cascade manner, in which the voltage limiter (DX) connected in parallel to the shunt (RX) together with the resistors (R3, R4) connected between the shunt (RX) and the voltage limiter (DX) forms a first circuit part (Y1') of these two circuit parts, and the second circuit part (Y2) comprises a further voltage limiter (DX2) connected in parallel to the shunt (RX) and two further resistors (R3', R4') connected between the two voltage limiters (DX, DX2). of which one is connected in series to the current input and one in series to the current output, or in which the voltage limiter (DX) connected in series with the at least one resistor (R3, R4) in parallel with the shunt (RX) forms a first circuit part (Y1) of these two circuit parts and the second circuit part (Y2) has a further voltage limiter (DX2) connected in series with at least one further resistor (R3', R4') in parallel with the shunt (RX).

5. Measuring device according to one of claims 1 to 4, wherein the measuring circuit is followed by a measuring transformer which converts a measuring signal (I) representing the current provided for the energy supply into a low-voltage signal.

6. Measuring device according to claim 5, wherein the measuring circuit and the measuring transducer are galvanically isolated.

7. Measuring device according to one of claims 5 or 6, wherein the measuring transducer is encapsulated within a housing excluding the measuring circuit and / or the measuring circuit is wholly or partially encapsulated within a housing excluding the measuring transducer.

8. Measuring device according to one of the preceding claims, wherein the measuring circuit is separately encapsulated within a housing and the connection contacts are accessible from outside this housing for the purpose of connecting electrical lines.

9. Charging station comprising a measuring device according to one of claims 1 to 8 and a control device for controlling a charging process with electrical current.

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