EP4728541A1

EP4728541A1 - Switching device, circuit breaker, arrangement and method for operating a switching device

Info

Publication number: EP4728541A1
Application number: EP24737094.3A
Authority: EP
Inventors: Lothar Jagusch
Original assignee: Eaton Intelligent Power Ltd
Current assignee: Eaton Intelligent Power Ltd
Priority date: 2023-07-06
Filing date: 2024-06-27
Publication date: 2026-04-22
Also published as: WO2025008266A1; CN121336278A

Abstract

In embodiment, the switching device (1) comprises a switching unit (2) with electrical contact surfaces (21, 22), a voltage metering circuit system (3), a current sensor (4) and a calculation unit (5). The voltage metering circuit system (3) is connected to a first end (23) and second end (24) of the switching unit (2) and configured to measure a voltage drop (10) across the switching unit (2). The current sensor (4) is connected to the first end (23) or the second end (24) of the switching unit (2) and is configured to measure a current (11). The calculation unit (5) is connected to the voltage metering circuit system (3) and the current sensor (4) and is configured to determine a contact resistance (6) of the contact surfaces (21, 22) of the switching unit (2) by means of the voltage drop (10) and the current (11). The calculation unit (5) is configured to determine a contact wear of the contact surfaces (21, 22) based on the contact resistance (6) of the contact surfaces (21, 22).

Description

Switching device , circuit breaker, arrangement and method for operating a switching device

A switching device is speci fied . Furthermore , a circuit breaker, an arrangement and a method for operating a switching device are speci fied .

One problem to be solved is , inter alia, to speci fy an improved switching device with a particular long li fespan . Other problems to be solved are , inter alia, to speci fy an improved circuit breaker comprising such a switching device , an arrangement comprising such a switching device and a method for operating such a switching device .

These problems are solved, inter alia, by a switching device comprising the features of independent claim 1 , by a circuit breaker comprising the features of claim 9 , by an arrangement comprising the features of claim 11 , and by a method comprising the features of claim 14 . Advantageous embodiments and further developments are the subj ect-matter of the respective dependent patent claims .

In at least one embodiment , the switching device comprises a switching unit with electrical contact surfaces , a voltage metering circuit system, a current sensor and a calculation unit . The voltage metering system is connected to a first end and a second end of the switching unit and is configured to measure a voltage drop across the switching unit . The current sensor is connected to the first end or the second end of the switching unit and is configured to measure a current . The calculation unit is connected to the voltage metering circuit and the current sensor and is configured to determine a contact resistance of the contact surfaces of the switching unit by means of the voltage drop and the current . The calculation unit is configured to determine a contact wear of the contact surfaces based on the contact resistance of the contact surfaces .

In particular, the switching unit comprises two electrical contact surfaces , wherein a first electrical contact surface is a moveable contact surface and a second electrical contact surface is a fixed contact surface . By bringing the movable contact surface in contact with the fixed contact surface , the switching unit , and hence also the switching device , may be closed and a main circuit , in which the switching device may be integrated, may be closed . The switching unit and/or the switching device may be an electromechanical switching unit and/or an electromechanical switching device .

For example , the contact surfaces comprise a metal and in particular one of the following materials or a combination thereof : silver (Ag) , nickel (Ni ) , copper ( Cu) , cadmium ( Cd) , cadmium oxide ( CdO) .

In particular, the first end of the switching unit is electrically conductively connected to the first electrical contact surface and the second end of the switching unit is electrically conductively connected to the second electrical contact surface . That is , by closing the switching unit , a voltage drop across the switching unit may be measured . The voltage drop mainly occurs due to the contact resistance between the electrical contact surfaces . For example , due to altering, degeneration, mechanical deformation, uneven and/or inhomogeneous contact surfaces , the contact resistance may change over time . By measuring the voltage drop across the switching unit , the change of contact resistance and hence the altering or contact wear of the contact surfaces may be monitored .

The calculation unit may receive the voltage drop obtained by the voltage metering circuit system and the current obtained by the current sensor as inputs and calculate the contact resistance of the contact surfaces . From the contact resistance the condition of the contact surfaces may be deduced . I f , for example a plurality of contact resistances gathered over time is known, an altering process of the contact surfaces may be monitored . This may indicate at what point in time the contact surfaces , i . e . the switching unit , need to be replaced .

The switching device described here is based on the following technical considerations . Contact surfaces of electromechanical switching devices like circuit breakers , motor protection devices and the like are degrading over time , thus reducing their switching capability . For predictive maintenance it is helpful to know the condition the contacts are in, in particular a contact wear . In modern switching devices this is carried out by comparably rough calculations , for example based on the number of switching operations and the currents flowing at these operations .

However, such a procedure can only be an estimation with huge tolerances , especially on the negative side . When calculating the contact li fe left , worst case wear must be considered . Consequently, devices are typically replaced much earlier than necessary for security reasons and because exact data regarding the contact wear are not known . A better contact wear detection may thus generally result in longer li fetime of the devices , fewer maintenance intervals for the installation and thus lower cost .

For example , i f the contact surfaces are formed with silver, the contact resistance may rise from about 0 . 25 mQ to 0 . 7 mQ after about 300 , 000 switching events i f the switching unit is installed in a main circuit carrying a current of 10 A and a DC voltage of 200 V at 50 Hz . Under the same conditions the contact resistance of contact surfaces formed with AgNi may rise from about 0 . 3 mQ to 1 mQ and the contact resistance of contact surfaces formed with AgCu may rise from about 1 . 1 mQ to 4 mQ . That is , depending on the material of the contact surfaces , the contact resistance may be increased by a factor of 3 to 4 over time .

The switching device described here makes use of the idea to provide a voltage metering circuit system configured to measure a voltage drop across the switching unit comprising the contact surfaces . In particular, the contact resistance is determined by the relation of the voltage drop across the contact system and the current flowing according to Ohm' s law . By measuring the voltage drop by the voltage metering circuit system and the current by the current sensor, the contact resistance may be calculated . Thus , a representation of the condition of the contact surfaces may be obtained . A damaged or uneven contact surface typically increase the contact resistance and hence the voltage drop across the contacts is increased accordingly . The condition of the contact surfaces may indicate i f the switching unit needs to be replaced, for example for safety reasons .

It is thus advantageously possible to determine the condition of the contact surfaces with high precision, in particular compared to common estimation techniques that are based on monitoring the number of switching operations. This particularly results in a reduced maintenance of the switching device and helps to reduce unnecessary replacements of the switching device. Thus, costs are reduced.

According to at least one embodiment of the switching device, the voltage metering circuit system comprises a first voltage metering path and the second voltage metering path. The first voltage metering path is connected to the first end of the switching unit and the second voltage metering path is connected to the second end of the switching unit. Furthermore, the voltage metering circuit system comprises an differential amplification stage connected to the first voltage metering path and the second voltage metering path. For example, the differential amplification stage is an operational amplifier or a differential amplifier. In particular, the first voltage metering path is connected to a non-inverting input of the differential amplification stage and the second voltage metering path is connected to an inverting input of the differential amplification stage or vice versa. The differential amplification stage is configured to generate an output difference voltage that is the voltage drop. That is, the differential amplification stage is a differential amplifier. The differential amplification stage preferably comprises an amplification factor, in particular if the differential amplification stage is, for example, an operational amplifier. The differential amplification stage may further comprise inputs for supply voltages .

During operation the differential amplification stage takes a voltage of the first voltage metering path and a voltage of the second voltage metering path as an input, forms a difference between these two voltages, and gives this differential voltage multiplied by the amplification factor as an output, which is the voltage drop. Preferably, the output of the differential amplification stage is connected to an input of the calculation unit. That is, the output of the differential amplification stage preferably forms an output of the voltage metering circuit system.

By arranging the first voltage metering path at the first end of the switching unit and the second voltage metering path at the second end of the switching unit, the voltage drop across the switching unit can be measured.

For example, an amplification factor of the differential amplification stage is at least 10. In particular, the amplification factor is between 10 and 100 or between 10 and 1000. For example, the amplification factor is at least 100 or at least 200 or at least 500 or at least 1000. For example, the amplification factor can be determined by choosing resistances of internal resistors of the differential amplification stage accordingly. By choosing a high enough amplification factor, even small changes in the contact resistance of the contact surfaces can be observed.

According to at least one embodiment of the switching device, the first voltage metering path comprises a first voltage divider and the second voltage metering path comprises a second voltage divider. Each voltage divider preferably comprises two resistors or more. In particular, an input of the first voltage divider is electrically conductively connected to the first end of the switching unit and an input of the second voltage divider is electrically conductively connected to the second end of the switching unit. Preferably, an output of the first voltage divider is arranged between the two resistors of the first voltage divider and connected to the differential amplification stage. Further preferably, an output of the second voltage divider is arranged between the two resistors of the second voltage divider and connected to the differential amplification stage.

By the first and second voltage divider, a voltage to the input of the differential amplification stage may be decreased. This may be result in an increased lifespan of the differential amplification stage. In particular, the voltage dividers are high impedance voltage dividers that form a protection impedance for the differential amplification stage and/or the calculation unit.

Since the differential amplification stage is configured to determine the voltage difference between the first voltage metering path and the second voltage metering path, a decrease in the absolute value of the voltages in these paths is insignificant as long as the decrease is the same in the first voltage metering path and second voltage metering path. To achieve this, the resistors of the first voltage divider and second voltage divider are preferably chosen to be equal.

According to at least one embodiment the switching device, the calculation unit comprises a storage unit configured to store at least the contact resistance of the contact surfaces. For example, the contact resistances for every closing of the switching unit may be stored in the storage unit. Therefore, a switching device history can be monitored. This switching device history can give an indication, i f contact wear is constant or i f it increases with every switching cycle , for example due to an uneven or inhomogeneous contact surfaces . The switching device history may also show the point in time when an over-proportional contact wear occurs and thus give an indication of the circumstances under which this occurs , for example a certain power level . This further not only gives an indication of the contact wear, but related increased power loss of a device can be detected, thus helping to reduce losses and foster sustainability . Furthermore , i f , for example , the switching is removed from one location and installed into another, for example i f an installation is modi fied, the switching device history is stored inside the storage unit , making an external documentation in principle unnecessary .

According to at least one embodiment of the switching device , the calculation unit is configured to store at least one contact parameter of the contact surfaces in the storage unit . Contact parameters are , for example , a material of the contact surfaces , a batch number, a si ze of the contact surfaces and/or a thickness of the contact surfaces . This data, together with the switching device history as described above stored in the storage unit , may advantageously increase precision of monitoring the contact wear .

According to at least one embodiment of the switching device , the calculation unit comprises a communication interface configured to transmit and/or receive at least the contact resistance of the contact surfaces . For example , the switching device history stored in the storage unit may be transmitted and/or received by the communication interface . Additionally or alternatively, contact parameters stored in the storage unit may be transmitted and/or received by the communication interface .

The communication interface allows for an external storage of data of the contact surfaces , for example , contact resistances or data regarding contact resistances . These externally stored data may be externally evaluated and/or processed and sent back to the switching device .

According to at least one embodiment of the switching device , the calculation unit comprises an analog-to-digital converter, abbreviated ADC, that an input of the calculation unit . The input of calculation unit is electrically conductively connected to the voltage metering circuit system and the current sensor . In particular, the ADC digiti zes analog signals corresponding to the voltage drop and/or the current for further processing in the calculation unit .

According to at least one embodiment of the switching device , the calculation unit comprises at least one of the following components : an application speci fic integrated circuit ( abbreviated AS IC ) , a field programmable gate array ( abbreviated FPGA) , a microcontroller, a system on a chip ( abbreviated SoC ) . For example , this component is capable of calculating the contact resistance on the basis of the voltage drop and the current .

The calculation unit is in particular configured to determine the contact wear of the contact surfaces based on the contact resistance of the contact surfaces . In particular, the contact wear is determined by the calculation unit by taking the switching device history stored in the storage unit into account . Furthermore , a circuit breaker is speci fied . In particular, the circuit breaker comprises at least one switching device described here . That is , all features disclosed for the switching device are also disclosed for the circuit breaker and vice versa .

For example , the circuit breaker comprises a power and/or an energy metering .

According to at least one embodiment , the circuit breaker is a motor protection circuit breaker of a motor case circuit breaker .

Furthermore , an arrangement is speci fied . In particular, the arrangement comprises at least one switching device described here . That is , all features disclosed for the switching device are also disclosed for the arrangement and vice versa .

According to at least one embodiment , the arrangement comprises a switching device at least comprising a communication interface , and an external computer . In particular, the external computer is distinct from the switching device . That is , the external computer is not part of the switching device .

The external computer is connected to the communication interface of the calculation unit of the switching device .

The external computer is configured to store and/or evaluate contact resistances of the contact surfaces of the switching unit transmitted by the communication interface . The external computer is further configured to transmit a contact wear of switching unit determined from evaluation of the contact resistances received from the switching device .

Additionally, contact parameters of the contact surfaces may be transmitted and stored in the external computer, for example in a database . These contact parameters may be used in evaluation of the contact resistances to obtain the contact wear . For example , the switching device history is stored in the external computer, preferably in the database .

In particular, i f a large amount of data regarding contact resistances of the contact surfaces and/or the switching device history has to be evaluated, the evaluation may be ef ficiently carried out by the external computer .

The external computer may be a server, for example a cloud server . For example , the external computer is configured to receive , store and/or evaluate data of a plurality of switching devices . In this case , the external computer may be a central server . For example , data of all switching devices with respect to contact resistances , type of switching device , serial number and the like , together with contact parameters may be stored in a database of the external computer . This data may be evaluated and analyzed, for example by statistical methods , to identi fy certain dependencies , typical peculiarities and the like , which cause and/or increase contact wear . This information may be used to ef ficiently predict the contact wear of the contact surfaces and to improve the switching devices . For example , by using this information a construction of the switching unit , a material of the contact surfaces and/or manufacturing processes may be improved . In particular, the connection between the switching device and the external computer is an internet connection . That is , of the switching device and the external computer are connected to the internet . It is possible that the connection is at least in part wireless .

According to at least one embodiment , the external computer is configured to evaluate data regarding the contact resistances by means of an arti ficial intelligence method . In particular, i f the external computer serves as a central server for a plurality of switching devices , a huge amount of data may be evaluated by the external computer . By an arti ficial intelligence method, this amount of data may be ef ficiently evaluated and analyzed .

Furthermore , a method for operating a switching device is speci fied . In particular, a switching device described here can be operated by the method . That is , all features disclosed for the switching device are also disclosed for the method and vice versa .

According to at least one embodiment of the method for operating a switching device , the contact resistance of the contact surfaces of switching unit is calculated every time the switching unit is closed .

According to at least one embodiment of the method, every time the contact resistance is calculated by the calculation unit , the contact resistance is stored in the storage unit of the switching device . Hence , it is possible to monitor the switching device history . According to at least one embodiment of the method, every time the contact resistance is calculated by the calculation unit , the calculated contact resistance is transmitted to an external computer configured to store and/or evaluate the contact resistance . For example , the contact resistance is stored in a database in the external computer . It is possible that the data of the database are evaluated by the external computer as described above .

Further advantages and advantageous embodiments and further developments of the switching device , the circuit breaker, the arrangement and the method for operating a switching device described herein will become apparent from the following exemplary embodiments shown in connection with schematic drawings . Identical elements , elements of the same kind or elements having the same ef fect , are provided with the same reference signs in the figures . The figures and the proportions of the elements shown in the figures are not to be regarded as true to scale . Rather, individual elements may be shown exageratedly large for better representability and/or for better comprehensibility .

In the figures :

Figure 1 shows a schematic circuit diagram illustrating a switching device described herein according to an exemplary embodiment ;

Figure 2 shows a schematic block diagram illustrating an arrangement described herein according to an exemplary embodiment ; Figure 3 shows a schematic circuit configuration of a simulation of a voltage metering circuit system according to an exemplary embodiment ; and

Figure 4 shows a graphical representation of a voltage drop obtained by the simulation according to Figure 3 .

The switching device 1 according to Figure 1 comprises a switching unit 2 . The switching unit 2 comprises a first electrical contact surface 21 and a second electrical contact surface 22 . The first electrical contact surface 21 is moveable and the second electrical contact surface 22 is fixed . By moving and bringing the first contact surface 21 into contact with the second contact surface 22 , the switching unit 2 and a main circuit 7 , in which the switching device 1 is integrated in, may be closed . The contact surfaces 21 , 22 comprise at least one metal and may be formed with at least one of the following materials : silver (Ag) , nickel (Ni ) , copper ( Cu) , cadmium ( Cd) , cadmium oxide ( CdO) .

The switching unit 1 further comprises a voltage metering circuit system 3 . The voltage metering circuit system 3 comprises a first voltage metering path 31 and a second voltage metering path 32 . The first voltage metering path 31 is electrically conductively connected to a first end 23 of the switching unit 2 and the second voltage metering path 32 is electrically conductively connected to a second end 24 of the switching unit 2 . The first end 23 of the switching unit 2 is electrically conductively connected to the first contact surface 21 and the second end 24 of the switching unit 2 is electrically connected to the second contact surface 22 . The voltage metering circuit system 3 comprises a differential amplification stage 33, which is preferably an operational amplifier, in particular a differential amplifier. The first voltage metering path 31 is connected to a non-inverting input of the differential amplification stage

33 and the second voltage metering path 32 is connected to an inverting input of the differential amplification stage 33. The differential amplification stage 33 is configured to form a difference between a voltage of the first voltage metering path 31 and a voltage of the second voltage metering path 32 and output this difference voltage multiplied by an amplification factor as a voltage drop 10.

Between the first end 23 of the switching unit 2 and the differential amplification stage 33, the first voltage metering path 31 comprises a first voltage divider 34. The first voltage divider 34 comprises a first resistor 341 and a second resistor 342. An output of the first voltage divider

34 is arranged between the two resistors 341, 342 of the first voltage divider 34 and is connected to the differential amplification stage 33. On a side opposite to the first resistor 341, the second resistor 342 is connected to ground 36.

Between the second end 24 of the switching unit 2 and the differential amplification stage 33, the second voltage metering path 32 comprises a second voltage divider 35. The second voltage divider 35 comprises a third resistor 351 and a fourth resistor 352. An output of the second voltage divider 35 is arranged between the two resistors 351, 352 of the second voltage divider 35 and is connected to the differential amplification stage 33. On a side opposite to the third resistor 351 , the fourth resistor 352 is connected to ground 36 .

By the first and second voltage divider 34 , 35 , a voltage to the input of the di f ferential ampli fication stage 33 may be decreased . The voltage dividers 34 , 35 form a high value protection impedance for the di f ferential ampli fication stage 33 and a calculation unit 5 of the switching device 1 .

The switching device 1 further comprises current sensor 4 . The current sensor 4 is configured to measure a current 11 of the main circuit 7 .

The switching device 1 comprises a calculation unit 5 . The calculation unit 5 is electrically conductively connected to the voltage metering circuit system 3 and the current sensor 4 . Between the current sensor 4 and the calculation unit 5 , a current signal conditioning operational ampli fier 41 is arranged . The current signal conditioning operational ampli fier 41 is configured to condition a current signal of the current sensor 4 .

The calculation unit 5 comprises an analog-to-digital converter ( abbreviated ADC ) 52 at an input side . The calculation 5 is configured to receive the voltage drop 10 provided by the voltage metering circuit system 3 and the current 11 provided by the current sensor 4 as inputs . The ADC 52 digiti ze these signals for further procession in the calculation unit 5 .

The calculation unit 5 is configured to calculate a contact resistance 6 of the switching unit 2 out of the voltage drop 10 and the current 11 . During operation of the switching device 1 the switching unit 2 is closed in order to close to the main circuit 7 . Each time the switching unit 2 is closed, the voltage drop 10 is measured by the voltage metering circuit system 3 . Additionally, the current 11 is measured by the current sensor 4 . The voltage drop 10 and the current 11 are trans ferred to the calculation unit 5 , where the contact resistance 6 is determined . The contact resistance 6 may be stored in a storage unit 51 of the calculation unit 5 and/or trans fer by a communication interface 51 of calculation unit

5 , for example to an external computer 100 .

By calculating the contact resistance 6 , a condition of the contact surfaces 21 , 22 may be obtained . I f , for example , the contact surfaces 21 , 22 are uneven or inhomogeneous or alter over time resulting in an increase of the contact resistance

6 . In particular by comparing the contact resistance 6 to previously obtained contact resistances , which are stored in the storage unit 50 , a degeneration and a contact wear may be detected and monitored . This allows for an improved contact wear detection . In particular, i f the switching device 1 is part of the circuit breaker, the switching device 1 and/or the circuit breaker may be replaced for security reasons before the contact wear is gone too far, but not unnecessarily early .

Figure 2 illustrates an arrangement 200 comprising a switching device 1 and an external computer 100 . The external computer 100 is not a part of the switching device 1 . The switching device 1 is , for example , the switching device 1 according to Figure 1 . The external computer 100 is connected to the communication interface 51 of the switching device 1 . By this connection, the external computer 100 and the switching device 1 may exchange data, for example with respect to contact resistances 6 of the switching unit 2 . The data may be stored and/or evaluated in the external computer 100 . In particular, i f a large amount of data is transmitted to the external computer 100 or the external computer 100 is connected to a plurality of switching devices 1 , an ef ficient evaluation of the data can be carried out by the external computer 100 . For example , the external computer 100 may calculate a contact wear of the switching units 2 and may send this information to the switching device 1 .

In particular, the external computer 100 is configured to evaluate the data of the switching device 1 by statistical methods . It is possible that the external computer 100 is configured to evaluate the data of the switching device 1 by means of an arti ficial intelligence method . This is in particular advantageous , i f a huge amount of data is evaluated by the external computer 100 . This can be the case i f , for example , the external computer is connected to a plurality of switching devices 1 .

Figure 3 shows a circuit configuration of a simulation of a voltage metering circuit system 3 . For example , the voltage metering circuit system 3 according to Figure 1 is simulated .

The voltage metering circuit system 3 is configured to measure a voltage drop 10 , by means of which a contact resistance 6 may be obtained . A main circuit 7 according to Figure 3 comprises an application voltage 70 and a load resistance 60 , simulating an application . In the simulation of Figure 3, the application voltage 70 is a DV voltage with 230 V at 50 Hz, the load resistance 60 is 4.6 Q and the contact resistance 6 is 20 pQ.

The voltage metering circuit system 3 comprises the first voltage divider 34 and second voltage divider 35. The first resistor 341 of the first voltage divider 34 and the third resistor 351 of the second voltage divider each have a resistance of 10 MQ in the simulation. The second resistor 342 of the first voltage divider 34 and the forth resistor 352 of the second voltage divider 35 each have a resistance of 1 MQ in the simulation.

The differential amplification stage 33 of the voltage metering circuit system 3 comprises a first amplification resistor 61, a second amplification resistor 62, a third amplification resistor 63, and a fourth amplification resistor 64 as internal resistors. The first amplification resistor 61 is arranged between a differentiator 65 of the differential amplification stage 33 and the first voltage divider 34. The second amplification resistor 62 is arranged between the differentiator 65 of the differential amplification stage 33 and the second voltage divider 35. The differentiator 65 is configured to form the difference voltage between the first voltage metering path 31 and the second voltage metering path 32. The third amplification resistor 63 is arranged in a circuit path that connects the output of the differentiator 65 with its inverting input. The fourth amplification resistor 64 is arranged between a noninverting input of the differentiator 65 and the ground 36.

By choosing resistances of the first to fourth amplification resistors 61 to 64, and amplification factor of the differential amplification stage 33 can be set. In the simulation of Figure 3, the first amplification resistor 61 and the second amplification resistor 62 each have a resistance of 10 kQ, and the third amplification resistor 63 and the fourth amplification resistor 64 each have a resistance of 1 MQ. This results in an amplification factor of 10.

The differential amplification stage 33 is powered by supply voltages 71, 72.

In the simulation of Figure 3, an analog-to-digital converter resistance 66 of the ADC 52 at the input of the calculation unit is chosen to be 10 kQ.

The resulting voltage drop 10 as measured at the ADC 52, i.e. at the analog-to-digital converter resistance 66 is graphically shown in Figure 4. An amplitude of the resulting voltage drop 10 is 100 pV. If, for example, the contact surfaces 21, 22 of the switching unit 2 degenerate, the contact resistance 6 increases. In this case, the amplitude of the voltage drop 10 would in increase to a value larger than 100 pV. Thus, by evaluating the voltage drop 10, i.e. the contact resistance, the condition of the contact surfaces 21, 22 of the switching unit 2 may be observed.

The invention is not restricted to the exemplary embodiments by the description on the basis of said exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which in particular comprises any combination of features in the patent claims and any combination of features in the exemplary embodiments, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.

This patent application claims the priority of German patent application 102023117876.8, the disclosure content of which is hereby incorporated by reference.

References

1 switching device

2 switching unit

3 voltage metering circuit system

4 current sensor

5 calculation unit

6 contact resistance

7 main circuit

10 voltage drop

11 current

21, 22 electrical contact surfaces

23, 24 first, second end of switching unit

31, 32 first, second voltage metering path

33 differential amplification stage

34, 35 first, second voltage divider

36 ground

41 current signal conditioning operational amplifier

50 storage unit

51 communication interface

52 analog-to-digital converter

60 load resistance

61...64 first to fourth amplification resistors

65 differentiator

66 analog-to-digital converter resistance

70 application voltage

71, 72 supply voltage

100 external computer

200 arrangement

341, 342 first, second resistor

351, 352 third, fourth resistor

Claims

Claims :

1. A switching device (1) comprising

- a switching unit (2) with electrical contact surfaces (21, 22) ,

- a voltage metering circuit system (3) connected to a first (23) and a second end (24) of the switching unit (2) and configured to measure a voltage drop (10) across the switching unit (2) ,

- a current sensor (4) connected to the second end (24) of the switching unit (2) configured to measure a current (11) ,

- a calculation unit (5) connected to the voltage metering circuit system (3) and the current sensor (4) configured to determine a contact resistance (6) of the contact surfaces (21, 22) of the switching unit (2) by means of the voltage drop (10) and the current (11) , and

- the calculation unit (5) is configured to determine a contact wear of the contact surfaces (21, 22) based on the contact resistance (6) of the contact surfaces (21, 22) .

2. The switching device (1) according to claim 1, wherein

- the voltage metering circuit system (3) comprises a first voltage metering path (31) , a second voltage metering path (32) , and an differential amplification stage ( 33 ) ,

- the first voltage metering path (31) is connected to the first end (23) of the switching unit (2) ,

- the second voltage metering path (32) is connected to the second end (24) of the switching unit (2) ,

- the differential amplification stage (33) connected to the first voltage metering path (31) and the second voltage metering path (32) configured to generate an output difference voltage as the voltage drop (10) .

3. The switching device (1) according to claim 2, wherein the first voltage metering path (31) comprises a first voltage divider (34) and the second voltage metering path (32) comprises a second voltage divider (35) .

4. The switching device (1) according to one of the preceding claims, wherein the calculation unit (5) comprises a storage unit (50) configured to store at least the contact resistance (6) of the contact surfaces (21, 22) .

5. The switching device (1) according to claim 4, wherein calculation unit (5) is configured to store at least one contact parameter of the contact surfaces (21, 22) in the storage unit (50) .

6. The switching device (1) according to one of the preceding claims, wherein the calculation unit (5) comprises a communication interface (51) configured to transmit and/or receive at least the contact resistance (6) of the contact surfaces (21, 22) .

7. The switching device (1) according to one of the preceding claims, wherein the calculation unit (5) comprises an analog-to-digital converter (52) at an input of the calculation unit (5) connected to the voltage metering circuit system (3) and the current sensor ( 4 ) .

8. The switching device (1) according to one of the preceding claims, wherein the calculation unit (5) comprises at least one of the following components: an application specific integrated circuit, a field programmable gate array, a microcontroller, a system on a chip.

9. A circuit breaker comprising at least one switching device (1) according to one of the preceding claims.

10. The circuit breaker according to claim 9, wherein the circuit breaker is a motor protection circuit breaker or a motor case circuit breaker.

11. An arrangement (200) comprising at least one switching device (1) according to claim 6 and an external computer (100) connected to a communication interface (51) of the calculation unit (5) , wherein

- the external computer (100) is configured to store and/or evaluate contact resistances (6) of the contact surfaces (21, 22) of the switching unit (2) transmitted by the communication interface (51) ,

- the external computer (100) is configured to transmit a contact wear of the switching unit (2) determined from evaluation of the contact resistances (6) of the contact surfaces (21, 22) received from the switching device

(1) •

12. The arrangement (200) according to claim 11, wherein the external computer (100) is configured to evaluate data regarding the contact resistances (6) by means of an artificial intelligence method.

13. The arrangement (200) according to claim 11 or 12, wherein the external computer (100) is configured to store at least one contact parameter of the contact surfaces (21, 22) .

14. A method for operating a switching device (1) according to one of the claims 1 to 8, wherein the contact resistance (6) of the contact surfaces (21, 22) of the switching unit (2) is calculated every time the switching unit (2) is closed.

15. The method according to claim 14, wherein

- the calculation unit (5) comprises a storage unit

( 50 ) , and

- every time the contact resistance (6) of the contact surfaces (21, 22) is calculated, the contact resistance (6) is stored in the storage unit (50) .

16. The method according to claims 14 or 15, wherein

- the calculation unit (5) comprises a communication interface (51) , and

- every time the contact resistance (6) of the contact surfaces (21, 22) is calculated, the contact resistance (6) is transmitted to an external computer (100) configured to store and/or evaluate the contact resistance ( ) .