WO2000026934A1 - Electric micromechanical residual-current protective switching device - Google Patents

Abstract

The invention relates to a novel residual-current protective switching device. The switch or switches (1, 1') have at least one respective microrelay (3) for the interruption of current or currents in monitored current paths (8, 8').

Description

 ELECTRIC MICROMECHANICAL FAULT CURRENT SWITCHING DEVICE

This invention relates to an electrical switching device for residual current protection.

Conventional two-pole residual current circuit breakers ("Fl switches") essentially consist of an induction coil for detecting a current asymmetry between, for example, a phase conductor and a neutral conductor of a household power supply. The currents in the conductors are added taking their direction into account. If the sum is clear a non-zero, ie above a certain threshold, triggers a conventional electromagnetic relay switch, in which case it must be assumed that the fault current above the threshold is due to an impermissible short circuit, earth contact or leakage current.

The invention is based on the technical problem of specifying a new, improved residual current circuit breaker.

According to the invention, this problem is solved on the one hand by an electrical fault current protection switching device with a first micro-relay switch in a first current path and an evaluation device for receiving and evaluating signals from a first current sensor that detects the current through the first current path and a second current sensor that detects a current through a second current path by comparing them with one another and opening the first microrelay switch in response to a result of the evaluation, and on the other hand by means of an electrical residual current protection switching device with a first microrelay switch in a first circuit and a first total current sensor which detects a total current through the first current path and at least one second adjacent current path and an evaluation device for receiving and evaluating a signal of the first total current sensors and opening the first micro relay switch in response to a result of the evaluation.

Embodiments of the invention can be found in the various dependent claims.

The invention is based on the basic idea that the use of microrelay switches in a residual current circuit breaker has various essential advantages. A micro relay as such is state of the art. This is an electrically operated miniature switch, which, in contrast to a transistor, is a mechanical switch with at least one movable contact piece. The mechanical movement of this contact piece is caused by an electrical signal. Various mechanisms can be used for implementation. Electrostatically actuated microrelay cells are particularly preferred here. However, electromagnetic devices can also be used, in which planar spiral coils with ferromagnetic movable contact pieces are generally used. Piezoelectric microrelays are also possible, but require high control voltages.

As a concrete example of a possible technology for an electrostatically actuated microrelay cell, reference is made to a Si microrelay published by Siemens (HF Schlaak, F. Arndt, J. Schimkat, M. Hanke, Proc. Micro System Technology 96, 1996, pages 463- 468). Reference is also made to R. Allen: "Simplified Process is Used to Make Micromachined FET-like Four-Terminal Microswitches and Microrelays" in Electronic Design, 8 July, 1996, page 31 and to "Micromechanic Membrane Switches on Silicon" by KE Petersen , IBM J. RES. DEVELOP., Vol. 23, No. 4, July 1979, pages 376-385. The disclosure content of these and the sources cited below is included in this application.

In this invention, the term microrelay switch now designates switching devices consisting of a single microrelay as well as switching devices directions that contain two or more microrelays. This is referred to again below.

Returning to the advantages of the microrelay switches mentioned, considerably faster switching times in the range of, for example, 100-200 μs are possible instead of the reaction times of the conventional residual current circuit breakers of over 25 ms. This aspect is particularly important in view of the safety function of residual current circuit breakers.

Furthermore, the microrelay switches can be realized with extremely low component weights and volumes in comparison to conventional electromagnetically operated relays. In this respect, they are suitable for installation in technical environments in which a conventional residual current circuit breaker would either lead to a significant increase in weight or volume or would generally not be usable. An example are smaller electronic devices, plug connections z. B. on cables, standard housing for connector sockets z. B. for wall mounting etc.

In this context, it should finally be mentioned that micro-relay switches allow mass production at very low unit costs due to the mass production technologies used in the field of semiconductor technology.

The first of the two above definitions of the invention now uses at least one microrelay switch which is actuated in response to the signals of at least two current sensors. Each current sensor detects the current through a respective current path, for example a cable or a conductor track. The evaluation device compares the signals with one another and, in so far, can detect the occurrence of a fault current through a mismatch between the individual signals. Accordingly, the result of this evaluation is decisive for the actuation of the micro relay switch. In the second definition of the invention, an overall current sensor was mentioned which detects the current through a first current path together with the current through the second current path. A current sensor is envisaged which, based on the spatial conditions, detects the sum of the two currents suitable for the fault current detection, taking into account their directions. For example, two conductor tracks can lead the currents to be compared in opposite directions as current paths, the total current sensor detecting the total current, ie a zero current in the case of an equal amount. Accordingly, the signal of the total current sensor only has to be compared by the evaluation device with a correspondingly small threshold value in order to control the micro relay switch.

It is of course also possible that the total current sensor does not detect the currents through the two (or even several) current paths with the same sensitivity, but instead does not deliver a zero signal due to certain spatial relationships when the currents are identical in magnitude. Then, of course, the evaluation device can also be designed to relate the signal of the total current sensor to a specific target range that is not centered on the value zero.

Of course, the two variants of the invention can also be combined in different ways.

One embodiment of the invention relates to a residual current protection switching device for three-phase lines with neutral conductor, in which a fault current is therefore to be determined with reference to the adjustment in four current paths. For this purpose, according to the invention, four current sensors can be provided for each current path, the signals of which are evaluated by the evaluation device.

In addition to a total current sensor measuring the currents through two current paths, a third and a fourth current sensor or a second total current sensor can also be provided for the third and fourth current paths. The evaluation device is a preferably microelectronically implemented circuit which is readily apparent to the person skilled in the art with regard to the task.

In the case of the current sensors, it must first be ascertained that they do not necessarily have to be part of the fault current protection switching device according to the invention. This can also be conventional current sensors, for example induction coils. With regard to the advantages possible with the invention, however, the most advantageous choice relates to Hall sensors, which, as semiconductor elements, can likewise be comparatively small, light and inexpensive. In particular, very low detection limits can also be achieved with Hall sensors, for example in the range of approximately 1 mA compared to a conventional detection limit of approximately 10 mA or above.

So far, the invention has been described in connection with a microrelay switch in one of the current paths. Of course, two or more microrelay switches can also be possible, with which some or all of the current paths affected by the detection can be switched. In the case of the three-phase lines with neutral conductor already mentioned, it is of interest, for example, to switch off all four poles when detecting a fault current. Even in the case of a line with a phase and a neutral conductor, it can be advantageous to be able to interrupt both lines. For example, this frees you from the need to take care during installation not to interchange the phase and neutral at any point. This is particularly advantageous in the area of plug-in connections because they are often constructed symmetrically and can also be plugged in if the neutral and phase are mixed up. In particular, there are also safety regulations for Fl switches that require all poles to be switched off.

It has already been pointed out that the term microrelay switch is used here in a general sense, which means both a single microrelay and also includes a switching device consisting of two or more microrelays. This takes into account the fact that, due to technology, micro-relays are subject to certain limits with regard to their current carrying capacity and dielectric strength. If the current carrying capacity or the dielectric strength of the individual microrelay envisaged is not sufficient for the intended application, it is provided according to the invention to use voltage-dividing series circuit comprising two or more microrelay cells and / or current-dividing parallel circuits. Switch panels in the sense of voltage-dividing series circuits of parallel circuits which divide the current in each stage of the series circuit can also be used. With regard to this aspect, reference is made to the pre-registration "New electrical switching device" filed on October 9, 1998 by the same applicant with the file number 19846639.0, the disclosure content of which is included here.

However, at the time of filing this invention, there are known technological tendencies to implement individual microrelays with fairly high voltage and current tolerances. Further improvements in the future are therefore foreseeable. For example, a research project by the manufacturer Bosch is working with the University of Bremen on the development of micro relays with 24 V maximum switching voltage and 25 A maximum switching current. From the numerical values mentioned it can be seen that, in particular, the microrelay has sufficient current carrying capacity for many applications, for example in household power networks. Then a corresponding series connection is sufficient for the adaptation to the respective voltage specification.

It is particularly advantageous to produce different micro-relay switches with a fixed standard technology and a correspondingly unchanged standard micro-relay cell in different sizes of the parallel connection, series connection or control panel. All that is required is to change the geometry of the layout, for example by exchanging the mask set. Otherwise, the manufacturing process is practically unchanged. This results in largely maintaining the cost advantages of a large Series production Possibilities to cover a wide range of different electrical specifications. Incidentally, this applies both to the case of individual microrelay switches and in an integrated combination with other electronic devices.

The above-mentioned advantage of the very fast response speed of the individual microrelay cells is advantageously incorporated directly into the entire microrelay switch without interconnecting a plurality of microrelay cells. This means that even with large specification values, extremely responsive residual current circuit breakers can be implemented. Comparable conventional residual current circuit breakers are considerably limited due to the inertia of the moving masses.

A further embodiment of the invention consists in a double function of the evaluation device, which helps the residual current protection switching device according to the invention to a second function as an overcurrent protection switching device. The invention is equivalent to a conventional electromagnetic contactor. For this purpose, the evaluation device compares the signals of the current sensors with a threshold value defining an overcurrent and opens the micro-relay switch or switches in response to the result of this comparison. Here too, the disclosure content of the previously cited prior application "New electrical switching device" is referred to.

The invention can be implemented in various integration variants. On the one hand, the microrelay switch or switches, the evaluation device and possibly also the Hall sensors can each be designed as semiconductor chips, which are mounted together on a circuit board. Here, the invention already shows significant advantages because, due to the design of the micro relay switch, which is related to semiconductor technology, the same assembly technology or at least very similar assembly technologies can be used for the components involved, with a small size and low weight. In this context, it should be pointed out in particular that Hall sensors are also on a chip, for example can be carried out on a silicon chip or another substrate material. As an example of a design very closely related to microelectronics, reference is made to "Cylindrical Hall Device" by H. Blanchard, L. Chiesi, R. Racz and RS Popovic, Proceedings IEDM 96, pages 541-544, IEEE 1996.

However, the invention is also very suitable for combining different components with one another on a chip. For example, the evaluation device and the micro relay switch can be integrated. With a suitable technology of the Hall sensors, these can also be integrated. On the other hand, it can make sense to integrate only the evaluation device and the Hall sensors, while the micro-relay switches are designed as separate chips or separate chips. This allows the combination of a standard component for the evaluation device and the Hall sensors with different levels for different electrical designs of the microrelay switches with regard to their current and voltage load. The integration of other electronic components, e.g. B. of temperature sensors for a temperature-controlled reading of the micro relay switch, timer circuits, etc. is possible.

Devices for displaying the response of the residual current protection switching device to a residual current (or also to an overcurrent or an increased temperature) can also be integrated in an optical or acoustic manner.

A specific embodiment of the invention is described below with reference to the figures. Features disclosed here can also be essential to the invention individually or in combinations other than those shown.

FIG. 1 shows a schematic circuit diagram of a microrelay switch of a residual current protection switching device, and

FIG. 2 shows the complete residual current protection switching device with two micro relay switches according to FIG. 1. FIG. 1 shows a microrelay switch 1 consisting of 17 series-connected stages 2, each with 45 microrelay cells 3, which are connected in parallel. Technologically, each microrelay cell 3 corresponds to the already mentioned Siemens silicon 5 microrelay and, each with a microrelay cell 3, is the preceding and one of the following Level 2 electrically connected. In the last and in the first of the stages 2, the connections are brought together on the outer side and connected to a common connection of the microrelay switch 1.

₁ 0 One can also see in a highly schematic representation a movable contact piece 4, which here corresponds to an electrostatically bendable or deflectable spring tongue. It is essential in the switching device according to the invention that all these movable contact pieces 4 work synchronously, ie are opened and closed by a single common signal, in so far as

15 parts of a jointly constructed uniform switch work.

Each individual microrelay cell 3 can interrupt a voltage of approximately 24 V, so that a switchable voltage of 400 V results for the microrelay switch 1. This is a value that is favorable for many applications, 20 in particular values above 200 or 300 V are preferred.

The switchable load current for each microrelay cell 3 is approximately 200 mA and thus results in a total current of 9 A for the microrelay switch 1.

2. This microrelay switch 1 requires a total activation power of only 5 mW and shows a power loss in the order of 0.6-6 W in the conductive state. However, the latter value can be improved by further improving the contacts and possibly increasing the closing force of the microrelay cells lower further. Particularly in view of the extraordinarily low activation power, there is clearly scope for the closing force. The arrangement of individual microrelay cells 3 shown in FIG. 1 forms a microrelay switch 1 in the sense of the invention. It is essential here that the micro-relay switch 1 is opened and closed uniformly, ie all movable contact pieces 4 of the individual micro-relay cells 3 are opened or closed simultaneously. The switching field from the microrelay cells 3 therefore behaves like a uniform switch 1.

FIG. 2 shows two of the microrelay switches 1 shown in FIG. 1 in a residual current protection switching device according to the invention. The first micro relay switch is designated by the reference number 1 and the second micro relay switch, which is constructed identically, by the reference number 1 '. The first microrelay switch 1 and the second microrelay switch 1 'are each connected in a first current path 8 and a second current path 8', the two current paths 8, 8 'being branched off from two lines which can be seen in the upper region of FIG. 2 and in the lower region the figure 2 to a consumer. For example, the first current path 8 corresponds to a phase line and the second current path 8 'corresponds to the associated neutral conductor. An earth line is not shown because it plays no role in the invention.

The two microrelay switches 1, 1 ', more precisely their respective contact pieces 4, are controlled via a control line 9. This control line 9 is identical for both microrelay switches 1, 1' because the microrelay switches 1, 1 'are switched together and simultaneously. Merely because of the galvanic isolation between the phase-conducting first current path 8 and the second neutral conductor path 8 ', two separate microrelay switches 1, 1' are provided. A common microrelay switch could also be used if it has galvanically isolated connections for the current paths, which have a sufficient dielectric strength in relation to one another.

The common control line 9 leads to an evaluation device 7 which has two parts 7a and 7b with regard to their function. Both parts 7a and 7b of the evaluation device 7 are supplied with a respective output signal. nes first Hall sensor 5 and a second Hall sensor 5 '. The first Hall sensor 5 detects the current through the first current path 8 and the Hall sensor 5 'detects the current through the second current path 8'. (Each of the Hall sensors 5, 5 'requires a drive power of approximately 60 to 360 mW). The part 7a of the evaluation device 7 determines the sum of the currents through the current paths 8, 8 'from the signals of the Hall sensors 5, 5', taking into account their direction, that is to say the difference in the amounts. If this sum or difference lies above a relatively small threshold value of approximately 5 mA, part 7a of the evaluation device 7 outputs a control signal via the control line 9, which the two microrelay switches 1, 1 'within approximately 150 μs after the detection of the Fault current, ie the excessive current sum or difference opens. This means that both current paths 8, 8 'are interrupted, and the defect in the consumer supplied by the current paths 8, 8', which is to be assumed due to the fault current, can be eliminated.

On the other hand, the part 7b of the evaluation device 7 monitors the signals of the Hall sensors 5, 5 'for themselves, i. H. compares the detected current quantities individually with a threshold value, which represents the maximum permissible current in the current paths. If an overcurrent occurs, that is to say the threshold value is exceeded, part 7b of the evaluation device 7 in the same way ensures immediate opening of the micro-relay switches 1 and 1 '.

The fault current protection switching device according to the invention thus simultaneously has the function of an overcurrent protection switching device. It is clear that the same microrelay switches 1, 1 ', Hall sensors 5, 5' and the same control line 9 can be used for this. In addition, the representation of the evaluation device 7 as consisting of two parts 7a and 7b is only related to the function of the evaluation device 7. The same circuit units can be used for the most part within the evaluation device 7 for the two functions 7a and 7b, for example the same input stages for the signals from the Hall sensors 5, 5 ', the same control stage for the micro-relay switches 1, 1', etc The difference between the two parts

consists only in the signal processing itself, i. H. between the comparison between two current signals with a tolerance predetermined by the fault current threshold value on the one hand and the comparison of the respective individual current signal with the overcurrent threshold value on the other hand.

The evaluation device 7 is designed as an integrated Si analog circuit. The Hall sensors 5, 5 ′ are designed on a Si substrate in accordance with the publication “Cyclic Hall Device” already cited. In the variant shown here in FIG. 2, the evaluation device 7, the Hall sensors 5, 5 are also and the two microrelay switches 1, 1 are integrated on the same uniform Si chip 6. In this exemplary embodiment, the residual current protection switching device according to the invention thus corresponds to a single Si chip 6 which is provided with a suitable housing with corresponding connections for a conventional household power line, which correspond to the two current paths 8, 8 'outside the housing The housing is only shown symbolically with the frame 10 in Figure 2 and can, for example, correspond to a conventional connector housing.

Claims

Expectations 1 . Electrical residual current protection switching device with a first micro-relay switch (1) in a first current path (8) and an evaluation device (7) for receiving and evaluating signals from a first current sensor (5) and one that detects the current through the first current path (8) a current through a second current path (8 ') detecting second current sensor (5') by comparison with each other and opening the first micro relay switch (1) in response to a result of the evaluation. 2. Electrical residual current protection switching device according to claim 1, wherein the evaluation device (7) for receiving and evaluating signals of the first and the second current sensor (5, 5 ') as well as a third current sensor detecting a current through a third current path and a current is designed by a fourth current sensor that detects a fourth current path. 3. Electrical residual current protection switching device according to claim 1 or 2, wherein the current sensors (5, 5 ') are part of the switching device and formed by Hall sensors. 4. Electrical residual current protection switching device with a first microrelay switch (1) in a first current path (8) and a first total current sensor and a total current through the first current path and at least one second adjacent current path Evaluation device for receiving and evaluating a signal of the first total current sensor and opening the first microrelay switch (1) in response to a result of the comparison. 5. Electrical residual current protection switching device according to claim 4 with a second and a third current sensor or with a second total current sensor for detecting the currents or the total current by a third and a fourth current path, the evaluation device being designed to receive and evaluate signals from the first total current sensor and the second and third current sensors or the second total current sensor. 6. Electrical residual current protection switching device according to one of the preceding claims with a second microrelay switch (1 ') in the second current path (8'), in which the evaluation device (7) also opens the second microrelay switch (1 ') in response to the result of the evaluation - net. 7. Electrical residual current protection switching device according to claim 6 in conjunction with one of claims 2, 3, 5 with at least one third microrelay switch in at least the third current path, in which the evaluation device also opens at least the third microrelay switch in response to the result of the evaluation. 8. Electrical residual current protection switching device according to claim 4 or 5, also in connection with claim 6 or 7, in which the current sensor or sensors (5, 5 ') or total current sensors are formed by Hall sensors. 9. Electrical residual current protection switching device according to one of the preceding claims, wherein the one or more microrelay switches (1, 1 ') have a voltage-dividing series circuit of microrelay cells (3). 10. Electrical residual current protection switching device according to one of the preceding claims, wherein the one or more microrelay switches (1, 1 ') have a current-dividing parallel connection of microrelay cells (3). 11. Electrical residual current protection switching device according to one of the preceding claims, in which the one or more microrelay switches (1, 1 ') each have at least one microrelay (3) with a mechanically moved contact piece (4). 12. Electrical residual current protection switching device according to one of the preceding claims, in which the evaluation device (7) further compares the signals of the current sensor (s) (5, 5 ') or the total current sensors with an overcurrent threshold value and the micro relay switch (s) (1 , 1 ') opens in response to the result of this comparison. 13. Electrical residual current protection switching device according to one of the preceding claims, in which the micro-relay switch or switches, the evaluation device and optionally the Hall sensors are each integrated as chips on a circuit board. 14. Electrical residual current protection switching device according to one of the preceding claims, in which the one or more microrelay switches (1, 1 ') and the evaluation device (7) are integrated on a chip (6). 15. Electrical residual current protection switching device according to claim 3 or 8, also in connection with one of claims 9-13, in which the evaluation device (7) and the Hall sensors (5, 5 ') are integrated on a chip (6). 16. Electrical residual current protection switching device according to claim 3 or 8, also in connection with one of claims 9-13, in which the or the micro-relay switch (1, 1 '), the evaluation device (7) and the Hall sensors (5, 5th ') are integrated on a chip (6).