PROTECTIVE SWITCH AND PROCEDURES

Description

[0001] The invention relates to the technical field of a protective switching device for a low-voltage circuit, such as a circuit breaker, according to the preamble of patent claim 1 and a method for a protective switching device for a low-voltage circuit according to the preamble of patent claim 9.

[0002] Low voltage refers to voltages of up to 1000 volts AC or up to 1500 volts DC. Low voltage refers in particular to voltages greater than extra-low voltage, with values ​​of 50 volts AC or 120 volts DC.

[0003] Low-voltage circuits, networks or systems refer to circuits with nominal currents or rated currents of up to 125 amperes, more specifically up to 63 amperes.

[0004] Miniature circuit breakers are long-established overcurrent protection devices used in low-voltage electrical circuits. They protect cables from damage caused by overheating due to excessive current and / or short circuits. A miniature circuit breaker can automatically disconnect the circuit in the event of an overload and / or short circuit. A miniature circuit breaker is a non-self-resetting fuse element.

[0005] Unlike miniature circuit breakers, circuit breakers are designed for currents greater than 125 A, and in some cases even as low as 63 A. Miniature circuit breakers are therefore simpler and more delicate in design. Miniature circuit breakers typically have a mounting option for mounting on a top-hat rail (DIN rail, TH35).

[0006] Miniature circuit breakers are typically electromechanical in design. They contain a switching contact or shunt release within a housing to interrupt (trip) the electrical current; a bimetallic protective element or bimetallic element to trip (interrupt) in the event of a prolonged overcurrent (overcurrent protection) or thermal overload (overload protection); an electromagnetic release with a coil for brief tripping when an overcurrent limit is exceeded or in the event of a short circuit (short-circuit protection); and one or more arc-quenching chambers or arc-quenching devices. They also contain connection elements for conductors of the electrical circuit to be protected.

[0007] Basically, circuit breakers monitor the level of electrical current in the circuit and interrupt the circuit if current limits or current-time limits are exceeded.

[0008] Arc faults are arcs that occur in the event of a fault, i.e., caused by faults in the electrical circuit. For example, due to poorly clamped, faulty, or poorly conductive connections or contacts in the electrical circuit, e.g., in junction boxes, switches, or sockets in the low-voltage circuit.

[0009] This does not include (interference) arcs such as those that occur during regular operation of a network, e.g. when switching or on the brushes of a motor.

[0010] Serial arc faults refer to arcs that occur in the current path of a circuit, meaning that the current flows through the arc and, for example, also flows through a load. This means that if a current flows in a "nearly broken" conductor, a so-called serial arc fault occurs at the point of interruption.

[0011] Arc fault devices are relatively new protective devices for electrical circuits or voltage networks and are used to detect such (particularly serial) arc faults.

[0012] Fire protection switches can be used in particular in domestic installations, such as fuse boxes, to detect such faults and, in the event of a fault or if an arc fault limit is exceeded, initiate an interruption of the electrical circuit, interrupt the circuit themselves or emit an arc fault detection signal.

[0013] For example, US 2015 / 0 070 026 A1 discloses a method for detecting the cause of a voltage loss upstream of a circuit breaker.

[0014] Furthermore, DE 10 2018 219 692 A1 discloses a protective switching device for a low-voltage circuit for detecting serial arc faults.

[0015] The object of the present invention is to improve a protective switching device, in particular a (classical) circuit breaker, and specifically to enable a measuring function.

[0016] This object is achieved by a protective switching device having the features of patent claim 1 or a method according to patent claim 9.

[0017] According to the invention, a protective switching device is provided for interrupting an electrical low-voltage circuit when current or current-time limit values ​​are exceeded, comprising: a housing with terminals for conductors of the low-voltage circuit, an interruption unit with contacts for interrupting the low-voltage circuit within the housing, a bimetallic release connected to the interruption unit, a magnetic release connected to the interruption unit (UB).

[0018] According to the invention, an (additional) resistance-based current measuring device is provided for periodically determining the current level of the low-voltage circuit. The resistance-based current measuring device is connected to a measuring unit. The protective switching device has a communication unit. The communication unit receives the current values ​​determined by the measuring unit. The communication unit transmits the determined current values ​​via a wired or wireless connection.

[0019] Thus, a protective switching device, for example a conventional miniature circuit breaker, advantageously has a measuring function that transmits the measured data to an external device. The protective switching device (circuit breaker) remains unchanged in its classic functions, particularly with regard to the bimetallic and magnetic release.

[0020] Advantageous embodiments of the invention are specified in the subclaims.

[0021] An arc fault detection unit is provided, which receives current values ​​determined by the resistance-based current measuring device for arc fault detection. This has the particular advantage of supplementing the (conventional) protective switching device with an arc fault detection device (fire protection switch). To perform arc fault detection, the resistance-based current measuring device, which provides high current measurement accuracy with suitable resistance material, is advantageously used for arc fault detection.

[0022] In an advantageous embodiment of the invention, the current values ​​determined by the resistance-based current measuring device are used exclusively for the arc fault detection or (or / and) transmission by means of the communication unit.

[0023] This means that the (additional) resistance-based current measuring device is not used for overcurrent and short-circuit protection. This means that the (additional) resistance-based current measuring device is not used for bimetallic releases or the magnetic release.

[0024] This has the particular advantage that a classic protective switching device, such as a miniature circuit breaker, remains unchanged with its existing units (bimetallic release, magnetic release) and is easily expanded to include additional functions (measuring function with transmission, arc fault detection and interruption).

[0025] In an advantageous embodiment of the invention, the resistance-based current measuring device is part of the current-carrying section of the bimetallic release (BM). This has the particular advantage of enabling particularly good and space-saving integration of the resistance-based current measuring device into an (existing) protective switching device.

[0026] In an advantageous embodiment of the invention, the current-carrying section of the bimetal release contains the material Wieland-F12.

[0027] Alternatively, the current-carrying section of the bimetallic release contains a material with a thermal expansion coefficient of the order of 19.5 x 10 -6 < 1 / K or better.

[0028] This has the particular advantage of achieving high accuracy in current measurement while maintaining high thermal stability and low mechanical expansion (avoiding mechanical stresses in the device).

[0029] In an advantageous embodiment of the invention, the measuring unit is designed such that a series circuit of an amplifier with programmable gain, an analog-to-digital converter and a computing unit is provided.

[0030] This has the particular advantage of providing a simple implementation for a measuring unit and a simple connection of the measuring unit to the resistance-based current measuring device.

[0031] In an advantageous embodiment of the invention, the analog-to-digital converter (ADC) is designed as a 24-bit delta-sigma multi-level modulator analog-to-digital converter.

[0032] This has the particular advantage of providing effective and appropriate analog-to-digital conversion. The analog values ​​received from the shunt in the form of a voltage drop relative to the current flowing through the shunt are converted directly into digital current values ​​by using the same reference potential in the measurement IC. This keeps offset errors to a minimum, thus achieving highly accurate values.

[0033] The same applies to measuring voltage, the only difference is that the analog values ​​are obtained from a voltage divider circuit.

[0034] The arc fault detection unit is connected to the communication unit.

[0035] This has the particular advantage that, in addition to the current measurement data, data from the arc fault detection unit can also be transmitted. This provides extended measurement functionality.

[0036] In an advantageous embodiment of the invention, the protective switching device is a circuit breaker.

[0037] This has the particular advantage of allowing a simple extension of an existing concept while retaining the previously proven functionality and without significant intervention in it.

[0038] According to the invention, a parallel method for a protective switching device for an electrical low-voltage circuit is further claimed, with the advantages already mentioned.

[0039] All embodiments, both in dependent form referring back to the independent patent claims and referring back only to individual features or combinations of features of patent claims, result in an improvement of a protective switching device.

[0040] The described properties, features and advantages of this invention and the manner in which they are achieved will become clearer and more clearly understandable in connection with the following description of the embodiments, which are explained in more detail in connection with the drawings.

[0041] The drawing shows: Figure 1 a first representation of a protective switching device to explain the invention, Figure 2a second representation of a protective switching device to explain the invention, Figure 3 a third representation of a protective switching device to explain the invention, Figure 4 a representation of a resistance-based current measuring device to explain the invention, Figure 5 a fourth representation of a protective switching device to explain the invention,

[0042] Figure 1 shows a representation of a protective switching device SG for a low-voltage circuit, in the example for a single-phase AC circuit, such as a circuit breaker, comprising: a housing (not shown) with input terminals Ne, Le and output terminals Na, La for the conductors of the low-voltage circuit. In the example, a power source is connected to the input terminals Ne, Le and one or more consumers are connected to the output terminals Na, La. The input and output terminals Ne, Na can be provided for the neutral conductor and the input and output terminals Le, La can be provided for the phase conductor of the low-voltage circuit. an interruption unit UB with contacts KT for interrupting the low-voltage circuit within the housing. The connection between the interruption unit UB and the contacts KT is shown by a dashed line. a bimetallic release BM connected to the interruption unit UB, shown by a dashed line. a magnetic release MR connected to the interruption unit UB.Indicated by a dashed line, a resistance-based current measuring device SH, in the example a resistor, shunt, shunt resistor, measuring resistor for periodically determining the current level of the low-voltage circuit, a measuring unit ME connected to the current measuring device SH. The measuring unit is connected to both terminals of the current measuring device SH, e.g., the measuring resistor. The current measuring device SH is arranged in one conductor of the low-voltage circuit. The measuring unit ME is also connected to the other conductor of the low-voltage circuit. In the example, the current measuring device SH is arranged in the phase conductor, i.e., in the current path between the terminals Le, La; the measuring unit ME is then (on the other hand) connected to the neutral conductor Ne, Na.

[0043] The measuring unit ME in the example according to Figure 1an internal communication unit (not shown in detail) that receives current values ​​measured by the measuring unit ME. The communication unit transmits the measured current values ​​via a wired or wireless connection.

[0044] The bimetal release BM or bimetal or bimetal protective element is provided in a conductor of the low-voltage circuit through which the current of the low-voltage circuit flows. In the example according to Figure 1The bimetallic release BM is located in the phase conductor, i.e., in the current path between the terminals Le and La. If excessive currents are present in the low-voltage circuit for a certain period of time, the bimetallic release BM heats up and deforms as a result of the heating. This deformation, via the connection to the interruption unit UB, triggers the interruption unit UB, which then opens the contacts KT and interrupts the electrical circuit. This means that if the current-time limit values ​​are exceeded, the bimetal interrupts the circuit; this is also referred to as thermal tripping.

[0045] The magnetic release MR is also located in a conductor of the low-voltage circuit, through which the current of the low-voltage circuit flows. In the example shown in Figure 1, the magnetic release MR is located in the phase conductor, i.e. in the current path between the terminals Le, La. I.e. in series with the bimetallic release BM and the resistance-based current measuring device SH. The magnetic release MR has a coil through which the electrical current of the low-voltage circuit flows. If the electrical current exceeds certain current limits, the magnetic field of the coil becomes so strong that iron parts of the magnetic release MR are attracted, which trip the interruption unit UB and consequently open the contacts KT and lead to the interruption of the electrical circuit. This is referred to as magnetic tripping, which occurs when current limits are exceeded.In the event of a short circuit in the low-voltage circuit, the low-voltage circuit is interrupted almost immediately.

[0046] The KT contacts can be equipped with an arc quenching device (ARC) that extinguishes any arc that occurs when the contacts open. The arc quenching device can be equipped with a so-called arc runner (AR).

[0047] According to Figure 1The input-side connection Ne, for example for a neutral conductor (input-side neutral conductor connection), is connected to the output-side connection Na (output-side neutral conductor connection) via a first partial contact of the KT contacts. The input-side connection Le, for example for a phase conductor (input-side phase conductor connection), is connected to the output-side connection La (output-side phase conductor connection) via the magnetic release MR, the second partial contact of the KT contacts, the bimetallic release BM, and the resistance-based current measuring device SH. The arc quenching device ARC with arc rotor AR is connected in parallel to the second partial contact of the KT contacts. The current can flow from the second partial contact KT to the bimetallic release BM via a flexible conductor FL.

[0048] The measuring unit ME is connected on the one hand to both terminals of the current measuring device SH, in the example a measuring resistor, and on the other hand to the output-side terminal Na (output-side neutral conductor terminal).

[0049] Figure 2 shows an arrangement according to Figure 1 , with the difference that the resistance-based current measuring device SH is located in the neutral conductor, i.e., between the input and output terminals Ne, Na, so that the current of the neutral conductor flows through the resistance-based current measuring device SH. The measuring unit ME is connected on the one hand to the two terminals of the resistance-based current measuring device SH in the neutral conductor and on the other hand to the phase conductor. According to Figure 2the input-side connection Ne, for example for the neutral conductor (input-side neutral conductor connection), is connected to the output-side connection Na (output-side neutral conductor connection) via the first partial contact of the contacts KT of the resistance-based current measuring device SH.

[0050] The input-side terminal Le, for example for the phase conductor (input-side phase conductor terminal), is connected to the output-side terminal La (output-side phase conductor terminal) via the magnetic release MR (not shown), the second partial contact of the contacts KT, the bimetallic release BM.

[0051] The interruption unit UB also has a mechanical handle HB for manually interrupting or closing the low-voltage circuit. This can also be seen in the other illustrations ( Figure 1 , Figure 3 , Figure 5 ) should be provided.

[0052] Figure 3shows a representation according to Figure 1 , with a detailed illustration of an inventive combined bimetal release BM and resistance-based current measuring device SH. The resistance-based current measuring device SH is part of the current-carrying section of a bimetal release BM. In the example, the middle section of a current-carrying section of the bimetal release BM. According to the invention, the current-carrying section of the bimetal release BM contains the material Wieland-F12. Alternatively, the current-carrying section of the bimetal release BM can contain a material with a thermal expansion coefficient in the order of 19.5 x 10 -6 < 1 / K or better.

[0053] This means that the middle section of the current-carrying section, for example, contains the material Wieland-F12 as a measuring resistor (resistance-based current measuring device), while the material of the bimetallic release is connected to the sides (left and right). This means a series circuit: bimetallic release material, measuring resistor (resistance-based current measuring device), and bimetallic release material. The middle section, or the section containing the measuring resistor, has a first terminal A1 and a second terminal A2 for connection to the measuring unit ME.

[0054] In Figure 4 is another detailed representation.

[0055] This advantageously reduces (or does not increase) the size of the circuit breaker. The current measuring device SH is located inside the circuit breaker. To reduce the space required in the circuit breaker, the bimetallic release BM or its bimetallic carrier is modified to advantageously contain a current measuring shunt made of Wieland-F12, a resistance alloy characterized by its low temperature coefficient of electrical resistance and its low thermal-electromotive force compared to copper. The alloy also exhibits high long-term stability of its electrical resistance.

[0056] Figure 3 and Figure 4show an implementation using this resistance-based current measuring device. The bimetal itself cannot be used as a resistance-based current measuring device because its resistance is high and not temperature-stable. Accurate current measurement would therefore not be possible. The resistance-based current measuring device can be installed in the phase conductor or the neutral conductor.

[0057] When a resistance-based current measuring device is introduced into the current path, it changes the thermal and short-circuit characteristics of the device. This problem is solved by using Wieland F12 material, which has a thermal expansion coefficient of 19.5 x 10^-6 / K.

[0058] The bimetal carrier according to Figure 4can be manufactured through a combination of welding and a special tool for pressing the measuring resistor onto the bimetallic carrier. The final bimetallic carrier consists of the carrier material on both sides, e.g., copper or (or / and) steel, with the high-precision resistance material welded in the center.

[0059] Figure 5shows an arrangement according to the preceding figures, with the difference that the measuring unit ME is connected to a separate communication unit COM. Furthermore, an arc fault detection unit is provided, which in the example is designed in two parts: a first arc fault detection unit AFDD1, which is connected to a second arc fault detection unit AFDD2. The first arc fault detection unit AFDD1 is connected to the resistance-based current measuring device SH, and the second arc fault detection unit AFDD2 is connected to the interruption unit UB for interrupting the low-voltage circuit upon detection of arc faults. Furthermore, the arc fault detection unit, in the example the second arc fault detection unit AFDD2, can be connected to the communication unit COM for transmitting information regarding the arc fault detection, etc.

[0060] The arc fault detection unit receives the current values ​​determined by the resistance-based current measuring device for the arc fault detection (parallel to the measuring unit).

[0061] The first arc fault detection unit AFDD1 can, for example, have functions for signal conditioning of the supplied current and voltage values ​​(from the conductors). The second arc fault detection unit AFDD2 can, for example, have an evaluation unit, e.g., with a microprocessor, for detecting arc faults.

[0062] The modifications according to the invention allow the introduction of a measuring function. The measuring unit can comprise a programmable amplifier with a programmable gain, an analog-to-digital converter, and a computing unit, such as a microprocessor. The analog-to-digital converter can be configured as a 24-bit delta-sigma multi-level modulator.

[0063] For example, the programmable amplifier is connected to both sides of the measuring resistor.

[0064] The current values ​​received by the computing unit or calculation engine are transmitted via the communication unit, for example with a UART interface, with wireless communication, wired communication, optical systems or similar.

[0065] Thus, the resistance-based current measuring device SH and measuring unit ME according to the invention enable current measurement with a very high accuracy in the range of 1% or better / less space-saving (due to the modifications according to the invention).

[0066] A protective switching device, or in particular a circuit breaker, can be converted into a measuring device that provides corresponding data without requiring additional space by adding a resistance-based current measuring device.

[0067] An existing conductor, an original part of the circuit breaker, is used as a measuring resistor to measure the current by modifying the current-carrying conductor path on the bimetal. This can be done very cost-effectively.

[0068] It is advantageous to add measurement and communication functionality to a circuit breaker, e.g. with integrated fire protection switch function.

[0069] The resistance-based current measuring device SH can avoid the problem of phase shift in current measurement.

[0070] The resistance-based current measuring device SH with low resistance value results in only low power loss, which avoids thermal problems.

[0071] The invention allows a measuring function to be integrated in a circuit breaker, e.g. with a width of 18 mm (1 TE), in a space-saving manner.

[0072] According to the invention, a modified bimetallic carrier is used in a circuit breaker as the primary path for current flow from the L and N terminals through the device. To measure the current through the device, this primary current-carrying path through the bimetallic carrier is modified to include a current-sensing mechanism, which, however, alters the thermal and short-circuit characteristics of the device. The choice of material, along with the joining process, is very important, as the material expands and transmits its thermal stresses to the welded components, altering the tripping behavior on the thermal side of the bimetal. The presence of thermal stresses at the junctions can further heat the terminals and alter the effects of the bimetal.The solution and material used allow current measurement with very high accuracy and minimal impact on the other parts of the protective switching device.

[0073] Although the invention has been illustrated and described in detail by the embodiment, the invention is not limited by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without departing from the scope of the invention as defined by the claims.

Claims

1. Circuit breaker device (SG) for interrupting an electrical low-voltage circuit when current or current-time limit values are exceeded, having: - a housing with connections (Ne, Na, Le, La) for conductors of the low-voltage circuit, - an interruption unit (UB) with contacts (KT) for interrupting the low-voltage circuit within the housing, - a bimetallic tripping device (BM) connected to the interruption unit (UB), and - a magnetic tripping device (MR) connected to the interruption unit (UB), wherein a resistance-based current measuring apparatus (SH) is provided for periodically ascertaining the magnitude of the current of the low-voltage circuit, and is connected to a measuring unit (ME), characterized in that the circuit breaker device has a communication unit (COM) that receives current values ascertained by the measuring unit (ME) from the measurement unit (ME) by means of a first communication connection, in that the communication unit (COM) transmits the ascertained current values in a wired or wireless manner, in that an arcing fault detection unit (AFDD1, AFDD2) is provided, which receives current values ascertained by the resistance-based current measuring apparatus (SH) for the arcing fault detection in parallel with the measuring unit (ME), in that the arcing fault detection unit (AFDD1, AFDD2) is connected to the communication unit (COM) by means of a second communication connection, which is different to the first communication connection, in order to transmit data from the arcing fault detection unit (AFDD1, AFDD2).

2. Circuit breaker device (SG) according to Patent Claim 1, characterized in that the current values ascertained by the resistance-based current measuring apparatus (SH) are used exclusively for the arcing fault detection or transmission by means of the communication unit (COM).

3. Circuit breaker device (SG) according to Patent Claim 1 or 2, characterized in that the resistance-based current measuring apparatus (SH) is part of the current-carrying section of the bimetallic tripping device (BM).

4. Circuit breaker device (SG) according to Patent Claim 3, characterized in that the current-carrying section of the bimetallic tripping device (BM) contains the material Wieland-F12.

5. Circuit breaker device (SG) according to Patent Claim 3, characterized in that the current-carrying section of the bimetallic tripping device (BM) contains a material with a coefficient of thermal expansion of the order of magnitude of 19.5 x 10-6 1 / K or better.

6. Circuit breaker device (SG) according to one of the preceding patent claims, characterized in that the measuring unit (ME) is configured in such a way that a series circuit comprising a programmable gain amplifier (PGA), an analogue-to-digital converter (ADC) and a computing unit is provided.

7. Circuit breaker device (SG) according to Patent Claim 6, characterized in that the analogue-to-digital converter (ADC) is in the form of a 24-bit delta-sigma multi-level modulator analogue-to-digital converter.

8. Circuit breaker device (SG) according to one of the preceding patent claims, characterized in that the circuit breaker device is a miniature circuit breaker.

9. Method for a circuit breaker device (SG) for interrupting an electrical low-voltage circuit when current or current-time limit values are exceeded, having a housing with connections (Ne, Na, Le, La) for conductors of the low-voltage circuit, an interruption unit (UB) with contacts (KT) for interrupting the low-voltage circuit within the housing, a bimetallic tripping device (BM) connected to the interruption unit (UB), and a magnetic tripping device (MR) connected to the interruption unit (UB), wherein a resistance-based current measuring apparatus (SH) is provided for periodically ascertaining the magnitude of the current of the low-voltage circuit, and is connected to a measuring unit (ME) that is connected to a communication unit (COM) by means of a first communication connection, such that the current values ascertained by means of the resistance-based current measuring apparatus (SH) are transmitted in a wired or wireless manner, in that an arcing fault detection unit (AFDD1, AFDD2) is provided, which receives current values ascertained by the resistance-based current measuring apparatus (SH) for the arcing fault detection in parallel with the measuring unit (ME), in that the arcing fault detection unit (AFDD1, AFDD2) is connected to the communication unit (COM) by means of a second communication connection, which is different to the first communication connection, in order to transmit data from the arcing fault detection unit (AFDD1, AFDD2).