LOW-VOLTAGE CIRCUIT BREAKER

Description

[0001] The invention relates to a low-voltage circuit breaker for a low-voltage circuit according to the preamble of patent claim 1.

[0002] Circuit breakers are protective devices that function similarly to a fuse. Circuit breakers monitor the current flowing through them via a conductor and interrupt the electrical current or energy flow to an energy sink or load. This is referred to as tripping when protection parameters, such as current limits or current-period limits, are exceeded. The set current limits or current-period limits are the corresponding trigger factors. The interruption is usually achieved by the mechanical contacts of the circuit breaker opening.

[0003] Especially for low-voltage circuits, systems, or networks, there are various types of circuit breakers depending on the level of the intended electrical current in the electrical circuit. Circuit breakers in the sense of the invention refer in particular to switches such as those used in low-voltage systems for currents, in particular rated currents or maximum currents, from 63 to 6300 amperes. Enclosed circuit breakers are used more specifically for currents from 63 to 1600 amperes, in particular from 125 to 630 or 1200 amperes. Open circuit breakers are used in particular for currents from 630 to 6300 amperes, more specifically from 1200 to 6300 amperes.

[0004] Circuit breakers, also known as circuit breakers (CBs for short), are divided into open circuit breakers or air circuit breakers (ACBs for short) and closed circuit breakers or molded case circuit breakers (MCCBs for short).

[0005] Low voltage refers to voltages up to 1000 volts AC or 1500 volts DC. More specifically, low voltage refers to voltages greater than extra-low voltage, with values ​​of 50 volts AC or 120 volts DC.

[0006] Low-voltage switches within the meaning of the invention refer, in particular, to switches used for rated currents or maximum currents up to 63 amperes, in particular from 6.3 amperes to 16 amperes or from 16 amperes to 63 amperes. Low-voltage switches can, in particular, be so-called miniature circuit breakers or miniature circuit breakers.

[0007] For the purposes of the invention, circuit breakers are understood to mean, in particular, circuit breakers with an electronic trip unit serving as a control unit, also referred to as an Electronic Trip Unit (ETU for short).

[0008] Recently, hybrid switching devices have emerged that combine power electronics with an electromechanical contact system. Previous, especially purely electromechanical, concepts have disadvantages or are unsuitable for power grids that are no longer determined by the short-circuit power of a transformer. The reasons for this unsuitability are that these grids are fed by converters in special "active front ends," which have very fast switching times that cannot be detected or switched off by conventional switching devices. The classic protection algorithms and mechanical delay times of electromechanical or previously known hybrid switches or switching concepts are too slow. Fully electronic switches are fast, but have the disadvantage of high power loss and high costs, especially when SiC-based semiconductors are used.In addition, these protective devices do not have galvanic isolation, which is often required by product standards.

[0009] Furthermore, DE 196 01 540 A1 discloses a circuit breaker and a circuit interrupting device. Furthermore, GB 2 550 155 A discloses a vacuum switch with a

[0010] The object of the present invention is to improve a low-voltage circuit breaker or low-voltage switch of the type mentioned at the outset, in particular to provide a hybrid switch which is suitable for networks in which fast switching times are required.

[0011] This object is achieved by a low-voltage circuit breaker having the features of patent claim 1.

[0012] According to the invention, a low-voltage circuit breaker is proposed, comprising: at least one current sensor for determining the level of the electrical current of a conductor of the low-voltage circuit breaker assigned to the current sensor, wherein a current sensor can be provided for each conductor or part of the conductors, at least one electromechanical switching unit for connecting and disconnecting at least two electrical contact points, of which at least one is movable such that in a first switching position of the movable contact point, two contact points are connected to one another and in a second switching position, the respective contact points are not connected to one another, wherein an electromechanical switching unit can be provided for each conductor or part of the conductors, at least one electronic switching unit having a semiconductor switching element, which is electrically conductive in a first switching state and electrically blocking in a second switching state,which is electrically connected in parallel to the electromechanical switching unit, whereby an electronic switching unit can be provided for each conductor or part of the conductors, an electronic tripping unit connected to the current sensor, the electronic and the electromechanical switching unit(s), which are designed in such a way that when current and / or current-time limit values ​​of the conductor (or at least one conductor) are exceeded, the electromechanical switching unit is first disconnected and then the electronic switching unit is blocked, If there are several electromechanical and electronic switching units, this is done in parallel for all corresponding switching units.

[0013] According to the invention, the electromechanical switching unit is designed as a vacuum switch in which the contact points are in a vacuum, and a piezoelectric actuator is provided for changing the switching position (commutation) of the electromechanical switching unit.

[0014] This has the particular advantage that a piezoelectric actuator is used to commutate the electrical current from the electromechanical switching unit or mechanical contact to the electronic switching unit or (power) semiconductor switching element or (power) semiconductor path. The piezoelectric actuator is so fast that movement is possible in approximately 20 µs or less. This makes it possible to switch to the parallel power semiconductor path in a time that allows the semiconductor now in the current path to carry the current and switch without reaching the semiconductor's destruction limit. This allows very fast shutdowns or interruptions of the electrical circuit.

[0015] This also has the particular advantage of enabling a low-voltage switch, i.e. a switch for smaller currents than the low-voltage circuit breaker, in which a series connection of electromechanical switching unit and electronic switching unit is enabled, with the piezo-operated electromechanical switching unit taking over the task of galvanic isolation.

[0016] Furthermore, with smaller currents, only smaller masses of the contacts or contact points need to be moved, whereby piezoelectric actuators can be used inexpensively.

[0017] According to the invention, at least one electromechanical separating unit is provided, which is arranged electrically in series with the parallel circuit of vacuum switch / new electromechanical switching unit and electronic switching unit.

[0018] This has the particular advantage that galvanic isolation can be achieved.

[0019] In an advantageous embodiment of the invention, the electromechanical isolating unit has isolating properties. Isolating properties refers to an isolating function in which a certain minimum distance or minimum air gap is realized between the contacts of the electromechanical isolating unit. This minimum air gap is essentially voltage-dependent. Other parameters are the degree of contamination, the type of field (homogeneous, inhomogeneous), and the air pressure or altitude above sea level. Corresponding regulations or standards exist for these minimum air gaps or creepage distances. For example, for air, these regulations specify the minimum air gap for an inhomogeneous and a homogeneous (ideal) electric field for a surge voltage withstand voltage, depending on the degree of contamination. The surge voltage withstand voltage is the strength when a corresponding surge voltage is applied.Only if this minimum length (minimum distance) is present does the electromechanical isolating unit have an isolating function or isolating property. For the purposes of the invention, the DIN EN 60947 and IEC 60947 series of standards, which are incorporated herein by reference, are relevant for the isolating function and its properties. This has the particular advantage that the low-voltage circuit breaker has an isolating function.

[0020] According to the invention, the electromechanical isolating unit is connected to the electronic tripping unit and if the current and / or current-time limit values ​​of the conductor are exceeded, the vacuum switch or the new electromechanical switching unit is first disconnected, then the electronic switching unit is blocked and then the electromechanical isolating unit is disconnected.

[0021] This has the particular advantage that the separation function is created automatically.

[0022] In an advantageous embodiment of the invention, the piezoelectric actuator is a piezo stack.

[0023] This has the particular advantage of providing a particularly simple and inexpensive implementation for the piezo actuator, whereby the piezo stack allows large switching strokes for the electromechanical switching unit to be realized.

[0024] According to the invention, the semiconductor switching element is a silicon-based component, specifically an IGBT (isolated gate bipolar transistor). "Silicon-based" specifically does not mean a SiC (silicon-carbon)-based component.

[0025] This has the particular advantage of being particularly cost-effective to implement.

[0026] In an advantageous embodiment of the invention, the switch is provided for a low-voltage circuit and a vacuum switch or a new electromechanical and an electronic switching unit are provided for each conductor of the low-voltage circuit monitored by the switch.

[0027] This has the particular advantage that each monitored conductor of the low-voltage circuit is protected by a solution according to the invention. In a three-phase alternating current circuit, the three phase conductors and, if a neutral conductor is present, the neutral conductor are protected. Thus, three or four combinations of electromechanical and electronic switching units are provided. These can be supplemented, if necessary, by three or four electromechanical isolating units.

[0028] All embodiments, in dependent form referring back to patent claim 1, bring about an improvement of a low-voltage circuit breaker or low-voltage switch, in particular for improving the switching times.

[0029] 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.

[0030] The accompanying drawing shows: Figure 1 a block diagram of a low-voltage circuit breaker; Figure 2 a block diagram of a first arrangement according to the invention; Figure 3 a representation of an electromechanical switching unit according to the invention; Figure 4 a block diagram of another arrangement not according to the invention.

[0031] Figure 1shows a schematic block diagram of a low-voltage circuit breaker LS or low-voltage switch NS of conventional design. Figure 1 shows electrical conductors L1, L2, L3, N of a low-voltage circuit, for example, a three-phase AC circuit, where the first conductor L1 forms the first phase, the second conductor L2 the second phase, the third conductor L3 the third phase, and the fourth conductor the neutral conductor N of the three-phase AC circuit. The conductors are routed through the low-voltage circuit breaker LS or low-voltage switch NS. The low-voltage circuit breaker LS or low-voltage switch NS are arranged, in particular, in a housing.

[0032] In the example according to Figure 1the first conductor L1 is connected to an energy converter EW (for example as part of a converter set) in such a way that at least part of the current, i.e. a partial conductor current, or the entire current of the first conductor L1 flows through the primary side of the energy converter EW. Usually, one conductor, in the example the first conductor L1, forms the primary side of the energy converter EW. The energy converter EW is usually a transformer with a core, e.g. an iron transformer. In one embodiment, an energy converter EW can be provided in each phase or in each conductor of the electrical circuit. The secondary side of the energy converter EW or of each provided energy converter is connected to a power supply NT (or several power supplies), which has a power supply, e.g.provides its own power supply, for example, in the form of a supply voltage, for the electronic trip unit (ETU), represented by a dashed connection of operating voltage conductors (BS). The NT power supply unit can also be connected to at least one or all current sensors (SE1, SE2, SE3, SEN) to supply power to the current sensors, if necessary.

[0033] Each current sensor SE1, SE2, SE3, SEN has at least one sensor element, for example a Rogowski coil, a measuring resistor / shunt, a Hall sensor, or similar, for determining the magnitude of the electrical current of the conductor assigned to it in the electrical circuit. In the example, the first current sensor SE1 is assigned to the first conductor L1, i.e., the first phase; the second current sensor SE2 to the second conductor L2, i.e., the second phase; the third current sensor SE3 to the third conductor L3, i.e., the third phase; and the fourth current sensor SEN to the (fourth conductor) neutral conductor N.

[0034] The first to fourth current sensors SE1, SE2, SE3, SEN are connected to the electronic trip unit ETU and transmit to it the level of the electrical current of the respective conductor.

[0035] The transmitted current level is compared in the electronic trip unit (ETU) with current limit values ​​and / or current-time limit values ​​that constitute the triggering reasons. If these are exceeded, the electrical circuit is interrupted. This provides overcurrent and / or short-circuit protection. This can be achieved, for example, by providing an electromechanical switching unit (EM), which is connected to the electronic trip unit (ETU) on the one hand and has contacts (K) or contact points for interrupting conductors L1, L2, L3, N, or other conductors on the other hand. In this case, the electromechanical switching unit (EM) receives an interruption signal to open the contacts or contact points.

[0036] Figure 2 shows an arrangement ANS1 according to the invention, wherein the arrangement ANS1 according to Figure 2 instead of the electromechanical switching unit EM according to Figure 1is used, for example, an arrangement ANS1 according to the invention is used in each conductor L1, L2, L3, N, in the example four units ANS1 according to the invention would replace the previous electromechanical switching unit EM according to Figure 1 substitute.

[0037] Figure 2 shows a conductor, for example the first conductor L1, which has a parallel circuit of a novel electromechanical switching unit EMVP (vacuum switch) according to the invention and an electronic switching unit EL. An electromechanical separating unit TE is connected in series with this parallel circuit (EMVP, EL), as shown in Figure 2 The parallel circuit units (EMVP, EL) and the electromechanical isolating unit (TE) are connected in the usual way to the electronic trip unit ETU or a circuit breaker control unit via connections (not shown).

[0038] Figure 3showed a representation of a new electromechanical switching unit EMVP or vacuum switch EMVP according to the invention, as shown in Figure 2 is to be used. This can have a housing GEH. It also has contacts K, specifically a fixed contact point KSF and a movable contact point KSB. Alternatively, two movable contact points can be provided.

[0039] Both are arranged in a vacuum, for example in a vacuum tube VR.

[0040] The movable contact point KSB is actuated by a piezo actuator PA, in particular by a piezo stack, with which a large stroke / switching path can be realized, i.e. its position can be changed so that in a first switching position the two contact points KSB, KSF are connected to one another so that an electrical current can flow, and in a second switching position the respective contact points KSB, KSF are not connected to one another, i.e. are separated so that no electrical current can flow.

[0041] According to the invention, in a low-voltage circuit breaker, an interruption process first involves a separation, ie opening or non-connection of the contacts / contact points, of the vacuum switch EMVP / new electromechanical switching unit EMVP and then a blocking, ie . a non-conductive or high-resistance, the electronic switching unit EL.

[0042] During a closing process, the electronic switching unit EL first becomes conductive or low-resistance, then the new electromechanical switching unit EMVP or vacuum switch EMVP closes, ie the contacts close or the contact points are connected to each other.

[0043] The electromechanical isolating unit TE opens its contacts during an interruption process following the non-conductive or high-resistance state of the electronic switching unit EL.

[0044] During a closing process, the contacts of the electromechanical separating unit TE close first before the electronic switching unit EL becomes low-resistance or conductive.

[0045] Figure 4 shows another arrangement ANS2 not according to the invention for a low-voltage switch NS, in which instead of the electromechanical switching unit EM according to Figure 1 the second arrangement ANS2 according to Figure 4 is used.

[0046] Figure 4shows an electronic switching unit EL, which is electrically connected in series to the new electromechanical switching unit EMVP or vacuum switch EMVP, according to Figure 3 , is switched on.

[0047] In the case of a low-voltage switch NS with a series connection of an electronic switching unit EL and a new electromechanical switching unit EMVP, if the current and / or current-time limit values ​​of the conductor are exceeded, the electronic switching unit EL is first blocked and then the new electromechanical switching unit / vacuum switch EMVP is disconnected.

[0048] During a closing process, the new electromechanical switching unit / vacuum switch EMVP is closed first and then the electronic switching unit EL is made conductive or low-resistance.

[0049] According to the invention, the electronic switching unit EL comprises at least one semiconductor switching element, which is an isolated gate bipolar transistor (IGBT). In a first switching state, the electronic switching unit EL is electrically conductive, i.e., low-resistance, and in a second switching state, it is electrically blocking, i.e., high-resistance—ideally non-conductive.

[0050] The new electromechanical switching unit / vacuum switch EMVP for connecting at least two electrical contact points is designed, for example, in such a way that the piezo actuator PA is coupled to the movable contact point KSB, so that the movable contact point KSB can be adjusted between the first switching position and the second switching position by means of the piezo actuator PA.

[0051] In one embodiment, the vacuum switch EMVP can be designed such that several movable electrical contact points KSB are provided, which are mechanically coupled to one another so that they can be adjusted jointly between the switching positions by the piezo actuator PA.

[0052] This means that two, three or four (or more) contacts can be opened or closed simultaneously by a piezo actuator.

[0053] The advantage of the invention lies, among other things, in a drive technology for electromechanical switching that allows a switch position change / commutation in the µs (microsecond range), i.e., switching from the electromechanical current path to the electronic current path (semiconductor path). Previously known concepts are too slow. A piezostack implementation according to the invention offers the possibility of adjusting both the response time and the stroke.

[0054] The possible limitation of the stroke of piezo actuators is compensated according to the invention by a vacuum tube, ie the piezo drive is combined with a vacuum tube.

[0055] In one embodiment, the piezo actuator can be integrated into the vacuum tube or vacuum chamber.

[0056] The required isolating distances can also be realized with smaller spacing using a vacuum chamber or tube, which is particularly advantageous for low-voltage switches or, where applicable, low-voltage circuit breakers.

[0057] The dimensioning of the vacuum chamber depends on the rated current. This can be advantageously exploited by the fact that power semiconductors, such as those used in converters, already limit the current. Furthermore, it is possible to switch from expensive semiconductor materials such as SiC to Si, which also has a higher current-carrying capacity and is more cost-effective than IGBTs.

[0058] A galvanic isolation distance can be achieved with an electromechanical isolation unit (TE) or isolator connected in series.

[0059] 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.

Claims

1. Low-voltage circuit breaker (LS) having: - at least one current sensor (SE1, SE2, SE3, SEN), for determining the level of the electrical current through a conductor (L1, L2, L3, N), associated with the current sensor, of the low-voltage circuit breaker, - at least one electromechanical switching unit (EM) for connecting and disconnecting at least two electrical contact points (KSB, KSF), of which at least one is movable in such a way that, in a first switching position of the movable contact point (KSB), the contact points (KSB, KSF) are connected to one another and, in a second switching position, the contact points (KSB, KSF) are not connected to one another, - at least one electronic switching unit (EL), which has a semiconductor switching element, is electrically conductive in a first switching state and electrically blocking in a second switching state, and is connected electrically in parallel with the electromechanical switching unit (EM), - an electronic trip unit (ETU), which is connected to the current sensor (SE1, SE2, SE3, SEN), the electronic switching unit (EL) and the electromechanical switching unit (EM), and is configured in such a way that, when current or / and current / time span limit values of the conductor are exceeded, first disconnection of the electromechanical switching unit (EM) and then blocking of the electronic switching unit (EL) takes place, wherein the electromechanical switching unit (EM) is configured as a vacuum circuit breaker (EMVP), in which the contact points (KSB, KSF) are in the vacuum, wherein at least one electromechanical disconnecting unit (TE) is provided, which is arranged electrically in series with the parallel circuit comprising the vacuum circuit breaker (EMVP) and the electronic switching unit (EL), wherein the electromechanical disconnecting unit (TE) is connected to the electronic trip unit (ETU) and, when current or / and current / time span limit values of the conductor are exceeded, first disconnection of the vacuum circuit breaker (EMVP) and then blocking of the electronic switching unit (EL) takes place, and subsequently disconnection of the electromechanical disconnecting unit (TE) takes place, characterized in that the semiconductor switching element is an IGBT, and in that a piezoelectric actuator (PA) is provided for the change in switching position of the electromechanical switching unit.

2. Breaker according to Claim 1, characterized in that the piezoelectric actuator (PA) is a piezostack.

3. Breaker according to either one of the preceding claims, characterized in that the breaker is provided for a low-voltage circuit, and a vacuum circuit breaker (EMVP) and an electronic switching unit (EL) are provided for each conductor (L1, L2, L3, N), which is monitored by the breaker, of the low-voltage circuit.