Safety electric switch

Abstract

The present invention relates to an electrical switch (1) for interrupting the current between a first interface and a second interface (11, 12), which has a third interface (13), a semiconductor switch (2), a fuse (3), and a circuit breaker (4), wherein a series circuit composed of the fuse (3) and the semiconductor switch (2) is provided between the first interface (11) and the second interface (12), and a series circuit composed of the fuse (3) and the circuit breaker (4) is provided between the first interface (11) and the third interface (13), wherein the fuse (3) has a triggering threshold, the triggering threshold has a current boundary value, and the current boundary value has a value between the persistently permitted current of the semiconductor switch (2) and the maximum permitted current of the semiconductor switch (2). The present invention also relates to a power grid (10) having at least one such electrical switch (1) and an energy source (7), wherein the energy source (7) is connected to the first interface (11) and the third interface (13) of the electrical switch (1). The present invention also relates to a method for operating such an electrical switch (1) or such a power grid (10), wherein the circuit breaker (4) is at least temporarily closed when the semiconductor switch (2) is overloaded.

Description

Field of the Invention

[0001] The present invention relates to an electrical switch for interrupting the current between a first interface and a second interface by means of a semiconductor switch. The present invention further relates to an electrical grid having at least one such electrical switch and an energy source. The present invention further relates to a method for operating such an electrical switch or such an electrical grid. Background Art

[0002] An electrical switch, also referred to as an electrical switching device or a semiconductor-based switching device, is understood to be a component that has at least one semiconductor switch and can switch, in particular interrupt, the current. Examples of semiconductor switches are transistors, such as IGBTs, MOSFETs, IGCTs, etc.

[0003] In fact, semiconductor-based switching devices are equipped with a conventional fuse connected in series in order to be able to implement a safety level restoration even in the event of a semiconductor switch failure. The construction and sizing of the fuse are designed such that it triggers in the case of a short-circuit current passing through the semiconductor switch and a turn-off failure of the semiconductor switch. The task of the fuse is to protect the load connected to its line or the connected subnet, etc.

[0004] A series circuit is understood to be a series arrangement of components, where the voltages at the individual components are added. Thus, a star circuit has a plurality (at least three) of series circuits. Summary of the Invention

[0005] The object on which the present invention is based is to improve the electrical switch.

[0006] This object is achieved by an electrical switch for interrupting the current between a first interface and a second interface, which has a third interface, a semiconductor switch, a fuse, and a short-circuit breaker, where a series circuit composed of the fuse and the semiconductor switch is provided between the first interface and the second interface, and a series circuit composed of the fuse and the short-circuit breaker is provided between the first interface and the third interface, where the fuse has a triggering threshold that has a current boundary value, and the current boundary value has a value between the permanently permissible current of the semiconductor switch and the maximum permissible current of the semiconductor switch. Furthermore, this object is achieved by an electrical grid having at least one such electrical switch and an energy source, where the energy source is connected to the first interface and the third interface of the electrical switch. Furthermore, this object is achieved by a method for operating such an electrical switch or such an electrical grid, where the short-circuit breaker is closed at least temporarily when the semiconductor switch is overloaded.

[0007] Further advantageous embodiments of the present invention are given in the dependent claims.

[0008] The present invention is based on the following understanding: A short-circuit current can be generated through a series circuit composed of a fuse and a circuit breaker, and this short-circuit current causes the fuse to respond, thereby protecting the semiconductor switch and one or more loads connected to the electrical switch from overload. Here, an energy source, such as a fed DC bus, is connected to the first and third interfaces of the electrical switch, and the load or a subnet with different loads is connected to the second and third interfaces. The response of the fuse is also referred to as the triggering of the fuse.

[0009] If the semiconductor switch is subjected to overload, the semiconductor switch will cut off the power as quickly as possible. This is achieved by putting the circuit breaker into the conducting state and driving the short-circuit current from the connected energy source via the fuse. As a result, the fuse is triggered and the semiconductor switch is powered off. Thereby, the transmission of electrical energy to the load connected to the electrical switch is also interrupted, and the load is protected from overload. Instead of multiple loads, only one load, electrical appliance or subnet can also be connected to the electrical switch.

[0010] The danger when the semiconductor switch is overloaded is also that it can no longer be disconnected or is damaged during disconnection. This danger can be avoided by triggering the fuse, that is, avoiding switch failure and damage during the turn-off process, because the current passing through the fuse is turned off. After resetting or replacing the fuse, the electrical switch can be used again. In addition, the fuse also protects the load and the line connected to it from overload.

[0011] Overload or impending overload can be recognized by means of standards. For example, the overload can be determined according to the current value passing through the semiconductor switch or by evaluating the current value. Here, for example, it is also feasible to recognize overload or impending overload according to the temperature of the semiconductor of the semiconductor switch, especially the temperature of the drift layer. The current value can also be used for temperature determination, especially according to the temperature model.

[0012] The semiconductor switch is reliably protected from destruction or damage by the described method, so that after replacing or resetting the fuse and, if necessary, after eliminating the fault causing the overcurrent, it can continue to operate without replacing the expensive semiconductor switch.

[0013] Therefore, damage or destruction of the semiconductor switch can be avoided multiple times, thereby achieving significant cost savings. In addition, the fuse also has a second triggering option for the fuse, so there is redundancy for the semiconductor switch, and this redundancy ensures safe turn-off.

[0014] Another advantage of the electrical switch is that even in the case of a fault in the semiconductor switch, the electrical switch can achieve safe disconnection of the electrical switch. Then, by closing the circuit breaker and subsequent triggering, that is, disconnecting the fuse, the electrical appliance, load or the connected subnet can be disconnected from the energy source, the subnet is connected to the second interface of the electrical switch, and the energy source is connected to the first interface.

[0015] If the switch in the circuit breaker can cut off voltages of different polarities and can conduct currents of different polarities, which can be achieved in a simple manner by using two anti-series or anti-parallel connected semiconductors, then this switch can be used as an AC voltage switch for AC voltage applications or also as a DC voltage switch for DC voltage applications with two polarities.

[0016] Therefore, as long as the circuit breaker can prohibit voltages of different polarities and conduct currents of different polarities, the electrical switch can be used for applications that act as AC switches and DC switches for different polarities.

[0017] It has proven particularly advantageous that the fuse has a trigger threshold that has a current value that lies between the permanently permissible current value of the semiconductor switch and the maximum permissible value of the semiconductor switch. With this trigger value, the fuse can reliably and independently of each other perform multiple fuse functions. On the one hand, only the fuse has already avoided impermissibly high currents because such currents trigger the fuse. In addition, the semiconductor switch with such a device can be briefly overloaded at the same time because the trigger threshold is set high enough, i.e., above the permanently permissible current value of the semiconductor. Here, the load of the semiconductor can be monitored by means of a control / regulation or protection device. In response to the monitoring, the semiconductor switch can be disconnected. The circuit breaker is only used in the case of an overload, in which case the semiconductor switch would be damaged due to the disconnection. The circuit breaker drives such a high current through the fuse that the fuse is triggered, where this current is higher than the maximum permissible current value of the semiconductor switch.

[0018] Therefore, the particular advantage of this trigger threshold is that the overcurrent protection function of the fuse cooperates with the regulation that controls the circuit breaker and can thus perform protective intervention via the fuse.

[0019] Here, the energy source of the power grid should be high-performance especially in terms of its short-circuit power, such that a current greater than the maximum permissible current of the semiconductor switch can be generated.

[0020] In an advantageous design of the present invention, a further circuit breaker is provided between the second interface and the third interface. If the load has feedback energy or an energy storage device, it can also cause a current in the direction of the electrical switch from one or more loads. Then, a current is formed from the one or more loads via the semiconductor switch through the circuit breaker through the conducting circuit breaker. The further circuit breaker is used to exclude the current through the semiconductor switch from the load side. Here, when the circuit breaker is closed or closed, the further circuit breaker is at least temporarily closed. The closing of the further circuit breaker can thus be carried out simultaneously with the closing of the circuit breaker or with a time offset, so that the current from the energy source through the semiconductor switch and the further circuit breaker can be safely excluded.

[0021] Therefore, in order to protect the semiconductor switch, it has proven advantageous to close an additional circuit breaker as long as the connected load permits such a short circuit, in order to avoid or even completely eliminate the current flowing through the semiconductor switch.

[0022] In a further advantageous embodiment of the invention, the circuit breaker is designed as a thyristor. Thyristors are available on the market at low cost and at the same time have a very high short-term overload capacity. The thyristor is important so that a large short-circuit current can be conducted briefly without the circuit breaker, in this case the thyristor, being damaged. The disadvantage that the thyristor cannot interrupt the current is insignificant because the interruption is effected by the fuse, so that the current flowing through the thyristor stops after a short time.

[0023] If the circuit breaker is formed as a switch by means of an antiparallel thyristor pair, this switch can be used as an AC voltage switch and / or a DC voltage switch with two polarities.

[0024] In addition to thyristors, other switchable semiconductor elements can also be used, provided that the semiconductor element can carry a large short-circuit current and at the same time keep the voltage across it small enough.

[0025] In a further advantageous embodiment of the invention, an additional fuse is provided between the semiconductor switch and the second interface, so that a series circuit consisting of an additional circuit breaker and an additional fuse is provided between the second interface and the third interface. With this embodiment, two subnets can be connected to each other. In the event of a switch overload, the circuit breaker and the additional circuit breaker can be closed simultaneously, thus triggering the fuse and the additional fuse and interrupting the energy exchange between the two subnets. By closing the circuit breaker and the additional circuit breaker simultaneously, the semiconductor switch does not carry any short-circuit current and is thus no longer loaded, but instead quickly switches to a voltage-free and current-free state.

[0026] Furthermore, in this embodiment, the electrical switch is constructed symmetrically, so that the electrical switch is suitable in many respects for any combination of all applications, in particular subnets and appliances, and does not require any special adaptation. In addition, due to the presence of two fuses, there is redundancy, which makes the electrical switch particularly safe.

[0027] In a further advantageous design of the invention, when the circuit breaker is closed and when the current through the semiconductor switch exceeds a presettable limit value or when the magnitude of the current through the semiconductor switch exceeds a presettable limit value, a further circuit breaker is closed. Since closing the further circuit breaker can completely represent the loading of the connected load, it has proven advantageous that the further circuit breaker is only closed when the semiconductor switch is actually loaded by means of a load feedback. Here, the triggering is advantageously carried out as a function of the current through the semiconductor switch. If the measured current value or the magnitude of the measured current value or the effective value of the measured current value exceeds a presettable limit value, the further circuit breaker is closed as long as the circuit breaker is already closed. Description of the Drawings

[0028] In the following, the invention will be described and explained in more detail on the basis of the embodiments shown in the drawings. The drawings show:

[0029] Figure 1 and Figure 2 show an embodiment of an electrical device,

[0030] Figure 3 show an embodiment of a circuit breaker,

[0031] Figure 4 show a power grid, and

[0032] Figure 5 and Figure 6 show the time course of the variables of a semiconductor switch. Detailed Description of the Embodiment

[0033] Figure 1 An electrical switch 1 is shown. The electrical switch 1 has a first interface 11, a second interface 12 and a third interface 13. A series circuit consisting of a fuse 3 and a semiconductor switch 2 is arranged between the first interface 11 and the second interface 12. The semiconductor switch 2 has two semiconductors, which can each interrupt currents of different polarities. The electrical switch 1 can thus switch independently of the polarity, in particular interrupt the current i through the semiconductor switch 2 HL . A series circuit consisting of a fuse 3 and a circuit breaker 4 is arranged between the first interface 11 and the third interface 13. Here, the components fuse 3, semiconductor switch 2 and circuit breaker 4 form a star circuit. In the star circuit, these three components are connected to one another at the star point and are also each connected to the interfaces of the electrical switch 1. The first interface 11 and the third interface 13 are provided for connection to an energy source 7 (not shown here) or to a DC (direct current) bus feeding energy. The voltage between the second interface 12 or between the second interface 12 and the third interface 13 is provided for connection to a load or an electrical appliance. It is also possible for the interfaces to be connected to a subnet which has a plurality of loads or electrical appliances.

[0034] Figure 2 Another embodiment of the electrical switch 1 is shown. To avoid repetition, reference is made to the description of Figure 1 and the reference signs introduced therein. The electrical switch 1 has a further short-circuit breaker 41, which is arranged between the second interface 12 and the third interface 13 of the electrical switch 1. Thereby, the further short-circuit breaker 41 is arranged in parallel with the series circuit consisting of the semiconductor switch 2 and the short-circuit breaker 4. For simple connection to a power supply, in particular to an energy source 7 (not shown here) and a load, the electrical switch 1 has a power supply side interface, namely the first interface 11 and the third interface 13, and a load side interface, namely the second interface 12 and a further interface 14. Since the further interface 14 is fixedly coupled to the potential of the third interface 13, the further interface 14 can also be referred to as the third interface 13. There is also a further interface 14 outside the electrical switch for connection to an electrical appliance or a load. Only an electrical connection to the third interface 13 can be provided.

[0035] Furthermore, the electrical switch optionally has a further fuse 31 between the semiconductor switch 2 and the second interface 12. By means of this fuse, the first interface 11 and the second interface 12 are safely electrically disconnected from the semiconductor switch 2 in such a way that the short-circuit breaker 4 and the further short-circuit breaker 41 can be closed simultaneously in the event of an overload of the semiconductor switch.

[0036] The short-circuit breaker 4 and the further short-circuit breaker 41 are thyristors in this embodiment. If it can be assumed that the potential of the first interface 11 or the second interface 12 is always greater than or equal to the potential of the third interface 13, a single thyristor is sufficient. Conversely, if the third interface can also have a higher potential than the first interface 11 or the second interface 12, it is advantageous to use two thyristors arranged antiparallel to each other. Figure 3 Such an arrangement is shown. The electrical switch 1 having the short-circuit breaker 4 and / or the further short-circuit breaker 41 according to Figure 3 is implemented for use in a DC network, in which the polarity of the DC voltage can be changed, and for use in an AC voltage network.

[0037] Figure 4 A power grid 10 having an energy source 7 and an electrical switch 1 is shown. Here, the electrical switch 1 has the above-mentioned interfaces 11, 12, 13. The further interface 14 is arranged outside the electrical switch 1 here and is connected to the third interface 13 of the electrical switch 1. The second interface 12 and the further interface 14 form a load side interface for connection to one or more electrical appliances or loads or sub-networks.

[0038] Figure 5Shows the time variation curve of the temperature T of the semiconductor switch 2. For example, this temperature can be the temperature of the cutoff layer of the semiconductor, and the cutoff layer temperature is determined from measurement variables such as temperature values and / or currents by means of a calculation model. A criterion can be formed with the temperature, especially the cutoff layer temperature, by means of which an overload or an impending overload of the semiconductor switch 2 can be recognized.

[0039] In this example, the temperature T fluctuates, for example, according to the operating state and / or the load on the semiconductor switch 2. If the temperature T, for example, at time point t off,1 reaches a preset boundary value T Max , the circuit breaker 4 closes in order to generate a short-circuit current through the fuse 3 and to trigger the fuse 3. At the moment of triggering, the fuse 3 enters the open state. After the fuse 3 has been triggered, the temperature T drops because there is no longer any current-induced loading.

[0040] Figure 6 Shows the time variation curve of the magnitude of the current i through the semiconductor switch 2 HL . By triggering the circuit breaker 4, the feedback current of the load can also flow through the semiconductor switch 2 and the circuit breaker 4. Due to the short circuit, the magnitude of the current i HL increases. When the current reaches the boundary value I G , at time point t off,2 , another circuit breaker 41 closes and the feedback current no longer flows through the semiconductor switch 2 but through the other circuit breaker 41.

[0041] In summary, the present invention relates to an electrical switch having a first interface, a second interface and a third interface, a semiconductor switch, a fuse, a circuit breaker, wherein the series circuit formed by the fuse and the semiconductor switch is arranged between the first interface and the second interface, and the series circuit formed by the fuse and the circuit breaker is arranged between the first interface and the third interface. In other words, the present invention relates to an electrical switch for interrupting the current between a first interface and a second interface, having a third interface, a semiconductor switch, a fuse, a circuit breaker, wherein the series circuit formed by the fuse and the semiconductor switch is arranged between the first interface and the second interface, and the series circuit formed by the fuse and the circuit breaker is arranged between the first interface and the third interface, wherein the fuse has a triggering threshold, the triggering threshold having a current boundary value, wherein the current boundary value has a value between the persistent permissible current of the semiconductor switch and the maximum permissible current of the semiconductor switch. The present invention also relates to a power grid having at least one such electrical switch and an energy source, wherein the energy source is connected to the first interface and the third interface of the electrical switch. The present invention also relates to a method for operating such an electrical switch or such a power grid, wherein the circuit breaker is closed at least temporarily when the semiconductor switch is overloaded.

Claims

1. A power grid (10) having at least one electrical switch (1), a load, and an energy source (7), the electrical switch being for disconnecting the current between a first interface (11) and a second interface (12), wherein, The electrical switch (1) has: - a third interface (13), - a semiconductor switch (2), - a fuse (3), and - a circuit breaker (4), wherein the semiconductor switch (2) has two semiconductors which can respectively turn off currents of different polarities, wherein a series circuit composed of the fuse (3) and the semiconductor switch (2) is provided between the first interface (11) and the second interface (12), and a series circuit composed of the fuse (3) and the circuit breaker (4) is provided between the first interface (11) and the third interface (13), wherein another circuit breaker (41) is provided between the second interface (12) and the third interface (13), wherein the energy source (7) is connected to the first interface (11) and the third interface (13) of the electrical switch (1), wherein the load is connected to the second interface (12) and the third interface (13), and wherein the load is feedback-capable.

2. The power grid (10) according to claim 1, wherein, The circuit breaker (4) or the other circuit breaker (41) is designed as a thyristor.

3. The power grid (10) according to claim 1 or 2, wherein, Another fuse (31) is provided between the semiconductor switch (2) and the second interface (12), such that a series circuit composed of the other circuit breaker (41) and the other fuse (31) is provided between the second interface (12) and the third interface (13).

4. A method for operating an electrical switch (1) of a power grid (10) according to any one of claims 1 to 3, wherein, When the semiconductor switch (2) is overloaded, the circuit breaker (4) is at least temporarily closed, and when the circuit breaker (4) is closed or is in a closed state, the other circuit breaker (41) is at least temporarily closed.

5. The method according to claim 4, wherein, When the circuit breaker (4) is closed and when the current (i HL ) through the semiconductor switch (2) exceeds a preset boundary value (I G ) or when the magnitude of the current (i HL ) through the semiconductor switch (2) exceeds a preset boundary value (I G ), close the additional circuit breaker (41).

6. The method according to claim 4, wherein, The other circuit breaker (41) is closed simultaneously with the circuit breaker (4).

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