Switching device and method for operating a switching device
By introducing a parallel structure of mechanical bypass switches, unipolar and bipolar semiconductor switches into the switching device, the problem of shortened lifespan of mechanical switches during current commutation is solved, enabling faster current commutation and dielectric property recovery, and extending the service life of the switch.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- EATON INTELLIGENT POWER LTD
- Filing Date
- 2024-10-11
- Publication Date
- 2026-05-29
AI Technical Summary
Existing mechanical switches have a shortened lifespan due to arcing during current commutation, and semiconductor switches have a dynamic positive recovery problem, resulting in excessively long current commutation time.
A hybrid switching device is adopted, including a parallel structure of mechanical bypass switch, unipolar semiconductor switch and bipolar semiconductor switch. The switching of current in the switching device is controlled by the control unit, which shortens the current commutation time.
It effectively shortens the current commutation time, reduces the arc duration of mechanical switches, extends the service life of mechanical switches, and improves the recovery speed of air dielectric properties.
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Figure CN122122687A_ABST
Abstract
Description
Technical Field
[0001] This article describes a switching device and a method for operating the switching device. Background Technology
[0002] Switching devices are used to switch current lines. Specifically, if the switching device is in the closed state, current can flow between the first and second terminals connected by the current line, while if the switching device is in the open state, no current flows. For example, a switching device is a circuit breaker that protects circuits and / or electrical devices from electrical overload, such as an alternating current (AC) circuit breaker or a direct current (DC) circuit breaker.
[0003] For example, when using a mechanical switch to switch large currents, an electric arc may form between the mechanical contacts of the mechanical switch, potentially shortening its lifespan. Switching devices, such as hybrid switches or hybrid contact circuit breakers comprising mechanical switches and semiconductor switches connected in parallel, can be used to extend the lifespan of mechanical switches. For instance, during normal operation, current flows through a closed mechanical switch. In the event of an electrical overload, for example, the mechanical switch is opened and the semiconductor switch is closed, thereby commutating current from the mechanical switch to the semiconductor switch. The semiconductor switch is then opened to interrupt the current flow.
[0004] However, during current commutation, an electric arc forms between the contacts of the mechanical switch before the current finally commutates to the semiconductor switch. For example, current commutation occurs once the arc voltage of the mechanical switch exceeds the turn-on voltage of the semiconductor switch. The turn-on voltage, for example, is the threshold voltage of the transistor, diode, and / or other PN junction of the semiconductor switch. Specifically, the higher the turn-on voltage of the semiconductor switch, the longer it takes for current to commutate from the mechanical switch to the semiconductor switch, leading to increased wear on the mechanical contacts.
[0005] Furthermore, silicon PN junction power diodes and / or insulated-gate bipolar transistors (IGBTs), commonly used in semiconductor switches, may exhibit significant dynamic forward recovery problems, resulting in longer commutation times from mechanical switches to semiconductor switches. For example, when a diode turns on, its forward voltage first rises to the maximum turn-on voltage, then drops to a steady-state value after the forward recovery time, at which point the N-type doped region of the diode is fully charged with charge carriers. The maximum turn-on voltage can reach at least several hundred volts, while for a fast recovery diode with a maximum repetitive reverse voltage of 1200V, the forward recovery time can reach at least several hundred nanoseconds. Consequently, due to the dynamic forward recovery effect, the arcing duration of mechanical switches is longer, thus shortening their lifespan. Summary of the Invention
[0006] At least one objective of certain embodiments is to describe a switching device for shortening current commutation time. At least one further objective of certain embodiments is to describe a method for operating the switching device to shorten current commutation time. These objectives are achieved through the subject matter of the independent claims.
[0007] Further embodiments and other advantageous developments are described in the dependent claims.
[0008] According to an embodiment of a switching device for switching a current line between a first terminal and a second terminal, the switching device includes a mechanical bypass switch electrically connected between the first terminal and the second terminal. For example, the mechanical bypass switch is an arc switch without an arc-extinguishing mechanism. For example, the mechanical switch includes at least one mechanically movable contact for disconnecting and / or closing the current line between the first terminal and the second terminal.
[0009] According to another embodiment, the switching device includes a first semiconductor switch electrically connected in parallel with a mechanical bypass switch. For example, the first semiconductor switch is a unidirectional switch or a bidirectional switch. Specifically, a bidirectional switch can conduct current in both directions and / or can carry voltages of opposite polarity. For example, the first semiconductor switch includes, or is composed of, a semiconductor switching element, such as a transistor.
[0010] According to another embodiment, the switching device includes a second semiconductor switch electrically connected in parallel with the mechanical bypass switch and the first semiconductor switch. For example, the second semiconductor switch is a unidirectional switch or a bidirectional switch. For example, the second semiconductor switch includes a semiconductor switching element, such as a transistor, or is composed of such an element.
[0011] According to another embodiment of the switching device, the first semiconductor switch includes or is composed of a unipolar semiconductor switching element, and the second semiconductor switch includes or is composed of a bipolar semiconductor switching element.
[0012] For example, a unipolar semiconductor switching element comprises a stack of semiconductor layers that, during operation, utilize only one type of charge carrier—either electrons or holes—when guiding the main current through it. For example, during operation, when charge carriers of the main current flow through the semiconductor stack of the unipolar semiconductor switching element, they do not cross a PN junction. For example, compared to bipolar semiconductor switching elements, unipolar semiconductor switching elements have shorter switching times and / or lower switching losses. For example, unipolar semiconductor switching elements do not have a turn-on voltage. For example, a unipolar semiconductor switching element is a field-effect transistor.
[0013] For example, a bipolar semiconductor switching element comprises a stack of semiconductor layers that utilize both electrons and holes as charge carriers while guiding main current through them during operation. For example, during operation, charge carriers of the main current flow through the PN junction as they pass through the semiconductor stack of the bipolar semiconductor switching element. For example, compared to unipolar semiconductor switching elements, bipolar semiconductor switching elements exhibit lower conduction losses at high currents (e.g., at least 100 A or at least 1000 A). For example, the turn-on voltage of a bipolar semiconductor switching element is between 0.5 V and 2 V. For example, a bipolar semiconductor switching element is a bipolar junction transistor.
[0014] According to a preferred embodiment of a switching device for switching current lines between a first terminal and a second terminal, the switching device includes: - Mechanical bypass switch, electrically connected between the first and second terminals. - A first semiconductor switch, electrically connected in parallel with a mechanical bypass switch, and - A second semiconductor switch, electrically connected in parallel with the mechanical bypass switch and the first semiconductor switch, wherein... - The first semiconductor switch includes a unipolar semiconductor switching element and the second semiconductor switch includes a bipolar semiconductor switching element.
[0015] The switching device described herein is based on the concept of providing a hybrid circuit breaker that shortens the current commutation time from the mechanical bypass switch to the semiconductor switch when the mechanical bypass switch is disconnected. Advantageously, in the case of overload current, the shorter current commutation time reduces the arc duration when the mechanical bypass switch is disconnected, thereby extending the service life of the mechanical bypass switch.
[0016] For example, when switching the device from a closed state to an open state, the current first commutates from the mechanical bypass switch to the first semiconductor switch. Because the first semiconductor switch is a unipolar device with no turn-on voltage, the current commutation between the mechanical bypass switch and the first semiconductor switch is faster than commutating the current directly from the mechanical bypass switch to the second semiconductor switch, which is a bipolar device. However, due to its unipolar characteristics, the conduction loss of the first semiconductor switch may be higher than that of the second semiconductor switch, and therefore it may not be able to carry overload current for an extended period. Therefore, the current is further commutated from the first semiconductor switch to the second semiconductor switch, and then the second semiconductor switch is turned off, thereby electrically disconnecting the first and second terminals.
[0017] Furthermore, the switching device described herein can improve the recovery speed of the dielectric properties of the air or ambient atmosphere surrounding the mechanical bypass switch. Specifically, by shortening the arc duration, less energy is dissipated in the arc. Therefore, in the event of an overvoltage across the contacts caused by the clamping device, the faster recovery of the dielectric properties of the air or ambient atmosphere can prevent the arc from reigniting.
[0018] Advantageously, the unipolar first semiconductor switch can be connected in parallel with the mechanical bypass switch in a particularly compact manner to reduce stray inductance in the current commutation circuit. For example, during current commutation, if the time derivative of the current is large, the voltage drop across the stray inductance will cause the voltage drop to be proportional to the derivative multiplied by the stray inductance, which may increase the current commutation time. Therefore, reducing stray inductance can advantageously shorten the current commutation time.
[0019] According to another embodiment of the switching device, the bipolar semiconductor switching element is an insulated gate bipolar transistor (IGBT). For example, an IGBT includes a semiconductor layer stack having a vertical bipolar junction transistor electrically connected to a surface-channel field-effect transistor. Here, "vertical" refers to a direction perpendicular to the main extending plane of the semiconductor layers of the semiconductor layer stack.
[0020] According to another embodiment of the switching device, the second semiconductor switch includes a freewheeling diode connected in anti-parallel to the bipolar switching element. For example, in a bidirectional semiconductor switch, the freewheeling diode conducts current in the opposite direction to the IGBT. Alternatively, the freewheeling diode may be configured as a blocking diode to prevent the IGBT from operating in a certain quadrant of the switching device.
[0021] According to another embodiment of the switching device, the freewheeling diode is a PN-combined Schottky diode, particularly a silicon carbide PN-combined Schottky diode. For example, the PN-combined Schottky diode combines the characteristics of a Schottky diode for current flow under normal operating conditions with the characteristics of a PN junction diode for surge current flow. Therefore, for example, compared to a PN junction diode, the PN-combined Schottky diode can advantageously withstand higher surge current densities and has a higher operating junction temperature. Silicon carbide has a wider bandgap than silicon, thereby allowing the breakdown voltage of the freewheeling diode to be increased to, for example, higher voltages.
[0022] Specifically, a PN-combined Schottky diode is a unipolar diode in which current does not pass through the PN junction during normal operation. Therefore, a PN-combined Schottky diode does not have a turn-on voltage. Furthermore, for example, compared to a PN junction diode, the dynamic forward recovery problem of a PN-combined Schottky diode is less pronounced, thus shortening the current commutation time.
[0023] According to another embodiment of the switching device, the second semiconductor switch includes a first insulated-gate bipolar transistor (IGBT) and a second IGBT as bipolar semiconductor switching elements. The first IGBT and the second IGBT are connected in anti-series configuration with either a common-emitter or common-collector configuration. For example, the second semiconductor switch is a bidirectional switch. For example, the second semiconductor switch includes a first IGBT, a second IGBT, a first freewheeling diode, and a second freewheeling diode, or a combination thereof. Specifically, the first freewheeling diode is connected in anti-parallel to the first IGBT, and the second freewheeling diode is connected in anti-parallel to the second IGBT. The first IGBT and the second IGBT are connected in series with a common-emitter configuration, wherein the emitter of the first IGBT is connected to the emitter of the second IGBT; or the first IGBT and the second IGBT are connected in series with a common-collector configuration, wherein the collector of the first IGBT is connected to the collector of the second IGBT. Therefore, if the second semiconductor switch is in the closed state, current flows through the first IGBT and the second freewheeling diode in one direction and through the second IGBT and the first freewheeling diode in the opposite direction.
[0024] According to another embodiment of the switching device, the unipolar semiconductor switching element is a field-effect transistor, particularly a silicon carbide field-effect transistor. For example, the unipolar semiconductor switching element is a metal-oxide-semiconductor field-effect transistor (MOSFET), particularly a silicon carbide MOSFET; or a junction-gate field-effect transistor (JFET), particularly a silicon carbide JFET.
[0025] According to another embodiment of the switching device, the first semiconductor switch includes a first field-effect transistor and a second field-effect transistor as unipolar semiconductor switching elements, wherein the first field-effect transistor and the second field-effect transistor are connected in series in a common-source configuration or a common-drain configuration. For example, the first semiconductor switch is a bidirectional switch.
[0026] According to another embodiment, the switching device further includes a mechatronic disconnect switch connected in series with a mechanical bypass switch, a first semiconductor switch, and a second semiconductor switch. For example, when the switching device is changed from a closed state to an open state, the mechatronic disconnect switch is disconnected after the mechanical bypass switch and the first and second semiconductor switches have been opened, for example, once the current approaches zero amperes. For example, the mechatronic disconnect switch is also connected in series with a voltage clamping system, which may be part of the switching device and is described in more detail below.
[0027] According to another embodiment, the switching device further includes a voltage clamping system electrically connected in parallel with a mechanical bypass switch, a first semiconductor switch, and a second semiconductor switch. For example, the voltage clamping system is configured to limit voltage rise due to energy stored in the lines and stray inductance when the semiconductor switches are open. For example, the voltage clamping system allows the voltage to rise to an allowable magnitude that is much greater than the source voltage and less than the breakdown voltage of the semiconductor switches. For example, the voltage clamping system includes or is composed of elements such as a varistor, particularly a metal oxide varistor (MOV), a transient voltage suppressor (TVS), and / or a buffer circuit.
[0028] According to another embodiment, the switching device includes a control unit for operating a mechanical bypass switch, a first semiconductor switch, and a second semiconductor switch. The control unit can further operate an electrical disconnect switch. For example, when switching the switching device from a closed state to an open state during operation, the control unit first closes the first semiconductor switch and opens the second semiconductor switch while the mechanical bypass switch is still closed.
[0029] For example, the control unit then disconnects the mechanical bypass switch, causing the current flowing between the first terminal and the second terminal to be immediately or almost immediately switched to the first semiconductor switch due to the absence of an on-state voltage in the first semiconductor switch.
[0030] For example, in a subsequent step, the control unit opens the first semiconductor switch and closes the second semiconductor switch, allowing current to be further commutated from the first semiconductor switch to the second semiconductor switch. Specifically, the second semiconductor switch is closed before the first semiconductor switch is opened. For example, compared to the first semiconductor switch, the second semiconductor switch can withstand surge current for a longer period of time due to its bipolar characteristics.
[0031] In another step, the control unit disconnects the second semiconductor switch, for example, by placing the switching device in an open state. For example, once the switching device is in the open state, current can still flow between the first and second terminals via a voltage clamping system due to energy stored in the circuitry and stray inductance of the switching device. For example, once the stored energy is dissipated, the current flow between the first and second terminals ceases.
[0032] For example, during the switching process from a closed state to an open state, the first semiconductor switch is in an on or closed state for up to ten microseconds, which reduces the thermal stress on the first semiconductor switch.
[0033] Furthermore, this document describes a method for operating a switching device. Specifically, the method is configured to operate the switching device as detailed above. All features of the switching device are also disclosed in the method for operating the switching device, and vice versa.
[0034] According to an embodiment of a method for operating a switching device, the switching device is used to switch a current line between a first terminal and a second terminal. The switching device includes a mechanical bypass switch electrically connected between the first and second terminals, a first semiconductor switch electrically connected in parallel with the mechanical bypass switch, and a second semiconductor switch electrically connected in parallel with both the mechanical bypass switch and the first semiconductor switch. The first semiconductor switch includes a unipolar semiconductor switching element, and the second semiconductor switch includes a bipolar semiconductor switching element. The method includes the step of disconnecting the electrical connection between the first and second terminals using the following steps: a) When the mechanical bypass switch is closed, the first semiconductor switch is closed and the second semiconductor switch is opened. b) Disconnect the mechanical bypass switch. c) Close the second semiconductor switch and open the first semiconductor switch. d) Disconnect the second semiconductor switch. Steps a) through d) are performed in the order specified above.
[0035] According to another embodiment of the method, during steps b) and c), the first semiconductor switch remains in the on or closed state for up to 10 microseconds.
[0036] According to another embodiment, the method includes the further step of closing the electrical connection between the first terminal and the second terminal, wherein the second semiconductor switch, the first semiconductor switch, and the mechanical bypass switch are closed sequentially. Specifically, before closing the electrical connection, the second semiconductor switch, the first semiconductor switch, and the mechanical bypass switch are all in an open state. Subsequently, for example, the second semiconductor switch is closed before the first semiconductor switch is closed, and the mechanical bypass switch is closed last. Specifically, after the mechanical bypass switch has reached a mechanically stable closed position, the first and second semiconductor switches are opened again.
[0037] Using the first semiconductor switch as described above during the closure of the electrical connection between the first and second terminals can advantageously reduce the contact bounce effect of the mechanical bypass switch during contact closure, because the first semiconductor switch has an almost zero turn-on voltage, for example, due to its unipolar characteristics, compared to the second semiconductor switch. Attached Figure Description
[0038] Further advantageous and additional embodiments of the switching device and its operating method will become apparent from the exemplary embodiments described below in conjunction with the accompanying drawings.
[0039] Figure 1 A schematic circuit diagram of a switching device according to an exemplary embodiment is shown.
[0040] Figure 2A schematic flowchart illustrating a method for operating a switching device according to an exemplary embodiment is shown.
[0041] In the figures, identical, similar, or having the same effect are represented by the same reference numerals. These figures and the scales of the elements shown in them should not be considered true scale. Rather, for better representation and / or better understanding, individual elements may be enlarged. Detailed Implementation
[0042] according to Figure 1 The exemplary embodiment of the switching device 1 includes a mechanical bypass switch 4, a first semiconductor switch 51, a second semiconductor switch 52, and a mechanical-electrical disconnect switch 6 configured to switch the current line 2 between a first terminal 31 and a second terminal 32. The states of all switches 4, 51, 52, and 6 of the switching device 1 are controlled and / or monitored by a control unit 8. Specifically, the switching device 1 is a bidirectional hybrid circuit breaker configured to electrically isolate the first terminal 31 from the second terminal 32, for example, in the event of overload, short circuit, and / or surge current, by changing the switching device 1 from a closed state to an open state.
[0043] The mechanical bypass switch 4 includes mechanically movable contacts for opening and / or closing the mechanical bypass switch 4. For example, the mechanical bypass switch 4 is a mechanical circuit breaker.
[0044] The first semiconductor switch 51 consists of a first field-effect transistor 511 and a second field-effect transistor 512, which are unipolar semiconductor switching elements 511. The first field-effect transistor 511 and the second field-effect transistor 512 are connected in series in a common-source configuration. Both the first field-effect transistor 511 and the second field-effect transistor 512 are N-channel MOSFETs, particularly silicon N-channel MOSFETs or silicon carbide N-channel MOSFETs. Due to the unipolar characteristics of MOSFETs 511 and 512, the turn-on voltage of MOSFETs 511 and 512 is almost zero, thus offering the advantage of no current commutation delay compared to bipolar transistors, for example.
[0045] The second semiconductor switch 52 comprises a first insulated-gate bipolar transistor (IGBT) 521 and a second IGBT 522, which are bipolar semiconductor switching elements 521, as well as a first freewheeling diode 523 and a second freewheeling diode 524. The first IGBT 521 and the second IGBT 522 are connected in anti-series configuration with a common emitter. The first freewheeling diode 523 is connected in anti-parallel to the first IGBT 521, and the second freewheeling diode 524 is connected in anti-parallel to the second IGBT 522. Specifically, the first freewheeling diode 523 and the second freewheeling diode 524 are configured to conduct reverse current, which would otherwise be blocked by the first IGBT 521 or the second IGBT 522, respectively.
[0046] Both the first IGBT 521 and the second IGBT 522 are silicon IGBTs, while the first freewheeling diode 523 and the second freewheeling diode 524 are both silicon carbide PN-combined Schottky diodes. Advantageously, the silicon carbide PN-combined Schottky diode is a unipolar device, therefore its turn-on voltage is almost zero and it has no current commutation delay. Furthermore, compared to PN junction diodes, the silicon carbide PN-combined Schottky diode does not have a dynamic forward recovery problem. Therefore, compared to PN junction diodes, the silicon carbide PN-combined Schottky diode shortens the current commutation time.
[0047] Furthermore, the voltage clamping system 7, in the form of a metal oxide rheostat, is electrically connected in parallel with the mechanical bypass switch 4, the first semiconductor switch 51, and the second semiconductor switch 52. The mechanical-electrical disconnect switch 6 is electrically connected in series with the mechanical bypass switch 4, the first semiconductor switch 51, the second semiconductor switch 52, and the voltage clamping system 7.
[0048] Figure 2 A flowchart illustrating steps S1, S2, S3, S4, and S5 of a method for operating a switching device 1 according to an exemplary embodiment is shown. For example, the method is configured to combine... Figure 1 The described switching device 1 switches from a closed state to an open state, wherein the first terminal 31 and the second terminal 32 are electrically isolated from each other in the open state.
[0049] In the first step S1, the first semiconductor switch 51 is closed and the second semiconductor switch 52 is open, while the mechanical bypass switch 4 and the mechanical-electrical isolation switch 6 remain closed. For example, the first semiconductor switch 51 is closed by applying a sufficiently large positive gate-source voltage to the first MOSFET 511 and the second MOSFET 512, while the second semiconductor switch 52 is open by not applying a gate-emitter voltage to the first IGBT 521 and the second IGBT 522.
[0050] In the second step S2, the mechanical bypass switch is turned off, so that the current flowing between the first terminal 31 and the second terminal 32 is immediately switched to the first semiconductor switch 51 because there is no turn-on voltage on the first semiconductor switch 51.
[0051] In the third step S3, the first semiconductor switch 51 is turned off and the second semiconductor switch 52 is closed, allowing current to be further commutated from the first semiconductor switch 51 to the second semiconductor switch 52. Specifically, the second semiconductor switch 52 is closed before the first semiconductor switch 51 is turned off. For example, during steps S2 and S3, for instance, to reduce thermal stress on the first semiconductor switch 51, the first semiconductor switch 51 may remain closed or in an on state for only a few microseconds (e.g., up to 10 microseconds).
[0052] In the fourth step S4, the second semiconductor switch 52 is turned off, placing the switching device 1 in the off state and eliminating current flow between the first terminal 31 and the second terminal 32. Alternatively, for a short time after the switching device 1 is switched to the off state, current may continue to flow between the first and second terminals via the voltage clamping system 7. For example, current may flow via the voltage clamping system 7 until the energy stored in the circuitry and stray inductance of the switching device 1 is dissipated.
[0053] In the fifth step S5, the mechanical-electric disconnect switch 6 is disconnected, so that the first terminal 31 and the second terminal 32 are electrically isolated.
[0054] This invention is not limited to the specific embodiments described in the specification based on these exemplary embodiments. Rather, this invention covers any new features and any combination of features, particularly any combination of features in the patent claims and any combination of features in the exemplary embodiments, even if the feature or combination itself is not expressly described in the patent claims or exemplary embodiments.
[0055] Figure Labels
[0056] 1 Switching device
[0057] 2 Current lines
[0058] 31 First terminal
[0059] 32 Second terminal
[0060] 4 Mechanical bypass switch
[0061] 51 First Semiconductor Switch
[0062] 511 Unipolar Semiconductor Switching Element
[0063] 512 Second Field-Effect Transistor
[0064] 52 Second Semiconductor Switch
[0065] 521 Bipolar Semiconductor Switching Element
[0066] 522 Second Insulated Gate Bipolar Transistor
[0067] 523 freewheeling diode
[0068] 524 Second Freewheeling Diode
[0069] 6 Mechanical-electric disconnect switch
[0070] 7 Voltage clamping system
[0071] 8 Control Unit
[0072] S1 First Step
[0073] S2 Second Step
[0074] S3 Third Step
[0075] S4, the fourth step.
Claims
1. A switching device (1) for switching a current line (2) between a first terminal (31) and a second terminal (32), the switching device (1) comprising: -Mechanical bypass switch (4), electrically connected between the first terminal (31) and the second terminal (32), - A first semiconductor switch (51) is electrically connected in parallel with the mechanical bypass switch (4), and - A second semiconductor switch (52) is electrically connected in parallel with the mechanical bypass switch (4) and the first semiconductor switch (51), wherein, - The first semiconductor switch (51) includes a unipolar semiconductor switching element (511), and the second semiconductor switch (52) includes a bipolar semiconductor switching element (521).
2. The switching device (1) according to the preceding claim, wherein, The bipolar semiconductor switching element (521) is an insulated gate bipolar transistor.
3. The switching device (1) according to any one of the preceding claims, wherein, The second semiconductor switch (52) includes a freewheeling diode (523) that is connected in antiparallel to the bipolar semiconductor switching element (521).
4. The switching device (1) according to the preceding claim, wherein, The freewheeling diode (523) is a PN-combined Schottky diode, particularly a silicon carbide PN-combined Schottky diode.
5. The switching device (1) according to any one of the preceding claims, wherein, The second semiconductor switch (52) includes a first insulated gate bipolar transistor (521) and a second insulated gate bipolar transistor (522), wherein the first insulated gate bipolar transistor (521) serves as the bipolar semiconductor switch element (521), and the first insulated gate bipolar transistor and the second insulated gate bipolar transistor are connected in anti-series configuration in either a common emitter configuration or a common collector configuration.
6. The switching device (1) according to any one of the preceding claims, wherein, The unipolar semiconductor switching element (511) is a field-effect transistor, particularly a silicon carbide field-effect transistor.
7. The switching device (1) according to any one of the preceding claims, wherein, The first semiconductor switch (51) includes a first field-effect transistor (511) and a second field-effect transistor (512), the first field-effect transistor (511) serving as the unipolar semiconductor switch element (511), and the first field-effect transistor (511) and the second field-effect transistor (512) being connected in series in a common-source configuration or a common-drain configuration.
8. The switching device (1) according to any one of the preceding claims further includes a mechanical-electric disconnect switch (6), the mechanical-electric disconnect switch (6) being connected in series with the mechanical bypass switch (4), the first semiconductor switch (51) and the second semiconductor switch (52).
9. The switching device (1) according to any one of the preceding claims further includes a voltage clamping system (7) electrically connected in parallel with the mechanical bypass switch (4), the first semiconductor switch (51) and the second semiconductor switch (52).
10. A method for operating a switching device (1) for switching a current line (2) between a first terminal (31) and a second terminal (32), the switching device (1) comprising a mechanical bypass switch (4) electrically connected between the first terminal (31) and the second terminal (32), a first semiconductor switch (51) electrically connected in parallel with the mechanical bypass switch (4), and a second semiconductor switch (52) electrically connected in parallel with the mechanical bypass switch (4) and the first semiconductor switch (51), wherein, The first semiconductor switch (51) includes a unipolar semiconductor switching element (511) and the second semiconductor switch (52) includes a bipolar semiconductor switching element (521), wherein the method includes the step of disconnecting the electrical connection between the first terminal (31) and the second terminal (32) using the following steps: a) When the mechanical bypass switch (4) is closed, the first semiconductor switch (51) is closed and the second semiconductor switch (52) is opened. b) Disconnect the mechanical bypass switch (4). c) Close the second semiconductor switch (52) and open the first semiconductor switch (51). d) Disconnect the second semiconductor switch (52). Steps a) through d) are performed in the order specified above.
11. The method according to the preceding claim, wherein, During steps b) and c), the first semiconductor switch (51) remains on for up to 10 microseconds.
12. The method according to claim 10 or 11, further comprising the step of closing the electrical connection between the first terminal (31) and the second terminal (32), wherein, The second semiconductor switch (52), the first semiconductor switch (51), and the mechanical bypass switch (4) are closed sequentially.