Hybrid switch and method for controlling a hybrid switch

Abstract

The invention relates to a hybrid switch (1, 100, 200) comprising a switching structure having at least a first section (10, 110) that has at least the following three components (20, 30, 40, 120, 130, 140) connected in parallel: i) at least one mechanical switching device (20, 120, 220) having a first switching path (21) with at least one contact point (22), wherein at least the switching path (21) is encapsulated in a switching chamber (23, 123, 223) filled with a filling gas (24) that has a higher energy absorption and preferably a higher electrical disruptive strength than air; ii) at least one semiconductor switching device (30, 130, 230) having a semiconductor switching path (31), and iii) a residual energy absorption device (40, 140, 240) having a threshold voltage selected such that it lies between a maximum operating voltage of the circuit and a dielectric strength of the semiconductor switching device (30). The switching structure furthermore comprises a second section (50, 150) that is connected in series with the first section (10, 110) and that has a mechanical isolating switch (50a, 50b) having a second switching path (51) for at least one-off isolation of the circuit. The invention furthermore relates to a switching method and to a control apparatus (60).

Description

[0001] Hybrid switches and methods for controlling a hybrid switch

[0002] The invention relates to a hybrid switch and a corresponding method for switching an electrical circuit, in particular a direct current circuit with an operating voltage of at least 600 V and an operating current of at least 100 A.

[0003] An electrical circuit serves to supply at least one load with electricity. During operation, the circuit is closed using a switching device. When the load, e.g., a lamp, is no longer needed, the circuit is opened using the switching device, thus interrupting the current. At low voltages and low currents, the circuit can still be switched with minimal arcing without special measures.

[0004] At higher voltages, especially when combined with higher currents, the current continues to flow when the contacts or electrodes of, for example, a mechanical switching device open, initially in the form of a spark discharge or an arc discharge. Depending on the current, voltage, prevailing pressure, and electrode material, a stable switching arc (hereinafter referred to simply as an arc) forms at approximately 14 V and 1 A. Upon contact separation, the current density initially increases or concentrates at the last contact point. As the contacts open further, the arc then forms between these last contact points. This is caused by the low dielectric strength of the insulating material between the initially not yet fully opened contacts. The insulating material, often air, is ionized and thus becomes electrically conductive.

[0005] Opening the contacts is particularly problematic with inductive loads (e.g., motors, coils, electromagnets, transformers), which store energy in the form of the magnetic field of the inductance. Here, a sudden interruption of the circuit causes the stored energy to continue flowing, with the voltage across the contacts instantly rising to very high values ​​upon opening, potentially creating a switching arc.

[0006] The electric arc is an additional resistance in the circuit and, although it consumes the energy still present or stored in the circuit, it generally poses a problem. The voltage rises without exceeding the source voltage. Due to the high thermal energy that the arc introduces into the surrounding media, contact erosion, even destruction of the contacts and the switching chamber, can occur within a very short time. Therefore, to prevent this, the arc should be extinguished very quickly. In any case, interference emissions and contact wear occur. With alternating current, the current direction changes in rhythm with the frequency. This means the current has a natural zero crossing, and a resulting arc extinguishes itself. In an alternating current circuit, an arc is therefore usually not a problem. With direct current, however, the current direction does not change. There are no natural current zero crossings.Therefore, the possibility of independent deletion is eliminated.

[0007] The switching arc must therefore be extinguished by additional measures. To extinguish the arc, the arc voltage must be increased to a level above the source voltage; then the arc breaks. In a mechanical switching system, the necessary voltage increase for extinguishing the arc can be achieved in two ways: by lengthening the arc or by reducing its energy through forced cooling. Both measures have certain disadvantages. Lengthening the arc typically increases the contact gap, which, among other things, increases the component dimensions, especially at high voltages and high currents. Intensive cooling consumes energy, requires additional installation space, and is expensive.

[0008] To switch the current flow in a circuit with as little arcing as possible, or even without arcing at all—that is, with an arc that burns only so briefly that it causes little to no significant damage—semiconductor switches can be used in parallel. Semiconductor switches, as the name implies, consist of semiconductors. Semiconductors are solids that can be described as both conductors and insulators with regard to their electrical conductivity. Their conductivity is strongly temperature-dependent. Depending on the temperature, they are less conductive than equivalent metal conductors, such as copper or aluminum. At certain temperatures, when connected in parallel to a copper or aluminum conductor in a circuit, they form a path that exhibits a very high ohmic resistance, depending on the temperature.They are therefore generally not well-suited for conducting current with low resistance during normal operation (unless they are and remain appropriately temperature-controlled, which can be complex). For this reason, so-called "hybrid switches" were developed, which combine a mechanical switching element, e.g., a mechanical switching device (relay), and a semiconductor switching element connected in parallel. Hybrid switches thus combine the advantages of both principles: a mechanical conductor that carries the current during operation and a semiconductor that carries the current at the moment of switching. A disadvantage of a semiconductor switch is that the very fast electronic switching processes necessitate additional components for overvoltage protection.

[0009] In normal operation, the operating current in hybrid switches always flows through the mechanical switching path due to its lower resistance when the contacts are closed. When the mechanical contact(s) open, the current flows through the semiconductor switching path as soon as the electrical resistance in the mechanical switching path is greater than in the semiconductor switching path. This switching of the current path is commonly known as "commutation." After successful commutation, the current in the semiconductor switching path is defined and forced to zero without arcing.

[0010] An RC circuit can then be used in parallel with the mechanical contact to limit the voltage rise at the moment of opening. This dampens the current (so-called "snubber circuit"). This circuit is often referred to as spark quenching in switching contacts.

[0011] In the off state, reliable isolation is only achieved through a sufficient air or gas gap. Therefore, for safety reasons, an additional mechanical switching link is typically provided to reliably interrupt the current in the event of a fault by means of a sufficient isolation gap and / or air gap.

[0012] One problem with existing hybrid switches is their price and lifespan. Extending their lifespan, i.e., increasing the number of possible switching cycles, has always been associated with significantly higher costs. While semiconductor switches exist that can handle higher operating voltages and simultaneously high operating currents (such as those required in electric vehicles, electric machines, etc.), the cost of a single such switch is already enormous. Typically, a system requires a large number of these switches. Examples of more complex switches are provided by US 2016 / 0285250 A1, which discloses a high-voltage DC circuit breaker and a corresponding method, and CN 1 17 578 380 A, which discloses a combined energy dissipation device based on a liquid metal energy collector.The subsequently published DE 10 2023 206 561 A1 also shows an electronic arrangement with a switching device comprising n series-connected semiconductor switching units, a voltage limiting device connected in parallel to the switching device, including at least one overvoltage protection component and at least one diac connected in series with the overvoltage protection component, and n surge arresters connected in parallel to the semiconductor switching units. Unfortunately, the price usually increases with the complexity of the switches.

[0013] It is an object of the present invention to provide an improved, more cost-effective hybrid switch with which operating voltages of at least 600 V and operating currents of at least 100 A can be switched permanently largely without contact damage.

[0014] This problem is solved by a hybrid switch according to claim 1, a method according to claim 17 and a control device according to claim 19.

[0015] The hybrid switch mentioned above is designed to switch a circuit with an operating voltage of at least 600 V and an operating current of at least 100 A. For example, the hybrid switch can be designed to switch a circuit, in particular a DC circuit, with an operating voltage between 600 and 1500 V and an operating current between 100 and 600 A.

[0016] Preferably, it can even be designed so that, under the aforementioned minimum conditions, it can switch the circuit largely continuously, i.e., for a certain minimum duration of at least one thousand switching cycles. Afterward, it can be stipulated that the switch or individual components should be replaced preventively as a safety precaution to minimize the risk of switch failure, ideally at which point the components should not yet have reached their actual service life.

[0017] The hybrid switch is particularly advantageous for use in a direct current (DC) circuit. This is because DC current does not periodically change its polarity, as is the case with alternating current (AC). Therefore, a switching arc that forms in a DC circuit does not extinguish itself automatically; rather, above a certain current and voltage, certain measures are required to extinguish the arc. With AC current, the polarity of the current direction changes periodically over time, with the current passing through a zero crossing at each change of direction. This zero crossing extinguishes any existing switching arc after a short time. Thus, a switching arc does not persist with AC current. These zero crossings are absent in DC current, which is why it is necessary to extinguish the switching arc by other means.

[0018] The hybrid switch is designed in such a way that it can handle not just one or a few switching operations, but preferably at least a thousand switching operations; that is, it is not a typical emergency switch or the like, which is deliberately designed to withstand only one or a few switching operations, and therefore already suffers irreparable damage and must be replaced.

[0019] The hybrid switch comprises a switching arrangement with A) at least one first section, which has at least the following three components connected in parallel. i) One of the parallel-connected components forms at least one mechanical switching device with a first switching section that includes at least one contact point. At the contact point, the circuit can be opened by the switching device by moving the contacts touching at the contact point apart, or closed again by bringing the contacts together at the contact point when the contacts at the contact point are just separated. It is also possible for the mechanical switching device to have several contact points connected in series, as will be explained further below.

[0020] In principle, the mechanical switching device is advantageously designed in such a way that the electrical voltage rises as quickly as possible when the switching device is switched off or opened.

[0021] In this configuration, at least the switching section of the switching device is encapsulated in a switching chamber filled with a gas that has a higher energy absorption capacity and preferably also a higher dielectric strength compared to air. The switching device thus has an encapsulation in which the switching process normally takes place in the absence of oxygen. ii) At least one further component connected in parallel is a semiconductor switching device with a semiconductor switching section. As mentioned above, semiconductors are well suited for switching; however, they are generally poor conductors, i.e., poorly conductive under certain conditions, and therefore exhibit a relatively high electrical resistance. In normal operation, the current therefore does not flow through the semiconductor switching device, since its resistance is significantly higher than that of the mechanical switching device.For the current to commutate to the semiconductor switching device, the resistance in the mechanical switching device must therefore be increased sufficiently so that it is higher than in the semiconductor switching device. The resistance increases when the voltage between the contacts in the mechanical switching device increases. If the voltage, and thus the resistance for the current through the mechanical switching device, is high enough, i.e., higher than in the semiconductor switching device, the current commutates to the semiconductor switching device. iii) A further component connected in parallel forms a residual energy absorption device with a threshold voltage chosen to lie between the maximum operating voltage of the circuit and the dielectric strength of the semiconductor switching device.

[0022] Furthermore, the hybrid switch comprises a second section connected in series with the first section, containing a mechanical disconnect switch with a second switching path for at least one-time disconnection, decoupling, or galvanic isolation of the circuit. Preferably, the disconnect switch can also serve to disconnect or switch off the circuit in section B after the switching operation in the first section, without a load. The second switching path of the disconnect switch preferably has a contact gap of at least 3 mm in the disconnected state. Alternatively, the disconnect switch can be designed as a DC disconnect switch with a magnetic field and a hydrogen-nitrogen mixture with an opening (or closing) time of 10–15 ms. The at least one electrical load can, for example, be connected between the two poles of the two-pole disconnect switch, thus providing additional protection for the load.Another possible configuration of the disconnect switch is explained further below. Usually (and preferably), the second section is connected in series with the first, but it could also be connected upstream.

[0023] An inventive method for controlling a hybrid switch for switching an electrical circuit, i.e., for opening when the circuit is closed or for closing when the circuit is interrupted (this variant is discussed further below), in particular a direct current circuit, comprises at least the following method steps:

[0024] In step i), two electrical contacts are initially opened at at least one contact point in a first switching section of a mechanical switching device. At least the switching section of the mechanical switching device is encapsulated in a switching chamber filled with a gas that has a higher energy absorption capacity than air. When the mechanical switching section opens, the anode-fall and cathode-fall voltages typically build up first.

[0025] In a further step ii), the current then commutates from the mechanical switching device to a parallel-connected semiconductor switching device (as soon as the resistance in the mechanical switching device is greater than in the semiconductor switching device). The semiconductor switching device comprises a semiconductor switching path, which may, for example, have several terminals, such as a control terminal. The terminals differ in their designation and properties depending on the type of semiconductor switching device. This further step occurs automatically when the mechanical switching device is opened and the semiconductor switching device is still conducting.

[0026] In a further step iii), the semiconductor switching device in the semiconductor switching path, particularly at the electrical terminals, is "opened" or switched to "block" mode after the mechanical switching device has been opened. "Blocking" here means that no significant current flows between the terminals, i.e., if any, only a negligible current. Since this interruption of the current flow is analogous to opening a mechanical switching device, the "blocking" can, for the sake of simplicity, also be referred to as "opening" the semiconductor switching device. In a further, final step iv), the residual energy still present in the circuit is absorbed or dissipated in a residual energy absorption device connected in parallel to both the mechanical switching device and the semiconductor switching device.The residual energy absorption device has a threshold voltage that is selected to lie between the maximum operating voltage of the circuit and the dielectric strength of the semiconductor switching device. This step also occurs automatically when the mechanical switching device is opened and the semiconductor switching device is opened or closed.

[0027] Preferably, in a further step after step iv), a disconnect switch can separate the circuit, wherein the disconnect switch is located, as already mentioned, in a second section which is connected in series to a first section in which the mechanical switching device, the semiconductor switching device and the residual energy absorption device are connected in parallel to each other in the first section.

[0028] In principle, the hybrid switch can also be used to switch an electrical circuit on or off. Therefore, in the individual process steps i) and iii) of the claims, in addition to opening the mechanical switching device and "opening" or "locking" the semiconductor switching device, "closing" (corresponding to "allowing" the current in the case of the semiconductor switching device) is also mentioned as an alternative. However, since the issue of the formation of a switching arc is generally unproblematic or does not occur when "closing," this case will not be discussed further here.

[0029] The advantage of a switching junction encapsulated in a switching chamber filled with a gas that has a higher energy absorption capacity than air is that the voltage across the junction builds up more quickly after the aforementioned anode-fall and cathode-fall voltages (than without encapsulation in air). At the same time, the switching junction, particularly the contact point, can be protected from oxidation by the exclusion of oxygen provided by the gas, thus reducing wear and extending its lifespan. This allows the use of copper as the contact material, which has the advantage of very low contact resistance. It also reduces wear on the mechanical contacts, further extending their service life. This enables faster commutation onto the semiconductor, which is a key aspect of the invention.With hydrogen as the filling gas, the voltage rises approximately ten times faster compared to air, for example. Experiments have shown that this is particularly true for a time interval of 0.5 ms after opening.

[0030] In current embodiments of the invention, for example, the threshold voltage of the residual energy absorption device can be approximately 1000 V, the maximum operating voltage of the circuit approximately 800 V, and the voltage withstand capability of the semiconductor switching device approximately 1200 V.

[0031] In principle, however, significantly higher operating voltages, particularly for DC circuits, are also achievable with a design according to the invention. For example, the threshold voltage of the residual energy absorption device can be approximately 1600 V, the maximum operating voltage of the circuit approximately 1500 V, and the voltage withstand capability of the semiconductor switching device approximately 1700 V.

[0032] Preferably, the opening (or closing) of the various aforementioned electrical contacts, or the switching of the semiconductor switching device (to "open," i.e., "block the current" or "close," i.e., "allow the current to flow"), can be effected by means of suitable control signals from a control device, as will be explained in more detail below. A control device according to the invention is then configured accordingly to control such a hybrid switch.

[0033] Further, particularly advantageous embodiments and developments of the invention result from the dependent claims and the following description, wherein the claims of one claim category may also be further developed analogously to the claims and description parts of another claim category and, in particular, individual features of different embodiments or variants may be combined to form new embodiments or variants.

[0034] There are preferred options for the filling gas. As already mentioned, the filling gas has a higher energy absorption capacity compared to air.

[0035] Preferably, the filling gas can also have a higher dielectric strength than air. Preferably, the filling gas can be a hydrogen-nitrogen mixture. Compared to pure hydrogen, a hydrogen-nitrogen mixture has a higher dielectric strength. Furthermore, the mixture is less volatile than, for example, H₂ alone. Nitrogen also has a passivating effect, which reduces the attack on contact surfaces. With pure H₂, the contact surfaces could potentially be attacked.

[0036] The hydrogen-nitrogen mixture preferably has a ratio of approximately 70-90% hydrogen and approximately 30-10% nitrogen, and even more preferably a ratio of approximately 75-85% hydrogen and approximately 25-15% nitrogen. A ratio of approximately 80% hydrogen and approximately 20% nitrogen is particularly preferred. At approximately this ratio, a particularly rapid voltage build-up at the anode and cathode is optimally supported.

[0037] Preferably, the filling gas can have a pressure of approximately 2 to 6 bar, particularly preferably approximately 3 to 5 bar. A certain pressure accelerates the voltage build-up at the anode and cathode. The higher the pressure, the more complex and difficult it is from a technical perspective to construct the switching chamber, especially to encapsulate it. Therefore, it is particularly preferable that the filling gas has a pressure of approximately 4 bar. A value of approximately 4 bar ideally supports the switching process and at the same time allows for a relatively simple switching chamber.

[0038] Preferably, the first section can be configured to have a switching time of at most 1 ms, preferably at most 0.5 ms, and most preferably at most 0.2 ms. After reaching a certain voltage (namely, a so-called threshold voltage (also collector-emitter voltage (UCE) or drain-source voltage (Ros⁻¹) of the semiconductor switching device)) at the mechanical switching device, the current commutates to the semiconductor switching device, since the resistance at the mechanical switching path is then greater than across the semiconductor switching path. For example, in the case of the IGBT semiconductor switching device, which will be explained in more detail below, the gate voltage is understood to be the voltage between the control electrode or control terminal (=gate) and the emitter terminal (=emitter). The gate voltage allows the semiconductor to be "closed" or switched to conduction. The conductivity can be "controlled" by adjusting the gate voltage.Conductivity improves with higher gate voltage up to a certain limit. The nominal gate voltage for IGBTs is typically around 15V. Only after a certain period of time has elapsed does the semiconductor switching device switch to "block." The current then "commutes" a second time to the residual energy absorption device, dissipating or "burning off" the remaining energy in the circuit. This process removes the residual energy from a potential arc. When the arc's energy is removed, the current, or rather the current intensity, decreases due to fewer charge carriers. The period from the opening of the mechanical switching device until the commutation from the semiconductor switching device to the residual energy absorption device is called the switching time. The shorter the current conduction time of the semiconductor switching device, the lower the current intensities it must withstand.The advantage of a very fast switching time is that even a small semiconductor switching device can be used, which would not be able to withstand such high currents continuously. The relationship between component size and current is quadratic; that is, if the semiconductor switching device can withstand, for example, 1 / 5 less current, this saves approximately 1 / 25 of the active semiconductor volume. Such semiconductor switching devices are, among other things, considerably more cost-effective. The re-solidification time of the mechanical switching device also has a certain influence on the switching time.

[0039] Preferably, the hybrid switch can be designed such that the semiconductor switching device has a current carrying capacity (occasionally also called "current carrying capacity") of at most 150 A, particularly preferably at most 125 A, most preferably at most 100 A.

[0040] Alternatively or additionally, the hybrid switch can be designed such that the semiconductor switching device preferably has a continuous current carrying capacity of at most one third, particularly preferably at most one quarter, most preferably at most one fifth, of the operating current or nominal rated current.

[0041] There are various options for the design of the semiconductor switching device.

[0042] Preferably, the semiconductor switching device can be designed as at least one metal-oxide-semiconductor field-effect transistor (hereinafter referred to as "MOSFET") with an insulated control electrode made of oxide. MOSFETs are currently available in large quantities at relatively low cost. They have several terminals, namely "source," "drain," "bulk" (substrate), and a control terminal "gate." The resistance, and thus the current, of the "drain-source" path is controlled by the voltage between "gate" and "source" and the resulting electric field. Furthermore, they are asymmetrically designed; that is, when they are closed (i.e., switched to "forward" or "ON"), they allow current to flow in both directions, and when they are open (i.e., switched to "block" or "OFF"), they block current only in the forward direction.

[0043] Alternatively, the semiconductor switching device can also be designed as at least one "Insulate-Gate Bipolar Transistor" (hereinafter referred to as "IGBT"). In IGBTs, the terminals are designated as follows: emitter (E), collector (C), and base (B). As long as the threshold voltage (gate-emitter voltage) is not reached, the IGBT is in reverse bias. If the voltage is increased, the IGBT enters the forward bias region. Due to their high power density, IGBTs are particularly suitable for switching high currents and high voltages. Compared to MOSFETs, IGBTs have not been in use as long and are therefore more expensive and available in fewer variants. IGBTs are symmetrical. When they are closed, they conduct in only one current direction. When they are open, they block current in both directions.

[0044] Preferably, the semiconductor switching link can have at least one parallel freewheeling diode with a breakdown voltage that corresponds to the voltage rating of the semiconductor switching device.

[0045] Preferably, the breakdown voltage can be at least 110% of the nominal switching voltage. For example, with a nominal switching voltage of approximately 800 V, the breakdown voltage can be approximately 1200 V.

[0046] With the aid of a freewheeling diode, an IGBT can be connected in anti-series or complementary (i.e., with opposite polarity) series with another IGBT, also with a freewheeling diode, in a bidirectional configuration. This allows the semiconductor switching device to conduct current in both directions in the "closed" or "conducting" state. This state differs from the "blocking" state in that a significantly larger current is allowed to flow. In the blocking state, the current flow is not necessarily zero, but it is negligibly small. Therefore, by analogy to a mechanical switch, this is also referred to as "opening" the semiconductor switching device or switching it to "open" (although, strictly speaking, semiconductor switches do not have closing or opening contacts).In the series-connected IGBTs, the current flows through the semiconductor in the first IGBT in one direction and through the first freewheeling diode in a second, reversed direction. The second semiconductor behaves exactly the opposite way; that is, the current flows through the second freewheeling diode in the first direction and through the semiconductor in the second direction.

[0047] Preferably, the semiconductor switching junction can be configured to have a dielectric strength of at least 125%, particularly preferably at least 150%, of the nominal switching voltage. For example, the semiconductor switching junction can have a dielectric strength of 1200 V at a nominal switching voltage of 800 V.

[0048] Preferably, the semiconductor switching device can be designed to have a short-term current carrying capacity of at least 500 A for 0.5 ms or a short-term current carrying capacity of 1000 A for 0.1 ms. That is, the semiconductor switching device is capable of carrying such high currents for short periods.

[0049] There are preferred options for the design of the residual energy absorption device.

[0050] Preferably, the residual energy absorption device can comprise a varistor, particularly preferably a metal oxide varistor. A varistor is a voltage-dependent resistor, as it is characterized by a resistance that depends on the voltage. Above a certain threshold voltage, which is typical for the respective varistor, the so-called differential resistance (i.e., the change in voltage with respect to a corresponding small change in current) decreases abruptly. For example, with a voltage rating of 1200 V for the semiconductor switching device and a nominal operating voltage of 800 V, a varistor can be used that has a manufacturer-specified start-up terminal voltage of approximately 1130 V. In a varistor, the resistance, and thus the threshold voltage, increases with each switching cycle, especially at high currents and high voltages.The threshold voltage can, for example, increase with each switching cycle from 1130 V until it eventually reaches 1200 V. This could be used as an indicator to replace the varistor, because the residual energy absorption and / or power dissipation (energy / time, approximately 700 joules must be absorbed adiabatically in 2 ms) may no longer be reliably guaranteed. For example, an RCD snubber circuit can be used in parallel with the varistor to further extend its service life. Preferably, the disconnect switch can be designed to disconnect or switch off the circuit in the second section at least once, even in the event of a fault. This can be advantageous, for example, if switching the circuit in the first section does not function as intended or if maintenance is required.In the event of a fault, the disconnect switch should therefore be designed to disconnect the entire load in the circuit, or preferably, to also interrupt a short circuit. Furthermore, disconnecting the circuit in the second section prevents energy losses due to leakage currents.

[0051] Preferably, the second switching path in the second section, when the mechanical disconnect switch is open, can have a contact gap between the contacts of at least 1.8 mm per contact point in order to reliably prevent reignition of the arc in the event that an arc has existed, at least briefly.

[0052] Preferably, the disconnect switch can include an evacuated isolation gap and a system for deflecting an electric arc, e.g., a magnetic field. This is particularly advantageous for isolation in the event of a fault.

[0053] Preferably, the first and / or second switching path can each have at least two contact points in series in the form of a bridge contact. Such a bridge contact can, for example, be essentially T-shaped. It accelerates the voltage build-up in the mechanical switching device, so that the current commutates more quickly to the semiconductor switching device because the required resistance is reached more rapidly, since the current takes the path of lower resistance. The anode-fall and cathode-fall voltages build up at two further points, namely four, namely the contact points where the circuit is broken. In principle, the more contact points, the greater the resistance of the first mechanical switching path when it opens. In principle, several bridge contacts can also be used in series to further increase the resistance and thus accelerate the voltage build-up.However, normally only a low single-digit number of contact points or bridge contacts should be used, as otherwise synchronizing the disconnection at all contact points becomes more difficult. Disconnection should preferably occur simultaneously at all contact points, as otherwise commutation might occur before the last contact point is actually open, which in extreme cases could lead to arc re-ignition. At the same time, the component becomes larger and its resistance higher as the number of contact points increases.

[0054] Preferably, the mechanical switching device can be designed to have an opening speed per contact point of at least approximately 0.5 m / s, preferably at least approximately 1 m / s, and particularly preferably at least approximately 1.5 m / s. This facilitates rapid commutation of the current to the semiconductor switching device, as the voltage across the switching path builds up more quickly after the so-called anode-fall and cathode-fall voltages, and thus the required resistance for commutation is reached more quickly.

[0055] Preferably, the mechanical switching device, in its fully open state, can have a contact gap, i.e., a contact opening between the contacts of the switching section, which is so large that the dielectric strength between the contacts is greater than the nominal operating voltage.

[0056] Preferably, the hybrid switch can be designed such that the commutation from the mechanical switching device to the semiconductor switching device takes place at a contact gap, i.e. a contact opening between the contacts of the mechanical switching device of approximately 0.1 mm per contact point, i.e. in approximately 0.3 ms after the opening of the mechanical switching device.

[0057] There are various ways to control the hybrid switch.

[0058] Preferably, as mentioned, the hybrid switch can include a control device for outputting on and off signals to the mechanical switching device, the semiconductor switching device, and the disconnect switch. Such a control device enables precise control of the switching time of the hybrid switch. This control device can be implemented, for example, by a suitably programmed microcontroller of type MSP430FR5969.

[0059] Preferably, the opening or closing of the electrical contacts at at least one contact point of the contacts in the first switching path of the mechanical switching device can be effected by means of a first control signal from the control device. Equally preferably, the signal to open or close the semiconductor switching device can be effected by means of a second control signal from the control device, with a time delay after the signal to open or close the mechanical switching device.

[0060] Preferably, the mechanical switching device can have at least one main contact and additionally a mirror contact. The mirror contact is designed such that when the main contact opens, the mirror contact is forcibly closed, and vice versa.

[0061] Preferably, the switching of the semiconductor switching device, i.e., the opening or closing, can be coupled to the switching of the main contact and the mirror contact, wherein the switching takes place in a switching time which is set by the mechanical distance between the main contact and the mirror contact.

[0062] Alternatively or additionally, the mechanical switching device can have an optical detection device, preferably a light barrier or an optical sensor, wherein the control of the semiconductor switching device is carried out via a signal from the optical detection device, preferably the light barrier or the optical sensor.

[0063] The advantage of controlling the switching via a mirror contact and / or optical detection device lies in the fact that the triggering of the semiconductor switching device is carried out directly by the mirror contact and / or the optical detection device. Therefore, no control device is required to maintain timing sequences, which would otherwise need to be implemented for the switching process. In this respect, these preferred designs replace a complex control device, resulting, among other things, in fewer components being required. They are therefore less complex, save space, and are more cost-effective.

[0064] Preferably, a gate voltage of up to 135%, particularly preferably up to 170%, and most preferably up to a maximum of 200%, of the nominal gate voltage of the semiconductor switching device can be applied to the semiconductor switching device. In the case of an IGBT, for example, the gate voltage is understood to be the voltage between the control electrode or control terminal (=gate) and the emitter terminal (=emitter). This widens the current-carrying channel of the semiconductor, thus allowing higher currents to be carried. By applying an increased gate voltage, the current-carrying capacity of the semiconductor in the switching device can be improved. Typically, the nominal gate voltage for IGBTs is approximately 15 V. Therefore, for example, a maximum of 20 V, preferably a maximum of 25 V, and particularly preferably 30 V can be applied.

[0065] The invention is explained in more detail below with reference to the accompanying figures and exemplary embodiments. The same components are designated with identical reference numerals in the various figures. The figures are generally not to scale. They show:

[0066] Figure 1 shows a schematic circuit diagram of a first embodiment of a hybrid switch according to the invention,

[0067] Figure 2 shows a schematic circuit diagram of a second embodiment of a hybrid switch according to the invention.

[0068] Figure 3 shows a schematic circuit diagram of a third embodiment of a hybrid switch according to the invention,

[0069] Figure 4 shows three switching time diagrams a), b) and c) of the sequences of the three embodiments according to Figures 1 to 3 of the hybrid switch according to the invention for comparison.

[0070] Figure 1 shows the circuit configuration of a first embodiment of a hybrid switch 1 integrated into a DC circuit, here with a nominal operating voltage up to 800 V and an operating current up to 500 A. The hybrid switch 1 comprises two sections 10, 50, a first section 10 with three parallel paths or devices 20, 30, 40 and a second section 50 connected in series, which are integrated into the circuit to switch a load CL in the circuit, i.e. to open (in Figure 4a, see state: “ON”) or to close (in Figure 4a, see state: “OFF”) the circuit.

[0071] The first section 10 comprises, as a first component, a mechanical switching device 20 with a first switching section 21 and a contact point 22, here in the form of a bridge contact 22 (not shown). The switching section 21 is encapsulated in a switching chamber 23, which is filled with a gas 24 (indicated by dots in the figure) that has a higher energy absorption capacity than air. As a second component, the first section 10 comprises a semiconductor switching device 30 with a semiconductor switching section 31. The semiconductor switching device 30 comprises two IGBTs 30 connected in series, each with a freewheeling diode 34, 35 connected in parallel to the IGBTs 30.

[0072] As a third component, the first section 10 includes a residual energy absorption device 40, here designed as a metal oxide varistor (MOV) 40, with a threshold voltage (approx. 1000 V) which is chosen here to be between the nominal operating voltage (approx. 800 V) and the voltage rating (approx. 1200 V) of the semiconductor switching device.

[0073] The second section 50 comprises (as a further component of the hybrid switch 1) a mechanical disconnect switch 50a, 50b with a second switching path, which is connected upstream and downstream of the load CL in order to disconnect the load CL from the circuit at least once. This disconnect switch is not shown in the further embodiments, but can be implemented there in the same way.

[0074] Furthermore, the hybrid switch 1 includes a control device 60 for controlling the components of the hybrid switch 1. All elements of the control device 60 are shown with dashed lines in Figure 1. The control device 60 comprises a central unit in which all control parameters for controlling the timing of the switching of the hybrid switch 1 converge. For this purpose, the control device 60 has several voltage and current transformers 61, 62, 63, 64, 65. It includes a voltage transformer 61, which takes the voltage UHCB from the first section 10, and a voltage transformer 65, which measures the gate voltage UG at the semiconductor switching device 30.Furthermore, in each of the three components 20, 30, 40 of the first section 10, it comprises a current transformer 62, 63, 64 for measuring the current IN in the mechanical switching device 20, the current Io in the semiconductor switching device 30, and the current IE in the residual energy absorption device 40. In addition, the control device 60 comprises a driver 66 for controlling the mechanical switching device 20 in the first section 10, a driver 67 for controlling the semiconductor switching device 30 in the first section 10, and a driver 68 for controlling the mechanical disconnect switch 50a, 50b in the second section 50. The drivers 66, 67, 68 are each supplied with a voltage of 24 V (via a separate circuit). Overall, the control device 60 is programmable and controllable and is connected to a comparator 70, which compares the measured voltage values ​​and transmits them to the control device 60.The corresponding switching sequence is roughly schematically shown in Figure 4 in the left switching time diagram a).

[0075] In the switching time diagrams a) to c) shown in Figure 4, the switching state is plotted against time t. For the case where a circuit is to be closed using hybrid switch 1, times h and t2 are relevant.

[0076] At time h, the semiconductor switching device 30 is switched to the ON state (for the first embodiment according to Figure 1, this is shown in the upper diagram a) in Figure 4). After a shortest possible "flying time" tf, the contact point 22 of the mechanical switching device 20 is closed at time t2 (corresponding to the ON state). From time h to time t2, the current lc flows briefly through the semiconductor switching device 30. Subsequently, the current commutates to the mechanical switching device 20, since the resistance is lower there, and initially continues to flow normally.As indicated by the dashed line, the semiconductor switching device 30 can optionally be temporarily switched to the OFF state with a slight time delay after the current has been commutated to the mechanical switching device 20 (since the resistance in the semiconductor switching device 30 is greater than in the mechanical switching device 20, no current flows through the semiconductor switching device 30 anyway).

[0077] In the event that a circuit is to be opened using hybrid switch 1, times t3 and t4 are relevant. First, it is ensured that the semiconductor switching device 30 is in the ON state; that is, if it has not been switched to the OFF state in the meantime, it remains there; otherwise, it is switched to the ON state at least shortly before time t3. At time ta, the contact point of the mechanical switching device 20 is opened and thus switched to the OFF state. Subsequently, the voltage in the mechanical switching device 20 rises very rapidly until the voltage, and consequently the resistance, are high enough for the current to commutate from the mechanical switching device 20 to the semiconductor switching device 30.After a short flying time (tf), during which the semiconductor switching device 30 conducts current for as short a time as possible, the semiconductor switching device 30 is also switched to the OFF state, whereupon the residual energy present in the circuit is dissipated via the residual energy absorption device 40. Figure 2 shows the circuit configuration of a second embodiment of a hybrid switch 100 with a mirror contact. The circuit configuration is largely similar to that of the first embodiment. Therefore, the similarities are only briefly mentioned, and the main focus is on the differences.

[0078] As in the first embodiment, the switching arrangement of the second embodiment also has a first section 110 with three parallel paths or devices 120, 130, 140 and a second section 150 connected in series with a load CL and a disconnect switch (not shown here). Additionally or alternatively, as shown here, a switch 185, 186, which can be controlled via a driver voltage Udrive of a driver, can be arranged in the first section to interrupt the current flow through the semiconductor switching device and the residual energy absorption device. The first section 110 differs in particular in the structure of the first component, namely the mechanical switching device 120. The first switching path of the mechanical switching device 120 comprises a main contact 121, which is open ("normally open") after the switching operation of the switching device 120.The circuit consists of a normally open contact (and a mirror contact 122) and a normally closed contact (“normally closed”) when the main contact 121 is open, and vice versa. This configuration is set up so that the mirror contact 122 automatically switches (and closes) with a time delay relative to the main contact 121. This automatic closing process triggers the switching operation in the semiconductor switching device 130 via a driver 193, after the current has commutated to the semiconductor switching device 130 during the appropriately timed interval. The driver 193 is connected to another circuit with a voltage of 24 V via a DC-DC converter 194. After the semiconductor switching device 130 automatically opens at the semiconductor switching junction, the residual energy of the current dissipates as intended via the residual energy absorption device 140. This process is also shown schematically in Figure 4 b).The mechanical interlocking between main contact 121 and mirror contact 122 enables a very simple construction without a complex control device.

[0079] The switching time diagram 4b) of the second embodiment according to Figure 2 differs from the first switching time diagram 4a) in that the mechanical switching device 120 now has, in addition to a main contact 121, a further mirror contact 122 mechanically interlocked with the main contact 121, thus exhibiting an additional switching state curve. If a circuit is to be closed with the hybrid switch 100, the times up to h and t2 are again relevant. At time ti, the mirror contact 122 of the mechanical switching device 120 opens, thereby switching the semiconductor switching device 130 to the ON state. With a delay in the form of the flying time tf, the main contact 121 is closed, i.e., switched to the ON state, so that the current flows normally through the mechanical switching device 120, since the resistance there is lower than through the semiconductor switching device 130.Thus, the semiconductor switching device 130 only carries the current lc briefly for the period h to t2.

[0080] As indicated by the dashed line, the semiconductor switching device 130 can also be switched to the OFF state temporarily, if desired, with a slight time delay after the current has commutated to the main contact 121 of the mechanical switching device 120.

[0081] To minimize the time the semiconductor switching device 130 conducts the current lc, a time delay td (delay) can be implemented. For this purpose, the semiconductor switching device 130 switches to the ON state with a slight delay, thus reducing the time the current flows through the semiconductor switching device 130. Depending on the type and speed of sound of the mechanical switching device 120, this time delay td may not be necessary and is therefore considered optional.

[0082] In the event that the circuit is to be opened with the hybrid switch 100, times t3 and t4 are again relevant. First, it is ensured that the semiconductor switching device 130 is in the ON state; that is, if it has not been switched to the OFF state in the meantime, it remains there; otherwise, it is switched to the ON state at least briefly before time t3. At time ta, the main contact 121 of the mechanical switching device 120 is opened and thus switched to the OFF state. The voltage in the mechanical switching device 120 then rises very rapidly until the voltage, and consequently the resistance, are high enough for the current to commutate from the mechanical switching device 120 to the semiconductor switching device 130. After a short flying time tf, the mirror contact 122 closes automatically, thus switching to the ON state.This switches the semiconductor switching device 130 to the OFF state, so that the semiconductor switching device 130 only conducts current for the short flying time tf. Any residual energy still present in the circuit is dissipated via the residual energy absorption device 40. This embodiment is, among other things, more cost-effective than the first embodiment as well as a subsequent third embodiment.

[0083] Figure 3 shows the circuit configuration of a third embodiment of a hybrid switch 200. This embodiment differs from the previous one essentially in that an optical detection device 201, i.e., for example, an optical sensor at the main contact 221, is integrated into the mechanical switching device 220, and the mirror contact 122 from the second embodiment according to Figure 2 has been replaced by a mechanical or optical switch 202, which triggers automatically based on the optical sensor output signal and thus activates the semiconductor switching device 230. The optical detection device 201 optically registers a switching process in the mechanical switching device 220 and outputs a corresponding switching signal to the switch 202, which in turn directly triggers the semiconductor switching device. After a short flying time tf, the switch 230 is activated.When the hybrid switch opens, it automatically switches to the OFF state, and the residual energy of the current is dissipated, as in the first and second embodiments, via the further parallel-connected residual energy absorption device 240. This process is roughly schematically illustrated in Figure 4 c).

[0084] Unlike the process shown in Figure 4 b), contact bounce cannot occur here. Contact bounce is schematically represented in Figure 4 b) by several adjacent vertical lines (see the switching state curve of the mirror contact 122 after time t4). In most cases, contact bounce is not particularly relevant from a circuit design perspective. However, it can be advantageously avoided with the design according to the third embodiment of the hybrid switch 200. Otherwise, the timing sequence is largely identical and is therefore not described again separately.

[0085] Finally, it should be noted once again that the devices described in detail above are merely exemplary embodiments which can be modified in various ways by a person skilled in the art without departing from the scope of the invention. For example, it is also conceivable to use transistor switches other than IGBTs or MOSFETs. Furthermore, the use of the indefinite articles "a" or "an" does not preclude the possibility that the features in question may be present multiple times. Likewise, the term "unit" does not preclude the possibility that it may consist of several subunits, possibly even spatially separated ones. List of reference numerals

[0086] 1 hybrid switch

[0087] Section 10, first

[0088] 20 mechanical switching device

[0089] 21 Switching section, first

[0090] 22 contact points / bridge contact

[0091] 23 Switching chamber

[0092] 24 Filling gas

[0093] 30 Semiconductor switching device / IGBT

[0094] 31 Semiconductor switching link

[0095] 34 Freewheeling diode, first

[0096] 35 Freewheeling diode, second

[0097] 40 Residual energy absorption device / varistor

[0098] Section 50, second

[0099] 50a, 50b Disconnect switch

[0100] 51 Switching section, second

[0101] 52 contact point, first

[0102] 53 Contact point, second

[0103] 60 Control device

[0104] 61 Voltage converters (for measuring UHCB)

[0105] 62 current transformers (for measuring IN)

[0106] 63 Current transformers (for measuring collector current lc)

[0107] 64 current transformers (for measuring IE)

[0108] 65 voltage transformers (for measuring UG)

[0109] 66 drivers for mechanical switching devices

[0110] 67 drivers for semiconductor switching devices

[0111] 68 T drivers for T disconnect switches

[0112] 70 comparisons

[0113] 100 hybrid switches

[0114] Section 110, first

[0115] 120 mechanical switching device

[0116] 121 Contact point / Main contact

[0117] 122 Contact point / Mirror contact

[0118] 123 Switching chamber

[0119] 130 Semiconductor switching device / IGBT 140 Residual energy absorption device / Varistor

[0120] Section 150, second

[0121] 182 drivers

[0122] 185 Unpolarized power relay

[0123] 186 switches

[0124] 187 drivers

[0125] 188 Potential equalization

[0126] 189 Schottky diode

[0127] 190 Capacitor

[0128] 191 Resistance, first

[0129] 192 Resistance, second

[0130] 193 drivers

[0131] 194 DC / DC converters

[0132] 200 hybrid switches

[0133] 201 Optical detection device

[0134] 202 switches with optical

[0135] 220 mechanical switching device

[0136] 221 Switching section

[0137] 223 Switching chamber

[0138] 230 Semiconductor switching device

[0139] 240 Residual energy absorption device / varistor

[0140] CL electrical load lc current through semiconductor switching device

[0141] IE current through residual energy absorption device

[0142] IN current through mechanical switching device

[0143] OFF Open / locking

[0144] ON Closed / Permeable td Time delay t f Flying time t Time tl , t2, t3, t4 Time points Udrive Driver voltage UHCB Voltage at the first section UG Gate voltage a) Switching time diagram for the first embodiment b) Switching time diagram for the second embodiment c) Switching time diagram for the third embodiment

Claims

Patent claims 1. Hybrid switch (1, 100, 200) comprising a switching arrangement with A) at least a first section (10, 110) comprising at least the following three parallel-connected components (20, 30, 40, 120, 130, 140): i) at least one mechanical switching device (20, 120, 220) with a first switching section (21) having at least one contact point (22), wherein at least the switching section (21) is encapsulated in a switching chamber (23, 123, 223) filled with a filling gas (24) which has a higher energy absorption and preferably a higher dielectric strength compared to air, ii) at least one semiconductor switching device (30, 130, 230) with a semiconductor switching section (31), and iii) a residual energy absorption device (40, 140, 240) with a threshold voltage selected such that it lies between a maximum operating voltage of the circuit and a dielectric strength the semiconductor switching device (30) is located, B) a second section (50, 150) connected in series with the first section (10, 110) with a mechanical disconnect switch (50a, 50b) with a second switching section (51) for at least one-time disconnection of the circuit.

2. Hybrid switch (1, 100, 200) according to claim 1, wherein the filling gas (24) is a hydrogen-nitrogen mixture, preferably wherein the hydrogen-nitrogen mixture has a ratio of approximately 70-90% hydrogen and approximately 30-10% nitrogen, particularly preferably a ratio of approximately 75-85% hydrogen and approximately 25-15% nitrogen, most preferably a ratio of approximately 80% hydrogen and approximately 20% nitrogen.

3. Hybrid switch (1 , 100, 200) according to claim 1 or 2, wherein the first section (10, 110) has a switching time of at most 1 ms, preferably at most 0.5 ms, particularly preferably at most 0.2 ms.

4. Hybrid switch (1 , 100, 200) according to one of the preceding claims, wherein the hybrid switch (1 , 100, 200) is configured such that the semiconductor switching device (30, 130, 230) has a nominal current carrying capacity of at most 150 A, preferably at most 125 A, particularly preferably at most 100 A, and / or a current carrying capacity of at most one third, preferably at most one quarter, particularly preferably at most one fifth, of an operating current.

5. Hybrid switch (1 , 100, 200) according to one of the preceding claims, wherein the semiconductor switching device (30, 130, 230) is configured as at least one MOSFET or at least one IGBT (30, 130, 230).

6. Hybrid switch (1 , 100, 200) according to one of the preceding claims, wherein the semiconductor switching section (31) has at least one parallel-connected freewheeling diode (34, 35) with a breakdown voltage corresponding to the dielectric strength of the semiconductor switching device (30, 130, 230), wherein preferably the breakdown voltage is at least 110% of a nominal switching voltage.

7. Hybrid switch (1 , 100, 200) according to one of the preceding claims, wherein the semiconductor switching gap (31) has a dielectric strength of at least 125%, preferably 150%, of a nominal switching voltage.

8. Hybrid switch (1 , 100, 200) according to one of the preceding claims, wherein the semiconductor switching section (31) is designed to have a short-term current carrying capacity of at least 500 A for 0.5 ms or 1000 A for 0.1 ms.

9. Hybrid switch (1 , 100, 200) according to one of the preceding claims, wherein the residual energy absorption device (40, 140, 240) comprises a varistor (40, 140, 240), preferably a metal oxide varistor (40, 140, 240).

10. Hybrid switch (1 , 100, 200) according to one of the preceding claims, wherein the disconnect switch (50a, 50b) in the second section (50) is designed to disconnect the circuit once in the event of a fault.

11. Hybrid switch (1 , 100, 200) according to one of the preceding claims, wherein the second switching section (51) in the open state of the disconnect switch (50a, 50b) has at least a contact distance between the contacts of approximately 1.8 mm per contact point (52, 53).

12. Hybrid switch (1 , 100, 200) according to one of the preceding claims, wherein the first and / or the second switching section (21 , 51) each have at least two contact points (22, 52, 53) in series in the form of a bridge contact (22, 52, 53).

13. Hybrid switch (1 , 100, 200) according to one of the preceding claims, wherein the mechanical switching device (20, 120, 220) has an opening speed per contact point (22, 52, 53) of at least approx. 0.5 m / s, preferably at least approx. 1 m / s, particularly preferably at least approx. 1.5 m / s.

14. Hybrid switch (1 , 100, 200) according to one of the preceding claims, wherein the mechanical switching device (20, 120, 220) in the fully open state has a contact gap between contacts of the switching section (31) which is such that the dielectric strength between the contacts is greater than the nominal operating voltage.

15. Hybrid switch (1 , 100, 200) according to one of the preceding claims, comprising a control device (60) for outputting on and off signals to the mechanical switching device (20), the semiconductor switching device (30) and the disconnect switch (50a, 50b).

16. Hybrid switch (1 , 100, 200) according to one of the preceding claims, wherein the mechanical switching device (120) - has at least one main contact (121) and additionally one mirror contact (122), wherein the mirror contact (122) is designed such that when the main contact (121) opens, the mirror contact (122) is forcibly closed and vice versa, wherein the switching of the semiconductor switching device (130) is coupled to the switching of the main contact (121) and the mirror contact (122), wherein the switching takes place in a switching time which is set by the mechanical distance between the main contact (121) and the mirror contact (122) and / or - comprising an optical detection device (200), preferably an optical sensor (200), wherein the control of the semiconductor switching device is carried out via a signal from the optical detection device (200).

17. Method for controlling a hybrid switch (1, 100, 200) for switching an electrical circuit, comprising at least the following method steps: i) opening or closing two electrical contacts at at least one contact point (22, 52, 53) of the contacts in a first switching section (21) of a mechanical switching device (20, 120, 220), preferably by means of a first control signal from a control device (60), wherein at least the switching section (21) of the mechanical switching device (20, 120, 220) is encapsulated in a switching chamber (23, 123, 223) which is filled with a filling gas (24) which has a higher energy absorption and preferably a higher dielectric strength compared to air, ii) commutating the current from the mechanical switching device (20, 120, 220) to a parallel-connected semiconductor switching device (30, 130, 230) comprising a semiconductor switching section (31), iii) opening or closing the semiconductor switching device (30, 130, 230) with a time delay after the opening or closing in the mechanical switching device (20, 120, 220), preferably by means of a second control signal from the control device (60), iv) Absorption of residual energy still present in the circuit in a mechanical switching device (20, 120,220) and a residual energy absorption device (40, 140, 240) connected in parallel to the semiconductor switching device (30, 130, 230), which has a breakdown voltage selected to be between a maximum operating voltage of the circuit and a dielectric strength of the semiconductor switching device (30, 130, 230).

18. Method according to claim 17, wherein a gate voltage (UG) of up to 135%, particularly preferably up to 170%, most preferably at most 200%, of a nominal gate voltage of the semiconductor switching device (30, 130, 230) is applied to the semiconductor switching device (30, 130, 230).

19. Control device (60) configured for controlling a hybrid switch (1) according to any one of claims 1 to 15, in particular for a hybrid switch according to claim 15, and / or for controlling a hybrid switch according to a method according to claim 17 or 18.

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