Circuit breaker

Abstract

The invention relates to a circuit breaker (12) for operation in a potentially explosive atmosphere (24). The circuit breaker (12) comprises a hybrid switch (28) having a main current path (24) with a disconnecting element (32) and a secondary current path (30) connected in parallel to the main current path (24) with a semiconductor switch (36), as well as a control circuit (40). The disconnecting element (32) and the semiconductor switch (36) are actuated by means of the control circuit (40). The invention further relates to a room (2) and the use of a circuit breaker (12).

Description

[0001] The invention relates to a circuit breaker and the use of a circuit breaker. The circuit breaker comprises a hybrid switch with a main current path and a secondary current path connected in parallel to the main current path. The invention also relates to a room.

[0002] Electricity is increasingly being generated from renewable energy sources such as solar and wind power. Since these sources are not continuously available or only available when needed, storage solutions are required. One option is to use the electricity to produce hydrogen gas and store it. The hydrogen gas produced in this way can also be used for other purposes, such as enriching natural gas or powering vehicles. However, producing hydrogen gas from electricity, especially through electrolysis, requires comparatively high electrical currents.

[0003] In the event of a short circuit in an actuator or damage to a cable supplying the actuator, an overcurrent can occur, leading to further damage to the actuator or feedback into the electrical supply network that powers the actuator. Therefore, it is necessary to interrupt this overcurrent relatively quickly. This is typically achieved using a circuit breaker connected to the electrical cable supplying power to the actuator. If an overcurrent occurs in the cable, meaning the current flowing through the cable exceeds a certain limit, the circuit breaker is activated, thus interrupting the flow of current through the cable and consequently to the actuator.

[0004] A circuit breaker typically has a switching element that is triggered by a signal from a sensor. The sensor and the switching element may be a single unit, such as a bimetallic snap disc. In the closed state, the bimetallic snap disc rests against a mating contact, and the electric current flows through it. If the electric current exceeds the limit, the bimetallic snap disc heats up to varying degrees and therefore bends. This bending causes the bimetallic snap disc to move away from the mating contact, thus interrupting the electric current.If the electric current carried by the circuit breaker is comparatively large and the applied electrical voltage is greater than, for example, 60 V, it is possible that an arc will form between the bent bimetallic snap disc and the opposing contact, through which an electric current will continue to be carried.

[0005] If such a circuit breaker is used in the production of hydrogen gas and is not gas-tight, it is possible that the hydrogen gas that has penetrated the circuit breaker could ignite. To prevent this, the circuit breaker is usually located outside the rooms containing the hydrogen gas, typically in a separate connection room within an industrial plant for hydrogen gas production. This necessitates comparatively long cables, which increases manufacturing costs and the potential for failure. Furthermore, restarting the actuator after the circuit breaker has tripped is complicated, as its operation and response cannot be visually inspected when the circuit breaker is reset to its electrically conductive state.

[0006] An alternative is to design the circuit breaker to be gas-tight and to install it in the same space as the actuator. However, if an arc occurs in the circuit breaker, the pressure within it increases, at least locally, by more than 10 bar. It is therefore essential that the circuit breaker remains gas-tight even at such high pressures, which increases the requirements for the circuit breaker housing. Consequently, the size and manufacturing costs of the circuit breaker increase.

[0007] From WO 2010 / 108565 A1, a hybrid switch (hybrid disconnect switch) is known, comprising a mechanical switch or disconnecting element and semiconductor electronics connected in parallel to it. The semiconductor electronics include a semiconductor switch, preferably an IGBT. The semiconductor electronics have no additional power source and are current-blocking when the mechanical switch is closed, i.e., practically current- and voltage-free. To interrupt the current via the hybrid switch, the mechanical switch is opened, which may generate an arc. The energy of the arc generated when the mechanical switch opens is used by the semiconductor electronics, which are connected to the mechanical switch in such a way that when the mechanical switch opens, the arc voltage across it (due to the arc) makes the semiconductor switch conductive.

[0008] As soon as the semiconductor switch is energized, the electric current commutates from the mechanical switch to the semiconductor switch. The corresponding arc voltage or current also charges an energy storage device in the form of a capacitor, which provides the control voltage for the semiconductor electronics. Once the electric current has commutated to the semiconductor switch, the arc extinguishes, and the charging process of the energy storage device is complete. An ionized gas, generated by the arc, is present between the switching contacts of the mechanical switch and dissipates over time. Following the charging process, a timer starts, during which the energy storage device keeps the semiconductor switch energized. After the timer expires, the semiconductor switch is switched off again.

[0009] The invention is based on the objective of specifying a particularly suitable circuit breaker, a particularly suitable space and a particularly suitable use of a circuit breaker, wherein manufacturing costs are expediently reduced and / or safety is increased.

[0010] With regard to the circuit breaker, this problem is solved according to the invention by the features of claim 1, with regard to the space by the features of claim 6, and with regard to the use by the features of claim 9. Advantageous embodiments and further developments are the subject of the respective dependent claims.

[0011] The circuit breaker serves to electrically protect a line and / or an actuator that is energized during operation via a line. Specifically, the circuit breaker is electrically connected to the line and is suitable, specifically designed and configured for this purpose. Advantageously, the circuit breaker has one or preferably two terminals, which are suitable, specifically designed and configured, for connecting the electrical line(s) to each. For example, the terminals are designed as terminals for a busbar, cable lugs, or insulation displacement contacts.

[0012] In particular, the circuit breaker is designed and configured to interrupt the electrical current flowing through it in the event of a guided overcurrent, for example, four times the rated current (i.e., the current carried through the circuit breaker during normal operation). Advantageously, the circuit breaker includes a sensor to detect the current flowing through it, so that the overcurrent can be determined. Alternatively, or in combination, the circuit breaker is designed and configured to detect a short-circuit current of up to 10,000 A, or a so-called "arc" occurring in the actuator / line, and subsequently interrupt the electrical current flow through the circuit breaker.

[0013] For example, a circuit breaker is designed so that the electrical current flowing through it is interrupted when it exceeds a limit value. This limit value can be static, adapted to the specific application, or time-dependent. For instance, the breaker might interrupt the current as soon as the limit value is exceeded, or only if the limit value has been exceeded for a specific period of time. The circuit breaker may also have a control input, and the signals received via this input can be used to switch the circuit breaker into either a conductive or non-conductive state. This allows the circuit breaker to be controlled remotely, thus increasing convenience.

[0014] For example, the circuit breaker is suitable, specifically designed and configured, to withstand an electrical voltage greater than 220 V or 500 V and, for example, less than 2000 V, provided the circuit breaker is electrically non-conductive. The circuit breaker is expediently used to protect an electrical voltage between 400 V and 1500 V and, for example, between 650 V and 800 V, and is suitable, designed and / or configured for this purpose.

[0015] For example, the circuit breaker is installed in an AC system, so that an AC current is carried through the circuit breaker during operation. However, it is particularly preferred that the circuit breaker is installed in a DC system and thus serves to protect a DC circuit. In other words, a DC current is carried through the circuit breaker during normal operation. Suitablely, the electrical current carried through the circuit breaker during normal operation is greater than 10 A, 20 A, or 50 A. In particular, the rated current, i.e., the maximum electrical current carried through the circuit breaker during normal operation, is less than 200 A or 150 A.

[0016] The circuit breaker is suitable for, designed for, and configured for safe operation in a potentially explosive atmosphere. In other words, the intended use of the circuit breaker is in a potentially explosive atmosphere. Therefore, when the circuit breaker is in operation, its immediate vicinity, i.e., adjacent to it, may contain, for example, a (highly) flammable and / or explosive gas, such as hydrogen gas (H2), particularly when mixed with oxygen gas (O2). Alternatively, or in combination with this, gasoline vapors or other highly flammable gases or dust may be present in the vicinity of the circuit breaker. Alternatively, the circuit breaker may be installed, for example, in a flammable / explosive liquid. In the event of a spark, particularly due to localized excessive heating, the gas / dust in the vicinity of the circuit breaker may explode unintentionally or at least ignite.Preferably, the circuit breaker is suitable for operation in a potentially explosive atmosphere in accordance with Directive 1999 / 92 / EC on minimum requirements for improving the health and safety protection of workers who may be exposed to explosive atmospheres. The circuit breaker preferably meets the requirements for use in Zone 0 or 20. Alternatively, the circuit breaker may suitably only meet the requirements for use in Zone 1 or 21. For example, the circuit breaker may only meet the requirements for use in Zone 2 or 22.

[0017] The circuit breaker is designed in such a way that local heating of the surroundings is prevented, so that even if an electric current flowing through the circuit breaker is interrupted, there is no ignition of gases or other explosive substances located in the vicinity of the circuit breaker.

[0018] The circuit breaker incorporates a hybrid switch, which is a disconnecting device, i.e., a switching unit. If the circuit breaker is electrically conductive, the hybrid switch is also electrically conductive, and the electrical current is conducted through it during operation. If the circuit breaker is electrically non-conductive, the hybrid switch is also electrically non-conductive. Advantageously, the hybrid switch is controlled by signals provided by any sensors, thus ensuring the functionality of the circuit breaker.

[0019] The hybrid switch has a main current path, which is formed between, or at least connected to, the two terminals of the circuit breaker. The main current path includes a disconnecting element that can be actuated. This element can be set to a closed position, in which the main current path has low resistance, allowing current to flow between its two ends, preferably between the two terminals. In an open position, however, the disconnecting element has high resistance, preventing current flow through the main current path or at least resulting in increased ohmic resistance. In summary, the disconnecting element is electrically conductive in the closed position and electrically non-conductive in the open position.

[0020] Advantageously, the isolating element is a galvanically isolating component when open. The isolating element is advantageously a mechanical switch, such as a relay, contactor, or connector, or comprises at least one of these. Alternatively, the isolating element is designed as a surge protector. The isolating element is particularly suitable, preferably designed and configured, to provide galvanic isolation of the main current path when opened, i.e., when moved into the open state.

[0021] The hybrid switch further comprises a bypass path that includes a semiconductor switch. Specifically, the semiconductor switch is connected in parallel to the isolating element, so that the isolating element is bypassed by the semiconductor switch. Alternatively, for example, other components of the main current path are also bypassed by the semiconductor switch. The semiconductor switch is advantageously a power semiconductor switch and preferably a field-effect transistor, such as a MOSFET, an IGBT, or a GTO. In particular, during normal operation, i.e., when current is intended to flow through the hybrid switch, the semiconductor switch is current-blocking. Thus, the electrical losses of the circuit breaker during operation are comparatively low. In the open state of the semiconductor switch, it is designed with high resistance, so that current flow through it is essentially impossible.In other words, when open, the semiconductor switch is electrically non-conductive. When closed, the semiconductor switch has low resistance and is therefore electrically conductive.

[0022] The circuit breaker also includes a control circuit by which the disconnecting element and the semiconductor switch are actuated. In other words, the control circuit is designed and configured to actuate the disconnecting element and the semiconductor switch, bringing them into the electrically conductive or non-conductive state. Specifically, a certain electrical voltage is applied to a respective control input for actuation. Advantageously, the disconnecting element and / or the semiconductor switch are actuated by the control circuit when a current flow through the circuit breaker is to be interrupted. In particular, the control circuit is connected to the sensor via a signal path, and the signals provided by the sensor are evaluated by the control circuit during operation.

[0023] Preferably, the isolating element / semiconductor switch is controlled by a control circuit. This circuit is, for example, composed of discrete components such as resistors, capacitors, diodes, or inductors. Preferably, the control circuit includes an application-specific integrated circuit (ASIC) and is, for example, formed using one. Alternatively or in combination with this, the control circuit includes a computer, which is suitably programmable.

[0024] If the circuit breaker is electrically conductive, meaning it is intended to carry an electric current, then the isolating element is electrically conductive and the semiconductor switch is electrically non-conductive. These are expediently controlled accordingly by the control circuit. If the electric current flow through the circuit breaker is to be interrupted, particularly if a triggering event occurs, such as an overcurrent, short circuit, or arc, the isolating element is expediently opened and the semiconductor switch is closed (at least briefly) by means of the control circuit.

[0025] For example, to interrupt the current flow through the circuit breaker, the semiconductor switch is first closed, allowing the electrical current to commutate from the main current path to the bypass path. The disconnecting element is then opened, and because the bypass path is electrically conductive, no arc forms when the disconnecting element opens. The semiconductor switch is then opened, thus entering a non-conductive state, which also interrupts the current flow through the bypass path. The circuit breaker is therefore subsequently in a non-conductive state, and no arc is formed. This process also results in virtually no heating of the circuit breaker, or only minimal heating. Consequently, any flammable / explosive gas present cannot ignite.

[0026] Alternatively, the separating element is opened first, which can lead to the formation of an electric arc. This results in an (unwanted) electric current flowing through the main current path. The voltage drop across the separating element due to the arc is used to switch the semiconductor switch into an electrically conductive state, commutating the electric current flow from the main current path to the secondary current path and interrupting the current flow through the main current path. Specifically, before the semiconductor switch closes, an energy storage device is charged using the voltage drop across the separating element. After the arc in the separating element collapses, the energy stored in this device is used to briefly activate the semiconductor switch, making it electrically conductive.When the arc is interrupted and the energy storage is discharged, the semiconductor switch is switched to a non-conductive state, preventing the arc from reigniting in the separating element due to the cooling that has occurred in the meantime. With this design, in particular, no additional power supply is required for the control circuitry.

[0027] In an alternative embodiment, the control circuit is designed such that, for example, the separating element is initially opened, allowing the arc to form. The separating element is specifically designed such that the longer it remains open, the higher the voltage required to maintain the arc becomes. After a certain period, the semiconductor switch is switched to the electrically conductive state, causing the current to commutate from the main current path to the secondary current path. This causes the arc to collapse. Once this process is essentially complete, the semiconductor switch is reopened almost immediately, thus interrupting the current flow.The time window is chosen in such a way that, despite the comparatively quick reopening of the semiconductor switch, the arc does not reignite due to the comparatively high electrical voltage required to form the arc.

[0028] With each of the aforementioned methods of interrupting the electrical current flow, the duration of any arc is comparatively short, and any heating is only localized and limited. Due to the use of the hybrid switch in the circuit breaker, the environmental impact, and thus any heating, particularly localized heating, is comparatively low. Therefore, even if explosive substances, especially gases, are present in the vicinity of the circuit breaker, they will not ignite. This enables safe operation of the circuit breaker even in such environments, with comparatively low requirements for the separation of the circuit breaker from the explosive gases. This reduces manufacturing costs. Furthermore, since the ignition of explosive / flammable gases in the surrounding area can be essentially ruled out, the safety of operating the circuit breaker is increased.Due to the main current path with the isolating element, the electrical losses incurred during operation of the circuit breaker are comparatively low, and the semiconductor switch is only used to conduct current when an interruption of the current flow is required. Therefore, the requirements for the semiconductor switch are relatively low, which reduces both manufacturing and operating costs.

[0029] Advantageously, the circuit breaker has a mechanical actuator, such as a lever, which allows the (switching) state of the circuit breaker to be changed, i.e., whether it is live or not. In particular, the control circuit is operated, at least partially, depending on the mechanical actuator. This increases the range of applications for the circuit breaker.

[0030] In particular, the circuit breaker has a housing that encloses the disconnecting element, the semiconductor switch, and the control circuitry. This housing provides mechanical protection for these components, simplifying installation. The housing is typically rigid and made of a material such as plastic, thus reducing manufacturing costs. It is also pressure-resistant, meaning the interior and exterior are pressure-tight. Therefore, a pressure differential can exist between them. Consequently, the housing is not gas-permeable, i.e., it is gas-tight. For example, the pressure resistance is less than 1 bar. If the overpressure inside the housing exceeds 1 bar, the housing may be damaged.Due to such low pressure resistance, the requirements for the housing are reduced, which in turn reduces manufacturing costs.

[0031] For example, the housing is flameproof encapsulated. This increases safety. However, it is particularly preferred that the housing is not flameproof encapsulated. In other words, the housing does not meet the requirements of the European standard "EN 60079-1 Explosive atmospheres", and preferably not Part 1 "Protection of equipment by flameproof enclosure" "d" of this standard. This reduces the requirements for the housing and therefore manufacturing costs. Certification is also unnecessary, which further reduces manufacturing costs. Preferably, the housing is also gas-permeable. This allows gas exchange between the inside and outside of the housing, thus enabling heat dissipation from the housing to the environment. Preferably, the housing has several openings, such as slots, to ensure even gas exchange.For example, during operation of the circuit breaker, particularly the disconnecting element / semiconductor switch, the temperature rises excessively. The disconnecting element and the semiconductor switch are controlled in such a way that no arc is generated when the current is interrupted, or at least the control is such that any arc that might occur and the resulting local heating are insufficient to ignite the gas from the surroundings, which may have partially penetrated the housing. The control circuit is suitably designed for this purpose. In summary, the presence of the hybrid switch allows the current to be interrupted via the circuit breaker without the formation of an arc, thus preventing gas ignition despite the housing not being flameproof.

[0032] For example, the bypass path may only include the semiconductor switch. However, it is particularly preferred that the bypass path includes an additional isolating element that is electrically connected in series with the semiconductor switch. For example, the additional isolating element may be identical in construction to the isolating element or different. In particular, the additional isolating element is galvanically isolating, which increases safety. Because of the additional isolating element, galvanic isolation of the bypass path is therefore possible, which is why the entire switch is designed to be galvanically isolating. Thus, safety is further increased.

[0033] For example, the additional isolating element is a mechanical switch, preferably a relay. This additional isolating element is also actuated by the control circuit. Ideally, during operation, the additional isolating element is always closed before the semiconductor switch closes, and it is always opened only after the semiconductor switch opens. Thus, an arc never forms in the additional isolating element, as the switching state is only changed when no electric current flows through the bypass path. The control circuit is suitably designed and configured for this purpose. For example, the additional isolating element is actuated by a corresponding wiring configuration of the control circuit.

[0034] For example, the main current path may only include the isolating element. However, it is particularly preferred that the main current path includes an additional semiconductor switch, which may be identical in construction to the semiconductor switch or, expediently, different from it. In particular, electrical losses in the additional semiconductor switch are prevented compared to the semiconductor switch when the electric current is carried, and, for example, the switching capacity of the additional semiconductor switch is reduced compared to the semiconductor switch, thus lowering manufacturing costs. The additional semiconductor switch is electrically connected in series with the isolating element and actuated by the control circuit. When the circuit breaker is (desired to be) carrying current, the additional semiconductor switch and the isolating element are electrically conductive, i.e., each closed.To interrupt the electrical current flow through the circuit breaker, the semiconductor switch is first closed, so that the electrical current is at least partially commutated from the main current path to the secondary path. Following this, the second semiconductor switch is opened, completely interrupting the current flow through the main current path. The voltage across this second semiconductor switch is comparatively low. Only then is the isolating element opened, preventing the formation of an arc due to the already interrupted current flow. The semiconductor switch is then actuated, thus also interrupting the electrical current flow through the secondary path. The opening time of the isolating element is independent of the opening time of the semiconductor switch.With this type of control, the use of the circuit breaker is also possible in the vicinity of highly flammable gases, ensuring that an arc does not form.

[0035] The space is filled with an explosive atmosphere. For example, the atmosphere is a gas, such as a mixture of hydrogen and oxygen. Alternatively, the space contains, for example, gasoline vapors or similar explosive gases. Another alternative is a mixture of dust and air, containing oxygen or some other oxidizing agent. At a minimum, the atmosphere is such that local excessive heating would cause an exothermic reaction, such as an explosion or at least ignition. The space is provided, for example, by a building or similar structure, and its exterior walls are made of stone or concrete. Alternatively, the space is provided, for example, by a piece of furniture, such as a cabinet or similar.Preferably, the space is designed to be gas-tight and / or pressure-resistant encapsulated.

[0036] An electric actuator is located in the space. This electric actuator, also referred to simply as the actuator, performs a specific task during operation, requiring an electric current to carry out this task. In particular, the actuator creates the atmosphere, preferably the gas or a component thereof. Alternatively, the gas may be used, for example, to prevent a chemical reaction that would otherwise occur due to the actuator's operation, or the actuator may be used to further process the gas or a material, during which the atmosphere is at least partially generated. For example, the space is a tank, and the gas is generated, for instance, by the evaporation of a liquid contained within the tank. In this case, the actuator could be, for example, a pump.However, the actuator is particularly preferred as an electrolysis device, and when current is applied, water undergoes electrolysis, producing hydrogen gas and oxygen gas.

[0037] A circuit breaker is located in the room, and the actuator and the circuit breaker are connected by an electrical conductor. When the actuator is energized, the required electrical current is passed through the circuit breaker and, in particular, monitored. Advantageously, in the event of an overcurrent, which is, for example, a certain multiple of the rated current used in normal operation, a short circuit, or any other malfunction, the circuit breaker is activated, thus interrupting the energization of the actuator and consequently its further operation. Specifically, the circuit breaker includes a terminal to which the electrical conductor is connected, and the remaining end of the electrical conductor is connected to the actuator.

[0038] The circuit breaker comprises a hybrid switch with a main current path containing a disconnecting element and a secondary current path connected in parallel to the main current path, containing a semiconductor switch, as well as a control circuit. The disconnecting element and the semiconductor switch are actuated by means of the control circuit. Preferably, the main current path, and consequently also the secondary current path, are routed to the terminal(s) of the circuit breaker and, in particular, connected between them. When the circuit breaker is electrically conductive, i.e., in the closed state, the electrical current required to energize the actuator is supplied via the main current path.

[0039] Since the actuator and the circuit breaker are located together in the same space, the required length of the electrical cable, also referred to simply as a cable, is comparatively short, thus reducing manufacturing costs. Furthermore, the reaction of the actuator is visible, for example, when the circuit breaker is manually activated, such as when it is switched to an electrically conductive state, making troubleshooting easier.

[0040] For example, the circuit breaker is attached to the actuator, which reduces the required installation space. Alternatively, the circuit breaker can be mounted on a wall of the room, allowing for separate replacement of the actuator and the circuit breaker, for example, for maintenance or in case of a malfunction. Preferably, however, the room has a control cabinet in which the circuit breaker is located. The control cabinet is expediently mounted on a wall of the room. The control cabinet prevents mechanical damage to the circuit breaker. It also facilitates replacement of the circuit breaker, for example, if the requirements for the actuator have changed. Furthermore, the control cabinet simplifies the installation of the circuit breaker in the room. Preferably, the control cabinet is designed to accommodate several circuit breakers.In particular, the control cabinet contains several circuit breakers, and the space also houses, for example, several actuators, at least some of which are identical. It is advantageous for each actuator to be assigned one of the circuit breakers. The control cabinet design simplifies installation.

[0041] For example, the control cabinet is gas-tight and / or pressure-resistant. This increases safety. However, it is particularly preferred that the control cabinet is not pressure-tight encapsulated. Consequently, the control cabinet does not meet the requirements of the European standard "EN 60079-1 Explosive atmospheres - Part 1 Equipment protection by flameproof enclosure 'd'". In this way, the requirements for the control cabinet and therefore manufacturing costs are reduced. Certification is also unnecessary, which further reduces manufacturing costs. In particular, it is possible to use any control cabinet. It is advantageous for the control cabinet to be gas-permeable. This facilitates heat dissipation from the control cabinet, thus preventing local overheating that could, for example, ignite the explosive gas and / or destroy the circuit breaker.Furthermore, it is possible to use a standard component or at least an existing design for the control cabinet, thus reducing manufacturing costs. Since the design of the circuit breaker prevents the formation of an arc when the circuit breaker is switched (i.e., when its switching state changes, namely when the current flow through the circuit breaker is interrupted or started), there are essentially no requirements for the control cabinet regarding explosion suppression.

[0042] In particular, a circuit breaker comprising a hybrid switch is used to protect an actuator. The circuit breaker is located in a potentially explosive atmosphere, specifically an explosion-hazardous area. Thus, an explosive / flammable fluid, such as a gas or liquid, is located directly adjacent to the circuit breaker. The hybrid switch has a main current path with a disconnecting element and a secondary current path connected in parallel to the main current path, containing a semiconductor switch, as well as a control circuit by which the disconnecting element and the semiconductor switch are actuated. Due to the design of the circuit breaker, the formation of an arc is prevented when the switching state of the circuit breaker changes, or its duration is at least comparatively short.The change in switching state occurs to protect the actuator, for example, in the event of an overload or malfunction. The potentially explosive atmosphere in which the circuit breaker is used meets, for example, the definition of Zone 2 / 22, or preferably Zone 1 / 21, or most preferably Zone 0 / 20, according to Directive 1999 / 92 / EC on minimum requirements for improving the health and safety protection of workers who may be at risk from explosive atmospheres.

[0043] The further training and advantages explained in connection with the circuit breaker can also be applied analogously to the room / the use and to each other, and vice versa.

[0044] An embodiment of the invention is explained in more detail below with reference to a drawing. The drawing shows: the single figure: schematically a room with an actuator and a circuit breaker.

[0045] The single figure schematically simplifies a section of room 2 in a perspective view. Room 2 is realized by means of a building (not shown in detail) and has several walls 4, three of which are shown. Access to room 2 is provided via an airlock (not shown in detail). A control cabinet 6, shown semi-transparently, is attached to one of the walls 4. Thus, the control cabinet 6 is located within room 2.

[0046] Two supply lines 8 extend into control cabinet 6, one of which is electrically connected to a busbar 10 located in control cabinet 6. The other supply line 8 is electrically connected to a circuit breaker 12 located in the control cabinet. This supply line 8 is connected to one of two terminals 14 of the circuit breaker 12. Since the circuit breaker 12 is located in control cabinet 6, which is situated in room 2, it is consequently also located in room 2. A line 16 is connected to the other terminal 14 of the circuit breaker 12. This line leads from control cabinet 6 to an (electrical) actuator 18, which is also located in room 2. In summary, the actuator 18 and the circuit breaker 12 are thus electrically connected by means of the (electrical) line 16.The busbar 10 is connected in the control cabinet 6 to another line 20, which is also connected to the actuator 18.

[0047] For the operation of actuator 18, it is supplied with electrical energy via the two lines 16 and 20, and thus via the control cabinet 6. This energy is provided by the supply lines 8. The electrical voltage between the two supply lines 8, and therefore also between the two lines 16 and 20, is greater than 400 V and, in the example shown, is 650 V. The electrical current carried by lines 8, 16, and 20 is a direct current of 120 A.

[0048] When actuator 18 is operated, it performs the electrolysis of water, producing hydrogen gas (H2) and oxygen gas (O2). The hydrogen gas is at least partially introduced into chamber 2 and extracted from chamber 2, which is otherwise gas-tight, via an extraction system (not shown) to a tank or similar container. As a result of the actuator 18's operation, an explosive gas 22, namely hydrogen gas mixed with small amounts of oxygen gas, is generated in chamber 2. The control cabinet 6, in which the circuit breaker 12 is located, is not flameproof and is gas-permeable, allowing some of the gas 22 to reach the circuit breaker 12. Therefore, the circuit breaker 12 is located in a potentially explosive atmosphere 24, and the explosive gas 22 is present, at least partially, directly adjacent to the circuit breaker 12.

[0049] When the actuator 18 is operated, the required electrical current flows between the two terminals 14 of the circuit breaker 12, which has a main current path 24 for this purpose, by means of which the two terminals 14 are electrically connected. One end of the main current path 24 is connected directly to one of the terminals 14, and the remaining end of the main current path 24 is connected to the other terminal 14 via a sensor 26. During operation, the sensor 26 detects the electrical current flowing through the circuit breaker 12, i.e., the current flowing between the two terminals 14. The main current path 24 is part of a hybrid circuit breaker 28, which has a secondary current path 30 connected in parallel to the main current path 24 and is thus also directly electrically connected to one of the terminals 14. The secondary current path 30 is also connected to the remaining terminal 14 via the sensor 26.

[0050] The main current path 24 has a disconnecting element 32, which is configured as a contactor or relay. The disconnecting element 32 is electrically connected in series with another semiconductor switch 34, which is configured as a MOSFET. The second semiconductor switch 34 is selected such that, when electrically conductive (i.e., closed), it exhibits only minimal electrical losses. Therefore, the maximum electrical voltage that can be switched by the second semiconductor switch 34 is limited.

[0051] The bypass path 30 includes a semiconductor switch 36, which is also a MOSFET. The maximum switching voltage achievable via semiconductor switch 36 is higher compared to the other semiconductor switch 34, which is why the losses that occur are increased when an electric current is conducted via semiconductor switch 36. A further isolating element 38, designed as a relay, is electrically connected in series with semiconductor switch 36.

[0052] In summary, both the main current path 24 and the secondary current path 30 each have one of the isolating elements 32, 38 and one of the semiconductor switches 34, 36, which are each electrically connected in series. The corresponding components are not identical. The two isolating elements 32, 38 are each galvanically isolated when they are in the electrically non-conductive state, i.e., open. The two isolating elements 32, 38 are each mechanical switching elements, whereas the semiconductor switches 34, 36 are electrical switching elements and are not galvanically isolated.

[0053] The separating elements 32, 38 and the semiconductor switches 34, 36 are actuated by means of a control circuit 40 of the hybrid switch 28, so that by means of the control circuit 40 they can each be switched – at least in principle independently of each other – into the electrically conductive or the electrically non-conductive state. The control circuit 40 is supplied with electrical energy via a supply connection (not shown) and is connected to the sensor 26 via a signal transmission link.

[0054] Furthermore, the control circuit 40, as well as the main current path 24, 30 and the sensor 26, are arranged in a housing 42 of the circuit breaker 12, which is made of plastic. Consequently, the isolating element 32, the semiconductor switch 36, and the control circuit 40 are enclosed by the housing 42. Thus, the individual components are protected from mechanical damage. However, the housing 42 is not pressure-tight and is designed to be gas-permeable, so that the gas 22 present in the surrounding area 24 can also penetrate into the interior of the housing 42.

[0055] When the actuator 18 is operated, the isolating element 32 and the additional semiconductor switch 34 are in the electrically conductive state. In contrast, the semiconductor switch 36 is in the electrically non-conductive state, and the additional isolating element 38 is in the electrically conductive state, for which a corresponding control is effected by the control circuit 40. Thus, electrical current flowing between the two terminals 14 is routed via the sensor 26 and only via the main current path 24, whereas no electrical current flows via the secondary current path 30. The losses arising in the circuit breaker 12 are comparatively low, since the losses arising from the mechanical switch used as the isolating element 32 are negligible, and the additional semiconductor switch 34 is selected accordingly.The low ohmic losses in the hybrid switch 28 cause the gas 22 contained within it to heat up. This gas can then escape from the housing 42, thus dissipating heat. This prevents local overheating in the circuit breaker 12, which could otherwise lead to an explosion of the gas 22.

[0056] The flowing electric current is monitored by sensor 26. If the flowing electric current exceeds a certain limit for a specific period, namely four times the rated current, i.e., 480 A, the control circuit 40 detects that an overcurrent has occurred. This is caused, for example, by a malfunction of actuator 18 or by a short circuit between the two lines 16 and 20. To prevent further damage to actuator 18, contamination of gas 22, and ignition of gas 22, it is necessary to interrupt the operation of actuator 18. Therefore, the circuit breaker 12 is used to protect actuator 18 in the potentially explosive atmosphere 24.

[0057] To interrupt the current flow through the circuit breaker 12 in the event of an overcurrent or other triggering event, such as a short circuit, the control circuit 40 first puts the further disconnecting element 38 into the electrically conductive state, if it is not already in the electrically conductive state. Following this, the semiconductor switch 36 is put into the electrically conductive state, so that the electrical current, which previously flowed exclusively through the main current path 24, can at least partially commutate onto the secondary current path 30. In other words, a portion of the electrical current flowing through the circuit breaker 12 is now also carried via the secondary current path 30.

[0058] Following this, the second semiconductor switch 34 is opened, interrupting the flow of electrical current through the main current path 24. Since the secondary current path 30 is electrically conductive, the electrical current now flows through it. The resulting electrical voltage between the terminals 14 is slightly increased due to the increased resistance of the components of the secondary current path 30. However, such an electrical voltage can be easily switched by means of the second semiconductor switch 34. Subsequently, the semiconductor switch 36 is opened, interrupting the flow of electrical current through the secondary current path 30 as well. Thus, no electrical current flows between the terminals 14. Subsequently, the two isolating elements 32 and 38 are opened, thereby galvanically isolating the two terminals 14 from each other.

[0059] Subsequently, no electrical current flows to the actuator 18, at least not via line 16, and the operation of the actuator 18 is discontinued. Furthermore, the actuator 18 is galvanically isolated from one of the supply lines 8 by the circuit breaker 12. In summary, the circuit breaker 12 is in its non-conductive state. No arcing occurs when the circuit breaker 12 switches from the conductive to the non-conductive state, so the circuit breaker 12 can be safely used to protect the actuator 18 despite the potentially explosive atmosphere 24.

[0060] The invention is not limited to the embodiment described above. Rather, other variants of the invention can also be derived by a person skilled in the art without departing from the subject matter of the invention. In particular, all individual features described in connection with the embodiment can also be combined with one another in other ways without departing from the subject matter of the invention. Reference symbol list

[0061] 2 Room 4 Wall 6 Control cabinet 8 Supply line 10 Busbar 12 Circuit breaker 14 Connection 16 Line 18 Actuator 20 Additional line 22 Gas 24 Main current path 26 Sensor 28 Hybrid switch 30 Secondary current path 32 Disconnect element 34 Additional semiconductor switch 36 Semiconductor switch 38 Additional disconnect element 40 Control circuit 42 Housing

Claims

1. Circuit breaker (12) for operation in a potentially explosive atmosphere (24) comprising a hybrid switch (28) having a main current path (24) with a disconnecting element (32) and a secondary current path (30) connected in parallel to the main current path (24) with a semiconductor switch (36) and a control circuit (40) by means of which the disconnecting element (32) and the semiconductor switch (36) are actuated.

2. Circuit breaker (12) according to claim 1, characterized by a housing (42) by means of which the separating element (32), the semiconductor switch (36) and the control circuit (40) are enclosed.

3. Circuit breaker (12) according to claim 2, characterized by that the housing (42) is not pressure-tight encapsulated.

4. Circuit breaker (12) according to one of claims 1 to 3, characterized by thatthe bypass path (30) has a further separating element (38) which is electrically connected in series with the semiconductor switch (36) and which is actuated by means of the control circuit (40).

5. Circuit breaker (12) according to one of claims 1 to 4, characterized by that the main current path (24) has a further semiconductor switch (34) which is electrically connected in series with the separating element (32) and which is actuated by means of the control circuit (40).

6. Space (2) filled with an explosive atmosphere (22) and in which an electrical actuator (18) and a circuit breaker (12) according to one of claims 1 to 5 are arranged, wherein the actuator (18) and the circuit breaker (12) are electrically connected by means of an electrical line (16).

7. Room (2) according to claim 6, characterized by a control cabinet (6) in which the circuit breaker (12) is arranged.

8. Room (2) according to claim 7, characterized by that the control cabinet (6) is not pressure-tight encapsulated.

9. Use of a protective switch (12) according to one of claims 1 to 5 for protecting an actuator (18) in an explosive atmosphere (24).

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