protective switch

Abstract

The invention relates to a protective switch, in particular for use in an explosion-endangered environment (24). The protective switch (12) comprises a hybrid switch (28) having a main current path (24) with an isolating element (32) and a secondary current path (30) parallel to the main current path (24) with a semiconductor switch (36), and a control circuit (40) by means of which the isolating element (32) and the semiconductor switch (36) are actuated. The invention also relates to the use of a space (2) and a protective switch (12).

Description

Technical Field

[0001] This invention relates to a protective switch and its application. The protective switch has a hybrid switch having a main current path and a secondary current path connected in parallel with the main current path. Furthermore, this invention also relates to a space. Background Technology

[0002] Increasingly, electricity is being generated from renewable energy sources, such as solar or wind power. Since this electricity is not continuous or available only when needed, storage solutions are required. One possibility is to use this electricity to produce hydrogen and store it. It is also possible to use the hydrogen produced in this way for other purposes, such as to enhance the concentration of natural gas or for use in motor vehicles. However, producing hydrogen from electricity, especially through electrolysis, requires relatively high currents.

[0003] Overcurrent may occur when an actuator experiences a short circuit or when the power supply line to the actuator is damaged. This overcurrent can cause further damage to the actuator or may lead to a reverse reaction in the power supply network that powers the actuator. Therefore, it is necessary to interrupt this overcurrent relatively quickly. For this purpose, a protective switch is typically used, which is connected to the power line that powers the respective actuator. When an overcurrent occurs in the line—that is, when the current guided through the line exceeds a certain threshold—the protective switch is activated, thereby interrupting the current flowing through the line and thus to the actuator.

[0004] Protective switches typically have a switching element that is triggered in a manner dependent on a signal provided by a sensor. It is possible that the sensor and the switching element exist as a common structural unit, for example, as a bimetallic trip piece. In the current-carrying / closed state, the bimetallic trip piece rests against a mating contact and carries the current through that contact. When the current exceeds a threshold value, the bimetallic trip piece is heated to varying degrees and thus bends. This bending causes the bimetallic trip piece to space away from the mating contact, thereby interrupting the current. If the current carried by the protective switch is relatively large and the applied voltage is greater than, for example, 60 V, it is possible that an electric arc is formed between the bent bimetallic trip piece and the mating contact, through which the current continues to carry.

[0005] If such a protective switch is used in hydrogen production and is not designed to be airtight, it is possible that hydrogen gas entering the switch could be ignited. To address this problem, the protective switch is usually located in a separate connection room within the industrial facility where hydrogen is present, outside the space where the hydrogen is present. This necessitates relatively long wiring, thereby increasing manufacturing costs and the likelihood of failure. Reactivating the actuator after the protective switch is triggered also becomes complicated because it is impossible to visually inspect the actuator and its response when the switch is back on.

[0006] As an alternative, the protective switch is designed to be hermetically sealed and housed within the space containing the actuator. When an electric arc is generated within the protective switch, the pressure inside increases at least locally, but the increase exceeds 10 bar. At this point, the protective switch must remain hermetically sealed even under such high pressure, which increases the requirements for its housing. This, in turn, increases the structural dimensions and manufacturing cost of the protective switch.

[0007] A hybrid switch (hybrid disconnecting switch) is known from WO 2010 / 108565 A1, which has a mechanical switch or isolating element and a semiconductor electronic device connected in parallel with the mechanical switch or isolating element. The semiconductor electronic device includes a semiconductor switch, preferably an IGBT. The semiconductor electronic device has no additional energy source and is in a current-blocking state when the mechanical switch is closed, that is, practically no current and no voltage. To achieve current interruption via this hybrid switch, the mechanical switch is opened, wherein an electric arc may be generated. The energy of the electric arc generated when the mechanical switch is opened is utilized by the semiconductor electronic device, wherein the semiconductor electronic device is interconnected with the mechanical switch such that when the mechanical switch is opened, the arc voltage (due to the electric arc) of the mechanical switch switches the semiconductor switch into an electrically conducting state.

[0008] Once the semiconductor switch is switched to the on state, current begins to flow from the mechanical switch to the semiconductor switch. The corresponding arc voltage, or arc current, also charges the energy storage device, in the form of a capacitor, which provides control voltage to the semiconductor electronic device. Once the current has flowed to the semiconductor switch, the arc extinguishes and the charging process of the energy storage device ends. At this point, ionized gas exists between the switch contacts of the mechanical switch; this ionized gas is generated by the arc and gradually dissipates over time. After the charging process is complete, a timing cycle begins, during which the energy storage device keeps the semiconductor switch in the current-leading state. After the timing cycle expires, the semiconductor switch is switched back to the current-blocking state. Summary of the Invention

[0009] The objective of this invention is to provide a particularly suitable protective switch, a particularly suitable space, and a particularly suitable application of the protective switch, wherein manufacturing costs are suitably reduced and / or safety is improved.

[0010] According to the invention, the task concerning the protection switch is solved by the feature of claim 1, concerning space by the feature of claim 6, and concerning application by the feature of claim 9. Advantageous designs and improvements are the subject of their respective dependent claims.

[0011] Protective switches are used to provide electrical protection for lines and / or actuators energized by a line or such line during operation. In particular, the protective switch is in electrical contact with the line and is suitably and specifically designed for this purpose. Suitably, the protective switch has one or preferably two terminals, which are suitable for, and particularly are designed and configured to connect the line or such line to the circuit at these terminals respectively. These terminals are designed, for example, according to the type of receptacle used for busbars, cable connectors, or insulating piercing contacts.

[0012] In particular, the protective switch is configured to interrupt the current flowing through it when an overcurrent, for example, reaches four times the rated current (i.e., the current flowing through the protective switch during normal operation). Suitably, the protective switch includes a sensor for detecting the current flowing through it, thereby enabling the detection of the overcurrent. Alternatively or in combination, the protective switch is configured to identify short-circuit currents up to 10,000 A or to identify a so-called "arc" in the actuator / line, and subsequently interrupt the current flowing through the protective switch.

[0013] A protective switch is constructed such that when the current induced by the protective switch exceeds a boundary value, the current is interrupted. The boundary value may be static, application-specific, or time-dependent. For example, the protective switch may interrupt the current as soon as the boundary value is exceeded, or only if the boundary value is exceeded for a specific period of time. The protective switch may have a control input, and by means of a signal received via the control input, the protective switch may be placed in an electrically conductive or non-conductive state. Therefore, it is also possible to remotely control the protective switch, i.e., operate it from a distance, which improves convenience.

[0014] Protective switches are, for example, suitable for, and particularly configured and established to withstand voltages greater than 220 V or 500 V and, for example, less than 2000 V when the protective switch is in a non-conducting state. Suitably, protective switches are used to protect voltages between 400 V and 1500 V, and for example, 650 V and 800 V, and are suitable for, configured and / or established for this purpose.

[0015] Protective switches are used, for example, in alternating current systems to guide alternating current during operation. However, particularly preferably, protective switches are used in direct current systems and thus for the protection of direct current circuits. In other words, direct current is guided by the protective switch during normal operation. Suitablely, the current guided by the protective switch during normal operation is greater than 10 A, 20 A, or 50 A. In particular, the rated current, i.e., the maximum current guided by the protective switch during normal operation, is less than 200 A or 150 A.

[0016] The protective switch is designed for safe operation in environments with explosion hazards and is installed and configured for this purpose. In other words, the protective switch is used in environments with explosion hazards. Therefore, when the protective switch is in operation, its environment, i.e., the location adjacent to the protective switch, may contain (flammable) and / or explosive gases, such as hydrogen (H2), which are particularly mixed with oxygen (O2). Alternatively or in combination, gasoline vapors or other flammable gases or dust may be present in the environment of the protective switch. In an alternative, the protective switch is installed, for example, in a flammable / explosive liquid. In the presence of a spark, especially when locally overheated, the gas / dust in the environment of the protective switch will undesirably explode or at least be ignited. Preferably, the protective switch is therefore designed for operation in areas with explosion hazards in accordance with "Richtlinie 1999 / 92 / EG". The provisions of Directive 1999 / 92 / EG: "Mindestvorschriften zurVerbesserung des Gesundheitsschutzes und der Sicherheit der Arbeitnehmer, die durch explosionsfähige Atmosphären geefährdet werden können" (Regarding the minimum requirements for improving the health protection and safety of workers potentially exposed to explosive atmospheres) stipulate that protective switches preferably meet the requirements for use in Zone 0 or Zone 20. Alternatively, protective switches may suitably meet the requirements for use in Zone 1 or Zone 21. Protective switches may, for example, meet the requirements for use in Zone 2 or Zone 22.

[0017] The protective switch is configured to prevent localized heating of the environment, so that even if the current flowing through the protective switch is interrupted, there will be no ignition of gases or other explosive substances in the environment of the protective switch.

[0018] The protective switch includes a hybrid switch, which is an isolating device, i.e., a switching unit / transfer unit. When the protective switch is in the on state, the hybrid switch is also in the on state and guides current during operation. When the protective switch is in the off state, the hybrid switch is also in the off state. Suitably, the hybrid switch is driven by signals provided by possible sensors, thereby providing the functionality of the protective switch.

[0019] The hybrid switch has a main current path, which is formed, or at least connected, between two terminals of the protective switch. The main current path has an isolation element that can be operated. It is possible that the isolation element is in a closed state, in which the main current path is particularly low-ohmic, thereby allowing suitable current flow between the two terminals, particularly between the two ends of the main current path. Conversely, in the open state, the isolation element is designed to be high-ohmic, thereby making current flow through the main current path essentially impossible, or thus resulting in at least an increased ohmic resistance. In summary, the isolation element is electrically conductive in the closed state and non-conductive in the open state.

[0020] Suitablely, if the isolating element is disconnected, it is a component for current isolation. The isolating element is suitably a mechanical switch, such as a relay, contactor, or plug, or at least one of these. Alternatively, the isolating element is designed according to the type of overvoltage protector. The isolating element is particularly suitable, and preferably configured, to provide current isolation to the main current path when disconnected, i.e., when placed in the open / closed state.

[0021] The hybrid switch also has a secondary current path, which includes a semiconductor switch. Specifically, the semiconductor switch is connected in parallel with an isolation element, such that the isolation element is bridged by means of the semiconductor switch. Alternatively, other components of the primary current path may also be bridged by means of the semiconductor switch. The semiconductor switch is suitably a power semiconductor switch and preferably a field-effect transistor, such as a MOSFET, or an IGBT or GTO. Particularly here, during normal operation, i.e., when a current should flow through the hybrid switch, the semiconductor switch is in a current-blocking state. Therefore, the electrical losses of the protective switch during operation are relatively small. In the open state, the semiconductor switch is designed to be high-ohmic, making it virtually impossible for current to flow through it. In other words, the semiconductor switch is in a non-conducting state in the open state. In the closed state, the semiconductor switch is low-ohmic and therefore in a conducting state.

[0022] The protective switch also includes a drive control circuit that operates the isolating element and the semiconductor switch. In other words, the drive control circuit is configured to operate the isolating element and the semiconductor switch, thereby placing them in an electrically conductive or electrically deconductive state. Specifically, a specific voltage is applied to their respective control inputs for operation. Suitably, the drive control circuit operates the isolating element and / or the semiconductor switch when the current flowing through the protective switch should be interrupted. In particular, the drive control circuit is signal-technically connected to any possible sensor, and during operation, the drive control circuit evaluates the signals provided by the sensor.

[0023] Preferably, the control of the isolation element / semiconductor switch is based on the interconnection of the control circuit. This interconnection is constructed, for example, by discrete components, such as electrical components, i.e., resistors, capacitors, diodes, or inductors. Preferably, the control circuit includes an application-specific integrated circuit (ASIC) and is formed, for example, by means of such ASIC. Alternatively or in combination with this, the control circuit has a computer, which is suitably designed to be programmable.

[0024] When the protective switch is electrically conductive, i.e., when current should be guided by the protective switch, especially when the isolating element is electrically conductive and the semiconductor switch is electrically inactive, they are suitably driven by a control circuit. If the current flowing through the protective switch should be interrupted, especially when there is a triggering event, such as an overcurrent, short-circuit current, or arc, the control circuit suitably disconnects the isolating element and (at least briefly) closes the semiconductor switch.

[0025] For example, to interrupt the current flowing through the protective switch, the semiconductor switch is first closed, allowing the current flow to be diverted from the main current path to the secondary current path. Then, the isolation element is opened, where, since the secondary current path is electrically conductive, no arcing occurs when the isolation element is opened. Subsequently, the semiconductor switch is opened, i.e., placed in a non-conductive state, thus interrupting the current flowing through the secondary current path. Therefore, the protective switch will subsequently transition to a non-conductive state, where no arcing occurs. In this way, essentially no or only slight heating of the protective switch occurs. Therefore, any flammable / explosive gases present will not be ignited.

[0026] Alternatively, the isolation element may be disconnected first, where an arc may have formed. Therefore, an (undesirable) current continues to flow through the main current path. The voltage drop across the isolation element caused by the arc is used specifically to put the semiconductor switch into an electrically conducting state, thereby diverting current flow from the main current path to the secondary current path and interrupting current flow through the main current path. Specifically, the energy storage device is charged with the voltage drop across the isolation element before closing the semiconductor switch. After the arc in the isolation element is quenched, the semiconductor switch remains electrically conducting for a short period using the energy stored in the energy storage device. When the arc has ceased and the energy storage device has discharged, the semiconductor switch is placed into a non-conducting state, where, due to cooling during this period, the reignition of the arc in the isolation element will not occur. In this design, in particular, no additional energy supply for the drive circuit is required.

[0027] In an alternative design, the drive circuit is designed to, for example, first disconnect an isolation element, where an arc may have formed. The isolation element is specifically configured such that the longer it remains disconnected, the higher the voltage required to sustain the arc rises. After a specific time window, the semiconductor switch is brought to the on state, causing the current to be switched from the main current path to the secondary current path. Thus, the arc is quenched. Once this process is substantially complete, the semiconductor switch is disconnected substantially immediately again, thus interrupting the current flow. This time window is chosen such that although the semiconductor switch is disconnected relatively quickly, the relatively high voltage required to form the arc prevents reignition.

[0028] In each of the aforementioned feasible methods for interrupting current flow, the duration of the possible arc is relatively short, and the heating is only localized and limited. Because a hybrid switch is used in the protective switch, the environmental load, i.e., the localized heating, is relatively small, thus preventing the ignition of explosive substances, especially explosive gases, even in the environment of the protective switch. Therefore, safe operation of the protective switch can be achieved even in such environments, where the requirements for isolation between the isolating switch and explosive gases are relatively low. This reduces manufacturing costs. Furthermore, since the ignition of explosive / flammable gases in the environment can be essentially eliminated, the safety during operation of the protective switch is improved. Here, based on the main current path with isolation elements, the electrical losses generated during the operation of the protective switch are relatively small, and the semiconductor switch is used for current guiding only when current flow should be interrupted. Therefore, the requirements for the semiconductor switch are relatively low, thus reducing manufacturing and operating costs.

[0029] Suitablely, the protective switch has a mechanical operating part, such as a lever, which allows the protective switch to change its (switching) state, i.e., whether it conducts current or not. In particular, the drive circuit relies at least in part on mechanical operation. Thus, the application range of the protective switch is expanded.

[0030] In particular, the protective switch has a housing that encloses the isolating element, semiconductor switch, and drive circuitry. This housing provides mechanical protection, facilitating the installation of the protective switch. Specifically, the housing is designed to be rigid and, for example, made of plastic. This reduces manufacturing costs. The housing is designed to be pressure-resistant, thus isolating the interior and exterior of the housing from each other pressure-technically. Therefore, it is possible for a pressure difference to exist between them. Suitablely, the housing is not airtight, i.e., it is hermetically sealed. For example, the pressure resistance is less than 1 bar. Therefore, if the overpressure in the housing exceeds 1 bar, damage to the housing, for example, will occur. This lower pressure resistance reduces the requirements for the housing, thus reducing manufacturing costs.

[0031] The housing is, for example, a pressure-resistant enclosure. This improves safety. However, it is particularly preferred that the housing is not a pressure-resistant enclosure. In other words, the housing therefore does not particularly meet the requirements of the European standard "EN 60079-1 ExplosionsfähigeAtmosphäre (Explosive Atmospheres)," and suitably does not meet Part 1 of that standard, "Geräteschutz durchdruckfeste Kapselung." (The requirement of "(device protection via a pressure-resistant package 'd')" is met. In this way, the requirements for the housing are reduced, and thus the manufacturing cost is reduced. No certification is required, which further reduces manufacturing costs. Preferably, the housing is also breathable. Therefore, gas exchange between the inside and outside of the housing is possible, thus enabling heat dissipation from the housing to the environment. Preferably, the housing has multiple openings, such as slits, to uniformly distribute gas exchange. For example, during operation, the protection switch, especially the isolation element / semiconductor switch, is prevented from overheating. Here, the isolation element and semiconductor switch are particularly controlled such that no arc is generated when the current is interrupted, or at least controlled in such a way that any possible arcing and localized heating are insufficient to ignite gases from the environment, especially those partially entering the housing. Suitably, the control circuit is configured for this purpose. In summary, especially due to the presence of a hybrid switch, it is possible to interrupt the current flowing through the protection switch without forming an arc, thus preventing gas ignition even though the housing is not a pressure-resistant package.

[0032] The secondary current path may consist of only a semiconductor switch. However, particularly preferably, the secondary current path also includes an additional isolation element electrically connected in series with the semiconductor switch. This additional isolation element may have the same or different structure as the original isolation element. In particular, the additional isolation element is current-isolated, which improves safety. Based on this additional isolation element, current disconnection of the secondary current path can be achieved, thus allowing the complete switch to be designed as current-isolated. This further enhances safety.

[0033] For example, another isolating element is a mechanical switch, and preferably a relay. This other isolating element is also operated by a drive circuit. Specifically, during operation, the other isolating element is always closed before the semiconductor switch is closed, and the other isolating switch is always opened only after the semiconductor switch is opened. Therefore, no arc is ever formed in the other isolating element, because the switch state only changes when no current flows through the secondary current path. Suitablely, the drive circuit is designed and established for this purpose. The corresponding operation of the other isolating element is performed, for example, based on the corresponding interconnection method of the drive circuit.

[0034] The main current path may have only an isolation element. However, particularly preferably, the main current path also includes an additional semiconductor switch, which may have the same structure as or suitably differ from the semiconductor switch. In particular, electrical losses during current conduction are prevented in the additional semiconductor switch compared to the semiconductor switch, where, for example, the switching capability of the additional semiconductor switch is weakened, thus reducing manufacturing costs. The additional semiconductor switch is electrically connected in series with the isolation element and is operated by means of a drive circuit. When the protective switch conducts the (desired) current, both the additional semiconductor switch and the isolation element are electrically conductive, i.e., closed. To interrupt the current flow through the protective switch, the semiconductor switch is first closed, thereby diverting at least partially the current from the main current path to the secondary current path. Subsequently, the additional semiconductor switch is opened, thereby completely interrupting the current flow through the main current path. At this time, the voltage drop through the additional semiconductor switch is relatively small. Only after this is the isolation element opened, whereby an arc is not formed because the current flow has been interrupted. Furthermore, the semiconductor switch is operated, thus interrupting the current flow through the secondary current path as well. Here, the timing of disconnecting the isolating element is independent of the timing of disconnecting the semiconductor switch. Under this control, the protective switch can be used even in environments with flammable gases, ensuring that no electric arc occurs.

[0035] The space is filled with an explosive atmosphere. This atmosphere is, for example, a gas, such as a mixture of hydrogen and oxygen. Alternatively, gasoline vapor or the like may be present in the space as an explosive gas. In another alternative, the atmosphere is, for example, a mixture of dust and air, particularly containing oxygen or other oxidizers. However, at least the atmosphere is such that an exothermic reaction, such as an explosion or at least ignition, occurs upon localized overheating. The space is provided, for example, by means of a building or the like, and its outer walls are made, for example, of stone or concrete. Alternatively, the space is provided, for example, by means of furniture such as cabinets or the like. Preferably, the space is designed to be airtight and / or pressure-resistant enclosed.

[0036] An electric actuator is arranged in the space. By means of the electric actuator, which is also simply referred to as an actuator, a specific activity is performed during operation, wherein an electric current is required to perform the activity. In particular, an atmosphere is generated by means of the actuator, preferably a gas or a component of a gas. Alternatively, the gas is used, for example, to prevent chemical reactions that would otherwise occur due to the operation of the actuator, or to further process the gas or workpiece by means of the actuator, during which the atmosphere is at least partially generated. For example, the space is a tank, and the gas is generated, for example, due to the evaporation of a liquid arranged in the tank. Here, the actuator is, for example, a pump. However, particularly preferably, the actuator is an electrolytic device, and when energized, it performs the electrolysis of water to produce hydrogen and oxygen.

[0037] A protective switch is arranged in the space, wherein the actuator and the protective switch are connected to each other by electrical lines. When the actuator is energized, the current required for this purpose is directed through the protective switch and is, in particular, monitored. Here, suitably, the protective switch is operated in the event of an overcurrent, such as a specific multiple of the rated current used in normal operation, in the event of a short-circuit current, or in the event of other faults, thereby preventing energization of the actuator and thus preventing its further operation. In particular, the protective switch includes terminals to which the electrical lines are connected, and the remaining end of the electrical lines is connected to the actuator.

[0038] The protective switch has a hybrid switch, which includes a main current path with an isolation element, a secondary current path with a semiconductor switch connected in parallel with the main current path, and a drive circuit. The drive circuit operates the isolation element and the semiconductor switch. Preferably, the main current path, and thus the secondary current path, is directed to one or more terminals of the protective switch and, in particular, is connected between these terminals. When the protective switch is electrically conductive, i.e., in the closed state, the main current path directs the current required to energize the actuator.

[0039] Because the actuator and the protective switch are arranged together in this space, the required length of the wiring (which is simply referred to as a line) is relatively short, thus reducing manufacturing costs. For example, when the protective switch is manually operated, the actuator's response is visible when it is placed in an electrically conductive state, which facilitates fault finding, for example.

[0040] The protective switch is, for example, fastened to the actuator, which reduces the required structural space. Alternatively, the protective switch is, for example, fastened to the wall of the space, thereby enabling individual replacement of the actuator and the protective switch, for example, for maintenance or in case of failure. However, it is particularly preferred that the space has a switch cabinet in which the protective switch is arranged. The switch cabinet is suitably fastened to the wall of the space. The switch cabinet here prevents the protective switch from being mechanically damaged. Furthermore, the switch cabinet facilitates the replacement of the protective switch, for example, when the requirements for the actuator have changed. The switch cabinet also facilitates the installation of the protective switch in the space. Preferably, the switch cabinet is configured to accommodate multiple protective switches. Multiple protective switches are arranged in particular in the switch cabinet, wherein, for example, there are multiple actuators in the space, wherein, for example, at least some of the actuators are structurally identical. Suitably, each actuator is assigned a separate protective switch. Here, the installation is simplified by the switch cabinet.

[0041] Switchgear is, for example, impermeable and / or pressure-resistant. This improves safety. However, it is particularly preferred that the switchgear is not pressure-resistant encapsulated. Therefore, the switchgear does not, in particular, meet the requirements of the European standard "EN 60079-1 Explosive Atmospheres, Part 1: Protection of Equipment by Pressure-Resistant Encapsulation 'd'". In this way, the requirements for the switchgear are reduced, and thus manufacturing costs are lowered. No certification is required, which further reduces manufacturing costs. It is particularly possible to use any type of switchgear. Suitably, the switchgear is ventilated. This facilitates heat dissipation from the switchgear, thus preventing localized overheating, which could, for example, lead to the ignition of explosive gases and / or damage to the protective switch. Furthermore, it is possible to use standard components or at least existing design structures for the switchgear, thus reducing manufacturing costs. Because the design structure is based on the protective switch, the formation of an electric arc is avoided when the protective switch is switched, i.e., when the switching state of the protective switch changes, i.e., when the current flowing through the protective switch is interrupted or begins, thus there are essentially no requirements for the switchgear regarding explosion suppression.

[0042] In particular, a protective switch, including a hybrid switch, is used to protect actuators. Here, the protective switch is placed in an environment with an explosion hazard, especially in an area with an explosion hazard. Therefore, an explosive / flammable fluid, such as a gas or liquid, is present directly adjacent to the protective switch. The hybrid switch has a main current path with an isolation element and a secondary current path connected in parallel with the main current path, with a semiconductor switch, and a drive circuit that operates the isolation element and the semiconductor switch. Based on the design of the protective switch, the formation of an electric arc is avoided, or its duration is at least relatively short, when the switching state of the protective switch changes. The change of switching state is implemented to protect the actuator, i.e., when, for example, there is an overload or malfunction of the actuator. The explosion hazard environment in which the protective switch is used meets, for example, the definition of Zone 2 / 22, or preferably Zone 1 / 21, or particularly preferably Zone 0 / 20, as specified in Directive 1999 / 92 / EG: Minimum requirements for improving the health protection and safety of workers potentially exposed to explosive atmospheres.

[0043] The improvements and advantages described in conjunction with the protective switch are also meaningfully applied to the space / application and to each other, and vice versa. Attached Figure Description

[0044] The embodiments of the present invention will be further described below with reference to the accompanying drawings. In the drawings:

[0045] The only accompanying drawing schematically shows the space containing the actuator and protective switch. Detailed Implementation

[0046] In the sole accompanying drawing, space 2 is schematically simplified in perspective view. Space 2 is realized by means of a building not shown in detail and has multiple walls 4, three of which are shown. Access to space 2 is achieved via an airlock not shown in detail. A switch cabinet 6 is fixedly mounted on one of the walls 4, and the switch cabinet is shown translucently. Thus, the switch cabinet 6 is arranged in space 2.

[0047] Two power supply lines 8 extend into the switch cabinet 6. One power supply line is in electrical contact with the busbar 10 arranged in the switch cabinet 6. The other power supply line 8 is in electrical contact with the protective switch 12 arranged therein. Here, the power supply line 8 is connected to one of the two terminals 14 of the protective switch 12. Since the protective switch 12 is arranged in the switch cabinet 6 located in space 2, the protective switch 12 is also arranged in space 2. A line 16 is connected to the other terminal 14 of the protective switch 12. This line leads out of the switch cabinet 6 and to the (electrical) actuator 18, which is also arranged in space 2. In summary, the actuator 18 and the protective switch 12 are thus electrically connected by the (electrical) line 16. The busbar 10 is connected in the switch cabinet 6 to another line 20, which is also connected to the actuator 18.

[0048] For the operation of actuator 18, it is supplied with electrical energy via two lines 16 and 20 and thus via switch cabinet 6, which is provided by power supply line 8. Here, the voltage existing between the two power supply lines 8 and therefore also between the two lines 16 and 20 is greater than 400 V, and in the example shown, it is equal to 650 V. The current guided by lines 8, 16, and 20 is direct current, which is 120 A.

[0049] When actuator 18 operates, it performs electrolysis of water, producing hydrogen (H2) and oxygen (O2). The hydrogen is at least partially introduced into space 2 and guided from the otherwise airtight space 2 to a container or similar via a suction system (not shown in detail). Therefore, based on the operation of actuator 18, an explosive gas 22, namely hydrogen, mixed with a small amount of oxygen, is generated in space 2. Here, the switch cabinet 6, in which the protective switch 12 is arranged, is not pressure-resistant and is permeable, allowing a portion of the gas 22 to advance forward to the protective switch 12. Thus, the protective switch 12 is positioned in an atmosphere 24 with a potential explosion hazard, and the explosive gas 22 is at least partially directly adjacent to the protective switch 12.

[0050] When actuator 18 operates, the required current flows between the two terminals 14 of protective switch 12, which has a main current path 24 through which the two terminals 14 are electrically connected. One end of the main current path 24 leads 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 sensor 26. Sensor 26 detects the current flowing through protective switch 12 during operation, i.e., the current flowing between the two terminals 14. The main current path 24 is part of hybrid switch 28, which also has a secondary current path 30 connected in parallel with the main current path 24, and this secondary current path is also directly electrically connected to one of the terminals 14. The secondary current path 30 is also connected to the remaining terminal 14 via sensor 26.

[0051] The main current path 24 has an isolation element 32, which is configured as a contactor or relay. The isolation element 32 is electrically connected in series with another semiconductor switch 34, which is designed as a MOSFET. Here, the other semiconductor switch 34 is selected to have minimal electrical losses when it is electrically turned on, i.e., closed. Therefore, the maximum voltage to be switched by means of the other semiconductor switch 34 is limited.

[0052] The secondary current path 30 has a semiconductor switch 36, which is also a MOSFET. Here, the maximum voltage that can be switched by means of semiconductor switch 36 is higher than that of the other semiconductor switch 34, thus increasing the losses when current is guided by semiconductor switch 36. An additional isolation element 38, configured as a relay, is connected in series with semiconductor switch 36.

[0053] In summary, both the main current path 24 and the secondary current path 30 have one of the isolation elements 32 and 38, and one of the semiconductor switches 34 and 36, respectively, which are connected in series. The corresponding components are not structurally identical. When the two isolation elements 32 and 38 are in a non-conductive state, i.e., open, they are configured as current-isolated. The two isolation elements 32 and 38 are mechanical switching elements; conversely, the semiconductor switches 34 and 36 are electrical switching elements and are not current-isolated.

[0054] Isolating elements 32 and 38, as well as semiconductor switches 34 and 36, are all operated by the drive circuit 40 of the hybrid switch 28, which allows them to be placed in an electrically conductive state or a electrically inactive state, respectively (at least in principle independently of each other). The drive circuit 40 is powered via a power supply terminal not shown in detail and is technically connected to the sensor 26.

[0055] Furthermore, the drive control circuit 40, along with the main current paths 24 and 30 and the sensor 26, is housed within the protective switch 12 housing 42, which is made of plastic. Thus, the housing 42 encloses the isolation element 32, the semiconductor switch 36, and the drive control circuit 40, thereby protecting each component from mechanical damage. However, the housing 42 is designed not to be pressure-resistant and is permeable, allowing the gas 22 in the environment 24 to also advance into the interior of the housing 42.

[0056] When actuator 18 is operating, both isolating element 32 and the additional semiconductor switch 34 are electrically conductive. Conversely, semiconductor switch 36 is electrically inactive, and additional isolating element 38 is electrically conductive, for which it is driven by the drive control circuit 40. Thus, the current flowing between the two terminals 14 is guided via sensor 26 and only via the main current path 24; conversely, no current flows via the secondary current path 30. The losses generated in the protective switch 12 are relatively small because the losses generated in the mechanical switch used as isolating element 32 are negligible, and the additional semiconductor switch 34 is appropriately selected. The small ohmic losses in the hybrid switch 28 cause the gas 22 located therein to be heated, which can flow out from housing 42, resulting in heat dissipation. This avoids localized overheating in the protective switch 12, which could otherwise lead to an explosion of gas 22.

[0057] The flowing current is monitored by sensor 26. If the flowing current exceeds a specific threshold value, that is, more than four times the rated current, i.e., 480 A, and persists for a specific period of time, an overcurrent is detected by the drive control circuit 40. This overcurrent may be 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, to prevent contamination of gas 22, and to prevent the gas 22 from being ignited, it is necessary to interrupt the operation of actuator 18. Therefore, protective switch 12 is used to protect actuator 18 in an atmosphere 24 with an explosion hazard.

[0058] To interrupt the current flowing through the protection switch 12 in the event of an overcurrent or other triggering event such as a short circuit, the additional isolation element 38 is first brought into a conducting state by means of the drive control circuit 40 if it is not already in a conducting state. Subsequently, the semiconductor switch 36 is brought into a conducting state, so that the current previously guided solely through the main current path 24 can also be at least partially diverted to the secondary current path 30. In other words, a portion of the current guided through the protection switch 12 is now also guided via the secondary current path 30.

[0059] Subsequently, the other semiconductor switch 34 is disconnected, thereby interrupting the current through the main current path 24. Since the secondary current path 30 is electrically conductive, current will now flow through the secondary current path. Due to the increased resistance of the components of the secondary current path 30, the voltage obtained between the terminals 14 is slightly increased. However, this voltage can be smoothly switched using the other semiconductor switch 34. Subsequently, the semiconductor switch 36 is disconnected, thereby now interrupting the current flow through the secondary current path 30 as well. Therefore, there is no current between the terminals 14. Subsequently, the two isolation elements 32 and 38 are disconnected, thereby isolating the two terminals 14 from each other.

[0060] Subsequently, no current flows to actuator 18, or at least no current flows through line 16, and operation of actuator 18 ceases. Furthermore, actuator 18 is electrically isolated from one of the power supply lines 8 based on protective switch 12. In summary, protective switch 12 is placed in a non-conductive state. Here, no electric arc occurs when protective switch 12 is switched from a conductive state to a non-conductive state, thus allowing protective switch 12 to be safely used to protect actuator 18 even in the potentially explosive environment 24.

[0061] This invention is not limited to the embodiments described above. Conversely, other variations of the invention can be derived by those skilled in the art without departing from the subject matter. Furthermore, in particular, all the individual features described in the embodiments can be combined with each other in other ways without departing from the subject matter.

[0062] List of reference numerals

[0063] 2 Space

[0064] 4 walls

[0065] 6. Switchgear

[0066] 8 Power supply lines

[0067] 10 busbars

[0068] 12 Protective Switch

[0069] 14 terminals

[0070] Line 16

[0071] 18 Actuators

[0072] 20 Other routes

[0073] 22 Gases

[0074] 24 Main Current Path

[0075] 26 sensors

[0076] 28 Mixed Switch

[0077] 30 Secondary Current Path

[0078] 32 Isolation Element

[0079] 34 Other semiconductor switches

[0080] 36 Semiconductor Switches

[0081] 38. Other isolation elements

[0082] 40 Drive control circuit

[0083] 42. Shell

Claims

1. A protective switch (12) for operation in an explosive atmosphere (24), the protective switch comprising a hybrid switch (28) having a main current path (24) with an isolation element (32) and a secondary current path (30) with a semiconductor switch (36) connected in parallel with the main current path (24) and a drive control circuit (40) by means of which the isolation element (32) and the semiconductor switch (36) are operated.

2. The protective switch (12) according to claim 1. Its features have The housing (42) surrounds the isolation element (32), the semiconductor switch (36), and the drive circuit (40).

3. The protective switch (12) according to claim 2. Its features are, The housing (42) is not a pressure-resistant enclosure.

4. The protective switch (12) according to any one of claims 1 to 3. Its features are, The secondary current path (30) has an additional isolation element (38) electrically connected in series with the semiconductor switch (36) and operated by means of the drive circuit (40).

5. The protective switch (12) according to any one of claims 1 to 4. Its features are, The main current path (24) has an additional semiconductor switch (34) electrically connected in series with the isolation element (32), and the additional semiconductor switch is operated by means of the drive circuit (40).

6. A space (2) filled with an explosive atmosphere (22), and in which an electric actuator (18) and a protective switch (12) according to any one of claims 1 to 5 are arranged, wherein, The actuator (18) and the protection switch (12) are electrically connected via a power line (16).

7. The space (2) according to claim 6. Its features have The switch cabinet (6) contains the protective switch (12).

8. The space (2) according to claim 7. Its features are, The switch cabinet (6) is not a pressure-resistant enclosure.

9. The application of the protective switch (12) according to any one of claims 1 to 5 for the protection of the actuator (18) in an environment (24) with an explosion hazard.

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