SWITCHING DEVICE

Description

[0001] The invention relates to a switching device.

[0002] Switching arcs occur when AC or DC circuits are opened, closed, or commutated. These switching arcs typically dissipate the released energy in appropriate quenching devices until the arc is extinguished. Conventional electrical switches attempt to control the resulting switching arcs. This involves considerable technical effort, especially given the increasing number of DC applications where no current zero crossing occurs.

[0003] In previous circuit breakers with single- or double-break contacts, where the arc is guided into ionization arcing chambers, for example, using slot motors, a resulting switching arc is extinguished in the ionization arcing chamber. The problem here is the formation of an ionizing gas at high temperatures, which leads to material loss and contamination of the electrical switch.

[0004] Likewise, an electric current can be switched without switching arcs by a semiconductor switch, which requires complex control electronics and in which reliable galvanic isolation is generally not guaranteed.

[0005] Low-voltage switchgear typically performs protective functions. For example, one of these protective functions is an overcurrent release. This overcurrent release ensures that the circuit is interrupted in the event of a fault. For low rated currents, the response time of the overcurrent release can be in the range of seconds. For higher rated currents, tripping must occur very quickly. The tripping threshold must typically be very finely adjustable.

[0006] In today's conventional switching devices, functional units such as ETUs, TMTUs, or MTUs (Electronic Trip Units, Thermo-Mechanical Trip Units, Magnetic Trip Units) detect an overcurrent and, if necessary, initiate a circuit break. Conventional systems only recognize the switch states ON and OFF.

[0007] US 2012 / 199558 A1 discloses a commutating circuit breaker that operates by the physical movement of a shuttle device that, through at least one set of electrical sliding contacts on the shuttle device, connects the current through the moving shuttle device to a sequence of varying resistances and thus to the circuit, introducing increasing resistance into an electrical circuit. The movement of the shuttle device can be either linear or rotary. At no point are the sliding stator electrodes separated from the matching stationary stator electrodes to create a strong arc that minimizes damage to the sliding stator electrodes. Instead, the current is commutated from one resistance path to the next with sufficiently small resistance changes at each step so that arcing is suppressed.

[0008] EP 3 031 062 A1 discloses a mechanical switch which operates by commutation of the current to an energy-absorbing path or a sequence of paths through at least one blocking semiconductor to open the circuit, wherein the commutation is effected by a sliding movement of at least one pendulum electrode over at least one stationary electrode.

[0009] It is therefore an object of the invention to provide an electrical switching device which enables intermediate states between the ON state and the OFF state of an electrical switch.

[0010] This object is achieved according to the invention by the switching device according to claim 1. Advantageous embodiments of the switching device according to the invention are specified in the subclaims.

[0011] The switching device with an ON state, an OFF state for opening, closing or commutating an electrical circuit between a first contact and a second contact and further intermediate states between the ON and OFF states according to claim 1 comprises a controllable resistance element which is electrically arranged between the first contact and the second contact, wherein in the ON state the switching device is closed and in the OFF state it is open, wherein the state of the switching device is changed by means of a mechanical transit movement, wherein the transit movement is carried out in such a way that the current voltage drop is smaller than the ignition voltage of an arc at any time and thereby the switching energy in the controllable resistance element is dissipated in the form of electrical power loss, and wherein in the event of overcurrents below an overcurrent threshold value, the controllable resistance element is transferred to an intermediate state by the transit movement,so that electrical attenuation is introduced into the circuit without interrupting it. The adjustable resistance element comprises a movable element and a stationary element, the movable element being substantially cylindrical, the stationary element being substantially hollow-cylindrical, the movable element being designed to be immersible into the stationary element and movable relative to it, a first contact system being attached to the movable element and a second contact system being attached to the stationary element, each for establishing electrical contact between the movable element and the stationary element, and the linear transit movement changing the distance between the first contact system and the second contact system, thereby changing the distribution of the current path between the movable element and the stationary element.

[0012] The advantage here is that such a switching device provides additional intermediate switching states in addition to the two switching states ON and OFF, namely switching states in which the circuit is damped in a defined manner. This offers decisive advantages in the following applications: Applications where the circuit cannot be disconnected for reasons of high availability, but adequate protection against overcurrent must still be guaranteed; applications where uninterrupted switching between two potentials is required. In contrast to a "hard" disconnection of circuits, this allows the flow of compensating currents. The operating principle is similar to that of high-speed resistance switches. Applications with rapidly changing loads, such as electrolysis furnaces in steel smelting plants or electrogalvanic processes, where the equipment is therefore very difficult to protect.

[0013] In one embodiment, when the overcurrent drops, the intermediate state is left and the ON state is entered.

[0014] In a further embodiment, the opening of the circuit (OFF state) is forced in the event of overcurrents above the overcurrent threshold.

[0015] In a further embodiment, the transit movement is stopped by a regulation.

[0016] In one embodiment, coils are provided on the adjustable resistance element for electro-mechanical drive against a spring.

[0017] In a further embodiment, a first coil is arranged at the bottom of the hollow cylindrical fixed element and a second, corresponding coil is arranged at the first end of the cylindrical movable element, wherein the two coils repel each other when energized, wherein at the opposite, second end of the cylindrical movable element a spring presses the movable element in the direction of the first coil and thus in the direction of the ON state.

[0018] In one embodiment, the switching device further comprises a sensor for measuring the temperature of the adjustable resistance element or the main current path.

[0019] In a further embodiment, the switching device is provided for switching an alternating or direct current.

[0020] The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of the embodiments, which are explained in more detail in connection with the figures.

[0021] Showing: Figure 1 : Electrical switch with adjustable resistance element; Figures 2A and 2B : Electrical resistance of the electrical switch according to the invention; Figures 3A, 3B, 3C : Electrical switch with adjustable resistance element in the ON state, intermediate state and OFF state; Figures 4A, 4B, 4C , 4D, 4E, 4F , 4G, 4H, 4I, 4J : Transit movement of the electrical switch according to the invention between ON state and OFF state; Figure 5A, 5B, 5C , 5D, 5E, 5F : Switching device with adjustable resistance element and coils and spring; Figure 6A and 6B : Damping of a circuit with a switching device according to the invention and switching states of the switching device; and Figure 7A and 7B: Another embodiment of an adjustable resistance element.

[0022] In Figure 1 An electrical switch 100 is shown. The electrical switch 100 comprises an ON state and an OFF state for opening, closing, or commutating an electrical circuit. For this purpose, a first contact 110 and a second contact 120 are provided, between which the electrical circuit is switched. The electrical switch 100 further comprises an adjustable resistance element 200, which is electrically arranged between the first contact 110 and the second contact 120. In the ON state, the electrical switch 100 is closed and in the OFF state it is open. The switching process, the transition from the ON state to the OFF state and vice versa, occurs by means of a mechanical transit movement T of the adjustable resistance element 200.

[0023] To open or commutate the circuit, the resistance of the adjustable resistance element 200 is increased by means of the transit movement T and the transit movement T is carried out in such a way that the current voltage drop at any time is smaller than the ignition voltage of an arc and that the switching energy in the adjustable resistance element 200 is dissipated in the form of electrical power loss.

[0024] The adjustable resistance element 200 comprises a movable element 210 and a stationary element 220, wherein the movable element 210 is substantially cylindrical and the stationary element is substantially hollow-cylindrical. The movable element 210 can be inserted into the stationary element 220 and moved against it. Furthermore, the adjustable resistance element 200 comprises a first contact system 310 on the stationary element 220 and a second contact system 320 on the movable element 210, each for establishing electrical contact between the movable element 210 and the stationary element 220.

[0025] By means of a linear transit movement T, the distance between the first contact system 310 and the second contact system 320 is changed, whereby the division of the current path between the movable element 210 and the fixed element 220 changes.

[0026] The fixed element 220 may comprise a galvanic isolation 230, so that in the OFF state the first contact 110 is galvanically separated from the second contact 120. Likewise, the galvanic isolation may be achieved via the doping of the adjustable resistance element 200 itself.

[0027] In Figure 2A The chain of electrical resistors of the electrical switch 100 is shown. It is a series circuit of electrical resistors, starting with the electrical resistor at the second contact 120 R_Cu2, through the resistance of the adjustable resistance element 200 R_SiC and the electrical resistance of the galvanic insulation 230 R_Iso, to the first contact 110 with the resistor R_Cu1.

[0028] In Figure 2B The electrical resistance of the adjustable resistance element 200 is shown plotted against the deflection of the mechanical transit movement T. In the representation of the Figure 2BIn small positions, the first contact 110 is galvanically isolated from the second contact 120 at an electrical resistance greater than 1MΩ (mega ohm). In this left position—at an electrical resistance greater than 1MΩ (mega ohm)—the electrical switch 100 is in the OFF state.

[0029] If the movable element 210 now moves by means of the mechanical transit movement T according to the representation of the Figure 1 to the right, the resistance decreases after crossing the insulation zone 230, until the electrical resistance of the adjustable resistance element is less than 100µΩ (micro Ohm). In this position, the electrical switch is in the ON state.

[0030] In the Figures 3A, 3B and 3CThe transition of the electrical switch 100 from the ON state to the OFF state is shown. By means of a linear transit movement T of the movable element 210, the resistance of the adjustable resistance element 200 is increased. The transit movement T is carried out in such a way that the current voltage drop at any time is smaller than the ignition voltage of an arc, thus dissipating the switching energy in the adjustable resistance element 200 in the form of electrical power loss.

[0031] In Figure 3AThe electrical switch 100 is in the ON state. The electrical current flows from the first contact 110 via the first contact system 310 to the movable element 210 and further via the second contact system 320 to the second contact 120. If the movable element 210 is made of copper, for example, the total resistance of the electrical switch in the ON position is in the range of less than 100 µΩ (micro ohms). The first contact system 310 and the second contact system 320 are formed by contact springs, for example, canted coil springs from Bal Seal Engineering.

[0032] To trigger the electrical switch 100, i.e. to transfer the electrical switch 100 from the ON state to the OFF state, the movable element 210 is now moved as shown in the Figures 3A, 3B and 3C moved to the left.

[0033] In an intermediate position, which Figure 3BAs shown, the current flows again from the first contact 110 via the first contact system 310, the movable element 210 to the second contact system 320 and in the adjustable resistance element 200 to the second contact 120. Due to the linear transit movement T, the distance between the first contact system 310 and the second contact system 320 was changed, namely reduced, whereby the division of the current path between the movable element 210 and the fixed element 220 changes.

[0034] In Figure 3C The electrical switch 100 is shown in the OFF state. By the transit movement T, the movable element 210 was further moved according to the representation of the Figures 3A, 3B and 3Cmoved to the left. The second contact system 320 has been moved beyond the galvanic isolation 230, so that the first contact system 310 and the second contact system 320 are both in the zone of the first contact 110. Thus, current flow only occurs due to a leakage current of the galvanic isolation, since the resistance of the adjustable resistance element 200 is greater than 1 MΩ (mega ohm).

[0035] In the Figures 4A to 4JAn electrical switch 100 is shown. The adjustable resistance element 200 has a first zone 221, which is made of copper, for example, and has a high conductivity. In the ON state of the electrical switch, the fixed element 220 dips into this first zone 221, so that, due to the lowest resistance, the current flows via the end face of the movable element 210 and the low-conductivity zone 221 of the adjustable resistance element 200. Likewise, the movable element 210 has a termination 211, which can also be made of copper and thus has a low conductivity. The current therefore flows from the first contact 110 via the termination 211 and the movable element 210.

[0036] If the transit movement T is now executed, according to the representation of the Figures 4A to 4Jthe movement of the movable element 210 to the left, there is a spatial separation of the termination 211 and also of the movable element 210 from the zone 221, so that the current flows via the first contact system 310 and the second contact system 320.

[0037] If the movable element 210 is now moved further to the left, the first contact system 310 and the second contact system 320 are moved toward each other and the current flows through the adjustable resistance element 200 itself. As the movement continues, the distribution of the current path between the movable element 210 and the fixed element 220 changes.

[0038] In Figure 4Hthe second contact system 320 reaches the zone of galvanic isolation 230. When the second contact system 320 is completely in the zone of galvanic isolation 230, the switch is open and a current flow is no longer possible. In the end position of the movable element 210 in the illustration of the Figure 4J the first contact system 310 and the second contact system 320 are located in the zone of the first contact 110.

[0039] The electrical switch 100 may have at least a third contact, wherein it commutates a potential between these at least three contacts.

[0040] The adjustable resistance element 200, in particular its fixed element 220, can be made of a conventional material or of a dopable semiconductor material. Silicon carbide (SiC), for example, is advantageous as a dopable semiconductor material because it meets important criteria and enables a compact design of the adjustable resistance element 200. As a semiconductor material, silicon carbide has a very high breakdown field strength and a low specific forward resistance. Furthermore, silicon carbide is dopable and thus its electrical properties can be adjusted from 0.1 to 109 Ω cm (ohm-centimeters). Furthermore, silicon carbide is highly temperature-resistant, with oxidation resistance up to 1600°C and a decomposition temperature above 2700°C. Silicon carbide is also a very good thermal conductor.

[0041] The resistance of the adjustable resistance element 200 can be increased by changing the active length, shape, arrangement, or doping. The current path within the adjustable resistance element 200, or rather the distribution of the current path between the movable element 210 and the stationary element 220, is changed by the transit movement T.

[0042] Figures 5A to 5D show the switching device 1000 according to the invention in its various intermediate states. The switching device 1000 can assume not only an ON state and an OFF state for opening, closing, or commutating an electrical circuit between a first contact 110 and a second contact 120, but also other intermediate states, wherein the switching device and thus the electrical circuit are closed in the ON state and open in the OFF state.

[0043] For this purpose, the switching device 1000 has a controllable resistance element 200, which is electrically arranged between the first contact 110 and the second contact 120. The state of the switching device 1000 is changed by means of a mechanical transit movement T.

[0044] The transit movement T is carried out in such a way that the current voltage drop at any time is smaller than the ignition voltage of an arc and thus the switching energy in the adjustable resistance element 200 is dissipated in the form of electrical power loss.

[0045] In the case of overcurrents below an overcurrent threshold, the transit movement T causes the adjustable resistance element 200 to be transferred into an intermediate state, so that electrical damping is introduced into the circuit without interrupting it.

[0046] In the Figure 5AThe switching device 1000 is initially in the ON state. The adjustable resistance element 200 comprises a movable element 210 and a fixed element 220, wherein the movable element 210 is substantially cylindrical and the fixed element 220 is substantially hollow cylindrical. The movable element 210 is designed to be immersible into the fixed element 220 and can be moved against it.

[0047] Furthermore, the adjustable resistance element 200 is provided with a first contact system 310 on the movable element 210 and a second contact system 320 on the fixed element 220. These contact systems 310; 320 are provided for electrical contact between the movable element 210 and the fixed element 220.

[0048] The linear transit movement T changes the distance between the first contact system 310 and the second contact system 320, which changes the distribution of the current path between the movable element 210 and the fixed element 220. This in the sequence of Figures 5A to 5F As the movable element 210 moves to the left, the second contact system 320 is moved toward the first contact system 310, and the current path changes such that an increasingly larger portion flows through the fixed element 220 of the adjustable resistance element 200.

[0049] If the overcurrent drops, the set intermediate state can be exited and the switching device 1000 can return to the ON state. In such a case, the electrical switching device 1000 would not be triggered, but would only be temporarily transferred to an intermediate state.

[0050] If, after the controllable resistance element 200 has been transferred to an intermediate state due to the occurrence of an overcurrent below an overcurrent threshold, the overcurrent continues to rise and exceeds the overcurrent threshold, the switching device 1000 can force the circuit to open, i.e., transfer it to the OFF state.

[0051] The transit movement T can be achieved by means of an electromechanical drive. Figures 5A to 5F For this purpose, a first coil 520 is provided at the bottom of the hollow-cylindrical stationary element 220, and a second, corresponding coil 510 is provided at the first end of the cylindrical movable element 210. These coils repel each other when energized. Furthermore, a spring 600 is arranged at the second end of the cylindrical movable element 210, which urges the movable element 210 toward the first coil 520 and thus toward the ON state.

[0052] The current supply to the first and second coils 520; 510 can be carried out by means of a control, which thus controls the transit movement T and sets the desired intermediate state or the ON state or OFF state of the controllable resistance element 200.

[0053] A sensor for measuring the temperature of the adjustable resistance element 200 or the temperature of the main current path may be provided on the switching device 1000. The control can adjust the adjustable resistance element 200 according to the measured temperature and, if necessary, transfer the switching device 1000 to the OFF state so that no current flow is possible.

[0054] The switching device 1000 according to the invention is intended for switching an alternating current or a direct current.

[0055] In Figure 6AThe switching device 1000 according to the invention is shown with four different intermediate states with resistors R1, R2, R3, and R4. For example, resistor R4 is much larger than resistor R3, which is much larger than resistor R2, and which is larger than resistor R1. When set to one of the four intermediate states, the adjustable resistance element 200 will attenuate the circuit using the set resistance.

[0056] Figure 6B clearly explains the sequence of electrical resistances of the adjustable resistance element 200: Starting from the ON state with low resistance, discrete electrical resistances R1, R2, R3, R4, ..., RN can be set. Above the maximum resistance RN lies the electrical resistance of the OFF state. According to the Figures 5A to 5Fand the formation of the adjustable resistance element 200, in this embodiment the resistance values ​​are continuously formed and can be continuously controlled.

[0057] The detection of the overcurrent and the deflection of the adjustable resistance element 200 can also be achieved by a corresponding arrangement of the main contacts without additional coil bodies, or by additional measuring devices. This fulfills the function of a thermal release.

[0058] In addition to the defined deflection due to a specific current, for smaller currents, the temperature can also be measured at specific points in the adjustable resistance element 200 or on the main current path. If the temperature exceeds a certain threshold, the movable contact system changes its position via a corresponding deflection mechanism, such as a bimetal, and the resistance is further increased. This reduces the current.

[0059] Such a system can either represent a function of the switching device 1000, which thereby protects the equipment connected in the circuit, or it can be a type of self-protection of the device to ensure an overload of the adjustable resistance element 200 or parts of the current path.

[0060] In the Figures 7A and 7BA further embodiment of a controllable resistance element 200 is shown. In this embodiment, uniform resistance elements 701 with a first connection surface 702 and a second connection surface 703 are connected in series. Insulating elements 705 are arranged between the resistance elements 701, so that the series connection is achieved via the electrical contacting of adjacent connection surfaces 702, 703. Resistance elements 701 are designed as broken hollow discs with a first connection surface 702 and a second connection surface 703.

[0061] The movable element 210 with the second contact system 320 runs inside the resistance elements 701. The opening and closing takes place analogously to the first or second embodiment by means of a transit movement T, wherein the transit movement T is carried out in such a way that the current voltage drop at any time is smaller than the ignition voltage of an arc and thus the switching energy in the controllable resistance element 200 is dissipated in the form of electrical power loss.

Claims

1. Switching device (1000) with an ON state, an OFF state for opening, closing or commutating a circuit between a first contact (110) and a second contact (120) and further intermediate states between the ON state and the OFF state, and with a variable resistor element (200), which is electrically arranged between the first contact (110) and the second contact (120), wherein the switching device (1000) is closed in the ON state and open in the OFF state, wherein the state of the switching device (1000) is changed by means of a mechanical transit movement (T), characterized in that the transit movement (T) is performed in such a way that the prevailing voltage drop at any point in time is less than the ignition voltage of an electric arc, and the switching energy in the variable resistor element (200) is consequently dissipated in the form of electrical power loss, and in that, in the event of overcurrents below an overcurrent threshold value, the variable resistor element (200) is transferred to an intermediate state by the transit movement (T), so that electrical damping is introduced into the circuit without interrupting it, wherein the variable resistor element (200) comprises a movable element (210) and a fixed element (220), wherein the movable element (210) is substantially cylindrical, wherein the fixed element (220) is substantially hollow-cylindrical, wherein the movable element (210) is designed such that it is able to be plunged into the fixed element (220) and can be moved against the latter, wherein a first contact system (310) is attached to the movable element (210) and a second contact system (320) is attached to the fixed element (220), in each case for establishing electrical contact between the movable element (210) and the fixed element (220), wherein the linear transit movement (T) changes the distance between the first contact system (310) and the second contact system (320), as a result of which the division of the current path between the movable element (210) and the fixed element (220) changes.

2. Switching device (1000) according to Claim 1, in which the intermediate state is left and the ON state is assumed when the overcurrent drops.

3. Switching device (1000) according to Claim 1 or 2, in which the circuit is forced to open (OFF state) in the event of overcurrents above the overcurrent threshold value.

4. Switching device (1000) according to any of the preceding claims, in which the transit movement (T) is adjusted by a controller.

5. Switching device (1000) according to Claim 4, in which coils (510; 520) are provided on the variable resistor element (200) for electromechanical driving against a spring (600).

6. Switching device (1000) according to Claim 1, in which a first coil (520) is arranged at the bottom of the hollow-cylindrical fixed element (220) and a second, corresponding coil (510) is arranged at the first end of the cylindrical movable element (210), wherein, when current is applied, the two coils (510; 520) repel each other, wherein, at the opposite, second end of the cylindrical movable element (210), a spring (600) pushes the movable element (210) in the direction of the first coil (520) and thus in the direction of the ON state.

7. Switching device (1000) according to any of the preceding claims, in which the switching device (1000) further comprises a sensor for measuring the temperature of the variable resistor element (200) or the main current path.

8. Switching device (1000) according to any of the preceding claims, wherein the switching device (1000) is provided for switching an alternating current or a direct current.