Switching of direct currents
The hybrid switching arrangement with a controlled semiconductor unit addresses the challenge of switching direct currents by preventing arcs and ensuring safe, reliable switching through a timed sequence of switch operations.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SIEMENS AG
- Filing Date
- 2025-10-14
- Publication Date
- 2026-05-15
AI Technical Summary
Switching off direct currents is complicated by the absence of a natural zero crossing, leading to arc formation during contact opening in existing technologies.
A hybrid switching arrangement using an electromechanical first switch and a parallel circuit with an electromechanical second switch and a semiconductor switching unit, where the semiconductor unit is controlled to switch after the first switch closes and before the second switch opens, preventing contact bounce and arc formation.
The solution ensures safe and reliable switching by preventing arcs during contact closure and using the same element for both closing and opening the current path, meeting industry standards for precise switching.
Smart Images
Figure EP2025079531_15052026_PF_FP_ABST
Abstract
Description
[0001] 2024P13178 DE
[0002] 1
[0003] Description
[0004] Switching of direct currents
[0005] The invention relates to a hybrid switching arrangement and a method for switching direct currents.
[0006] Direct current (DC) networks are becoming increasingly important in low-voltage applications. They are now used not only for powering railways, as before, but also for photovoltaic systems, battery storage, fast-charging stations for electric vehicles, and in industrial applications. Numerous research projects, such as "DC Industrie," demonstrate the advantages of DC networks. These networks require devices for switching direct currents. Switching off direct currents is complicated by the fact that, unlike alternating current (AC), direct current does not have a natural zero crossing, which, for example, extinguishes arcs that occur when switching contacts open.
[0007] The invention is based on the objective of providing an improved switching arrangement and an improved method for switching direct currents.
[0008] The problem is solved according to the invention by a switching arrangement with the features of claim 1 and a method with the features of claim 15.
[0009] Advantageous embodiments of the invention are the subject of the dependent claims.
[0010] A hybrid switching arrangement according to the invention for switching direct currents comprises
[0011] - an electromechanical first switch,
[0012] - a parallel circuit connected in series with the first switch, comprising an electromechanical second switch which closes automatically with a time delay after the first switch closes and opens automatically before the first switch opens, and a semiconductor switching unit which has a forward state in which it conducts for direct currents of at least one direction and a reverse state in which it blocks direct currents of both directions,
[0013] - a detector unit configured to detect a closing time when the first switch is closed and the second switch is open, 2024P13178 DE
[0014] 2 and
[0015] - a control unit configured to put the semiconductor switching unit into the on state when the switches are closed after the closing time while the second switch is still open, and to put it into the on state before the second switch is opened when the switches are opened, and into the off state after the second switch is opened while the first switch is still closed.
[0016] The switching arrangement according to the invention makes it possible, in particular, to switch the semiconductor switching unit into the conducting state only after the first switch has closed, while the second switch is still open. For this purpose, the switching arrangement includes a detector unit configured to detect the closing time at which the first switch is closed and the second switch is still open. By switching the semiconductor switching unit into the conducting state only after the first switch has closed, contact bounce of the first switch during its closing is prevented, since it is not the first switch, but the semiconductor switching unit that closes the current path in which the switching arrangement is located. In particular, the first switch does not draw any arcs during closing that could occur during contact bounce.Furthermore, the current path is closed and opened by the same element, namely the semiconductor switching unit, since when the switches are opened, the current path is only interrupted by the semiconductor switching unit being switched off. Thus, the switching arrangement meets standards that require precisely this: the closing and opening of the current path by the same element.
[0017] In one embodiment of the switching arrangement according to the invention, the semiconductor switching unit has at least one self-blocking semiconductor switch.
[0018] In a further embodiment of the switching arrangement according to the invention, the semiconductor switching unit is conductive in the forward state for direct currents of both directions. In this case, the semiconductor switching unit has, for example, two anti-series connected, self-blocking semiconductor switches. The anti-series connection of self-blocking semiconductor switches enables the blocking of direct currents of both directions.
[0019] For example, every semiconductor switch is an IGBT (abbreviation for Insulated-Gate Bipolar Transistor) with an antiparallel diode, a bipolar transistor, or a field-effect transistor, such as a 2024P13178 DE.
[0020] 3
[0021] MOSFET (abbreviation for Metal-Oxide-Semiconductor Field-Effect Transistor).
[0022] In a further embodiment of the switching arrangement according to the invention, the detector unit is configured to detect the closing time by potential-free detection of a voltage drop across the second switch. This embodiment of the switching arrangement utilizes the fact that the voltage drop across the second switch increases after the first switch is closed, and thus the closing time can be detected by this voltage rise. Potential-free detection of the voltage rise is understood to mean galvanically isolated detection. If no voltage drop occurs across the second switch when the first switch is closed and the second switch is still open, either the system voltage is too low or the load impedance is too high. In both cases, however, no significant load current flows, so this situation is not critical.If the voltage across the second switch is so low that the detector unit does not detect this voltage, it also results in a negligible load current.
[0023] In a further embodiment of the switching arrangement according to the invention, the detector unit comprises a current-limiting element and an optocoupler connected in series in parallel with the second switch. In particular, the optocoupler can be bidirectional (dual-channel). Alternatively, the detector unit comprises a current-limiting element and two anti-series-connected optocouplers connected in series in parallel with the second switch. One optocoupler enables particularly simple and cost-effective potential-free detection of the voltage rise across the second switch. A bidirectional optocoupler and two anti-series-connected optocouplers each enable the monitoring of DC voltages with different polarities. The very simple voltage measurement with one optocoupler is sufficient in this case, since only the detection of the closing time is required, not a precise voltage measurement.
[0024] In a further embodiment of the switching arrangement according to the invention, the current limiting element is a series resistor. A series resistor is a particularly simple and cost-effective implementation of the current limiting element.
[0025] In a further embodiment of the switching arrangement according to the invention, the current limiting element is a constant current source consisting of a field-effect transistor and 2024P13178 DE
[0026] 4. A series-connected resistor. Compared to a series resistor, the semiconductor-based design of the current limiting element allows for an extension of the detector unit's operating range.
[0027] In a further embodiment of the switching arrangement according to the invention, the detector unit has a protective circuit above each optocoupler. Protective circuits can, for example, protect the LEDs of the optocouplers from reverse bias overvoltages.
[0028] In a further embodiment of the switching arrangement according to the invention, the detector unit is configured to output the measurement signals detected by each optocoupler to the control unit. This allows the control unit to determine the closing time based on the measurement signals from the detector unit.
[0029] In a further embodiment of the switching arrangement according to the invention, an ohmic resistor is connected in parallel to the semiconductor switching unit. A leakage current can be defined by an ohmic resistor, particularly one with a high resistance, connected in parallel to the semiconductor switching unit. This leakage current flows through the semiconductor switching unit before the switches are closed, ensuring that the second switch is de-energized. This is advantageous for defining the voltage rise across the second switch after the first switch closes and thus for unambiguously detecting the closing time.
[0030] The method according to the invention relates to switching direct currents with an electromechanical first switch and a parallel circuit of an electromechanical second switch and a semiconductor switching unit connected in series with the first switch. The second switch closes automatically with a time delay after the first switch closes and opens automatically with a time delay before the first switch opens. The semiconductor switching unit has a forward state, in which it conducts for direct currents in at least one direction, and a reverse state, in which it blocks direct currents in both directions. When the switches close, a closing point is detected at which the first switch is closed and the second switch is open. After this closing point, the semiconductor switching unit is switched to the forward state while the second switch is still open.When the switches are opened, the semiconductor switching unit is switched to the on state before the second switch is opened, and to the off state after the second switch is opened while the first switch is still closed. 2024P13178 DE.
[0031] 5
[0032] The features of the method according to the invention correspond to the features of a switching arrangement according to the invention. Therefore, the advantages of the method according to the invention also correspond to the aforementioned advantages of a switching arrangement according to the invention.
[0033] The properties, features, and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more readily understandable in connection with the following description of exemplary embodiments, which are explained in more detail in conjunction with the drawings. These drawings show:
[0034] FIG 1 two electromechanical switches of an embodiment of a switching arrangement according to the invention,
[0035] FIG 2 shows a circuit diagram of an embodiment of a switching arrangement according to the invention for switching direct currents with switches shown in Figure 1,
[0036] FIG 3 shows a flowchart of an embodiment of the method according to the invention when closing the switches of the switching arrangement shown in Figure 2,
[0037] FIG 4 Time course of voltages and a current when closing the switches of the switching arrangement shown in Figure 2,
[0038] FIG 5 shows a flowchart of an embodiment of the method according to the invention when opening the switches of the switching arrangement shown in Figure 2.
[0039] Corresponding parts are marked with the same reference symbols in the figures.
[0040] Figure 1 (FIG 1) shows a first electromechanical switch S1 and a second electromechanical switch S2 of an embodiment of a switching arrangement 1 according to the invention (see Figure 2). Each switch S1, S2 is a switch of a conventional electromechanical contactor 2 with an electromagnet (not shown). To close the contactor 2, the electromagnet is energized with a control current. The electromagnet then generates a magnetic field through which an armature of the contactor 2 is moved. The armature is connected to switching contacts 3, 5 of switches S1, S2, which are moved by the movement of the armature to a fixed mating contact 7, 9. 2024P13178 DE
[0041] 6, which closes switches S1 and S2. To open contactor 2, the control current of the electromagnet is switched off, and a restoring force from a (also not shown) spring in the contactor moves the armature and thus also the switching contacts 3 and 5 back to their initial positions.
[0042] The switching contacts 3 of the first switch S1 are separated from their respective mating contacts 7 by a distance a, which is smaller by a distance difference H than the distance b of the switching contacts 5 of the second switch S2 from their respective mating contacts 9. Therefore, when switches S1 and S2 close, the second switch S2 automatically closes later than the first switch S1. When switches S1 and S2 open, the second switch S2 automatically opens earlier than the first switch S1. Thus, the two switches S1 and S2 close and open with a time offset from each other.
[0043] Figure 2 (FIG 2) shows a circuit diagram of an embodiment of a hybrid switching arrangement 1 according to the invention for switching direct currents. The switching arrangement 1 comprises the switches S1, S2, a semiconductor switching unit 11, a detector unit 13, a current measuring unit 14 and a control unit 15 shown in Figure 1.
[0044] The semiconductor switching unit 11 is connected in parallel to the second switch S2. The parallel connection of the second switch S2 and the semiconductor switching unit 11 is connected in series with the first switch S1.
[0045] The semiconductor switching unit 11 comprises two anti-series connected, self-blocking semiconductor switches 17. In the embodiment shown in Figure 2, each semiconductor switch 17 is an IGBT with an anti-parallel diode. In other embodiments, the semiconductor switching unit 11 can comprise other semiconductor switches 17, for example, MOSFETs. The semiconductor switching unit 11 has a forward state, in which it conducts for direct currents in both directions, and a reverse state, in which it blocks direct currents in both directions. In the forward state, the two semiconductor switches 17 are switched on; in the reverse state, the two semiconductor switches 17 are switched off.
[0046] The detector unit 13 is configured to detect a closing time t1 (see Figure 4) at which, when switches S1 and S2 are closed, the first switch S1 is closed and the second switch S2 is still open. In the embodiment shown in Figure 2, the detector unit 13 has a current limiting element 19 and a 2024P13178 DE for this purpose.
[0047] 7
[0048] Optocoupler 21 is connected to a light-emitting diode (LED) 23 and a photosensor 25. The current-limiting element 19 is designed as a series resistor and is connected in series with the LED 23 of the optocoupler 21. The series connection of the current-limiting element 19 and the LED 23 is connected in parallel with the second switch S2. The optocoupler 21 outputs the measurement signals from the photosensor 25 to the control unit 15.
[0049] The current measuring unit 14 is designed to detect a current flowing through the semiconductor switching unit 11 and to transmit the measurement signals detected by it to the control unit 15.
[0050] The control unit 15 is set up to control the semiconductor switches 17 of the semiconductor switching unit 11 depending on the measurement signals of the optocoupler 21 and the current measuring unit 14.
[0051] Figures 3 to 5 show an embodiment of the method according to the invention with method steps 31 to 36 for switching direct currents by means of a switching arrangement 1 described with reference to Figures 1 and 2.
[0052] Figure 3 (FIG 3) shows process steps 31, 32, 33 when closing switches S1, S2. Process steps 31, 32, 33 are also described below with reference to Figure 4.
[0053] Figure 4 (FIG 4) shows the waveforms of a voltage U1 across the first switch S1, a voltage U2 across the second switch S2 and a current I through the first switch S1 as a function of a time t when closing the switches S1 , S2.
[0054] Before switches S1 and S2 close, both switches S1 and S2 are open, the semiconductor switching unit 11 is in the off state, and the voltage U1 across the first switch S1 assumes a voltage value Uo. The voltage U2 across the second switch S2 is zero, because a leakage current flowing through the semiconductor switching unit 11 ensures that the second switch S2 is de-energized.
[0055] In a first process step 31, contactor 2 is switched on, meaning the control current for the electromagnet of contactor 2 is switched on. Subsequently, the first switch S1 closes at closing time t1, while the second switch S2 is still open. By closing the first switch S1, the voltage U1 drops to zero and the 2024P13178 DE
[0056] 8
[0057] Voltage U2 rises to the voltage value Uo. The current I remains zero as long as the second switch S2 is still open and the semiconductor switching unit 11 is in the off state.
[0058] In a second process step 32, the closing time t1 is detected. As the voltage U2 rises from zero to Uo, the voltage across the LED 23 also increases. This voltage increase is detected by the optocoupler 21 without any potential difference. The measurement signals acquired by the optocoupler 21 are output to the control unit 15, which uses these signals to determine the closing time t1.
[0059] In a third process step 33, the semiconductor switching unit 11 is switched to the on-state by the control unit 15 at time t2. This causes the voltage U2 to drop back to zero, and a current I begins to flow through the first switch S1 and the semiconductor switching unit 11. At time t3, the second switch S2 closes automatically and takes over the conduction of the current I from the semiconductor switching unit 11; that is, the current I now flows through the first switch S1 and the second switch S2 and reaches a final current value Ion-
[0060] Figure 5 (FIG 5) shows process steps 34, 35, 36 during the opening of switches S1, S2. Before opening switches S1, S2, both switches S1, S2 are closed.
[0061] Semiconductor switching unit 11 is in the blocking state and a current flows through the first switch S1 and the second switch S2.
[0062] In a fourth process step 34, contactor 2 is switched off by disconnecting the control current of the electromagnet. Simultaneously, the semiconductor switches 17 of the semiconductor switching unit 11 are activated by the control unit 15 to set the semiconductor switching unit 11 to the on-state. Since the semiconductor switches 17 switch faster than the second switch S2, the semiconductor switching unit 11 is thereby set to the on-state before the second switch S2 opens.
[0063] In a fifth process step 35, the opening of the second switch S2 is detected. Since the first switch S1 is still closed after the second switch S2 opens, and the semiconductor switching unit 11 is in the on-state, a current flows through the first switch S1 and the semiconductor switching unit 11 after the second switch S2 opens. This current, and thus the opening of the second switch S2, is detected by the current measuring unit 14. The measurement signal from the current measuring unit 14 is transmitted to the control unit 15. 2024P13178 DE
[0064] 9
[0065] In a sixth process step 36, after the second switch S2 is opened, the semiconductor switching unit 11 is switched to the off state by the control unit 15, thereby interrupting the current. Subsequently, the first switch S1 opens automatically. Although the invention has been further illustrated and described in detail by preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived from them by a person skilled in the art without departing from the scope of protection of the invention.
[0066] 2024P13178 DE
[0067] Reference symbol list
[0068] 1 Switching arrangement 2 Contactor
[0069] 3, 5 Switching contact 7, 9 Counter contact
[0070] 11 Semiconductor switching unit 13 Detector unit
[0071] 14 Current measuring unit 15 Control unit
[0072] 17 Semiconductor switches 19 Current limiting element
[0073] 21 Optocoupler 23 Light-emitting diode
[0074] 25 Photosensor 31 to 36 Process step a, b Distance H Distance difference I Current Ion Final current value
[0075] S1 first switch
[0076] S2 second switch t time t1 closing time t2, t3 time Uo voltage value U1, U2 voltage
Claims
2024P13178 DE 11 Patent claims 1. Hybrid switching arrangement (1) for switching direct currents, the switching arrangement (1) comprising - an electromechanical first switch (S1), - a parallel circuit connected in series with the first switch (S1) of an electromechanical second switch (S2), which automatically closes with a time delay after the first switch (S1) closes when the switches (S1, S2) close and automatically opens before the first switch (S1) opens when the switches (S1, S2) open, and a semiconductor switching unit (11) which has a forward state in which it is conductive for direct currents of at least one current direction and a reverse state in which it is blocking for direct currents of both current directions, - a detector unit (13) configured to detect a closing time (t1) when the switches (S1, S2) are closed, at which the first switch (S1) is closed and the second switch (S2) is open, and - a control unit (15) configured to put the semiconductor switching unit (11) into the on-state when the switches (S1, S2) are closed after the closing time (t1) while the second switch (S2) is still open, and to put it into the on-state before the second switch (S2) is opened when the switches (S1, S2) are opened and after the second switch (S2) is opened to put switch (S2) into the locked state while the first switch (S1) is still closed.
2. Switching arrangement (1) according to claim 1, wherein the semiconductor switching unit (11) has at least one self-blocking semiconductor switch (17).
3. Switching arrangement (1) according to claim 1 or 2, wherein the semiconductor switching unit (11) is conductive in the forward state for direct currents of both current directions.
4. Switching arrangement (1) according to claim 3, wherein the semiconductor switching unit (11) comprises two anti-series connected, self-blocking semiconductor switches (17).
5. Switching arrangement (1) according to one of claims 2 to 4, wherein each semiconductor switch (17) is an IGBT with an antiparallel connected diode, a bipolar transistor or a field-effect transistor, for example a MOSFET.
6. Switching arrangement (1) according to one of the preceding claims, wherein the The detector unit (13) is set up to determine the closing time (t1) by means of a potential-free 2024P13178 DE 12 To detect an increase in a voltage drop (U2) across the second switch (S2).
7. Switching arrangement (1) according to one of the preceding claims, wherein the detector unit (13) comprises a series connection of a current limiting element (19) and an optocoupler (21) connected in parallel to the second switch (S2).
8. Switching arrangement (1) according to claim 7, wherein the optocoupler (21) is bidirectional.
9. Switching arrangement (1) according to one of claims 1 to 6, wherein the detector unit (13) comprises a series connection of a current limiting element (19) and two anti-series connected optocouplers (21) connected in parallel to the second switch (S2).
10. Switching arrangement (1) according to one of claims 7 to 9, wherein the current limiting element (19) is a series resistor.
11. Circuit arrangement (1) according to one of claims 7 to 9, wherein the current limiting element (19) is a constant current source consisting of a field-effect transistor and a resistor connected in series.
12. Switching arrangement (1) according to one of claims 7 to 11, wherein the detector unit (13) has a protective circuit above each optocoupler (21).
13. Switching arrangement (1) according to one of claims 7 to 12, wherein the detector unit (13) is configured to output the measurement signals detected by each optocoupler (21) to the control unit (15).
14. Switching arrangement (1) according to one of the preceding claims, wherein an ohmic resistor is connected in parallel to the semiconductor switching unit (11).
15. Method for switching direct currents with an electromechanical first Switch (S1) and a parallel circuit of an electromechanical second switch (S2) connected in series with the first switch (S1), which automatically closes after a time delay when the switches (S1, S2) close and automatically closes before the first switch (S1) opens when the switches (S1, S2) open. 2024P13178 DE 13 opens, and a semiconductor switching unit (11) which has a forward state in which it is conductive for direct currents of at least one current direction and a reverse state in which it is blocking for direct currents of both current directions, wherein - when the switches (S1, S2) are closed, a closing time (t1) is detected at which the first switch (S1) is closed and the second switch (S2) is open, and after the closing time (t1) the semiconductor switching unit (11) is switched to the on state while the second switch (S2) is still open, and - when the switches (S1, S2) are opened, the semiconductor switching unit (11) is put into the on state before the second switch (S2) is opened and into the off state after the second switch (S2) is opened while the first switch (S1) is still closed.