Circuit breaker

Description

[0001] The invention relates to a low-voltage protective switching device according to the preamble of patent claim 1.

[0002] A corresponding protective switching device is known from WO 2015 / 028634 A1 by the applicant. A snubber, or attenuation element, is also connected to the semiconductor circuit arrangement, which serves to switch off a short circuit and which, according to WO 2015 / 028634 A1, comprises a rectifier bridge and two IGBTs. The snubber serves to protect the IGBTs and is composed of a resistor and a capacitor connected in series with the resistor, with the resistor being bridged by a diode.

[0003] Such a structure is also known from DE 10 2014 108 657 A1 of the applicant.

[0004] It has been shown that the snubber diode significantly increases the stress on the IGBT during short-circuit breakout. This is due to the fact that both are bipolar devices. The IGBT and the diode must therefore be selected and dimensioned to meet the high demands of a short circuit. This leads to an increase in the size of the respective components and, due to the longer paths, also to an increase in the loop inductance and the turn-off time.

[0005] WO 2013 / 071980 A1 describes a high-voltage DC circuit breaker with a hybrid design. It has a snubber consisting of only a resistor and a capacitor.

[0006] The object of the invention is therefore to provide a protective switching device of the type mentioned at the outset, with which the disadvantages mentioned can be avoided, which has a small size and which has a high level of reliability over a long period of time.

[0007] According to the invention, this is achieved by the features of patent claim 1.

[0008] This simplifies the design of the low-voltage protective device. This eliminates the need for a significant component. It has been shown that eliminating the diode can extend the service life of the IGBT, or allow the use of less resilient IGBTs. Due to the long time between two switching operations of a protective device, which is three minutes according to the standard, eliminating the diode has no negative effects on the low-voltage protective device or the semiconductor circuit arrangement. Eliminating the diode makes the low-voltage protective device more compact, more cost-effective, and more durable.

[0009] The subclaims relate to further advantageous embodiments of the invention.

[0010] Express reference is hereby made to the wording of the patent claims, whereby the claims are incorporated into the description at this point by reference and are deemed to be reproduced verbatim.

[0011] The invention will be described in more detail with reference to the accompanying drawings, in which only preferred embodiments are shown by way of example. In the drawings: Fig. 1 a circuit breaker according to the state of the art as a schematic representation; and Fig. 2 a part of a low-voltage protective switching device according to the preferred embodiment of the present invention.

[0012] The Fig. 2 shows a low-voltage protective switching device 1 with at least one outer conductor path 2 from an outer conductor supply connection 3 of the low-voltage protective switching device 1 to an outer conductor load connection 4 of the low-voltage protective switching device 1, and a neutral conductor path 5 from a neutral conductor connection 6 of the low-voltage protective switching device 1 to a neutral conductor load connection 7 of the low-voltage protective switching device 1, wherein a mechanical bypass switch 8 and a first mechanical disconnector 9 are arranged in series in the outer conductor path 2, wherein a second mechanical disconnector 10 is arranged in the neutral conductor path 5, wherein a semiconductor circuit arrangement 11 of the low-voltage protective switching device 1 is connected in parallel to the bypass switch 8, wherein a first current measuring arrangement 12, in particular comprising a shunt, is arranged in the outer conductor path 2,which is connected to an electronic control unit 13 of the protective switching device 1, wherein the electronic control unit 13 is designed to control the bypass switch 8, the first mechanical disconnector 9, the second mechanical disconnector 10 and the semiconductor circuit arrangement 11 upon detection of a predeterminable overcurrent, in particular a short-circuit current, by the current measuring arrangement 12, wherein a snubber 24 is arranged in circuitry parallel to the semiconductor circuit arrangement 11, wherein the snubber 24 has a capacitor 35 and a resistor 36 arranged in circuitry parallel to the capacitor 35.

[0013] This simplifies the design of the low-voltage protective switching device 1. This eliminates the need for a component that is considerably larger. It has been shown that omitting the diode can extend the service life of the IGBT 21, or that less resilient IGBT 21s can be used. Due to the long time between two switching operations of a protective switching device 1, which is three minutes according to the standard, omitting the diode does not have any negative effects on the low-voltage protective switching device 1 or the semiconductor circuit arrangement 11. By omitting the diode, the low-voltage protective switching device 1 becomes more compact, more cost-effective, and longer-lasting.

[0014] The present protective switching device 1, as well as the protective switching device according to WO 2015 / 028634 A1, are low-voltage protective switching devices. As is customary, the term "low voltage" refers to the range up to 1000V AC. The present low-voltage protective switching device 1 is, in particular, a pure AC voltage switching device.

[0015] Fig. 1 shows a protective switching device according to the prior art, as described, for example, in WO 2015 / 028634 A1. Like the protective switching device 1 in question, this device has an outer conductor path 2 and a neutral conductor path 5. The outer conductor path 2 runs through the protective switching device 1 from an outer conductor supply connection 3 to an outer conductor load connection 4. The neutral conductor path 5 runs through the protective switching device 1 from a neutral conductor connection 6 to a neutral conductor load connection 7. The respective connections 3, 4, 6, 7 are each preferably designed as screw connection terminals or plug-in connection terminals and are arranged in the protective switching device 1 so as to be accessible from the outside.

[0016] The protective switching device 1 preferably has an insulating housing.

[0017] A conventional mechanical bypass switch 8 with simple contact interruption is arranged in the outer conductor section 2. Preferably, and as shown, a first mechanical disconnect switch 9 is also arranged in the outer conductor section 2, in particular in series with the bypass switch 8. A second mechanical disconnect switch 10 is preferably arranged in the neutral conductor section 5. A semiconductor circuit arrangement 11 is connected in parallel with the bypass switch 8.

[0018] Furthermore, a surge arrester 19 is connected in parallel to the bypass switch 8.

[0019] The protective switching device 1 further comprises a current measuring arrangement 12, which is arranged in the outer conductor path 2 and is preferably designed to include a shunt or shunt resistor. The first current measuring arrangement 12 is preferably arranged in series with both the bypass switch 8 and the semiconductor circuit arrangement 11.

[0020] The current measuring arrangement 12 is connected to an electronic control unit 13 of the protective switching device 1, which is preferably designed to include a microcontroller or microprocessor. The electronic control unit 13 is designed to control the bypass switch 8 and the semiconductor circuit arrangement 11, as well as preferably the first mechanical disconnector 9 and the second mechanical disconnector 10, and thus to actuate or switch them in a predeterminable manner. For this purpose, the electronic control unit 13 is preferably connected by circuitry to the semiconductor circuit arrangement 11, as well as further to, in particular electromagnetic, actuating elements of the mechanical switches, thus the bypass switch 8, the first mechanical disconnector 9 and the second mechanical disconnector 10. The corresponding connections originating from the electronic control unit 13 are not shown in the Fig. 1 und 2 shown. During shutdown, after the IGBTs 21 are turned off, the voltage will rise due to the energy stored in the grid. The rising voltage is conducted by the surge arrester 19, which limits the current. When the current is low enough, the first and second mechanical disconnectors 9, 10 are opened.

[0021] The semiconductor circuit arrangement 11 preferably comprises a rectifier circuit 20, which is preferably designed as a full bridge, and, in the present embodiment, two power semiconductors 21, which are designed as IGBTs, as the actual switching or control elements. A larger power semiconductor 21 may also be provided.

[0022] In Fig. 1 In addition to the actual protective switching device 1, the electrical environment is also indicated. The supply network is represented by the AC mains voltage source 16, the internal network resistance 17, and the network inductance 18. Furthermore, an electrical load 23 and an electrical fault 22 in the form of a short circuit are shown.

[0023] In a switching device according to the state of the art, as in Fig. 1 As shown, it is provided that a shutdown process is carried out by the bypass switch 8 and the semiconductor circuit arrangement 11, and the first and second isolating switches 9, 10 only serve to ensure galvanic isolation of the load circuit after shutdown has taken place.

[0024] In a present low-voltage protective switching device 1, as shown as a preferred embodiment in Fig. 2 As shown, it is provided that the snubber 24 has a capacitor 35, to which a resistor 36 is arranged in parallel in terms of circuitry. All components or assemblies of the present low-voltage protective switching device 1, which are not considered alternative or different to the low-voltage protective switching device according to Fig. 1 correspond to the low-voltage protective switching device according to Fig. 1 .

[0025] The snubber 24 is designed without a diode. As already explained, it has been shown that, given the expected long times between two switching operations, the diode can be omitted without any negative effects. In fact, it has been shown that omitting the diode not only reduces the size and costs, but also reduces the stress on the IGBT 21. Thus, by omitting the diode, the electrical performance of the low-voltage protective switching device 1 was surprisingly increased.

[0026] Preferably, the resistor 36 is designed to be high-resistance, with the resistor 36 preferably being greater than 5 kΩ, in particular 10 kΩ. The capacitor 35 can be discharged by the high-resistance resistor 36.

[0027] When the low-voltage protective switching device 1 in question is switched on, the first mechanical disconnector 9 is closed first when the voltage crosses zero, followed immediately by the second mechanical disconnector 10. This prevents or at least minimizes an inrush current in the capacitor 35. At the next subsequent zero crossing of the voltage, the semiconductor circuit arrangement 11 is switched on, preventing a large inrush current from flowing through the IGBT 21. At the next subsequent zero crossing of the voltage, the bypass switch 8 is closed. The electronic control unit 13 is accordingly configured to actuate the relevant components in the specified order.

Claims

1. Low-voltage circuit breaker (1) having at least one phase conductor section (2) from a phase conductor supply terminal (3) of the low-voltage circuit breaker (1) to a phase conductor load terminal (4) of the low-voltage circuit breaker (1) and a neutral conductor section (5) from a neutral conductor terminal (6) of the low-voltage circuit breaker (1) to a neutral conductor load terminal (7) of the low-voltage circuit breaker (1), wherein a mechanical bypass switch (8) is arranged within the phase conductor section (2), wherein a semi-conductor circuit arrangement (11) of the low-voltage circuit breaker (1) is connected in parallel with the bypass switch (8), wherein a first current measuring arrangement (12), in particular comprising a shunt, is arranged within the phase conductor section (2), which is connected to an electronic control unit (13) of the circuit breaker (1), wherein the electronic control unit (13) is configured to actuate the bypass switch (8) and the semi-conductor circuit arrangement (11) upon detection of a predeterminable over-current, in particular a short-circuit current, by means of the current measuring arrangement (12), wherein a snubber (24) is arranged in parallel with the semi-conductor circuit arrangement (11) in terms of circuitry, wherein a first mechanical disconnect switch (9) is arranged within the phase conductor section (2), wherein a second mechanical disconnect switch (10) is arranged within the neutral conductor section (5), characterised in that the snubber (24) has a capacitor (35) and a resistor (36) arranged in parallel with the capacitor (35) in terms of circuitry, the snubber (24) is designed free of a diode and the electronic control unit (13) is configured to first close the first mechanical disconnect switch (9) and immediately thereafter the second mechanical disconnect switch (10) when the low-voltage circuit breaker (1) is switched on in the event of a voltage zero crossing.

2. Low-voltage circuit breaker (1) according to claim 1, characterised in that the resistor (36) is of a high-resistance design, wherein the resistor (36) has a resistance of preferably greater than 5 kΩ, in particular 10 kΩ.

3. Low-voltage circuit breaker (1) according to any one of claims 1 or 2, characterised in that the first mechanical disconnect switch (9) is arranged in series with the bypass switch (8).