CN111128602A

CN111128602A - Arrangement for interconnecting current switching devices

Info

Publication number: CN111128602A
Application number: CN201910982028.2A
Authority: CN
Inventors: D.库宗; J.勒布莱; P.德博克斯
Original assignee: Schneider Electric Industries SAS
Current assignee: Schneider Electric Industries SAS
Priority date: 2018-10-31
Filing date: 2019-10-16
Publication date: 2020-05-08
Also published as: FR3087957B1; EP3648134B1; FR3087957A1; EP3648134A1

Abstract

The invention relates to an interconnect device (6) and an electrical system, the interconnect device comprising: first and second terminals configured to be connected to first (C1) and second (C2) switching devices, respectively; third and fourth terminals configured to be connected to actuators of the first and second switching devices, respectively; an input terminal (10), an output terminal (12) and control terminals (14, 16); a first circuit connecting the input and output terminals to the first terminal and the second terminal; a second circuit connecting the control terminal to the third and fourth terminals for distributing the control signal, and comprising an electronic circuit (8), the electronic circuit (8) being configured to delay the transmission to the fourth terminal of the signal received from the control terminal for controlling the opening of the electrical contacts.

Description

Arrangement for interconnecting current switching devices

Technical Field

The invention relates to an arrangement for interconnecting current switching devices. The invention also relates to an electrical system comprising such an interconnect device.

Background

A switching device such as a contactor or a relay can selectively interrupt the flow of the direct current.

Such switching devices usually comprise electrical contacts or switches which can be switched between an open state and a closed state by means of an electromagnetic actuator integrated in the switching device. By controlling the actuator with a control signal, it is possible to switch between an open state and a closed state.

In practice, switching devices typically have maximum current and/or voltage ratings. If there are no other suitable switching devices on the market, it sometimes happens that the user has to use a switching device that is rated much higher than the intended use.

Disclosure of Invention

One aspect of the present invention relates to an interconnect device, comprising:

-a first terminal configured to be electrically connected to a first electrical contact of a first device for interrupting an electrical current;

-a second terminal configured to be electrically connected to a second electrical contact of a second device for interrupting the current;

-a third terminal configured to be electrically connected to a first actuator for actuating the first circuit breaker device;

-a fourth terminal configured to be electrically connected to a second actuator for actuating a second circuit breaker device;

-an input terminal, an output terminal and a control terminal;

-a first circuit connecting the input and output terminals to the first terminal and the second terminal to electrically connect the first and second contacts of the first and second circuit breaker devices between the input and output terminals;

-a second circuit connecting the control terminal to the third and fourth terminals to distribute the control signal applied between the control terminals to the third and fourth terminals, the second circuit further comprising an electronic circuit connected between the control terminal and the fourth terminal, the electronic circuit being configured to transmit the control signal for opening the electrical contact received from the control terminal to the fourth terminal with a predetermined time delay.

The interconnection device thus enables a modular combination of two or more circuit breaker devices to form an electrical system capable of interrupting a DC current having a magnitude and/or voltage respectively higher than the rating of each of said circuit breaker devices.

According to advantageous but not mandatory aspects, such interconnection means may incorporate one or more of the following features, alone or in any technically allowed combination:

the interconnect device is preassembled and comprises a support on which are mounted a first terminal, a second terminal, a third terminal and a fourth terminal, an input terminal, an output terminal and a control terminal, and in which the first and second circuits are integrated.

The support is made of a plastics material, preferably a moulded plastics material.

The first circuit is configured to electrically connect the first electrical contacts in parallel between the input and output terminals.

The first circuit is configured to electrically connect the second electrical contacts in series with each other and in parallel with the first electrical contacts between the input and output terminals.

The control signal for switching on comprises a transition of a voltage applied to the control terminal from a first amplitude value to a second amplitude value lower than the first amplitude value, the electronic circuit being configured to provide the delayed control signal to the fourth terminal, wherein the transition of the voltage to the second amplitude value is delayed by a time delay with respect to the control signal transmitted to the third terminal.

The time delay has a duration between 5ms and 50ms, including 5ms and 50 ms.

Another aspect of the invention relates to an electrical system comprising:

-a first device for interrupting the current, comprising a first electrical contact and a first actuator configured to switch the first electrical contact between an open state and a closed state according to a control signal;

-a second device for interrupting the current, comprising a second electrical contact and a second actuator configured to switch the second electrical contact between an open state and a closed state according to a control signal;

-an interconnect device as described above;

in the system, the interconnection device is connected to first and second circuit breaker devices, the first terminal being connected to the first contact, the second terminal being connected to the second contact, the third terminal being connected to the first actuator, and the fourth terminal being connected to the second actuator.

According to advantageous but not mandatory aspects, such an electrical system may incorporate one or more of the following features, alone or in any technically allowable combination:

the first contact and the second contact are normally open contacts.

The first and second circuit breaker devices are adapted to interrupt a DC current.

Drawings

The invention will be better understood and other advantages will become more apparent from the following description of one embodiment of the interconnect, given by way of example only and with reference to the accompanying drawings.

Fig. 1 is a diagram illustrating an electrical system including a circuit breaker apparatus and an interconnect apparatus according to one embodiment of the present invention;

figure 2 is a simplified circuit diagram of the electrical system of figure 1 when the interconnection device is connected to the circuit breaker device;

figure 3 is a diagram showing the interconnection arrangement of figure 1;

figure 4 is an example of a graph representing the variation of the amplitude of the control signal of the circuit breaker device of figure 1 over time.

Detailed Description

Fig. 1 shows an electrical system 2 comprising an assembly 4 of devices for interrupting an electrical current and an interconnection device 6.

According to an example, the assembly 4 comprises a first circuit breaker device C1 and a second circuit breaker device C2. Alternatively, the number of circuit breaker devices may be greater than 2.

Here, each breaker device C1 and C2 is adapted to interrupt DC current. For example, the circuit breaker devices C1 and C2 are contactors or relays.

Each circuit breaker device C1 and C2 includes electrical contacts or switches that can be reversibly switched between an open state and a closed state, respectively, to prevent or allow the passage of current.

Each circuit breaker device C1 and C2 further includes an actuator, in particular an electromagnetic actuator, configured to switch electrical contacts between an open state and a closed state in response to a control signal.

For example, the control signal is a voltage fed to a terminal of a coil of the actuator. All contacts are switched simultaneously, for example by an actuator.

In practice, each circuit breaker device C1 and C2 includes a housing, typically made of molded plastic, and an electrical connector, typically mounted on one face of the housing. The electrical connector is connected to the electrical contacts and to the actuator and allows to connect the latter to the electrical apparatus.

In this example, as shown in fig. 2, the circuit breaker device C1 includes three first

electrical contacts

40,42, and 44. The circuit breaker arrangement C2 includes eight second

electrical contacts

50,52,54,56,58,60,62 and 64.

However, the number of contacts of each breaker device C1, C2 may also be different. For example, the contact count of the circuit breaker device C1 is greater than or equal to one or two and less than or equal to five or ten. The number of contacts of the circuit breaker device C2 is, for example, greater than or equal to three or five and less than or equal to ten or twenty.

According to an embodiment, the

contacts

40,42, and 44 of the circuit breaker device C1 and the

contacts

50,52,54,56,58,60,62, and 64 of the circuit breaker device C2 are normally open contacts, that is, they remain open if no control signal is applied to the actuator.

The

first contacts

40,42, and 44 of the circuit breaker device C1 are preferably simultaneously in the same open or closed state and the

second contacts

50,52,54,56,58,60,62, and 64 of the circuit breaker device C2 are preferably all in the same open or closed state.

As shown in fig. 1, 2 and 3, the device 6 includes an input terminal 10, an output terminal 12 and

control terminals

14 and 16.

The

terminals

10 and 12 enable the system 2 to be connected to an electrical device. By way of illustrative example, in fig. 2, an electrical load 30 is connected between the output terminal 12 and another terminal 32 of the electrical device.

Here, the device 6 is intended to be connected to circuit breaker devices C1 and C2, so that the system 2 can interrupt the current flowing between the input terminal 10 and the output terminal 12. For example, the device 6 is removable and can be reversibly connected to the circuit breaker devices C1 and C2.

The

control terminals

14 and 16 are adapted to receive a control signal, in particular a control signal similar to the control signal for controlling one of the actuators of the circuit breaker devices C1 and C2.

Device 6 also includes first terminals L1/C1, T1/C1, L2/C1, T2/C1, L3/C1 and T3/C1, second terminals L1/C2, T1/C2, L2/C2, T2/C2, L3/C2, T3/C2,13NO/C2,14NO/C2,53NO,54NO,63NO,64NO,73NO,74NO,83NO and 84NO, third terminals a1/C1 and a2/C1 and fourth terminals a1/C2 and a 2/C2.

For example, each terminal includes a blade or pad of conductive material adapted to connect to a respective connector of the circuit breaker device C1 or C2.

According to an example, when the device 6 is connected to the assembly 4 to form the system 2, the first terminals L1/C1, T1/C1, L2/C1, T2/C1, L3/C1 and T3/C1 are electrically connected to the first

electrical contacts

40,42, 44.

More precisely, here the first terminals are grouped in pairs, each first terminal being connected to one first electrical contact. For example, the terminals L1/C1, T1/C1 are connected to opposite terminals of the contact 40, respectively. The terminals L2/C1, T2/C1 are connected to opposite terminals of the contact 42, respectively. The terminals L3/C1, T3/C1 are connected to opposite terminals of the contact 44, respectively.

In a similar manner, the second terminals L1/C2, T1/C2, L2/C2, T2/C2, L3/C2, T3/C2,13NO/C2,14NO/C2,53NO,54NO,63NO,64NO,73NO,74NO,83NO and 84NO are electrically connected to the second

electrical contacts

50,52,54,56,58,60,62,64, respectively.

Here, the second terminals are again grouped in pairs, each connected to one second electrical contact. For example, the terminals L1/C2, T1/C2 are connected to opposite terminals of the contact 50, respectively. Terminals 83NO,84NO are connected to opposite terminals of the contact 64, respectively, and so on.

The third terminals a1/C1 and a2/C1 are electrically connected to the actuator of the first circuit breaker device C1. The fourth terminals a1/C2 and a2/C2 are electrically connected to the actuator of the second circuit breaker device C2.

The device 6 is preferably preassembled and comprises a support 18, mounted on the support 18 are the

terminals

10, 12, 14 and 16, the first terminals L1/C1, T1/C1, L2/C1, T2/C1, L3/C1 and T3/C1, the second terminals L1/C2, T1/C2, L2/C2, T2/C2, L3/C2, T3/C2,13NO/C2,14NO/C2,53NO,54NO,63NO,64NO,73NO,74NO,83NO and 84NO, the third terminals a1/C1 and a2/C1 and the fourth terminals a1/C2 and a 2/C2.

For example, the support 18 is made of a plastic material, preferably a molded plastic material. According to an example, the support 18 forms a rigid or at least partially rigid armature.

The support 18 may optionally include one or more connector portions 20 visible from the exterior of the support 18 that connect portions of the support 18, particularly when the rigid portions of the support 18 that support the terminals are not integrally formed.

According to an example, device 6 is adapted to be mounted on the surface of circuit breaker devices C1 and C2, such that when device 6 is connected to circuit breaker devices C1 and C2, the terminals of device 6 are inserted into the respective connectors of circuit breaker devices C1 and C2. In the example of fig. 1, the circuit breaker devices C1 and C2 are aligned and arranged side-by-side, e.g., fixed to the same circuit board.

It is therefore clear that the arrangement and shape of the device 6 depend on the shape of the circuit breaker devices C1 and C2 and are therefore adapted according to the type of circuit breaker device that is intended to be connected with the device 6.

For example, as shown in fig. 1, the terminals are divided between a plurality of connection regions with

reference numerals

22, 24 and 26. The shape and size of the connection region is complementary to the layout of the connectors of the circuit breaker devices C1 and C2.

According to the illustrative example, the terminals of the device 6 are arranged along parallel rows, one of the terminals of each pair of terminals being placed in the upper row and the other terminal of the pair of terminals being placed in the lower row.

In the example shown in FIG. 3, terminals L1/C1, L2/C1, L3/C1, L1/C2, L2/C2, L3/C2,13NO/C2,53NO,63NO,73NO,83NO, A1/C1 and A1/C2 are placed in the upper row, and terminals 1/C1, T2/C1, T3/C1, T1/C2, T2/C2, T3/C2,14NO/C2,54NO,64NO,74NO,84NO, A2/C1 and A2/C2 are placed in the lower row.

According to an alternative embodiment, not shown, the support 18 comprises a fixing element enabling the support 18 to be reversibly fixed to the respective housings of the circuit breaker devices C1 and C2. The fixing elements may comprise hooks, screws, bolts, clamping means, fixing means relying on complementary shapes or any other equivalent fixing means.

The device 6 comprises a first circuit connecting the input terminal 10 and the output terminal 12 to the first terminals L1/C1, T1/C1, L2/C1, T2/C1, L3/C1 and T3/C1 and to the second terminals L1/C2, T1/C2, L2/C2, T2/C2, L3/C2, T3/C2,13NO/C2,14NO/C2,53NO,54NO,63NO,64NO,73NO,74NO,83NO to electrically connect the

first contacts

40,42,44 and the

second contacts

50,52,54,56,58,60,62 and 64 of the circuit breaker device C1, C2 between the input terminal 10 and the output terminal 12.

According to an embodiment, the first circuit is configured to electrically connect the

first contacts

40,42,44 in parallel between the input and

output terminals

10, 12. Further, the first circuit is configured to electrically connect the

second contacts

50,52,54,56,58,60,62, and 64 in series with each other and in parallel with the

first contacts

40,42,44 between the input and

output terminals

10, 12.

For example, the first circuit comprises an electrical conductor integrated into the support 18. In fig. 3, the electrical conductor of the first circuit is identified by the hatched area.

According to one example, the electrical conductor is a metal strip or cable and is fixed to the support 18 or integrated into the support 18, for example by overmoulding. According to another example, the electrical conductors are conductive tracks deposited on an insulating substrate, for example an insulating resin sheet, fixed to or integrated in the support 18.

In the example shown in fig. 3, the support 18 comprises

plates

70, 72, 74, 76, 78 and 80 associated with the

connection zones

22, 24 and 26 on which the terminals are mounted. For example,

plates

70, 74 and 78 are used to support the upper terminals, while

plates

72, 76 and 80 are used to support the lower terminals. Support 18 also includes

auxiliary plates

82, 84, 86, 88 and 90 that

interconnect plates

70, 72, 74, 76, 78 and 80 and form, at least in part, connector 20 therein. To make fig. 3 easier to read, the

connection regions

22, 24 and 26 are shown separated from each other.

In this illustrative and non-limiting example, the first circuit comprises a conductor connecting the input terminal 10 to the terminals L1/C1, L2/C1, L3/C1, L1/C2, another conductor connecting the output terminal 12 to the terminals T1/C1, T2/C1, T3/C1 and 83NO, and an additional conductor connecting two grounds to the other second terminals to connect the second contacts in series, as described above, as shown in fig. 2.

The device 6 also comprises a second circuit connecting the

control terminals

14 and 16 to the third and fourth terminals a1/C1, a2/C1, a1/C2 and a2/C2, in order to distribute the control signals applied between the

control terminals

14 and 16 to the third and fourth terminals.

For example, as described above, the control signal is a voltage here. When a voltage is applied between the

control terminals

14 and 16, a corresponding voltage is applied between the third terminal a1/C1 and a2/C1 and between the fourth terminal a1/C2 and a 2/C2.

For example, the first circuit comprises an electrical conductor integrated into the support 18. In fig. 3, the electrical conductors of the second circuit are identified by the shaded areas. The electrical conductors of the second circuit are for example similar to the electrical conductors of the first circuit.

The second circuit further comprises an electronic circuit 8, the electronic circuit 8 being configured to transmit the control signal for opening the electrical contacts received from the

control terminals

14 and 16 to the fourth terminals a1/C2 and a2/C2 with a predetermined time delay (T) delay.

For example, the electronic circuit 8 is connected between the control terminal and the fourth terminal. The electronic circuit 8 is mounted on a support 18, here a plate 74.

The amplitude of the voltage applied between the third terminal a1/C1 and a2/C1 (curve 100) and between the fourth terminal a1/C2 and a2/C2 (curve 102) when a command for opening the first and second contacts is received from the

control terminals

14 and 16 is represented by way of example in fig. 4.

Here, the abscissa axis t corresponds to time, and the ordinate axis V corresponds to an amplitude value in volts. To make fig. 4 easy to read, a vertical offset has been applied to the curve 100.

For example, in the case of a normally open contact, the command to open the contact corresponds to a transition of the control voltage from a first amplitude value (for example equal to 5 volts DC) to a second amplitude value (for example zero volts) lower than the first amplitude. In other words, according to these examples, the supply of power to the coil of the actuator of the circuit breaker device is stopped to force the electrical contacts of the circuit breaker device to return to their open state.

Thus, the second circuit and the electronic circuit 8 are configured to provide a delayed control signal (curve 102) to the fourth terminals a1/C2 and a2/C2, wherein the transition of the voltage to the second amplitude value is delayed by a time delay T with respect to the signal (curve 100) transmitted to the third terminals a1/C1 and a 2/C1.

Thus, when the voltage on the

control terminals

14 and 16 disappears, the actuator of the first circuit breaker device C1 immediately stops supplying power. On the other hand, due to the delay imposed by the electronic circuit 8, the actuator of the second circuit breaker device C2 continues to be powered for the time delay T and stops being powered when the time delay T expires.

According to an example, the time delay T has a duration between 5ms and 50ms, including 5ms and 50 ms.

For example, the electronic circuit 8 comprises one or more passive components which enable to delay the transmission of the opening command to the fourth terminals a1/C1 and a2/C1, that is to say here to keep the voltage between the fourth terminals a1/C1 and a2/C1 equal to the first amplitude value within the time delay T after the voltage between the

control terminals

14, 16 has been interrupted.

For example, the electronic circuit 8 comprises a capacitor connected between the

terminals

14, 16 and the fourth terminal, which capacitor is adapted to keep the voltage between the fourth terminal a1/C1 and a2/C1 (but not between the third terminal a1/C1 and a2/C1) equal to the first amplitude value for a time delay T once the voltage between the

control terminals

14, 16 is interrupted.

The interconnection device 6 enables a modular combination of two or more circuit breaker devices C1, C2 to form an electrical system 2 suitable for interrupting a DC current having a magnitude and/or voltage higher than the rating of each of said circuit breaker devices C1, C2, respectively.

As an illustrative, non-limiting example, each breaker device C1 and C2 is rated at 300V DC and rated at 32 amps (a). Thanks to the device 6, the system 2 formed by the combination of the circuit breaker devices C1 and C2 is able to interrupt the current even at voltages greater than 300V DC, for example up to 1000V DC for voltages and up to 75A for currents.

The device 6 is preassembled, making it easier to connect the circuit breaker devices C1 and C2 to form the system 2. The user does not need to manually wire all of the connections between the circuit breaker devices C1 and C2, thereby saving time and limiting connection errors that may occur with manual wiring installation.

Thus, users can build a system 2 suitable for their requirements based on existing circuit breaker devices C1, C2.

By connecting the

second contacts

50,52,54,56,58,60,62 and 64 in series between the

terminals

10 and 12, the current is more easily interrupted, because the greater the number of second contacts in series, the greater the voltage drop per second contact. There is less risk that an arc will stay at the level of only one

second contact

50,52,54,56,58,60,62 or 64 when interrupting the current.

By connecting the

first contacts

40,42,44 in parallel between the

terminals

10 and 12 with the

second contacts

50,52,54,56,58,60,62, and 64, when the system 2 is in operation, the current flowing in the

second contacts

50,52,54,56,58,60,62, and 64 is reduced, limiting heat dissipation.

The device 6 thus enables the system 2 to be constructed with a good compromise between interrupting power and dissipating heat.

The delay in opening the

second contacts

50,52,54,56,58,60,62, and 64 when the open command is received enables the

first contacts

40,42,44 to be opened before the second contacts. In fact, since the system 2 may use currents in excess of the rating of the circuit breaker device C1, and the

first contacts

40,42,44 are connected in parallel, the

first contacts

40,42,44 may not be able to interrupt the currents themselves if the

second contacts

50,52,54,56,58,60,62, and 62 open before the

first contacts

40,42, 44.

Many other embodiments are possible. In particular, the above teachings may be translated into many different circuit breaker devices or circuit breaker devices comprising a different number of contacts or different geometric configurations than those described, or again into circuit breaker devices having normally closed contacts instead of normally open contacts.

The embodiments and variants envisaged above may be combined with each other to create new embodiments.

Claims

1. An interconnect device (6), comprising:

-a first terminal (L1/C1, T1/C1, L2/C1, T2/C1, L3/C1, T3/C1) configured to be electrically connected to a first electrical contact (40,42,44) of a first means (C1) for interrupting an electrical current;

-second terminals (L1/C2, T1/C2, L2/C2, T2/C2, L3/C2, T3/C2,13NO/C2,14NO/C2,53NO,54NO,63NO,64NO,73NO,74NO,83NO,84NO) configured to be electrically connected to second electrical contacts (50,52,54,56,58,60,62,64) of a second device (C2) for interrupting an electrical current;

-a third terminal (a1/C1, a2/C1) configured to be electrically connected to a first actuator for actuating the first circuit breaker device;

-a fourth terminal (a1/C2, a2/C2) configured to be electrically connected to a second actuator for actuating a second circuit breaker device;

-an input terminal (10), an output terminal (12) and control terminals (14, 16);

-a second circuit connecting the control terminals to the third and fourth terminals to distribute the control signals applied between the control terminals (14, 16) to the third terminal (a1/C1, a2/C1) and to the fourth terminal (a1/C2, a2/C2), the second circuit further comprising an electronic circuit (8) connected between the control terminals and the fourth terminal, the electronic circuit being configured to transmit the control signals received from the control terminals for opening the electrical contacts to the fourth terminal with a predetermined time delay (T).

2. Interconnect device (6) according to claim 1, characterized in that the interconnect device (6) is pre-assembled and comprises a support (18), first terminals (L1/C1, T1/C1, L2/C1, T2/C1, L3/C1, T3/C1), second terminals (L1/C2, T1/C2, L2/C2, T2/C2, L3/C2, T3/C2,13NO/C2,14NO/C2,53NO,54NO,63NO,64NO,73NO,74NO,83NO,84NO), third terminals (a1/C1, a2/C1) and fourth terminals (a1/C2, a2/C2), an input terminal (10), an output terminal (12) and control terminals (14, 16) are mounted on the support, and the first and second circuits are integrated into the support.

3. Interconnection device (6) according to claim 2, characterized in that the support (18) is made of plastic, preferably molded plastic.

4. Interconnect device (6) according to any of the preceding claims, characterized in that the first circuit is configured to electrically connect the first electrical contacts (40,42,44) in parallel between the input and output terminals (10, 12).

5. Interconnect device (6) according to any of the preceding claims, characterized in that the first circuit is configured to electrically connect the second electrical contacts (50,52,54,56,58,60,62 and 64) in series with each other and in parallel with the first electrical contacts (40,42,44) between the input and output terminals (10, 12).

6. Interconnect device (6) according to any of the preceding claims, characterized in that the control signal for opening comprises a transition of a voltage applied to the control terminals (14, 16) from a first amplitude value to a second amplitude value lower than the first amplitude value, the electronic circuit (8) being configured to provide the delayed control signal (102) to the fourth terminal (a1/C2, a2/C2), wherein the transition of the voltage to the second amplitude value is delayed by a time delay (T) with respect to the control signal (100) transmitted to the third terminal (a1/C1, a 2/C1).

7. Interconnect device (6) according to any of the preceding claims, characterized in that the duration of the time delay (T) is in the range of 5 to 50 milliseconds.

8. An electrical system (2), comprising:

-a first device (C1) for interrupting the current, comprising a first electrical contact (40,42,44) and a first actuator configured to switch the first electrical contact between an open state and a closed state according to a control signal;

-second means (C2) for interrupting the current, comprising second electrical contacts (50,52,54,56,58,60,62,64) and a second actuator configured to switch the second electrical contacts between an open state and a closed state according to a control signal;

-an interconnection device (6) according to any one of the preceding claims;

in the system, an interconnection device (6) is connected to the first and second circuit breaker devices, a first terminal (L/C, T/C, L/C, T/C, L/C, T/C) is connected to the first contact (40,42,44), a second terminal (L/C, T/C, L/C, T/C, 13NO/C, 14NO/C, 53NO,54NO,63NO,64NO,73NO,74NO,83NO,84NO) is connected to the second contact (50,52,54,56,58,60,62,64), a third terminal (A/C ) is connected to the first actuator, and a fourth terminal (A/C ) is connected to the second actuator.

9. The electrical system (2) of claim 8, wherein the first (40,42,44) and second (50,52,54,56,58,60,62,64) contacts are normally open contacts.

10. The electrical system (2) according to claim 9, wherein the first and second circuit breaker devices (C1, C2) are adapted to interrupt a DC current.