EP3032557A1 - Direct current circuit for high voltage on-board networks - Google Patents

Abstract

The invention relates to a DC voltage switch (1) for high-voltage vehicle electrical systems, comprising a housing (2), at least two fixed contacts (4) and a movable contact (6), wherein in each case a first contact region (4a) of the fixed contacts (4) the housing (2) is led out and in each case a second contact region (4b) of the fixed contacts (4) in a switching chamber (10) of the housing (2) with the movable contact (6) is arranged, wherein the housing (2) hermetically encapsulated wherein a cooling chamber (11) is arranged above the switching chamber (10), which is separated from the switching chamber (10) via a dividing wall (9), the dividing wall (9) having at least one outlet opening (12) and at least one inlet opening (12). 13).

Description

The invention relates to a DC voltage switch for high-voltage vehicle electrical systems.

For example, in electric or hybrid vehicles DC switches are required to electrically isolate various parts of a high-voltage electrical system.

DC currents, unlike AC currents, have no natural current zero crossing, which is why the interruption of such currents is associated with particular challenges. Interruption of the currents and erosion of switching arcs occurring is usually accomplished by extending the length of the arc columns and / or increasing the power per unit length. However, the breaking capacity of hermetically encapsulated switching devices or DC voltage switches is limited in terms of current levels and ohmic-inductive time constants, the limiting factor being in particular the thermal capacity, since the electrical power in the arc must be thermally absorbed.

In the low voltage area, this problem is often solved by the fact that the DC voltage switches are not hermetically encapsulated. This allows the hot gases to be dissipated. Such a solution is for example in the DE 35 41 514 C2 disclosed.

From the DE 690 18 432 T2 is a multi-pole low-voltage circuit breaker in a equipped with a double cooling device for the extinguishing gases insulating housing is known, which is divided by insulating intermediate walls in several internal compartments. These are each assigned to one of the poles and each comprise a separable pair of contacts, a splitter stack for deionization of the drawn during the separation of said contacts arc and equipped with a first gas cooling device outlet opening for the extinguishing gases. In this case, all the outlet openings open into a common chamber to the individual poles, which is connected via a gas outlet opening with the surrounding medium. A second cooling device is inserted in the flow path of the gases between the outlet openings and the gas outlet opening.

From the DE 10 2012 112 202 A1 is a DC voltage switch comprising a housing with a switching chamber and a contact arrangement in the switching chamber, known. The housing is hermetically sealed and electrically insulated. Arranged in the housing is at least one fixed contact and at least one movable contact, wherein the respectively fixed and the respectively movable contact are arranged within the housing as a contact pair.

From the working paper "Switching Devices for Switching High DC Voltage in Energy Systems and Electrically Driven Vehicles", VDE Discussion Event: DC Contact Behavior and Switching at U> 300 VDC, Dr. Matthias Kroeker et al., Tyco Electronics, September 7, 2010 a generic DC voltage switch for high-voltage vehicle electrical systems is known, comprising a housing, at least two fixed contacts and a movable contact, wherein in each case a first contact region of the fixed contacts is led out of the housing and in each case a second contact region of the fixed contacts in a switching chamber of the housing the movable contact is arranged, wherein the housing is hermetically encapsulated. The extinction of the occurring partial arcs is achieved by their power output is increased beyond the driving power. For this purpose, the generated arc voltage is increased and maintained above the driving source voltage until the system current is forced to 0 A and the energy stored in the inductance of the electrical circuit is used up.

The invention is based on the technical problem of providing a DC voltage switch for high-voltage vehicle electrical systems, which has an improved turn-off behavior.

The solution of the technical problem results from a DC voltage switch with the features of claim 1. Further advantageous embodiments of the invention will become apparent from the dependent claims.

The DC voltage switch for high-voltage vehicle electrical systems comprises a housing, at least two fixed contacts and a movable contact, wherein in each case a first contact region of the fixed contacts is led out of the housing. In each case, a second contact region of the fixed contacts is arranged in a switching chamber of the housing with the movable contact. The housing is hermetically sealed. Above the switching chamber, a cooling chamber is arranged, which is separated via a partition wall of the switching chamber, wherein the partition wall has at least one outlet opening and an inlet opening. This causes three positively influencing the switching behavior Results. On the one hand, the thermal capacity of the DC voltage switch is increased by the additional cooling chamber. In addition, there is an increased thermal energy removal from the switching chamber and finally, by a suitable choice of the outlet and inlet openings, a self-excited gas flow can be generated within the switching chamber, which presses the arc towards the housing walls. This causes an improved switching behavior of the DC voltage switch. The high-voltage vehicle electrical system, for example, has DC voltages greater than 300 V.

In one embodiment, at least one heat sink, which is thermally connected to at least one of the fixed contacts, is arranged in the cooling chamber. As a result, the hot gas is withdrawn more heat and removed via the fixed contact from the housing. In this case, the heat sink may also be connected to two fixed contacts or else the heat sink is only connected to the housing, via which the heat is dissipated. Likewise, both measures can be combined. Preferably, a plurality of heat sinks are provided, for example, four heat sinks, in which case, for example, two half-shell-shaped heat sink are each associated with a fixed contact.

In a further embodiment, the at least one outlet opening is arranged between the fixed contact and the housing inner wall. Preferably, the DC voltage switch has more than one outlet opening. For example, the DC voltage switch has four outlet openings, two of which are assigned to a fixed contact. Due to the application in the area of the inner wall of the housing, the outlet opening is located in the area where the hottest gases occur. In this case, the outlet opening may be conically shaped, wherein the diameter on the side of the switching chamber is larger than the diameter on the side of the expansion chamber. For example, the outlet opening may have the shape of a Laval nozzle. A Laval nozzle is a flow organ with a first convergent and subsequent divergent cross-section, the transition from one to the other part being gradual. The cross-sectional area is circular at each location. Also, a valve may be disposed in the outlet port to assist in directed gas flow.

In a further embodiment, the at least one inlet opening is arranged between the stationary contacts. As a result, the cooled gas is flowed into the arc, which supports its expansion in the direction of the housing walls. Accordingly, more than one, for example four, inlet openings may be provided. Also the inlet openings may be conical or in the form of a Laval nozzle and / or have a valve. In the case of the conical design, the diameter on the side of the expansion chamber is preferably larger than the diameter on the side of the switching chamber.

In a further embodiment, hydrogen or nitrogen is in the housing as a gas. Hydrogen offers the advantage of high energy absorption in the arc, but limits the choice of contact material and poses major challenges in terms of hermetic sealing. Nitrogen is easier to handle and allows greater freedom in material choice, such as silver for the contacts rather than copper.

In a further embodiment, the housing is made of ceramic, for example of aluminum nitride. In this case, the housing may also consist only partially of ceramic, wherein preferably the housing consists of a uniform material. The advantage of ceramic over plastics is that ceramics are fire-robuster, so there is no burn-up due to the arcing. Another advantage is the generally better thermal conductivity compared to plastics. In principle, the housing but also made of plastic.

In a further embodiment, the heat sink or the heat sink are made of copper, in which case preferably also the fixed contacts are made of copper. Heat sink and contact can be contacted thermally well by thermal paste.

Alternatively, the heat sink or the heat sinks are formed of a thermally conductive ceramic, but which is not electrically conductive.

The one or more heat sinks, as already stated, while being thermally connected to the housing, which may be connected either only to the housing or in addition to the fixed contacts, which increases the thermal heat dissipation.

In another embodiment, an insulating plate is disposed on the housing between the first contact areas of the fixed contacts to prevent flashover.

In principle, it is also possible to arrange on the housing outer walls permanent magnets that generate a supporting magnetic field.

Fig. 1

eine perspektivische Darstellung eines Gleichspannungsschalters,

Fig. 2

eine Querschnittsdarstellung des Gleichspannungsschalters, wobei die Schnittlinie durch die beiden feststehenden Kontakte verläuft,

Fig. 3

eine Schnittdarstellung, wobei der Schnitt vor einem feststehenden Kontakt verläuft,

Fig. 4

eine perspektivische Schrägdarstellung des Gleichspannungsschalters und

Fig. 5

eine perspektivische Vorderansicht des Gleichspannungsschalters.

The invention will be explained in more detail below with reference to a preferred embodiment. The figures show:

Fig. 1

a perspective view of a DC switch,

Fig. 2

4 is a cross-sectional view of the DC switch with the cut line passing through the two fixed contacts;

Fig. 3

a sectional view, wherein the section runs in front of a fixed contact,

Fig. 4

a perspective oblique view of the DC switch and

Fig. 5

a front perspective view of the DC switch.

In the Fig. 1 a DC voltage switch 1 is shown in the assembled state, comprising a housing 2, protrude from the two first contact portions 4a of two fixed contacts 4. The housing 2 is formed in three parts and has a lower part 2a, a middle part 2b and an upper part 2c. Between the first contact areas 4a an insulation plate 3 is arranged, which is shown in dashed lines. The lower part 2a, middle part 2b and upper part 2c are screwed, for example, which is indicated by holes 5. The connection of the housing parts is designed such that the housing 2 is hermetically encapsulated.

As in the Fig. 2 and 3 shown, the DC voltage switch 1 in addition to the two fixed contacts 4 and a movable contact 6, which is arranged below the fixed contacts 4. The movable contact 6 can be moved by a spring, not shown, in the direction of the stationary contacts 4, so that the movable contact 6 contacts second contact areas 4b of the fixed contacts 4. The movement of the movable contact 6 is guided by guide elements 7, 8 in the lower part 2a and upper part 2c. Above the second contact areas 4b, a partition wall 9 is arranged. In this case, a switching chamber 10 is formed below the partition wall 9 and a cooling chamber 11 above the partition wall 9. The switching chamber 10 and the cooling chamber 11 are connected to each other via outlet openings 12 and inlet openings 13. In this case, the outlet openings 12 shown in dashed lines lie between the fixed contacts 4 and the housing inner wall 2d and are conical. In this case, the outlet opening 12 is formed frusto-conical and merges into a cylindrical opening, wherein the larger diameter is located on the side of the switching chamber 10. The inlet openings 13 are located between the fixed contacts 4, the exact location is particularly good in Fig. 4 is recognizable. Also, the inlet openings 13 are conical, with their larger diameter on the side of the cooling chamber 11. Alternatively, the outlet openings 12 and / or the inlet openings 13 may have the shape of a Laval nozzle. Furthermore, cooling bodies 14 are arranged in the cooling chamber 11, which are thermally connected to the fixed contacts 4, for example by means of a thermal compound. In this case, the heat sink 14 are half-shell-shaped, which are slightly asymmetrical. In the switching chamber 10 and the expansion chamber 11 is a gas, for example hydrogen or nitrogen.

If an existing contact between the movable contact 6 and the second contact regions 4b of the stationary contacts 4 is opened, an arc is produced. This arc must absorb the energy stored in an inductive load. Due to the ionization of the gases, there is a current flow that generates a magnetic field. This magnetic field is directed towards the housing inner wall 2d, which is dashed in Fig. 2 is shown. The heated and ionized gas molecules are thus moved in the direction of the housing inner wall 2d, where an overpressure builds up, which is degraded by outflow from the outlet openings 12. In this case, the guide element 8 in the switching chamber 10 separates the flows to the left and to the right housing inner wall 2a, so that they do not interfere with each other.

In the cooling chamber 11, the hot gas flows past the heat sinks 14 and gives off heat to then flow back through the inlet openings 13, since there the pressure is lower. The return flow of the gases presses the gases in the switching chamber 10 in addition to the magnetic field in the direction of the housing inner wall 2d. The heat absorbed by the heat sinks 14 is then removed via the fixed contacts 4 from the housing 2. The arc is thus deprived of energy and this goes out.

In the 4 and 5 the DC voltage switch 1 is shown without central part 2b and upper part 2c, wherein additionally two heat sinks 14 have been removed so that the front outlet openings 12 and inlet openings 13 can be seen, wherein the rear outlet openings 12 and inlet openings 13 are covered by the rear heat sink 14. Next, a slot 15 for the guide element 8 can be seen. Here are the Outlet openings 12 and inlet openings 13 a little offset (or for the invisible postponed) to the fixed contacts 4. It should be noted that the heat sink 14 in the 4 and 5 in their training different from the heat sinks 14 in the Figures 2 and 3 are.

Claims (9)

DC voltage switch (1) for high-voltage vehicle electrical systems, comprising a housing (2), at least two fixed contacts (4) and a movable contact (6), wherein in each case a first contact region (4a) of the fixed contacts (4) from the housing (2 ) is led out and in each case a second contact region (4b) of the fixed contacts (4) in a switching chamber (10) of the housing (2) with the movable contact (6) is arranged, wherein the housing (2) is hermetically encapsulated,
characterized in that
above the switching chamber (10) a cooling chamber (11) is arranged, which is separated from the switching chamber (10) via a dividing wall (9), wherein the dividing wall (9) has at least one outlet opening (12) and at least one inlet opening (13) , DC voltage switch according to claim 1, characterized in that in the cooling chamber (11) at least one heat sink (14) is arranged, which is thermally connected to at least one of the fixed contacts (4) and / or the housing (2). DC voltage switch according to claim 1 or 2, characterized in that the at least one outlet opening (12) between stationary contact (4) and housing inner wall (2d) is arranged. DC voltage switch according to one of the preceding claims, characterized in that the at least one inlet opening (13) between the fixed contacts (4) is arranged. DC voltage switch according to one of the preceding claims, characterized in that in the housing (2) is hydrogen or nitrogen. DC voltage switch according to one of the preceding claims, characterized in that the housing (2) is made of ceramic. DC voltage switch according to one of claims 2 to 6, characterized in that the heat sink (14) is made of copper. DC voltage switch according to one of claims 2 to 6, characterized in that the cooling body (14) consists of a thermally conductive ceramic. DC voltage switch according to one of the preceding claims, characterized in that an insulation plate (3) is arranged on the housing (2) between the first contact regions (4a) of the fixed contacts (4).

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