Cooled busbar and charging system

Abstract

An electrical busbar (100) is proposed, which is designed as a hollow profile (101), the cavity (104) of which is flowed through by a coolant. The busbar has an inlet connection and an outlet connection, wherein the inlet connection is designed to allow a coolant to flow into the cavity. The outlet connection is designed to allow the coolant to flow out of the cavity. Contact pieces (107) are integrally and electrically conductively connected to the ends (106) of the busbar and the hollow profile, respectively, and tightly seal the cavity. Furthermore, a charging system with such a busbar is proposed.

Description

Area

[0001] The invention relates to a cooled busbar and a charging system with such a busbar, in particular for battery electric vehicles. background

[0002] The spread of electric vehicles is constantly increasing, which is politically and socially desirable in order to reduce exhaust emissions, particularly in urban areas, while at the same time lowering CO2 emissions from traffic to the extent that so-called green electricity is available to operate the vehicles. One obstacle to the further spread of electric vehicles, in addition to the limited electric range, is the time required to charge a vehicle's battery. Charging the battery of an electric vehicle still takes considerably longer than refueling a conventional vehicle with a combustion engine, which can typically be done in just a few minutes. There is therefore a desire to shorten the required charging time by increasing the electrical charging power. Currently, charging voltages are up to 500 V, which can achieve a charging power of 50 kW.At such high charging currents, ohmic heat naturally develops in the conductors that connect the electric vehicle's charging socket to its battery storage unit. Nevertheless, during a rapid charging process lasting, for example, 15 minutes, temperature limits must not be exceeded, particularly at the connection contacts of the charging socket or battery storage unit. One way to achieve this goal is to increase the cross-section of the connecting cable that connects the charging socket to the battery storage unit, which is often designed as a busbar, so that the permissible temperature limits are not reached at critical points. The disadvantage of this approach is that it requires a high level of material and simultaneously increases the vehicle weight, which is generally undesirable.An alternative option is to cool the busbars that carry the charging current to prevent limit temperatures from being reached or exceeded.

[0003] DE 10 2021 132 397 A1 describes a charging cable for connecting a battery of an electric vehicle to a charging interface. The charging cable comprises two lines, each designed as hollow profiles, each with a cooling channel through which the cooling medium flows. The lines have connection elements for the cooling medium.

[0004] DE 10 2017 103 268 A1 discloses an electrical cable formed as a hollow profile with channels separated from each other by internal webs. The interior of the conductor profile serves to conduct a heat transfer medium.

[0005] Based on this, the present invention has the object of creating a busbar and a charging system with such a busbar in order to overcome or at least improve one or more of the problems mentioned above. Description of the invention

[0006] To achieve this object, the invention proposes, according to a first aspect, an electrical busbar which is designed as a hollow profile, the cavity of which is through which a coolant flows. The busbar has an inlet connection and an outlet connection, wherein the inlet connection is designed to allow a coolant to flow into the cavity. The outlet connection is designed to allow the coolant to flow out of the cavity. Contact pieces are materially and electrically conductively connected to the ends of the busbar or the hollow profile and tightly close the cavity. The cavity is divided into a plurality of individual cavities by partition walls. In a first individual cavity, the coolant flows in a first flow direction. In a second individual cavity, the coolant flows in a second flow direction which is opposite to the first flow direction.

[0007] The busbar is particularly suitable for installation in electric vehicles to connect a charging socket to an electric battery storage unit. The coolant flowing through the busbar limits the temperature rise, especially at the contact pieces, to values ​​that are still permissible for contact points, for example, to 90°C, particularly during rapid charging. The coolant also cools the contact piece via the integral connection between the busbar and the contact piece. At the same time, the contact pieces seal the cavity of the busbar and prevent the coolant from escaping. The coolant thus flows through the busbar in a closed cooling circuit. The partition walls increase the contact area between the coolant and the current-carrying metal. This increases the cooling effect of the coolant on the busbar.

[0008] The opposing flow directions in the individual cavities allow a uniform temperature distribution to be achieved in charging systems that have two busbars.

[0009] According to a second aspect, the invention relates to a charging system for a battery-electric power storage device. The charging system has a connection that can be connected to a power source, a current sink, a busbar according to the first aspect of the invention, which electrically connects the power source to the current sink, and a heat sink through which the coolant flows. The charging system comprises two busbars, each of which is fluidly and electrically insulated from one another at one end, so that the coolant flows out of one busbar and into the other busbar. The other ends of the two busbars have an inlet connection and an outlet connection, respectively, which are fluidly connected to the heat sink. The charging system comprises two busbars, each of which has two or more individual cavities in which the coolant flows in opposite directions.

[0010] In one embodiment, the power source is a charging station and the power sink is a battery storage unit. The charging station is connected to the usable port with a charging cable and supplies the charging current to charge the battery storage unit.

[0011] The heat sink may be any arrangement suitable for absorbing heat from the coolant flowing through the bus bars.

[0012] This design of the charging system means that coolant that has cooled down in the heat sink and coolant that has already flowed through the other busbar and has a higher temperature than the coolant coming from the heat sink flow through each of the two busbars. This ensures that the two busbars have approximately the same temperature. In contrast, in a charging system in which the coolant first flows through one busbar and then the other busbar before returning to the heat sink, temperature differences can occur between the busbars. This can result in the warmer busbar reaching a permissible limit temperature more quickly than in a charging system in which the busbars are at a uniform temperature.

[0013] In one embodiment, the heat sink is a heat exchanger, a battery storage device, an electrical machine and / or a device for regulating the temperature of an interior space.

[0014] In one embodiment, the heat exchanger is air-cooled. Short description of the drawing

[0015] The invention will be explained in more detail below using an exemplary embodiment with reference to the accompanying figures. All figures are purely schematic and not to scale. They show: Fig. 1A a busbar according to the invention; Fig. 1B an alternative hose connection for a coolant for the Fig. 1A shown busbar; Fig. 1C a second alternative hose connection for a coolant for the Fig. 1A shown busbar; Fig. 2A-C show embodiments of a charging system with a busbar according to the invention; and Fig. 3 another busbar according to the invention in cross section.

[0016] Identical or similar elements are provided with identical or similar reference numerals in the figures. Example

[0017] Fig. 1A shows a busbar 100 according to the present invention. The busbar 100 is formed from a rectangular tube 101 having two narrow sides 102a,b and two wide sides 103a,b. In one embodiment of the busbar 100, the rectangular tube 101 is made of aluminum or copper. In principle, the rectangular tube 101 can also be made of other materials with good electrical conductivity. It is noted that the present invention is not limited to rectangular tubes; other tube cross-sections can also be used, for example, round, oval, or polygonal tube cross-sections. The following description, however, refers to rectangular tubes because they are frequently used in practice. The narrow sides 102a,b and the wide sides 103a,b form a circumferential wall that encloses a cavity 104.The rectangular tube 101 has two ends 106, to each of which a contact piece 107 is attached by means of a materially bonded connection, so that a mechanically stable connection is created between the rectangular tube 101 and the contact pieces 107, and at the same time the interior 104 is tightly sealed at the ends 106 of the rectangular tube 101. The contact pieces 107 are, for example, welded or soldered. A threaded hole 108 is provided in the wide side 103a, into which a hose nipple 109 can be screwed in order to establish a fluid connection between the interior 104 and a hose 111. The connection shown in . Fig. The threaded hole 108 shown in Figure 1A forms an inlet opening. Fig. The end of the rectangular tube 101 not shown in Figure 1A forms a corresponding outlet opening which, with the arrangement of a further hose nipple and a hose 111, also establishes a flow connection to the interior 104 of the rectangular tube 101.

[0018] The rectangular tube 101, closed at its ends 106 with contact pieces 107 and provided with an inlet and outlet opening, forms a busbar 100 according to the present invention. During operation of the busbar 100, the rectangular tube 101 fulfills two functions: the function of an electrical conductor by means of the walls of the rectangular tube 101 and the function of a fluid conductor for a coolant, with the cavity 104 enclosed by the walls of the rectangular tube 101 forming the fluid conductor. For electrical insulation, the rectangular tube 101 is encased in an insulating jacket 108.

[0019] Any flowable gaseous or liquid medium with low electrical but high thermal conductivity is suitable as a coolant. In practice, liquids are easier to control than gases, so for the sake of brevity, the embodiments are described using a liquid as the coolant. This should not be understood as limiting the invention to liquids as coolants. One example of a suitable coolant is commercially available from 3M under the brand name Novec 7000.

[0020] Using hoses 111, it is possible to circulate a coolant through the busbar 100, thereby controlling the temperature of the busbar. The contact pieces 107 are also cooled by heat conduction between the rectangular tube 101 and the contact pieces 107. Cooling of the busbar 100 is achieved by heat transfer from the rectangular tube or the walls of the rectangular tube to the coolant. The coolant, in turn, is cooled in a cooler. Any heat sink that lowers the temperature of the coolant as it flows through it functions as a cooler. Different designs of a heat sink are described below.

[0021] Fig. Figure 1B shows an alternative hose connection 120, which is constructed from two parts. A connection component 121 has a hose nozzle 122, which is fluidically connected to a nozzle arranged on the connection component 121 (in Fig. 1B not shown) and establishes a fluid connection with the cavity 104 of the rectangular tube 101. The connecting component 121 is locked to a holding component 123 so that the rectangular tube 101 is guided between the connecting component 121 and the holding component 123. The hose nozzle 122 is used to establish a cooling circuit for the coolant flowing in the rectangular tube 101 by attaching a hose to the hose nozzle 122.

[0022] Fig. Figure 1C shows another alternative hose connector 130, which is constructed from two parts. A connecting component 131 has a hose door 132, which is fluidically connected to a nozzle arranged on the connecting component (in Fig. 1B not shown) and establishes a fluid connection with the cavity 104 of the rectangular tube 101. The connecting component 131 is screwed to a holding component 133 in such a way that the rectangular tube 101 is guided between the connecting component 131 and the holding component 133 and clamped. The hose nozzle 132 can be used to create a cooling circuit for the coolant flowing in the rectangular tube 101 with a hose. For this purpose, a hose is slipped onto the hose nozzle 132.

[0023] Fig. 2A schematically shows a section of a charging system 200-1 for an electric vehicle, in particular a battery-electric vehicle, in which very high charging currents flow during a rapid charging process, leading to correspondingly high heating in the current-carrying lines. An electric vehicle is an example of an application of the invention. In principle, the invention is suitable for all applications where high currents flow, leading to heating of the current-carrying conductors or contacts, which must not exceed permissible limit temperatures and therefore require appropriate cooling of the current-carrying lines and contacts.

[0024] The charging system 200-1 comprises a charging socket 201, which is arranged in an accessible manner on the exterior of a body of the electric vehicle. During a charging process, a charging cable is plugged into the charging socket, which connects the charging socket to a charging station that supplies the power to charge a battery of the electric vehicle. The charging socket 201 is connected to a high-voltage battery 202 via two busbars 100a,b. For this purpose, the busbars 100a,b are connected, for example, screwed, to corresponding connection contacts on the charging socket 201 and the high-voltage battery 202 via contact pieces 107.

[0025] A hose 111a of the busbar 100a is connected to a coolant outlet 203 of the high-voltage battery 202, which is equipped with a coolant circuit and has its own coolant cooler (not shown). The coolant flows in the busbar 100a to a connecting piece 204 arranged at the opposite end of the busbar 100a, which connects a coolant outlet opening of the busbar 100a to a coolant inlet opening 206 of the busbar 100b. The coolant flows through the busbar 100b to a hose 111b, which is connected to a coolant inlet 206 of the high-voltage battery 202. The flow direction of the coolant is indicated by arrows 207a, 207b. The coolant cooled by the cooling circuit of the high-voltage battery 202 ensures cooling of the busbars 100a, b during a rapid charging process, which is time-limited oris aborted if a limit temperature on a critical component of the charging system is exceeded.

[0026] Fig. 2B is another schematic representation of a charging system 200-2. In contrast to the charging system 200-1, the hoses 111 are not connected to a cooling circuit of the high-voltage battery 202, but rather to a heat exchanger 208, which cools the coolant flowing in the busbars 100a,b and thus dissipates heat from the busbars 100a,b. The heat exchanger 208 can be a dedicated heat exchanger intended exclusively for cooling the coolant flowing into the busbars 100a,b. However, the heat exchanger 208 can also have multiple media circuits and can be used, for example, for temperature control of a vehicle interior, the high-voltage battery, and / or a drive motor, among other things.

[0027] Fig. 2C schematically shows another charging system 200-3 in which the coolant flowing in the busbars 100a,b flows through a cooling coil 209 and is cooled by an air flow generated by a fan 211.

[0028] In all charging systems 200-1, 200-2 and 200-3, the cooling of the busbars 100a,b is dimensioned so that a fast charging process can be carried out without interruption.

[0029] Fig. Figure 3 shows a perspective view of a rectangular tube 301 for a busbar. The rectangular tube 301 has partition walls 302 that divide an interior space enclosed by the rectangular tube 301 into several individual cavities 303. Coolant flows within the individual cavities to cool the rectangular tube 301. Due to the partition walls 302, the contact area between the coolant and the current-carrying material of the rectangular tube is larger compared to a rectangular tube with a single interior space.

[0030] In a practical application in an electric vehicle, cooled coolant preferably flows from the heat sink into the busbar at a positive potential (HV+) and returns to the heat sink via the other busbar at ground potential (HV). In principle, the coolant can also be routed in the opposite direction. In any case, the invention is not limited to a specific flow direction. If busbars with rectangular tubes are used, opposite flow directions can also occur simultaneously, as explained below.

[0031] In the individual cavities 303, the coolant can also flow in different directions, so that in a charging system with two busbars, both coolant that has cooled down in the heat sink and coolant that has already flowed through the other busbar and has a higher temperature than the coolant coming from the heat sink flow through both busbars. Fig.3, the different flow directions are indicated by arrows 304. This ensures that the two busbars have approximately the same temperature. In contrast, in a charging system in which the coolant first flows through one busbar and then the other busbar before returning to the heat sink, temperature differences can occur between the busbars. This can result in a permissible limit temperature being reached more quickly by the warmer busbar than in a charging system in which the busbars are at a uniform temperature.

[0032] In principle, a user can determine the flow direction as desired. However, in a practical embodiment, it has proven advantageous for the coolant originating from the heat sink to flow in the inner individual cavities 303, while the coolant flowing from the respective other busbar flows in the outer individual cavities 303. List of reference symbols 100 busbar 101 Rectangular tube 102a,b Narrow side 103a,b Wide side 104 Cavity 106 ends 107 Contact piece 108 threaded hole 109 hose nipples 111 Hose 200 charging system 201 charging sockets 202 high-voltage battery 203 Coolant outlet 204 connecting piece 206 coolant inlet 207a,b arrows 208 heat exchangers 209 Cooling coil 211 Fan 301 rectangular tube 302 Partition wall 303 Single cavity 304 Arrow

Claims

[1] An electrical busbar designed as a hollow profile (101, 301) through whose cavity (104, 303) a coolant flows, wherein the busbar (100a, b) has an inlet connection and an outlet connection, wherein the inlet connection is designed to allow the flow of a coolant into the cavity (104, 303), wherein the outlet connection is designed to allow the flow of the coolant out of the cavity, wherein contact pieces (107) are integrally and electrically conductively connected to the ends (106) of the busbar or of the hollow profile and tightly close the cavity (104, 303), wherein the cavity (104) is divided into a plurality of individual cavities (303) by partition walls (302), characterized bythat the coolant flows in a first individual cavity (303) in a first flow direction and that the coolant flows in a second individual cavity (303) in a second flow direction which is opposite to the first flow direction. [2] A charging system for a battery-electric power storage device (202), wherein the charging system comprises a terminal (201) connectable to a power source, a power sink (202), a power rail (100a,b) according to the preceding claim, which electrically connects the power source to the power sink, and a heat sink (208,209) through which the coolant flows, wherein the charging system comprises two power rails (100a,b) which are connected to one another at one end by means of a connecting piece (204) in a fluidically and electrically insulated manner, so that the coolant flows out of one power rail (100a) and into the other power rail (100b), wherein the other ends of the two power rails have an inlet connection and an outlet connection, respectively, which are fluidly connected to the heat sink, characterized bythat the two busbars (100a,b) each have two or more individual cavities (303) in which the coolant flows in opposite directions. [3] Charging system according to claim 2, wherein the heat sink is a heat exchanger (208,209), a battery storage (202), an electric machine and / or a device for regulating the temperature in an interior space. [4] Charging system according to claim 3, wherein the heat exchanger is air-cooled.

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