AC-Busbar

Abstract

An AC busbar is proposed, comprising a head area for connection with a first component and a rail area for connection with a second component, wherein the rail area has at least two constrictions at a transition area to the head area, which are arranged at a distance from each other and which connect the rail area to the head area in a web-like manner, wherein a current sensor is arranged at a first constriction.

Description

[0001] The present invention relates to the field of electromobility, in particular to the AC busbars of an electric drive.

[0002] In high-current applications, it is often necessary to measure the current strength at the AC busbars. Busbars or busbars are used to electrically connect two components with one head area being in contact with one component, e.g. an inverter, and one rail area being in contact with the other component, e.g. an electric motor. The current strength is determined, for example, using a shunt measurement or by measuring the magnetic field generated by the alternating current flowing through the AC busbar. Different types of sensors, also known as current sensors, such as Hall sensors, can be used to measure the magnetic field. Currently, such a current sensor is arranged in an area of ​​a constriction (a web) of the busbar between the head area and the rail area, where the current flow is concentrated and can therefore be easily measured.The problem is that reducing the cross-section of the busbar results in increased electrical resistance at the sensor measuring point. Increased electrical resistance leads to increased power loss, which in turn is converted into heat. This leads to an increased temperature at the busbar, which in turn can affect the sensor and other components located near the busbar. This effect is more pronounced at higher currents than at lower currents. Especially in high-current applications such as electric drive systems for vehicles, there is a dilemma between a narrow measuring point and an increased, undesirable temperature.

[0003] Therefore, it is an object of the invention to provide an improved current measurement on AC busbars, in which, in particular, less heating of the AC busbar occurs in the area of ​​the current sensor. This object is achieved by the features of the independent claims. Advantageous embodiments are the subject of the dependent claims.

[0004] An AC busbar is proposed, comprising a head region for connection to a first component and a rail region for connection to a second component, wherein the rail region has at least two constrictions at a transition region to the head region, which constrictions are arranged at a distance from one another and which connect the rail region to the head region in a web-like manner, wherein a current sensor is arranged at a first constriction.

[0005] By using at least one additional constriction at the transition between the head area and the rail area, where no current sensor is provided, the current intensity is distributed among the constrictions. The current range to be measured can be reduced by appropriately designing the additional constriction(s) at the first constriction (the web), where the current sensor is provided, to such an extent that it lies within an optimal measuring range and the power loss—and thus the temperature at the current sensor—reaches an acceptable value.

[0006] In one embodiment, the rail area has two or three constrictions at a transition area to the head area.

[0007] In one embodiment, the at least one additional constriction is designed such that the ratio of the current distribution through the constrictions remains constant over the measuring frequency.

[0008] Furthermore, an inverter with at least one phase and an AC busbar for each phase, as well as an electric drive for a vehicle with at least one electric machine, a transmission device and a multi-phase inverter are provided, wherein the inverter and the electric machine are electrically contacted with the AC busbar for each phase.

[0009] In addition, a motor vehicle with electric drive will be provided.

[0010] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention, with reference to the figures of the drawing, which illustrate details of the invention, and from the claims. The individual features can be implemented individually or in combination in a variant of the invention.

[0011] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. Fig. 1 shows a section of an AC busbar according to the state of the art. Fig. 2 shows a section of an AC busbar according to an embodiment of the present invention. Fig. 3 shows a section of an AC busbar according to another embodiment of the present invention.

[0012] In the following descriptions of the figures, the same elements or functions are provided with the same reference symbols.

[0013] The AC busbar 100 (AC busbar) described below is primarily used in the field of electromobility. Here, it is used in electronic modules, specifically in power electronics, to connect corresponding components for driving the vehicle. Such components are used, for example, for high-current applications and are, for example, a (three-phase) electric motor, i.e., an electric drive, which is to be electrically connected to an inverter, in particular an inverter (DC / AC converter). The inverter converts a direct current, e.g., from a rechargeable battery, into an alternating current that can be used by the electric motor. AC busbars 100 are used to electrically connect the components, with one AC busbar 100 provided for each phase. Of course, the AC busbar 100 can also be used in other applications that do not necessarily have to be high-current applications.

[0014] In Fig. 1 shows a section of an AC busbar 100 according to the prior art. As already mentioned at the beginning, the head region 20 and the rail region 10 of the AC busbar 100 are connected to one another via a web-like constriction 11. The constriction is part of the AC busbar 100, i.e., is formed integrally with it. A current sensor 40 is provided in the region of the constriction 11. This is advantageously arranged as precisely as possible above the constriction 11 in order to measure the magnetic field generated in the region of the constriction 11 due to the flux concentration of the alternating current (AC current). The current sensor 40 transmits the measured data for evaluation to an evaluation unit, e.g., a microcontroller, which calculates the associated current strength from the measured magnetic field. A disadvantage is that, particularly in high-current applications such as in the field of electromobility, a high temperature occurs in the region of the constriction due to the flux concentration, which is undesirable.

[0015] One possible solution to reduce the temperature would be to make the AC Busbar 100 significantly thicker, but this weakens the magnetic field and causes measurement errors, and is not always practical for cost and space reasons, among other things.

[0016] Therefore, another solution is proposed to provide current measurement (using magnetic field measurement) on an AC busbar 100, in which no critical temperature arises due to the current intensity in the area of ​​the current sensor 40. In the proposed solution, at least one further web-like constriction 12, 13 is provided in the transition area between the rail area 10 and the head area 20 (also formed integrally with the AC busbar 100). The current measurement, more precisely the measurement of the magnetic field resulting from the alternating current, from which the current (the current intensity) is calculated, is carried out, as in the prior art, at only one of the constrictions, in the figures at constriction 11. Fig. 2 shows an embodiment in which a total of two constrictions 11 and 12, i.e. an additional constriction 12 to the constriction 11 of the prior art, are provided. In Fig. 3 shows an embodiment in which a total of three constrictions 11, 12 and 13, i.e. two additional constrictions 12 and 13 to the constriction 11 of the prior art, are provided.

[0017] By providing at least one further constriction 12 and / or 13 as a bypass bridge, the current (the current intensity) flowing between the rail region 10 and the head region 20 is divided, so that less heating occurs at the constriction 11, where the current sensor 40 is provided (as in the prior art). In addition, even improved mechanical stability of the AC busbar 100 is achieved.

[0018] By designing the additional constriction(s) 12, 13, i.e., the bypass bridge(s), the current range to be measured by the current sensor 40 can be reduced to such an extent that it lies within the most optimal measuring range possible and the power loss reaches an acceptable value, i.e., the temperature at the current sensor 40 remains within an acceptable range. The additional constriction(s) 12, 13 do not have to be designed such that the currents in the additional constriction(s) 12, 13 and the constriction 11, at which the current is measured, are equal.

[0019] When designing the additional constriction(s) 12, 13, i.e., the dimensions (length, width), spacing, and position, it must be taken into account that a magnetic field is also generated at the additional constriction(s) 12, 13, which can influence (add to or cancel out) the magnetic field at the constriction 11, where the current is measured. Therefore, the additional constriction(s) 12, 13 must be designed in such a way that either the magnetic field of the constriction 11 is not influenced, or the influence is incorporated into the current strength calculation. The influence can be determined through measurements and simulations, and a formula can be generated from this, which is incorporated into the current strength calculation. The influence on the magnetic field of the constriction 11 depends on the design of the constrictions 11-13. The shape and thickness of the AC busbar 100 also influence the generated magnetic field.

[0020] In a preferred embodiment, the ratio of the current distribution at the constrictions 11-13 remains constant throughout the measurement frequency. This can be achieved by optimizing the geometry (length in the y-direction and width in the x-direction) of the constrictions 11, 13 and the distance to the constriction 11. In this case, the calculation of the current intensity from the magnetic field is simplified and thus accelerated, since in the optimal case, only a constant factor of the ratio of the influence of the additional constriction(s) 12, 13 to the constriction 11 at which the current is measured results. This factor can be easily incorporated into the calculation.

[0021] If the current distribution ratio is not constant across the measurement frequency, a more complex relationship may exist between the constrictions 11-13. This influence must be determined based on the design, e.g., through measurements and simulations, and can then be incorporated into the current calculation, e.g., in the form of a formula.

[0022] The AC Busbar 100 is used in a primary application in the field of electromobility. It connects the electric motor and the inverter, i.e., a DC / AC inverter, to supply the alternating current generated by the inverter to the electric motor. The electric motor is used to power the vehicle. In particular, it serves as the axle drive for an electrified axle.

[0023] The described AC busbar 100 can also be used in other applications because it provides improved mechanical stability. This allows the AC busbar 100 to be formed from the smallest possible thickness. List of reference symbols 100 AC busbars 10 Rail area 11 first constriction 12 second constriction 13 third constriction 20 Head area 40 current sensor

Claims

[1] AC busbar (100), comprising a head region (20) for connection to a first component and a rail region (10) for connection to a second component, wherein the rail region (10) has at least two constrictions (11; 12-13) at a transition region to the head region (20), which constrictions are arranged at a distance from one another and which connect the rail region (10) to the head region (20) in a web-like manner, wherein a current sensor (40) is arranged at a first constriction (11). [2] AC busbar (100) according to claim 1, wherein the rail region (10) has two or three constrictions (11-13) at a transition region to the head region (20). [3] AC busbar (100) according to claim 1 or 2, wherein the at least one additional constriction (12, 13) is designed such that the ratio of the current distribution through the constrictions (11-13) is constant over the measuring frequency. [4] Inverter comprising at least one phase and for each phase an AC busbar (100) according to one of the preceding claims. [5] Electric drive for a vehicle with at least one electric machine, a transmission device and a multi-phase inverter, characterized by that the inverter and the electrical machine are electrically contacted with an AC busbar (100) according to one of claims 1 to 3 per phase. [6] Vehicle comprising an electric drive according to claim 5.

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