DE102013222466A1 - Arrangement for measuring a short-circuit current - Google Patents

Abstract

The invention relates to an arrangement (10) comprising an electrical conductor (12) and a current indicator (13, 14, 15) for measuring a current intensity of a short-circuit current through the electrical conductor, wherein the current indicator (13, 14, 15) comprises a magnetizable material , which detects the current intensity of the short-circuit current, and wherein the current indicator (13, 14, 15) and the electrical conductor (12) are arranged relative to one another such that a magnetic field of the electrical conductor (12) at least the current indicator (13, 14, 15) partially magnetized in the radial direction to a longitudinal axis of the electrical conductor (12). The invention also relates to a battery system (20) having such an arrangement (10) and a vehicle having such a battery system, and to a method for measuring a current intensity of a short-circuit current using such an arrangement (10).

Description

State of the art

The invention relates to an arrangement with an electrical conductor and a current indicator for measuring a current strength of a short-circuit current through the electrical conductor. The invention also relates to a battery system having such an arrangement and to a vehicle having such a battery system and to a method for measuring a current intensity of a short-circuit current using such an arrangement.

The concept of electromobility is becoming increasingly important and is subject to constant further development, especially in the field of battery systems. Thus, the electrical energy is provided for driving vehicles, such as electric or hybrid vehicles, from battery systems that include a plurality of rechargeable battery cells. Especially in the use of such battery systems in vehicles high demands are placed on the security. For example, battery systems have current sensors that can measure the charge and discharge currents that occur and protective circuit devices that break a connection to a vehicle network when a short circuit is detected.

Out DE 101 03 398 A1 is an ammeter known, which measures the electrical current of a current-carrying conductor. For this purpose, a flexible sensor means is provided, which is arranged along the circumference of the conductor and represents a closed circle. To measure the currents, an evaluation of magnetic fields takes place. Furthermore, the sensor means is designed as a magnetoresistive layer around the cylindrical conductor.

EP 2 194 600 B1 describes an integrated circuit protection device for rechargeable batteries, which includes a short-circuit detection device. For this purpose, the short-circuit detection device converts the electrical discharge current into a voltage value, which is compared with a specified voltage value, and detects a short circuit via an equal or greater voltage value of the discharge current. To interrupt the discharging operation of the battery, a discharge control terminal is operated.

DE 197 04 941 A1 describes a mechanical device for detecting short-circuit currents, wherein a bimetallic element is in thermal operative connection with a terminal busbar of a switching device. Due to the heat-related deformation of the bimetal as a result of a short circuit, a strip-shaped display element is actuated.

In battery systems, the detection of electrical currents and in particular short-circuit currents is particularly critical. This is to ensure on the one hand that the circuit is interrupted as quickly as possible. For this purpose, fuse elements between interconnected battery cells and a contactor are used at the main terminals of the battery. As a result of this design, the higher the short-circuit current in the event of a fault, the contactors or the battery cells are damaged to varying degrees and must be replaced with short-circuit currents of more than a few kA. However, the current intensity of the short-circuit current can no longer be determined afterwards. Therefore, for example, the contactor must be replaced as a precautionary measure after every fault.

Disclosure of the invention

According to the invention an arrangement with an electrical conductor and a current indicator for measuring a current strength of a short-circuit current through the electrical conductor is proposed, wherein the current indicator comprises a magnetizable material that detects the current strength of the short-circuit current, and wherein the current indicator and the electrical conductor are arranged to each other in that a magnetic field of the electrical conductor magnetizes the current indicator at least partially in the radial direction to a longitudinal axis of the electrical conductor.

Further according to the invention, a battery system with the arrangement for measuring the current strength of the short-circuit current through the electrical conductor is proposed. In the battery system while electrical conductors may be provided which are equipped with the current indicator. The battery system may further include a battery having a plurality of battery cells, such as lithium-ion battery cells, which is connectable to other components, in particular a consumer, such as an electric motor of a vehicle.

Further according to the invention, a vehicle equipped with the battery system is proposed. In particular, the battery system may be connected to a drive train of the vehicle.

The invention makes it possible to detect the current strength of a short-circuit current in a battery system of a vehicle with very simple means. Thus, conventional current sensors provided in battery systems are designed such that currents in the range of 100 to 800 A can be measured during a driving operation. By the Using the proposed arrangement, higher currents of more than 800 A and in particular more than 1 kA can be detected. In addition, the maximum value of the short-circuit current can be stored and thus provide a basis for decision making, which makes it possible to draw conclusions about the damage to other components of the battery system. As a result, even after the occurrence of a short circuit, reliable statements can still be made as to how strongly the fault has influenced the battery system and its components.

According to the invention, the current indicator in the case of a short circuit to a radial axis to a longitudinal axis of the electrical conductor magnetization, which depends on the current strength of the short-circuit current in the electrical conductor. Thus, the current indicator can detect magnetic fields and detect the current through the radial magnetization. The measurement of the current is thus based on the principle of a current-carrying conductor around which forms a magnetic field as a function of the current whose field strength decreases inversely proportional to the radial distance from the electrical conductor.

In this case, a short-circuit current denotes a current which has a current intensity of more than 800 A, preferably more than 1 kA and particularly preferably between 1 and 10 kA, for example between 2 and 4 kA. The current intensity of the short-circuit current typically depends on several factors. Such factors include, for example, the design of the battery cells, such as lithium-ion battery cells, or the design of components that are connected in the electrical circuit with the battery cells, such as fuse elements, conductors or switching elements.

The current indicator preferably designates an element that detects the maximum current intensity of the short-circuit current that has flowed in the electrical conductor of the battery system. More preferably, the current indicator is designed to store the maximum current intensity of the short-circuit current. For this purpose, the current indicator may comprise a material which, in the case of magnetization, also retains it.

In one embodiment, the current indicator comprises a ferromagnetic and / or a ferrimagnetic material. The current indicator preferably has a soft-magnetic material. Suitable materials include, for example, iron oxide, cobalt, cobalt alloys such as cobalt-nickel alloy or cobalt-iron alloy, chromium alloys, iron alloys such as silicon-iron alloy, soft ferrite such as nickel-zinc alloy or manganese Zinc alloy, or mixtures thereof. Particularly suitable are iron oxide, such as magnetite (iron (II, III) oxide), cobalt, cobalt-nickel alloys, nickel-zinc alloys, manganese-zinc alloys or chromium alloys.

In a further embodiment, the current indicator is rod-shaped or cylindrical. In this case, the current indicator can be arranged such that its longitudinal axis is aligned radially to the longitudinal axis of the electrical conductor. Here, radially to the longitudinal axis of the electrical conductor, each axis, which is aligned perpendicular to the longitudinal axis of the electrical conductor. The electrical conductor may be designed as a conductor cable with different cross-sectional shapes, such as round, elliptical or generally angular. Furthermore, the electrical conductor can be designed as a busbar, for example as a copper rail.

Furthermore, the radial magnetization of the current indicator can indicate the maximum current intensity. Thus, the radial magnetization behaves proportionally to the current across the distance from the electrical conductor. If a small current flows in the range of less than 500 A in the electrical conductor, the current indicator is magnetized in the radial direction to a small distance from the electrical conductor with a lower magnetic field strength. If a current of more than 500 A, preferably more than 1 kA, flows in the electrical conductor, the current indicator is magnetized in the radial direction to a greater distance with a greater magnetic field strength than at 500 A. The radial magnetization of the current indicator is thus a measure of the maximum current intensity of the current flowing in the electrical conductor. In particular, when using ferromagnetic or ferrimagnetic materials, this magnetization is maintained, whereby the current indicator stores the maximum current of the current flowing in the conductor.

In a further embodiment, the current indicator is arranged radially at a distance to the longitudinal axis of the electrical conductor, which is adapted to a maximum current intensity to be detected and thus to the corresponding radial magnetization. Furthermore, the current indicator may have a length which is adapted to the maximum current intensity to be detected and thus to the corresponding radial magnetization. In battery systems, short-circuit currents are, for example, in the range of 1 to 10 kA. Thus, the distance to the electrical conductor and the length of the current indicator can be selected such that the current indicator can detect corresponding radial magnetizations.

In another embodiment, the current indicator is calibrated with respect to the radial magnetization and the current intensity of the short-circuit current. The calibration can be done, for example, by using a reference measurement for predetermined current levels of the current in the electrical conductor, the radial magnetization of the current indicator is measured. For example, the current indicator can be divided into segments with different radial distance from the electrical conductor. The magnetization of the current indicator can be read out for the segments and the values read out for the magnetization can be assigned to a current intensity. Thus, a table (look-up table) can be generated, from which the current can be determined. Alternatively or additionally, threshold values for the magnetization can be determined, by means of which the current intensity can be determined.

To protect the battery system in the event of short circuits, a protective device with at least one securing element can furthermore be provided in the battery system. In a variant, the securing element may comprise a fuse. Such fuses may have a fusible element that has a small thermal mass. This means that the melt melts at currents in the kA range already after a few milliseconds and thus interrupts the electrical connection. At currents in the range of a few 100 A to 1 kA, the fuse may take a second or more to finally break the circuit. Due to the small thermal mass of the melting element, currents in the range of a few kA can be interrupted faster than in the range of a few 100 A to 1 kA. For currents in the kA range, the interruption can occur without any other battery components, such as busbars, heating up. In contrast, some of the heat can be dissipated at currents in the range of a few 100 A to 1 kA across the components of the battery, such as the bus bars. Accordingly, the heat energy that must be introduced to melt the fuse and thus also the current that has a melting result.

In a further variant, the battery system therefore additionally comprises at least one further securing element, which is designed as a contactor for disconnecting the battery from a vehicle network. In this case, a contactor denotes an electromagnetically operated switch, which has two separation points. In addition, a quenching magnet can be arranged in the contactor, which separates an arc in DC applications with limited space.

Furthermore, according to the invention, the use of the arrangement described above in a method for measuring a current intensity of a short-circuit current is proposed.

In one implementation, in the presence of a short circuit, fuse elements that interrupt a battery circuit are activated. Fuseholders or contactors are particularly suitable for this purpose. In another implementation, the current indicator can be evaluated when replacing fuse elements. For example, the current indicator can be removed together with activated fuse elements, in particular fuses, after the presence of a short circuit.

In another implementation, the current indicator is evaluated by detecting the radial magnetization. The evaluation can be carried out with the aid of a read element, such as a Hall probe or a read head based on a magnetoresistance (MR) or a giant magnetoresistance (GMR). In particular, the read element is moved along the current indicator, and the course of the detected magnetization is determined along the radial distance from the electrical conductor. The distance and the radial magnetization characterize the maximum amperage of the short-circuit current.

Based on the maximum current of the short-circuit current, the functionality of components of the battery system can be determined. Thus, in particular contactors or battery cells may have been affected by the short circuit. The assessment of such components can be made by comparing the maximum current of the short-circuit current with a maximum allowed for the corresponding component current. If the maximum current strength of the current flowing in the conductor is greater than the maximum permitted current for the corresponding component or equal to the maximum permitted current for the corresponding component, then the component is no longer functional and must be replaced. Conversely, the component is functional and can be retained.

Advantages of the invention

Overall, the proposed arrangement provides a cost effective and easy way to detect short circuit currents in battery systems and to store the magnitude of the current. This makes it possible to make a confident statement about whether components have been affected and to what extent they need to be replaced. This results in significant cost savings, since not precautionary components, such as the contactors of the battery system must be replaced after each short circuit.

Brief description of the drawings

Embodiments of the invention are illustrated in the figures and are explained in more detail in the following description.

Show it:

1 an embodiment of an arrangement for measuring a current intensity of a short-circuit current with an electrical conductor and a current indicator,

2 a battery system with the arrangement according to 1 and

3 a flow of a method for measuring a current of a short-circuit current using the arrangement according to 1 in the form of a flow chart.

In the following description of the embodiments of the invention, the same or similar components and elements are denoted by the same or similar reference numerals, wherein a repeated description of these components or elements is dispensed with in individual cases. The figures illustrate the subject matter of the invention only schematically.

Embodiments of the invention

1 shows an arrangement 10 with an electrical conductor 12 and a current indicator 14 for measuring a current intensity of a short-circuit current through the electrical conductor 12 ,

The order 10 includes such an electrical conductor 12 in the form of a high-current cable with a round cross-section 16 , Through the electrical conductor 12 a current flows in the representation of the 1 indicated by the cross 11 flows into the picture plane. Due to the moving charge in the electrical conductor 12 a magnetic field forms around the electrical conductor 12 , The magnetic field is in 1 using magnetic field lines 18 illustrated. The field strength is along a circular field line 18 around the electrical conductor 12 constant.

Due to the flow of current in the electrical conductor 12 will be outside the electrical conductor 12 induces a magnetic field whose field strength depends on the current in the electrical conductor 12 flowing current and the distance r to the electrical conductor 12 depends. The electricity indicator 14 comprises a magnetizable material, such as a ferromagnetic or a ferrimagnetic and in particular a soft magnetic material. For example, the electricity indicator 14 made of an iron oxide. Furthermore, the electricity indicator 14 rod-shaped with the length L and radially at a distance ΔD to the electrical conductor 12 arranged. Dependent on the magnetic field strength outside of the electrical conductor 12 becomes the electricity indicator 14 thus magnetized in the radial direction, wherein the magnetic field strength in turn of the current strength of the electrical conductor 12 flowing current and the distance r to the electrical conductor 12 depends.

That by the electrical conductor 12 generated magnetic field magnetizes with it the current indicator 14 radially with a radial magnetization at a distance r. The distance r of the radial magnetization results from the sum of the radius D of the electrical conductor 12 , the distance ΔD of the current indicator 14 to the electrical conductor 12 and the radial distance ΔR of the magnetization of the current indicator 14 in the distance r. With the help of a calibration, the radial magnetization at a distance r is a current of the in the electrical conductor 12 flowing current can, from the radial magnetization of the current indicator 14 at a distance r, the current in the electrical conductor 12 be determined. Thus, the current indicator shows 14 the maximum current in the electrical conductor 12 flowed on.

The electricity indicator 14 does not provide a snapshot of the current in the electrical conductor 12 flowing current, but rather the maximum current in the electrical conductor 12 flow, by means of which at least the magnitude of a short-circuit current of more than 1 kA can be specified. The maximum current in the electrical conductor 12 Flowed current corresponds in the case of a short circuit of the maximum current of the short-circuit current. Thus, after an error, which has led to a short circuit, the occurred overcurrent can be evaluated. In particular, it can be determined whether the short-circuit current has exceeded a current, in addition to, for example, fuse elements 26 . 28 other components of a battery system 20 with battery cells 22 , as in 2 shown, has affected. Based on this information, it can be reliably and safely decided which components need to be replaced. Thus, the repair can be carried out efficiently and inexpensively after a fault.

2 shows an example of a battery system 20 with security elements 26 . 28 and orders 10 according to 1 ,

The battery system 20 is in 2 schematically using a circuit diagram of the high-voltage circuit (HV) for battery cells 22 shown. There are several battery cells 22 connected in series and form, for example, a battery module 24 ,

To interrupt the circuit in the event of a short circuit in the battery system 20 are security elements 26 . 28 intended. One of the security elements shown 26 . 28 is between at least one pair of battery cells 22 interconnected and is as a fuse 26 designed. The fuse 26 has a small thermal mass. That is, at high currents, for example at 6 kA, releases the fuse 26 after just a few milliseconds. At lower currents, for example, at 500 A, the fuse 26 take up to a second to trigger. Due to the small thermal mass of the fuse 26 High short-circuit currents are interrupted very quickly, without any other battery components, such as busbars or high-current cables, heating up. At lower short-circuit currents, part of the heat from the fuse becomes 26 derived from other battery components. Thus, more heat energy must be introduced to melt the fuses by a higher current. In addition, the battery system includes 20 a contactor 28 , which is operated as an electromechanical switch. Responds to the fuse 26 not fast enough, the connection to a vehicle network is through the contactors 28 interrupted.

Usually, battery systems include 20 Current measuring devices (not shown), such as Hall current sensors, shunt sensors or the like, which can detect the presence of a short-circuit current, but can not measure the currents. Thus, the current intensity of the short-circuit current, for example, a current greater than 1kA or more than 2kA, until the triggering of the fuse elements 26 . 28 flows, not detected or only during the rise phase of the short-circuit current. The current value of the short-circuit current is unknown.

To be able to measure such high currents as short-circuit currents in the range of a few kA, the battery system includes 20 arrangements 10 to measure the current with the current indicator 13 . 14 . 15 , In the embodiment of 1 are two electricity indicators 13 . 14 . 15 in different positions of the battery system 20 arranged. The electricity indicators 13 . 14 . 15 are made of a magnetizable material and, like in 1 shown radially to a longitudinal axis of the electrical conductor 12 of the battery system 20 arranged. The first electricity indicator 13 . 14 is radial to the longitudinal axis of the electrical conductor 12 arranged, which is the contactor 28 is downstream. The second electricity indicator 14 . 15 is radial to the longitudinal axis of the electrical conductor 12 arranged, one of the battery cells 22 upstream. The electricity indicators 13 . 14 . 15 measure the current through the electrical conductor 12 flowing current in the immediate vicinity of the contactors 28 and the battery cells 22 , So can the electricity indicators 13 . 14 . 15 in the case of a short circuit serve the current strength of the flowed short-circuit current in the contactor 28 and in the area of the battery cells 22 to investigate.

The current value of the short-circuit current is determined by evaluation of the current indicators 13 . 14 . 15 determined. After the fuse 26 has triggered because of a short circuit, it must be changed. During a visit to the workshop electricity indicators can be used 13 . 14 . 15 also be expanded and evaluated. Thus, in particular by the measurement of the radial magnetization at a distance r to the maximum current intensity in the electrical conductor 12 flow closed. Based on this evaluation, a statement can then be made as to what the components of the battery system 20 So the battery cells 22 and the contactors 28 were short circuit affected. Depending on whether the maximum amperage of the electrical conductor 12 flowed a maximum for the components of the battery system 20 If the rated current reaches or exceeds the permitted current, the corresponding component can also be replaced.

3 shows a flow of a method for measuring the current strength of a short-circuit current using the arrangement 10 according to 1 in the form of a flow chart.

To measure the amperage of the short-circuit current in the battery system 20 , such as in 2 is shown in a first step 100 the electricity indicator 13 . 14 . 15 provided and radial to a longitudinal axis of an electrical conductor 12 of the battery system 20 arranged.

In a second step 102 captures the electricity indicator 13 . 14 . 15 in case of a short circuit, the maximum current of the short-circuit current.

In a third step 104 becomes the electricity indicator 13 . 14 . 15 evaluated to determine the maximum amperage of the short-circuit current. For this purpose, the radial magnetization at a distance r of the current indicator 13 . 14 . 15 read out using for example a Hall probe. In particular, the magnetization is measured as a function of the radial distance r. From this, with the help of a calibration, the maximum current in the electrical conductor 12 flow are determined.

In a fourth step 106 is the maximum amperage of the short-circuit current with a maximum allowed amperage for the individual components of the battery system 20 compared. Reaches or exceeds the maximum current in the electrical conductor 12 current flow the maximum permitted current for one of the components of the battery system 20 , so this component is replaced. On the basis of the determined maximum current strength of the short-circuit current thus a reliable and reliable statement can be made as to whether battery components, such as battery cells 22 short-circuited and need to be replaced.

The invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, within the scope indicated by the appended claims, a variety of modifications are possible which are within the purview of the skilled artisan.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10103398 A1 [0003]
• EP 2194600 B1 [0004]
• DE 19704941 A1 [0005]

Claims (10)

Arrangement ( 10 ) with an electrical conductor ( 12 ) and a current indicator ( 13 . 14 . 15 ) for measuring a current intensity of a short-circuit current through the electrical conductor ( 12 ), characterized in that the current indicator ( 13 . 14 . 15 ) has a magnetizable material that detects the current strength of the short-circuit current, and wherein the current indicator ( 13 . 14 . 15 ) and the electrical conductor ( 12 ) are arranged to each other such that a magnetic field of the electrical conductor ( 12 ) the current indicator ( 13 . 14 . 15 ) at least partially in the radial direction to a longitudinal axis of the electrical conductor ( 12 ) magnetized. Arrangement ( 10 ) according to claim 1, characterized in that the current indicator ( 13 . 14 . 15 ) is configured to store a maximum current of the short-circuit current. Arrangement ( 10 ) according to claim 1 or 2, characterized in that the current indicator ( 13 . 14 . 15 ) comprises a ferromagnetic and / or a ferrimagnetic material. Arrangement ( 10 ) according to one of claims 1 to 3, characterized in that the current indicator ( 13 . 14 . 15 ) is rod-shaped, wherein the current indicator ( 13 . 14 . 15 ) is arranged such that its longitudinal axis is radial to the longitudinal axis of the electrical conductor ( 12 ) is aligned. Arrangement ( 10 ) according to one of claims 1 to 4, characterized in that the current indicator ( 13 . 14 . 15 ) radially at a distance (ΔD) to the longitudinal axis of the electrical conductor ( 12 ) is arranged and has a length (L) which is adapted to a maximum current to be detected. Arrangement ( 10 ) according to one of claims 1 to 5, characterized in that the current indicator ( 13 . 14 . 15 ) with respect to a radial magnetization of the current indicator ( 13 . 14 . 15 ) and the current strength of the short-circuit current is calibrated. Battery system ( 20 ) with at least one arrangement ( 10 ) according to one of claims 1 to 6. Battery system ( 20 ) according to claim 7, characterized in that the battery system ( 20 ) at least one security element ( 26 . 28 ) in the event of a short circuit. Vehicle equipped with a battery system ( 20 ) according to claim 7 or 8. Method for measuring a short-circuit current in a battery system ( 20 ) using the arrangement ( 10 ) according to one of claims 1 to 6.

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