Device for Determining a Current Flowing Through a Current Conductor, and an Electrical System having such a Device

A device for determining a current flowing through a conductor is disclosed. The device includes a magnetic field sensor unit having at least one first sensor element and a second sensor element, each of which detects a magnetic field strength along a detection direction. The device is designed to determine the current according to the magnetic field strengths detected by way of the first sensor element and the second sensor element. The conductor has a constriction transversely to the longitudinal direction of the conductor, and the magnetic field sensor unit is positioned on the conductor in such a way that the first sensor element is positioned above a first region of the conductor and the second sensor element is positioned above a second region of the conductor, the first region and the second region differing from one another in width due to the constriction. The first sensor element and the second sensor element each use a planar measuring method and each have a detecting device which is parallel to the main extension plane of the conductor, the detecting devices being parallel to one another. An electrical system having such a device is also disclosed.

PRIOR ART

The invention relates to a device for determining a current flowing through a conductor, said device comprising a magnetic field sensor unit having at least one first sensor element and a second sensor element, each of which detects a magnetic field strength along a detection direction, and said device being designed to determine the current according to the magnetic field strengths detected by means of the first sensor element and the second sensor element.

Corresponding devices for determining the current flowing through a conductor are already known to a person skilled in the art. In these devices, the sensor elements are designed as vertical magnetic field sensors and are positioned on opposite sides of the conductor such that the magnetic field can be detected in the vertical direction with respect to the main extension plane. The magnetic field, which is generated in a circular manner around the conductor due to the current flowing through the conductor, in this case acts on the sensor elements in the opposite directions as a result of their corresponding positioning, for example upward in the case of the first sensor element and downward in the case of the second sensor element. By contrast, external interference fields typically act on the two sensors in the same direction, since these interference fields have a certain homogeneity. These stray fields can then be subtracted out by differential evaluation during the actual determination of the current. The difference quotient is in this case understood to be a gradient of the magnetic field.

DISCLOSURE OF THE INVENTION

The invention relates to a device for determining a current flowing through a conductor, said device comprising a magnetic field sensor unit having at least one first sensor element and a second sensor element, each of which detects a magnetic field strength along a detection direction, and said device being designed to determine the current according to the magnetic field strengths detected by means of the first sensor element and the second sensor element.

One aspect of the invention consists in that the conductor has a constriction transversely to the longitudinal direction of the conductor, the magnetic field sensor unit being positioned on the conductor such that the first sensor element is offset parallel to the main extension plane of the conductor and is positioned above a first region of the conductor, and the second sensor element is offset parallel to the main extension plane of the conductor and is positioned above a second region of the conductor, the first region and the second region differing from one another in width transversely to the longitudinal direction due to the constriction, and the first sensor element and the second sensor element each using a planar measurement method and each having a detection direction which is parallel to the main extension plane of the conductor, which detection directions are parallel to one another.

It is advantageous in this case that, as a result of the corresponding positioning of the sensor elements and the design of the conductor, the sensor elements can use a planar measuring method in order to allow a differential evaluation of the magnetic field strengths for determining the current. In this case, the conductor, due to its corresponding design, has a higher current density in the region of the constriction than outside the constriction, as a result of which a corresponding magnetic field gradient is formed in the direction of the main extension plane of the conductor, which magnetic field gradient can be detected by the sensor elements by means of the planar measuring method and can be used for determining the current. As a result, external interference fields can be subtracted out when determining the current.

Compared to the vertical measuring method used in the prior art, the planar measurement method also has the advantage of an improved signal-to-noise ratio, increased accuracy, higher sensitivity and a greater fire width.

The conductor can be designed, for example, as an electrical cable or also as a busbar. If the conductor is round or square, the main extension plane can be defined in any way, taking into account the corresponding geometry. In this case, positioned above a region of the conductor means that the sensor element is positioned at the relevant region so as to be perpendicularly spaced apart from the main extension plane.

The current flowing through this conductor generates a magnetic field which forms around the conductor in a substantially circular manner.

Determining the current is in this case understood to mean that the electrical current intensity is determined, which corresponds to the charge flowing through the conductor.

The longitudinal direction is in this case typically understood to mean the direction along which the current substantially flows.

The sensor elements of the magnetic field sensor can be designed, for example, as a Hall sensor, as an AMR sensor, as a GMR sensor or also as a TMR sensor. It is then possible to infer the current flowing through the conductor according to the detected magnetic field strengths, since this flowing current generates a corresponding magnetic field.

Constriction is understood to mean a recess of the conductor transverse to the longitudinal direction of the conductor, which recess reduces the cross-sectional area of the conductor in the longitudinal direction. Such a reduction in the cross-sectional area in turn results in an increase in the current density in this region.

In one embodiment of the invention, the constriction is designed in a stepped manner such that the conductor additionally has at least one further region having a width transverse to the longitudinal direction that differs from that of the first region and the second region.

It is advantageous in this case that the skin effect in the conductor can be reduced. This in turn results in increased frequency stability when determining the current.

In particular, the further region has a greater width than the first and second region, on which the first sensor element and the second sensor element are positioned, respectively.

In a further embodiment of the invention, the constriction is designed such that a ratio between the maximum and the minimum cross-sectional area of the conductor in the longitudinal direction is less than two.

It is advantageous in this case that the heat loss generated due to the higher current density within the constriction is limited.

According to one embodiment of the invention, the constriction is formed from both sides transversely to the longitudinal direction of the conductor.

It is advantageous in this case that a symmetrical design of the conductor is possible, which improves the measurement tolerances of the devices, in particular the positioning of the magnetic field sensor unit.

According to one embodiment of the invention, the constriction is formed from only one side transversely to the longitudinal direction of the conductor.

It is advantageous in this case that such a one-sided recess can be implemented particularly easily in terms of manufacture, as a result of which cost and time expenditure is optimized during manufacture.

According to one embodiment of the invention, the first sensor element and the second sensor element are oriented such that the relevant detection direction of the first sensor element and of the second sensor element extends in parallel with the longitudinal direction of the conductor.

It is advantageous in this case that a particularly large gradient can be achieved in this direction.

According to one embodiment of the invention, the first sensor element and the second sensor element are oriented such that the relevant detection direction of the first sensor element and of the second sensor element extends transversely to the longitudinal direction of the conductor.

It is advantageous in this case for the magnetic field to also extend in this direction.

The invention also relates to an electrical system having a device according to the invention.

Such an electrical system can be, for example, an electric machine, for example a synchronous machine, having an inverter. In this case, the conductor can be designed, for example, as a phase of the inverter, as a result of which the corresponding phase current which flows through this phase can be measured.

DESCRIPTION OF EMBODIMENTS

FIG.1is a sectional representation of a device for determining a current flowing through a conductor according to the prior art.

A device is shown. The device comprises a magnetic field sensor unit20which is positioned on a conductor100. The magnetic field sensor unit20in turn comprises at least one first sensor element21and a second sensor element22, each of which detects a magnetic field strength along a detection direction25.

Here, the magnetic field sensor unit20is positioned on a conductor100such that the first sensor element21and the second sensor element22are positioned laterally above the main extension plane of the conductor100on opposite sides of the conductor100and each have a detection direction25which is vertical with respect to the main extension plane. The first sensor element21and the second sensor element22correspondingly use a vertical measurement method.

If a current flows in the longitudinal direction102through the conductor100, it generates a magnetic field, the corresponding magnetic field strength being directed upward in the first sensor element21and downward in the second sensor element22.

The device is designed to detect a magnetic field strength in each case by means of the first sensor element21and the second sensor element22and to determine the current which flows through the conductor100according to the magnetic field strengths detected by means of the first sensor element21and the second sensor element22.

FIG.2is a perspective view of a first embodiment of a device according to the invention for determining a current flowing through a conductor.

A device10is shown for determining a current flowing through a conductor100, which device differs from the device according toFIG.1in that the conductor100has a constriction110transversely to the longitudinal direction102of the conductor100. The constriction110is in this case formed from both sides transversely to the longitudinal direction102of the conductor100.

In addition, in contrast to the device according toFIG.1, in the case of the device the magnetic field sensor unit20is positioned on the conductor100such that the first sensor element21is offset parallel to the main extension plane of the conductor100and is positioned above a first region121of the conductor100, and the second sensor element22is offset parallel to the main extension plane of the conductor and is positioned above a second region122of the conductor100, the first region121and the second region122differing from one another in width130transversely to the longitudinal direction102due to the constriction110. Furthermore, the first sensor element21and the second sensor element22each use a planar measurement method and each have a detection direction25which is parallel to the main extension plane of the conductor100, which detection directions are parallel to one another. In this case, the first sensor element21and the second sensor element22are oriented such that the relevant detection direction25of the first sensor element21and of the second sensor element22extends transversely to the longitudinal direction102of the conductor100, with the magnetic field also extending in this direction, which magnetic field is formed by a current flowing in the longitudinal direction102and has a corresponding gradient due to the constriction100with the current density changed thereby within the conductor100.

The constriction110is designed in a stepped manner such that the conductor100additionally has at least one further region123having a width130transverse to the longitudinal direction102that differs from that of the first region121and the second region122.

Furthermore, the constriction110is designed such that a ratio between the maximum and the minimum cross-sectional area of the conductor100in the longitudinal direction102is less than two, i.e., the cross-sectional area of the conductor100is at most halved due to the constriction110.

FIG.3is a perspective view of a second embodiment of a device according to the invention for determining a current flowing through a conductor.

A device11is shown for determining a current flowing through a conductor100, the device11differing from the device10according toFIG.2in that the constriction110is formed from only one side transversely to the longitudinal direction102of the conductor100and is additionally designed with only one step, so that only a first region121and a second region122having mutually different widths130are formed, on which the first sensor element21and the second sensor element22are positioned, respectively.

A further difference from the device10is that in the case of the device11, the first sensor element21and the second sensor element22are oriented such that the relevant detection direction25of the first sensor element21and of the second sensor element22extends in parallel with the longitudinal direction102of the conductor100, in which detection direction a gradient field can also be detected due to the constriction and the corresponding current flow.