DE102019212084A1 - Converter for an electrical machine - Google Patents

Abstract

The invention relates to a power converter (100, 101) for an electrical machine. The converter (100, 101) has a housing with a housing frame (10) and a housing cover (11), a phase busbar (1) for contacting a phase winding of the electrical machine, a magnetic flux guide element (2) made of a ferromagnetic material with a back and two Legs, wherein the phase busbar (1) is arranged between the two legs of the magnetic flux guide element (2). The converter (100, 101) also has a Hall element (4), which is arranged between the two legs of the magnetic flux guiding element (2), for detecting a magnetic field that is caused by an electric current flowing through the phase busbar (1 ) flows and it has a circuit carrier (3) on which the Hall element (4) is attached. It is provided that the magnetic flux guide element (2) is at least partially integrated into the housing frame (10) or housing cover (11), the Hall element (4) being arranged between the back of the magnetic flux guide element (2) and the circuit carrier (3) , and / or it is provided that the Hall element (4) is attached to the circuit carrier (3) in such a way that a sensor plane (40) of the Hall element has a distance (d) of 0 mm to 5 mm from one with the free leg ends of the magnetic flux guide element (2) has flush plane (30).

Description

The present invention relates to a power converter for an electrical machine.

State of the art

Electrical machines such as generators or electric motors usually have one or more power converters for converting direct current into alternating current or vice versa. To control the electrical machine, a current measurement of one or more phase currents can be provided, for example on a phase busbar, by means of which a phase winding of the stator is connected to the converter.

A current sensor can be used to measure the current. A suitable current sensor with a magnetic flux guide element made of a ferromagnetic material and a Hall element can be provided. The magnetic flux guiding element has the task of amplifying the magnetic field that is generated by the phase current within the phase busbar and guiding it to the Hall element and at the same time shielding it from magnetic interference. The position of the magnetic flux guide element in relation to the Hall element is decisive for the accuracy of the measurement. The magnetic flux guide element can for example consist of a nickel-iron alloy.

From the DE 10 2012 202 826 A1 Current sensors are known which each enclose a phase of a three-phase electrical system and which are arranged on a circuit board. The current sensors have magnetic flux guide elements for concentrating the magnetic flux surrounding the phase busbars.

There may be a need to improve the accuracy of the current measurement inexpensively by simple means. Furthermore, there may be a need to provide a universally applicable, cost-effective magnetic flux guide element.

Disclosure of the invention

• -- ein Gehäuse mit einem Gehäuserahmen und einem Gehäusedeckel;
• -- eine Phasenstromschiene zur Kontaktierung einer Phasenwicklung der elektrischen Maschine;
• -- ein Magnetflussführungselement aus einem ferromagnetischen Material mit einem Rücken und zwei Schenkeln, wobei die Phasenstromschiene zwischen den zwei Schenkeln des Magnetflussführungselements angeordnet ist;
• -- ein Hall-Element, welches zwischen den zwei Schenkeln des Magnetflussführungselements angeordnet ist, zur Erfassung eines Magnetfelds, welches durch einen elektrischen Strom verursacht ist bzw. wird, der durch die Phasenstromschiene fließt;
• -- einen Schaltungsträger, auf dem das Hall-Element befestigt ist.

According to the invention, a power converter for an electrical machine with the features of the independent claims is proposed.
The converter has:

• - A housing with a housing frame and a housing cover;
• - A phase busbar for contacting a phase winding of the electrical machine;
• a magnetic flux guide element made from a ferromagnetic material with a back and two legs, the phase busbar being arranged between the two legs of the magnetic flux guide element;
• a Hall element, which is arranged between the two legs of the magnetic flux guide element, for detecting a magnetic field which is caused by an electric current which flows through the phase busbar;
• - A circuit carrier on which the Hall element is attached.

According to one aspect of the invention, the magnetic flux guide element is integrated into the housing, that is to say either into the housing frame or into the housing cover.

According to a further aspect of the invention, the Hall element is arranged raised by a circuit carrier carrying it between the legs of the magnetic flux guide element so that a sensor plane of the Hall element is at a distance of 0 mm to 5 mm, preferably at least 1 mm, more preferably at least 2 mm , preferably at most 4 mm, more preferably at most 3 mm, from a plane flush with the free limb ends of the magnetic flux guide element (hereinafter limb end plane), in particular in the direction of the back. Thus, the distance can be measured e.g. from the leg end plane in the direction of the back of the magnetic flux element. This solution is particularly suitable for power converters with ceramic circuit carriers (e.g. "Direct Bonded Copper" circuit carriers (DBC), "Low Temperature Cofired Ceramics" circuit carriers (LTCC)), since there are organic circuit carriers or circuit carriers made of plastic (e.g. circuit boards ("Printed Circuit Board" (PCB))) Feed-through openings for the magnetic flux guide element can only be provided with great effort.

The invention creates advantageous possibilities of defining the relative position of the magnetic flux guide element or its free leg ends and Hall element - especially also in the case of ceramic circuit carriers - very precisely, in order to enable the best possible measurement in this way. In principle, the invention is of course also suitable for organic circuit carriers, such as printed circuit boards, but holes for the magnetic flux guide element can also be drilled there without great effort.

In particular, the sensor is located centrally between the legs of the magnetic flux guide element, which improves the measurement accuracy. Deviations of up to 4 mm from the central Arrangements are possible, but usually undesirable.

The magnetic flux guide element can be designed in a particularly simple manner: it can, for example, only be formed from the back and the two legs protruding substantially perpendicularly from the back. The legs can each have a free end on their side facing away from the back. It can therefore take the form of a "U" or an upside-down "U". The two legs are particularly advantageously designed as simple, straight pieces. The back can e.g. be designed as a flat, straight piece. In cross section, the magnetic flux element can thus be configured like three sides of a rectangle. The magnet guide element can be produced in one piece (e.g. as an injection-molded part or as a cast part or as an element in which the free space remaining between the legs has been cut out). However, it is also conceivable that the magnetic guide element is composed of the individual parts of the back and two legs, e.g. by soldering or welding.

In this way, the magnet guide element is particularly easy to manufacture. There is no need to arrange or design ends at the free ends of the two legs which are respectively stretched towards the other leg. This means that, for example, there is no need to make a narrowly defined slot in a closed ring that has to be produced first. If the legs were to be mounted on the back with opposite ends (so there is no initially closed ring), a test step that checks the tolerance of the resulting slot can be omitted.

The “U” -shaped embodiment has the advantageous effect that when the magnetic flux element is installed above the Hall element, the risk of damage to the Hall element is reduced. This is because the receiving opening for the Hall element is significantly larger compared to a magnet guide element with ends facing each other at the leg ends.

Advantageous configurations are the subject of the subclaims and the description below.

According to an advantageous embodiment, the magnetic flux guide element with the housing frame or the housing cover is at least partially or in sections overmolded. This represents a particularly simple and robust option for integration. Plastics are particularly suitable materials for this, since they also provide electrical insulation.

The housing frame preferably forms a heat sink. In this way, the heat dissipation can be improved. For example, it can comprise copper or aluminum.

In particular, the magnetic flux guide element and the phase busbar are encapsulated together. Alternatively, it is also possible to glue the phase busbar to the housing, in particular to the part of the housing with which the magnetic flux guide element is extrusion coated. The joint encapsulation or gluing of the phase busbar and the magnetic flux guide element enables particularly simple assembly with simultaneous mutual electrical insulation. The phase busbar and the magnetic flux guide element can be brought into a fixed distance from one another by means of the joint extrusion coating or gluing, so that the Hall element can be positioned particularly easily for this purpose.

If the magnetic flux guide element is at least partially integrated into the cover of the housing, the Hall element can be attached to the housing frame - especially together with the circuit carrier carrying it - and the cover with the magnetic flux guide element can be slipped over the Hall element during assembly. However, joint integration of the magnetic flux guide element and Hall element in the housing frame is also conceivable.

The magnetic flux guide element is expediently integrated into the cover in such a way that the two legs of the magnetic flux guide element protrude from the cover and can be slipped over the Hall element during assembly. This is advantageous because simple assembly and good positioning accuracy are ensured in this way.

The distance between the sensor plane of the Hall element and the leg end plane is expediently generated by arranging the Hall element at a distance from a main plane of extent of the circuit substrate. A distance between the sensor plane and a main plane of extent of the circuit carrier is preferably 2 to 6 mm.

The distance between the sensor plane of the Hall element and the leg end plane is expediently provided by a base arranged between the Hall element and circuit carrier. This is a particularly simple and robust way of positioning the Hall element at a fixed distance from the leg end plane of the magnetic flux guide element.

In particular, the Hall element is soldered onto the base. This is a particularly simple and stable connection.

The base is preferably made of copper. As a result, the base can function both as a spacer and as one of the electrical contacts of the Hall element at the same time. Furthermore, there are thermal advantages, since copper has good thermal conductivity and can optimally spread the heat. This has a beneficial effect on the service life of the Hall element and the solder joint.

In another advantageous embodiment, the distance between the sensor plane of the Hall element and the leg end plane is provided by contact pins of the Hall element. This is advantageous since no additional spacer is required and subsequent positioning or alignment is possible through the contact pins.

In particular, a combination of the two aspects of the invention is conceivable. By integrating the magnetic flux guide element into the housing frame or the housing cover in combination with a spaced installation of the Hall element from the leg end plane, particularly precise positioning combined with simple installation can be achieved.
In a further embodiment it is provided that the circuit carrier is a DBC substrate or an LTCC substrate. As a result, the converter can advantageously be designed to be particularly resistant to high temperatures.

In a further embodiment it is provided that the converter has a second circuit carrier on which a logic circuit for evaluating the signals of the Hall element is arranged. In this way, various functionalities of the converter can advantageously be arranged on circuit carriers that are tailored for this purpose. For example, components that are particularly sensitive to shaking or produce particularly high levels of waste heat can be arranged on a particularly stable and heat-resistant circuit carrier, while other components are arranged on a particularly flexible and inexpensive circuit carrier.

In a further embodiment it is provided that the circuit carrier is a DBC substrate and that the second circuit carrier is an LTCC substrate or a PCB substrate.

Further advantages and configurations of the invention emerge from the description and the accompanying drawing.

The invention is illustrated schematically in the drawings using exemplary embodiments and is described below with reference to the drawings.

Figure list

• 1 shows a section of a converter according to a first preferred embodiment of the invention;
• 2 shows a section of a converter according to a second preferred embodiment of the invention;
• 3 shows a section of a converter according to a third preferred embodiment of the invention.

Embodiments of the invention

In 1 is a section of a power converter 100 shown according to a first preferred embodiment of the invention. Converters are used, for example, in electrical machines in order to operate them as motors or generators.

The section shows an example of a mutual arrangement of a phase busbar 1 , a magnetic flux guide element 2 and one on a circuit carrier 3 attached Hall element 4th in such a converter 100 . Such arrangements can be used as current sensors to measure one through the phase busbar 1 current flowing through the Hall element by means of the magnetic field generated by it 4th capture. Typical applications are the detection of the so-called phase currents, ie the currents flowing through the stator windings (so-called phases) of the electrical machine, the stator windings being connected to the phase busbars of the converter.

The magnetic flux guide element is used to guide the magnetic field and shield external magnetic fields 2 made of ferromagnetic, in particular soft magnetic (ie with low coercive force) material, such as an iron-nickel alloy, and has a back and two legs extending from it here essentially perpendicularly. The magnetic guide element 2 thus has the shape of an inverted “U” or (in cross-section) the shape of a rectangle with one side omitted. The two legs each have a free end at their end facing away from the back.

So that the magnetic field detection by the Hall element 4th is as accurate as possible, the Hall element should 4th be arranged centrally between the two legs. The phase busbar should also be preferred 1 arranged centrally between the two legs and from the magnetic flux guide element 2 be electrically isolated. This can all according to a preferred embodiment of Invention can be achieved by the magnetic flux guide element 2 and in the example shown also the phase busbar 1 are encapsulated with part of a housing of the converter. The encapsulation is marked with 7.

The Hall element is used to further improve the detection of magnetic fields 4th in the example shown so on the circuit board 3 attached that a sensor plane 40 of the Hall element 4th a distance d of, for example, about 2 mm from a leg end plane 30th has, wherein the leg end plane is that plane which is flush with the free leg ends of the magnetic flux guide element 2 concludes. The Hall element 4th is for this purpose by means of a copper base 5 from the circuit carrier 3 placed at a distance, i.e. towards the back. The leg end plane 30th in this embodiment coincides with a main plane of extent of the circuit carrier 3 together, but may differ in general.

The circuit carrier 3 a ceramic circuit carrier is preferred here, such as a direct bonded copper substrate (DBC). Due to the combination of the positive properties of the ceramic base material with its high insulation strength and the high electrical conductivity of the copper foils as well as the associated high thermal conductivity, DBC substrates can be used especially in power electronics and for high-current applications and in those applications that are characterized by adverse environmental conditions. Typical applications are modules with IGBT or MOSFET power transistors, which are used, for example, as power modules in railway and automotive electronics or automation technology.

In 2 is a section of another embodiment of a power converter according to the invention 100 shown, however, phase busbar 1 and magnetic flux guide element 2 are not shown. In this embodiment is the sensor plane 40 of the Hall element 4th by means of contact pins 6th at a distance d of about 2 mm from the leg end plane 30th spaced. The circuit carrier 3 , here also designed as a DBC substrate, for example, has corresponding copper contact points for the contact pins 6th on. In this embodiment, the contact pins allow 6th an exact central (re) positioning of the Hall element is advantageous 4th between the legs of the magnetic flux guide element 2 .

3 shows a section of a further embodiment of a power converter according to the invention 101 . In this picture there is also a case from one here as a heat sink 10 formed housing frame and a housing cover 11 pictured. The magnetic flux guide element 2 and the phase busbar 1 are in the housing cover 11 integrated.

The converter has two circuit carriers 3 and 8th on a first circuit carrier 3 for power semiconductors and a second circuit carrier 8th for logic semiconductors that are on the heat sink 10 are arranged or attached.

The first circuit carrier 3 is designed as a DBC substrate, for example. DBC substrates are usually only used for power semiconductors such as MOSFETs, IGBTs, etc. An LTCC substrate (Low Temperature Cofired Ceramics) is usually used for the logic circuit. This has numerous advantages over a conventional printed circuit board (PBC): it is resistant to high temperatures, non-flammable, shake-proof, etc. Semiconductor components can only be applied to an LTCC substrate without packaging. Although this has advantages in terms of packaging (circuit is approx. 8x - 10x smaller), the availability of these components is severely limited and in some cases has to be requested separately.

The invention shows a solution here, such as a packaged component (Hall element 4th ) in a control unit, which is a DBC substrate 3 for power electronics and an LTCC substrate 8th used for the logic, can be integrated particularly easily and precisely.

As in 2 shown is the Hall element 4th through contact pins 6th from the circuit carrier 3 spaced. This figure shows the particular advantage of integrating the magnetic flux guide element 2 and phase busbar 1 in the housing cover 11 recognizable. This can be done with the housing cover 11 via the Hall element 4th be put on. The magnetic flux guide element 2 is electrical with the heat sink 10 connected, in the figure for example by means of a press contact 9 to the magnetic flux guide element 2 to the potential of the heat sink (0V) and thus, for example, to prevent short circuits and interference caused by capacitive coupling with the magnetic flux guide element 2 arise to reduce. In this way, the magnet guide element 2 can also be closed in a ring, which further increases the measurement accuracy. This is advantageously achieved without the Hall element in a complicated assembly step 4th through a narrow slot or gap in the magnet guide element 2 having to thread.

On the second circuit carrier 8th For example, a control circuit can be implemented in the form of an integrated circuit, which a measured Hall voltage across the Hall element 4th evaluates and supplies, for example, a current control.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• DE 102012202826 A1 [0004]

Claims (14)

A converter (100, 101) for an electrical machine, comprising: a housing with a housing frame (10) and a housing cover (11); a phase busbar (1) for making contact with a phase winding of the electrical machine; a magnetic flux guide element (2) made of a ferromagnetic material with a back and two legs, the phase busbar (1) being arranged between the two legs of the magnetic flux guide element (2); a Hall element (4), which is arranged between the two legs of the magnetic flux guide element (2), for detecting a magnetic field which is caused by an electric current which flows through the phase busbar (1); a circuit carrier (3) on which the Hall element (4) is attached; characterized in that the magnetic flux guide element (2) is at least partially integrated into the housing frame (10) or housing cover (11), the Hall element (4) being arranged between the back of the magnetic flux guide element (2) and the circuit carrier (3). Converter (100, 101) according to Claim 1 , wherein the magnetic flux guide element (2) is at least partially encapsulated with the housing frame (10) or the housing cover (11). Converter (100, 101) according to Claim 2 , wherein the magnetic flux guide element (2) and the phase busbar (1) are overmolded together. Converter (100, 101) according to Claim 3 , wherein the magnetic flux guide element (2) and the phase busbar (1) are electrically isolated from one another. Power converter (100, 101) according to one of the preceding claims, wherein the magnetic flux guide element (2) is integrated into the cover (10) in such a way that the two legs of the magnetic flux guide element (2) protrude from the cover (10) and during assembly over the Hall element (4) can be pulled over. Converter (100, 101) according to one of the preceding claims or the preamble of Claim 1 , the Hall element (4) being attached to the circuit carrier (3) in such a way that a sensor plane (40) of the Hall element is at a distance (d) of 0 mm to 5 mm from one with the free leg ends of the magnetic flux guide element (2 ) has a flush plane (30), the distance being determined in particular starting from the plane (30) in the direction of the back of the magnetic guide element (2). Converter (100, 101) according to Claim 6 wherein the distance between the sensor plane of the Hall element (4) and the plane (30) flush with the free leg ends of the magnetic flux guide element (2) is provided by a base (5) arranged between the circuit carrier (3) and the Hall element (4) . Converter (100, 101) according to Claim 7 , the Hall element (4) being soldered onto the base (5). Converter (100, 101) according to Claim 7 or 8th , wherein the base (5) is made of copper. Converter (100, 101) according to Claim 6 wherein the distance between the sensor plane of the Hall element (4) and the plane (30) flush with the free leg ends of the magnetic flux guide element (2) is provided by contact pins (6) of the Hall element (4). Power converter (100, 101) according to one of the preceding claims, wherein the housing frame (10) is designed as a heat sink. Power converter (100, 101) according to one of the preceding claims, wherein the circuit carrier (3) is a DBC substrate or an LTCC substrate. Power converter (100, 101) according to one of the preceding claims, with a second circuit carrier (8) on which a logic circuit for evaluating the signals of the Hall element (4) is arranged. Converter (100, 101) according to Claim 13 , the circuit carrier (3) being a DBC substrate, and the second circuit carrier (8) being an LTCC substrate or a PCB substrate.

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