Rectifier for an electric motor

Abstract

The present invention relates to a rectifier for an electric motor. The rectifier has a housing with a housing frame and a housing cover, a phase current busbar for contacting the phase windings of the electric motor, a magnetic flux guiding element made of ferromagnetic material having a back and two arms, wherein the phase current busbar is arranged between the two arms of the magnetic flux guiding element. In addition, the rectifier has a Hall element, which is arranged between the two arms of the magnetic flux guiding element, the Hall element is used to detect the magnetic field caused by the current flowing through the phase current busbar, and the rectifier has a circuit base, and the Hall element is fixed on the circuit base. It is hereby stipulated that the magnetic flux guiding element is at least partially integrated into the housing frame or the housing cover.

Description

Technical Field

[0001] The present invention relates to a rectifier for an electric machine. Background Art

[0002] An electric machine, such as a generator or an electric motor, usually has one or more rectifiers for converting direct current into alternating current or vice versa. In order to control the electric machine, it is possible to provide current measurement of one or several phase currents, for example, on a phase current busbar, by means of which the phase windings of the stator are connected to the rectifier.

[0003] For current measurement, current sensors can be used. Current sensors can be provided that are suitable and have a magnetic flux guiding element made of ferromagnetic material and a Hall element. The task of the magnetic flux guiding element is to enhance the magnetic field generated by the internal phase current passing through the phase current busbar, guide it to the Hall element, and at the same time shield the Hall element from magnetic interference. The position of the magnetic flux guiding element relative to the Hall element is decisive for the measurement accuracy. The magnetic flux guiding element can be made of, for example, permalloy.

[0004] Current sensors are known from DE 102012202826 A, which each enclose a phase of a three-phase electrical system and are arranged on a circuit board. The current sensors have a magnetic flux guiding element for concentrating the magnetic flux surrounding the phase current busbar.

[0005] There may be a need to improve the accuracy of current measurement inexpensively with simple means. In addition, there may be a need to provide a universal and inexpensive magnetic flux guiding element. Summary of the Invention

[0006] According to the present invention, a rectifier for an electric machine as described herein is proposed. The rectifier has:

[0007] - a housing with a housing frame and a housing cover;

[0008] - a phase current busbar for contacting the phase windings of the electric machine;

[0009] - a magnetic flux guiding element made of ferromagnetic material having a back and two arms, wherein the phase current busbar is arranged between the two arms of the magnetic flux guiding element;

[0010] - a Hall element arranged between the two arms of the magnetic flux guiding element for detecting the magnetic field caused by the current flowing through the phase current busbar;

[0011] - a circuit base on which the Hall element is fixed.

[0012] Wherein the magnetic flux guiding element is at least partially integrated into the housing frame or the housing cover, and wherein the Hall element is arranged between the back of the magnetic flux guiding element and the circuit base.

[0013] Or,

[0014] Wherein the Hall element is fixed to the circuit base such that the sensor plane of the Hall element has a spacing of 0 mm to 5 mm from the plane flush with the free arm end of the magnetic flux guiding element, and wherein the spacing is determined in the direction towards the back of the magnetic flux guiding element.

[0015] According to one aspect of the invention, the magnetic flux guiding element is integrated into the housing, that is, either integrated into the housing frame or integrated into the housing cover.

[0016] According to another aspect of the invention, the Hall element is arranged between the arms of the magnetic flux guiding element when raised from the circuit base that supports it, such that the sensor plane of the Hall element has a spacing 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 the plane flush with the free arm ends of the magnetic flux guiding element (hereinafter referred to as the arm end plane), especially in the direction towards the back. Thereby, the spacing, for example, in the direction from the arm end plane towards the back of the magnetic flux element can be measured. This solution is particularly suitable for rectifiers having a ceramic circuit base (such as a "Directed Bonded Copper" - circuit base (DBC), a "Low Temperature Cofired Ceramics" - circuit base (LTCC)), because different from an organic circuit base or a circuit base made of plastic (such as a "Printed Circuit Board" (PCB), a printed circuit), where it is only possible to provide through-holes for the magnetic flux guiding element at a very high cost.

[0017] The invention provides advantageous solutions for very precisely determining the relative positions of the magnetic flux guiding element or its free arm ends and the Hall element - especially also for ceramic circuit bases - so that the best possible measurements can be made in this way. In principle, the invention is of course also suitable for organic circuit bases, such as printed circuit boards, but where it is also possible to drill holes for the magnetic flux guiding element without great expense.

[0018] The sensor is particularly centered between the arms of the magnetic flux guiding element, which improves the measurement accuracy. Deviations of less than 4 mm from the centered arrangement are possible, but are generally not desirable.

[0019] The magnetic flux guiding element can in particular be easily configured here: It can for example consist only of the back and two arms extending essentially perpendicularly from the back. The arms can each have a free end on the side facing away from the back. Thereby, it can have the shape of a "U" or an inverted "U". Particularly advantageously, the two arms are configured as simple, straight blocks. The back can for example be configured as a flat, straight block. In cross-section, the magnetic element can thus be configured like three sides of a rectangle. The magnetic flux guiding element can be made integrally (for example as an injection molding or as a casting or as an element for which the free space remaining between the arms has already been cut out). However, it can also be considered that the magnetic guiding element is composed of the back and the two arms as individual parts, for example by brazing or welding.

[0020] In this way, the magnetic flux guiding element can be made particularly easily. The necessity of arranging or configuring ends extending respectively in the opposite direction to the other arm at the free ends of the two arms is eliminated. Thereby, for example, the addition of a narrowly defined gap to a closed loop that should be manufactured first can be dispensed with. If the arms are mounted on the back with ends extending in opposite directions to each other (that is, there is thus no initially closed loop), the step of checking the tolerance of the resulting gap can be eliminated.

[0021] This is advantageously achieved by an embodiment in the form of a "U" in that the risk of damage to the Hall element is reduced when the magnetic flux element is mounted on the Hall element. Because the receiving opening for the Hall element is significantly larger compared to the magnetic guiding element with ends facing each other at the arm ends.

[0022] Advantageous designs are the subject of the following.

[0023] According to an advantageous embodiment, the magnetic flux guiding element with a housing frame or a housing cover is at least partially or segmentally extrusion-encapsulated. This represents a particularly simple and durable integration solution. As a material, in particular plastic is suitable for this, because the plastic simultaneously provides electrical insulation.

[0024] Preferably, the housing frame forms a heat sink. In this way, heat dissipation can be improved. The housing frame can for example be made of copper or aluminum.

[0025] In particular, the magnetic flux guiding element and the phase current busbar are jointly extrusion - encapsulated. As an alternative, it is also possible to bond the phase current busbar to the housing, in particular to the following components of the housing, with which the magnetic flux guiding element is extrusion - encapsulated. Through the joint extrusion - encapsulation or bonding of the phase current busbar and the magnetic flux guiding element, particularly easy assembly can be carried out while achieving mutual electrical insulation. The phase current busbar and the magnetic flux guiding element can be placed at a fixed distance relative to each other through joint extrusion - encapsulation or bonding, so that the Hall element can be particularly easily positioned relative to them.

[0026] If the magnetic flux guiding element is at least partially integrated into the cover of the housing, then the Hall element - particularly together with the circuit board on which it is carried - can be fixed to the housing frame and the cover can be placed over the Hall element together with the magnetic flux guiding element during assembly. However, it is also possible to consider integrating the magnetic flux guiding element and the Hall element together into the housing frame.

[0027] The magnetic flux guiding element can be suitably integrated into the cover such that two arms of the magnetic flux guiding element extend out of the cover and can be placed over the Hall element during assembly. This is advantageous because in this way easy assembly and good positioning accuracy are ensured.

[0028] The distance of the sensor plane of the Hall element from the end - plane of the arm is suitably produced by the spaced - apart arrangement of the Hall element from the main extension plane of the circuit board. The distance of the sensor plane relative to the main extension plane of the circuit board is preferably 2 to 6 mm.

[0029] The distance of the sensor plane of the Hall element from the end - plane of the arm is suitably provided by a base arranged between the Hall element and the circuit board. This is a particularly simple and durable solution to position the Hall element at a prescribed distance relative to the end - plane of the arm of the magnetic flux guiding element.

[0030] In particular, the Hall element is soldered to the base. This represents a particularly simple and stable connection.

[0031] Preferably, the base is made of copper. Thereby, the base can not only act as a spacer at the same time but also act as one of the electrical contacts of the Hall element. In addition, thermal advantages are produced because copper has good thermal conductivity and can dissipate heat optimally. This advantageously affects the service life of the Hall element and the soldering points.

[0032] In another advantageous embodiment, the spacing of the sensor plane of the Hall element from the end plane of the arm is provided by the legs of the Hall element. This is advantageous because no additional spacer is required and subsequent positioning or orientation can be carried out via the legs.

[0033] In particular, a combination of two aspects of the invention can be considered. By integrating the magnetic flux guiding element into the housing frame or the housing cover and combining the Hall element with the spaced-apart assembly from the end plane of the arm, particularly precise positioning can be achieved together with easy assembly.

[0034] In another embodiment, it is provided that the circuit base is a DBC substrate or an LTCC substrate. Thereby, the rectifier can advantageously be configured to be particularly resistant to high temperatures.

[0035] In another embodiment, it is provided that the rectifier has a second circuit base on which logic circuits for evaluating the signals of the Hall element are arranged. In this way, the different functions of the rectifier can advantageously be arranged on circuit bases that are dimensionally customized for this purpose. Thus, for example, structural elements that are particularly sensitive to vibration or generate particularly high waste heat can be arranged on particularly stable and heat-resistant circuit bases, while other structural elements can be arranged on particularly flexible and cost-effective circuit bases.

[0036] In another embodiment, it is provided that the circuit base is a DBC base and the second circuit base is an LTCC substrate or a PCB substrate.

[0037] Further advantages and design options of the invention result from the description and the drawings. Description of the Drawings

[0038] The invention is schematically illustrated in the drawings by way of examples and is described below with reference to the drawings:

[0039] Figure 1 A cut-away portion of a rectifier according to a first preferred embodiment of the invention is shown;

[0040] Figure 2 A cut-away portion of a rectifier according to a second preferred embodiment of the invention is shown;

[0041] Figure 3 A cut-away portion of a rectifier according to a third preferred embodiment of the invention is shown. Detailed Description of the Embodiment

[0042] In Figure 1A cut-away portion of a rectifier 100 according to a first preferred embodiment of the present invention is shown. The rectifier is used, for example, in an electric machine for operating the electric machine in motor mode or in generator mode.

[0043] The cut-away portion shows an exemplary relative arrangement of a phase current busbar 1, a magnetic flux guiding element 2, and a Hall element 4 fixed to a circuit base 3 in such a rectifier 100. Such an arrangement can be used as a current sensor for detecting the current flowing through the phase current busbar 1 by means of the magnetic field generated by the current via the Hall element 4. A typical application scenario is the detection of so-called phase currents, i.e., the currents flowing through the stator windings (so-called phases) of the electric machine, where the stator windings are connected to the phase current busbars of the rectifier.

[0044] In order to guide the magnetic field and shield external magnetic fields, the magnetic flux guiding element 2 is made of a ferromagnetic, especially soft magnetic (i.e., having a small coercive force) material, such as permalloy, and has a back and two arms extending substantially perpendicularly therefrom. Thus, the magnetic flux guiding element 2 here exemplarily has an inverted "U" shape or (in cross-section) a rectangular shape with one side omitted. The two arms each have a free end at their end facing away from the back.

[0045] In order to make the magnetic field detection by the Hall element 4 as precise as possible, the Hall element 4 should be able to be arranged centrally between the two arms. Preferably, the phase current busbar 1 should also be arranged centrally between the two arms and be electrically insulated from the magnetic flux guiding element 2. All the advantages of a preferred embodiment according to the present invention can be achieved by the fact that the magnetic flux guiding element 2 and also the phase current busbar 1 in the shown embodiment are also extrusion-encapsulated by a part of the rectifier housing. The extrusion-encapsulation is denoted by 7.

[0046] In order to further improve the magnetic field detection, the Hall element 4 in the shown embodiment is fixed to the circuit base 3 such that the sensor plane 40 of the Hall element 4 has a spacing d of, for example, approximately 2 mm from the arm end plane 30, where the arm end plane is a plane terminating flush with the free arm ends of the magnetic flux guiding element 2. The Hall element 4 is placed spaced apart from the circuit base 3, i.e., in the direction towards the back, by means of a copper base 5. In this embodiment, the arm end plane 30 coincides with the main extension plane of the circuit base 3, but can generally be different from the latter.

[0047] The circuit base 3 is preferably a ceramic circuit base here, such as a "Direct Bonded Copper" substrate (DBC). Through the combination of the positive characteristics of the ceramic substrate, its high insulation strength, the high conductivity of the copper foil, and the resulting high thermal conductivity, the DBC substrate is specifically suitable for use in power electronics and for high-current applications and in applications with contradictory environmental conditions. Typical applications are modules with IGBTs or MOSFET power transistors, which are used, for example, as power modules in rail and automotive electronics or automation technology.

[0048] In Figure 2 a partial cutout of another embodiment of the rectifier 100 according to the invention is shown, but the phase current busbar 1 and the magnetic flux guiding element 2 are not shown. In this embodiment, the sensor plane 40 of the Hall element 4 is spaced from the arm end plane 30 by a distance d of approximately 2 mm by means of the pins 6. Here, the circuit base 3, which is also constructed as a DBC substrate, for example, has corresponding copper contact points for the pins 6. In this embodiment, the pins 6 can advantageously (re)position the Hall element 4 precisely centered between the arms of the magnetic flux guiding element 2.

[0049] Figure 3 A partial cutout of another embodiment of the rectifier 101 according to the invention is shown. In this illustration, the housing consisting of the housing frame and the housing cover 11, which is constructed as a heat sink 10 here, is also shown. The magnetic flux guiding element 2 and the phase current busbar 1 are integrated into the housing cover 11 here.

[0050] The rectifier has two circuit bases 3 and 8, a first circuit base 3 for power semiconductors and a second circuit base 8 for logic semiconductors, which are arranged or fixed on the heat sink 10.

[0051] The first circuit base 3 is constructed as a DBC substrate, for example. DBC substrates are generally only used for power semiconductors, such as MOSFETs, IGBTs, etc. For logic circuits, LTCC substrates (Low Temperature Cofired Ceramics) are generally used. This substrate has a number of advantages over traditional circuit boards (PBCs): it is heat-resistant, non-combustible, vibration-resistant, etc. Semiconductor structural elements can only be applied to the LTCC substrate in an unpackaged state. This has advantages in terms of packaging (the circuit is, for example, 8x - 10x smaller), but the availability of these structural elements is greatly restricted and must be requested partially separately.

[0052] The present invention describes here a solution on how the packaged structural element (Hall element 4) can be integrated particularly easily and precisely into a controller that uses a DBC substrate 3 for power electronics and an LTCC substrate 8 for logic circuitry.

[0053] Also as shown in Figure 2 , the Hall element 4 is spaced apart from the circuit base 3 by the pins 6. In this illustration, it can be particularly seen the advantage of integrating the magnetic flux guiding element 2 and the phase current busbar 1 into the housing cover 11. The magnetic flux guiding element and the phase current busbar can be covered onto the Hall element 4 with the housing cover 11. The magnetic flux guiding element 2 is electrically connected to the heat sink 10 in the drawing, for example, by means of a press contact 9, in order to pull the magnetic flux guiding element 2 to the potential (0 V) of the heat sink and thus, for example, prevent short circuits and reduce interference generated by capacitive coupling with the magnetic flux guiding element 2. In this way, the magnetic flux guiding element 2 can also be closed in a ring shape, thereby further improving the measurement accuracy. This is advantageously achieved without having to thread the Hall element 4 through narrow slits or gaps in the magnetic flux guiding element 2 in complex assembly steps.

[0054] On the second circuit base 8, a control circuit in the form of an integrated circuit can be implemented, which evaluates the measured Hall voltage on the Hall element 4 and, for example, feeds it to a current regulating mechanism.

Claims

1. A rectifier (100, 101) for an electric motor, the rectifier having the following components: A housing with a housing frame (10) and a housing cover (11); A phase current busbar (1) for contacting the phase windings of the electric motor; A magnetic flux guiding element (2) made of ferromagnetic material and having a back and two arms, wherein the phase current busbar (1) is arranged between the two arms of the magnetic flux guiding element (2); A Hall element (4) arranged between the two arms of the magnetic flux guiding element (2), the Hall element being used to detect the magnetic field caused by the current flowing through the phase current busbar (1); A circuit base (3) on which the Hall element (4) is fixed, Characterized in that The magnetic flux guiding element (2) is at least partially integrated into the housing frame (10) or the housing cover (11), wherein the Hall element (4) is arranged between the back of the magnetic flux guiding element (2) and the circuit base (3).

2. The rectifier (100, 101) according to claim 1, wherein the magnetic flux guiding element (2) is at least partially encapsulated by the housing frame (10) or the housing cover (11).

3. The rectifier (100, 101) according to claim 2, wherein the magnetic flux guiding element (2) and the phase current busbar (1) are jointly encapsulated.

4. The rectifier (100, 101) according to claim 3, wherein the magnetic flux guiding element (2) and the phase current busbar (1) are electrically insulated from each other.

5. The rectifier (100, 101) according to any one of claims 1 to 4, wherein the magnetic flux guiding element (2) is integrated into the housing cover (11) such that the two arms of the magnetic flux guiding element (2) protrude from the housing cover (11) and can cover the Hall element (4) during assembly.

6. The rectifier (100, 101) according to any one of claims 1 to 4, wherein the Hall element (4) is fixed on the circuit base (3) such that the sensor plane (40) of the Hall element is spaced 0 mm to 5 mm from the plane (30) flush with the free arm ends of the magnetic flux guiding element (2), wherein the spacing is determined in the direction towards the back of the magnetic flux guiding element (2).

7. The rectifier (100, 101) according to claim 6, wherein the spacing of the sensor plane of the Hall element (4) from the plane (30) flush with the free arm ends of the magnetic flux guiding element (2) is provided by a base (5) arranged between the circuit base (3) and the Hall element (4).

8. The rectifier (100, 101) according to claim 7, wherein the Hall element (4) is soldered to the base (5).

9. The rectifier (100, 101) according to claim 7, wherein the base (5) is made of copper.

10. The rectifier (100, 101) according to claim 6, wherein the spacing of the sensor plane of the Hall element (4) from the plane (30) flush with the free arm end of the magnetic flux guiding element (2) is provided by the legs (6) of the Hall element (4).

11. The rectifier (100, 101) according to any one of claims 1 to 4, wherein the housing frame (10) is configured as a heat sink.

12. The rectifier (100, 101) according to any one of claims 1 to 4, wherein the circuit substrate (3) is a DBC substrate or an LTCC substrate.

13. The rectifier (100, 101) according to any one of claims 1 to 4, having a second circuit substrate (8) on which logic circuitry for evaluating the signals of the Hall element (4) is arranged.

14. The rectifier (100, 101) according to claim 13, wherein the circuit substrate (3) is a DBC substrate and the second circuit substrate (8) is an LTCC substrate or a PCB substrate.

15. The rectifier (100, 101) according to claim 6, wherein the spacing is determined in the direction towards the back of the magnetic flux guiding element (2) starting from the plane (30).

16. A rectifier (100, 101) for an electric motor, the rectifier having the following components: A housing with a housing frame (10) and a housing cover (11); A phase current busbar (1) for contacting the phase windings of the electric motor; A magnetic flux guiding element (2) made of ferromagnetic material having a back and two arms, wherein the phase current busbar (1) is arranged between the two arms of the magnetic flux guiding element (2); A Hall element (4) arranged between the two arms of the magnetic flux guiding element (2), the Hall element for detecting the magnetic field caused by the current flowing through the phase current busbar (1); A circuit substrate (3) on which the Hall element (4) is fixed, characterized in that the Hall element (4) is fixed on the circuit substrate (3) such that the sensor plane (40) of the Hall element has a spacing (d) of 0 mm to 5 mm from the plane (30) flush with the free arm end of the magnetic flux guiding element (2), wherein the spacing is determined in the direction towards the back of the magnetic flux guiding element (2).

17. The rectifier (100, 101) according to claim 16, wherein the spacing of the sensor plane of the Hall element (4) from the plane (30) flush with the free arm end of the magnetic flux guiding element (2) is provided by a base (5) arranged between the circuit substrate (3) and the Hall element (4).

18. The rectifier (100, 101) according to claim 17, wherein the Hall element (4) is soldered to the base (5).

19. The rectifier (100, 101) according to claim 17, wherein the base (5) is made of copper.

20. The rectifier (100, 101) according to claim 16, wherein the spacing of the sensor plane of the Hall element (4) from the plane (30) flush with the free arm end of the magnetic flux guiding element (2) is provided by the legs (6) of the Hall element (4).

21. The rectifier (100, 101) according to any one of claims 16 to 20, wherein the housing frame (10) is configured as a heat sink.

22. The rectifier (100, 101) according to any one of claims 16 to 20, wherein the circuit substrate (3) is a DBC substrate or an LTCC substrate.

23. The rectifier (100, 101) according to any one of claims 16 to 20, having a second circuit substrate (8) on which logic circuitry for evaluating the signal of the Hall element (4) is arranged.

24. The rectifier (100, 101) according to claim 23, wherein the circuit substrate (3) is a DBC substrate and the second circuit substrate (8) is an LTCC substrate or a PCB substrate.

25. The rectifier (100, 101) according to claim 16, wherein the spacing is determined in the direction towards the back of the magnetic flux guiding element (2) starting from the plane (30).

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