DE102022201333A1 - Intermediate circuit capacitor with optimized heat dissipation, power converter with such an intermediate circuit capacitor - Google Patents

Abstract

The present invention relates to an intermediate circuit capacitor (10A-B) for a power converter for energizing an electric axle drive in an electric vehicle and/or a hybrid vehicle, comprising a capacitor input (12) for connecting a voltage source, a positive-pole busbar (14a) and a negative-pole busbar ( 14b) for conducting an input current generated by means of the voltage source, a winding (16) which is electrically connected to an upper side (142) of the busbars (14a, 14b), a capacitor output (18) for feeding the input current into power electronics which are is designed to convert the input current into an output current by switching a plurality of semiconductor switching elements contained in the power electronics, the positive-pole busbar (14a) and the negative-pole busbar (14b) being thermally coupled to a cooler (22) on their underside facing away from the winding (16). are.

Description

The invention relates to an intermediate circuit capacitor for a converter, in particular an inverter, which is used to power an electric axle drive of an electric vehicle or a hybrid vehicle. The invention also relates to an electric axle drive with such a power converter and a vehicle with such an electric axle drive.

Purely electric vehicles and hybrid vehicles are known in the prior art, which are driven exclusively or in support of one or more electric machines as drive units. In order to supply the electric machines of such electric vehicles or hybrid vehicles with electric energy, the electric vehicles and hybrid vehicles include electric energy stores, in particular rechargeable electric batteries. These batteries are designed as DC voltage sources, but the electrical machines usually require an AC voltage. Therefore, power electronics with a so-called inverter are usually connected between a battery and an electrical machine (E-machine) of an electric vehicle or a hybrid vehicle.

Such inverters usually include power electronics with a number of semiconductor switching elements, which are typically formed from transistors, such as MOSFETs or IGBTs. In this context, it is known to design the semiconductor switching elements as so-called half-bridges, which have a high-side device and a low-side device. This high-side or low-side device comprises one or more semiconductor switching elements connected in parallel, which are controlled in a targeted manner during operation of the inverter in order to generate a plurality of phase currents of an AC current that are offset in time from a DC current fed into the input side of the half bridges, the phase currents each are themselves variable over time and usually assume a sinusoidal course.

It is known that intermediate circuit capacitors are used in the power converters or inverters for the purpose of greater stability of the voltages fed in and tapped off. Due to high current impressions, heat is generated not only in the power electronics but also in the intermediate circuit capacitor, which has to be dissipated. The power converters known from the prior art have the disadvantage that the intermediate circuit capacitors there cannot be sufficiently cooled. This leads to impairment of the functionality of the power converter.

It is an object of the invention to provide an intermediate circuit capacitor in order to at least partially eliminate the disadvantages mentioned above.

According to the invention, this object is achieved by the intermediate circuit capacitor, the power converter, the electric axle drive and the vehicle according to the independent patent claims. Advantageous refinements and developments of the invention emerge from the dependent patent claims.

The invention relates to an intermediate circuit capacitor for a power converter that is used to operate an electric axle drive in an electric vehicle and/or a hybrid vehicle. The intermediate circuit capacitor includes a capacitor input for connecting a voltage source and a capacitor output for feeding an input current into power electronics, which is designed to convert the input current into an output current by switching a plurality of semiconductor switching elements contained in the power electronics. For this purpose, the capacitor output is electrically connected to the power connections of the power electronics. A busbar arrangement consisting of at least one positive-pole busbar and at least one negative-pole busbar for conducting the input current generated by the voltage source is arranged between the capacitor input and the capacitor output. If the power converter is designed as a DC/AC inverter, the busbars are designed as DC busbars for conducting the DC input current. The intermediate circuit capacitor also includes at least one winding (foil capacitor), which is electrically connected to an upper side of the positive-pole (DC) busbar and the negative-pole (DC) busbar. The positive-pole (DC) busbar and the negative-pole (DC) busbar are thermally coupled to a cooler on their underside facing away from the at least one winding. The upper side and the lower side are formed on a base section of the (DC) busbars, which extends parallel to the cooler, in particular to a cooling plate. The winding is preferably cuboid, it being possible for the corners of the cuboid to be rounded. The capacitor input and the capacitor output are preferably arranged on a front side and a rear side of the cuboid shape, with the (DC) busbars being arranged on the underside of the cuboid shape.

In this way, the entire (DC) busbar arrangement of the intermediate circuit capacitor can be cooled particularly effectively. The positive pole busbar and the negative pole busbar can run parallel to one another between the at least one coil and the cooler in order to increase the cooling surface thermally connected to the cooler and thereby increase the cooling capacity. The intermediate circuit capacitor can include a current-insulating covering that is applied to a surface of the at least one winding. The current-insulating covering is preferably an injection-molded layer or housing, which is formed by over-molding the at least one winding and the (DC) busbar arrangement. In this case, the current-insulating covering has a recess in an area on the underside of the (DC) busbars. In the case of an injection layer, the recess can be accomplished by exposing the underside of the (DC) busbars during the injection molding process. This enables better thermal coupling of the (DC) busbars with the cooler. In addition, a thermally conductive layer, which is preferably made of metal, can be arranged between the underside of the (DC) busbars and the cooler. In this case, an insulating film preferably connects the underside of the busbars and the metal layer to one another in order to ensure, in combination with the thermally conductive layer, a potential separation with simultaneous heat conduction.

According to one embodiment, the positive-pole busbar and/or the negative-pole busbar have a side wing which extends vertically upwards from the bottom section of the (DC) busbars and is thermally coupled to the cooler by the underside connection already described above. This enables the at least one coil to be cooled laterally.

The invention also relates to a power converter. The power converter is preferably a DC/AC inverter for converting a DC voltage into an AC voltage. Alternatively, the converter can be designed as a DC/DC rectifier for converting a DC input voltage into a different DC output voltage. The power converter includes power electronics with a plurality of semiconductor switching elements for generating an output current based on an input current provided by a voltage source by switching the semiconductor switching elements. The power converter can have a plurality of (for example three) phase units which are each assigned to a phase current of the input current or of the output current. In the case of an inverter, the input current is a DC current provided by a DC voltage source, while the output current is an AC current with multiple phase currents. In the case of a rectifier, the input current is a DC input current provided by a DC voltage source (such as a charging station or vehicle battery/fuel cell), and the output current is a DC output current (such as a charging current) that is different from the DC input current for charging a high-voltage vehicle battery), which is preferably supplied to charge a vehicle battery.

The semiconductor switching elements are preferably transistors such as MOSFETs and/or IGBTs, it being possible for the semiconductor switching elements to additionally include one or more diodes. The semiconductor material on which the semiconductor switching elements are based is preferably silicon or a so-called wide bandgap semiconductors (WBS) semiconductor, for example silicon carbide or gallium nitride. The semiconductor switching elements are mounted on a substrate. The substrate can have a multilayer structure with a first metal layer, a second metal layer and an insulating layer located between them. In this case, the semiconductor switching elements are preferably connected to an upper side of the first metal layer, with a heat sink being connected to an underside of the second metal layer.

The power electronics have a number of power connections for feeding the input current into the semiconductor switching elements and for tapping off or delivering the output current. In the case of the inverter, the power terminals include DC power terminals and AC power terminals. The DC power connections in turn comprise one or more positive-pole and negative-pole DC power connections. The AC power connections are assigned to a common AC phase current or to one of several AC phase currents of the total AC current. The power terminals preferably extend outward beyond a side face of a potting compound, by means of which the semiconductor switching elements are potted. More preferably, the power terminals extend outside of the potting compound perpendicularly to the top of the substrate upwards, so that they can be contacted from above. The power electronics include a number of signal pins for transmitting control signals that are generated by a control device of the power converter and are sent to the control electrode (e.g. gate electrode) for driving the semiconductor switching elements.

The invention also relates to a corresponding electric axle drive with a power converter according to the invention and a vehicle with such an electric axle drive. This results in the already described in connection with the power converter according to the invention Benen advantages for the electric axle drive according to the invention and the vehicle according to the invention.

The invention is explained below by way of example using the embodiments shown in the figures.

• 1 eine schematische Darstellung eines Zwischenkreiskondensators gemäß einer Ausführung in einer Perspektivansicht, wobei der innere Aufbau des Zwischenkreiskondensators gezeigt ist;
• 2 eine schematische Darstellung des Zwischenkreiskondensators aus 1 in einer weiteren Perspektivansicht, wobei eine stromisolierende Umspritzung des Zwischenkreiskondensators gezeigt ist;
• 3 eine schematische Darstellung des Zwischenkreiskondensators aus 2 in einer weiteren Perspektivansicht, wobei eine Verbindungsschicht unterseitig des Zwischenkreiskondensators aufgebracht ist;
• 4 eine schematische Darstellung des Zwischenkreiskondensators aus 3 in einer Schnittansicht senkrecht zur Verbindungsschicht;
• 5 eine schematische Darstellung eines Zwischenkreiskondensators gemäß einer weiteren Ausführungsform in einer Perspektivansicht, wobei der innere Aufbau des Zwischenkreiskondensators gezeigt ist;
• 6 eine schematische Darstellung des Zwischenkreiskondensators aus 5 in einer weiteren Perspektivansicht, wobei eine stromisolierende Umspritzung des Zwischenkreiskondensators gezeigt ist;
• 7 eine schematische Darstellung einer Kondensatoranordnung bestehend aus drei Zwischenkreiskondensatoren aus 2 und einem Kühler in einer Perspektivansicht;
• 8 eine schematische Darstellung der Kondensatoranordnung aus 7 in einer Schnittansicht.

Show it:

• 1 a schematic representation of an intermediate circuit capacitor according to an embodiment in a perspective view, wherein the internal structure of the intermediate circuit capacitor is shown;
• 2 a schematic representation of the intermediate circuit capacitor 1 in a further perspective view, wherein a current-insulating encapsulation of the intermediate circuit capacitor is shown;
• 3 a schematic representation of the intermediate circuit capacitor 2 in a further perspective view, a connecting layer being applied on the underside of the intermediate circuit capacitor;
• 4 a schematic representation of the intermediate circuit capacitor 3 in a sectional view perpendicular to the connection layer;
• 5 a schematic representation of an intermediate circuit capacitor according to a further embodiment in a perspective view, wherein the internal structure of the intermediate circuit capacitor is shown;
• 6 a schematic representation of the intermediate circuit capacitor 5 in a further perspective view, wherein a current-insulating encapsulation of the intermediate circuit capacitor is shown;
• 7 a schematic representation of a capacitor arrangement consisting of three intermediate circuit capacitors 2 and a cooler in a perspective view;
• 8th a schematic representation of the capacitor arrangement 7 in a sectional view.

Identical objects, functional units and comparable components are denoted by the same reference symbols across the figures. These objects, functional units and comparable components are designed to be identical in terms of their technical features, unless the description explicitly or implicitly states otherwise.

1 10 schematically shows an intermediate circuit capacitor 10A according to an embodiment in an exemplary perspective view. The intermediate circuit capacitor 10A includes a capacitor input 12, a capacitor output 18 and a plurality of busbars 14a, 14b arranged in between. The intermediate circuit capacitor 10A is designed for use in a DC/AC inverter (not shown here), for example. In this case, the busbars 14a, 14b are DC busbars. The intermediate circuit capacitor 10A is described below in connection with the inverter. Alternatively, however, the intermediate circuit capacitor 10A can also be used in a DC/DC rectifier.

The DC busbars 14a, 14b include a positive-pole DC busbar 14a and a negative-pole DC busbar 14b. The positive-pole DC busbar 14a is arranged in an electrically connecting manner between a positive-pole input contact 122 of the capacitor input 12 and a positive-pole output contact 182 of the capacitor output 18 . The negative-pole DC bus bar 14b is arranged in an electrically connecting manner between a negative-pole input contact 124 of the capacitor input 12 and a negative-pole output contact 184 of the capacitor output 18 . The positive-pole input contact 122, the positive-pole DC busbar 14a and the positive-pole output contact 182 are preferably formed in one piece, as shown here by way of example. Likewise, the negative input contact 124, the negative DC bus bar 14b and the negative output contact 184, as shown here by way of example, are also preferably formed in one piece. The input contacts 122, 124 and output contacts 182, 184 each extend laterally out of a current-insulating cover 28, which is here, by way of example and preferably, designed as an overmolding. The DC busbars 14a, 14b are located within the current-insulating overmolding 28 and in the illustration in 2 therefore not apparent.

The intermediate circuit capacitor 10A includes a winding 16 (also referred to as film capacitor). As shown here by way of example, the winding 16 is preferably cuboid with rounded corners. The winding 16 is connected directly on the underside to a top side 142 of a bottom section 143 of the positive-pole DC busbar 14a and the negative-pole DC busbar 14b. Furthermore, two Y-capacitors 17 (also referred to as interference suppression capacitors or electrolytic capacitors) are provided in the intermediate circuit capacitor 10A, which are connected between the winding 16 and the capacitor output 18 on the upper side 142 of the bottom section 143 of the DC busbars 14a, 14b are arranged lying on top and are electrically connected to them. A ground line 19 also connects the Y-capacitors 17 with a screw connection from which in 1-4 only one screw guide 21 (screw sleeve) is shown. In the representation of 7 a screw 23 is also shown, by means of which the intermediate circuit capacitor 10A (there in addition to two further intermediate circuit capacitors 10A of a capacitor arrangement 100) is connected to a cooler 22.

The winding 16 and also the Y-capacitors 17 are therefore attached to the top 142 of the DC busbars 14a, 14b, which run parallel next to one another. The DC busbars 14a, 14b are thermally coupled to the cooler 22 on their underside opposite the upper side 142 . This brings about a particularly effective cooling of the intermediate circuit capacitor 10A, since the effective cooling surface is advantageously enlarged with the aid of the arrangement of the DC busbars 14a, 14b according to the invention. In addition, the winding 16 is indirectly cooled laterally by the cooler 22 with the aid of a side wing 146 of the DC busbars 14a, 14b. For this purpose, the side wing 146 extends vertically upwards from the bottom section 143 of the DC busbars 14a, 14b.

The current-insulating overmold 28 has a recess on the underside, which is created by the fact that when the winding 16, the Y-capacitors 17 and the DC busbars 14a, 14b are overmoulded, the base section 143 of the DC busbars 14a, 14b is exposed and not connected to the current-insulating Injection molding material is covered or coated. A thermally conductive layer 24 , which is preferably made of metal, is connected to the underside of the base section 143 via an insulating film 26 . As in 3 and 4 shown, a connecting layer 30 is arranged for connecting between the thermally conductive layer 24 and the cooler 22 or the upper side 222 thereof. The connecting layer 30 can be applied from a gap-filling material (engl.: gappad) by means of an injection molding process.

5 and 6 12 show an intermediate circuit capacitor 10B according to a further embodiment. In contrast to the in 1 until 4 The embodiment shown contains two windings 16 in the intermediate circuit capacitor 10B. In addition, the capacitor input 12 has two positive-pole input contacts 122 and two negative-pole input contacts 124. At the same time, the capacitor output 18 has two positive-pole output contacts 182 and two negative-pole output contacts 184. The two positive-pole input contacts 122 and the two negative-pole input contacts 124 are in pairs with respect to an intermediate level between the both winding 16 arranged symmetrically. The two positive-pole output contacts 182 and the two negative-pole output contacts 184 are also arranged symmetrically in pairs with respect to the intermediate plane between the two windings 16 . This measure favors symmetrical current flows, which improves the EMC properties of the intermediate circuit capacitor 10B.

7 and 8th show a capacitor arrangement 100, which here, by way of example, consists of three intermediate circuit capacitors 10A according to FIG 1 until 4 embodiment shown consists. Alternatively, intermediate circuit capacitors according to another embodiment described in the context of this invention, for example those in 5 until 6 embodiment shown, are used. In 7 the capacitor arrangement 100 is shown in a schematic perspective view. In 8th 1, the capacitor arrangement 100 is shown in a schematic sectional view, the sectional plane being perpendicular to the upper side 222 of the cooler 22 along a longitudinal direction in which the intermediate circuit capacitors 10A are lined up.

The intermediate circuit capacitors 10A are arranged next to one another on the upper side 222 of the cooler 22, in particular a cooling plate, and are fastened by means of a number of screws 23. The screws 23 also serve as an electrical connection to ground for the Y capacitors 17. Each intermediate circuit capacitor 10A is assigned to a phase unit of the power electronics of the inverter. The internal structure of the capacitor arrangement 100 is shown in the sectional view in FIG 8th shown closer. Although not explicitly shown there, the insulating film 26, the thermally conductive layer 24 that can be seen here and also the connecting layer 30 are arranged between the bottom sections 143 of the DC busbars 14a, 14b on the one hand and the cooler 22 on the other hand, in order to thermally connect the intermediate circuit capacitors 10A to the cooler 22 couple and at the same time to realize a potential separation between the two.

Reference List

10A-B

intermediate circuit capacitor

12

capacitor input

122

positive input contact

124

negative input contact

14a

positive busbar

14b

negative busbar

142

top

143

bottom section

146

side wings

16

wrap

17

Y capacitor

18

condenser output

182

positive output contact

184

negative output contact

19

ground wire

20

current insulating casing/overmolding

202

recess

21

screw guide

22

cooler

222

top

23

screw

24

thermal conductive layer

26

insulation film

28

current insulating casing/overmolding

30

connection layer

100

capacitor arrangement

Claims (12)

Intermediate circuit capacitor (10A-B) for a power converter for energizing an electric axle drive in an electric vehicle and/or a hybrid vehicle, comprising: - a capacitor input (12) for connecting a voltage source, - a positive-pole busbar (14a) and a negative-pole busbar (14b) for conducting an input current generated by the voltage source, - a coil (16) which is electrically connected to an upper side (142) of the busbars (14a, 14b), - a capacitor output (18) for feeding the input current into power electronics, which is designed to convert the input current into an output current by switching a plurality of semiconductor switching elements contained in the power electronics, the positive-pole busbar (14a) and the negative-pole busbar (14b) on their from the winding (16) facing away from the underside are thermally coupled to a cooler (22). intermediate circuit capacitor (10A-B) after claim 1 , wherein the positive-pole busbar (14a) and the negative-pole busbar (14b) run parallel next to each other between the winding (16) and the cooler (22). intermediate circuit capacitor (10A-B) after claim 1 or 2 , wherein the positive-pole busbar (14a) and/or the negative-pole busbar (14b) have a side wing (146) which extends vertically upwards from the underside of the busbars (14a, 14b). Intermediate circuit capacitor (10A-B) according to one of Claims 1 until 3 , further comprising a current-insulating covering (20) which is applied to a surface of the winding (16) and/or the busbars (14a, 14b). intermediate circuit capacitor (10A-B) after claim 4 , wherein the current-insulating casing (20) has a recess (202) in a region of the underside (144) of the busbars (14a, 14b). Intermediate circuit capacitor (10A-B) according to one of Claims 1 until 5 , A thermally conductive layer (24) being arranged between the underside of the busbars (14a, 14b) and the cooler (22). intermediate circuit capacitor (10A-B) after claim 6 , wherein an insulating film (26) between the underside of the busbars (14a, 14b) and the thermally conductive layer (24) is arranged. Intermediate circuit capacitor (10A-B) according to one of the preceding claims, wherein the intermediate circuit capacitor has two Y-capacitors (17), one Y-capacitor being connected to a positive-pole busbar (14a) and the other Y-capacitor being connected to a negative-pole busbar (14b). is. intermediate circuit capacitor (10A-B) after claim 8 , wherein the Y-capacitors (17) are thermally coupled to a cooler (22). Converter, in particular inverter, for energizing an electric axle drive in an electric vehicle and/or a hybrid vehicle, comprising an intermediate circuit capacitor (1 0A-B) according to one of the preceding claims. Electric axle drive for a vehicle, in particular an electric vehicle or hybrid vehicle, comprising an electric machine, a transmission device and a power converter, in particular an inverter claim 10 . Vehicle, in particular electric vehicle or hybrid vehicle, comprising an electric axle drive claim 11 .

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