High-voltage drive system for a vehicle, as well as a vehicle with a high-voltage drive system

Abstract

High-voltage drive system (10) for a vehicle with at least one electrical drive energy storage device (12), which is functionally connected via an electrical wiring system to at least one drive motor (14, 16) for driving at least one drive wheel in such a way that the electrical energy of the drive energy storage device (12) can be used to drive the at least one drive wheel, wherein at least one inverter (22, 28) and at least one first capacitor (20) are arranged between the drive energy storage device (12) and the drive wheel, wherein at least one second capacitor (26) is arranged in the electrical wiring system, and wherein the electrical wiring system is at least partially formed from an electrical line (34) with a first conductor (38) and at least one second conductor (40), which are arranged adjacent to each other within a sheath (44) enclosing them and are separated from each other by an insulating layer (42).characterized in that the insulating layer (42) has a dielectric strength of at least 150 kV / mm and a maximum thickness of 125 µm.

Description

[0001] The invention relates to a high-voltage drive system for a vehicle according to the preamble of claim 1, and to a vehicle with such a high-voltage drive system. In particular, the invention relates to vehicles in the form of motor vehicles, preferably motor vehicles that have all-wheel drive with an electric front and an electric rear drive.

[0002] From FR 1 358 913 A, an electrical insulator with high mechanical tensile strength is known, intended for use in connection with high-voltage, medium-voltage, and low-voltage electrical lines of power grids. No reference is made to high-voltage drive systems of vehicles or to vehicles with such drive systems.

[0003] From DE 10 2015 213 428 A1, an electrical conductor device for transmitting electric current across two separate phases is known. The conductor device has a connection for the first and second phases at one end and a connection for the first and second phases at the other end. The conductor device comprises several conductive layers arranged parallel to one another, separated by a dielectric. These layers are alternately assigned to either the first or the second phase, and depending on their assignment, either current of the first or current of the second phase can be transmitted between the connections at the first and second ends of the conductor. The conductor device preferably has between 4 and 2000 conductive layers and is intended for use in photovoltaic systems.The use of the electrical conductor system is intended to have the advantage that a capacitor – which requires a relatively large amount of installation space – can be omitted or used in a smaller size. No reference is made to high-voltage drive systems in vehicles or to vehicles with such drive systems.

[0004] DE 10 2018 203 039 A1 discloses an electrical system for a motor vehicle with an electric drive. However, this publication does not disclose any information on possible configurations of the electrical wiring of the electrical system.

[0005] US Patent 2022 / 0037062A1 discloses an electrical feedthrough for passing an electrical conductor through a barrier such as a wall of an enclosure or building.

[0006] DE 10 2017 214 040 A1 discloses an electric charging cable that serves to connect an electric charging port of an electrically powered motor vehicle to a charging station in order to enable charging of the motor vehicle.

[0007] DE 10 2011 112 333 A1 discloses an electrically powered motor vehicle with a traction line which can have a greater length depending on the length of the motor vehicle, if the motor vehicle also has a greater length.

[0008] DE 10 2017 116 445 A1 discloses a flat conductor arrangement for a vehicle's electrical system, in which flat conductors are shielded with a magnetic material.

[0009] US 2019 / 0326034A1 discloses a multi-layer insulator arrangement for high-voltage cables in electric aircraft.

[0010] EP 3 371 069 B1 discloses a multi-voltage electrical system for motor vehicles and a multi-layer cable spanning multiple voltage levels for use in such multi-voltage electrical systems of motor vehicles.

[0011] DE 10 2016 114 434 A1 shows a busbar for conducting electric current in a motor vehicle.

[0012] DE 10 2016 107 937 A1 discloses a conductor arrangement for the transmission of electrical energy in a mobile system in which an inner conductor and an outer conductor arranged coaxially to it are electrically isolated from each other by an insulating layer.

[0013] DE 10 2012 001 150 B4 discloses a power cable with an electrical conductor and an earthing conductor, which are separated by an electrically insulating layer, wherein contact between the electrical conductor and the earthing conductor can be established by applying a sufficiently high pressure to the surface of the power cable.

[0014] DE 10 2015 111 882 A1 relates to a cable for supplying electrical units in vehicles, which has auxiliary strands for carrying compensating currents.

[0015] In high-voltage drive systems for vehicles known from practical experience according to the preamble of claim 1, resonance phenomena occur, particularly in high-voltage drive systems of vehicles with electric front- and rear-wheel drive. Resonances can arise especially from the interaction of the inductance (L') of electrical lines (also called traction lines or HV lines) of such high-voltage drive systems with the intermediate capacitors (C1, C2) of the two drive inverters of two drive motors. The resonances lead to high reactive currents that oscillate back and forth between the two drive motors at the resonant frequency. This generates magnetic fields with the same frequency and additional losses across the electrical lines.The magnetic fields, through their electromagnetic force, can cause mechanical excitation in metal body structures, which in turn leads to undesirable acoustic disturbances in the vehicle. Both are detrimental and reduce the range or necessitate additional measures to shield the fields.

[0016] Electrical cables known from the prior art are constructed from round conductors and can be used shielded or unshielded. For a shielded twin cable, the inductance per unit length (L') is often around 0.4 µH / m in practice, and for unshielded twin cables around 0.7 µH / m. Regardless of whether shielded or unshielded electrical cables are used, resonances occur in the range easily audible to most people at certain capacitance values ​​of the intermediate circuit capacitors, i.e., resonances with a frequency between 20 Hz and 15 kHz, particularly between 20 Hz and 10 kHz.

[0017] Increasing the line inductance causes the resonant frequency to shift to lower frequencies, potentially making it even more bothersome. Adjusting the capacitance values ​​is usually not feasible due to the functional limitations of the drives, and / or it is very expensive and therefore uneconomical.

[0018] The resonant frequency of a system as outlined above can be calculated in a simplified manner, i.e., without taking into account the influence of a drive energy storage device in the form of a high-voltage battery, as follows: ƒres=12π⋅1L'(1C1+1C2)

[0019] Here, L' is the inductance per unit length of the electrical line, C1 is the capacitance of the first capacitor, and C2 is the capacitance of the second capacitor.

[0020] The invention is based on the objective of improving a high-voltage drive system for a vehicle according to the preamble of claim 1 and a vehicle with such a high-voltage drive system in such a way that the aforementioned acoustic abnormalities in the audible range can be avoided or at least largely reduced.

[0021] The problem is solved according to the invention by the features of the independent claims. Further practical embodiments and advantages of the invention are described in connection with the dependent claims.

[0022] A high-voltage drive system according to the invention for a vehicle comprises at least one electrical drive energy storage device, which is functionally connected via an electrical wiring system to at least one drive motor for driving at least one drive wheel, such that the electrical energy of the drive energy storage device can be used to drive the at least one drive wheel. At least one inverter and at least one first capacitor are arranged between the drive energy storage device and the drive wheel, wherein at least one second capacitor is arranged in the electrical wiring system, and wherein the electrical wiring system is at least partially formed from an electrical line with a first conductor and at least one second conductor, which are arranged adjacent to each other within a sheath enclosing them and separated from each other by an insulating layer.The insulating layer has a dielectric strength of at least 150 kV / mm. The dielectric strength values ​​mentioned in this document refer to measurements according to IEC 60243. The design makes it possible to implement an electrical conductor with a significantly reduced inductance per unit length (L') compared to conductors known from the field of high-voltage drive systems, in particular by keeping the distance between the electrical conductors within an electrical conductor very small. Voltage flashovers or short circuits are prevented by means of the insulating layer designed as described above. With the high-voltage drive system according to the invention, the resulting resonant frequencies, which were still within the audible range with electrical conductors known from the prior art (e.g., at approximately 10 ...6 kHz) in a frequency range above 10 kHz, above 15 kHz, or even above 20 kHz, so that these frequencies are only audible to a few people or even to no one. With a high-voltage drive system according to the invention, additional acoustic measures can be dispensed with because disruptive resonance frequencies are avoided. The efficiency of such a system is also increased by reducing the compensating currents. Furthermore, the capacitors provided for drive motors can potentially be made smaller in high-voltage drive systems according to the invention. Due to reduced magnetic fields, it may even be possible to route electrical cables (HV cables) within the vehicle interior with a high-voltage drive system according to the invention.

[0023] For the sake of completeness, it should be noted that the electrical conduction system preferably consists entirely of an electrical conductor with a first conductor and at least one second conductor, which are arranged adjacent to each other within an enclosing sheath and separated from each other by an insulating layer, wherein the insulating layer has a dielectric strength of at least 150 kV / mm. The same applies to all the technical features described below in more detail. Preferably, an electrical conductor of the high-voltage drive system according to the invention has the corresponding features over its entire length. If several electrical conductors are provided in the high-voltage drive system according to the invention, each electrical conductor preferably has these technical features.

[0024] In a practical embodiment of a high-voltage drive system according to the invention, the insulating layer is made of polyimide. Polyimide exists in various embodiments, particularly with dielectric strengths from 150 kV / mm to 310 kV / mm. Preferably, the insulating layer is realized with a dielectric strength of at least 180 kV / mm, more preferably at least 210 kV / mm, and most preferably with at least 250 kV / mm or even 280 kV / mm.

[0025] The aforementioned values ​​for dielectric strength can be achieved using a polyimide insulating layer with a maximum thickness of 125 µm. Preferably, a polyimide film with a maximum thickness of 100 µm is used, more preferably a maximum thickness of 75 µm, and most preferably a maximum thickness of 50 µm.

[0026] In principle, the casing can be made of the same material as the at least one insulation layer, or possibly several insulation layers. However, it is preferred that the casing be made of a different material than the insulation layer. Thermoplastic materials are particularly well-suited for the casing, especially those that can be formed by overmolding. Regardless of the manufacturing process, polyethylene (PE) is also considered a particularly suitable material for the casing due to its exceptional abrasion resistance, water repellency, and mechanical stability.

[0027] The three cable variants described below are particularly suitable for realizing the invention.

[0028] According to the first variant, the electrical conductor is formed from exactly two conductors and is designed as a flat conductor with a rectangular cross-section, whereby the first conductor and the second conductor are arranged next to each other and separated from each other by an insulating layer with a linear cross-section.

[0029] According to the second variant, the electrical conductor is formed from more than two conductors and is designed as a flat conductor with a rectangular cross-section, whereby two adjacent conductors are separated from each other by an insulating layer that is linear in cross-section.

[0030] A flat conductor within the meaning of the invention is understood to be, in particular, a conductor which has a cross-sectional width that is significantly greater than the conductor height, wherein the conductor width is in particular at least 3 times, at least 4 times, at least 5 times or at least 10 times the conductor height.

[0031] According to the third variant, the electrical conductor consists of exactly two conductors and is designed as a coaxial conductor with a circular cross-section, wherein the first conductor is arranged surrounding the second conductor and the first and second conductors are separated from each other by an insulating layer with a circular cross-section. Preferably, the first and second conductors each have an oval or circular cross-sectional shape. The inner second conductor preferably has an oval or circular solid profile, while the outer first conductor preferably has an annular hollow profile that surrounds the solid profile of the second conductor.

[0032] In another practical embodiment of a high-voltage drive system according to the invention, a first drive motor and a second drive motor are provided for driving at least two different drive wheels, with a second inverter and a second capacitor being provided for supplying energy to the second drive wheel. In practice, the resonance problems described above occur particularly frequently in such high-voltage drive systems, so that the design according to the invention is especially advantageous in connection with such high-voltage drive systems.

[0033] In conjunction with a high-voltage drive system with a first drive motor and a second drive motor, the first drive motor is preferably part of a front-wheel drive and the second drive motor is part of a rear-wheel drive or vice versa.

[0034] The invention also relates to vehicles with a high-voltage drive system as described above, in which the second capacitor is part of an air conditioning unit, a voltage converter, or a second drive motor. In this context, it is particularly noted that a second capacitor need not necessarily be provided by a second drive motor, but can also be provided by an air conditioning unit and / or a voltage converter, for example, to support a 12V electrical system, in the form of a corresponding capacitor connected to a high-voltage drive system according to the invention. In this regard, it is particularly noted that, for the purposes of the invention, a capacitor is considered to have a capacitance of at least 10 µF. Such capacitances, especially between 10 µF and 100 µF, are common for air conditioning units or voltage converters. Preferably, a vehicle according to the invention...A high-voltage drive system according to the invention comprises two capacitors with capacitances of at least 100 µF, particularly in the form of test inverters (PWRs) of drive motors. The capacitances of capacitors in high-voltage drive systems according to the invention are preferably between 100 µF and 1,000 µF, and particularly preferably between 300 µF and 800 µF.

[0035] Further practical embodiments of the invention are described below in connection with the drawings. They show: Fig. 1 a schematic representation of the structure of a high-voltage drive system according to the invention with a drive energy storage device and two functionally connected drive motors, Fig. 2 a first embodiment of an electrical conductor designed as a flat conductor with two conductors in a cross-sectional view, Fig. 3 a second embodiment of an electrical conductor designed as a flat conductor with three conductors in a cross-sectional view and Fig. 4 a third embodiment with an electrical conductor designed as a coaxial conductor with two conductors in a cross-sectional view.

[0036] Fig. Figure 1 shows a schematic representation of the structure of a high-voltage drive system 10 according to the invention, comprising a drive energy storage device 12, a first drive motor 14, and a second drive motor 16. The first drive motor 14 drives the front wheels (not shown) of a vehicle (also not shown). The second drive motor 16 drives the rear wheels of the vehicle (also not shown).

[0037] The drive energy storage device 12 is a high-voltage battery (HV battery) that provides a voltage of more than 200 V, in particular a voltage between 300 V and 1,200 V, preferably between 350 V and 1,000 V.

[0038] Between the drive energy storage 12 and the first drive motor 14, a first EMC filter 18, a first capacitor 20 with capacitance C1 and a first inverter 22 are arranged.

[0039] Between the drive energy storage 12 and the second drive motor 16, a second EMC filter 24, a second capacitor 26 with capacitance C2 and a second inverter 28 are arranged.

[0040] The unit consisting of the first EMC filter 18, the first capacitor 20, the first inverter 22 and the first drive motor 14 can be considered a front wheel drive unit 30.

[0041] The unit consisting of the second EMC filter 24, the second capacitor 26, the second inverter 28 and the second drive motor 16 can be considered a rear-wheel drive unit 32.

[0042] The electrical lines 34a, 34b leading from the drive energy storage unit 12 to the front wheel drive unit 30 and to the rear wheel drive unit 32, with line inductance K, are symbolically represented by a rectangle 36. In the embodiment shown, the lines are metallic, i.e., lines made of a metallic base material.

[0043] In the Fig. Figures 2 to 4 show three different embodiments of electrical conductors 34a, 34b, as they are used in particular in a system as described in Fig. 1 sketched high-voltage drive system 10 are installed.

[0044] The in Fig. The first embodiment shown in Figure 2 is a flat electrical conductor comprising a first conductor 38 and a second conductor 40, wherein the first conductor 38 is, in particular, a negative conductor and the second conductor 40 is, in particular, a positive conductor. Both the first conductor 38 and the second conductor 40 have a rectangular cross-sectional shape. A linear insulating layer 42 is arranged between the first conductor 38 and the second conductor 40. The insulating layer 42 is made of polyimide. The first conductor 38 and the second conductor 40 are made of a material having an electrical conductivity of at least 30 MS / m, in particular aluminum or copper. In the illustrated embodiment, the insulating layer 42 has a thickness greater than 1 µm and less than 125 µm. Preferred values ​​for the thickness of the insulating layer 42 are between 25 µm and 100 µm.In the exemplary embodiment, the insulating layer 42 is formed from polyimide in the form of a polyimide film.

[0045] On the outside, the first conductor 38 and the second conductor 40 are completely enclosed by a sheath 44. In the embodiment shown, this sheath is made of polyethylene.

[0046] The in Fig. The embodiment shown in 3 essentially corresponds to the one shown in Fig. 2 embodiment shown. However, the second conductor 40 has a different design compared to the one shown in Fig. In the embodiment shown in Figure 2, the conductor height is reduced by approximately 50 percent. Additionally, a third conductor 46 is arranged on the opposite side of the second conductor 40, resulting in a sandwich construction. If – as in the embodiment according to Figure 2 – the conductor height is reduced by approximately 50 percent. Fig. 2. Since the first conductor 38 is a negative conductor, the second conductor 40 and the third conductor 46 are preferably each a positive conductor. The foregoing applies accordingly to the insulation layers 42 and the sheathing 44, which in conjunction with Fig. 2 was described.

[0047] Fig. Figure 4 shows a further embodiment with a first conductor 38 and a second conductor 40, wherein the conductor is a coaxial cable. Accordingly, the first conductor 38 and the second conductor 40 each have a circular cross-sectional shape, with the first conductor 38 arranged to surround the second conductor 40. The second conductor 40 has a solid circular profile, while the first conductor 38 has an annular cross-sectional geometry. Reference symbol list 10 High-voltage drive system 12 drive energy storage devices 14 first drive motor 16 second drive motor 18 first EMC filter 20 first capacitor 22 first inverter 24 second EMC filter 26 second capacitor 28 second inverter 30 Front wheel drive unit 32 Rear wheel drive unit 34a,b electrical line 36 Rectangle 38 first conductor (negative conductor) 40 second conductor (positive conductor) 42 Insulation layer 44 Coat 46 third conductor C1 Capacitance of the first capacitor C2 Capacitance of the second capacitor Z line resistance

Claims

[1] High-voltage drive system (10) for a vehicle with at least one electrical drive energy storage device (12), which is functionally connected via an electrical wiring system to at least one drive motor (14, 16) for driving at least one drive wheel in such a way that the electrical energy of the drive energy storage device (12) can be used to drive the at least one drive wheel, wherein at least one inverter (22, 28) and at least one first capacitor (20) are arranged between the drive energy storage device (12) and the drive wheel, wherein at least one second capacitor (26) is arranged in the electrical wiring system and wherein the electrical wiring system is at least partially formed from an electrical line (34) with a first conductor (38) and at least one second conductor (40), which are arranged adjacent to each other within a sheath (44) enclosing them and are separated from each other by an insulating layer (42),, characterized by , that the insulating layer (42) has a dielectric strength of at least 150 kV / mm and a maximum thickness of 125 µm. [2] High-voltage drive system (10) according to the preceding claim, characterized by , that the insulating layer (42) is made of polyimide. [3] High-voltage drive system (10) according to any one of the preceding claims, characterized by , that the sheath (44) is made of a different material than the insulating layer (42). [4] High-voltage drive system (10) according to any one of the preceding claims, characterized by , that the electrical conductor (34) is formed from exactly two conductors (38, 40) and is designed as a flat conductor with a rectangular cross-section, wherein the first conductor (38) and the second conductor (40) are arranged next to each other and are separated from each other by an insulating layer (42) with a linear cross-section. [5] High-voltage drive system (10) according to one of claims 1 to 3, characterized by, that the electrical conductor (34) is formed from more than two conductors (38, 40, 46) and is designed as a flat conductor with a rectangular cross-section, wherein each pair of adjacent conductors (38, 40) are separated from each other by an insulating layer (42) with a linear cross-section. [6] High-voltage drive system (10) according to one of claims 1 to 3, characterized by , that the electrical conductor (34) is formed from exactly two conductors (38, 40) and is designed as a coaxial conductor with a round cross-section, wherein the first conductor (38) is arranged enclosing the second conductor (40) and the first conductor (38) and the second conductor (40) are separated from each other by an insulating layer (42) with a round cross-section. [7] High-voltage drive system (10) according to any one of the preceding claims, characterized by, that a first drive motor (14) and a second drive motor (16) are provided for driving at least two different drive wheels, wherein a second inverter (28) and the second capacitor (26) are provided for the energy supply of the second drive wheel. [8] High-voltage drive system (10) according to the preceding claim, characterized by , that the first drive motor (14) is part of a front wheel drive unit (30) and the second drive motor (16) is part of a rear wheel drive unit (32) or vice versa. [9] Vehicle with a high-voltage drive system (10) according to any one of claims 1 to 8, characterized by , that the second capacitor (26) is part of an air conditioning unit, a voltage converter or a second drive motor (16).

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