CAPACITOR SYSTEM WITH PREDEFINED RIGIDLY MOUNTED CAPACITORS AND ELECTRICAL CIRCUIT WITH A CAPACITOR SYSTEM

Abstract

Capacitor system (100) comprising: - several capacitors (102a, 102b, 102c); - a mounting device (101) which mounts at least two of the capacitors (102a, 102b, 102c) with a rigidity predetermined on the basis of a parameter, wherein the rigidity is predetermined as a function of a rigidity of the mounting device (101), by a detachable fastening (101a) and / or by a non-detachable fastening (103c).

Description

[0001] Disclosed below are embodiments comprising a capacitor system with a plurality of capacitors, wherein different capacitors of the capacitor system are mounted with different levels of rigidity. Further embodiments relate to an electrical circuit with a capacitor system.

[0002] For example, the transmission of voltage ripples can lead to excitation during operation of a capacitor system by components in the vicinity of which the capacitors of the capacitor system are mechanically mounted. This can lead in particular to acoustic effects that may be perceived as a disturbance, or to effects that accelerate capacitor wear. Such voltage ripples can be triggered, for example, in an electrical circuit in which an AC load is powered by a DC power source via an intermediate circuit, by the carrier frequency of a PWM amplifier. This can excite the capacitors of the intermediate circuit at their resonant frequency. This can lead to annoying noise.

[0003] If the frequency of an exciting signal coincides with the natural frequency of the capacitors, e.g., the natural frequency of the windings of a film capacitor, these capacitors are excited to oscillate, resulting in high amplitudes in the mechanical excitation. This can result in airborne sound radiation and high-frequency noise, which are perceived as a disturbance.

[0004] JP 2013-206 933 A relates to a capacitor system with several capacitor elements, wherein the individual capacitor elements have different resonance frequencies and therefore expand or contract differently in response to an alternating excitation voltage.

[0005] DE 10 2017 203 106 A1 relates to a capacitor with several capacitor units, wherein at least two capacitor units are oppositely polarized.

[0006] JP 2007 - 299 888 A relates to a capacitor which is simply structured and whose wire inductance and internal inductance are reduced, wherein electrode terminal plates consist of a pair of holding electrode terminals arranged to hold the element electrodes on both sides of the capacitor elements.

[0007] DE 20 2015 004 662 U1 relates to an intermediate circuit capacitor module with low-inductance busbar connections between several individual capacitors and a connection for a semiconductor switch, in particular an IGBT, wherein the individual capacitors are designed as cup capacitors.

[0008] DE 10 2016 205 249 A1 relates to a capacitor system with two capacitors that are connected in parallel by means of electrical connecting elements and terminals, wherein the connecting elements are selected such that a first inductance of the first capacitor and a second inductance of the second capacitor are as equal as possible with respect to the terminals.

[0009] In contrast, the object is to provide an improved capacitor system which, in embodiments, should be suitable as an intermediate circuit capacitor system for vehicle and industrial converters.

[0010] This problem is solved by the respective subject matter of the independent claims. The dependent claims concern corresponding further training.

[0011] A first aspect relates to a capacitor system, in particular for an intermediate circuit, comprising a plurality of capacitors, in particular film capacitors. The capacitor system also comprises a mounting device, wherein the mounting device mounts at least two of the capacitors with a predetermined rigidity. The rigidity is predetermined by a detachable fastening and / or a non-detachable fastening, depending on the rigidity of the mounting device.

[0012] A capacitor in the capacitor system can be a foil capacitor. Additionally or alternatively, a capacitor in the capacitor system can be a film capacitor. A capacitor in the capacitor system can also be an electrolytic capacitor. Additionally or alternatively, a capacitor in the capacitor system can be a ceramic capacitor.

[0013] A film capacitor (also known as a wound capacitor or film capacitor) is a capacitor comprising at least one winding. A winding is an element in which several layers, typically foils, are wound. A current tap element is an element via which a voltage provided by the film capacitors can be tapped. This means that the film capacitors can be discharged via the current tap elements. However, this does not preclude the film capacitors from also being charged via the current tap elements. Each film capacitor can have a first and a second terminal.

[0014] The capacitor system can consist of different capacitors or of identical capacitors. In particular, a capacitor system can consist of identical capacitor types but with different dimensions.

[0015] A mounting device can be a housing of the capacitor system. A mounting device can also be a circuit board on which several capacitors of the capacitor system are arranged. A mounting device can also be a screw connection to an environmental device. Typical materials for generating rigidity can be used for the mounting device; in particular, flexible materials such as rubber or caoutchouc can be used. Stiffness can also be specified as compliance, elasticity, and / or mechanical impedance.

[0016] Capacitors of the capacitor system can in particular be connected in parallel.

[0017] The predetermined stiffness can be provided, for example, by a so-called busbar. Therefore, the bearing device can be the busbar. A busbar can be a metal sheet on which the capacitors are mounted. A predetermined stiffness can be achieved through corresponding recesses, through which the stiffness of the busbar is different at different points. A capacitor can be mounted on these points so that several capacitors are mounted on the busbar with different stiffnesses. The predetermined stiffness can be predetermined, for example, by at least two capacitors with different stiffnesses being mounted in one support of the capacitor system. The predetermined stiffness can also be achieved through a corresponding casing for one or more capacitors, which in this case represents the bearing device or at least part of the bearing device.

[0018] One embodiment relates to a capacitor system according to the first aspect, wherein the support device supports two, three or four or all capacitors with a different stiffness.

[0019] Different stiffnesses can be specified by using materials of different stiffnesses for the bearings. Additionally or alternatively, elements within one or more capacitors in the capacitor system can be varied to specify a stiffness for one capacitor or to specify different stiffnesses for several capacitors. For example, the stiffness of different capacitor windings in a film capacitor can be varied using geometric measures. This changes the natural frequencies, and the acoustic excitation occurs over a broader frequency band. This can reduce the amplitude of the excitation. Additionally or alternatively, individual capacitor windings of one or more film capacitors in the capacitor system can be mounted with different stiffnesses using asymmetric contact.

[0020] One embodiment relates to a capacitor system according to the first aspect, wherein additionally the stiffnesses differ by at least 10%.

[0021] Alternatively, the stiffnesses of two or more capacitors in the capacitor system can differ by 15%, 20%, or 30%. Additionally or alternatively, the stiffnesses of two capacitors arranged directly next to each other can differ by 10%, 15%, 20%, or 30%. If the capacitor system comprises more than two capacitors, a mounting with decreasing or increasing absolute stiffness can be implemented across several capacitors arranged in a row.

[0022] One embodiment relates to a capacitor system according to the first aspect, wherein two or more capacitors form a series and the capacitors are arranged in order of increasing or decreasing stiffness.

[0023] Increasing or decreasing stiffnesses can be defined by absolute stiffness values. Additionally or alternatively, increasing or decreasing stiffnesses can be defined by relative stiffness differences. In particular, relative stiffness differences can relate to the stiffness of a capacitor from which the stiffness values ​​of all other capacitors are derived, e.g., so that a capacitor has 10%, 15%, 20%, or 30% more stiffness, i.e., is mounted more stiffly, than a specific other capacitor in the capacitor system. In particular, one or more relative stiffness differences can each relate to the neighboring capacitor that a specific capacitor in the capacitor system has, so that, for example, one capacitor or more capacitors differ from their right- or left-hand neighboring capacitor by a specific relative stiffness, e.g., 10%.

[0024] One embodiment relates to a capacitor system according to the first aspect, wherein two or more, in particular all, capacitors have the same predetermined stiffness or the stiffnesses differ from each other by a maximum of 2%, 5%, 10% or 20%.

[0025] A specified equal stiffness for several capacitors in the capacitor system and / or specified stiffnesses that differ only slightly means that the resulting resonant frequencies are also the same or close to one another. This can be particularly advantageous if it allows the resonant frequencies of the capacitor system to be shifted into a range that is not excited by the environment, particularly the electrical and / or mechanical environment, of the capacitor system. For example, the stiffnesses of the capacitors can be specified such that they lie in a frequency range that is not excited by a PWM amplifier that interacts with the capacitor system.

[0026] One embodiment relates to a capacitor system according to the first aspect, wherein the rigidity is predetermined as a function of a rigidity of the housing of the capacitor system forming the bearing device.

[0027] A housing can, in particular, completely or partially enclose the capacitor system. The housing can be made of metal and / or plastic. The housing can comprise a layer of flexible material on which the capacitors are mounted and / or through which the housing is attached to its surroundings. This can provide a predetermined rigidity. The mounting device can be a busbar. Additionally or alternatively, the capacitor system can be suspended in the mounting device, so that the individual capacitors are mounted with a predetermined rigidity.

[0028] The rigidity is determined by a detachable fastening.

[0029] A detachable fastening can, in particular, involve a screw connection of the capacitor system or the capacitors of the capacitor system. In particular, the type of screw connection can determine rigidity.

[0030] Alternatively or additionally, the rigidity is determined by a non-removable fastening.

[0031] A non-removable fastening refers to fastenings that are not designed to be removed. Such fastenings can, in particular, be soldered, welded, and / or riveted. In particular, the rigidity of a mounting for the capacitors of the capacitor system or of the entire capacitor system can be defined by the size of the soldering points and / or the welding points.

[0032] Alternatively or additionally, the stiffness of one or more capacitors is specified based on a parameter.

[0033] The stiffness of one or more capacitors themselves can be specified based on a parameter. Such a parameter then generally also influences the resonant frequency of the corresponding capacitor(s). Therefore, such a parameter can, in particular, have a frequency, e.g., a resonant frequency, of a component in the vicinity of the capacitor system, so that the parameter affects the capacitor system accordingly. Such a parameter can, in particular, also relate to an electrical signal that affects the capacitor system from the environment of the capacitor system and could, in particular, excite one or more of the capacitors in the capacitor system.

[0034] An embodiment relates to a capacitor system according to the first aspect, wherein the parameter is a parameter of an inverter and / or a PWM amplifier.

[0035] The parameter can, in particular, relate to a switching frequency of an inverter or an H-bridge. Additionally or alternatively, a parameter can relate to a carrier frequency of a PWM amplifier. A PWM amplifier can, in particular, be a power transistor circuit (e.g., one or more H-bridges) controlled by a PWM signal. These frequencies can excite one or more of the capacitors, in particular in an intermediate circuit, for example, if these frequencies coincide with the mechanical resonance frequencies of the capacitors. For this reason, the stiffness of a bearing of one or more of the capacitors in the capacitor system can be designed such that the resonance frequency or the natural frequency of the bearing of a capacitor in the capacitor system does not coincide with one of the above-mentioned frequencies. In this case, excitation of one or more capacitors is unlikely.

[0036] An embodiment relates to a capacitor system according to the first aspect, wherein the parameter is a carrier frequency of a PWM amplifier.

[0037] An embodiment relates to a capacitor system according to the first aspect, wherein the parameter relates to a cutout band of a random PWM amplifier.

[0038] PWM amplifiers can also use multiple carrier frequencies, particularly so-called random-carrier PWM amplifiers. Within these amplifiers, individual or multiple frequencies, or entire frequency bands, can be excluded from use as carrier frequencies. In this case, the stiffness of one or more capacitors in a capacitor system can be specified such that the resonant frequency of the respective capacitor(s) coincides with one of the frequencies of a PWM amplifier not used as a carrier frequency. These capacitors are then not excited by the PWM amplifier.

[0039] A second aspect relates to an electrical circuit with an intermediate circuit, wherein the intermediate circuit comprises a capacitor system according to the first aspect.

[0040] An intermediate circuit is designed to connect different electrical power grids in such a way that interactions between the power grids are reduced. For example, an intermediate circuit can be designed to couple a direct current energy source to an alternating current load in such a way that feedback from the alternating current load to the direct current source is minimized. An intermediate circuit includes a capacitor called a link capacitor. Such a link capacitor can include multiple capacitors. Intermediate circuit capacitors can be, for example, film capacitors, ceramic capacitors, foil capacitors, and / or electrolytic capacitors.

[0041] An embodiment relates to an electrical circuit according to the second aspect, wherein the electrical circuit comprises an inverter and / or PWM amplifier and the one or more stiffnesses of the capacitor system are predetermined such that they do not coincide with a frequency of the inverter and / or the PWM amplifier.

[0042] A DC link capacitor can be used to supply a power module for an electric motor from a high-voltage storage device with reduced feedback. For example, in an electrically powered vehicle, electrical energy can be fed into the DC link from a mobile energy storage device. This energy can then be converted into a variable-frequency AC voltage via an inverter or PWM amplifier during operation to accelerate the drive motors. If the vehicle's speed needs to be reduced, the energy flow can also be reversed, so that the energy from the drive motors is fed into the mobile energy storage device via the DC link and corresponding DC link capacitors.However, voltage ripples, which occur particularly as feedback from the inverter and / or the PWM amplifier, can cause excitation of components on which the DC link capacitor is mechanically mounted during operation. This can lead to acoustic effects, which may be perceived as a disturbance.

[0043] In the following exemplary embodiments, various embodiments are described in more detail with reference to the attached figures. Fig. 1 discloses a capacitor system with a storage device designed as a busbar. Fig. 2 discloses an electrical circuit with a capacitor system for operating an AC load. Fig. 3 discloses a curve of radiated sound power over frequency for an electrical circuit with a capacitor system.

[0044] In the following, identical reference symbols refer to identical or at least functionally equivalent features.

[0045] In the following description, reference is made to the accompanying drawings, which form a part of the disclosure, and in which, by way of illustration, specific aspects in which the present invention may be understood are shown. It should be understood that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the described embodiments. The following detailed description, therefore, is not to be taken in a limiting sense, since the scope of the present invention is defined by the appended claims.

[0046] Fig. 1 describes capacitor system 100 according to one embodiment, wherein the figure naturally only describes some basic aspects of the capacitor system and the embodiment can of course have other features. The described capacitor system 100 comprises a bearing device 101 designed as a busbar. The busbar or bearing device 101 is made at least partially from a flexible metal material, e.g. spring steel, copper or aluminum, which gives the busbar a certain rigidity. By choosing a suitable material, it can be ensured in particular that the rigidity predetermined by the busbar does not change over the service life of the busbar. Three capacitors 102a, 102b, 102c are arranged next to one another on the busbar. The capacitors are connected in parallel. The capacitors are film capacitors.Of course, film capacitors or other capacitor types can also be used. The capacitors 102a, 102b, 102c are electrically coupled to the busbar. The busbar also has two detachable fastenings 101a, which in this example are designed as connection points via which the capacitor system is integrated into an electrical circuit. As can be seen, the capacitors 102a, 102b, 102c are not arranged symmetrically on the busbar. The busbar or mounting device 101 also has a recess 101b. This recess predetermines three different stiffnesses, each of which relates to one of the capacitors 102a, 102b, 102c. The recess 101b is narrow and divides an edge section into a first part 103a and a second part 103b. As can be clearly seen, the first capacitor 102a is fully supported by the edge portion 103a.The second capacitor 102b is not fully supported by edge sections 103a and 103b. The third capacitor 102c is only supported by edge section 103b. The specified stiffnesses for the capacitors 102a, 102b, and 102c are proportional to the total surface area of ​​the edge sections 103a, 103b that the respective capacitor covers. The more of the edge area a capacitor covers, the more rigidly it is mounted. As can be clearly seen, the capacitor 102a is covered most by edge section area. Due to the recess 101b, the capacitor 102b is mounted somewhat less rigidly than the capacitor 102a. The capacitor 102c, on the other hand, is not even half supported by an edge section, edge section 103b, and is thus less rigidly mounted than the capacitors 102a and 102b.In addition, the rigidity of the capacitor system 100 is influenced by a number of non-removable fastenings 103c, for example, soldering points, with which the busbar or bearing device 101 is non-removably fastened to the individual capacitors. As can be seen, the capacitor 102a is coupled to the busbar by three non-removable fastenings 103c or soldering points. It is thus more rigidly connected to the busbar than the other two capacitors 102b, 102c, which are each coupled to the busbar by only two or one soldering point, respectively. Of course, the rigidity for the capacitor system 100 shown can also be additionally specified by the type of contacting of the capacitor system via the detachable fastenings 101a or connection points, which can also be referred to as contact sections.In particular, the stiffness of the mounting of the capacitors 102a, 102b, 102c can be influenced by a more or less rigid screw connection of the busbar to the detachable fastenings 101a of the busbar.

[0047] Fig. Figure 2 shows an electrical circuit 200. The electrical circuit comprises a DC voltage source 201. The DC voltage source supplies an AC motor 202. To convert the DC current into an AC voltage for the AC motor, a PWM amplifier (or a converter controlled by a PWM signal) is used, which is contained in the AC motor and is not shown separately. A capacitor system 100 is connected in parallel to the voltage source 201 and the AC motor 202. This capacitor system can, in particular, be a capacitor system according to Fig. 1. The capacitor system 100 is configured to couple the DC voltage source 201 to the AC motor 202 in such a way that feedback from the AC motor to the DC voltage source is reduced. Such a capacitor system connection is also called an intermediate circuit. The capacitor system 100 in the intermediate circuit is configured such that interference generated by the PWM amplifier, in particular by the carrier frequencies used by the PWM amplifier, does not excite the mechanical resonant frequency of the capacitor system. This is achieved by specifying the stiffness for the capacitors of the capacitor system 100 depending on the carrier frequencies of the PWM amplifier used in the motor 202.

[0048] Fig. 3 shows the effect of a capacitor system with non-predetermined stiffness and a capacitor system 100 with predetermined stiffness, which for example is the capacitor system from Fig. 1 if these capacitor systems are used as intermediate circuit capacitors in an electrical circuit according to Fig. 2 to couple a DC voltage source to an AC motor. The diagram 300 shown shows two characteristic curves 301 (with a solid line) and 302 (with a dashed line), which essentially each describe a radiated sound power plotted against a frequency. The sound power levels indicate the noise generated by the two capacitor systems. Line 301 indicates the sound power of a capacitor system for which no stiffness was specified. With such a capacitor system, oscillations occur during operation in the range of the resonance frequency of the capacitor system, which trigger a high radiated sound power. This resonance frequency is excited by the carrier frequency of a PWM amplifier (of course, another component in the vicinity of the intermediate circuit capacitor can also generate a corresponding excitation).The radiated sound power at the resonance frequency can be perceived as a disturbance.

[0049] The characteristic curve 302, on the other hand, describes a capacitor system with a given stiffness as an intermediate circuit capacitor. A capacitor system according to Fig.1 with three capacitors mounted with different stiffnesses. The capacitor system thus has three different resonant frequencies. The characteristic curve 302 shows the sound power at these frequencies significantly reduced. This can be explained by the fact that the radiated sound power of the three capacitors no longer adds up at a single resonant frequency. This is because the different specified stiffness of the mounting of the individual capacitors in the capacitor system 100 changes the resonant frequencies. Characteristic curve 302 clearly shows the three new resonant frequencies that are generated by the specified stiff mounting of the individual capacitors in the capacitor system 100. The resonant frequencies no longer coincide, and the radiated sound power at the resonant frequencies is lower.The capacitor system of characteristic curve 301 therefore results in a lower noise load than the capacitor system of characteristic curve 301. LIST OF REFERENCE SYMBOLS 100 Capacitor system according to one embodiment 101 storage facility designed as a busbar 101a detachable fastening or contact section or connection point of the busbar 101b Recess 102a capacitor 102b capacitor 102c capacitor 103a Edge section of the busbar 103b Edge section of the busbar 103c non-removable fastening or soldering point 200 Electrical Circuit 201 DC voltage source 202 AC motor with PWM amplifier 300 diagram 301 Capacitor system characteristic curve 302 Characteristic curve of a capacitor system according to an embodiment

Claims

[1] Capacitor system (100) comprising: - several capacitors (102a, 102b, 102c); - a mounting device (101) which mounts at least two of the capacitors (102a, 102b, 102c) with a rigidity predetermined on the basis of a parameter, wherein the rigidity is predetermined as a function of a rigidity of the mounting device (101), by a detachable fastening (101a) and / or by a non-detachable fastening (103c). [2] Capacitor system according to the preceding claim, wherein the support device (101) supports two, three or four or all capacitors (102a, 102b, 102c) with a different stiffness. [3] Capacitor system according to the preceding claim, wherein the stiffnesses differ by at least 10%. [4] Capacitor system according to one of the two preceding claims, wherein two or more capacitors (102a, 102b, 102c) form a series and the capacitors (102a, 102b, 102c) are arranged in order of increasing stiffness. [5] Capacitor system according to claim 1, wherein two or more, in particular all, capacitors (102a, 102b, 102c) have the same stiffness or their stiffnesses differ from each other by a maximum of 2%, 5%, 10% or 20%. [6] Capacitor system according to one of the preceding claims, wherein the rigidity is predetermined as a function of a rigidity of a housing of the capacitor system formed by the bearing device (101). [7] Capacitor system according to the preceding claim, wherein the parameter is a parameter of an inverter and / or a PWM amplifier. [8] Capacitor system according to the preceding claim, wherein the parameter is a carrier frequency of a PWM amplifier. [9] Capacitor system according to one of the two preceding claims, wherein the parameter relates to a cut-out band of a random PWM amplifier. [10] Electrical circuit (200) comprising an intermediate circuit, wherein the intermediate circuit comprises a capacitor system (100) according to one of the preceding claims. [11] Electrical circuit according to the preceding claim, wherein the electrical circuit comprises an inverter and / or PWM amplifier and the one or more stiffnesses of the capacitor system (100) are predetermined such that they do not coincide with a frequency of the inverter and / or the PWM amplifier.

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