Arrangement for heat sinks in a multilevel converter
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- SIEMENS AG
- Filing Date
- 2024-08-28
- Publication Date
- 2026-04-29
Smart Images
Figure EP2024074046_27032025_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] Arrangement for heat sinks in a multilevel converter
[0003] The present invention is based on a converter,
[0004] - wherein the converter has a plurality of phase strands,
[0005] - where the phase strands each have two DC voltage connections and one AC voltage connection,
[0006] - wherein the phase strands between the AC voltage connection and the DC voltage connections each have a series connection of several semiconductor switches,
[0007] - wherein the phase strands have capacitors which are each connected to two nodes between two semiconductor switches of the respective phase strand,
[0008] - where, viewed from the AC voltage connection to the respective DC voltage connection, the number of semiconductor switches between the respective node point and the respective DC voltage connection is the same.
[0009] Such a converter is generally known.
[0010] In conventional two-level and three-level converter topologies, considerable filtering effort is required. This results in high filter volume and costs. The so-called flying-capacitor multilevel topology, in contrast, offers significant advantages.
[0011] The corresponding topology as such is known to experts. Purely as examples, reference can be made to the two technical papers "Behaviour of the flying capacitor converter under critical operating conditions" by P. Papamanolis, D. Neumayr and J. W. Kolar, 2017 IEEE 26 International Symposium on Industrial Electronics ( IS IE ) , Edinburgh, UK, 2017, pages 628 to 635, and "Analysis and Design of Multicell DC / DC Converters Using Vectorized Models" by Meynard, Thierry A. ( 2015 ).
[0012] From WO 02 / 11273 A1 a converter is known which has a plurality of phase strands. The phase strands each have two DC voltage connections and one AC voltage connection. The phase strands each have a series connection of a plurality of semiconductor switches between the AC voltage connection and the DC voltage connections. Furthermore, the phase strands have capacitors which are each connected to two nodes between two semiconductor switches of the respective phase strand. Viewed from the AC voltage connection to the respective DC voltage connection, the number of semiconductor switches between the respective node and the respective DC voltage connection is the same. In WO 02 / 11273 A1, among other things, two semiconductor switches are combined to form a power switch unit. A heat sink is attached to the side of each power switch unit.Finally, there is a housing. Several circuit breaker units, including their heat sinks, and several capacitors, including their heat sinks, are arranged in the housing.
[0013] EP 1 870 934 A1 discloses a converter which has a plurality of phase strands, each having two DC voltage connections and one AC voltage connection. The phase strands each have an individual semiconductor switch between the AC voltage connection and the DC voltage connections. Each semiconductor switch is assigned its own heat sink, which has a contact surface directly adjacent to the respective semiconductor switch and by means of which the respective semiconductor switch is cooled. Each heat sink is arranged in a housing made of insulating material, in which the heat sinks are spaced apart and thus fastened mechanically and electrically separately. Converters in industrial environments - this applies equally to two-level, three-level and multi-level converters - must typically tolerate short-term overloads.The thermal system of the respective converter must therefore be dimensioned such that the semiconductor switches can dissipate the power loss generated during such overload periods quickly enough. Heat sinks are required for this purpose.
[0014] The heat sink essentially fulfills two functions. First, it acts as a buffer, meaning it can absorb the power loss during brief overloads and later dissipate it into the environment. Second, it must also be able to absorb the power loss that occurs during continuous operation (which is lower than the power loss during overloads) and dissipate it into the environment.
[0015] The flying-capacitor multilevel topology typically features significantly more semiconductor switches than two-level and three-level converter topologies. The individual semiconductor switches can therefore be smaller and often even implemented as individual surface-mounted devices (SMDs). However, surface-mounted devices in particular have very low thermal masses, so their intrinsic overload capacity is limited. They must therefore be very well connected to a heat sink to achieve significant overload capacity.
[0016] In the prior art, it is common practice for two-level and three-level converters to arrange the semiconductor switches on a substrate. The substrate itself is electrically insulating. On one side of the substrate there is a structured copper layer which implements the circuitry and to which the semiconductor switches are applied. On the other side of the substrate there is usually another, often unstructured copper layer which borders on a heat sink. A thermal paste is often arranged between this copper layer and the heat sink. The heat sink is electrically insulated from the semiconductor switches by the substrate. It can therefore be dimensioned large and be uniform for all semiconductor switches. Touch protection is not required.
[0017] A similar approach is, in principle, also possible with a converter based on the flying-capacitor multilevel topology. However, the substrate in particular often increases the thermal resistance to such an extent that overload capacity is no longer guaranteed. This design, in conjunction with the flying-capacitor multilevel topology, is also often unsuitable for high switching frequencies. The same applies if the semiconductor switches are arranged on a printed circuit board rather than on a substrate, with the design remaining otherwise unchanged.
[0018] The object of the present invention is to further develop a converter based on the flying capacitor multilevel topology in such a way that it is overload-capable and can also be used at high switching frequencies.
[0019] The object is achieved by a converter having the features of claim 1. Advantageous embodiments of the converter are the subject of dependent claims 2 to 16.
[0020] According to the invention, a converter of the type mentioned at the outset is designed in such a way that
[0021] - that each semiconductor switch is assigned its own heat sink, which has a contact surface directly adjacent to the respective semiconductor switch and by means of which the respective semiconductor switch is cooled, and
[0022] - that the respective heat sink is arranged in a housing made of an insulating material, by which the respective heat sink is mechanically and electrically separated from the other heat sinks.
[0023] Typically, the housing is individually designed for each heat sink, so that the housing (more precisely: the respective casing) only accommodates the respective heat sink. Even if the casing accommodates multiple heat sinks, the casing has a separate receptacle for each heat sink accommodated by the casing, in which the heat sink arranged in the respective receptacle is also mechanically and electrically separated from the other heat sinks arranged in the same casing.
[0024] Due to the direct mechanical contact of the heat sink to the respective semiconductor switch, there is very good heat transfer from the respective semiconductor switch to the respective heat sink. The heat dissipation of the respective semiconductor switch is therefore very easy. This means that the overload capacity can be realized. Due to the direct mechanical contact of the heat sink to the respective semiconductor switch, there is also an electrical connection between the respective semiconductor switch and the respective heat sink. However, this is not critical due to the mechanical and electrical separation of the respective heat sink from the other heat sinks.
[0025] Preferably, the respective heat sink is held in a touch-safe manner within the housing or the housing mount. This ensures electrical operational safety even if the entire housing containing the converter is opened. Touch-safety can be achieved, for example, by ensuring that the housing openings adhere to certain dimensions, similar to IP 20 protection.
[0026] Preferably, the respective heat sink has a support surface on its side opposite the contact surface, the support surface is supported on the housing by a bearing, and the bearing is designed as a dome-like, resilient elevation. This ensures that the contact surface of the respective heat sink is aligned exactly parallel or at least almost exactly parallel to the adjacent interface of the respective semiconductor switch (coplanar alignment). Any tilting can therefore be avoided. This makes it possible to reliably ensure, in particular, good thermal connection between the respective semiconductor switch and the respective heat sink.
[0027] Preferably, the dome-like, resilient elevation supports the respective heat sink essentially centrally on the support surface. This results in a particularly reliable coplanar alignment.
[0028] Preferably, the housing is designed to cover the entire surface in the area of the support surface. This makes it particularly easy to ensure electrical insulation on this side. With regard to heat dissipation to the environment, the full-surface design is usually uncritical, since heat dissipation to the environment is achieved by a crossflow of air.
[0029] Preferably, the contact surface is bordered by inclined guide surfaces, either directly or via a step, which interact with corresponding inclined guide surfaces of the housing when the heat sink is inserted into the housing. This simplifies the installation of the converter.
[0030] Preferably, the semiconductor switches are designed as surface-mounted components (SMD). This offers manufacturing advantages, electrical advantages, and size advantages. Furthermore, a nearly uniform installation situation (low tolerances) can be achieved.
[0031] The capacitors can also be designed as surface-mounted components.
[0032] Preferably, the housing has openings for supplying air to the respective heat sink and for dissipating air from the respective heat sink. This makes the respective heat sink suitable not only for temporarily absorbing increased power loss, but also for cooling the respective semiconductor switch during continuous operation. The openings can be arranged, in particular, in the side surfaces of the housing.
[0033] The housing preferably comprises several parts, relative to the respective heat sink. As a result, the respective heat sink is surrounded by several parts of the housing. The housing as a whole, or—in the case of multiple housing receptacles—the respective receptacle, is thus formed by several parts. Only through the interaction of the various parts does the housing hold the heat sink securely in place. Furthermore, the housing is easy to assemble.
[0034] For example, one part of the housing can be arranged on the side of the respective heat sink facing away from the respective semiconductor switch, and another part can be arranged on the side of the respective heat sink facing the respective semiconductor switch. This makes it possible, on the one hand, to cover the respective heat sink completely or at least almost completely on its side facing away from the respective semiconductor switch, so that good electrical protection is provided in this area. Nevertheless, it is possible to insert the heat sink from this side into the (at this point not yet assembled) housing.
[0035] The side surfaces of the housing can, as required, be independent parts of the housing or be part of one or the other of the two aforementioned parts. Mixed forms are also possible, for example, where part of the side surfaces is arranged on one of the two aforementioned parts and another part of the side surfaces is arranged on the other of the two aforementioned parts.
[0036] A currently particularly preferred construction is that - the converter has a base plate with a top side from which orthogonally pin-like spacers protrude, - at least one of the heat sinks is arranged on the top side of the base plate, with a bottom side of the housing being arranged between the top side of the base plate and the heat sink,
[0037] - that a printed circuit board is placed on the heat sink on the side facing away from the base plate, which carries the semiconductor switch cooled by the respective heat sink on its side facing the heat sink in the area of the heat sink, and
[0038] - that holding elements are connected to the spacers, which rest on the circuit board on the side facing away from the heat sink and press the semiconductor switch onto the heat sink via the circuit board.
[0039] This design is simple, robust and works reliably.
[0040] The base plate can be made of metal (normal case) or of an electrically insulating material, in particular a plastic (exception) as required.
[0041] The base plate can be individual for each heat sink or for multiple heat sinks. It is often shared by two semiconductor switches that are equidistant from the two DC voltage terminals. The same applies to the part of the housing located between the base plate and the respective heat sink. The circuit board can also be shared by both semiconductor switches.
[0042] The capacitors, if arranged on the circuit board, can be arranged on the side of the circuit board facing the heat sink or on the side facing away from the heat sink, as required. In any case, however, they are arranged such that they are spaced apart from the heat sink. The housing preferably has guide aids that interact with the spacers, which are placed on the spacers and by means of which the housing is fixed in a plane defined by the upper side of the base plate. This also simplifies assembly.
[0043] The holding elements preferably have a first and a second leg, so that the holding elements are L-shaped. In this case, the respective first leg rests against the circuit board, and the respective second leg is connected to one of the spacers. This configuration makes it particularly easy to press the semiconductor switches against the heat sinks.
[0044] Preferably, the respective circuit board has recesses through which the second legs of the holding elements protrude. This allows the leverage and shear forces acting on the holding elements to be kept small.
[0045] Preferably, the second legs of the retaining elements engage around the spacers. This can improve the alignment of the retaining elements.
[0046] Preferably, the spacers have internal threads on their side facing away from the base plate, and the second legs have recesses for the passage of fastening screws. In this case, the holding elements are attached to the spacers by means of the fastening screws. This design is simple and reliable.
[0047] The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of the embodiments, which are explained in more detail in conjunction with the drawings. Herein, in schematic representation:
[0048] FIG 1 a converter and a load, FIG 2 a phase string,
[0049] FIG 3 a semiconductor switch and its surroundings,
[0050] FIG 4 a semiconductor switch before connecting to a heat sink,
[0051] FIG 5 shows the semiconductor switch of FIG 4 after connection to the heat sink,
[0052] FIG 6 a section through a housing and a heat sink,
[0053] FIG 7 a module of a converter in perspective view,
[0054] FIG 8 is an exploded view of the module of FIG 7 ,
[0055] FIG 9 a perspective section through the module of
[0056] FIG 7 ,
[0057] FIG 10 is a plan view of a circuit board seen from a base plate of the module of FIG 7,
[0058] FIG 11 is a perspective view of a base plate of the module of FIG 7 and part of a housing and
[0059] FIG 12 the mechanical-structural design of a converter.
[0060] According to FIG. 1, a converter has a plurality of phase strands 1. The number of phase strands 1 is usually three. However, in individual cases, it may be only two or more than three, in particular four or five.
[0061] The phase strands 1 each have, according to FIG 2, two DC voltage connections 2, 3 and one AC voltage connection
[0062] 4 . At the DC voltage terminals 2 , 3 there is usually a low potential Ul and a high potential U2 . Often the AC voltage terminal 4 is connected to the DC voltage terminals 2 , 3 via a node 5 . Between the AC voltage terminal 4 and the node
[0063] 5 a throttle 6 is usually arranged.
[0064] In this case, it is assumed that the energy flow occurs from the DC voltage terminals 2, 3 via the AC voltage terminal 4 to a load 7 (see FIG. 1). In principle, however, the reverse energy flow is also possible.
[0065] According to FIG 2, the phase strands 1 each have a series connection of a plurality of semiconductor switches 8 between the AC voltage connection 4 and the DC voltage connections 2, 3. The number of semiconductor switches 8 per series connection can be determined as required. However, the number of semiconductor switches 8 per series connection is generally the same as viewed from the AC voltage connection 4 to both the one and the other DC voltage connection 2, 3. The number of semiconductor switches 8 per series connection is also generally uniform for the phase strands 1. The number of three semiconductor switches 8 shown in FIG 2 is, however, only purely an example. There could equally well be 4, 5, 6, etc. semiconductor switches 8 per series connection.
[0066] The semiconductor switch 8 can comprise a single switching element (semiconductor switch in the narrower sense). Alternatively, the semiconductor switch 8 can comprise several switching elements arranged electrically in parallel and generally connected simultaneously and in the same way (semiconductor switch in the broader sense).
[0067] In terms of their functionality, the semiconductor switches 8 can be designed, for example, as voltage-controlled switching elements, for example based on IGBTs or FETs. This design is widespread, operates reliably, and has low switching losses. In terms of semiconductor technology, the semiconductor switches 8 can be designed, in particular, as GaN elements. In many cases, freewheeling diodes are connected in parallel with the semiconductor switches 8. The freewheeling diodes can each be an intrinsic component of the respective semiconductor switch 8. Alternatively, they can be independent diodes (i.e. discrete components). The freewheeling diodes are not shown in the figures. According to figure 2, the phase strands 1 have capacitors 9. The capacitors 9 are each connected to two nodes 10 between two semiconductor switches 8 of the respective phase strand 1.Here, from the AC voltage connection 4 to the respective DC voltage connection 2, 3, the number of semiconductor switches 8 between the respective node point 10 and the respective DC voltage connection 2, 3 is the same.
[0068] FIG 3 shows an individual semiconductor switch 8 and, in particular, the way in which this semiconductor switch 8 is cooled. According to FIG 3, a heat sink 11 is assigned to the semiconductor switch 8, by means of which heat sink the semiconductor switch 8 shown in FIG 3 is cooled. The heat sink 11 has a contact surface 12. The heat sink 11 lies with the contact surface 12 directly on the respective semiconductor switch 8. It is possible to apply a (thin) layer of thermally conductive paste between the semiconductor switch 8 and the heat sink 11. This is generally not necessary, however. Above all, the direct contact creates a galvanic connection between the heat sink 11 and the semiconductor switch 8. The heat sink 11 is therefore at the potential of the semiconductor switch 8. For electrical insulation, the heat sink 11 is therefore arranged in a housing 13. The housing 13 consists of an insulating material, usually plastic.The housing 13 mechanically and electrically separates the heat sink 11 from the other heat sinks 11. This applies regardless of whether the housing 13 contains only a single receptacle for a single heat sink 11 or multiple receptacles for multiple heat sinks 11. Even if there are multiple receptacles, the receptacles are designed in such a way that a heat sink 11 arranged in a receptacle of the housing 13 is mechanically and electrically separated not only from the heat sinks 11 arranged in other housings 13, but also from the other heat sinks 11 arranged in the same housing 13. The heat sink 11 is assigned to the semiconductor switch 8 in a proprietary manner. The term “proprietary” is to be understood in the sense that the heat sink 11 shown in FIG. 3 cools the semiconductor switch 8 shown in FIG. 3, but not any other semiconductor switches 8.The term “semiconductor switch 8” can be a semiconductor switch in the narrower sense or a semiconductor switch in the broader sense.
[0069] As is already apparent from FIG. 3 and even more clearly from FIGS. 4 and 5, the semiconductor switch 8 is arranged on a printed circuit board 14, specifically on the side of the printed circuit board 14 facing the heat sink 11. The semiconductor switch 8 can be designed, in particular, as a surface-mounted component (SMD), as shown in FIGS. 3 to 5.
[0070] 3 to 5, the heat sink 11 has a support surface 15 on its side opposite the contact surface 12. The support surface 15 can alternatively be continuous or divided into cooling fins as shown in FIGS. 3 to 5. Regardless of whether one or the other embodiment is adopted, the support surface 15 is supported on the housing 13 on a bearing 16. The bearing 16 is dome-shaped, which means that it is raised (elevated) compared to its surroundings. It is therefore an elevation. Furthermore, the bearing 16 is designed to be resiliently flexible, as indicated in FIG. 4 by an arrow 17. In most cases, the bearing 16 supports the heat sink 11 essentially centrally on the support surface 15.
[0071] The more or less point-based support on the bearing 16 (elevation) in conjunction with the resilient design means that the contact surface 12 of the heat sink 11 always lies flat against the semiconductor switch 8. This also applies if the end surface of the semiconductor switch 8 facing the heat sink 11 forms an angle with the contact surface 12 before being connected to the heat sink 11, as shown in FIG. 4 (greatly exaggerated in FIG. 4 for clarity). This is because the only point-based support in conjunction with the resilient compliance means that such tolerances can be compensated for during assembly.
[0072] 3 to 5 that the housing 13 is of full-surface construction in the region of the support surface 15. The housing 13 therefore has no openings in this region. In the region of the contact surface 12, the housing 13 can alternatively be substantially closed laterally next to the contact surface 12 (FIG. 3) or open (FIG. 4, FIG. 5). However, in the region of the side surfaces, i.e. between the contact surface 12 and the support surface 15, the housing 13 has openings 18. This makes it possible to supply air to the heat sink 11 and to remove air from the heat sink 11. The openings 18 can be full-surface. Alternatively, the side surfaces can have relatively small openings forming a grid. In this case, the heat sink 11 is held in the housing 13 in a touch-proof manner.
[0073] Preferably, the housing 13 has, with respect to the respective heat sink 11, several parts 19, 20. For example, the housing 13 can have a part as shown in FIG. 6
[0074] 19 and a part 20. In this case, the part 19 can be arranged on the side of the respective heat sink 11 facing the respective semiconductor switch 8, and the part 20 on the side of the respective heat sink 11 facing away from the respective semiconductor switch 8. Side surfaces 21 of the housing 13 are part of the part 19 in the embodiment according to FIG. 6. However, they could - at least in some cases - also be completely or partially part of the part
[0075] be 20 .
[0076] FIG 6 shows yet another advantageous embodiment of the present invention. Specifically, the heat sink 11 according to FIG 6 has inclined guide surfaces 22. In the present case, the guide surfaces 22 border on the contact surface 12 via a step 23. The step 23 could also be omitted. In this case, the guide surfaces 23 would border directly and immediately on the contact surface 12. Correspondingly, the housing 13 has corresponding inclined guide surfaces 24 (and, because of the step 23, in this case also a step 25). The guide surfaces 23, 24 interact when the heat sink 11 is inserted into the housing 13, so that the heat sink 11 is correctly positioned and aligned in the housing 13.
[0077] 7 to 11. The module 26 is the assembly unit for two semiconductor switches 8, which are arranged at corresponding locations within the series circuits. For example, the module 26 can comprise the two outer semiconductor switches 8 of the phase strand 1 of FIG. 2, which are directly adjacent to the DC voltage connection 2, 3. Alternatively, the module 26 can comprise the two inner semiconductor switches 8 of the phase strand 1 of FIG. 2, which are directly adjacent to the AC voltage connection 4 and the node 5, respectively. Alternatively, the module 26 can comprise the two middle semiconductor switches 8 of the phase strand 1 of FIG. 2, which are arranged between the inner and outer semiconductor switches 8 of the phase strand 1 of FIG. 2.
[0078] 7 to 11, the module 26 has a base plate 27. The base plate 27 has an upper side from which orthogonal pin-like spacers 28 project. At least one of the heat sinks 11 is arranged on the upper side of the base plate 27. In the present case, the two heat sinks 11 for the two semiconductor switches 8 of the module 26 are arranged on the upper side of the base plate 27. An underside of the housing 13 is arranged between the upper side of the base plate 27 and the heat sinks 11. The underside corresponds essentially to the part 20 of FIG. 6. In the present case, the side walls of the housing 13 are also partly arranged on the underside. The (in this case uniform) printed circuit board 14 is placed on the respective heat sink 11 on the side facing away from the base plate 27, which in this case carries the two semiconductor switches 8 of the module 26.In principle, it would also be possible to divide the circuit board 14 so that each semiconductor switch 8 is arranged on its own circuit board 14. Regardless of the division of the circuit board 14, the semiconductor switches 8 are arranged on the side of the circuit board 14 facing the heat sink 11, in the area of the heat sink 11. The circuit board 14 therefore carries the semiconductor switches 8 in this area.
[0079] The semiconductor switches 8 are arranged—as in FIGS. 3 to 5—on the side of the circuit board 14 facing the heat sink 11. The capacitors 9, only a few of which are provided with their reference symbols in FIGS. 7 to 11, can also be arranged on the circuit board 14. The reference symbols 9 can be arranged on one and / or the other side of the circuit board 14 as required.
[0080] The module 26 also has retaining elements 29. The retaining elements 29 are connected to the spacers 28. The retaining elements 29 rest against the printed circuit board 14, specifically on the side of the printed circuit board 14 facing away from the heat sinks 11. Via the printed circuit board 14, the retaining elements 29 press the semiconductor switches 8 against their respective heat sinks 11.
[0081] As shown, particularly in FIGS. 7 to 11, the housing 13 has guide aids 30 that interact with the spacers 28. The guide aids 30 are placed on the spacers 28. The guide aids 30 laterally fix the housing 13 in a plane defined by the upper side of the base plate 27.
[0082] The holding elements 29 have a first and a second leg 31, 32. The holding elements 29 are thus L-shaped. The respective first leg 31 rests against the circuit board 14. The respective second leg 32 is connected to one of the spacers 28.
[0083] As shown in FIGS. 7 to 11, the printed circuit board 14 has recesses 33. The recesses 33 are - see in particular FIGS. 8 and 10 - preferably completely surrounded by the material of the printed circuit board 14 when viewed in the plane of the printed circuit board 14. They are therefore preferably closed recesses. As can be seen particularly clearly from FIGS. 8 and 9, the second legs 32 of the holding elements 29 protrude through the recesses 33. The second legs 32 of the holding elements 29 preferably also engage around the spacers 28.
[0084] In order to be able to fasten the holding elements 29 to the spacers 28, the spacers 28 have an internal thread 34 on their respective sides facing away from the base plate 27. Furthermore, the second legs 32 have recesses 35 for the passage of fastening screws 36. This makes it easy to fasten the holding elements 29 to the spacers 28 by means of the fastening screws 36.
[0085] According to FIG. 12, a converter has a plurality of such modules 26. Only a few of the modules 26 and also of the semiconductor switches 8 are provided with their reference symbols in FIG. 12. Specifically, the modules 26 form three double rows, each with eight modules 26. The eight modules 26 of each double row contain, in their two rows, the two series circuits of semiconductor switches 8 of one of the phase strands 1.
[0086] As can be seen, the two heat sinks 11 of a respective module 26 are separated from one another, and the heat sinks 11 of the modules 26 are also separated from one another due to the distance between the modules 26. The base plate 27 can be uniform for all modules 26. The same applies to the undersides of the housings 13. The printed circuit board 14 is present in this case uniform for all modules 26. The housings 13 each accommodate the heat sinks 11 of a respective double row.
[0087] In summary, the present invention relates to the following:
[0088] A converter has a plurality of phase strands 1, each of which has two DC voltage connections 2, 3, one AC voltage connection 4 and, between the AC voltage connection 4 and the DC voltage connections 2, 3, a series connection of a plurality of semiconductor switches 8. The phase strands 1 also have capacitors 9, which are each connected to two nodes 10 between two semiconductor switches 8 of the respective phase strand 1. Viewed from the AC voltage connection 4 to the respective DC voltage connection 2, 3, the number of semiconductor switches 8 between the respective node 10 and the respective DC voltage connection 2, 3 is the same. Each semiconductor switch 8 is assigned its own heat sink 11, which has a contact surface 12 directly adjacent to the respective semiconductor switch 8 and by means of which the respective semiconductor switch 8 is cooled.The respective heat sink 11 is arranged in a housing 13 consisting of an insulating material, by which the respective heat sink 11 is mechanically and electrically separated from the other heat sinks 11.
[0089] The present invention has many advantages. The direct connection of the semiconductor switches 8 to the heat sinks 11 results in excellent thermal connection between the semiconductor switches 8 and the heat sinks 11, so that the overload capacity can be easily achieved. The heat transfer is further improved by the individual pressing of the semiconductor switches 8 against the heat sinks 11. Due to the bearing 16 (point-like, resilient dome-like elevation), tolerances are automatically compensated for during assembly of the modules 26. Because the individual, individually relatively small heat sinks 11, only low electrical coupling capacitances arise. This improves the EMC behavior. The converter can be scaled as required without any problems. The heat sinks 11 can usually be made from aluminum and are therefore mechanically stable and cost-effective.
[0090] Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited to the disclosed examples and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.
Claims
Patent claims 1. Inverter, - wherein the converter has a plurality of phase strands (1), - wherein the phase strands (1) each have two DC voltage connections (2, 3) and one AC voltage connection (4), - wherein the phase strands (1) between the AC voltage terminal (4) and the DC voltage terminals (2, 3) each have a series connection of a plurality of semiconductor switches (8), - wherein the phase strands (1) have capacitors (9) which are each connected to two nodes (10) between two semiconductor switches (8) of the respective phase strand (1), - wherein, viewed from the AC voltage connection (4) to the respective DC voltage connection (2, 3), the number of semiconductor switches (8) between the respective node point (10) and the respective DC voltage connection (2, 3) is the same, characterized in that - that the semiconductor switches (8) are each assigned their own heat sink (11), which has a contact surface (12) directly adjacent to the respective semiconductor switch (8) and by means of which the respective semiconductor switch (8) is cooled, and - that the respective heat sink (11) is arranged in a housing (13) consisting of an insulating material, by means of which the respective heat sink (11) is mechanically and electrically separated from the other heat sinks (11).
2. Converter according to claim 1, characterized in that the respective heat sink (11) is held in the housing (13) in a touch-proof manner.
3. Converter according to claim 1 or 2, characterized in that the respective heat sink (11) has a support surface (15) on its side opposite the contact surface (12), that the support surface (15) is supported on the housing (13) on a bearing (16) and that the bearing (16) is designed as a dome-like, resiliently yielding elevation.
4. Converter according to claim 3, characterized in that the dome-like, resiliently yielding elevation supports the respective heat sink (11) on the support surface (15) essentially centrally.
5. Converter according to claim 3 or 4, characterized in that the housing (13) is formed over the entire surface in the region of the support surface (15).
6. Converter according to claim 3, 4 or 5, characterized in that oblique guide surfaces (22) adjoin the contact surface (12) directly or via a step (23), which interact with corresponding oblique guide surfaces (24) of the housing (13) when the heat sink (L) is inserted into the housing (13).
7. Converter according to one of the above claims, characterized in that the semiconductor switches (8) are designed as surface-mounted components (SMD).
8. Converter according to one of the above claims, characterized in that the housing (13) has openings (18) for supplying air to the respective heat sink (L) and for discharging air from the respective heat sink (L).
9. Converter according to one of the above claims, characterized in that the housing (13), with respect to the respective heat sink (11), has a plurality of parts (19, 20).
10. Converter according to claim 9, characterized in that a part (20) of the housing is arranged on the side of the respective heat sink (11) facing away from the respective semiconductor switch (8) and that a further part (19) is arranged on the side of the respective heat sink (11) facing the respective semiconductor switch (8).
11. Converter according to one of the above claims, characterized in that - that the converter has a base plate (27) with an upper side from which orthogonally pin-like spacers (28) protrude, - that at least one of the heat sinks (11) is arranged on the upper side of the base plate (27), wherein a lower side of the housing (13) is arranged between the upper side of the base plate (27) and the heat sink (11), - that a printed circuit board (14) is placed on the heat sink (L) on the side facing away from the base plate (27), which printed circuit board carries the semiconductor switch (8) cooled by means of the respective heat sink (11) on its side facing the heat sink (11) in the region of the heat sink (11), and - that holding elements (29) are connected to the spacers (28) which rest on the printed circuit board (14) on the side facing away from the heat sink (11) and press the semiconductor switch (8) onto the heat sink (11) via the printed circuit board (14).
12. Converter according to claim 11, characterized in that the housing (13) has guide aids (30) which interact with the spacers (28), which are placed on the spacers (28) and by means of which the housing (13) in a region defined by the upper side of the base plate (27) level is fixed.
13. Converter according to claim 11 or 12, characterized in that the holding elements (29) have a first and a second leg (31, 32), so that the holding elements (29) are L-shaped, that the respective first leg (31) rests on the circuit board (14) and that the respective second leg (32) is connected to one of the spacers (28).
14. Converter according to claim 13, characterized in that the respective circuit board (14) has recesses (33) through which the second legs (32) of the holding elements (29) protrude.
15. Converter according to claim 13 or 14, characterized in that the second legs (32) of the holding elements (29) engage around the spacers (28).
16. Converter according to claim 13, 14 or 15, characterized in that the spacers (28) have internal threads (34) on their side facing away from the base plate (27), that the second legs (32) have recesses (35) for the passage of fastening screws (36) and that the holding elements (29) are fastened to the spacers (28) by means of the fastening screws (36).