Cooling system for power converter

Abstract

The invention relates to a power converter having an improved cooling system. Power converters are electrical devices which convert direct current into alternating current or vice versa. They are motionless electrical devices which are cooled by means of an air flow, in particular by means of a fan. The invention presents, for the first time, a power converter having a complex and highly effective cooling system using heat pipes which project into the chamber and penetrate different stacks of cooling plates. At every point in the power converter, the cooling system presented here for the first time takes the still present cooling capacity of a fan-generated air flow into account by way of the arrangement of cooling fins of different lengths, cooling plates in different numbers and heat pipes which penetrate the cooling plates and have different lengths. As a result, the cooling power of the generated air flow is optimised.

Description

[0001] 202422153

[0002] 1

[0003] Description

[0004] Cooling system for power converters

[0005] Technical field

[0006] The invention relates to a power converter with an improved cooling system. Power converters are electrical devices that convert direct current to alternating current or vice versa. They are stationary electrical devices that are cooled by an airflow, in particular by means of a fan.

[0007] Technical background

[0008] Power converters are stationary electrical devices or systems, meaning they have no moving parts, but are not necessarily stationary. They serve to convert one type of electrical current, e.g., direct current (DC) or alternating current (AC), into the other, or to change characteristic parameters such as voltage and frequency. Often, both principles are used in combination. There are various types of power converters, e.g., rectifiers, converters, inverters, and frequency converters. The conversion is generally carried out using modules in the form of electronic components based on semiconductors—for example, with diodes, transistors, or thyristors, in particular using MOSFETs (metal-oxide-semiconductor field-effect transistors), IGBTs (bipolar transistors with insulated gate electrodes), and IGCTs (integrated gate commutated thyristors).

[0009] Inverters, for example, allow the modification of periodically occurring electromagnetic waves to control the rotational speed of an AC motor. The inverter achieves this by changing the frequency and voltage of the supplied electrical current.

[0010] One of the most common applications of inverters and power converters in general is in electrical power supplies, specifically switched-mode power supplies, which are found in almost every electronic device. Power converters also perform the rectification and inversion of electrical current in high-voltage direct current (HVDC) transmission. Cooling is often achieved using fans that direct a cool airflow through the power converters. 202422153

[0011] 2

[0012] Modern power converter and / or inverter development relies on compact power electronics through the use of IGBT modules. This enables increasingly compact designs, which, however, result in high power dissipation density, for example, in the form of heat. Effective cooling is essential and typically limits the performance of the power converter and / or inverter.

[0013] Technical developments in large-format inverters and converters, such as those converting direct current to alternating current from 5 kW upwards (e.g., from 10,000 W, or 10 kW), are leading to an optimal device arrangement based on various factors. In this arrangement, DC and inverter IGBT modules are positioned in a row within the airflow for heat dissipation. There is no upper limit to the power output of these converters, as semiconductor components are constantly increasing in power. The problem of heat dissipation is therefore continuously increasing, necessitating the ongoing search for new solutions for heat dissipation from power semiconductor components like IGBT modules.

[0014] Both arrangements where the IGBT modules are in a line and arrangements where the IGBT modules are staggered occur in the various power converters.

[0015] Conventionally, cooling air is intended to flow past the inverter and rectifier modules during operation, driven, for example, by one or more fans or other cooling devices. As the air used for cooling passes through the converter along the individual modules, it absorbs the heat generated by the modules and thus becomes progressively warmer. Consequently, the air's absorption capacity is sometimes quite low at the last module. This also increases the temperature of the respective modules, which are no longer cooled as effectively. However, for the safe operation of the converter, the temperature of the warmest module, e.g., the IGBT module temperature, is crucial.

[0016] The airflow is directed by means of cooling fins and / or cooling plates in the power converter, which basically serve to increase the surface area that is cooled by the air flowing past it.

[0017] The problem remains that the individual electronic semiconductor component modules are cooled to varying degrees, and in particular the last electronic semiconductor component modules are cooled insufficiently. 202422153

[0018] 3

[0019] Summary of the invention

[0020] Therefore, the object of the present invention is to provide a cooling system for a power converter that overcomes the disadvantages of the prior art. In particular, the object of the invention is to increase the effectiveness and cooling effect of the available air volume of the flowing fan cooling air in the cooling system of a power converter of the order of 5 kW and above.

[0021] Accordingly, the present invention relates to a power converter with a cooling system comprising several modules in the form of electronic components for current, frequency and / or voltage conversion, each arranged on a base plate and connected in series, wherein at least one fan is provided which generates a fan airflow in the power converter through which the waste heat from the modules can be dissipated, characterized in that at least the following arrangement is realized in the fan airflow:

[0022] Cooling fins and cooling plates that direct and distribute the fan airflow, at least partially, within the power converter,

[0023] Adaptation of the number and / or shape of the cooling fins and cooling plates to the individual modules and blocks, as well as

[0024] Heat pipes are arranged along the base plates of the modules and / or projecting into the space with the fan airflow, so that they direct and distribute the fan airflow at least partially within the power converter.

[0025] According to one embodiment of the invention, the modules are arranged in blocks of at least 2, for example 2 to 30, modules.

[0026] According to one embodiment of the invention, the number of cooling plates within a block varies, with the number of cooling plates per module increasing in the direction of airflow.

[0027] According to one embodiment of the invention, the number of cooling plates varies at the beginning of a block, with the number of cooling plates at the front of the block in the direction of airflow being lower than further back in the direction of airflow, where the flowing air has already absorbed a great deal of waste heat. 202422153

[0028] 4

[0029] According to one embodiment of the invention, the number of heat pipes arranged per module varies.

[0030] According to one embodiment of the invention, the length of the heat pipes arranged in the module varies.

[0031] According to one embodiment of the invention, the arrangement of the heat pipes varies within a block and / or within the power converter.

[0032] According to one embodiment of the invention, at least one heat pipe is integrated into the base plate of a module. It is possible that part of the base plate is formed by the outer wall of the heat pipe.

[0033] According to one embodiment of the invention, the base plates of the modules are partly provided in two or more parts.

[0034] According to one embodiment of the invention, the base plate pieces of the modules are joined together by plugging them together, screwing them, soldering them, gluing them and / or other types of connection to the base plate.

[0035] According to one embodiment, the cooling fins and / or cooling plates are partially identical in shape and / or length.

[0036] In one embodiment, the cooling fins and / or cooling plates vary in shape and / or length. For example, the cooling fins are short in the front region of the fan airflow, while they are long in the rear region. Between these points, the cooling fins can have a stepped or continuously increasing length. It is also possible, for example, that the length of the cooling fins does not increase further between two blocks, but rather that the last cooling fin of a preceding block is longer than the first cooling fin of a block located further back in the fan airflow.

[0037] In one embodiment, the cooling fins and / or cooling plates are partially curved. 202422153

[0038] 5

[0039] In one embodiment, cooling fins and / or cooling plates are partially or completely provided with a surface structure, such as bumps. In another embodiment, cooling fins and / or cooling plates are partially coated.

[0040] The general insight of the present invention is that considering the cooling capacity volume of the fan airflow available at the respective location in the power converter, taking into account the waste heat generated there, inevitably leads to a cooling system in the power converter that should have many adjustable parameters, accessible during assembly, for optimizing the cooling performance at a specific module in the power converter. These parameters are the number and arrangement of cooling fins and heat sinks, as well as the number, length, and orientation of the heat pipes in the power converter.

[0041] Embodiments of the invention

[0042] According to the embodiment of the invention, the modules are arranged in blocks of at least 2, for example 2 to 30, modules. Preferably, a number of modules divisible by a factor of 3 is provided, for example for a 3-phase power grid.

[0043] The heat pipes are arranged to protrude into the room, generally penetrating the cooling plates 8. The penetration of the cooling plates is achieved, for example, with appropriate seals, so that the fan airflow does not experience turbulence.

[0044] The number of cooling plates per block increases continuously from front to back, because this makes the cooling capacity of the cooling air in the fan airflow more usable for the rear modules of the block.

[0045] By arranging heat pipes of different lengths within a module, the module's waste heat can be distributed to different areas of the fan airflow.

[0046] Exemplary embodiments of the drawing

[0047] Fig. 1 shows a section of a power converter according to an exemplary embodiment of the invention in a perspective view from above. The section shows two blocks, each with 6 modules and a cooling system.

[0048] Fig. 2 shows the same power converter in a different perspective view from below. 202422153

[0049] 6

[0050] Fig. 3 shows a section of Figures 1 and 2 in a front view.

[0051] Fig. 4 shows the other section from Figures 1 and 2 in the same view as Figure 3.

[0052] Fig. 5 shows the same section as Figure 4 in a perspective view from above.

[0053] Fig. 6 shows the same section as Figure 3 in the same perspective view from above as Figure 5.

[0054] Detailed description of the exemplary implementations

[0055] Figure 1 shows a section of a power converter 1 according to an exemplary embodiment of the invention in a perspective view from above. The two blocks 10 and 11 are visible, each having six modules 4 arranged in parallel on a base plate 3. The parallel arrangement of the modules 4 is only one example of a possible arrangement of modules 4 in a block 10 or 11. There are many types of staggered and / or stepped arrangements of the modules 4 that are intended to be included within the scope of the invention and for which the invention is equally applicable.

[0056] According to the invention, a power converter 1 is a stationary electrical device or system. There are various types of power converters, e.g., rectifiers, converters, inverters, and frequency converters. Power converters convert current through modules 4 in the form of electronic components based on semiconductors, such as diodes, transistors, or thyristors, in particular by means of MOSFETs (metal-oxide-semiconductor field-effect transistors), IGBTs (bipolar transistors with insulated gate electrodes), and IGCTs (IGC thyristors or integrated gate commutated thyristors).

[0057] The length and number of cooling fins and / or cooling plates can advantageously be precisely aligned after simulation. The cooling capacity is adjusted by directing the fan airflow towards the vicinity of the power modules 4. Direct heat transfer from the vertically finned base structure is advantageous for the heat sink area near the modules 4. The longer the cooling fins are designed, the less temperature difference can be utilized for heat transfer to the surrounding air. Therefore, it is advantageous to ensure a heat supply via heat pipes 9 for the heat sink areas furthest from the modules 4. 202422153

[0058] 7

[0059] The modules 4 are each located on a base plate 3, which is constructed either as a single piece or from several sections. In the embodiment of the invention shown here, the heat pipes 9 are part of the base plate 3 and replace it in the area of ​​the modules 4, thus enabling improved heat dissipation from the module 4 directly to the heat pipe 9 without prior heat conduction through the base plate 3. This is advantageous because heat dissipation through different materials or shaped bodies is less effective than within a heat pipe 9. The arrangement of heat pipes 9 parallel to the base plates 3 of the modules 4 is part of the cooling system 2 according to the illustrated embodiment of the invention and is complemented by the arrangement of the heat pipes 9 extending into the space containing the fan airflow 5.

[0060] A thermal management component known as a heat pipe 9 is defined as a heat pipe and / or heat conduit through which heat is efficiently transferred from the heat source, module 4, to the cooling system, in this case, the fan airflow 5. For example, a heat pipe 9 utilizes an evaporation-condensation cycle to transfer heat. However, other heat pipe concepts are also applicable within the scope of the present invention.

[0061] The use of Heat Pipes 9 is a highly effective way to transfer heat, provided air cooling is implemented. Thermal conductivities of over 20,000 W / mK are achieved at the material replacement level, representing a significant improvement compared to the common thermal conductor copper at approximately 380 W / mK. For example, direct cooling of the Heat Pipes 9 – even without cooling fins – is possible for the frontmost modules, which are not temperature-critical. This ensures high thermodynamic cooling performance. Cooling fins for increasing surface area are only used where needed. The targeted placement of the cooling fins minimizes the pressure drop of the heat sink in the airflow, thereby maximizing the volume of air moved by the fan. This results in optimal cooling of the modules and the lowest possible module temperature.

[0062] The cooling system 2 of the embodiment of the invention shown here in Figures 1 to 6 comprises the following elements:

[0063] The cooling system is based on one or more fans (not shown) that generate a fan airflow 5 through the power converter 1; further components of the cooling system are 2 202422153

[0064] The cooling system includes the cooling plates 8, which are penetrated by heat pipes 9, as can be clearly seen in the figures, and the cooling fins 6 and 7, which are arranged on the side of the base plate 3 opposite the module 4. The cooling fins are available in different lengths, for example as short cooling fins 6 (see Figures 3 and 6 for details) and as long cooling fins 7 (see Figures 4 and 5 for details). Finally, the cooling system also includes the heat pipes 9, which are arranged adjacent to the modules 4, the base plate 3, the cooling fins 6 and / or 7, and finally the cooling plates 8.

[0065] Among the advantages of the cooling system proposed here are:

[0066] • Improved thermodynamic performance

[0067] The possibility exists to standardize the heat sinks per module and use many identical parts. Except for the number of transverse fins, each heat sink has a virtually identical construction. This could result in cost advantages, as identical parts can be used across multiple devices.

[0068] • Highly effective uniformity of temperature distribution across the modules. Ideally, the device design process can follow a fixed set of rules: The hottest or last module in the final block in the airflow must always be built with a full fin array. Temperature measurements of the other modules logically lead to the conclusion that this results in local fin thinning or densification. The ideal heatsink is designed in just a few iterations in the test field or simulation.

[0069] • The device width can be better utilized: The horizontal cooling fins can use the entire device width, thus providing a larger surface area for heat transfer.

[0070] In the concept shown, it is advantageous for space reasons to arrange the modules 4 exactly one behind the other in a row, as otherwise the laterally bent heat pipes 9 could collide with the device walls (not shown). This design limitation can be implemented differently in more spacious environments. 202422153

[0071] 9

[0072] The setup shown here was compared to a previously established concept using flow simulations. The achievable temperatures of the modules 4 can be directly compared, with cooler temperatures being better. Realistic heat transfer assumptions were used for the heat pipes 9. Initial tests show that the maximum module plate temperature is reduced by approximately 4°C with a 10% lower air volume flow.

[0073] As can be clearly seen in Figures 1 and 2, in the embodiment of the invention shown here, the number of cooling plates 8 within a block 10 or 11 varies. Furthermore, the number of cooling plates 8 differs from block 10 to block 11. As can be seen, the front block 10 begins with a small stack of six cooling plates 8 and, after a stepwise increase in the number of plates in each module 4, ends with a stack of sixteen cooling plates 8. In contrast, the rear block 11 begins with a taller stack of eleven cooling plates 8 and, after a stepwise increase in the number of plates, ends with a stack of sixteen cooling plates 8. In the embodiment shown here, the stack heights of the cooling plates vary within each module 4.This is only one way to take into account the cooling capacity of the fan airflow 5 at the point in the power converter by varying the stack height within a block and from block to block by means of an adapted cooling system at that point.

[0074] Finally, Figure 1 shows the heads 12 of the Heat Pipes 9.

[0075] Figure 2 shows the same section 1 of a power converter as Figure 1, but in a perspective view from below, so that the short and long cooling fins 6 and 7 and the undersides of the cooling plates 8 are more clearly visible. However, the modules 4 are only visible at the very edge and the base plates 3 only from the side. Apart from this, it is the same section of the same power converter 1 as in Figure 1, so the reference numerals, as explained above in connection with Figure 1, have the same meaning here as well.

[0076] Figure 3 shows the front block 10 with the short cooling fins 6 in a front view. Figure 4 shows the rear block 11 with the long cooling fins 7 in a front view. Figure 5 shows the rear block 11 with the long cooling fins 7 in a perspective front view from above.

[0077] Finally, Figure 6 shows the front block 10 with the short cooling fins 6 in a perspective front view from above.

[0078] The invention provides, for the first time, a power converter with a complex and highly efficient cooling system using heat pipes projecting into the room, which various 202422153

[0079] 10

[0080] The cooling system, presented here for the first time, takes into account the remaining cooling capacity of a fan-generated airflow at every point in the power converter by arranging cooling fins of varying lengths, cooling plates in varying numbers, and heat pipes of varying lengths penetrating the cooling plates. This optimizes the cooling performance of the generated airflow.

[0081] 202422153

[0082] 11

[0083] Reference symbol list

[0084] 1 Section from a power converter

[0085] 2 Cooling system 3 Base plate

[0086] 4 Module

[0087] 5 Fan airflow

[0088] 6 short cooling fins

[0089] 7 Cooling fins long 8 Cooling plate

[0090] 9 Heat Pipe

[0091] 10 front block

[0092] 11 back block

[0093] 12 Head of a heat pipe 9

Claims

202422153 12 Patent claims 1. Power converter (1) with cooling system (2), comprising several modules (4) in the form of electronic components for current, frequency and / or voltage conversion, each arranged on a base plate (3) and connected in series, wherein at least one fan is provided which generates a fan airflow (5) in the power converter (1) through which the waste heat from the modules (4) can be dissipated, characterized in that at least the following arrangement is implemented in the fan airflow (5): o Cooling fins (6, 7) and cooling plates (8) which direct and distribute the fan airflow (5) at least partially within the power converter (1), o Adaptation of the number and / or shape of the cooling fins (6, 7) and cooling plates (8) to the individual modules (4) and blocks (10, 11), and o Heat pipes which are arranged along the base plates of the modules and / or projecting into the space with the fan airflow (5) in such a way thatthat they direct and distribute the fan airflow, at least in part, within the power converter.

2. Power converter according to claim 1, wherein the modules are arranged in blocks (10, 11) comprising 2 or more modules.

3. Power converter according to one of the preceding claims 1 or 2, wherein the number of cooling plates per module (8) varies within a block (10,11), the number of cooling plates (8) increasing in the direction of the fan airflow (5).

4. Power converter according to one of the preceding claims, wherein the number of cooling plates (8) at the beginning of a block (10, 11) within the power converter (1) varies, wherein the number of cooling plates (8) of a block (10) is less further forward in the direction of the fan airflow (5) than further back in the direction of the fan airflow (5).

5. Power converter according to one of the preceding claims, wherein the number of heat pipes (9) arranged per module is the same or different.

6. Power converter according to one of the preceding claims, wherein the length of the heat pipes (9) arranged in the module is the same or different. 202422153 13 7. Power converter according to one of the preceding claims, wherein the arrangement of the heat pipes (9) within a block (10,11) and / or within the power converter (1) is the same or different.

8. Power converter according to one of the preceding claims, wherein the heat pipes (9) are partially integrated into the base plates (3) of the modules (4).

9. Power converter according to one of the preceding claims, wherein at least one base plate (3) of a module (4) is made up of two or more parts.

10. Power converter according to claim 9, in which pieces of the base plate (3) of the module (4) are joined together to form the base plate (3) by plugging, screwing, gluing, soldering and / or welding.

11. Power converter according to one of the preceding claims, wherein cooling plates (8) are the same or different in shape and / or length.

12. Power converter according to one of the preceding claims, wherein cooling fins (6, 7) are the same or different in shape and / or length.

13. Power converter according to one of the preceding claims, wherein the number of cooling fins (6, 7) within a block and / or from block to block in the power converter (1) are the same or different.

14. Power converter according to one of the preceding claims, wherein the number of cooling plates (8) within a block and / or from block to block in the power converter (1) is different.

15. Power converter according to one of the preceding claims, wherein the cooling plates (8) and / or the cooling fins (6, 7) are at least partially bent.

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