A cooling device and a method for cooling a power module

Abstract

Disclosed is a cooling device (14) comprising a baseplate (3) having a cavity (2) extending from a connection surface (4) of the baseplate (3) and into the baseplate (3), wherein a cooling fluid channel (11) connects the cavity (2) with a cooling fluid inlet (12) and a cooling fluid outlet (13) of the baseplate (3). The connection surface (4) comprises at least two baseplate connection means (9) arranged for connecting a power module (1) to the connection surface (4) at opposite ends of the connection surface (4), and the cooling device (14) further comprises turbulating means (5) arranged in the cavity (2). The connection surface (4) further comprises a connection means area (7) at each of the at least two baseplate connection means (9) and at least two intermediate areas (10) arranged between the at least two baseplate connection means (9) on opposite sides of the cavity (2) and wherein the at least two intermediate areas (10) are elevated in relation to the connection means areas (7) as seen in a direction perpendicular to the connection surface (4). A method for cooling a power module (1) is also disclosed.

Description

[0001] A COOLING DEVICE AND A METHOD FOR COOLING A POWER MODULE

[0002] Field of the Invention

[0003] The present invention relates to a cooling device comprising a baseplate having a cavity extending from a connection surface of the baseplate and into the baseplate, wherein a cooling fluid channel connects the cavity with a cooling fluid inlet and a cooling fluid outlet of the baseplate. The connection surface comprises at least two baseplate connection means arranged for connecting a power module to the connection surface at opposite ends of the connection surface, and the cooling device further comprises turbulating means arranged in the cavity. The invention further relates to method for cooling a power module.

[0004] Background of the Invention

[0005] Power modules comprising power electronics such as rectifiers, inverters, converters, semiconductors, transistors and other often generates much heat during use and it is therefore known to cool these devices to ensure their function and to prevent damage. Typically, this is done by mounting the power module over a cavity and then generate a flow of cooling fluid along the underside of the power module. The cooling fluid is typically cooled by being circulated through a cooling circuit and it is therefore typically pressurized.

[0006] From EP 2 207 201 Bl it is known to place an electronic component that requires cooling on top of a plate where the bottom side of the plate is cooled by liquid which is guided along the plate by means of a distributing element. But the heat transfer in such an arrangement is not particularly efficient.

[0007] From US 9,638,477 Bl it is known to place an electronic device on a plate comprising a turbulator extending from the bottom of the plate. The plate is then positioned on a manifold so that the turbulator extends down into a cavity in the manifold, and a flow of cooling liquid is established in the cavity. Forming the turbulator integrally with the plate ensures good heat conductivity but this design is complex and costly.

[0008] From WO 2022 / 156865 Al it is known to deform an oversized turbulator placed in the cavity of a baseplate when connecting a power module to the baseplate. However, the turbulator’s pressure on the power module could increase the risk of leakage of cooling fluid from the cavity.

[0009] It is therefore an object of the present invention to provide for a more simple and cost-efficient technique for cooling a power module.

[0010] The invention

[0011] The invention relates to a cooling device comprising a baseplate having a cavity extending from a connection surface of the baseplate and into the baseplate, wherein a cooling fluid channel connects the cavity with a cooling fluid inlet and a cooling fluid outlet of the baseplate. The connection surface comprises at least two baseplate connection means arranged for connecting a power module to the connection surface at opposite ends of the connection surface, and the cooling device further comprises turbulating means arranged in the cavity. The connection surface further comprises a connection means area at each of the at least two baseplate connection means and at least two intermediate areas arranged between the at least two baseplate connection means on opposite sides of the cavity and wherein the at least two intermediate areas are elevated in relation to the connection means areas as seen in a direction perpendicular to the connection surface.

[0012] To efficiently and uniformly cool the power module no matter what the ambient temperature is, the cooling fluid being circulated through the cavity is pressurized because of the pressure loss over the turbulating means the cooling fluid must be pressurized to ensure sufficient and efficient flow and cooling. However, the pressure from this pressurized cooling fluid and thermal expansion of the power module the power module will have a tendency to cause the power module to bulge between the connection means connecting the power module to the baseplate, which can lead to unwanted leakage of cooling fluid or at least severe strain on any gasket or the like arranged between the connection surface of the baseplate and the power module. I fact the travel / bulging of the part of the power module in the middle between two connection means is often so big between active and inactive state of the power module that standard gaskets like O-rings cannot be used for sealing the gap because such standard seals can only seal safely over a limited span. And non-standard seals able to seal over a greater span are expensive and difficult to implement. Thus, by forming elevated intermediate areas on the connection surface between at least some of the connection means, the power module is bend when being connected to the baseplate and thereby in a simple manner pre-tensioned downwards towards the cavity to counter the upwards pressure from the pressurized cooling fluid and thermal expansion of the power module and thereby reduce the risk of leakage.

[0013] It should be noticed, that in this context the term “connection means” should be understood as any kind of connector suited for connecting an object to a connection surface. I.e., the term includes any kind of screws, bolts, rivets, threaded rods, threaded or free holes or other or any combination thereof.

[0014] It should also be noticed, that in this context the term “connection surface” should be understood as any kind of surface on the baseplate to which the power module is connected - i.e. the area around the cavity where the base plate and the power module closely overlap. However, the term is not limited to surfaces on the baseplate directly touching the power module in that cooling paste, O-rings, gaskets or other could be arranged between the connection surface and the power module which could hinder direct contact.

[0015] It should be noticed, that in this context the term “turbulating means” should be understood as any kind of turbulator suited for generating turbulent flow in the cooling fluid flowing through the cavity. I.e. the term includes any kind of barrier, plate pattern, obstruction, obstacle or other. It should also be noted that the turbulating means can be formed integrally with the baseplate and / or the turbulating means can be formed as an independent entity placed in the cavity.

[0016] In an aspect, the cavity comprises a bottom surface having a cavity middle area arranged at the middle of the bottom surface and a cavity periphery area arranged at a periphery of the bottom surface and wherein the cavity middle area is elevated in relation to the cavity periphery area as seen in a direction perpendicular to the connection surface.

[0017] To efficiently cool the power module, it is important that the turbulating means are as close to or even directly touching the underside of the power module and if the bottom of the cavity is flat and level, the distance between the bottom and the underside of the power module will vary when the height of the connection surface varies and it is therefore difficult to ensure close proximity between the turbulating means and the underside of the power module. It is therefore advantageous to also elevate the cavity middle area in relation to the cavity periphery area to ensure that the turbulating means is brought into closer and more uniform proximity of or contact with the underside of the power module.

[0018] In an aspect, the cavity middle area is elevated in relation to the cavity periphery area by the same amount that the at least two intermediate areas are elevated in relation to the connection means areas + / - 50%, preferably + / - 40% and most preferred + / - 30%.

[0019] Elevating the cavity middle area in relation to the cavity periphery area by the same amount that the intermediate areas are elevated in relation to the connection means areas - plus / minus a certain percentage to compensate for any production tolerances, deflection inaccuracies or tolerances in the power module and / or the turbulating means and / or other - increases the chance of close and uniform proximity or contact between the entire overside of the turbulating means and the underside of the power module. In an aspect, the turbulating means comprises a turbulator middle area arranged at the middle of the cavity and a turbulator periphery area arranged at a periphery of the cavity along the connection surface and wherein the middle height of the turbulating means at the turbulator middle area is bigger than the periphery height of the turbulating means at the turbulator periphery area, wherein the middle height and the periphery height is measured in a direction perpendicular to the connection surface.

[0020] If the bottom surface of the cavity is flat or if height differences of the bottom surface of the cavity does not fully compensate for the distance differences between the bottom surface of the cavity and the underside of the bend power module, it is advantageous to design the turbulating means so that the middle area of the turbulating means is thicker / bigger than the thickness of the turbulating means at the turbulator periphery area to bring the turbulating means into closer and more uniform proximity of or contact with the underside of the power module.

[0021] In an aspect, the middle height is bigger than the periphery height by the same amount the at least two intermediate areas are elevated in relation to the connection means areas + / - 50%, preferably + / - 40% and most preferred + / - 30%.

[0022] Increasing the thickness of the turbulating means in the middle in relation to the thickness of the turbulating means at the turbulator periphery area at the periphery of the cavity - plus / minus a certain percentage to compensate for any production tolerances, deflection inaccuracies or tolerances in the power module and / or the turbulating means and / or other - increases the chance of close and uniform proximity or contact between the entire overside of the turbulating means and the underside of the power module.

[0023] In an aspect, the turbulating means are extending from a bottom surface of the cavity and at least up to the at least two intermediate areas. Making the turbulating means extend from the bottom surface of the cavity and at least up to the intermediate areas is advantageous in that this increases the chance of close proximity or contact between the entire overside of the turbulating means and the underside of the power module when the power module is connected to the baseplate.

[0024] It should be noted that the bottom surface of the cavity does not have to be formed integrally with the rest of the baseplate. I.e., in an embodiment the bottom surface of the cavity could comprise a separate plate, sheet, block or other.

[0025] In an aspect, the connection surface is gradually elevated between the connection means area and the intermediate area.

[0026] Gradually elevating the connection surface between the connection means area and the intermediate area to generate the height difference in one or more steps is advantageous in that the elevation hereby is easier to form - e.g., in a few machining steps or by fitting plates to the connection surface.

[0027] In an aspect, a smooth height transition of the connection surface is formed between the connection means area and the intermediate area.

[0028] Forming a smooth height transition of the connection surface between the connection means area and the intermediate area is advantageous in that the risk of any gaps forming between the underside of the power module and the connection surface, when the power module is connected to the connection surface and bend over the intermediate areas, is hereby reduced.

[0029] In an aspect, the connection surface comprises four baseplate connection means describing a rectangle. Making the connection surface comprises four baseplate connection means arranged in a rectangle is advantageous in that this enables the power module to be connected at four corners while at the same time ensuring simple and fast connection and disconnection of the power module to the baseplate.

[0030] In an aspect, the at least two intermediate areas are arranged in the middle between the at least two baseplate connection means on opposite sides of the cavity.

[0031] Arranging the intermediate areas in the middle between the baseplate connection means on opposite sides of the cavity is advantageous in that the stress of bending the power module is hereby more evenly distributed thereby reducing the risk of local stress concentrations.

[0032] In an aspect, the at least two intermediate areas are elevated by an intermediate height in relation to the connection means areas, wherein the intermediate height is between 0.05% and 10%, preferably between 0.1% and 6%, and most preferred between 0.2 and 3% of the connection distance between the at least two baseplate connection means.

[0033] If the intermediate areas are elevated too much, in relation to the connection distance between the baseplate connection means areas, the risk of overbending the power module and thereby damaging it increases. However, if the intermediate areas are elevated too little in relation to the connection distance the pre-tension induced by bending the power module is so little that it will not counter the pressure from the cooling fluid sufficiently. The present percentage ratios therefore present an advantage relationship between safety and functionality.

[0034] In an aspect, the cooling device further comprises a power module being connected to the connection surface.

[0035] Hereby is achieved an advantageous embodiment of the invention. In an aspect, the power module is connected to the connection surface by means of module connection means of the power module engaging the at least two baseplate connection means.

[0036] Connecting the power module to the connection surface by means of module connection means engaging the baseplate connection means is advantageous in that this ensures a simple and fast connection between the power module and the baseplate.

[0037] In an aspect, the module connection means are arranged along a periphery of the power module.

[0038] Arranging the module connection means along the periphery of the power module is advantageous in that this allows much space for the power electronics on the power module, and it ensures easy access to the module connection means. Furthermore, this location enables easier bending of the power module.

[0039] In an aspect, the at least two module connection means comprise bolts.

[0040] Connecting the power module to the connection surface by means of bolts is advantageous in that bolts are excellent for generating the downward force needed to force the power module downwards towards the connection means areas of the connection surface so that the power module is bend across the intermediate areas while at the same time forming a tight connection between the power module and the connection surface.

[0041] In an aspect, the power module comprises heat generating power electronics. Power electronics generates much heat and therefore needs efficient cooling, and it is therefore particularly advantageous to cool heat generating power electronics by means of the present invention.

[0042] In an aspect, the power module fully covers the cavity.

[0043] Forming the power module and / or the cavity so that the power module fully covers the cavity when the power module is connected to the connection surface is advantageous in that a closed space is hereby formed under the power module enabling a leak-free flow of cooling fluid along the underside of the power module.

[0044] In an aspect, the cooling device further comprises a gasket encircling the cavity.

[0045] Arranging a gasket between the power module and the baseplate all around the cavity is advantageous in that this reduces the risk of the cooling fluid leaking out between the power module and the baseplate.

[0046] In an aspect, the gasket is arranged in a baseplate groove in the connection surface.

[0047] Arranging the gasket in a groove in the connection surface is advantageous in that this ensures the correct position of the gasket is maintained at all times - thus, simplifying the mounting and dismounting procedure.

[0048] In an aspect, the baseplate connection means comprises threaded holes arranged in the connection surface or threaded rods extending from the connection surface.

[0049] Making the baseplate comprise threaded holes and / or threaded rods is advantageous in that a tight and forceful connection between the power module and the baseplate hereby can be made is a simple manner.

[0050] In an aspect, the baseplate is made of metal. Forming the baseplate of metal is advantageous in that metal is an excellent conductor of heat.

[0051] In an aspect, the metal is aluminium.

[0052] Forming the baseplate of aluminium is advantageous in that aluminium is inexpensive, easy to machine and it is an excellent conductor of heat.

[0053] In an aspect, the turbulating means comprises a turbulator arranged as an independent unit in relation to the baseplate.

[0054] Forming the turbulating means as a turbulator that is independent from the baseplate is advantageous in that this enables that the turbulator can be made from a different material - e.g., more suited for forming turbulators - and the turbulator can more easily be provided with a more complex and efficient design in that it can be manufactured in a separate process.

[0055] The invention further relates to a method for cooling a power module, wherein the method comprises the steps of:

[0056] • forming a cavity in a baseplate so that the cavity is extending from a connection surface of the baseplate and into the baseplate,

[0057] • forming at least two baseplate connection means in the connection surface,

[0058] • forming the connection surface so that it comprises a connection means area at each of the at least two baseplate connection means,

[0059] • forming at least two intermediate areas between the at least two baseplate connection means on opposite sides of the cavity and so that the at least two intermediate areas are elevated in relation to the connection means areas as seen in a direction perpendicular to the connection surface,

[0060] • arranging turbulating means in the cavity, • connecting the power module to the connection surface by means of the at least two baseplate connection means so that at least a part of the power module is bend across the at least two intermediate areas, and

[0061] • generating a flow of cooling fluid through the cavity to cool the power module.

[0062] Bending at least a part of the power module over the intermediate areas on opposite sides of the cavity, when the power module is connected to the connection surface is advantageous in that this bending of the power module will pre-tension the power module in a direction opposite the pressure from the cooling fluid and possible heat expansion of the power module and thereby reduce the risk of leakage of cooling fluid between the power module and the connection surface.

[0063] It should be noted that the method steps do not necessarily have to be performed in the order that they are listed. E.g., the turbulating means could be formed in the cavity during forming of the cavity, the at least two baseplate connection means could be formed at any time before connecting the power module to the connection surface, the connection means area and the intermediate areas could be formed in opposite order or simultaneously at any time before connecting the power module to the connection surface and so on.

[0064] In an aspect, the method further comprises the step of arranging a gasket between the power module and the baseplate.

[0065] Arranging a gasket between the power module and the baseplate is advantageous in that this reduces the risk of the cooling fluid leaking out between the power module and the baseplate.

[0066] In an aspect, the cooling fluid is pressurized to a pressure between 200,000 and 1,500,000 pascal, preferably at between 250,000 and 1,000,000 pascal, and most preferred between 300,000 and 800,000 pascal. If the pressure of the cooling fluid is too little the flow of cooling fluid is reduced or stopped due to pressure drop through the system and the cooling fluid cannot be efficiently cooled in a cooling circuit without being pressurized to a certain extent. However, if the pressure of the cooling fluid is too high the pressure will strain the entire cooling device, and the risk of leakage is increased. Thus, the present pressure ranges present an advantageous relationship between cooling efficiency and functionality.

[0067] In an aspect, the power module is connected tightly to the baseplate.

[0068] Connecting the power module tightly to the baseplate is advantageous in that this reduces the risk of the cooling fluid leaking out between the power module and the baseplate and it ensure good heat conduction between the baseplate and the power module.

[0069] In an aspect, the power module is cooled by means of a cooling device according to any of the previously discussed cooling devices.

[0070] Hereby is achieved an advantageous embodiment of the invention.

[0071] Figures

[0072] The invention will be explained further herein below with reference to the figures in which: fig. 1 shows a cooling device with a power module, as seen from the top, fig. 2 shows cross section A- A indicated in fig. 1, as seen from the front, fig. 3 shows cross section B-B indicated in fig. 1, as seen from the front, fig. 4 shows cross section C-C indicated in fig. 1, as seen from the side, fig. 5 shows cross section D-D indicated in fig. 1, as seen from the side, fig. 6 shows turbulating means, as seen from the front, and fig. 7 shows a cooling device with a power module, as seen in an isometric view.

[0073] Detailed description

[0074] Fig. 1 shows a cooling device 14 with a power module 1, as seen from the top.

[0075] In this embodiment the power module 1 comprises power electronics 17 in the form an insulated-gate bipolar transistor (IGBT) unit formed with a bottom plate. However, in another embodiment the power module 1 could also or instead comprise converters, power MOSFETs, thyristors or other and / or the power module 1 would not comprise a bottom plate or the power module 1 could be designed in a multitude of other ways known to the skilled person.

[0076] In this embodiment the baseplate 3 is made from a single block of machined aluminium, but in another embodiment the baseplate 3 could be cast and / or the baseplate 3 could be made in from another material such as stainless steel, brass, cobber or another metal, the baseplate could be made from a composite material, ceramic or other or any combination of the above. And / or the baseplate 3 could be made from two or more interconnected elements - e.g., interconnected through soldering, welding, adhesive, bolts or other.

[0077] In this embodiment both the baseplate 3 and the power module 1 are rectangular (seen from the top) and in this embodiment both the baseplate 3 and the power module 1 are generally cuboid shaped but in another embodiment the baseplate 3 and / or the power module 1 could be provided with a different shape, such as round, square, polygonal, oval or other.

[0078] Fig. 2 shows cross section A-A indicated in fig. 1, as seen from the front.

[0079] In this embodiment the baseplate 3 includes a connection surface 4 and in this embodiment baseplate connection means 9 - in this case in the form of threaded blind holes - are formed in the connection surface 4 of the baseplate 3. Accordingly, the power module 1 is in this embodiment provided with matching module connection means 22 - in this case in the form of bolts extending through through- holes in the power module 1 so that the bolt engages the threaded holes in the baseplate 3. However, in another embodiment the baseplate connection means 9 could comprise threaded rods extending from the connection surface 4 through the through-holes in the power module 1 and then the connection force could be provided through module connection means 22 in the form of a nut.

[0080] Fig. 3 shows cross section B-B indicated in fig. 1, as seen from the front.

[0081] In this embodiment the baseplate 3 comprises a single cavity 2 extending from the connection surface 4 and down into the baseplate 3. However, in another embodiment the baseplate 3 could comprise another number of cavities 2 - such as two, four, eight or even more - each being provided with a power module 1 or a power module could extend across more than one cavity 2. In this embodiment the cavity 2 is milled in the baseplate 3 but in another embodiment the cavity 2 could also or instead be formed by spark machining, drilling, stamping or other or any combination thereof or the cavity 2 could be formed in a casting process.

[0082] In this embodiment turbulation means 5, in the form of an independent turbulator 5, is then arranged in the cavity 2. This will be discussed in more details in relation to fig. 5. In the embodiment the baseplate 3 is provided with a baseplate groove 15 in which a gasket 6 is placed and in this embodiment the baseplate groove 15 and the gasket 6 is fully encircling the cavity 2. Placing the gasket 6 in a groove 15 simplifies assembly and ensures that the gasket 6 stays in the right place but in another embodiment the baseplate 3 would not be provided with a baseplate groove 15 and the gasket 6 would be placed directly between the baseplate 3 and the power module 1. In this embodiment the gasket 6 is an O-ring made from rubber but in another embodiment the gasket 6 could have another shape, such as oval, rectangular, flat, or other and / or the gasket 6 could be made in another material such as cobber, plastic, a composite material or other or the gasket 6 could be formed by a sealing paste.

[0083] In this embodiment a connection surface 4 is formed all around the cavity 2 to which the power module 1 is connected. In this embodiment a connection surface 4 comprises a connection means area 7 at each of the baseplate connection means 9 and an intermediate area 10 is formed between baseplate connection means 9 on both sides of the cavity 2, wherein the intermediate areas 10 on opposite sides of the cavity 2 are elevated upwards in relation to the connection means areas 7 so that when the connection means 9, 22 are tightened, the contact face 8 of the power module 1 at the corners are forced down against the connection means areas 7 so that the power module 1 is bend slightly over the elevated intermediate areas 10.

[0084] Fig. 4 shows cross section C-C indicated in fig. 1, as seen from the side and fig. 5 shows cross section D-D indicated in fig. 1, as seen from the side.

[0085] In this embodiment a connection surface 4 is formed with a connection means area 7 at each of the baseplate connection means 9 - wherein all the connection means areas 7 are flush and level - and an intermediate area 10 is formed between the baseplate connection means 9 on both sides of the cavity 2 similar to the design described in relation to fig. 3. Thus, in this embodiment intermediate areas 10 are formed between all the baseplate connection means 9 so that the power module is bend in both directions when the connection means 9, 22 are tightened. However, in another embodiment the connection surface 4 would only comprise elevated intermediate areas 10 along the longest sides of the cavity 2 (as disclosed in figs. 4 and 5) or only along the shortest sides of the cavity 2 (as disclosed in figs. 2 and 3) and / or more than one elevated intermediate area 10 could be formed between the baseplate connection means 9.

[0086] In this embodiment the entire connection surface 4 is formed at a level under the top surface 23 of the baseplate 3 because in this embodiment the shape of the connection surface is formed through milling but in another embodiment the connection means areas 7 could be level with the top surface 23 of the baseplate 3 and the intermediate areas 10 would be raised above the top surface 23 of the baseplate 3 or the connection surface 4 could be formed in another level in relation to the top surface 23 of the baseplate 3. In another embodiment the connection surface 4 could be formed through a casting process or the connection surface 4 could be formed as an independent height altering part being connected to the baseplate 3 which would enable simple retrofitting.

[0087] In this embodiment a smooth height transition of the connection surface 4 is formed between the connection means areas 7 and the intermediate area 10 to form a gliding transition between the two different heights of the connection means areas 7 and the intermediate area 10. However, in another embodiment the height of the connection surface 4 could be gradually elevated in one or more steps between the connection means areas 7 and the intermediate area 10.

[0088] As disclosed in fig. 1 and 7 the connection surface 4 does in this embodiment comprises four baseplate connection means 9 describing a rectangle because in this embodiment the power module 1 is provided with a rectangular shape - note that a square is also a rectangle. However, in another embodiment connection means 9, 22 would be provided only at the middle of opposite ends of the power module so that the cooling device 14 only comprised two sets of connection means 9, 22, the power module 1 could be connected to the baseplate 3 by means of more than four sets of connection means 9, 22 and / or the sets of connection means 9, 22 could be distributed different such as in a triangle in a circle or other.

[0089] In this embodiment the intermediate area 10 is arranged in the middle between the two baseplate connection means 9 but, in another embodiment, the intermediate area 10 could be arranged closer to one of the two baseplate connection means 9 than to the other - e.g., depending on the design of the power module 1.

[0090] In this embodiment the connection distance CD between the two baseplate connection means 9 is around 115 mm and, in this embodiment, the intermediate area 10 is elevated by an intermediate height IH of 0.45 mm in relation to the two connection means areas 7. Thus, in this embodiment the intermediate height IH is around 0.4% of the connection distance CD between the two baseplate connection means 9. However, in another embodiment the intermediate height IH could be bigger in relation to the connection distance CD - such as 0.8%, 1%, 2% or even more - or the intermediate height IH could be smaller in relation to the connection distance CD - such as 0.35%, 0.25%, 0.15% or even less - e.g. depending on the size or design of the power module 1, the pressure of the cooling fluid or other. In another embodiment the intermediate height IH of different intermediate areas 10 could vary e.g., depending on the design of the power module 1, the size of the power module 1 or other. Also note that the physical size of the power module 1 and thereby the baseplate 2, cavity 3, turbulator 5 can very greatly depending on the specific use, nature and design of the power module 1.

[0091] In this embodiment cavity 2 comprises a bottom surface 16 having a cavity middle area 18 arranged at the middle of the bottom surface 16 which is elevated in relation to a cavity periphery area 19 arranged at a periphery of the bottom surface 16. In this embodiment the cavity middle area 18 is elevated in relation to the cavity periphery area 19 by the same amount that the at the intermediate areas 10 are elevated in relation to the connection means areas 7 to compensate for the elevation of the underside of the power module induced by being bend over the intermediate areas 10. In will ensure that substantially the entire overside of the turbulating means 5- extending from the bottom surface 16 and at least up to the intermediate areas 10 and having a substantially constant thickness - will be forced against the underside of the power module 1 to ensure efficient heat transfer. However, due to production tolerances and the fact that if intermediate areas 10 are formed in more than one direction - which would elevate the part of the power module 1 over the cavity middle area 18 more in relation to the cavity periphery area 19 that the height difference between the connection means areas 7 and the intermediate area 10 - the height difference between the cavity middle area 18 and the cavity periphery area 19 could vary in relation to the height difference between the connection means areas 7 and the intermediate area 10 by + / - 10%, + / - 20%, + / - 35% or even more.

[0092] In this embodiment the shape of the bottom surface 16 is formed through milling but in another embodiment the bottom surface 16 could be formed through a casting process or the bottom surface 16 could be formed as an independent height altering part being connected to the baseplate 3 which would enable simple retrofitting.

[0093] In this embodiment the cooling device 14 further comprises a cooling fluid channel 11 having a cooling fluid inlet 12 and a cooling fluid outlet 13 enabling that a flow of cooling fluid can be established through the cavity 2 in the baseplate 3 e.g. by means of an external pump (not shown) forming part of a cooling circuit. In this embodiment cooling fluid channels 11 are formed both lengthwise and transversal to enable connection at all sides and to enable that more cooling devises 14 can be interconnected. Unused cooling fluid inlets 12 or cooling fluid outlets 13 would then be blinded.

[0094] In this embodiment the cooling fluid is a glycol and water solution but in another embodiment the cooling fluid could be brine, water, ammonia, or another form of natural or artificial cooling fluid suitable for exchanging heat with the power modules 1 to cool the power modules 1. In this embodiment the cooling fluid is pressurized to a pressure around 500,000 pascal (5 bar) by means of a pump because the cooling fluid has to overcome the pressure drop in the system and because the cooling fluid in this embodiment is circulated through a dry cooling system comprising cooler, control valves and pipes and hoses. In another embodiment the cooling fluid could also or instead be cooled by means of a two-phase cooling system comprising a compressor, a condenser, an expansion valve and an evaporator. In another embodiment the cooling fluid could be pressurized to a lower pressure - such as 450,000, 350,000, 200,000 pascal or even lower - or the cooling fluid could be pressurized to a higher pressure - such as 600,000, 900,000, 1,200,000 pascal or even higher.

[0095] In this embodiment the power module 1 is cooled in the following way.

[0096] A cavity 2 is formed in the baseplate 3 along with baseplate connection means 9 - in this case in the form of threaded holes - along with cooling fluid channel 11, cooling fluid inlet 12 and cooling fluid outlet 13. Turbulation means 5 in the form of an independent turbulator 5 is then arranged in the cavity 2 (or turbulation means 5 could be formed integrally with the baseplate 3).

[0097] A connection surface 4 comprising a connection means area 7 at each of the baseplate connection means 9 is formed along with elevated intermediate areas 10 formed between the baseplate connection means 9 on opposite sides of the cavity 2.

[0098] The power modules 1 is then connected to the contact surface 4 by means of connection means 9, 22 which in this embodiment is bolts 22 extending through through-holes 22 in the power module 1 and into the threaded holes 9 in the baseplate 3 so that at the power module 1 is bend across the intermediate areas 10 and so that the power module 1 fully covers the cavity 2. During the connection process the power module 1 will in this embodiment only bend a little and therefore only be subject to elastic deformation but in another embodiment the power module 1 could also be subject to plastic deformation. Finally, a flow of cooling fluid is generated through the cooling fluid inlet 12, the cooling fluid channel 11, the cavity 2 and the cooling fluid outlet 13 to cool the power module 1.

[0099] Fig. 6 shows turbulating means 5, as seen from the front.

[0100] In this embodiment the turbulating means 5 comprises a turbulator middle area 20 arranged at the middle of the turbulator - which will be arranged at the middle of the cavity 2 when the turbulator 5 is arranged inside the cavity 2 - and a turbulator periphery area 21 arranged at a periphery of the turbulator 5 - which will be arranged at the periphery of the cavity 2 along the connection surface 4 when the turbulator 5 is arranged inside the cavity 2 - wherein the middle height MH of the turbulating means 5 at the turbulator middle area 20 is bigger than the periphery height PH of the turbulating means 5 at the turbulator periphery area 21, so that if the turbulator 5 is placed in a cavity 2 with a flat bottom surface 16 the chance of close and uniform proximity or contact between the entire overside of the turbulating means 5 and the underside of the bend and pre-tensioned power module 1 is increased.

[0101] Note that the thickness of the turbulator 5 at the turbulator middle area 20 is shown exaggerated in fig. 6 to better illustrated the turbulator design.

[0102] In this embodiment middle height MH is bigger than the periphery height PH by the same amount that the at the intermediate areas 10 are elevated in relation to the connection means areas 7 to compensate for the elevation of the underside of the power module 1 induced by being bend over the intermediate areas 10. In this way it is ensured that substantially the entire overside of the turbulating means 5 will be forced against the underside of the power module 1 to ensure efficient heat transfer. However, due to production tolerances and the fact that if intermediate areas 10 are formed in more than one direction - which would elevate the part of the power module 1 over the turbulator middle area 20 more in relation to the turbulator periphery area 21 that the height difference between the connection means areas 7 and the intermediate area - the height difference between the turbulator middle area 20 and the turbulator periphery area 21 could vary in relation to the height difference between the connection means areas 7 and the intermediate area 10 by + / - 10%, + / - 20%, + / - 35% or even more.

[0103] In this embodiment the turbulation means 5 are made from drawn aluminium sheet metal but in another embodiment the turbulation means 5 could also or instead be made through casting, milling, 3D printing or other and / or the turbulation means 5 could be made from cobber, stainless steel, brass, or another metal and / or the turbulation means could be made from a composite material, ceramic, plastic or other or any combination hereof.

[0104] The main function of the turbulation means 5 is to turn laminar flow of the cooling fluid flowing through the cavity 2 into turbulent flow, in that a turbulent flow will mix up the cooling fluid as it passes through the cavity 2 and thereby increase the contact with the turbulation means 5 and the power module 1, whereby the heat exchange is increased. It should be noted that turbulation means 5 can be made with a multitude of designs - e.g. with labyrinth channels, heat sink ribs or fins arranged in a pattern - such as herringbone, alternate directions, zig-zag or other -, coils, balls, twisted wire rod, as steel wool or other or any combination thereof.

[0105] Fig. 7 shows a cooling device 14 with a power module 1, as seen in an isometric view.

[0106] It should be noted that any reference to orientation - such as up, down, side, upwards, downwards, top, bottom etc. - throughout this document refers to the cooling device 14 and the power module 1 during normal use where the baseplate 3 is arranged substantially horizontally and the power module 1 is placed on top of the baseplate 3 so that the underside of the power module 1 is cooled by cooling fluid flowing through the cavity 2 underneath the power module 1. In the foregoing, the invention is described in relation to specific embodiments of power modules 1, baseplates 3, turbulating means 5 and other as shown in the drawings, but it is readily understood by a person skilled in the art that the invention can be varied in numerous ways within the scope of the appended claims.

[0107] List

[0108] 1. Power module

[0109] 2. Cavity

[0110] 3. Baseplate

[0111] 4. Connection surface

[0112] 5. Turbulating means

[0113] 6. Gasket

[0114] 7. Connection means area

[0115] 8. Contact face of power module

[0116] 9. Baseplate connection means

[0117] 10. Intermediate area

[0118] 11. Cooling fluid channel

[0119] 12. Cooling fluid inlet

[0120] 13. Cooling fluid outlet

[0121] 14. Cooling device

[0122] 15. Baseplate groove

[0123] 16. Bottom surface of cavity

[0124] 17. Power electronics

[0125] 18. Cavity middle area

[0126] 19. Cavity periphery area

[0127] 20. Turbulator middle area

[0128] 21. Turbulator periphery area

[0129] 22. Module connection means

[0130] 23. Top surface of baseplate MH. Middle height of turbulator PH. Periphery height of turbulator IH. Intermediate height

[0131] CD. Connection distance

Claims

Claims1. A cooling device (14) comprising a baseplate (3) having a cavity (2) extending from a connection surface (4) of said baseplate (3) and into said baseplate (3), wherein a cooling fluid channel (11) connects said cavity (2) with a cooling fluid inlet (12) and a cooling fluid outlet (13) of said baseplate (3), wherein said connection surface (4) comprises at least two baseplate connection means (9) arranged for connecting a power module (1) to said connection surface (4) at opposite ends of said connection surface (4), and wherein said cooling device (14) further comprises turbulating means (5) arranged in said cavity (2), and wherein said connection surface (4) comprises a connection means area (7) at each of said at least two baseplate connection means (9) and at least two intermediate areas (10) arranged between said at least two baseplate connection means (9) on opposite sides of said cavity (2) and wherein said at least two intermediate areas (10) are elevated in relation to said connection means areas (7) as seen in a direction perpendicular to said connection surface (4).

2. A cooling device (14) according to claim 1, wherein said cavity (2) comprises a bottom surface (16) having a cavity middle area (18) arranged at the middle of said bottom surface (16) and a cavity periphery area (19) arranged at a periphery of said bottom surface (16) and wherein said cavity middle area (18) is elevated in relation to said cavity periphery area (19) as seen in a direction perpendicular to said connection surface (4).

3. A cooling device (14) according to claim 2, wherein said cavity middle area (18) is elevated in relation to said cavity periphery area (19) by the same amount that said at least two intermediate areas (10) are elevated in relation to said connection means areas (7) + / - 50%, preferably + / - 40% and most preferred + / - 30%.

4. A cooling device (14) according to any of the preceding claims, wherein said turbulating means (5) comprises a turbulator middle area (20) arranged at the middleof said cavity (2) and a turbulator periphery area (21) arranged at a periphery of said cavity (2) along said connection surface (4) and wherein the middle height (MH) of said turbulating means (5) at said turbulator middle area (20) is bigger than the periphery height (PH) of said turbulating means (5) at said turbulator periphery area (21), wherein said middle height (MH) and said periphery height (PH) is measured in a direction perpendicular to said connection surface (4).

5. A cooling device (14) according to claim 4, wherein said middle height (MH) is bigger than said periphery height (PH) by the same amount said at least two intermediate areas (10) are elevated in relation to said connection means areas (7) + / - 50%, preferably + / - 40% and most preferred + / - 30%.

6. A cooling device (14) according to any of the preceding claims, wherein said turbulating means (5) are extending from a bottom surface (16) of said cavity (2) and at least up to said at least two intermediate areas (10).

7. A cooling device (14) according to any of the preceding claims, wherein said connection surface (4) is gradually elevated between said connection means areas (7) and said at least two intermediate areas (10).

8. A cooling device (14) according to any of the preceding claims, wherein a smooth height transition of said connection surface (4) is formed between said connection means areas (7) and said at least two intermediate areas (10).

9. A cooling device (14) according to any of the preceding claims, wherein said connection surface (4) comprises four baseplate connection means (9) describing a rectangle.

10. A cooling device (14) according to any of the preceding claims, wherein said at least two intermediate areas (10) are arranged in the middle between said at least two baseplate connection means (9) on opposite sides of said cavity (2).

11. A cooling device (14) according to any of the preceding claims, wherein said at least two intermediate areas (10) are elevated by an intermediate height (IH) in relation to said connection means areas (7), wherein said intermediate height (IH) is between 0.05% and 10%, preferably between 0.1% and 6%, and most preferred between 0.2 and 3% of the connection distance (CD) between said at least two baseplate connection means (9).

12. A cooling device (14) according to any of the preceding claims, wherein said cooling device (14) further comprises a power module (1) being connected to said connection surface (4).

13. A cooling device (14) according to claim 12, wherein said power module (1) is connected to said connection surface (4) by means of module connection means (22) of said power module (1) engaging said at least two baseplate connection means (9).

14. A cooling device (14) according to claim 11, wherein said module connection means (22) are arranged along a periphery of said power module (1).

15. A cooling device (14) according to claim 11 or 12, wherein said at least two module connection means (22) comprises bolts.

16. A cooling device (14) according to any of claims 11-13, wherein said power module (1) comprises heat generating power electronics (17).

17. A cooling device (14) according to any of claims 11-14, wherein said power module (1) fully covers said cavity (2).

18. A cooling device (14) according to any of the preceding claims, wherein said cooling device (14) further comprises a gasket (6) encircling said cavity (2).

19. A cooling device (14) according to claim 18, wherein said gasket (6) is arranged in a baseplate groove (15) in said connection surface (4).

20. A cooling device (14) according to any of the preceding claims, wherein said baseplate connection means (9) comprises threaded holes arranged in said connection surface (4) or threaded rods extending from said connection surface (4).

21. A cooling device (14) according to any of the preceding claims, wherein said baseplate (3) is made of metal.

22. A cooling device (14) according to claim 21, wherein said metal is aluminium.

23. A cooling device (14) according to any of the preceding claims, wherein said turbulating means (5) comprises a turbulator arranged as an independent unit in relation to said baseplate (3).

24. A method for cooling a power module (1), wherein said method comprises the steps of:• forming a cavity (2) in a baseplate (3) so that said cavity (2) is extending from a connection surface (4) of said baseplate (3) and into said baseplate (3),• forming at least two baseplate connection means (9) in said connection surface (4),• forming said connection surface (4) so that it comprises a connection means area (7) at each of said at least two baseplate connection means (9)• forming at least two intermediate areas (10) between said at least two baseplate connection means (9) on opposite sides of said cavity (2) and so that said at least two intermediate areas (10) are elevated in relation to said connection means areas (7) as seen in a direction perpendicular to said connection surface (4),• arranging turbulating means (5) in said cavity (2),• connecting said power module (1) to said connection surface (4) by means of said at least two baseplate connection means (9) so that at least a part of said power module (1) is bend across said at least two intermediate areas (10), and• generating a flow of cooling fluid through said cavity (2) to cool said power module (1).

25. A method according to claim 24, wherein said method further comprises the step of arranging a gasket (6) between said power module (1) and said baseplate (3).

26. A method according to claim 24 or 25, wherein said cooling fluid is pressurized to a pressure between 200,000 and 1,500,000 pascal, preferably at between 250,000 and 1,000,000 pascal, and most preferred between 300,000 and 800,000 pascal.

27. A method according to any of claims 24-26, wherein said power module (1) is connected tightly to said baseplate (3).

28. A method according to any of claims 24-27, wherein said power module (1) is cooled by means of a cooling device (14) according to any of claims 1-23.

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