EP4736592A1

EP4736592A1 - Apparatus for cooling power electronics components

Info

Publication number: EP4736592A1
Application number: EP24831124.3A
Authority: EP
Inventors: Pekka SEPPÄLÄ
Original assignee: Msc Control Oy
Current assignee: Msc Control Oy
Priority date: 2023-06-27
Filing date: 2024-06-17
Publication date: 2026-05-06
Also published as: FI20237129A1; FI131923B1; WO2025003561A1

Abstract

The object of the invention is an apparatus for cooling non-planar and planar power electronic components, such as components containing magnetic circuits. The apparatus according to the invention comprises a housing (1) filled, with a dielectric cool ant (2) with a high thermal conductivity value into which the cooled components (K1) are immersed to cool them. Further, the apparatus comprises a cooling element (3) placed inside the housing, in its upper part in contact with the coolant (2) preferably cooled outside the apparatus, with separate closed fluid circulation (5a, b) to cool the element (3) and control the temperature of the coolant (2) inside the housing (1); and a heat-conducting cooling plate ( 4 ) closing the housing (1), arranged at the top of housing (1) as its lid above the cooling element (3) so that the cooling plate (4) is in contact with the coolant (2) and/or cooling element (3) to cool the planar components arranged on the outer surface of the cooling plate.

Description

Apparatus tor cooling power electronics components

The object of the invention is an apparatus as presented in the preamble to the independent claim directed thereto for the cooling of specifically power electronic compo-

A significant part of the weight, volume and cost of power converters and other components containing magnetic cir- cuits is due to transferring of heat losses created inside the converter components away from the apparatus, i.e. cooling the components. For this reason, in high-power power converters, it is cost-effective to maximize the proportion of liquid cooling and minimize the number of

>arts required for this.

Power converters contain components (e.g. power semicon- ductors) where the generated loss heat is directed to the planar highly heat-conducting surface of the component. However, the power converter has also components (e.g. magnetic circuits) where the heat loss is conducted in several directions and on surfaces of different shapes. For example, inductors generate heat three-dimensionally through non-planar surfaces, which makes it challenging to cool them using only its planar surfaces.

At present, in power electronics, devices containing mag- netic components (magnetic circuits) that generate heat through losses are typically cooled convectively by air- flow, either passively using various cooling fin solu- tions to increase the area of the cooling surface, or actively combining fans with the above. Devices with mag- netic components can be additionally cooled by immersing them in a non-conductive (dielectric) , but heat- conducting coolant, or using combinations of the above. These solutions typically require cooling fins on the outside surface of the device, which limits the use of the outside surface for other purposes, such as attaching accessories .

Publication EP 2 790 311 Al presents a converter solution wherein capacitive elements are immersed in a heat-con- ducting liquid. The solution is passively cooled with ribs outside the housing, "which can be further enhanced by using external fans. The publication focuses essen- tially on the structure of the cooled capacitive compo- nent in order to cool it efficiently.

Publication WO/2020/200523 presents a cooling solution for magnetic components of power electronics used to en- sure power supply to data centers, wherein components are embedded in a coolant. Vaporization and convective move- ment occur in the liquid heated by the components, cre- ating internal circulation of the liquid. The circulation is directed through a cooling element/heat sink, wherein its mass causes vapor condensation and fluid circulation. Power semiconductor components, such as thyristors or IGBT transistors, are attached on the cooling elements. However, according to the publication, the liquid is not actively cooled.

Further, publication US 2013/0122331 presents a solution suitable for cooling hybrid car battery cells, wherein the battery cells are placed in a housing and immersed in a heat-conducting liquid with which the housing is filled so that the cells are completely subsurface, but the housing is not completely filled. A cooling element is also placed inside the housing, which can be, for example, hydronic and with a purpose to cool the liquid in the housing. The purpose of the cooling element is to condense the boiling coolant for recirculation, and it has not been completely immersed in the coolant.

In turn, the publication SE 2030079 Al presents a liquid- tilled housing cooled by a cooling plate intended for a battery module. The cooling plate is placed on the bottom or sides of the housing.

Further, publication EP 4 093 170 Al presents a cooling plate immersed in liquid that cools the liquid in a tank. Components that require cooling are also embedded in the tank. In the solution, a forced flow with the help of pumps is used to provide a coolant flow.

The publication CN 107135632 describes an apparatus for cooling electronic components, in particular a printed circuit board and the components arranged on it. In the apparatus according to the invention, the circuit board and its components are arranged inside a housing, which is further filled with heat-conducting dielectric liquid to cool the components. The publication describes a cool- ing plate placed under the printed circuit board with a separate internal coolant circulation to cool the board. The housing is closed above with a plate with feedthroughs placed on it, means to fill the case with liquid, and a display for indicating the temperature. Further, accord- ing to an embodiment of the invention, the housing can be cooled by cooling elements arranged on its side walls, which may be equipped with fans and/or cooling fins.

All the above-mentioned prior art publications present attempts to cool heat-generating components with the help of liquid. However, the presented inventions are either inefficient or complex in their construction, causing unnecessary costs when applying them for cooling power electronic components. Furthermore, the above-mentioned cooling solutions only provide solutions for cooling com- ponents arranged inside the housing. In that case, for the cooling of components arranged outside the housing and/or on the surface of the housing of systems used in power electronics, separate cooling shall be provided.

Furthermore, it is well known to use different cooling plates when cooling planar components, either liquid- cooled or, for example, cooled by Peltier elements. When cooled with a Peltier element, one side of the element is cooled and the other is correspondingly heated, in which case additional arrangements are required to conduct heat away from the Peltier element itself.

Water-cooled cooling commonly uses cooling plate, which are typically assembled from two or more heat-conducting plates, wherein at least one plate has a machined fluid channel so that when the plates are joined together, the channel remains between the plates. In this case, an in- ternal channel is formed in the cooling plate for fluid circulation and cooling of the plate. In a fluid-circulating cooling plate that utilizes forced convection, the cooling capacity and efficiency can be reached at a fairly high level, but especially in applications that require a lot of cooling power, the heat profile formed by the channels on the cooled plate surface becomes a problem, as it causes temperature differences (thermal gradients) on the surface of the plate. In this case, if necessary, the cooling channels must be designed in such a way that temperature differences can be minimized, which in turn leads to more complex structures and, for example , in- creased machining times , which correspondingly increases costs . Ef ficient heat trans fer in the case of forced con- vection also requires a good flow, which sets its own requirements for cooling channel design and coolant sup- ply . Further, channels designed in this way are optimal for only one form of implementation, and as component pos itioning changes , the coo ling plate channel s must also be redesigned . In addition, thermal gradients that form in the plate in any case cause reliability problems es- pecial ly in metal cooling plates as the internally vary- ing thermal expansion of the pl ate causes strain parti c- ularly on the j oints between the plates .

The obj ective of the present invention is to provide a decisive improvement on the above-presented problems and thereby to raise essentially the available prior art of the field . In order to attain this obj ect ive , the inven- tion is principally characteri zed by what is presented in the characteri z ing part of the independent claim directed thereto .

The purpose of the apparatus according to the invention is to present a solution for cooling power electronic components of preferably free- form, such as cylindrical shaped, in particular magnetic components such as con- verters , inductors or trans formers , which uti l i zes a coolant cooled by a separate cooling element to cool the components by immersion cooling . Furthermore , the purpose of the apparatus according to the invention is to present a soluti on for cool ing the surface of the apparatus by means of a cooling plate and coolant for cooling compo- nents that are cooled through a planar surface and placed on the surface of the apparatus . o

In the cooling solution of the invention, non-planar ob- jects, such as magnetic circuits, are cooled by immersing them in a sealed housing filled with a non-conductive but heat-conducting liquid, i.e. immersion cooling. The tem- perature of the liquid is controlled by a separate cooling element placed inside the housing, which is thus in con- tact with the liquid, and which preferably has a separate closed circulation of liquid for its cooling. The coolant circulation of the cooling element is preferably carried out using equipment outside the housing.

A heat-conducting cooling plate is placed as a lid at the top of the liquid-filled housing, with which said cooling element inside the housing is placed in the immediate vicinity or contact with it. When components immersed in the liquid, such as magnetic circuits, generate heat in the coolant, it initiates a convective flow inside the housing, causing the warm liquid to tend to rise upwards, reaching the heat sink, which cools the warm liquid that has risen up, thus maintaining convective circulation.

The cooling element at the top cools the heated liquid. Further, the cooling element also cools the above-placed cooling plate, either by direct contact, in which case the neat is dissipated directly to the cooling plate, or by the coolant above the cooling element, where a heat- conducting thin layer of liquid acts as a medium for heat transfer between the cooling element and the cooling plate. In this case, the coolant provides convective heat transfer to the cooling plate, smoothing thermal gradi- ents both vertically to the cooling plate, and horizon- tally between the cooling element structures. The exter- nal part of the cooling plate can therefore be used to cool planar components without significant thermal gra- dients that would form in the plate.

In the cooling apparatus according to the invention, the components are designed to be separate, enabling easy arrangement of their maintenance and replacement if nec- essary. The components are not dependent on the compo- nents of the cooling system, allowing them to be replaced or serviced separately if necessary. Further, the compo- nents of the cooling apparatus, cooling element, coolant and cooling plate can be replaced independently of each other in a simple manner without expensive machining.

In the subsequent description, the invention is illus- trated in detail while referring to the accompanying drawings, where :

Figures la and lb present certain embodiments of cooling apparatus according to the invention in perspective view, and present an embodiment of the cooling apparatus ac- cording to the invention as a cross-sectional view. invention is an apparatus for cooling power electronics components, which comprises a housing 1 filled with coolant 2, at least one cooling element 3 and cooling plate 4. With reference to Figures la and lb, the housing 1 is a free-form hollow structure with a solid bottom and sidewalls to store liquid 2 inside it. The purpose of the housing 1 is, on the one hand, to act as a basin for coolant 2, and on the other hand, to act as a housing for components KI to be cooled. Further, the housing 1 is preferably an open body at the top, which is closed with the cooling plate 4. Said cooling plate 4 is a most preferably planar plate of high thermal conduc- tivity material, which closes housing 1 at its top, wherein housing 1 and cooling plate 4 form a sealed ves- sel. The cooled components KI, such as the magnetic cir- cuits used in power electronics converters, are arranged permanently and/or detachably in the interior of the housing as required by the current use, and housing 1 is filled with coolant 2 so that the cooled components KI are completely or partially covered by coolant 2, and cooling element 3 and/or cooling plate 4 are in contact with the coolant. The coolant 2 is a non-conductive (di- electric) material with high thermal conductivity, such as transformer oil, electronic fluid, or similar liquid suitable for submersible cooling, to enable heat transfer between components KI, cooling element 3 and cooling plate 4. The purpose of the coolant 2 is, on the one hand, to enable heat transfer between components KI and cooling element 3, and on the other hand, to enable convective heat transfer between cooling element 3 and cooling plate 4. Further, the coolant 2 smoothes out the thermal gra- dients between the structures of the cooling element, allowing a smoother thermal profile in the cooling plate.

Cooling element 3 is a tubular body, with a larger outer cross-sectional diameter than the inner diameter, made of high thermal conductivity material, preferably shaped in a serpentine shape in order to increase the cooling area. In the apparatus according to the invention, the cooling element 3 is arranged in the space inside housing 1 in the immediate vicinity of the cooling plate 4 at a dis- tance s from it or in heat-conducting contact with it, so that the horizontal plane formed by the cooling element 3 is parallel to the plane formed by the base of the cool ing plate 4 . Further, preferably for the outer sur- face area within the hous ing 1 , the cooling element 3 and cool ing plate 4 are arranged in contact wi th the coo lant 2 to cool the cooling plate 4 through coolant 2 and the heat trans fer feature it provides . The internal space of the cooling element 3 has a separate , externally con- trolled coo lant circulation 5a, b . In thi s case , the coolant supply 5a inside the cooling element 3 is cooled by an arrangement outside the apparatus , such as a sepa- rate radiator, where the coolant circulation 5b that has circulated in coo ling element 3 and warmed up is further fed back for cooling . In this case , the temperature of the element 3 is independently adj usted according to the cooling power required by the apparatus of to the inven- tion at any given time . The feedthroughs of the liquid circulation f lows 5 a, b entering in and out of the cool- ing element 3 are arranged liquid-proof , with particular reference to figure la, through the surface S above the cool ing plate 4 and/or through a wall W of housing 1 with reference to figure 2 .

As a preferred embodiment of the invention, components K2 that are cooled through a planar surface , such as tran- sistors , thyristors or similar used in power electronics , or circuit boards or similar platforms to which the com- ponents to be cooled are attached , are arranged on the outer surface of the cooling plate 4 to cool them through the outer surface of the housing .

As a preferred embodiment of the invention, the housing 1 is made of metal , plastic, composite or similar material according to the specmc use so that it can be tilled with cool ant 2 without leaking out . Furthermore , it i s possible to neat insulate the housing from its external

As a preferred embodiment of the invention, the coo ling element 3 is positioned in the internal space of the housing 1 in its upper part and completely in the coolant 2 to cool the components KI as the coolant heated by them ri ses convectively due to the density di f ference to the upper part of housing 1 for cooling . Furthermore , the cooled coolant 2 flows convectively inside the housing downwards , cooling components KI .

As a preferred embodiment of the invention, drain valves are arranged preferably at the lower part and/or bottom of the housing 1 to drain coolant 2 from housing 1 and/or a precipitate cup to coll ect any precipitate that may be formed by components KI and/or cool ant 2 .

As a preferred embodiment of the invention, a forced con vection i s created to coolant 2 to increase its f low, wherein said forced convect ion is created using external equipment , such as a pump or similar, with the necessary connections to housing 1 to circulate coolant 2 . Further, as a preferred embodiment of the invent ion, lamellas , or similar structures , such as proj ections and indentations , are arranged in housing 1 to contro l and/or manage the internal convective f lows in hous ing 1 . Furthermore, as a preferred embodiment of the invention, fixed and/or monolithic protruding parts are arranged in cooling plate 4 to enhance heat trans fer and increase and/or improve f luid contact so that proj ections such as fl anges or la- mellas are directed in the internal space of the housing towards the lower part of housing 1 deeper into coolant 2 . Further, as a preferred embodiment of the invention, me- chanical fastening structures for components KI are ar- ranged insi de the housing 1 in order to attach them per- manent ly and/or detachably in the housing 1 .

As a preferred embodiment of the invention, the parts of the apparatus according to the invention, housing 1 , cooling plate 4 , cooling element 3 , components KI and/or coolant 2 are arranged to be replaced independently with- out di sassembl ing the entire apparatus .

As a further preferred embodiment of the invent ion, a safety valve or equivalent arrangement is arranged on the outer wall or bottom of housing 1 or on the cooling plate closing the enclosure or at the j unction of the said parts in order to equal ize the pressure in hous ing 1 to prevent the pressure increase in case temperature rises in the event of overheating and/or failure of the apparatus . Further, as a preferred embodiment of the invention, ap- propriate valves , such as check valves or simi lar, are arranged in housing 1 and/or cooling plate 4 for filling and/or topping up coolant 2 .

As a preferred embodiment of the invention, the cooling plate 4 that closes the housing 1 is attached to the upper edge of the s ide wall s W of the enclosure by liquid-tight soldering, welding, gluing, threading and/or mechanical or electromechanical connections such as clamps , bolt screws , mounting j aws or simi lar .

As a preferred embodiment of the invention, the cooling element 3 is integrated into the cooling plate 4 in such a way that the cool ing element 3 is fixed to the surface of cooling plate 4 by a highly heat-conducting process such as soldering, welding and/or gluing so that cooling element 3 and cool ing plate are in fixed contact with each other to conduct heat between cool ing element 3 and cooling plate 4 , wherein the distance s between cooling element and cooling plate 4 is essentially zero . Further- more , it is possibl e to arrange the cool ing element with suitable clips in the immediate vicinity of cooling plate 4 in distance s so that coolant 2 can flow between element

3 and plate 4 .

It is obvious that the invention limited to the embodiment described or explained above , but may, within the framework of the basic idea of the invention, be modi fied depending on the circumstances by using the most appropriate means of fastening in the method for the housing 1 and the coo ling plate 4 . The basic idea of the invent ion is to arrange the housing 1 with a lid filled with the coolant 2 , inside which the cooling element 3 and components KI are immersed in the coolant , wherein the cooling element 3 cools the l iquid 2 and thus compo- nents KI and cool ing plate 4 . It i s clear that the mutual connections between the housing 1 , cooling element 3 and cooling plate 4 and their selected distances using brack- ets can be implemented in various ways , including men- tioned parts fully or partial ly integrated with each other by mechanical fastening structures . In addit ion , the housing 1 can be implemented with separate walls and/or a removable base part , while maintaining fluid proofness . Further, to the coolant 2 within hous ing 1 , it is poss ible to arrange forced convection to enhance heat trans fer with an external device or by taking advantage of various lamellas inside the housing to control the flow . It i s possible to implement the supply of the coolant from different parts of the housing 1 or, re- spectively, from different points on the cooling plate 4.

In addition, the size, shape and outer and/or inner di- ameter of the cooling element ran be varied according to the specific purpose or material choices within the framework of the basic idea of the invention.

Claims

Claim

1. An apparatus for cooling components, such as power electronic components containing magnetic circuits, com- prising a housing (1) filled with a dielectric coolant (2) with a high thermal conductivity value, such as trans- former oil, electronic fluid or similar submersible cool- ing liquid in which the cooled components (KI) are im- mersed in order to cool them, the apparatus further com- prising, a separate cooling element (3) placed inside the housing (1) , at the upper part of it, in contact with the coolant (2) , said cooling element (3) having preferably a separate closed fluid circulation (5a, 5b) cooled out- side the apparatus to cool the element (3) and control the temperature of the coolant (2) inside the housing (1) , characterized in that the apparatus further com- prises :

- a cooling plate (4) manufactured of a high thermal conductivity material, said cooling plate (4) ar- ranged at the top of the housing (1) filled with coolant as its lid in a liquid-proof manner above said separate cooling element (3) , wherein the cooling plate (4) is in contact with the coolant (2) or cool- ing element (3) and the coolant,

- components (K2) cooled through a planar surface that are arranged on the surface of the cooling plate out-

:er immediate t it e from it or contact with it in a heat-conducting manner so that the horizontal plane formed by the cooling element (3) is parallel to the plane formed by the base surface of the cooling plate (4) , to cool the cooling plate (4) by the influence of the cooling element (3) and the coolant (2) , and to cool components (K2) cooled through a planar sur- face being arranged on the outer surface of the cooling plate (4) .

2. The apparatus according to claim 1, characterized in that the coolant circulation (5a, 5b) of the internal cooling element (3) of the housing (1) is provided by equipment outside the housing (1) in order to inde- pendently control the temperature of the element (3) .

3. The apparatus according to claim 1 or 2, character- ized in that the housing (1) is partially or fully ther- mally insulated in its external parts.

4. The apparatus according to any of the preceding claims 1-3, characterized in that the cooling plate (4) is preferably a planar plate made of a material with a high thermal conductivity value, such as metal.

The apparatus according to any of the preceding claims 1-4, characterized in that the cooling element (3) is a tubular body made of high thermal conductivity ma- terial, preferably of a serpentine shape in order to in- crease the cooling area.

6. The apparatus according to any of the preceding claims 1-5, characterized in that the cooled components (KI) , such as magnetic circuits, are arranged detachably in the interior of the housing.

7. The apparatus according to any of the preceding claims 1-6, characterized in that the components (K2) cooled through a planar surface and arranged on the outer surface of the cooling plate (4) are transistors, thy- ristors or similar used in power electronics and/or cir- cuit boards or similar substrates to which the components (K2) to be cooled are attached in order to cool them.

8. The apparatus according to any ot the preceding claims 1-7, characterized in that the housing (1) is made of metal, plastic, composite, and/or similar material t hold the coolant (2) .

9. The apparatus according to claim 1-8, characterized in that the lower part and/or bottom of the housing (1) is preferably fitted with a precipitate bowl in order to collect any precipitate potentially formed from compo- nents (KI) and/or coolant (2) .

10. The apparatus according to any of the preceding claims 1-9, characterized in that the apparatus comprises an external pump or similar apparatus for the creation of forced convection in the coolant (2) inside the housing

(1) •

11. The apparatus according to any of the preceding claims 1-10, characterized in that lamellas or similar structures, such as projections and indentations to en- hance neat transfer by controlling and/or controlling convective flows inside the housing (1) are arranged in connection with the internal space of the housing (1) and/or the cooling plate (4) .

12. The apparatus according to any of the preceding claims 1-11, characterized in that mounting structures are arranged in the internal space of the housing (1) for the components (KI) , the cooling plate (4) and cooling element (3) for their fixed and/or removable attachment in the housing (1) in order to replace them independently.

13. The apparatus according to any of the preceding claims 1-12, characterized in that a safety valve or equivalent arrangement is arranged in the housing (1) and/or cooling plate (4) to equalize the pressure in the housing (1) to prevent the pressure increase to an ex- cessive level due to temperature rise in the event of overheating and/or failure of the apparatus.

14. The apparatus according to any of the preceding claims 1-13, characterized in that appropriate valves, such as check valves or equivalent, are arranged in the housing (1) and/or the cooling plate (4) to add and/or reduce the coolant (2) .

15. The apparatus according to any of the preceding claims 1-14, characterized in that the cooling element

(3) is integrated into the surface of the cooling plate

(4) in fixed manner by a highly thermally conductive pro- cess such as soldering, welding and/or gluing, wherein the cooling element (3) and cooling plate (4) are in fixed contact with each other in order to conduct heat between the cooling element (3) and the cooling plate (4) ; or with suitable clips in the immediate vicinity of the cooling plate (4) at such a distance (s) that the coolant (2) can flow between the element (3) and the cooling plate