Patent Grant
9251947
The object of the invention is a liquid cooling arrangement of an inductive component and a method for manufacturing the aforementioned inductive component as defined in the claims.
Liquid cooling has brought numerous advantages to power electronics, such as reduced temperatures and a smaller size. However, the implementation of liquid cooling has mainly focused on the cooling of power semiconductors, and not many very effective solutions have been developed for the liquid cooling of inductive components. Inductive components, such as filters, transformers and chokes, are composed of, among other things, a core and one or more windings, in both of which losses are created that must be cooled.
In the most common inductive components, various heat exchangers are placed only on the surface. A drawback in this methodology, however, is that not very effective cooling is achieved, but instead the structure is large in size and does not cool evenly. In this case hot spots remain in the structure and a large part of the losses is transferred to the surrounding air, which detrimentally heats the component cubicle, among other things, and the losses are thus not effectively transferred into the cooling liquid.
The aim of this invention is to eliminate the aforementioned drawbacks and to achieve a simple, advantageous and efficient liquid cooling structure of inductive components and also a method for manufacturing a liquid cooling structure for inductive components. The cooling solution according to the invention can be used for cooling all types of inductive components, but it is particularly well suited to the cooling of chokes.
Other inventive embodiments may also be discussed in the descriptive section of the present application. The inventive content of the application can also be defined differently than in the claims presented below. In addition, it can be stated that at least some of the features of the subordinate claims can at least in some suitable situations be deemed to be inventive in their own right.
One advantage, among others, of the solution according to the invention is that the loss produced in the core of the inductive component can be efficiently transferred into the cooling liquid. Another advantage is that the losses of the winding can be transferred into the cooling liquid also via the cores such that the losses are conducted from the winding directly into the cores through an insulation. A further advantage is that the solution according to the invention improves the efficiency of the liquid cooling of inductive components.
In the following, the invention will be described in greater detail by the aid of some examples of its embodiments with reference to the attached drawings, wherein
Alternatively the winding can also be of the foil type, in which case liquid cooling is integrated into each or only into some of the gaps between the foil layers. A heat exchanger can be installed vertically between the foil layers or a liquid pouch that adapts along with the foil winding is installed on top of the winding foil before the winding, which liquid pouch remains between the foil winding layers and in which liquid pouch the cooling liquid flows. Alternatively the liquid cooling could also flow in ducts built inside or on the surface of the foil. The losses of the winding 3 can also be transferred into the liquid via the cores 1 such that the losses are conducted from the winding 3 into the cores 1 e.g. through an insulation. Correspondingly, the core 1 can be cooled into the winding 3. The cooling options presented above can be freely combined.
It is practical to manufacture the core 1 of the inductive component from a number of smaller structural elements 7 that are essentially mainly similar to each other. Metallurgical powder is particularly well suited to the manufacturing of this type of structural element 7. A structural element manufactured from metallurgical powder, i.e. metal powder, operates electrically just as well in all dimensional directions, i.e. in the X, Y and Z directions, in which case it can be installed three-dimensionally in all directions. The structure is appreciably better than a structure made of laminate that works well in only one or two-dimensional directions and badly in the third dimensional direction and therefore causes additional losses. The structural element 7 is preferably manufactured by compression from insulated metal powder. An additional advantage of a core pressed from insulated metal powder is that due to its internal insulation it withstands corrosion better than a core made of laminate.
By means of the groove 8, a duct is formed for a liquid cooling pipe, if necessary, by placing two structural elements 7 against each other such that the grooves 8 are also placed against each other. It is easier to install the liquid cooling pipe into this type of structure than into a hole 9. The duct formed by the grooves 8 is preferably larger to the extent of a suitable tolerance than the outside diameter of the liquid cooling pipe. The space between the pipe and the wall of the groove 8 is preferably filled with a thermally conductive paste. The task of the thermal paste is to ensure the transfer of heat from the core 1 into the liquid cooling pipe, and also to even out the effect of mechanical tolerances and thermal expansion. This type of thermal paste also forms an electrically insulating layer between the core 1 and the pipe, which reduces the formation of undesired currents into the structure.
From the viewpoint of assembly, one preferred structure of the core is such that the cooling liquid circulation with its pipes and end flanges is manufactured first and the cores are assembled from small structural elements 7 that comprise a suitable groove 8 ready for liquid pipes, by joining the structural elements 7 around the ready piping.
Methods for making joints in the ends of the pipes 10 are, among others: connection by means of threads, gluing, soldering, pressing, the utilization of thermal expansion, expansion, i.e. swaging, welding and laser welding, as well as metallic and plastic cast pieces and also pipe connectors such as a pipe beading.
In
The structural elements 7 used in this solution, e.g. presented in
From the viewpoint of assembly, it is preferable to use the core structure presented in
Correspondingly, the structural element 7b is flat on all its surfaces. In addition, the structural element 7 is the largest in its cross-section, and the structural elements 7a and 7b are correspondingly smaller in their cross-section than the structural element 7. The larger structural elements 7 are used e.g. in the corners of the core structure and in places into which the structural elements 7 are easy to install. On the other hand, the smaller structural elements 7a and 7b are used in the final phase of the assembly of the core, in which phase there is less space around the pipes 10 and the structural elements must be installed perhaps from unfavorable directions.
The idea of assembling the core is that the cross-sectionally small and flat structural element 7b is placed into its position by suitably fitting it last of all. In this case the structural elements 7 and 7a provided with a groove 8 can be installed more freely into their positions from the best possible direction. This is important so that the thermal paste placed into the grooves 8 of the structural elements 7 and 7a stays as well as possible in place when installing a structural element 7a and 7 into its position. If the structural elements 7 of the core that are provided with a groove 8 were fitted in the final phase of the assembly into their positions in the direction of the pipes 10, the thermal paste would easily be wiped out of the grooves 8. Also, the thermal paste and the glue in the structural elements 7, 7a, 7b of the core would foul the pipe 10 and particularly the end of the pipe 10, when making of a joint to the end would be difficult.
The cooling pipes passing through the structure of the core can be separate pipes 10 or they can be manufactured directly into the structural elements 7 of the core 1. The pipes manufactured into the structural elements 7 can be manufactured as a so-called “high-porosity” structure, i.e. as a porous structure through which liquid permeates. The porous material can only be on the edges of the pipes or on the whole area of a pipe. This type of high-porosity structure efficiently transfers heat from the core 1 into the cooling liquid, because the flow inside it is easily rotational i.e. turbulent. Likewise the inner surface area of the pipe made from porous material, i.e. the surface area contributing to heat transfer, is large. When using separate pipes 10 they can be provided with separate turbulators, such as e.g. with spirals, which make a laminar flow turbulent even at a low flow speed, in which case the transfer of heat from the pipe 10 into the cooling liquid becomes more efficient. This type of effect is also achieved with separate shapes, such as tubercles or rifles, made on the inner surface of the pipes 10. It is best to coat a high-porosity structure with a coating that prevents corrosion, such as with an aluminium or nickel coating. Separate pipes 10, the aforementioned high-porosity structure or other duct structures form, either together or separately, the liquid duct structure 2 of the core 1 presented in
Any magnetic material whatsoever can be used as the core material. It is, however, preferable to use core material that is based on metal powder instead of a laminate-based material because it keeps its inductance up to a higher frequency than silicon steel laminate.
In the choke according to the invention, there can be liquid cooling pipes 10 both in the horizontal beams and in the vertical pillars of the core 1. The horizontal beams and the vertical pillars are defined such that when the choke is in its basic position on the base at least one horizontal beam is in the bottom part of the choke and one horizontal beam is in the top part of the choke. In a 3-phase choke, three vertical pillars that are essentially perpendicular with respect to the horizontal beams are between the horizontal beams, around which vertical pillars the windings are wound. In practice, the choke can be in such a position that the horizontal beams are not horizontal and the vertical pillars are not vertical, but for the sake of simplicity these elements are hereinafter referred to as horizontal beams and vertical pillars.
When the pipes 10 are installed into suitable locations, it is possible to get the pipes 10 that are in the horizontal beams and vertical beams to pass overlapping each other in the finished choke. U-shaped pipes are used in the vertical pillars and in the horizontal beams, in which case the joints are placed at the same end and there are fewer of them than if, instead of U-shaped pipes, there were two straight, i.e. I-shaped, pipes with connectors at both ends. It is advantageous to make the core 1 from a number of smaller parts that settle in connection with each other or overlapping each other in the assembly phase.
The winding that will go around the core can be made e.g. with busbars, with wire, with planar connected plates, with cables or with conductor foil. Especially when using cables, they can be efficiently pressed tightly into the cores 1, in which case they cool via the cores 1 into the cooling liquid. When using cables, also more than one winding turn can easily be produced and by placing a suitable quantity of cables in parallel a sufficient conductor surface area for each current value can be obtained. In addition, the insulation of the cables takes care of the insulation of electrical parts, in which case disruptive discharge problems caused by accretion typical to busbar solutions are not able to occur. In this way e.g. a dUdT filter can be made such that liquid cooling is integrated into the core 1 and the winding 3 is made with cables, which are cooled against the core 1 that is cooled with liquid.
When using the essentially flat winding layers 4 presented in
When the liquid heat exchangers 5 of the structure according to
The winding plates 15 can be of different lengths and they can be manufactured by water cutting or laser cutting, in a plate machining center or by punching with a follow-on tool. Manufacturing the plates from aluminium, in particular, is cost-effective. In addition, the material best suited for each specific environmental condition can be selected. Additionally, the winding plates 15 can be connected to each other e.g. by screwing, riveting, cold soldering, pressing or welding.
At its simplest a liquid cooling heat exchanger or a liquid cooling element 16 can be an object 21 essentially of rectangular shape, as presented sectioned at the end and side in
Individual winding plates can also be composed of a number of thinner plates stacked one on top of the other. This may need to be done due to, among other things, the limitations of manufacturing technology. Also from the viewpoint of high-frequency operation it is advantageous to make a winding layer from a number of thinner plates, because with high frequencies current flows only on the surface of the plates and a number of thinner plates have a larger combined surface than one thick plate. It is possible to line this type of a filter completely with thermal insulation, in which case the heat to be transferred to the surrounding air can be almost completely eliminated.
These types of manufacturing methods can be used to manufacture transformers, chokes and filters. The capacitors of filters can also be cooled, e.g. into cooling elements 5 that are integrated into the windings, which elements are also called “cold plates”. For this purpose different shapings or additional parts can be made for the cooling elements 5. Chokes made with this technology can also be placed one on top of the other, in which case they are fitted to use shared liquid cooling pipes 10. Such a structural solution can be e.g. an LCL filter that has two chokes. The solution according to the invention is suited to the manufacturing of both single-phase and polyphase chokes.
It is also possible to perform a so-called “hybrid cooling”, in which the core is cooled with integrated liquid cooling and the winding is made by stacking the plates one on top of the other and leaving a thin gap between them for the passage of cooling air. Air is blown into the winding with a fan. Thus extremely effective cooling is brought about, because both cooling liquid and cooling air are generally available in all installation sites.
The first end visible in
Liquid cooling elements 16 are placed at suitable points between the winding layers 25, the winding plates 15j below and above which liquid cooling elements comprise at the first end additional protrusions 26 pointing towards the center line of the plates, which protrusions are bent obliquely either upwards or downwards so that the winding plate layers 25 can be connected to each other over the liquid cooling elements 16. In this case the protrusions 26 in the winding plates of the winding layer 25 that are above the liquid cooling element 16 are bent downwards and the protrusions 26 in the winding plates of the winding layer 25 that are below the liquid cooling element 16 are bent upwards. The connection is made by connecting the downward-bent and the upward-bent protrusions 26 to each other with fixing means, such as rivets or bolts. Bypassing the liquid cooling elements 16 can also be implemented in other ways, such as by placing a conductor piece at this point of the winding, which piece is of the same thickness as the liquid cooling element.
The ends of the liquid cooling elements 16 comprise branch couplings 28 of the liquid ducts, by means of which branch couplings the liquid cooling elements are connected to each other for implementing the circulation of cooling liquid. For the sake of clarity, the cooling tubes connected to the branch couplings 28 are not shown in
The compression structure of the winding 3 comprises a mechanism, such as e.g. spring washers 31 in connection with each bar 29, 30, which mechanism eliminates the effect of thermal expansion on the compression of the contacts. In the liquid cooling elements 5, the liquid flows into the winding structure via a connector 33 in the first end of the element, turns around at the other end of the winding element and comes back out from the connector 34 that is in the first end of the winding element, in which case all the external liquid connections 33, 34 of the liquid cooling element 5 are at the same end, i.e. at the first end of the structure. In this case the cooling tubes connected to the structure take up space only at the first end of the structure. The interface of layers comprises preferably thermal paste for improving the transfer of heat. Preferably e.g. SIL-PAD insulation material is used for the insulation of the liquid cooling elements 5.
It is advantageous to assemble the core structure 1 such that suitable subassemblies are assembled first, which subassemblies are e.g. vertical poles or pillars 35, a partially-assembled top horizontal beam 36 and a partially-assembled bottom horizontal beam 37. These subassemblies are presented as detached in
The core 1 of a three-phase choke comprises three vertical pillars 35 assembled from small structural elements 7 and/or 7a and/or 7b of different shapes and different sizes, as well as a top horizontal beam 36 and a bottom horizontal beam 37 assembled from the structural elements 7 and/or 7a and/or 7b, all of which comprise their own separate cooling liquid circulations. Additionally, the cooling pipes 10 of the cooling liquid circulations are fitted into the vertical pillars 35 and into both the top horizontal beams 36 and the bottom horizontal beams 37 such that the cooling liquid pipes 10 pass in the vertical pillars 35 and in both the top horizontal beams 36 and the bottom horizontal beams 37 crosswise and overlapping each other. Separate cooling liquid circulations facilitate the assembly of the choke.
The horizontal beams 36 and 37 consist of even smaller subassemblies. In this case the bottom horizontal beam 37 comprises two neck parts 38 on the side, which contain a cooling pipe 10, and two rectangularly-shaped intermediate beam parts 39, which intermediate beam parts 39 are placed between the neck parts 38 in the finished assembly. Correspondingly, the top horizontal beam 36 comprises a basic beam 40 as well as additional structural parts to be installed in the final phase of installation around the cooling pipes 10 of the vertical pillars 35, which additional structural parts are at least suitably sized and shaped structural elements 7 as well as structural elements 7a and 7b that are smaller than the structural elements 7, of which the structural elements 7 and 7a comprise a groove 8 for the cooling pipe, but the structural elements 7b are flat on all their sides.
The liquid pipes 10 in the vertical pillars 35 form a U-bend in the bottom part of the vertical pillars 35. When performing the assembly, the different subassemblies settle overlapping each other to form a fixed, uniform structure when the parts are placed into their position and the structure is pressed together. The subassemblies are built up like a brick wall, in which case the structure becomes sturdy. The core structure comprises vertical and horizontal liquid pipes 10 that pass overlapping each other. The liquid pipes 10 of the vertical pillars 35 can be put through the top horizontal beam 36 when some of the structural elements are initially left out of the top horizontal beam 36, in which case the basic beam 40 of the top beam 36 comprises apertures 47 at its ends and apertures 48 in the centre for the lead-ins of the pipes 10 of the vertical pillars 35. Only when the pipes 10 of the vertical pillars 35 have been put through the apertures 47 and 48 are the smaller structural elements 7, 7a and 7b placed in their positions in the apertures 47 and 48 around the pipes.
In this case e.g. a smaller structural element 7a is carefully threaded between the pipe 10 and the closed end of the aperture 47 in the basic beam 40, which aperture is open at one of its ends, which structural element 7a contains thermal paste in the groove 8 that is on its side surface on the pipe side, and the surfaces of which structural element 7a that are intended to be glued contain glue. The structural element 7a is carefully threaded into its position downwards from above and at the same time the end of the pipe 10 is carefully bent towards the free end of the aperture 47, in which case the space between the closed end of the aperture 47 and the pipe 10 increases and the structural element 7a is easily brought into its position so that neither the thermal paste nor the glue stains the pipe 10. When the pipe 10 is released to return to its normal position, the pipe 10 settles into the groove 8 of the structural element 7a. After this a larger structural element 7, the groove 8 of which has been provided with thermal paste and the surfaces of which that are intended to be glued contain glue, is carefully pushed into the aperture 47 essentially in the horizontal direction from the open end of the aperture 47 and finally lowered onto the structural element below and pushed tight against the pipe 10. Thus the pipe 10 can be firmly enclosed between the structural elements 7 and 7a.
Correspondingly, the smaller structural elements 7a provided with a groove 8 are first threaded into the aperture 48 that is in the center of the basic beam 40, the length of which aperture 48 is greater than the combined length of two small structural elements 7a, around the pipe 10, the groove of which smaller structural elements contains thermal paste and the surfaces of which smaller structural elements that are intended to be glued contain glue. Threading of the small structural elements 7a occurs e.g. such that the structural elements 7a are first lowered downwards into the aperture 48 at a suitable horizontal distance from the surface of the pipe 10 and when the structural element 7a is almost at its destination in the vertical direction it is moved in the lateral direction tight against the pipe 10 such that the pipe 10 settles into the groove 8. This is also done in the same aperture 48 on the other side of the pipe 10. After this the structural pieces 7b, which function as filler pieces, are placed in the aperture 48, behind the structural pieces 7a. As many structural pieces 7b are placed into the aperture 48 as needed to fill the aperture 48 sufficiently.
The upper core structure 1 in
Correspondingly, the lower core structure 1 in
According to the invention it is advantageous in principle to use one material in the structural elements 7 forming the core structure 1, but if too high a temperature were to form in the center of the core, a part of the material in principle used is replaced with a lower-loss material in the center of the core structure 1. Since each structural element 7 is preferably of only one material, the replacement is implemented one structural element 7 at a time such that the centermost structural element or structural elements 7 is/are of a lower-loss material than the structural elements that are nearer the edge of the structure.
When the losses of all the structural elements 7 are 10 W, the temperatures of the structural elements in a certain operating situation settle so that the temperature in the cooling duct 2 is approx. 50°, in the edgemost structural element no. 1 approx. 80°, in the structural element no. 2 approx. 100°, and in the hottest, i.e. in the centermost structural element no. 3 approx. 110°. Correspondingly, the temperatures of the structural elements of the lower core structure 1 presented in
With the method according to the invention, an inductive component is manufactured e.g. as follows:
The core 1 of the inductive component is manufactured from a number of smaller structural elements 7, 7a, 7b that are essentially both different and similar to each other, which structural elements are assembled to form a packet of the size and shape of the core 1 designed for the application, e.g. such that subassemblies are made first, which are separately composed of e.g. vertical pillars 35, a top horizontal beam 36 and a bottom horizontal beam 37, and cooling liquid pipes 10 are placed in at least a part of the subassemblies before final assembly of the subassemblies into the core structure. Any magnetic material whatsoever can be used as the material of the structural elements 7, 7a, 7b. According to the invention, core material based on metal powder is used as the material. A structural element 7, 7a, 7b is manufactured e.g. from metal powder by pressing such that the structural element 7, 7a, 7b is pressed into an essentially rectangularly-shaped piece, in which all the sides are essentially right-angled. In connection with the pressing phase a groove 8 or hole 9 that passes in one direction through the structural element is also formed in the structural element 7, 7a for the use of the cooling liquid. The groove 8 in the structural element 7, 7a is cross-sectionally essentially e.g. semicircular, becoming a full circle when two structural elements 7 and/or 7a provided with a similar groove are placed against each other in the assembly phase of the core 1.
In the assembly phase of the core 1 of an inductive component, such as of a choke, the structural elements 7, 7a, 7b are placed consecutively one after the other and, if necessary, side-by-side and one on top of the other such that the grooves 8 of the structural elements 7, 7a in at least one direction form an essentially straight duct 2, 8a, extending essentially through the whole core 1, for the purpose of liquid cooling.
Correspondingly, in the assembly of the core 1 the structural elements 7b that have flat surfaces are placed essentially last in the core to be assembled, which structural elements are preferably smaller in their cross-section than the largest structural elements 7 that are provided with grooves 8.
Cooling liquid pipes 10 or corresponding pipe-like means are placed into the ducts 2, 8a formed in the assembly phase of the structural elements 7, 7a of the core 1. Thermal expansion is utilized, if necessary, in the installation such that the pipe 10 or corresponding pipe-like means is cooled before being placed into the duct 2, 8a. The tolerance-air gap between the pipe 10 and the duct 2, 8a is filled, if necessary, with a paste that conducts heat, such as with a 2-component paste. After this the pipes 10 that have been installed into the cores 1 are connected to each other to form a continuous liquid circulation by means of the end plates 11 provided with liquid ducting, and/or by means of connectors 33, 34 and/or tubes.
Another method to manufacture a liquid-cooled inductive component is to assemble the liquid circulation with pipes and possible end plates 11 first, after which the structural elements 7, 7a provided with semicircular grooves 8 are assembled around the finished piping to form a packet of the size and shape of the core 1 designed for the application.
To improve the efficiency of the cooling, the pipes 10 are provided, if necessary, with separate turbulators, such as e.g. with spirals or with corresponding means that produce a turbulent flow, such as tubercles or rifles, all of which are placed inside the pipes 10.
An aluminium profile 12 is used as a liquid cooling element, if necessary, in addition to or instead of the pipe 10. The structural elements 7 that form the core 1 are assembled consecutively to each other around the pipe part 13 in connection with the aluminium profile 12.
Yet another way to implement liquid cooling is to manufacture the cooling piping as parts directly inside the structural elements 7 in the pressing phase of the structural elements. This type of cooling piping is constructed as e.g. a so-called “high-porosity” structure, i.e. as a porous structure through which liquid permeates. The porous material is formed in the pressing phase either only on the edges of the pipes or on the whole area of a pipe. When the structural elements 7 manufactured in this way are assembled together to form one pack in the manufacturing phase of the core 1, the holes of the structural elements 7 set consecutively settle into a straight row one after another and thus form a ready pipe or duct. The surfaces of the structural elements 7 that touch each other are sealed to each other, e.g. by gluing, so that the cooling liquid is not able to leak from the gaps between the structural elements 7.
It is obvious to the person skilled in the art that different embodiments of the invention are not limited to the examples described above, but that they may be varied within the scope of the claims presented below.
It is also obvious to the person skilled in the art that the liquid cooling pipe can also pass in the area between the core and the winding, simultaneously cooling both of them.
It is further obvious to the person skilled in the art that the winding plates and the heat exchangers of the winding can also be round in shape. Round shapes and geometry can be used e.g. to limit the forces of short-circuited currents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20095772 | Jul 2009 | FI | national |
| 20096045 | Oct 2009 | FI | national |
| 20105397 | Apr 2010 | FI | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FI2010/050577 | 7/2/2010 | WO | 00 | 2/21/2012 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2011/004068 | 1/13/2011 | WO | A |
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