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(11) | EP 4 145 474 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | COOLED ELECTRICAL ASSEMBLY COMPRISING CHOKE COIL |
| (57) A cooled electrical assembly comprising at least one choke coil (2) having a plurality
of coil turns wound around a choke centre line, a liquid cooling element (4) adapted
for cooling the at least one choke coil (2), the liquid cooling element (4) having
a first cooling surface (41) that is in heat conducting connection with a first outer
surface area (21) of the at least one choke coil (2). The cooled electrical assembly
comprises at least one a heat conduction element (6) that is in heat conducting connection
with the first cooling surface (41) of the liquid cooling element (4), and with a
second outer surface area (22) of the at least one choke coil (2) located on an opposite
side of the choke centre line than the first outer surface area (21).
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FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION
[0002] It is known in the art to cool a choke coil with a liquid cooling element surrounding the choke coil and/or extending inside the choke coil.
[0003] One of the problems associated with the above arrangement is that a required liquid cooling system is complicated, and comprises at least one coolant connection for each choke coil.
BRIEF DESCRIPTION OF THE INVENTION
[0004] An object of the present invention is to provide a cooled electrical assembly so as to solve the above problems. The objects of the invention are achieved by a cooled electrical assembly which is characterized by what is stated in the independent claim. The preferred embodiments of the invention are disclosed in the dependent claims.
[0005] The invention is based on the idea of providing a cooled electrical assembly with a heat conduction element that is adapted to conduct heat from an outer surface of a choke coil to a liquid cooling element. The heat conduction element is a passive cooling element which does not comprise an inlet and outlet for coolant flow.
[0006] An advantage of the cooled electrical assembly of the invention is that the cooling system is simple yet efficient. Since the heat conduction element is a passive cooling element, there are no coolant connections that could leak in the heat conduction element. Despite the passive structure of the heat conduction element, its cooling capacity is great due to its heat conductive connection with both the outer surface of the choke coil and the liquid cooling element.
[0007] In an embodiment, a cooled electrical assembly comprises a liquid cooling element, a plurality of choke coils and a semiconductor switch device such that the liquid cooling element is adapted to cool both the semiconductor switch device and the plurality of choke coils. In said embodiment, using the liquid cooling element for cooling of the plurality of choke coils does not require any additional coolant connections compared to a situation where the liquid cooling element is adapted to cool exclusively the semiconductor switch device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which
Figure 1 shows a cooled electrical assembly according to an embodiment of the invention;
Figure 2 shows the cooled electrical assembly of Figure 1 from a direction parallel to choke centre lines of choke coils of the cooled electrical assembly;
Figure 3 shows the cooled electrical assembly of Figure 1 from a direction perpendicular to the choke centre lines of the choke coils of the cooled electrical assembly;
Figure 4 shows the cooled electrical assembly of Figure 1 in a disassembled state;
Figure 5 shows the disassembled cooled electrical assembly of Figure 4 from a direction parallel to the choke centre lines of the choke coils of the cooled electrical assembly; and
Figure 6 shows a choke coil of the cooled electrical assembly of Figure 1.
DETAILED DESCRIPTION OF THE INVENTION
[0009] Figure 1 shows a cooled electrical assembly comprising three choke coils 2, a liquid cooling element 4, three heat conduction elements 6, an insulating system, a pressing system, and an electrical device 101. Each of the choke coils 2 has a plurality of coil turns wound around a choke centre line. The liquid cooling element 4 is adapted for cooling the choke coils 2, and has a first cooling surface 41 that is in heat conducting connection with a first outer surface area 21 of each choke coil 2.
[0010] The choke coils 2 are identical with each other. The first cooling surface 41 of the liquid cooling element 4 is a planar surface. The choke centre line of each choke coil 2 extends linearly, and is parallel to the first cooling surface 41 of the liquid cooling element 4. The choke centre line is an imaginary line.
[0011] There is one heat conduction element 6 for each of the choke coils 2. Each heat conduction element 6 is a passive element with no inlet or outlet for a cooling liquid circulation. Each heat conduction element 6 is in heat conducting connection with the first cooling surface 41 of the liquid cooling element 4, and with a second outer surface area 22 of the corresponding choke coil 2. The second outer surface area 22 of the choke coil 2 is located on an opposite side of the choke centre line than the first outer surface area 21.
[0012] In each choke coil 2, each of the plurality of coil turns comprises a first rectilinear section such that the first rectilinear sections form the first outer surface area 21 of the choke coil 2. A length of the first rectilinear section is greater than 10% of a total length of the coil turn. The first rectilinear sections increase a heat conducting area between the choke coil and the first cooling surface of the liquid cooling element compared to the alternative where the choke coil has a circular cross section on a plane perpendicular to the choke centre line.
[0013] Figure 2 shows the cooled electrical assembly of Figure 1 from a direction parallel to the choke centre lines of the choke coils 2. Figure 3 shows the cooled electrical assembly of Figure 1 from a direction perpendicular to the choke centre lines of the choke coils 2. Referring to Figure 2, a first heat conduction angle α between the heat conduction element 6 and an outer surface of the choke coil 2 is approximately 105°. The first heat conduction angle α is defined relative to the choke centre line. In an alternative embodiment, a first heat conduction angle between a heat conduction element and an outer surface of a choke coil is greater than or equal to 90°.
[0014] In a longitudinal direction, a dimension of the heat conduction element 6 is equal to a dimension of the plurality of coil turns of the choke coil 2 corresponding to the heat conduction element 6, wherein the longitudinal direction is parallel to the choke centre line of the choke coil 2. Therefore, the plurality of coil turns of the choke coil 2 is entirely located between the heat conduction element 6 and the first cooling surface 41 of the liquid cooling element 4. In an alternative embodiment, in a longitudinal direction a dimension of at least one heat conduction element is greater than or equal to 50% of a dimension of the plurality of coil turns of at least one choke coil, the longitudinal direction being parallel to the choke centre line of the at least one choke coil.
[0015] The cooled electrical assembly comprises a pump (not shown) adapted to pump cooling liquid through the liquid cooling element 4. The liquid cooling element 4 comprises an inlet port 431 and outlet port 432 for the cooling liquid.
[0016] The liquid cooling element 4 and the heat conduction elements 6 are made of aluminium. The insulating system electrically insulates the liquid cooling element 4 from the choke coils 2, and each heat conduction element 6 from the corresponding choke coil 2. The insulating system comprises an insulating sheet 5 for each choke coil 2, each choke coil 2 being wrapped in a corresponding insulating sheet 5. Each insulating sheet 5 is made of an electrically insulating, thermally conducting and flexible material. Figures 1 and 3 show, that a longitudinal dimension of the insulating sheet 5 is greater than a longitudinal dimension of the plurality of coil turns of the choke coil 2 inside the insulating sheet 5.
[0017] The insulating sheets 5 are thin sheets. In an embodiment, thickness of the insulating system is less than or equal to 2mm. In another embodiment, thickness of the insulating system is less than or equal to 1mm.
[0018] It should be noted that the plurality of coil turns of each choke coil 2 is coated with an insulating varnish. The insulating varnish electrically insulates the plurality of coil turns from each other. The insulating system is a separate system from the insulating varnish.
[0019] Figure 6 shows one of the choke coils 2 as a separate component. In addition to the plurality of coil turns, the choke coil 2 has a first terminal 271 and a second terminal 272 adapted for connecting the choke coil 2 electrically to an electric circuit (not shown). The first terminal 271 and the second terminal 272 extend further in the longitudinal direction than the plurality of coil turns. Figure 3 shows that the first terminal 271 and the second terminal 272 extend further in the longitudinal direction than the heat conduction element 6 and the insulating sheet 5.
[0020] Each heat conduction element 6 is heat conductively connected to the liquid cooling element 4 by a first heat conduction area 61 and a second heat conduction area 62 which are located on opposite sides of the first outer surface area 21 of the choke coil 2 corresponding to the heat conduction element 6.
[0021] Figure 2 shows that the first heat conduction area 61 is electrically insulated from the liquid cooling element 4 by the insulating system while the second heat conduction area 62 is in direct heat and electricity conducting connection with the liquid cooling element 4. The electrical insulation between the first heat conduction area 61 and the liquid cooling element 4 prevents forming of an electrically conducting loop around the choke coil 2 corresponding to the heat conduction element 6.
[0022] The liquid cooling element 4 is adapted to be grounded. Since each of the heat conduction elements 6 is in electrically conductive connection with the liquid cooling element 4 through the second heat conduction area 62 thereof, the heat conduction elements 6 are also adapted to be grounded.
[0023] In an alternative embodiment, the liquid cooling element and the heat conduction elements are made of another electrically conductive material than aluminium. In another alternative embodiment, the liquid cooling element and heat conduction elements of the cooled electrical assembly are made of electrically non-conductive materials, and there is no separate insulating system. In an embodiment, the liquid cooling element and the heat conduction elements are injection moulded elements made of thermally conductive plastic materials.
[0024] There is a plurality of heat pipes embedded in each of the heat conduction elements 6 for enhancing heat conduction from the second outer surface area 22 of the corresponding choke coil 2 to the first cooling surface 41 of the liquid cooling element 4. Each of the plurality of heat pipes has an evaporator section located adjacent the second outer surface area 22 of the corresponding choke coil 2, and a condenser section located adjacent the first cooling surface 41 of the liquid cooling element 4. In an alternative embodiment, passive heat-transfer devices other than heat pipes are embedded in the heat conduction elements.
[0025] The pressing system presses the heat conduction elements 6 towards the first cooling surface 41 of the liquid cooling element 4. Further, the pressing system presses the heat conduction elements 6 towards the choke coils 2. Therefore, the pressing system enhances heat conduction between the heat conduction elements 6 and the first cooling surface 41 of the liquid cooling element 4, and between the heat conduction elements 6 and the choke coils 2.
[0026] The pressing system comprises twelve screws 88, four first type pressing members 501, and two second type pressing members 502. The first type pressing members 501 and the second type pressing members 502 are best seen in Figures 4 and 5 which show the cooled electrical assembly of Figure 1 in a disassembled state. The screws 88 co-operate with internal threads provided in the liquid cooling element 4. The first type pressing members 501 and the second type pressing members 502 distribute pressing forces exerted by the screws 88 to a larger surface area.
[0027] The electrical device 101 is a semiconductor switch device comprising a plurality of semiconductor switches, and has an outer contact area that is in heat conducting connection with a second cooling surface 42 of the liquid cooling element 4, the second cooling surface 42 being located on an opposite side of the liquid cooling element 4 than the first cooling surface 41. In an alternative embodiment, the outer contact area of the electrical device is in heat conducting connection with the first cooling surface of the liquid cooling element. In another alternative embodiment, the electrical device is a device other than a choke coil, which generates waste heat during its operation.
1. A cooled electrical assembly comprising:
at least one choke coil (2) having a plurality of coil turns wound around a choke centre line;
a liquid cooling element (4) adapted for cooling the at least one choke coil (2), the liquid cooling element (4) having a first cooling surface (41) that is in heat conducting connection with a first outer surface area (21) of the at least one choke coil (2),
characterized in that the cooled electrical assembly comprises at least one a heat conduction element (6) that is in heat conducting connection with the first cooling surface (41) of the liquid cooling element (4), and with a second outer surface area (22) of the at least one choke coil (2) located on an opposite side of the choke centre line than the first outer surface area (21).
2. The cooled electrical assembly according to claim 1, wherein for each of the at least
one choke coil (2), a first heat conduction angle (α) between the heat conduction
element (6) and an outer surface of the choke coil (2) is greater than or equal to
90°, the first heat conduction angle (α) being defined relative to the choke centre
line.
3. The cooled electrical assembly according to claim 1 or 2, wherein the at least one
heat conduction element (6) is made of an electrically non-conductive material, and
the heat conducting connection between the heat conduction element (6) and the first
cooling surface (41) of the liquid cooling element (4) is based on a direct contact
between them.
4. The cooled electrical assembly according to claim 1 or 2, wherein the liquid cooling
element (4) is made of an electrically conductive material, and the cooled electrical
assembly comprises an insulating system electrically insulating the liquid cooling
element (4) from the choke coil (2).
5. The cooled electrical assembly according to claim 4, wherein the at least one heat
conduction element (6) is made of an electrically conductive material, and the insulating
system electrically insulates the at least one heat conduction element (6) from the
at least one choke coil (2), and at least partially electrically insulates the at
least one heat conduction element (6) from the liquid cooling element (4).
6. The cooled electrical assembly according to claim 5, wherein the at least one heat
conduction element (6) is connected to the liquid cooling element (4) by a first heat
conduction area (61) and a second heat conduction area (62) which are located on opposite
sides of the first outer surface area (21) of the at least one choke coil (2).
7. The cooled electrical assembly according to claim 6, wherein at least one of the first
heat conduction area (61) and the second heat conduction area (62) is electrically
insulated from the liquid cooling element (4) by the insulating system in order to
prevent forming of an electrically conducting loop around the choke coil (2).
8. The cooled electrical assembly according to any one of the preceding claims, wherein
there is at least one passive heat-transfer device embedded in the at least one heat
conduction element (6) for enhancing heat conduction from the second outer surface
area (22) of the choke coil (2) to the first cooling surface (41) of the liquid cooling
element (4).
9. The cooled electrical assembly according to claim 8, wherein the at least one passive
heat-transfer device comprises a heat pipe.
10. The cooled electrical assembly according to any one of the preceding claims, wherein
the first cooling surface (41) of the liquid cooling element (4) is a planar surface.
11. The cooled electrical assembly according to claim 10, wherein the choke centre line
of the at least one choke coil (2) extends linearly, and is parallel to the first
cooling surface (41) of the liquid cooling element (4).
12. The cooled electrical assembly according to claim 10 or 11, wherein each of the plurality
of coil turns of the at least one choke coil (2) comprises a first rectilinear section
such that the first rectilinear sections form the first outer surface area (21) of
the at least one choke coil (2).
13. The cooled electrical assembly according to claim 11 or 12, wherein a dimension of
the at least one a heat conduction element (6) in a longitudinal direction is greater
than or equal to 50% of a dimension of the plurality of coil turns of the at least
one choke coil (2) in the longitudinal direction, the longitudinal direction being
parallel to the choke centre line of the at least one choke coil (2).
14. The cooled electrical assembly according to any one of the preceding claims, wherein
the cooled electrical assembly comprises at least one electrical device (101) other
than a choke coil, the at least one electrical device (101) having an outer contact
area that is in heat conducting connection with the liquid cooling element (4).
15. The cooled electrical assembly according to claim 14, wherein the outer contact area
of the at least one electrical device (101) is in heat conducting connection with
a second cooling surface (42) of the liquid cooling element (4), the second cooling
surface (42) being located on an opposite side of the liquid cooling element (4) than
the first cooling surface (41).
16. The cooled electrical assembly according to any one of the preceding claims, wherein
the cooled electrical assembly comprises a pressing system for pressing the at least
one a heat conduction element (6) towards the first cooling surface (41) of the liquid
cooling element (4), the pressing system comprising a plurality of screws (88).