THERMALLY INSULATED RADIATOR ELEMENT

Abstract

An electrical device, such as a transformer or an inductor, for connecting to a high-voltage network includes a tank which is filled with an insulating fluid and which encases a magnetizable core and at least one winding. A cooling system includes at least one radiator which is arranged outside the tank and is connected to same for circulating the insulating fluid via the radiator. The radiator has at least two heat exchange elements connected in parallel with one another. In order to cost-effectively accelerate a cold start, one of the heat exchange elements is fitted with a thermal insulation unit which reduces the heat transfer from the insulating fluid into the insulated heat exchange element to the atmosphere in comparison with a heat exchange element with no thermal insulation unit.

Claims

1-9. (canceled)

10. An electrical device for connection to a high-voltage network, the electrical device comprising: a tank filled with an insulating fluid; a magnetizable core and at least one winding disposed in said tank; a cooling system having at least one radiator arranged outside and fluidically connected to said tank for circulating the insulating fluid via said radiator, said radiator having at least two heat-exchange elements connected in parallel with one another; at least one of said heat-exchange elements being an insulated heat-exchange element equipped with a thermally insulating unit configured to reduce a heat transfer from the insulating fluid in said insulated heat-exchange element to an exterior atmosphere in comparison with a heat-exchange element without a thermally insulating unit.

11. The electrical device according to claim 10, wherein one single heat-exchange element is equipped with said thermally insulating unit.

12. The electrical device according to claim 11, wherein said at least one radiator has an upper feed line and a lower return line each connected to said tank and connected to one another via said heat-exchange elements, and wherein said insulated heat-exchange element that is equipped with said thermally insulating unit is an innermost heat-exchange element at a smallest distance from said tank.

13. The electrical device according to claim 10, wherein said thermally insulating unit encloses the respectively associated heat-exchange element in places or completely.

14. The electrical device according to claim 10, wherein said thermally insulating unit consists of at least one thermally insulating material.

15. The electrical device according to claim 10, wherein said thermally insulating unit has a heat transfer coefficient of less than $1.Math.\frac{W}{m^2.Math.K}.$

16. The electrical device according to claim 15, wherein the heat transfer coefficient lies between 0.5 and $0.01.Math.\frac{W}{m^2.Math.K}.$

17. The electrical device according to claim 10, wherein said cooling system is a passive cooling system.

18. The electrical device according to claim 10, wherein said cooling system has a plurality of radiators, and wherein only one of said radiators has a heat-exchange element equipped with said thermally insulating unit.

Description

[0020] Further configurations and advantages of the invention constitute the subject matter of the following description of exemplary embodiments of the invention with reference to the figures of the drawings, wherein identically acting components are provided with identical reference signs and wherein

[0021] FIG. 1 is a side view of a conventional commercial radiator,

[0022] FIG. 2 is a plan view of a heat-exchange element of the radiator according to FIG. 1 and

[0023] FIG. 3 is a schematic side view of an exemplary embodiment of the electrical device according to the invention.

[0024] FIG. 1 is a schematic side view of an exemplary embodiment of a conventional commercial radiator 1. It is apparent that the radiator 1 has an upper feed line 2 which is connected hydraulically with a return line 4 via heat-exchange element or radiator elements 3. The feed line 2 and the return line 4 have an inlet and outlet opening respectively which points to the left and via which the radiator 1 communicates after installation thereof with the interior of a tank not shown in FIG. 1. The insulating fluid of said tank may then be circulated via the feed line 2, the heat-exchange elements 3 and the return line 4 via the radiator 1 with its heat-exchange elements 3. The heat-exchange elements 3 are made of a thermally conductive material, such as a metal, and are in thermal contact with the external atmosphere. If the insulating fluid is guided via the heat-exchange elements, heat is thus dissipated from the heated insulating fluid to the colder external atmosphere.

[0025] FIG. 2 shows a heat-exchange element 3 in front view. It is apparent that the heat-exchange elements 3 are plate-shaped. In other words, the radiator 1 shown in FIG. 1 is a “plate radiator”. The plate-shaped heat-exchange elements 3 in each case define flow channels, through which the insulating fluid circulated via the heat-exchange elements 3 is guided. Ultimately, the insulating fluid arrives at the collecting return line 4 and thence arrives as cooled insulating fluid back in the interior of the tank.

[0026] FIG. 3 shows an exemplary embodiment of the electrical device 5 according to the invention, which here takes the form of a transformer. The electrical device 5 according to the invention may however also take the form of a choke. The transformer 5 has a tank 6, which is filled with an insulating fluid 7. Furthermore, a magnetizable core 8 and windings 9 are arranged in the tank 6, only one of these windings being indicated schematically in FIG. 3, however. The windings 9 here however comprise a “high-voltage winding” and a “low-voltage winding”, which are arranged concentrically to a limb 10 of the core 8. The mode of operation of such a transformer 5 is, however, known to a person skilled in the art and therefore will not be addressed in greater detail here. The necessary connection lines for connecting the windings to a high-voltage network are likewise not shown in the figures for reasons of clarity.

[0027] The transformer 5 is provided with a cooling system 11, here merely comprising a radiator 1 according to FIG. 1, attached to the outside of the tank 6. It is apparent that the feed line 2 and the return line 4 open into the interior of the tank 6. The fact that the feed line 2 and the return line 4 are connected together via heat-exchange elements 3 enables circulation of the insulating fluid 7 via the radiator 1. A heat-exchange element which is at the smallest distance from the tank 6, the “innermost radiator element” 12, is equipped with a thermally insulating unit 13. The thermally insulating unit 13 consists of an extensive thermally insulating layer 13, which encloses the entirety of the radiator element 12. The thermally insulating layer 13 is shown in sectional view in FIG. 3. A conventional adhesive bond serves to fasten the thermally insulating layer to the radiator element 12.

[0028] If the transformer 5 is at a standstill for a relatively long period, the insulating fluid 7 cools down completely. At low external temperatures in particular, for example in the range from −10° C. to −50° C., the insulating fluid 7 exhibits such a high viscosity, in other words it is so viscous, that it is no longer circulated via the radiator 1 even after an extended starting procedure. It is for this reason that the thermally insulating unit 13 is provided, which ensures that heated insulating fluid which has been only slightly heated is not immediately cooled again in the innermost heat-exchange element 12. For the purposes of the invention, the high-voltage winding of winding 9 may thus be connected to the high-voltage network. In contrast, a resistance appropriate therefor is applied to the low-voltage winding, such that the transformer 5 is not operated under full load. In this case, gradual heating of the insulating fluid 7 and thus of the outer wall of the tank 6 occurs. Cooling in the heat-exchange element 12 is greatly impeded, such that the circulated insulating fluid 7 is heated more rapidly. The continuous, gradually established heating of the insulating fluid 7 is transferred little by little also to the remaining heat-exchange elements 3, until the desired operating state is ultimately achieved.

[0029] It should finally be noted that, for the purposes of the invention, load control in the event of a cold start may be selected at will. At variance with the above-stated implementation of a cold start, the electrical device according to the invention may also be started under full load.