Non-liquid immersed transformers with improved coil cooling

Abstract

A non-liquid immersed transformer including a magnetic core having a winding axis and at least two coil windings wound around the magnetic core along the winding axis. One or more cooling tubes made of dielectric material are arranged inside at least one of the coil windings to cool down the coil winding using dielectric fluid flowing through the dielectric cooling tubes. Each cooling tube is wound continuously forming one or more complete loops around the core.

Claims

1. A non-liquid immersed transformer comprising: a magnetic core having a winding axis; at least two coil windings wound around the magnetic core along the winding axis; at least one cooling tube made of dielectric material arranged inside at least one of the coil windings to cool down the coil winding using dielectric fluid flowing through the cooling tube made of dielectric material, wherein said at least one cooling tube is continuously wound forming one or more complete loops around the magnetic core, and wherein at least one of the coil windings comprises foil windings having foil turns and said at least one cooling tube is helicoidally wound continuously forming one or more complete loops around the core placed in a space defined between turns of the foil winding and passing into through holes provided on a metallic piece interposed between and joining adjacent turns.

2. The non-liquid immersed transformer according to claim 1, wherein at least one of the coil windings comprises turns made of electricity conducting material and encapsulated in epoxy resin together with the at least one cooling tube.

3. A non-liquid immersed transformer comprising: a magnetic core having a winding axis; at least two coil windings wound around the magnetic core along the winding axis; at least one cooling tube made of dielectric material arranged inside at least one of the coil windings to cool down the coil winding using dielectric fluid flowing through the cooling tube made of dielectric material, wherein said at least one cooling tube is continuously wound forming one or more complete loops around the magnetic core, and wherein at least one of the coil windings comprises foil windings having foil turns and said at least one cooling tube is helicoidally wound continuously forming one or more complete loops around the core placed in a space defined between turns of the foil winding and crossing the conductive foil turns through holes made in the foil windings.

4. A non-liquid immersed transformer comprising: a magnetic core having a winding axis; at least two coil windings wound around the magnetic core along the winding axis; at least one cooling tube made of dielectric material arranged inside at least one of the coil windings to cool down the coil winding using dielectric fluid flowing through the cooling tube made of dielectric material, wherein said at least one cooling tube is continuously wound forming one or more complete loops around the magnetic core, and wherein at least one of the coil windings comprises foil-disk windings or CTC-disk windings and the at least one cooling tube is located in a space between disks, wherein any two cooling tube portions located at consecutive spaces are connected by passing the tube over the disk between two consecutive spaces.

5. The non-liquid immersed transformer according to claim 1, wherein at least one of the coil windings comprises helical or layer winding as strand wire or continuously transposed conductors (CTC) and the at least one cooling tube is wound helicoidally forming one or more complete loops around the core and placed between turns of the helical winding or in spaces between the turns of the layer winding.

6. The non-liquid immersed transformer according to claim 1, wherein said at least one cooling tube comprises a single tube wound continuously forming one or more complete loops around the core.

7. The non-liquid transformer according to claim 1, wherein said at least one cooling tube comprises several tubes connected in parallel using fittings and each wound continuously forming one or more complete loops around the core.

8. The non-liquid immersed transformer according to claim 1, further comprising a cooling circuit to supply fresh dielectric fluid to the at least one cooling tube, wherein the cooling circuit comprises at least a pump and a heat-exchanger.

9. The non-liquid immersed transformer according to claim 1, wherein the dielectric fluid is one of an ester fluid, a silicone fluid, a non-flammable fluid, and a mineral or natural oil.

10. The non-liquid immersed transformer according to claim 1, wherein the at least one cooling tube is made of plastic material.

11. The non-liquid immersed transformer according to claim 10, wherein the at least one cooling tube is made of plastic material selected from the group consisting of cross-linked polyethylene (PEX), polyphenylsulfone (PPSU), polybutylene (PB), polytetrafluoroethylene (PTFE) or silicone.

12. The non-liquid immersed transformer according to claim 1, comprising a first cooling tube to cool a primary coil winding and wound continuously forming one or more complete loops around the core inside said primary coil winding and a second cooling tube to cool a secondary coil winding and wound continuously forming one or more complete loops around the core inside said secondary coil winding.

13. The non-liquid immersed transformer according to claim 1, wherein the primary coil winding is a high voltage winding and the secondary coil winding is a low voltage winding.

14. A three-phase transformer comprising non-liquid immersed transformers according to claim 1.

15. A non-liquid immersed transformer comprising: a magnetic core having a winding axis; at least two coil windings wound around the magnetic core along the winding axis; and at least one cooling tube made of dielectric material arranged inside at least one of the coil windings to cool down the coil winding using dielectric fluid flowing through the cooling tube made of dielectric material, wherein said at least one cooling tube is continuously wound forming one or more complete loops around the magnetic core, wherein at least one of the coil windings comprises turns made of electricity conducting material and encapsulated in epoxy resin together with the at least one cooling tube, and wherein at least one of the coil windings comprises foil windings having foil turns and said at least one cooling tube is helicoidally wound continuously forming one or more complete loops around the core placed in a space defined between turns of the foil winding and crossing the conductive foil turns through holes made in the foil windings.

16. A non-liquid immersed transformer comprising: a magnetic core having a winding axis; at least two coil windings wound around the magnetic core along the winding axis; and at least one cooling tube made of dielectric material arranged inside at least one of the coil windings to cool down the coil winding using dielectric fluid flowing through the cooling tube made of dielectric material, wherein said at least one cooling tube is continuously wound forming one or more complete loops around the magnetic core, wherein at least one of the coil windings comprises turns made of electricity conducting material and encapsulated in epoxy resin together with the at least one cooling tube, and wherein at least one of the coil windings comprises foil-disk windings or CTC-disk windings and the at least one cooling tube is located in a space between disks, wherein any two cooling tube portions located at consecutive spaces are connected by passing the tube over the disk between two consecutive spaces.

17. The non-liquid immersed transformer according to claim 2, wherein at least one of the coil windings comprises helical or layer winding as strand wire or continuously transposed conductors (CTC) and the at least one cooling tube is wound helicoidally forming one or more complete loops around the core and placed between turns of the helical winding or in spaces between the turns of the layer winding.

18. The non-liquid immersed transformer according to claim 2, wherein said at least one cooling tube comprises a single tube wound continuously forming one or more complete loops around the core.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Non-limiting examples of the present disclosure will be described in the following, with reference to the appended drawings, in which:

(2) FIG. 1 is a schematic partial and sectional view of a transformer comprising cooling tube(s) according to an exemplary embodiment;

(3) FIGS. 2a-2b are schematic views of an exemplary transformer comprising a foil winding coil with the cooling tube(s) wound inside the coil continuously forming one or more completed loops in a helical configuration;

(4) FIGS. 3a-3b are schematic views of a transformer comprising a foil-disk or CTC-disk winding coil with the cooling tubes placed in the space between disks;

(5) FIGS. 4a-4b are schematic views of an exemplary transformer comprising a strand or CTC layer winding coil with the cooling tube(s) placed in the space between layers in a helical configuration;

(6) FIGS. 5a-5b are schematic views of an exemplary transformer comprising a strand or CTC layer winding coil with the cooling tubes placed between turns in a helical configuration.

DETAILED DESCRIPTION OF EXAMPLES

(7) FIG. 1 is a schematic sectional view of a transformer comprising one or more cooling tubes according to the present invention. The transformer of FIG. 1 may be a non-liquid immersed three-phase transformer. The non-liquid immersed transformer 100 may comprise three phases each with a set of windings and arranged around an associated core leg. In the following description, reference will be made to just one electric phase for the sake of simplicity but what described is likewise applicable to each of the phases. For example, a first phase 105 comprises a core leg 110, an inner coil winding 115, an outer coil winding 120. At least one cooling tube made of dielectric material is arranged inside at least one of the coil windings 115, 120 to cool down the coil winding using dielectric fluid flowing through the cooling tube itself and the cooling tube is wound continuously forming one or more completed loops around the magnetic core. In particular, the cooling tube is continuously wound around the core inside the associated coil winding 115 or 120 forming the one or more completed loops.

(8) In the exemplary embodiment illustrated in FIG. 1, a first cooling tube 125 and a second cooling tube 130 are used. The inner coil winding 115 may be a low voltage (LV) winding surrounding the core 110. The inner coil winding 115 may be a foil winding. The first cooling tube winding 125 is wound forming one or more completed loops around the core leg 110, preferably in a helical form, placed between the turns of the foil winding. The outer coil winding 120 may be a high voltage (HV) winding surrounding the inner coil winding 115. The outer coil winding 120 may be a foil-disk winding. The second cooling tube 130 is also wound forming one or more completed loops around the core leg 110, preferably in a helical manner, passing from spaces between disks in the dome area through the external part of the outer coil winding. The cooling tubes 125, 130 may be connected to an external circuit 135. The external circuit may comprise a pump 140, a heat-exchanger 145 and a liquid reservoir 150. The pump 140 may force liquid from the reservoir 150 to the cooling tube windings 125 and 130 through feeding tube 127. The liquid may then be warmed when it passes through the cooling tubes 125 and 130 and return to the external circuit through return tube 129. When the liquid returns warmer it may pass through heat exchanger 145 where the excess heat may be dissipated. The liquid may then return to the liquid reservoir 150.

(9) As indicated, the cooling liquid to be used in the cooling tubes may be any type of suitable dielectric fluid. Preferably it can be an ester fluid, such as Midel®, Biotemp® or Envirotemp®. In other examples the dielectric fluid may be a silicone fluid, or a non-flammable fluid, preferably a fluorinated fluid, such as Novec® or Fluorinert®, or a mineral or natural oil.

(10) The cooling tubes may be made of dielectric material. For example, it may be made of plastic material, preferably selected from the group consisting of cross-linked polyethylene (PEX), polyphenylsulfone (PPSU), polybutylene (PB), polytetrafluoroethylene (PTFE) or silicone.

(11) FIG. 2a and FIG. 2b are schematic views of a transformer comprising a foil winding coil with at least one cooling tube continuously wound forming one or more completed loops around the core, preferably in a helical configuration. The foil winding may comprise turns made of electricity conducting material, preferably aluminum or copper, and all together with the cooling tube(s) are preferably encapsulated in epoxy resin 201. More specifically, the coil winding comprises a first set of turns 202 and a second set of turns 203. Between the turns a space 204 is present. The space 204 may be maintained by spacers (not shown). A cooling tube 205 is wound continuously forming one or more completed loops around the core, arranged preferably in a helical manner, and located in the space 204. The extremes of the cooling tube 205 may be coupled to a pair of connectors 206. The connectors may be used to connect the cooling tube 205 to an external circuit similar to the external circuit 135 described with reference to FIG. 1. The external circuit may then provide cooling dielectric liquid to the cooling tube 205. In a more preferred embodiment, consecutive coil winding turns, such as the turns 202 and 203 illustrated in FIG. 2b are connected, e.g. welded, with a corresponding metallic piece 207 which is interposed there between. A suitable number of metallic pieces 207 is provided in the coil winding, and each preferably comprises through holes 208. A cooling tube 205 passes through holes of the metallic piece 207, as shown in FIG. 2b. Alternatively, the cooling tube(s) is/are wound continuously forming one or more completed loops around the core placed in a space defined between turns of the foil winding and crossing the conductive foil turns through holes made in the foil windings themselves.

(12) FIG. 3a and FIG. 3b are schematic views of a transformer comprising a foil-disk or CTC-disk winding with the cooling tube(s) wound continuously forming one or more completed loops around the core, preferably in a helical configuration. The coil 400 of the example of FIG. 3a may comprise a disk winding and cooling tube 404. The disk winding may comprise disks 402 made of electricity conducting material, preferably aluminum or copper, and the cooling tube(s) together with the coil winding are all encapsulated in epoxy resin 401. More specifically, the disk winding may comprise a series of discs 402. The disks 402 may be separated by spaces 403 present between two adjacent disks 402. The cooling tube 404 is placed in the space between the disks and it may protrude outwards, passing over the disk between two consecutive spaces in order place the cooling duct in the consecutive space between disks. The extremes of the cooling tube 404 may be coupled to a pair of connectors 405. The connectors 405 may be used to connect the cooling tube 404 to an external circuit (not shown) similar to the external circuit 135 discussed with reference to FIG. 1. The external circuit may then provide cooling dielectric liquid to the cooling tube 404.

(13) FIG. 4a and FIG. 4b are schematic views of a transformer comprising a strand or CTC layer winding with the cooling tube(s) 605 wound continuously forming one or more completed loops around the core, preferably in a helical configuration, and placed in the space between layers. The winding may comprise layers made of electricity conducting material, preferably aluminum or copper, and the cooling tube(s) are preferably encapsulated in epoxy resin 601 together with the winding. More specifically, the helical or layer winding may comprise a first layer 602 and a second layer 603. Between the layers a space 604 is present. The space 604 may be maintained by spacers (not shown). A cooling tube 605 is wound forming one or more completed loop around the core, preferably in a helical manner, and arranged in the space 604. The extremes of the cooling tube 605 may be coupled to a pair of connectors 606. The connectors may be used to connect the cooling tube 605 to an external circuit (not shown) similar to the external circuit 135 discussed with reference to FIG. 1. The external circuit may then provide cooling dielectric liquid to the cooling tube 605.

(14) FIG. 5a and FIG. 5b are schematic views of a transformer comprising a strand or CTC layer winding with cooling tubes 703 placed between turns. The helical or layer winding may comprise a layer winding made of electricity conducting material, preferably aluminum or copper; the winding is encapsulated in epoxy resin 701 together with the cooling tube(s). Within the layer winding 702 a cooling tube 703 is arranged which is wound continuously forming one or more completed loops around the core, preferably in a helical manner. The extremes of the cooling tube 703 may be intercalated between the turns of the layer winding 702. The cooling tube 703 may be coupled to a pair of connectors 704. The connectors 704 may be used to connect the cooling tube 703 to an external circuit (not shown) similar to the external circuit 135 discussed with reference to FIG. 1. The external circuit may then provide cooling dielectric liquid to the cooling tube 703.

(15) The above mentioned examples may be used independently in transformer windings or may be combined. For example, in case of LV/HV transformers, a LV winding normally may comprise a foil winding while the HV winding normally may comprise a disk winding. Accordingly, each of the LV/HV windings may have any of the cooling arrangements discussed with reference to the examples disclosed herein. The cooling arrangements may be independent (i.e. each cooling tube may be connected independently) or in parallel connected to an external circuit.

(16) Thanks to the combination of features of the present invention, and in particular to the implementation of a cooling solution with closed loops made of non-conducting material (tubes and fluid) it is possible to avoid voltage drops in the cooling system, thus preventing generation of high currents in the tube or in the liquid inside the tube as instead possible in prior art solutions. In addition to improve cooling, manufacturing is particularly simplified over known solutions, especially when one single tube is continuously wound around the leg and inside an associated coil winding. The constructive layout is simplified reducing or making even unnecessary to use fittings and connections, thus reducing cost and complexity.

(17) Although only a number of examples have been disclosed herein, other alternatives, modifications, uses and/or equivalents thereof are possible. Furthermore, all possible combinations of the described examples are also covered. Thus, the scope of the present disclosure should not be limited by particular examples, but should be determined only by a fair reading of the claims that follow. If reference signs related to drawings are placed in parentheses in a claim, they are solely for attempting to increase the intelligibility of the claim, and shall not be construed as limiting the scope of the claim.