Non-liquid immersed transformers with improved coil cooling

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.