Cooling system for a dry-type air-core reactor

1. A cooling system for a dry air-core reactor, the reactor comprising a winding around the air-core, the winding being divided into winding packages, the air core comprising:

first open spaces inside the winding packages to let air flow through the winding inside the winding packages in parallel with an axis of symmetry of the reactor and

second open spaces crossing the first open spaces between winding packages to let air flow through the winding between winding packages angular to the axis of symmetry,

the cooling system comprising:

a ventilation unit producing a forced-air flow, where a first part of the forced-air flow enters one of the first or second open spaces,

at least one guiding element which is arranged with respect to a crossing of the first and the second open spaces in such a way that the first part of the forced-air flow leaves and a second part of the forced-air flow enters the one of the first or second open spaces, and

a shielding element is arranged at another crossing of the first and the second open spaces so that substantially no air can leave or enter the one of the first or second open spaces.

2. The cooling system according to claim 1 , wherein the ventilation unit generates the forced-air flow outside of the winding and the at least one guiding element guides the first part of the forced-air flow into the air-core.

3. The cooling system according to claim 1 , wherein the ventilation unit generates the forced-air flow inside of the air-core and the at least one guiding element guides the first part of the forced-air flow to the outside of the winding.

4. The cooling system according to claim 1 , wherein the cooling air is enclosed by a substantially closed space leaving mainly one intake opening for fresh air to enter and another outlet opening for used air to leave the closed space.

5. The cooling system according to claim 4 , further comprising:

at least one outlet shielding unit to prevent forced-air to flow directly to the outlet opening without entering the first or second open spaces.

6. The cooling system according to claim 4 , further comprising:

at least one intake shielding unit to prevent used air to flow back to the intake opening.

7. The cooling system according to claim 1 , wherein the second open spaces are arranged perpendicular to the axis of symmetry.

8. The cooling system according to claim 1 , wherein the ventilation unit comprises a tube unit and a fan arranged inside the tube unit.

9. A method to convert an air-core reactor with natural-air cooling into an air-core reactor with forced-air cooling, wherein the air-core reactor comprises

a winding around the air core and divided into winding packages,

first open spaces inside the winding packages to let air flow through the winding inside the winding packages in parallel with an axis of symmetry of the reactor, and

second open spaces crossing the first open spaces between winding packages to let air flow through the winding between winding packages angular to the axis of symmetry,

the method comprising:

arranging a ventilation unit to produce a forced-air flow towards the air-core reactor so that a first part of the forced-air flow enters one of the first or second open spaces,

arranging at least one guiding element with respect to a crossing of the first and the second open spaces in such a way that the first part of the forced-air flow leaves and a second part of the forced-air flow enters the one of the first or second open spaces, and

arranging a shielding element at another crossing of the first and the second open spaces so that substantially no air can leave or enter the one of the first or second open spaces.

10. The method according to claim 9 , wherein the first open spaces are obtained via spacers inserted in each of the winding packages.

11. The cooling system according to claim 1 , wherein the first open spaces are obtained via spacers inserted in each of the winding packages.