Electric device

1. An electric device comprising at least one core ( 5 , 10 ) of magnetic material and a high-voltage winding ( 16 ) in the form of an electric conductor wound around the core, characterised in that it comprises

a first insulating layer ( 14 ) of a solid, electrically insulating material which encloses the core ( 10 ) and which is arranged between the core ( 10 ) and the high-voltage winding ( 16 ), a first and a second semiconductive layer being arranged on separate sides of the first electrically insulating layer,

a second insulating layer ( 18 ) of a solid, electrically insulating material enclosing the high-voltage winding ( 16 ), a third and a fourth semiconductive layer being arranged on either side of the second electrically insulating layer.

2. An electric device according to claim 1 , wherein the first semiconductive layer ( 13 ) is in contact with the first insulating layer and enclosed by the first insulating layer ( 14 ),

the second semiconductive layer ( 15 ) is arranged between the first insulating layer ( 14 ) and the high-voltage winding ( 16 ) in contact with both the first layer and the high-voltage winding ( 16 ),

the third semiconductive layer ( 17 ) is arranged between the second insulating layer ( 18 ) and the high-voltage winding ( 16 ) in contact with both the second insulating layer ( 18 ) and the high-voltage winding ( 16 ), and

the fourth semiconductive layer ( 19 ) is in contact with and encloses the second insulating layer ( 18 ).

3. An electric device according to claim 1 , wherein the semiconductive layers ( 13 , 15 , 17 , 19 ) have a surface resistance in the range 10 5 -10 8 Ω.

4. An electric device according to claim 1 , wherein the device further comprises a low-voltage winding ( 20 ) which encloses the core.

5. An electric device according to claim 1 , wherein the device also comprises a third insulating layer ( 21 ) of a solid, electrically insulating material, the low-voltage winding ( 20 ) enclosing the second insulating layer ( 18 ) and the low-voltage winding being enclosed by the third insulating layer ( 21 ).

6. An electric device according to claim 1 , wherein the device also comprises an electric conductor which is enclosed by a fourth insulating layer ( 27 ) of an electrically insulating material and which is connected to the high-voltage winding ( 16 ), and which partly is arranged between the first insulating layer ( 14 ) and the second insulating layer ( 18 ), the fourth insulating layer ( 27 ) being provided with a first corona protection layer ( 29 ) of a material exhibiting non-linear resistivity as a function of the electric field along part of the outer side of the fourth insulating layer ( 27 ) from the end of the fourth insulating layer ( 27 ) that is closest to the winding, and the first insulating layer ( 14 ) and the second insulating layer ( 18 ) being provided with a second corona protection layer ( 30 ) and a third corona protection layer ( 31 ), respectively, of the material exhibiting non-linear resistivity, in stretches each of which, in the longitudinal direction of the core, at least partly overlaps the first corona protection layer ( 29 ).

7. An electric device according to claim 6 , wherein the corona protection layers ( 29 , 30 , 31 ) have a surface resistance in the range 10 8 -10 12 Ω for electric fields with an intensity of less than 1 kV/mm.

8. An electric device according to claim 1 , wherein the high-voltage winding ( 16 ) consists of at least one lacquered wire.

9. An electric device according to claim 8 , wherein the high-voltage winding consists of at least two part windings ( 22 ), each having an extent in the longitudinal direction of the core in the range 0.03-2 m.

10. An electric device according to claim 1 , wherein cooling channels ( 12 ) are provided in the core, said cooling channels ( 12 ) being arranged in the longitudinal direction of the core.

11. An electric device according to claim 1 , wherein there is provided a cooling flange ( 63 ) enclosing the fourth semiconductive layer and comprising cooling channels ( 65 ) in the longitudinal direction of the electric device.

12. An electric device according to claim 11 , wherein there is arranged a cooling flange ( 57 ) between the core and the first semiconductive layer, said cooling flange ( 57 ) comprising longitudinal cooling channels ( 64 ).

13. An electric device according to claim 1 , wherein the insulating layers are made of crosslinked polyethylene, so-called PEX.

14. An electric device according to claim 1 , wherein the insulating layers are made of silicone.

15. An electric device according to claim 1 , wherein the device also comprises an electric screen enclosing the outermost insulating layer.

16. Use of an electric device, according to claim 1 , as a transformer in a rail-mounted vehicle.

17. Use of an electric device, according to claim 1 , suspended from the top of a pole ( 42 ).

18. Use of an electric device, according to claim 1 , suspended between two poles.

19. Use of an electric device, according to claim 1 , lying in a cable trench.

20. Use of an electric device, according to claim 1 , lying on a cable rack.

21. Use of an electric device, according to claim 1 , as a transformer for transforming high voltage into mains voltage.

22. Use according to claim 21 , wherein the transformer is located inside the power pole.

23. Use according to claim 16 , wherein the cores are interconnected at both ends.

24. Use according to claim 16 , wherein an end portion of stripped cores of the devices are twisted around each other to close the magnetic flux.

25. Use of an electric device according to claim 1 , at frequencies above 150 Hz.