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1. WO2020115029 - FILM CAPACITOR WITH BALANCING PATH

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[ EN ]

Claims

1. A film capacitor (1) comprising a first film (2a), a second film (2b), a first electrode (3 a) connected to a first terminal, a second electrode (3b) connected to a second terminal, an electrically floating electrode (4), and a balancing path, wherein

a part of the electrically floating electrode (4) is in contact with a front side of the first film (2a), wherein

the balancing path provides a first balancing connection between the electrically floating electrode (4) and the first terminal and a second balancing connection between the electrically floating electrode (4) and the second terminal, wherein

the first balancing connection and the second balancing connection each have an electrical resistance lower than any leakage resistance and higher than 103 Ohm, and wherein

a leakage resistance is an electrical resistance through any of the first film (2a) and the second film (2b) between the electrically floating electrode (4) and an electrode devoid of contact with the front side of the first film (2a).

2. The film capacitor (1) according to claim 1, wherein the balancing path is at least partly provided by a weakly conductive strip (5a), wherein the weakly conductive strip (5a, 5b) is in contact with the electrically floating electrode (4) and any of: the first terminal and the second terminal.

3. The film capacitor (1) according to claim 2, wherein the weakly conductive strip (5a, 5b) is arranged on a surface of the first film (2a).

4. The film capacitor (1) according to any of the preceding claims, wherein

the electrically floating electrode (4) has a shielded portion, wherein the shielded portion is electrically shielded from the first electrode (3 a) and the second electrode (3b) by a shielding portion of an electrode, wherein

the film capacitor (1) has a low-field region comprising the shielded portion and wherein

at least a part of the balancing path is provided in the low-field region.

5. The film capacitor (1) according to claim 4, wherein

the first film (2a) has an edge margin, a front side of the edge margin being devoid of contact with the electrically floating electrode (4), and wherein

the low- field region further comprises a part of the edge margin which adjoins the shielded portion.

6. The film capacitor (1) according to any of claims 4 to 5, wherein the weakly conductive strip (5a, 5b) is located only in the low- field region.

7. The film capacitor (1) according to any of the preceding claims, wherein the second film (2b) has a passive section along a main direction of extension, wherein a front side of the passive section is not in contact with any parts of the first electrode (3 a) or the second electrode (3b), and wherein at least a part of the balancing path is provided directly adjacent to a back side of the passive section.

8. The film capacitor (1) according to any of the preceding claims, further comprising a winding bobbin (9), wherein at least a part of the winding bobbin (9) comprises a weakly conductive material and wherein the balancing path is provided at least partly by the weakly conductive material of the winding bobbin (9).

9. The film capacitor (1) according to any of the preceding claims, wherein at least a part of the surface of the first film (2a) is a weakly conductive surface and wherein the balancing path is provided at least partly by the weakly conductive surface.

10. The film capacitor (1) according to claim 8, wherein the weakly conductive surface is provided on a part of the first film (2a) modified so as to decrease a surface resistivity of the first film (2a).

11. The film capacitor (1) according to any of claims 8 to 9, wherein the weakly conductive surface is provided on a fluorinated part of the first film (2a).

12. The film capacitor (1) according to any of claims 4 to 11, wherein the weakly conductive surface is located only in the low-field region.

13. The film capacitor (1) according to any of the preceding claims, wherein

the balancing path is provided at least partly by a weakly conductive layer which covers at least a part of the first film (2a).

14. The film capacitor (1) according to claim 13, wherein the weakly conductive layer covers the first film (2a) only in the low-field region of the first film (2a).

15. The film capacitor (1) according to any of the preceding claims, further comprising a third terminal (8) connected to the electrically floating electrode (4), wherein the balancing path is provided at least partly by an external weakly conductive unit connected to the third terminal (8).