Electrolytic Capacitor with Safety Vent

Abstract

An electrolytic capacitor with a safety vent is disclosed. In an embodiment the electrolytic capacitor includes a case, a capacitor element mounted in the case and a safety vent for enabling pressure relief, wherein the safety vent is located at least partially inside a hole of the capacitor element.

Claims

1-19. (canceled)

20. An electrolytic capacitor comprising: a case; a capacitor element mounted in the case; and a safety vent for enabling pressure relief, wherein the safety vent is located at least partially inside a hole of the capacitor element.

21. The electrolytic capacitor of claim 20, wherein the safety vent comprises a membrane.

22. The electrolytic capacitor of claim 20, further comprising terminals located at a first side of the electrolytic capacitor, wherein the safety vent is configured such that the pressure relief is enabled through an opposite second side of the electrolytic capacitor.

23. The electrolytic capacitor of claim 20, further comprising a cover member for sealing the case, wherein the cover member comprises an elastic material, and wherein the cover member is free from the safety vent.

24. The electrolytic capacitor of claim 20, wherein the electrolytic capacitor is configured such that an electrolyte in the electrolytic capacitor is not in contact with the safety vent.

25. The electrolytic capacitor of claim 20, further comprising a centering member extending into the hole of the capacitor element, wherein the safety vent is located in the centering member.

26. The electrolytic capacitor of claim 25, wherein the centering member is located near a first side or a second side of the electrolytic capacitor.

27. The electrolytic capacitor of claim 20, wherein the safety vent is recessed in the electrolytic capacitor.

28. The electrolytic capacitor of claim 20, wherein a cavity is located between the safety vent and an outer side of the electrolytic capacitor.

29. The electrolytic capacitor of claim 20, further comprising a stud, wherein the safety vent is located in the stud.

30. The electrolytic capacitor of claim 29, further comprising terminals at a first side of the electrolytic capacitor, wherein the stud is located at a second side of the electrolytic capacitor, and wherein the first side is opposite to the second side.

31. The electrolytic capacitor of claim 30, wherein the electrolytic capacitor comprises two safety vents.

32. The electrolytic capacitor of claim 31, wherein one of the safety vents is located in an elastic cover member for sealing the case at a first side and one of the safety vents is located inside a hole in the capacitor element near a second side of the electrolytic capacitor.

33. The electrolytic capacitor of claim 31, wherein one of the safety vents is located near a first side and one of the safety vents is located near a second side of the electrolytic capacitor, and wherein both safety vents are at least partially located inside a hole in the capacitor element.

34. A mounting assembly comprising: the electrolytic capacitor according to claim 20; and a mounting member, wherein the electrolytic capacitor is mounted at the mounting member.

35. An electrolytic capacitor comprising: a case; a capacitor element mounted in the case; a safety vent for enabling gradual pressure relief; and terminals located at a first side of the electrolytic capacitor, wherein pressure relief is enabled through an opposite second side of the electrolytic capacitor.

36. A mounting assembly comprising: the electrolytic capacitor according to claim 35; and a mounting member, wherein the electrolytic capacitor is mounted at the mounting member.

37. A method of operating an electrolytic capacitor, wherein the electrolytic capacitor comprises a safety vent for enabling gradual pressure relief through a side of the electrolytic capacitor, the method comprising: operating the capacitor in an orientation where the side does not point downwards.

38. The method of claim 37, wherein the side points upwards.

39. The method of claim 37, wherein the side points in a horizontal direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Further features, refinements and expediencies become apparent from the following description of the exemplary embodiments in connection with the figures.

[0036] FIG. 1 shows a schematic cross sectional view of a capacitor according to a first embodiment,

[0037] FIG. 2 shows a view on a second side of the capacitor according to the first embodiment,

[0038] FIG. 3 shows a view on a first side of the capacitor according to the first embodiment.

[0039] FIG. 4 shows a schematic cross sectional view of a capacitor according to a second embodiment.

[0040] Similar elements, elements of the same kind and identically acting elements may be provided with the same reference numerals in the figures.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0041] FIG. 1 shows an electrolytic capacitor 1. The capacitor 1 comprises a case 2 and a capacitor element 3 mounted in the case 2. The capacitor element 3 comprises a wound shape. The capacitor element 3 has a cylindrical shape with a hole 4 extending along its central axis. The capacitor element 3 may comprise foils, in particular aluminum foils. The capacitor element 3 is impregnated with a liquid electrolyte.

[0042] The case 2 may have the shape of a circular cylinder. The case 2 may comprise a metal. As an example, the case 2 may comprise aluminum. The case 2 may have the shape of a can.

[0043] The capacitor 1 comprises a first side 6, a lateral side 7 and a second side 8. The second side 8 is opposite to the first side 6. The second side 8 may be formed by a bottom 5 of the case 2. The bottom 5 may comprise a metal. The bottom 5 may be integrally formed with the lateral side 7.

[0044] At the first side 6, the capacitor 1 comprises terminals 9, 10 for electrically connecting the capacitor. The terminals 9, 10 may be configured as screw-type terminals. The capacitor 1 may be configured to be mounted terminal-down, i.e., such that the terminals 9, 10 point towards the Earth's center. Alternatively, the capacitor 1 may be mounted horizontally, i.e., with the terminals 9, 10 pointing in a horizontal direction. Alternatively, the capacitor 1 may be mounted terminal-up.

[0045] The capacitor 1 may be mounted at a mounting member (not shown). The mounting member may serve to fix the capacitor 1. Additionally, the mounting member may serve to electrically connect the terminals 9, 10. In this case, the mounting member may comprise a printed circuit board or a bus bar, for example.

[0046] At the first side 6, the case 2 is closed by a cover member 11. The cover member 11 may have the shape of a disc. The cover member 11 may seal the case 2. The cover member 11 may comprise a rubber material or another elastic material. The terminals 9, 10 are lead through the cover member 11.

[0047] The capacitor 1 comprises a safety vent 12. The safety vent 12 enables controlled pressure relief. During operation of the capacitor 1, gas generation and pressurization inside the capacitor 1 may occur, which may be caused by electrochemical reactions. The safety vent 12 may enable a discharge of the gas when the inner pressure approaches a critical value. Thereby, an uncontrolled explosion of the capacitor 1 may be prevented. As an example, the safety vent 12 may be designed to burst in case of a critical pressure.

[0048] Additionally or alternatively, the safety vent 12 may enable gradual diffusion of the gas to the ambient during the operation of the electrolytic capacitor 1. Thereby, the inner pressure may be gradually reduced. The safety vent 12 may comprise a membrane 13. The membrane 13 may comprise a rubber or silicone material. In particular, the safety vent 12 may comprise a thin rubber membrane. The membrane 13 may be permeable or semi-permeable for gas.

[0049] The safety vent 12 may be configured such that pressure relief is enabled through the second side 8 of the capacitor 1. In particular, pressure relief is enabled through a hole 14 in the bottom 5 of the case 2. The safety vent 12 is located at a smaller distance from the second side 8 than the first side 6 of the capacitor 1.

[0050] Such an arrangement of the safety vent 12 may be particularly beneficial in a mounting orientation of the capacitor 1 where the side through which pressure-relief is enabled points upwards. In case of pressure relief being enabled through the second side 8, this orientation corresponds to a terminal-down mounting orientation. This construction may be both beneficial in case of a burst of the safety vent 12 and for gradual pressure relief with the safety vent 12 being intact.

[0051] When the safety vent 12 is intact, this construction may prevent the safety vent 12 from being covered with electrolyte. When the safety vent 12 is located at a lower side of the capacitor 1, electrolyte may cover the safety vent 12 due to gravity and thus block diffusion. This may result in cumulative pressurization until the safety vent 12 burst. This phenomenon may reduce the efficiency of the operation of the safety vent 12. When the safety vent 12 is positioned at an upper side of the capacitor 1 it may be kept free from electrolyte such that gradual diffusion is maintained.

[0052] The capacitor 1 comprises a centering member 15 protruding at the second side 8 into the hole 4 of the capacitor element 3. The centering member 15 serves to center the capacitor element 3 in the case 2. The centering member 15 may be formed as a peg. The centering member 15 may be hollow. The centering member 15 may be integrally formed with the bottom 5 of the case 2.

[0053] The safety vent 12 is located in the centering member 15. Thereby the two functions of winding fixation and pressure relief can be combined. The centering member 15 separates the safety vent 12 from the capacitor element 3.

[0054] The safety vent 12 is located inside the hole 4 of the capacitor element 3. The safety vent 12 is encircled by the windings of the capacitor element 3. Accordingly, the safety vent 12 is located in the core of the capacitor 1.

[0055] The safety vent 12 is located at a distance from the bottom 5 of the case 2. In particular, the safety vent 12 is located in a recessed position relative to the bottom 5. Thereby, the safety vent 12, and, in particular the membrane 13 may be protected from mechanical damage.

[0056] As an example, a cavity 16 may exist between the safety vent 12 and the bottom 5. This may help to avoid electrolyte leaking to the outside of the capacitor 1. As an example, the cavity 16 may receive a small amount of electrolyte leaking out of the capacitor 1 after a burst of the safety vent 12. This may prevent the bottom 5 from being contaminated by the electrolyte.

[0057] With the disclosed safety vent 12, the capacitor 1 can be filled with an excess amount of electrolyte, which helps to provide stable electrical parameters. Thereby, parameter drift during long-term operational life can be avoided. As an example, a drying out of the windings may be prevented. In a standard capacitor, the electrolyte reservoir may be restricted in order to avoid free-flowing liquid electrolyte inside the capacitor and, thereby, prevent electrolyte leakage. With the improved safety vent 12, electrolyte leakage may be prevented also in case of a high amount of electrolyte.

[0058] In a further embodiment, the capacitor 1 may alternatively or additionally comprise a centering member located near the first side 6. As an example, the centering member may protrude from the cover member 11 into the hole 4 of the capacitor element 3. A safety vent may be additionally or alternatively located in the centering member near the first side 6.

[0059] When the capacitor 1 comprises two safety vents, wherein one of the safety vents is located near the first side 6 and the other one is located at the second side 8, gradual diffusion may always be ensured, at least through one of the safety vents. In particular, gradual diffusion may be ensured at any orientation of the capacitor. As an example, the capacitor 1 may comprise a safety vent 12 at the second side 8 as shown in FIG. 1 and a further safety vent located in the cover member 11. The further safety vent may also comprise a rubber or silicone material, in particular a membrane.

[0060] FIG. 2 shows a view on the second side 8 of the capacitor 1 according to FIG. 1 after a pressure relief test. The pressure relief test was conducted at reverse polarity according to the IEC-60384-1 (2008) standard. During this test, relatively fast gas generation takes place due to the reverse polarity. Thereby, a high pressure was generated inside the capacitor 1.

[0061] As can be seen in FIG. 2, the membrane 13 of the safety vent 12 has burst. The capacitor 1 was mounted terminal-down. The second side 8, in particular the bottom 5, is not covered by electrolyte.

[0062] FIG. 3 shows a view on the first side 6 of the capacitor 1 according to FIG. 1 after the pressure relief test.

[0063] The first side 6, in particular the cover member 11, is not covered by electrolyte. In the shown embodiment, the cover member 11 is free from any safety vent.

[0064] FIG. 4 shows a further embodiment of a capacitor 1, which corresponds to the capacitor 1 shown in FIGS. 1, 2 and 3 but additionally comprises a stud 17 for mounting the capacitor 1. The stud 17 is located at the second side 8 of the capacitor 1.

[0065] The stud 17 may be threaded for screwing the capacitor 1 to a mounting member (not shown). The terminals 9, 10 may be connected to a printed circuit board or a bus bar, for example.

[0066] The stud 17 may be integrally formed with the bottom 5 and/or the centering member 15.