Class y capacitor and inverter

Abstract

Class Y capacitor (1, 7, 12, 16, 27), which can be connected between a line and ground, comprising a first and a second electric conductor (2, 3), which are separated by a dielectric medium, wherein the first electric conductor (2) is connected to a first leg (4, 8, 9, 13, 18) and the second electric conductor (3) is connected to a second leg (5, 10, 11, 19), wherein the first leg (4, 8, 9, 13, 18) has a larger cross-section than the second leg (5, 10, 11, 19). In addition, an inverter (23) with a class Y capacitor (1, 7, 12, 16, 27) is described.

Description

[0001] Class Y capacitor and inverter

[0002] The invention relates to a class Y capacitor, which can be connected between a line and ground, comprising a first and a second electric conductor, which are separated by a dielectric medium, wherein the first electric conductor is connected to a first leg and the second electric conductor is connected to a second leg.

[0003] A class Y capacitor, which is also known as “line to ground capacitor”, can be placed between a line and ground in order to prevent or minimize negative effects of electromagnetic interference and radiofrequency interference.

[0004] Class Y capacitors are used as filter components in high-voltage electric of automobiles. Actually, there is a trend towards higher voltages, higher switching frequencies and faster switching speeds. When conventional class Y capacitors are used, they tend to overheat due to losses of the filtering function, which can lead to failure. Therefore, the operating temperature of class Y capacitors has to be kept below a predetermined limit. Most class Y capacitors are provided with a plastic housing, which does not really conduct heat. As a workaround, several class Y capacitors are connected in series.

[0005] The object of the invention is to provide a class Y capacitor, which can be operated as a filter component in a high-voltage application without overheating.

[0006] This object is achieved by a class Y capacitor with the features of claim 1 .

[0007] The invention is based on the idea that a class Y capacitor can be operated without the danger of overheating, when the first leg has a larger cross-section than the second leg. The first leg can then be connected to a chassis of a housing or ground, in order to dissipate heat from the capacitor. When sufficient heat can be dissipated, there is no risk that the capacitor overheats. By modifying a conventional class Y capacitor such that it has two legs with different cross-sections the risk of overheating can be avoided. Implementation of the invention is cheap, therefore the inventive solution is attractive for all applications in which a class Y capacitor is subjected to higher voltages, higher switching frequencies and faster switching speeds.

[0008] According to the invention it may be envisaged that the first leg comprises two or more leads. Using several leads increases the surface through which heat is dissipated. Several leads can also improve the mechanical stability of the place Y capacitor, when it is placed on a printed circuit board.

[0009] According to a preferred embodiment of the invention the leads are formed as wires, which are preferably arranged in parallel. Using leads in the form of wires is easy, therefore the inventive capacitors can be produced with conventional machines. In addition, such wires can easily be placed on a PCB.

[0010] Preferably, the first leg of the inventive class Y capacitor is formed as a strip. Preferably, the strip has a rectangular cross-section. Due to this shape the first leg has a larger cross-section than the second leg, so that a larger amount of heat can be dissipated through the strip. Such a strip is able to dissipate several times more heat compared to a conventional wire with a circular cross-section.

[0011] The electric conductors of the inventive class Y capacitor can be divided in several parts, wherein each part is connected to the first leg and the second leg. Preferably, the class Y capacitor comprises three parts.

[0012] Preferably, the three parts are formed as bobbins, which are preferably arranged in parallel. Each bobbin may be provided with a housing, which can be made of a plastic material or a metal material.

[0013] The first and second electric conductors of the inventive class Y capacitor can be received in a metal housing. The metal housing of the inventive class Y capacitor can be provided with an attachment point for mounting a heat dissipating component. The attachment point can be provided with a hole, so that a screw can be used for mounting the capacitor on a support.

[0014] It is particularly preferred that the first electric conductor and / or the first leg is / are connected to the metal housing. The metal housing supports the transfer of heat from the conductor to the housing.

[0015] In addition, the invention relates to an inverter with an inventive class Y capacitor, which is connected with the first leg having the larger cross-section to a chassis and / or ground and with the second leg to an AC line or a DC line. The inventive inverter is very reliable because the class Y capacitor does not overheat.

[0016] The invention is explained by means of preferred examples with reference to the drawings. The drawings are schematic and show:

[0017] Fig. 1 a first embodiment of an inventive class Y capacitor;

[0018] Fig. 2 a second embodiment of an inventive class Y capacitor;

[0019] Fig. 3 a third embodiment of an inventive class Y capacitor;

[0020] Fig. 4 a fourth embodiment of an inventive class Y capacitor; and

[0021] Fig. 5 an inventive inverter.

[0022] Fig. 1 shows a first embodiment of a class Y capacitor 1 in an exploded perspective view, which is formed as a cuboid. Within the capacitor 1 a first electric conductor 2 and a second electric conductor 3 are received, which are separated by a dielectric medium and which are formed as wound-up films. The first electric conductor 2 is connected to a first leg 4, the second electric conductor 3 is connected to a second leg 5. In addition, the class Y capacitor 1 also comprises a housing 6 in the form of a cuboid case with one open side, in which the wound-up electric conductors 2, 3 can be inserted. The housing 6 is preferably made of a metal material in order to further optimize the thermal behaviour. However, in other embodiments the housing can e.g. made from aluminium, steel or a plastic material.

[0023] Both legs 4, 5 are formed as wires, whereby the first leg 4 has a larger cross-section than the second leg 5. The class Y capacitor 1 is in particular suitable for applications, in which it is necessary to prevent or minimize negative effects of electromagnetic interference and radiofrequency interference, like in an inverter, which converts direct current into alternating current. During operation the class Y capacitor 1 heats up due to electric losses. This heat has to be dissipated, so that the temperature of the class Y capacitor 1 does not exceed a predetermined limit temperature. The first leg 4 having the larger cross-section is suitable for being connected to a housing of an electronic device, for example an inverter housing. The second leg 5 is intended to be connected to a busbar of the electronic device. Due to its larger cross-section the first leg 4 acts as a heat conductor which helps to dissipate heat from the class Y capacitor 1 . This embodiment has the advantage that no additional cooling like water cooling is necessary. Dissipating the heat from the class Y capacitor 1 through the first leg 4 with the larger cross-section is sufficient to keep the temperature below the limit temperature.

[0024] Fig. 2 shows a second embodiment of a class Y capacitor 7. Those components which are identical to the components of the first embodiment are not explained in detail again. In accordance with the first embodiment the class Y capacitor 7 comprises the first electric conductor 2 and the second electric conductor 3, which are wound-up, and the housing 6, in which the electric conductors 2, 3 are inserted. The first electric conductor 2 is connected to two separate first legs 8, 9. The second electric conductor 3 is connected to two separate second legs 10, 11. The first legs 8, 9 have a larger cross-section than the second legs 10, 11. In the present embodiment the legs 8, 9, 10, 11 have a circular cross-section, but other shapes are also possible like a square or rectangular cross-section. As the overall cross- section of the first legs 8, 9 is larger compared to the first embodiment, the class Y capacitor 7 can even dissipate more heat compared to the class Y capacitor 1 of the first embodiment. In addition, using four legs improves the mechanical stability, when the class Y capacitor 7 is mounted on a support like a printed circuit board. In order to further improve the heat transfer, the first legs 8, 9 can be connected to a metal housing of an electronic device like an inverter.

[0025] Fig. 3 shows a third embodiment of a class Y capacitor 12, which is similar to the first embodiment. The class Y capacitor 12 comprises a first leg 13 and a second leg 5. The first leg 13 has a rectangular cross-section and is formed as a strip. Accordingly, a comparatively large amount of heat can be dissipated through the first leg 13 due to its large cross-section. The first leg 13 has an angled end section 14 which is provided with a hole 15, so that the class Y capacitor 12 can be fixed on a support by a screw. The first leg 13 can be connected to a chassis or a housing of an inverter, the second leg 5 can be connected to a busbar. In this third embodiment the first leg 13 is internally connected to a bobbin of the class Y capacitor 12. Alternatively, the first leg 13 could be connected to the housing 6, which is made of metal and which serves as a ground connection. In this case, a capacitor film is connected to the metal housing inside of the housing 6. This structure is thermally advantageous for the first leg 13 and a housing connection.

[0026] Fig. 4 shows a fourth embodiment of a class Y capacitor 16, with a first conductor and a second conductor, which are divided in three parts which are formed as bobbins 17 and which are arranged in parallel. A first leg 18, which is connected to the first electric conductor, has a larger cross-section than a second leg 19, which is connected to the second electric conductor. Both legs 18, 19 are provided with angled end sections 20, 21 which are each provided with a hole 22. The class Y capacitor 16 can be received in a housing (not shown). On the side of the leg 18 with the larger cross-section the thermal interface of the class Y capacitor 16 is better than on the other side of the leg 19 due to the asymmetric connection. Fig. 5 is a schematic view of an inverter 23, which is connected to a battery 24 and a motor 25. DC current from the battery 24 is converted by the inverter 23 into AC current. The inverter comprises an high voltage DC bus filter, which exemplarily consists of inductors 26, class Y capacitors 27 and power semiconductor devices 28. The AC current is used to drive the motor 25.

[0027] List of reference numbers

[0028] 1 class Y capacitor

[0029] 2 first electric conductor

[0030] 3 second electric conductor

[0031] 4 first leg

[0032] 5 second leg

[0033] 6 housing

[0034] 7 class Y capacitor

[0035] 8 first leg

[0036] 9 first leg

[0037] 10 second leg

[0038] 11 second leg

[0039] 12 class Y capacitor

[0040] 13 first leg

[0041] 14 end section

[0042] 15 hole

[0043] 16 class Y capacitor

[0044] 17 bobbin

[0045] 18 first leg

[0046] 19 first leg

[0047] 20 end section

[0048] 21 end section

[0049] 22 hole

[0050] 23 inverter

[0051] 24 battery

[0052] 25 motor

[0053] 26 inductor

[0054] 27 class Y capacitor

[0055] 28 power semiconductor device

Claims

Claims1. Class Y capacitor (1 , 7, 12, 16, 27), which can be connected between a line and ground, comprising a first and a second electric conductor (2, 3), which are separated by a dielectric medium, wherein the first electric conductor (2) is connected to a first leg (4, 8, 9, 13, 18) and the second electric conductor (3) is connected to a second leg (5, 10, 11 , 19), characterized in that the first leg (4, 8, 9, 13, 18) has a larger cross-section than the second leg (5, 10, 11 , 19).

2. Class Y capacitor according to claim 1 , wherein the first leg (8, 9, 18) comprises two or more leads.

3. Class Y capacitor according to claim 2, wherein the leads are formed as wires, which are preferably arranged in parallel.

4. Class Y capacitor according to any of the preceding claims, wherein the first leg (13, 18) is formed as a strip.

5. Class Y capacitor according to claim 4, wherein the strip (13) has a rectangular cross-section.

6. Class Y capacitor according to any of the preceding claims, wherein the electric conductors (2, 3) are divided in several parts, preferably three parts, wherein each part is connected to the first leg (18) and the second leg (19).

7. Class Y capacitor according to claim 6, wherein the three parts are formed as bobbins (17), which are preferably arranged in parallel.

8. Class Y capacitor according to any of the preceding claims, wherein the conductors (2, 3) are received in a metal housing (6).

9. Class Y capacitor according to claim 8, wherein the metal housing (6) is provided with an attachment point for mounting a heat dissipating component.

10. Class Y capacitor according to claim 8 or 9, wherein the first electric 5 conductor (2) and / or the first leg (4, 8, 9, 13, 18) is / are connected to the metal housing (6).11 . Inverter (23) with a class Y capacitor (27) according to any one of claims 1 to 10, which is connected with the first leg having the larger cross-section to a chassis w and / or ground and with the second leg to an AC line or a DC line.

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