Field of the invention

Embodiments of the present invention relate to an EMC filter, in particular to a high-current EMC filter according to the independent claim.

Description of related art Feed-through components such as feed-trough filter or feed- trough capacitors are electrical components, which are provided in an electric power line. They consist in an electric circuit arranged around a conductor in a housing. The conductor extends the housing creating two outer contacts for connecting external elements. The elements of the circuit consist of capacitors, ferromagnetic materials or resistances, which are in many embodiments co-axial with the electric conductor.

Feed-through components are used generally for changing the transmitting properties of electric power or data lines. Such filters with for example a π-filter circuit are mainly used for wide band noise reduction of power lines to sensitive or noise generating devices. Such filter circuit consists mostly of one or two identical capacitive members and one ferromagnetic member. Until now the concentric arrangement of the elements of the circuit increases high frequency damping values. However, the depending on arrangement, the insertion losses of the filter could be rather high. Such feed-through components are known from DE4218171 , DE10240084 or DE4025159.

Furthermore, most of the feed-through elements are soldered or pressed with a conductive gasket to contact the different elements of circuit with each other. Brief summary of the invention It is one aim of the present invention to provide an EMC Filter, which will be more reliable and easier to assemble.

It is another aim of the present invention to create an EMC filter operable within a high frequency bandwidth. According to the invention, these aims are achieved by means of the feature of the impended claim. Dependent claims give advantageous embodiments.

Especially these aims are solved by an EMC filter unit with the features of the preamble of independent claim, characterised in that · the capacitor has a first face and a second face in opposition, each one of which comprises an electric terminal, wherein the faces are flat and parallel, and

• the capacitor is inserted and tightly held in position between the

conductive housing and the electric conductor so as to create an electric contact between housing and conductor and the corresponding terminal of capacitor.

One advantage comes from the fact that flat connection elements are arranged on both sides of the capacitors, which allows an easy manufacturing process without soldering. The invention can as well be used for 2-, 3- or 4-lines EMC filters.

Brief Description of the Drawings

The invention will be better understood with the aid of the description of an embodiment given by way of example and illustrated by the figures, in which:

Fig. 1 a shows a schematic view of a first embodiment of an inventive EMC filter; Fig. 1 b shows a side view of the inventive EMC filter;

Fig. 1 c shows the detail I of Fig. 1 a, which illustrates a conductive gasket between the housing and the capacitor; and

Fig. 2 shows s schematic view of a second embodiment of an inventive EMC filter;

Detailed Description of possible embodiments of the Invention

Fig. 1 a shows a schematic view of a first embodiment of an inventive EMC filter circuit 1 and Fig. 1 b shows a side view of the inventive EMC filter. The EMC filter circuit 1 comprises a conductive housing 2, which is grounded with not shown connection elements, and a rigid busbar 3 for carrying an electric power to which is superposed a noise component. Such filters are mainly used for wide band noise reduction of power lines to sensitive or noise generating devices. As seen in Fig. 1 a the busbar 3 is arranged in the middle of the housing 2 and extends on both sides. In order to hold the bus bar 3 and to isolate it from the housing 2 on both ends of the housing 2 an isolating material 22 is arranged. The isolation material could be for example plastic.

As seen in Fig. 1 b apertures 31 are arranged on both ends for the connection to external devices via not shown terminal or other means. The housing 2 will be closed in the lower side by a cover (not shown), and at each side has at least one lateral means 21 for fixing the house to any external device such as eyelets with an aperture. Advantageously the house 2 is electric conductive metal, e.g. aluminum. The filter comprises two main inductors 4 and capacitors 5. The inductors 4 arranged around the bus bar 3 consist of a ferromagnetic material such as ferrite with a gap, iron powder, sendust or similar. In one embodiment they have a rectangular shape with a central rectangular aperture, which accommodates the bus bar 3, and they increase an impedance of the central bus bar 3. The number of inductors 4 is given by the way of example and will be chosen according to the use of the inventive filter 1 .

Furthermore the capacitors 5 have each a first and a second faces 51 , 52 in opposition, each one of which comprises an electric terminal. The capacitors 5 are inserted solderless and tightly held in position between the conductive housing 2 and the bus bar 3. The first face 51 is thereby being juxtaposed to the bus bar 3 and the corresponding electric terminal on the first face 51 is in electric contact with the electric conductor. The second face 52 is being juxtaposed to the conductive housing 2, the electric terminal on the second face 52 is in electric contact with the conductive housing 2. Therefore the faces 51 , 52 are in direct electrical contact with the bus bar 3 and the grounded conductive housing 2. To increase the contact, the faces 51 , 52 can be provided with a conductive electrical layer 53. As seen in Fig. 1 c additionally to the electrical layer 53 an electrical gasket or mesh 6 is provided between the terminal of each face and the corresponding surface. Still it would be possible to have only one of both measures, either the conductive electrical layer 53 or the mesh 6. The number of capacitors 5 is four and given by the way of example only and will be vary according to the use of the inventive filter 1 . The capacity of the capacitors 5 will in an advantageous embodiment be identical. In order to achieve a good contact to the corresponding terminal said opposite faces 51 , 52 are advantageous flat and parallel and the capacitors 5 have a round or a rectangular shape. This guarantees a simple assembly of the capacitors 5 in the housing 2. The so formed EMC filter is filter with a double π-circuit. In another embodiment, it could be still a T-circuit or L- circuit to be constructed.

One advantage is that the construction of the EMC filter according to this invention is much simpler than known constructions of prior art filters and that this design and especially flat connection elements on both sides of the capacitors allow an easy manufacturing process. The inductors 4 can put onto the bus bar 3 and assembled with the material 22 into the housing 2. Finally the capacitors 5 can be put manually into place. Then the housing will be closed and fixed by the eyelet 21 or soldering pin on a device. Another advantage comes from the fact that no electrical contact has to be soldered inside the inventive EMC filter. Due to short connection of the capacitors between bus bar 3 and housing 2 it works with a high frequency bandwidth.

Fig. 2 shows s schematic view of a second embodiment of an inventive EMC filter 1 with two parallel bus bars 2 in a housing 3, where capacitors 5 are inserted between one bus bar 3 and the housing 2 in the same way as described as for Fig. 1 . Furthermore, one or more capacitor 5 can be inserted and tightly held in position between parallel electric conductors 3. These capacitors 5 have again a first face 51 and a second face 52 in opposition, each one of which comprises an electric terminal. The faces 51 , 52 are flat and parallel. The use of a conductive gasket or an electric conductive film between the electric terminals and the electric conductor 3 as described for Fig. 1 can be envisaged. In this embodiment, the inductors 4 can be separately around the electric conductor 3 (left and side inductor) or can be built as common core through which all electric conductors 3 go (shown in the middle). Furthermore, the man skilled in the art will understand that this principle can be applied to EMC filters having three or four bus bars 3.

Reference Numbers

1 EMC filter circuit

2 Conductive housing

21 Fixing means

22 Isolating material

3 Bus bar

31 Aperture

4 Inductor

5 Capacitor

51 First face of capacitor

52 Second face of capacitor

53 Conductive electrical layer

6 Gasket, mesh