GB2026241A

GB2026241A - Radio anti-interference capacitor

Info

Publication number: GB2026241A
Application number: GB7924310A
Authority: GB
Original assignee: INT STANDARD
Current assignee: INT STANDARD
Priority date: 1978-07-14
Filing date: 1979-07-12
Publication date: 1980-01-30
Also published as: DE2830961A1; DE2830961B2; GB2026241B; DE2830961C3

Abstract

A wound ratio anti-interference capacitor comprising a first dielectric foil (1), two conductive coatings (2,3) on one surface of the first dielectric foil, and a metal foil (5) arranged between the other surface of the first dielectric and a second dielectric foil (6), the metal foil forming the outer turn of the capacitor roll and having an external connection (11). Thus several capacitances are combined in one roll to act as X- or Y- capacitors with self healing capability and occupying a small volume. <IMAGE>

Description

SPECIFICATION Radio anti-interference capacitor The invention relates to a radio anti-interference capacitor comprising several capacitances combined in one capacitor roll, for acting as X- or Y-capacitors, in which two coatings on one surface of a first dielectric foil are overlayed by a third coating in such a way that an internal series connection results.

For the elimination of radio interference, especially of compact equipment there is generally used a high-capacity capacitor of class X and either one or two low-capacity capacitors of class Y. In so doing, the X-capacitor is inserted between the conductors of a network while the one or more Y-capacitors are inserted between the conductor and ground. If the X-capacitor as well as the one or more Y-capacitors are housed in a common casing, there is spoken of a combined X-Y-capacitor arrangement.

Such types of radio anti-interference capacitors serving as the shunt elements of radio-frequency voltages which, besides the usual values prescribed for capacitors, are still to have certain radiofrequency properties, have very large dimensions when manufactured in accordance with the conventional winding technique.

From the German Offenlegungsschrift (DE-OS) 2,229,407 there is known a radio-anti-interference capacitor employing a paper or plastic-foil dielectric, in which one capacitance is accommodated in common with a second capacitance in one capacitor roll: two coatings evaporated on one surface of a plastic foil or of paper, are covered by a third coating likewise evaporated on to a plastic-foil or paper. In this way both capacitances are series-connected and combined to form one capacitor which may be used either as an X-capacitor or as a Y-capacitor. With the aid of such an arrangement it is possible to achieve, in particular, improved properties with respect to the glow inset potential. For an X-Y-capacitor arrangement, several such capacitors are required.

From the German Auslegeschrift (DE-AS) 1,011,527 there is known an electric roll-type capacitor which has a self-healing effect as well as a built-in protection against inadmissible temperatures occurring locally inside the roll: For this purpose, one of its coatings is metallized on to at least one side of a dielectric tape and made so thin as to burn out in the event of breakdowns at the breakdown point. The other electrode whose melting temperature is lying below the destruction temperature of the capacitor dielectric, consists of a self-supporting foil.

According to the present invention there is pro; vided wound radio anti-interference capacitor comprising a first dielectric foil, two conductive coatings on one surface of the first dielectric foil, and a metal foil arranged between the other surface of the first dielectric foil and a second dielectric foil, the metal foil, as a dead foil, forming an outer end turn of the capacitor roll and providing an internal series connection, whereby several capacitances are combined in one capacitor roll for acting as X- or Y-capacitors.

In one embodiment of the invention, a particularly simple construction of the radio anti-interference capacitor, the first dielectric foil is designed to be wider than the second dielectric foil, with the latter in turn, being designed to be wider than the metal foil, one sprayed metal layer each at the face ends of the roll contacts one coating on the first dielectric foil and the end winding is likewise contacted.

The invention will now be explained in greater detail with reference to an embodiment schematically shown in Figures 1 and 2 of the accompanying drawings, in which: Figure 1 shows the layer structure at the beginning of the capacitor roll, and Figure 2 shows the layer structure at the end of the capacitor roll.

In the drawings, the reference numeral 1 indicates a polypropylene foil as the first dielectric foil. It has a thickness of 15 microns. This polypropylene foil 1 is provided with two metallized coatings 2 and 3. These metallized coatings 2 and 3 are in such a way deposited on a surface of the polypropylene foil 1 that the centre thereof remains as a non-metallized strip 4. The metallized coatings 2 and 3 consist of evaporated aluminium or zinc. The reference numeral 5 indicates a metal foil. This metal foil 5 has a thickness ranging from 7 to 9 microns and consists of a tin-lead alloy. The reference numeral 6 indicates a non-metallized polypropylene foil serving as the second dielectric foil. This polypropylene foil 6 likewise has a thickness of 15 microns.

The metal foil 5 is arranged between the polyp ropylenefoil 6 and the non-metallized surface of the polypropylene foil 1, partly covering the metal coatings 2 and 3. The polypropylene foil 1 is designed wider than the non-metallized polypropylene foil 6 and the latter, in turn, is designed wider than the metal foil 5. Sprayed metal layers 7 and 8 are deposited on both face sides of the capacitor roll; they may be applied either by way of spraying, metal-spraying, or in any other way. The sprayed metal layers 7 and 8 contact the metal coatings 2 and 3 on the polypropylene foil 1. At the end of the capacitor roll, as is shown in Figure 2, the metal foil 5, as a dead foil, forms the end winding. This end winding is contacted.

The radio anti-interference capacitor comprises a lead-in terminal 9 electrically connected to the sprayed metal layer 7, a lead-in terminal 10 electrically connected to the sprayed metal layer 8, and a lead-in terminal 11 electrically connected to the metal foil 5 for serving as the end winding.

As will be seen from Figure 2, there will result from this a first Y-capacitor via the terminals 9 and 11, and a second Y-capacitor via the terminals 10 and 11, as well as one X-capacitorvia the terminals 9 and 10, in an internal series connection; in this arrangement the metal foil 5 serves as a dummy electrode.

In this way there can be provided a radio antiinterference capacitor in a X-Y capacitor arrangement formed of one X-capacitor and two Ycapacitors, having an extremely small volume. The radio anti-interference capacitor, in addition thereto, operates with a high operational reliability. With such a layer structure there is not only achieved a very space-saving arrangement, but owing to the coatings evaporated on to the first dielectric foil there is also achieved a self-healing effect in the case of electric breakdowns, owing to the coatings evaporated on to the first dielectric foil, and owing to the metal foil there is achieved a protection against inadmissible heatings occurring locally inside the capacitor roll.

Claims

1. Wound radio anti-interference capacitor comprising a first dielectric foil, two conductive coatings on one surface of the first dielectric foil, and a metal foil arranged between the other surface of the first dielectric foil and a second dielectric foil, the metal foil, as a dead foil, forming an outer end turn of the capacitor roll and providing an internal series connection, whereby several capacitances are combined in one capacitor roll for acting as X- or Y- capacitors.

2. Anti-interference capacitor as claimed in claim 1, wherein the first dielectric foil is wider than the second dielectric foil, with both, in turn, being wider than the metal foil, wherein the face sides of the capacitor roll each have one sprayed metal layer contacting respective conductive coatings, and said end turn is likewise contacted with a sprayed metal layer.

3. Anti-interference capacitor as claimed in claim 1 or 2, wherein the metal foil is formed of a tin-lead alloy.

4. Anti-interference capacitor as claimed in claim 1, claim 2 or claim 3, wherein the first dielectric foil is formed of polypropylene whose one surface is provided with two side-by-side metal coatings in such a way as to form in the centre a non-metallized strip.

5. Anti-interference capacitor as claimed in any of claims 1 to 4, wherein the second dielectric foil is formed of polypropylene.

6. Anti-interference capacitor as claimed in claim 3, wherein said metal foil has a thickness in the range of 7 to 9 microns.

7. Anti-interference capacitor as claimed in claim 4, wherein the first dielectric foil has a thickness of 15 microns.

8. Anti-interference capacitor as claimed in claim 5, wherein the second dielectric foil has a thickness of 15 microns.

9. Anti-interference capacitor as claimed in claim 4, wherein the conductive coatings are made of aluminium zinc.

10. Awound radio anti-interference capacitor substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.