GB1383446A - Radio interference suppressors - Google Patents

Abstract

1383446 Inductors SIEMENS AG 29 Feb 1972 [23 April 1971] 9189/72 Heading HIT A choke for interference suppression has a winding 8 formed on a core 1 comprising at least two annular parts 2 and 3, stacked coaxially. A first part 2 is of magnetizable iron laminations or wound strip made from, e.g. a silicon containing ferrous alloy and the remaining part is of a ferrite material, the ferrite parts having at least one air gap or slot. The iron laminations may alternatively be of an unalloyed deep drawn iron material. Two radial air gaps can be produced by forming the ferrite annulus in two halves and placing the halves almost together, but preferably a single radial air gap is provided. Instead of gaps extending completely through the ferrite, incursions or slots may be formed on the inside of the surface of the annulus so that the effect of air gaps is achieved and noise due to magnetostriction is kept to a minimum. In one embodiment of the invention, the effective cross-sectional area of the ferrite core section is made equal to or greater than that of the laminated core section, which is made up of 17 ring laminations. In a further embodiment, the cross-sectional area of the ferrite core section, which has a height of 3 mm., is a third of the total cross-sectional area of the core. The casing 4 is filled with a potting resin, 6, to which 40% of ground quartz has been added, and which remains elastic after setting. The resin penetrates between the core sections and laminations to secure sound damping. The casing is surrounded by a double layer of insulated copper wire, the winding direction, but not the winding sense of which is reversed after the 1st layer has been completed. An air gap or slot 0À2 to 0À3 mm. wide is ground in the core section 3. In one particular arrangement of the invention having a winding of current rating 2À5 A, the core has an inner diameter of 20 mm. and an outer diameter of 30 mm.