DE2118053A1 - Earth core for choke made from a mixture of ferromagnetic powder and insulating material binder - Google Patents

Description

Earth core for choke made from a mixture of ferromagnetic powder and Insulating material ties and insulating material ties The invention relates to an earth core for choke made of a mixture of ferromagnetic powder and an insulating material binder, which is pressed into molds, with great inductivity and high damping predominantly at Frequencies below 1 MHz for radio interference suppression in thyristor circuits, in particular with electronic brightness control devices.

In various electrotechnical areas, in particular telephone and high frequency technology, are used as choke cores, depending on the magnetic cores Task should exhibit a certain behavior. This behavior is largely determined by material and composition. For choke cores in the special Application for radio interference suppression in phase angle controls with thyristors it is important to find a favorable compromise with regard to the required properties and to find the material possibilities. On the one hand, there is a high initial permeability important, while on the other hand the saturation range should also be as high as possible.

In addition, there are also high requirements for low noise levels posed.

Using mixing ring cores it was possible to create non-linear chokes to develop interference suppression of thyristor circuits compared to the known Versions have significant advantages (new toroidal radio suppression chokes for special applications, journal for applied physics 301 volume 1t issue 1970). According to the German patent specification 364 451, it is also known to make magnetic cores a mixture of zinc-coated iron parts and shellac under high pressure in Molds to be pressed in order to use cores for telephone load coils high to obtain specific resistance. It is also from the German patent specification 761 191 known, mass cores for high frequency technology from an iron powder and to manufacture a thermoplastic insulating material such as polystyrene in an injection molding process, whereby an increased permeability is achieved.

The known core compositions and manufacturing processes exhibit however seldom permeabilities up to 10. Because of this, they are special at Brightness control devices (dimmers) not to be used5 because the maximum permissible here Volume is given by the normal flush-mounted boxes.

It has also been shown that with metal cores and with fired Ferrite cores as a result of the strong current changes in the phase control due to magnetostriction annoying Brwamge = noises occur, which are often used in living areas to forbid.

fence the invention, the task was set, in particular for electronic Brightness control devices (dimmers) in the living area to create a throttle that both their attenuation properties for radio interference suppression through high inductance and has great inherent attenuation as well as optimal with regard to the annoying humming noises Values achieved. As a solution, a throttle core was found, the mixture of a ferromagnetic powder and an epoxy resin content of less than 5%. The proportion of epoxy resin is around 4% to 5%.

In addition, the ferromagnetic powder has a grain size of 0.2 mm to 0.4 mm.

In the production of such a mass core, the ferrite and the epoxy resin powder is mixed well in the cold state and then in a Mold pressed under a pressure of about 3.5 t / cm2. This is followed by curing at 1200 to 1500 C for 1 hour.

Although the proportion of the epoxy resin binder is relatively low, the ferromagnetic particles are due to the extraordinarily high adhesive force of the binder held together very firmly, even under high mechanical stress no break occurs. Since epoxy resin is also a thermoset, the throttle core is resistant also higher operating temperatures, as they always occur in continuous operation.

Claims (4)

Claims ra assekern for throttle made from a mixture of ferromagriet powder and Insulating binder, which is pressed into shapes, with high inductance and high attenuation, mainly at frequencies below 1 MHz for radio interference suppression for thyristor circuits, especially with electronic brightness control devices, characterized in that the mixture of a ferromagnetic powder and an amount of epoxy resin from less than 5%. 2.) mass core according to claim 1, characterized in that the proportion of the epoxy resin is 4% to 5%. 3.) earth core according to claim 1 and 2, characterized in that the grain size of the ferromagnetic powder is 0.2 mm to 0.4 mm. 4.) Process for the production of mass cores with a composition according to claims 1 to 3, characterized in that the cold mixed ferrite powder and epoxy resin powder particles in a mold under a pressure of about 3.5 to / cm2 are pressed and a subsequent curing at about 1200 to 1500 C during 1 hour.