Radio interference elimination choke for suppressing impulse like interference voltages

Claim 1

A radio interference elimination choke for phase control switching circuits comprising a magnetic impedance core of two annular axially superposed partial cores, a cup and a cup cover housing said cores, at least one coil carried about said cup and cup cover, a first of said partial cores including iron sheet material containing 2 to 4% Si having high electric losses in the frequency range of 5 to 15 kHz for attenuating transients which are due to impulse-like currents applied to said coil, said first partial core having a cross section accounting for 65 to 85 percent of the effective cross section of the impedance core, a second of said partial cores including ferrite material having a permeability of at least 200 in the frequency range up to 10 MHz, said impedance core exhibiting high losses due to the effect of the ferrite material in the frequency range of from 10 to 300 MHz with a permeability which decreases with increasing frequency.