Improvements in or relating to inductance coils comprising a ferro-magnetic core of highly-permeable ferrite

摘要

708,121. Inductances. PHILIPS ELECTRICAL INDUSTRIES, Ltd. April 17,1951 [April 20, 1950], No. 8991/51. Drawings to Specification. Class 38(2) In an inductance coil for signal frequencies exceeding 10 KE/sec, a ferromagnetic core of ferrite with a loss angle less than 0.06 and a Curie temperature greater than 80‹C is premagnetized by a constant magnetic field of such valve that the inductance of the coil is substantially independent of temperature. This field, which may be produced by a permanent magnet, is preferably at right angles to the field produced within the core by the signals. Both the permeability and the losses of the material are approximately halved. The core dimensions may be chosen so that loss increase from mechanical resonance is avoided. An inductance, may have a core part with a positive temperature coefficient combined with a part with such a value of premagnetization field that it has a negative temperature coefficient, so that the coefficient overall is zero. Specifications 708,127, 708,131, 708,132, 708,133, 708,134 708,135, 708,136, 708,137 and 708,140 are referred to.