GB404332A - Process of and apparatus for standardizing magnetic cores - Google Patents

Abstract

404,332. Inductances. JOHNSON LABORATORIES, Inc., 609, West Lake Street, Chicago, U.S.A.-(Assignees of Polydoroff, W. J. ; 609, West Lake Street, Chicago, U.S.A.) June 10, 1932, No. 16461. Convention date, June 27, 1931. [Class 37.] In order to standardize the losses in cores or compressed core material made of compressed powdered and insulated magnetic particles, particularly cores for inductance coils used for radio-frequency currents, the core is made with losses below the standard and the eddy-current losses are increased, after finishing the core, by breaking down the insulation of some of the particles. The core 1 is provided with a winding 2 forming part of a resonant circuit containing an ammeter 4 and supplied with an electromotive force of a certain frequency. The variable condenser 3 is adjusted until the circuit is in resonance with the applied electromotive force, the amplitude of the current at resonance being set as the standard to which all the cores are to be adjusted. A circuit consisting of a source 5 of high potential and electrodes 6 is applied directly to the core so as to form conductive paths within the core by breaking down the insulation between some of the particles, thereby increasing the eddy-current losses. This is continued until the deflection of the ammeter 4 is decreased to the standard reading. The core may be rotated during this process so that particles lying in a plane are affected by the discharge. The electrodes may be applied in the direction of the flux, as shown in dotted lines, in which case the permeability also is increased.