GB444564A - Improvements in or relating to high frequency inductance coils - Google Patents

Abstract

444,564. Transformers. POLYDOROFF, W. J., 609, West Lake Street, Chicago, U.S.A. March 4, 1935, No. 3446/34. [Class 38 (ii)] [See also Group XXXVI] A high - frequency inductance coil or transformer comprises a comminuted magnetic core wound with Litz wire having a strand diameter of substantially ten times the average grain size of material of the e magnetic core, the winding being divided into sections, spaced from one another along the magnetic axis, each section consisting of a multilayer coil whose radial depth is at least equal to its width. In the construction shown in Fig. 1, the coil is divided into three bank-wound multi-layer sections alpha separated by ribs b on an insulating former c. The cylindrical core d is pushed into the former c so that it is linked with all the coil sections alpha, and is adjustable by means of a screw-threaded rod e passing through a tapped hole in the former c. In a modification, Fig. 2, the sections a are of the self-supporting type of multi-layer winding, and are air spaced axially along a plain cylindrical former c. The magnetic core consists of a cylindrical rod d passing through the former c and engaged at its ends by a U-shaped yoke e. The rod d is adjustable relatively to the former c and yoke e for adjusting the inductance to the desired value. In the construction shown in Fig. 3, an outer core part f in the form of a hollow cylinder flanged at both ends surrounds the former c so as to produce a nearly closed magnetic circuit. The cylinder is split circumferentially into two parts at g to permit assembly. The core d may be adjustable by a screwed rod as shown, or the core itself may be screw-threaded to engage a corresponding screw-thread in the former c so that axial adjustment may be effected by rotating the core, as by a screwdriver inserted in a slot. The coil sections may alternatively be of the flat spiral or flat pancake type, but it is stated that the best results are obtained when the radial depth of each section is approxi.- mately equal to its width. As a result of the relation between the diameter of the strands of the Litz wire and the degree of subdivision of the magnetic material of the core, the core losses are approximately equal to the copper and dielectric losses. The core material may be that described in Specification 403,368, the average size of grain particles varying from 0À5 micron for a frequency of 1500 kilocycles per second to 30 microns for a frequency of 100 kilocycles per second.