Nikola Tesla Books
154 HIGH FREQUENCY APPARATUS others is the same, a repetition would be superfluous. Construction of the Core.-The core is composed of thin sheet iron or preferably silicon steel which may be obtained from transformer manufacturers. The sheet metal is to be cut into strips according to the specifications given in Fig. 1. The 2 by 6 inch strips are divided into two piles of 130 pieces each and these strips are assembled alternately with the ends overlapping two inches. The 1½ by 6 inch strips are next divided into four piles of twenty each and these are assembled alternately also. These packs are then to be placed above and below the assembled piles as shown in Fig. 3 to break the sharp corners. The piles are then wound tightly with tape and finally covered with several layers of press-board, preparatory to winding the primary and secondary. Winding the Primary and Secondary.-The primary is wound on one leg of the core and the secondary on the other. The two cores are then joined in a complete magnetic circuit by the end yokes as shown in Fig. 1. The primary winding consists of 125 turns of No. 10 D. C. C. copper magnet wire wound 25 turns per layer and five layers deep. Between each two layers of wire, a turn of press-board should be taken. The first and last turns of wire are held in place with loops of strong tape placed under the winding and drawn tight after the turns are in place. No shellac or other paint is used on the winding as the coils are to be immersed in oil when the transformer is completed. The secondary winding is in two sections, each containing 4200 turns of No. 28 enameled magnet wire, making 8400 turns in all. The wire is wound in layers about an inch wide and separated by a double thickness of oiled paper between each two layers of wire. The paper should be 1½ inches wide. In Fig. 6 is shown the method of
