Influence of ID/OD ratio on static and dynamic magnetic properties of toroidal cores

The optimization of toroidal core shapes for use in self-saturating magnetic amplifiers requires a knowledge of the influence of the inside-diameter/outside-diameter (ID/OD) ratio on apparent core magnetic properties. A theoretical result has been derived assuming a parallelogram-shaped basic hysteresis loop. Since this result has several unexpected features of great practical interest, a rather elaborate experiment was performed which verified their existence. In one application, it has been possible to double the gain of a push-pull amplifier stage by changing the core height and radial build-up so as to increase the ID/OD ratio without changing the iron area.