Computer design of induction coil cores

This paper presents a method for designing inductance cores of a given inductance which, when under the influence of a given applied dc bias current, must decrease by no more than a given percentage. A typical important application is the loading coil cores used in telephony. The inductance and its behavior under dc bias is determined by the core geometry and the magnetic characteristics of the core material. The material can be characterized by: Integrating the time rate of change of the flux yields an equation for the inductance in terms of the dimensions of the core and the two material parameters μu and c. A computer program, which systematically searches for the core that meets a number of dimensional constraints and has the minimum volume, was used to generate new core designs. Experimental determination of the material constant C for 2-81 molybdenum permalloy powders has revealed that , as predicted by the model. Lower Ni (50-65%) permalloys or sendust are not as suitable as core materials because their C values are higher.