Design of air-gapped magnetic-core inductors for superimposed direct and alternating currents

Using data readily available from manufacturers on standard magnetic-material properties and standard core sizes for air gap type cores, an algorithm designed for a computer solution is developed which optimally determines the air gap length and locates the quiescent point on the normal magnetization curve so as to yield an inductor design with the minimum number of turns for a given ac voltage and frequency and with a given dc bias current superimposed in the same winding. Magnetic-material data used in the design are the normal magnetization curve and a family of incremental permeability curves. A second procedure, which requires a simpler set of calculations, starts from an assigned quiescent point on the normal magnetization curve and first screens candidate core sizes for suitability, then determines the required turns and air gap length.