Computation of flux switching in magnetic circuits

A number of physical and semiempirical flux-switching models that have appeared in the literature are reviewed briefly and classified. A thin ferrite core is switched by essentially a step mmf (with short rise time Tr). Three components of the totalφ̇(t)are distinguished and semiempirical models are proposed for each : 1) an initial elasticφ̇spike during the rise time ofF, φ̇ε = ̇, where ε is constant in time; 2) a decaying inelasticφ̇starting att Tᵣ,φ̇rho i = ρᵢ(F - Fdᵐⁱⁿ) exp [-(t - Tᵣ)(F - Fdᵐⁱⁿ)/Cᵢ], where ρiand Ciare constants in time andFdᵐⁱⁿis the static mmf threshold; and 3) the bell-shaped, main inelasticφ̇, φ̇ = φ̇ₚ{1 - [(2φ + φₛ - φd)/(φₛ + φd)]²}, where, for givenF , φₚis the peak ofφ̇, φdis the φ value on the staticφ(F)curve, and φsis saturation flux. Expressions involving switching parameters are given forε, φ̇ₚ, and φd. The agreement between these models andφ(t)of a thin core is satisfactory. The main-φ̇model is applied in a numerical analysis of three magnetic circuits: an unloaded core, a core loaded byR, L, C, and a diode, and a core-diode shift register. The agreement between computed and experimental results is satisfactory, especially if different parameters are used for computing step-Fand ramp-Fswitching.