مرکز منطقه ای اطلاع رساني علوم و فناوري - Computation of flux switching in magnetic circuits

Abstract :

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 total $\\dot{\\phi}(t)$ are distinguished and semiempirical models are proposed for each : 1) an initial elastic $\\dot{\\phi}$ spike during the rise time of $F, \\dot{\\phi}_{\\epsilon} = \\epsilon\\dot{F}$ , where ε is constant in time; 2) a decaying inelastic $\\dot{\\phi}$ starting at $t \\cong T_{r}$ , $\\dot{\\phi}_{\\rho i} = \\rho_{i}(F - F_{d}^{\\min}) \\exp [-(t - T_{r})(F - F_{d}^{\\min})/C_{i}]$ , where ρiand Ciare constants in time and $F_{d}^{\\min}$ is the static mmf threshold; and 3) the bell-shaped, main inelastic $\\dot{\\phi}, \\dot{\\phi} = \\dot{\\phi}_{p}{1 - [(2\\phi + \\phi_{s} - \\phi_{d})/(\\phi_{s} + \\phi_{d})]^{2}}$ , where, for given $F , \\phi_{p}$ is the peak of $\\dot{\\phi}, \\phi_{d}$ is the φ value on the static $\\phi(F)$ curve, and φsis saturation flux. Expressions involving switching parameters are given for $\\epsilon, \\dot{\\phi}_{p}$ , and φd. The agreement between these models and $\\phi(t)$ of a thin core is satisfactory. The main- $\\dot{\\phi}$ model is applied in a numerical analysis of three magnetic circuits: an unloaded core, a core loaded by $R, L, C$ , 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- $F$ and ramp- $F$ switching.