The Q Contour-A Graphical Method for Characterizing Inductors

A graphical presentation is developed which shows Q an increase in inductance for every inductor in a family on one plot. The basic principle consists of plotting loci of constant Q in inductance-frequency coordinates. Lines of constant increase in inductance, minimum and maximum nominal inductance, and peak Q are also included. Information which conventionally would be scattered in several different places or not presented at all is thus brought together in one display. These plots very effectively present the characteristics of a single family of inductors. However, their most significant advantage is the convenience with which the characteristics of several families can be presented on one sheet for comparison and selection. The inductor designer can use the Q-contour concept to visualize the way in which existing or contemplated families complement each other in the inductance-frequency plane. The equations for the Q contour are derived assuming that an inductor can be represented with a lumped constant equivalent circuit over the frequency range of interest, and that high-frequency winding and dielectric losses are negligible compared to core losses.