A simple noniterative procedure for designing naturally-cooled high-frequency inductors and transformers based upon limitation of the maximum device temperature

Abstract

Simple noniterative procedures for designing high frequency (>10 kHz) naturally-cooled transformers and inductors are described which are based on limiting the component temperature to a specified maximum value when rated currents and voltages are applied to the component and the ambient temperature is at a specified maximum. The procedure uses the surface-to-ambient thermal resistance, which includes the effects of convection and radiation, to relate the maximum surface temperature to the maximum allowable power dissipation in the device. The allowable power dissipation in turn is expressed in terms of the allowable current density in the winding and the allowable flux density in the core. These relationships form the basis of design procedures which proceed in a straight-line path without any iterations from input specifications derived from power converter design considerations to the design of the inductor or transformer. Experimental measurements indicate that calculated thermal resistances are in good agreement with measured values. The intuitive physical basis of the procedures makes it much easier for students, even undergraduates, to learn magnetic component design compared to other approaches. >