Cost-effective and configurable-diameter heating areas for induction cooktops via passive inductors

In domestic applications of induction heating, high efficiency is achieved when the diameter of the vessel to be heated is similar to the size of the inductor coil. Current market trends demand flexibility of use and consequently, induction cookers usually incorporate medium-sized inductors with several concentric ring-shaped inductors that will be activated or not depending on the vessel diameter. This solution requires an extra electronic converter for each concentric ring. Thinking of cost-effective solutions, this work proposes the use of passive resonator coils concentric with a unique active coil. The proposed solution does not require a power supply for the concentric passive coils, thus reducing costs by eliminating electronic converters. In this work, a finite element analysis of the coil system is carried out to determine the impedance of the energized coil and the power dissipation distribution in the vessel. The proposed solution is validated using experimental prototypes.