A novel method of measurement of loss in a track of a turn of a planar transformer for induction heating applications

Abstract

The new trend in power converters is to design planar magnetic components aimed at low profile. However, at high frequencies, the AC losses induced in the planar inductor and transformer windings become significant due to skin and proximity effects. This paper presents the design of a high-frequency planar transformer (HFPT) for an induction heating system. The aim of this design is to adapt the levels of voltage and current from the inverter to the resonant tank characteristics. We propose a planar structure of Litz in the primary of our HFPT to reduce the AC resistance of the planar conductor. The Litz structure is obtained with a technique of the turn’s division in four tracks and their intersection so that the current passes all over the turn.For the single secondary turn, the choice of the section is based on an analytical study compared to a 2D finite element modeling (FEM), and is determined according to the shape that represents fewer losses and responds to our needs.2D finite element modeling (FEM) was performed for three different primary turns’ structures; full coil, a turn with four parallel tracks and our Litz planar turn; to minimize losses. Simulation results show that the planar Litz conductor can lead to a lower AC resistance. The performance of this Litz structure is also verified by measurements on experimental prototypes.