Practical issues when calculating AC losses for magnetic devices in PCB implementations

In this paper, a method to calculate the ac losses (including skin effect and proximity losses) in planar magnetic devices having rectangular cross-section conductors is presented. A similar model to that employed in the losses calculation with round wires is developed for the mentioned conductors. The aim is to obtain a proper design procedure, especially for magnetic devices in printed circuit board (PCB) implementations. Basically, the losses model is based on the superposition of different losses in the wire (conduction and proximity losses) and also in an orthogonal decomposition of the field where the conductors are immersed. As a consequence, to provide us a computation time reduction, the number of functions, needed to calculate the proximity losses is reduced to one, as it occurs in round wires. This function and also the function that describes the conduction losses, both include the size and frequency dependencies, are calculated and tabulated by means of Finite Element (FEM) calculations. Thus, the ac losses are obtained with a computation time reduction employing the losses model developed with FEM field calculations. Finally, several prototypes are used to verify the proposed method and some optimization results are also extracted.