Circuit Model of Choke Coils for Approximating Frequency-Dependent Winding Losses

Both windings and magnetic material cause losses in choke coils. For the efficient design of choke coils, a model of these losses is required where they are considered separately. In this paper, we focus solely on the winding loss. There are a number of methods to determine the winding loss. Most of them are based on numerical methods for computing electromagnetic fields like, e.g., the finite element method (FEM). Unfortunately, these methods are computationally expensive and have significant limitations. For instance, it is not feasible to consider special cases like, e.g., litz wires or complicated winding or core geometries. This paper introduces a computationally efficient and more universal approach for determining winding losses. The presented method is based on firstly measuring the frequency-dependent resistance of the winding, followed by a numerical approximation of this resistance via a network of passive components based on the Levenberg-Marquardt optimization method. Finally, the winding losses of a choke coil can be computed under real operating conditions by investigating the resulting network using a conventional circuit simulator. Simulation results of a choke coil with a flat wire show a high accuracy when compared to three-dimensional (3D) FEM simulations despite of its tremendously smaller computational complexity.