Calculation of winding losses in high-frequency toroidal inductors using single strand conductors

The paper is concerned with the optimisation of inductor design to improve the design capability for these large, expensive and heat-producing magnetic components in power electronic circuits. The work focuses on toroidal inductors which consist of uniformly distributed, solid conductor windings on low permeability toroidal cores. It develops methods of calculating the eddy current losses in the windings. The basic analytical equations for losses in the windings are evolved and the problem of variable turn pitch that arises in the toroidal geometry is dealt with by means of an effective core diameter concept. Effective core diameters are presented graphically in terms of normalised parameters. The theoretical and graphical results given in the paper enable toroidal inductor designs to be optimised, and losses to be calculated in a rapid and convenient way. Experimental results are shown to agree well with the theoretical results presented in the paper.