Proximity-effect loss calculations for a discontinuous-mode PFC inductor utilising a multifilar winding construction

A method for calculating proximity-effect losses in a discontinuous-mode power-factor-correction inductor is examined with regard to simple multifilar windings. Calculation of effective winding AC resistance R_ac is performed for each switching pulse, which in turn is multiplied by the square of the I_rms for that pulse. The loss value for each pulse is then summed for all pulses to determine the winding loss. This calculation is sensitive to conductor diameter and winding arrangement, particularly the number of layers. Calculations are then used to target the optimum winding arrangement, within the application constraints, for minimum winding loss and compared with measured results. The general agreement between calculation and results demonstrates that this approach is a useful tool in the initial design of such an inductor. The tenor of the paper is the examination of ´limited-resource´ or low-volume solutions to the aforementioned losses; therefore Litz-wire versions are not examined, as they represent initial ´high-cost´ solutions.