Analysis of EMI Reduction Effect of a Magnetorheological Fluid-Gap Inductor in a DC/DC Converter

In this paper, the electromagnetic interference reduction effect of a magnetorheological (MR) fluid-gap inductor in a dc/dc converter is investigated. For a realistic electromagnetic simulation, a prototype MR fluid-gap inductor is built and put in a typical buck converter setup, and the current waveform of the inductor is measured. Based on the measured current waveform, a 3-D time domain finite element electromagnetic analysis is performed considering non-linearity of an MR fluid and complex geometry of the winding. The rms and maximum values of the leakage flux and eddy current losses of the MR fluid-gap inductor are calculated and compared with those of the air-gap inductor. It is predicted that the eddy current heat source due to the leakage flux from the gap is reduced by as much as 75.6% for the MR fluid-gap inductor. To verify the simulation data, the leakage fluxes of both MR fluid-gap and air-gap types of inductors are measured in a dc/dc converter setup, and their experimental results are compared with calculated ones.