Acoustic Noise Characteristics and Magnetostriction of Fe-Si Powder Cores

Fe-Si powder compressed cores have been widely used as reactors in the powder conditioning systems (PCS) of photovoltaic applications and electrical vehicles. Reduction of acoustic noise from the reactor is important when the PCS is installed indoors. In this paper, magnetostriction of the Fe-Si powder cores was investigated in connection with acoustic noise from the reactors assembled with Fe-Si cores. A dummy gage in the coil, wound noninductively, is useful in eliminating the contribution of thermal expansion of cores under strain. Magnetostriction varied with the mechanical strength of the Fe-Si core, which is dependent on the conditions of impregnation. Magnetostriction of the cores was several ppm under the maximum field of 18 kA/m. The Fe-Si cores with lower mechanical strength show lower magnetostriction and thus lower acoustic noise. Strain due to Maxwell force is much larger than that of magnetostriction in the rectangular-type reactor.