Study On The Influence Of The Particle Size Distribution On The Magnetic Properties Of Soft Magnetic Powder Core

As one kind of soft magnetic materials, soft magnetic powder cores have both high resistivity and high saturation flux density. They have been widely used in the electrical and electronic industries due to their excellent soft magnetic properties at the frequencies ranging from several kHz to hundreds of kHz. With the development of electrical and electronic industries, soft magnetic powder cores also get a rapid development in recent years.In this paper, the mechanically-crushed Fe-Si-Al powders were sieved into four groups with different size ranges. Then the phosphate insulation coating was applied to prepare the Fe-Si-Al soft magnetic powder cores and the effects of particle size distribution on the core’s magnetic properties were studied in detail. It was found that the increase of the percentage of the small particles results in the decreases of the effective permeability, the quality factor at low frequencies and the core loss at high frequencies, the improvements of the quality factor at high frequencies and the DC-bias performance and the deterioration of the core loss at low frequencies. The relatively best magnetic performance of the Fe-Si-Al powder cores with the effective permeability of about 60 was finally achieved as follows:the maximum quality factor is 164, the percent permeabilities at 50 Oe and 100 Oe are up to 76.3% and 49.3%, the lowest core loss at 50 kHz/1000 Gs is 269.7 mW/cm3.The gas-atomized Fe-5.5wt.%Si powders were sieved into four groups with different size ranges and the phosphate insulation coating was also applied to prepare the Fe-Si soft magnetic powder cores in this work. It was found that the increase of the percentage of the small particles results in the decreases of the effective permeability and the core loss and the improvements of the quality factor and the DC-bias performance. The relatively best magnetic performance of the Fe-Si powder cores with the effective permeability of about 60 was finally achieved as follows:the maximum quality factor is 138.4, the percent permeabilities at 50 Oe and 100 Oe are up to 95.8% and 81.1% and the lowest core loss at 50 kHz/1000 Gs is 541.9 mW/cm3.The effects of the particle size distribution on the distributed air gap, the demagnetization field and the eddy current within the powder cores were believed to be the main physical mechanisms determining the core’s magnetic properties.