Magnetic Properties And Loss Mechanism Of Soft Magnetic Composite Employed In Special Magnetic Component

Soft magnetic composite(SMC)is widely used in high power electronic components worked at kilohertz frequency bands,which are due to its high saturation magnetic induction and excellent loss characteristics and SMC has attracted a great deal of interest in recent years In this dissertation,the Fe-Si and Fe-Si-Al soft magnetic composites employed in special magnetic component have been prepared and their preparing process,morphology,complex permeability and loss mechanism have been investigated in details.A novel common mode choke in the work condition of big common mode current and an integrated inductor made of Fe-Si-Al/phosphate soft magnetic composite have been also prepared and their properties have been investigated.The result and discussion in this dissertation is benefit to the research and application of soft magnetic composite and also benefit to the study of magnetic component.The main contents of this dissertation are as follows:1.Fe-Si/glass soft magnetic composites with different glass content by using low melting glass as adhesive and insulating agent have been prepared and their magnetic properties have been investigated.SEM results indicate that the glass particles between different Fe-Si spheres soften and deform into flakes when annealing temperature is more than 400?,which reveals that the glass particles can play as an adhesive agent in SMC.Saturation magnetization of Fe-Si/glass composites is very high(up to 210 Am2/kg)due to the small volume ratio of glass in the composites.Permeability of Fe-Si/glass composites significantly increases when the annealing temperature is around melting point of glass,which is considered to be the result of stress release and distributed gap reduction caused by glass softening.Power losses measurement shows that the total magnetic loss of Fe-Si/glass composites(less than 2100 kW/m3 at 100 mT and 100 kHz)is lower than many reported data in literature.The eddy current loss of Fe-Si/glass composites is moderate,which is regarded that the glass particles between the Fe-Si spheres block the eddy current between different spheres.The SMC prepared by using low melting glass as adhesive and insulating agent is simpler and more environmentally friendly2.Fe-Si/SrFe12O19 soft magnetic composites with different SrFe12O19 content have been prepared and their microstructure and soft magnetic properties have been investigated.SEM morphology shows that Fe-Si spheres are surrounded by small SrFe12O19 powders,which can block the eddy current between different spheres.The saturation magnetization of all composites is more than 200 Amt/kg and such a high saturation magnetization of SMC has a definite relationship with SrFe12O19 ferrite.The permeability of Fe-Si/SrFe12O19 composites is moderate.Magnetic losses analysis reveals that Fe-Si/SrFe12O19 composites have excellent loss characteristics(less than 1800 kW/m3 at 100 mT and 50 kHz).Measured Pcv/f vs f data of Fe-Si/SrFe12O19 composites shows that the hysteresis loss increases and the eddy current loss decreases with SrFe12O19 content increasing in composites3.The Fe-Si-Al soft magnetic composites with different phosphoric acid solution content have been prepared and their soft magnetic properties have been investigated in details FE-SEM morphology shows that a uniform insulation layer of the phosphate formed on the surface of the magnetic particles.The permeability of the composite core is very high(up to 147.7).Magnetic losses analysis reveals that Fe-Si-Al composites have excellent loss characteristics(less than 550 kW/m3 at 100 mT and 100 kHz).Measured Pcv/f vs f data of Fe-Si-Al composites shows that the hysteresis loss increases and the eddy current loss decreases with phosphate content increasing in composites.The Fe-Si-Al soft magnetic composites with excellent soft magnetic properties provide great potential for expanding the application of various magnetic components like differential mode inductors worked at kilohertz frequency bands,especially the high permeability is benefit to reduce component volume and save costs4.A novel common mode choke in the work condition of big common mode current and an integrated inductor made of Fe-Si-Al/phosphate soft magnetic composite have been prepared and their properties have been investigated.Fe-Si-Al/phosphate composite exhibits relatively high permeability(bigger than 100)and low magnetic loss.Fe-Si-Al/phosphate composite is firstly selected to use in common mode choke.The DC bias measurement shows that the common mode choke exhibits good DC bias characteristics of common mode inductance because of the high saturation magnetic induction and distributed gaps in the core.The common mode choke shows excellent impedance performance because of frequency stability of the permeability.The differential mode inductance with a considerable value which is realized by the leakage inductance of the common mode choke can be used for differential mode electromagnetic interference noise suppression.The integrated inductor shows good DC bias characteristics and relatively low core loss.The integrated inductor with excellent performance is benefit to reduce component volume and weight,reduce core loss and save costs.