Research On Preparation And Properties Of Fe-Si System Soft Magnetic Powder Core

Soft magnetic powder core have particular properties, such as, high permeability under a dc magnetic bias field, relatively low core losses at medium and high frequencies (25kHz-500kHz), the high and wider constant permeability and so on. As inductance filter, frequency choke, switching main vibration core, inverter inductance, they are widely used in telecommunication, UPS, power source in solid-state laser, solar electrical energy generation and so on. This dissertation systematically studied the effect of insulation coating, pressing process and annealing on properties of FeSi system alloy soft magnetic powder core. Especially, based on annealing process deteriorates the insulation property of coating layer, the component design of coating layer according to inorganic phase diagram and the method of physics deposit inorganic salt were introduced. Based on the non-linear magnetization of the powder cores, the thesis researched on the quality factor of the Sendust powder cores under dc magnetic bias field. The mechanism and separation of power loss of FeSi system alloy soft magnetic powder core had been researched.The paper systematically studied the effect of insulation coating, pressing process and annealing on properties of FeSi system alloy soft magnetic powder core in theory and on experiment. The proper particle ratio and compressing pressure can effectively promote the effective permeability by effective demagnetizing factor N. The proper annealing process can effectively decrease the loss of magnetic powder core.Inorganic phosphate-borate salt insulating coating layer was designed, by using optimized compressing pressure and annealing process, high performance Sendust powder cores were prepared. According to optimized Sendust alloy DO3phase transite temperature is650℃, sodium metaphosphate and sodium metaborate were designed as insulating coating layer. The corresponding magnetic properties of powder core show:the effective permeability is119, loss is below75mW/cm3at50kHz/50mT.Sodium silicate glass was designed as Fe-Si aolly powder core insulating coating layer. Because of optimized Fe-Si aolly DO3phase transite temperature is500℃, sodium oxide and silicon oxides have higher melting point than that temperature, the constituent of insulating coating layer have good thermal stability. Two-liquid phase area was selected as component of insulating coating layer considering the electromagnetic and constructs property.The quality factor of the Sendust powder cores under dc magnetic bias field were investgeted on the basis of deviation of linear magnetization. The propeties of curves at varied frequency was analysised, efficiency of operations was promoted. The quality factor of under dc magnetic bias field can be improved by changing the effective permeability and amplitude of ac magnetic bias field.The mechanism and separation of power loss of Sendust powder cores had been studied. The hysteresis loss (Ph), eddy current loss (Pe) and residual loss (Pr) were separated from the total power loss of Sendust powder cores by extrapolating the P/f～f plots. This result found that:1) the total power loss is made up of hysteresis loss (Ph) and eddy current loss (Pe), and the residual loss (Pr) can be ignored;2) at300kHz, the power loss composition of jue125with low hysteresis loss is very different from that of/ue60with low eddy current loss.The mechanism and separation of power loss of Fe-6.5%wt Si powder core had been studied. The hysteresis loss (Ph), eddy current loss (Pe) and residual loss (Pr) were separated from the total power loss of Fe-6.5%wt Si powder core by extrapolating the P/f～fplots. This result found that the total power loss is made up of hysteresis loss (Ph) and eddy current loss (Pe), and the residual loss (Pr) can be ignored.