Low Thd And High Permeability Ferrite Material And Adsl Transformers

In this dissertation, MnZn ferrite material with low THD(Total Harmonic Distortion)and high initial permeability were prepared by oxide electronic ceramic process, The preparation process and mechanism of MnZn ferrite with low THD and initial permeability were studied deeply. To make sure the effect of initial permeabilityμi and coefficient of hysteresis constantηÎ', the composition, the mode of milling, diameter of powder, calcining process, different additives, sintering temperature and holding time were investigated detailedly. Using MnZn ferrite core with low THD and high initial permeability, the design of ADSL transformer was followed. At last, analysis of factors on performance of ADSL transformer is accomplished.The results show that the key of preparing low THD and high initial permeability MnZn ferrite materials are how to reduce the coefficient of hysteresis constant and increase initial permeability. So accurate composition and optimum calcining conditions can gain active calcining powder; proper combination of additives can improve the characteristic of the grain and grain boundary; optimum process of ball milling can got fine granularity of powder and distributing of granularity; the growth of grain and grain boundary can come into being under the appropriate condition of sintering temperature,oxygen atmosphere and holding time finally. The powder based on the composition of Fe2O3:52mol% ZnO:22mol% Mn3O4 26mol% was calcined in 2 hours at 830℃. Then after adding the combination of additives(including CaCO3,Bi2O3,MoO3,V2O5 and TiO2) and milling under the medium of iron ball in 2 hours, MnZn ferrite with the initial permeabilityμi which is 10000±30% and coefficient of hysteresis constantηÎ'which is less than 1.4×10-6 is accomplished, which have the same properties as H5C2 of TDK, under the condition of sintering temperature of 1400℃,holding time of 6 hours and oxygen atmosphere of 4%.At the second part of this dissertation, it is the optimizing design of ADSL transformer with the MnZn ferrite core of low THD and initial permeability. The effect of coil turns, gas gap length and wire winding model on performance of ADSL transformer were studied detailedly, the design of ADSL transformer is accomplished. the results show that optimum ADSL transformer with gas gap length of 0.17mm﹑coil turns of 26Ts and wire winding model of hierarchical winding of primary and secondary coil and the winding of two ways in secondary coil.Its parameters of performance are as follow: Inductance(L=120μH±10%), Insert Loss(IL≤0.5dB), Leakage Inductance(Li≤10μH), Resistance(Rs≤1?), Interelectrode Capacitance(Cww≤50pF), Total Harmonic Distortion (THD≤-80dB).