Composite Magnetic Material Of The Magnetic Circuit Theorem And The Displacement Variable Permeability Type Electromagnetic Induction

Based on the comparability between magnetic circuit and electro circuit, magnetic circuit theorem has become a powerful tool to analyze and calculate the magnetic field distribution. In constant current circuit, its current is constant and unrelated to wire size or resistance. Similarly, the magnetic flux through core section has been regarded as always the same by traditional magnetic circuit theorem on the basis of Gauss theorem, and it only can be used when the permeability of iron core tends to be infinite. If not, the iron core only can be taken as magnetic induction tube, and it commonly accompanies leakage flux. Recent years, micro-vibration power generation device based on ferrite core has aroused a lot of attention. Researchers try to improve its output power and much more attention has been paid to the physical characteristics of ferrite core in composite magnetic circuit.According to the traditional magnetic circuit theorem, this thesis takes the U-shape manganese-zinc ferrite as composite magnet, revises traditional magnetic circuit theorem, and studies the composite magnetic circuit theorem and its’ application in composite magnetic medium. Based on the new magnetic circuit, the matchup for permeability of manganese-zinc ferrite core and the output power of micro-vibration power generation device have been investigated. In this thesis, we take two different kinds of manganese-zinc ferrite cores as experiment samples, whose permeability are5000and15000, respectively. We made them into pair and got four kinds of composite magnets. Spatial magnetic density of different pairs under different external magnetic fields also has been detected. Experiment results show that much of the magnetic flux has been restricted inside the ferrite core, but there is still some diffusion. Thus, there is a permeability matchup problem about the U-shape manganese-zinc ferrite core, because the high permeability of ferrite core could not make good generating efficiency. Theory and experiment result have proved that composite core whose stator core of5000and oscillator core of15000is the best match. By means of high transient change rate of effective permeability, the electricity harvesting device based on micro-vibration by placement-permeability can get high output voltage through electromagnetic induction. Its output voltage not only relates to the change rate, but also to the impedance characteristic of its composite ferrite core which is the function of core gap and vibration frequency.The composite magnetic circuit theorem in this thesis based on the traditional magnetic circuit theorem but revised it, guided the selection of core match and provided powerful theoretical foundation to study the output power of electricity harvesting device. The electricity harvesting device based on micro-vibration by placement-permeability can work under vibration environment of low frequency and low amplitude, which owns wide application prospect and deserves intensive study.