Study On Quantitative Pulse Magnetizing Technique And Device

Since the appearance of the first generation of permanent magnet SmCo5 in the early 60s of last century, till the wide application of rare-earth"magnet king"NdFeB nowadays, the permanent magnet materials have gone through more than forty years'development. Their permanent magnet properties have been improving continuously, with a higher intrinsic coercivity, stronger remanence and bigger magnetic energy products, which ensure the application of the permanent magnet materials in almost every field. In the process of production and application of the permanent magnet materials, the requirements for magnetizing and demagnetizing equipments have become more sophisticated, and they need to be improved continuously to be more intelligent, accurate and diversified. We study the quantitative magnetizing device applied to NMR magnetic field measurement techniques, which could change the remanence of the permanent magnet and thus achieve the quantitative regulation of the steady magnetic field.Firstly, we expound on some characteristics of the rare-earth permanent magnetic materials, respectively introducing its magnetization, retraction and demagnetization, etc. Based on these characteristics, we do the research on the method of quantitative magnetizing permanent magnet. Secondly, we analyze the pulse magnetizing principle and simulate the relationship between the pulse peak and the discharging circuit parameters by using MATLAB7.0 software, then we advance the design method of parameters and the choice of important components of the circuit. The traditional magnetizing machine-specific pulse energy-storage capacitor is replaced by the one made up of electrolytic capacitors connecting in series and parallel mixed, which lower the costs and reduce the volume of the whole system. Magnetizing head is made of hollow coil. In the course of design, the finite element analysis software ANSYS10.0 is applied to analyse the magnetic field of the coil. Finally we design the magnetizing head with more total turns, fewer turns of single layer and more layers as much as possible. In this way, although the coil inductance value increases and the pulse current peak decreases, the generated magnetic field peak is not small. The advantage of this choice lies in: the reducing of the pulse current peak lowers the requirements for the circuit component parameters, and also reduces the generated heat in the coil during the magnetizing process. It makes the design of whole system circuit simple and highly reliable.In this paper, we also introduce the hardware circuit design and software solution. The hardware circuit design mainly includes: main magnetizing circuit, switching trigger circuit, magnetic field measurement circuit, temperature detection circuit and control circuit. The central control chip adopts MCU C8051F020 to control the whole circuit. Its high integration reduces the surrounding circuit of the whole control system, which makes the control and software composition become more convenient and easy. In the design, quantitative magnetizing, saturated magnetizing and full demagnetizing functions are accomplished by software-composing, and the working status information of the system is provided by the terminal display.The generated pulse magnetic field of the quantitative magnetizing device ranges from 0～6T. Its precision is not less than 1%, and the uniformity is less than 5%. The device could regulate the remanence of the permanent magnet quantitatively. Finally, we carry on a further discussion about the system features according to the experimental facts. Experiments show that the device is simple, low cost, and it has a high magnetizing precision and speed, which could meet real needs.