Research On Electric Characteristics Of MOV And Its Application In Pulsed Power

The Metal Oxide Arrestor (MOA), composed of metal oxide varistor (MOV), is a perfect protector for over-voltage. The superconducting technology is a promising topic in the development of electrical engineering in the 21st century, which will greatly change the power industry, can also be used in pulse power technology. However, protective technology under low temperature is fundamental for superconducting technology and pulse power technology. If MOV is used for protection or else in low temperature, characteristics of MOV in low temperature must be studied.In this paper, the author firstly studied AC/DC characteristics of MOV in low current regions, and analyzed characteristics of MOV under pulse which produced by impulse oscillating generator and lightning generator, and then the author compared the results at liquid nitrogen temperature (77K) with the corresponding results that got from normal temperature. Based on these results from the above experiments, the author put forward the protective scheme of high temperature superconductive (HTS) magnet using MOV, and brought forward other application about MOV in HTS pulse power technology. The paper mainly contains seven contents as follow:(1) Analyzed and proved the Method of Synthesizing Vector(MSV) in order to deal with datum that got from experiments in low current regions;(2) Discussed the application of filter technique based on wavelet transformation in impulse wave evaluation, by using this method, noise signals were drawn out from signals of impulse experiments.(3) Analyzed AC/DC characteristics of MOV in low current regions, and discussed characteristics of MOV under pulse which produced by impulse oscillating and lightning surge experiments, then compared the results at liquid nitrogen temperature with the corresponding results that got from normal temperature. Results show that at liquid nitrogen temperature some characteristics of MOV, i.e. absorbing ability and residual voltage, are better than normal temperature. Some characteristics of some type of MOV at liquid nitrogen temperature, e.g. non-linear and brittleness are worse than normal temperature. In another hand, feedback speed of MOV is so swift that we can even ignore the delay, and above all indicates protective character of MOV under pulse is good at liquid nitrogen temperature.(4) Put forward selection method using MOV for HTS pulse magnets inner protection, analyzed and proved the method by experiments and simulink analysis.(5) Discussed microstructure change of MOV after it was destroyed by pulse which was released by HTS magnet, and analyzed the destroyed theory of MOV under this pulse,then put forward the advice about MOV's amelioration when it was applied in HTS magnet protection.(6) Based on the discharge experiment of a small HTS magnet, put forward a pulse form network (PFN), then analyzes and proves the method by experiments.(7) Based on the electromagnetic characteristics of MOV and HTS magnet, a PFN based on HTS pulse magnet and transformer was designed, thereinto, MOV is a protector for the HTS pulse magnet and transformer, and it can also sharp the output wave.