特高压直流换流阀饱和电抗器用超薄取向硅钢涂层制备与性能评估

Preparation and Performance Evaluation of Ultra-thin Grain-oriented Silicon Steel Coating for Saturable Reactor of Ultra-high Voltage Direct Current Converter Valves

饱和电抗器是保护特高压直流换流阀中晶闸管的核心设备,而超薄取向硅钢是制造饱和电抗器铁心的关键材料。本研究以磷酸铝、纳米硅酸铝以及铬酸酐为主要原料,制备了一种超薄取向硅钢表面无机绝缘涂层;利用扫描电子显微镜(SEM)和X射线能谱仪(EDS)分别对涂层形貌与成分进行了表征与分析,并定量分析了涂层厚度与降损率之间的关系;采用任意波形磁场激励测量系统研究了超薄取向硅钢在不同频率、拉应力、谐波次数/含量/相位差条件下的磁性能、磁致伸缩及噪声特性。结果表明:在700℃/20 s最优烧结固化工艺下,涂层附着性为A级、绝缘电阻系数达22.5Ω·cm 2/片;建立了铁损降低率ΔP与涂层厚度δ之间的数学方程,自变量δ的有效取值区间确定为0.3~1.5 mm;得到薄带在50 Hz^10 kHz频率,5次、7次、9次、11次谐波及0°、90°、180°相位差条件下的损耗变化规律;外加拉应力从0 MPa增加至20 MPa过程中,带材的磁致伸缩系数(λp-p)和噪声(L vA)先下降后上升,在4~5 MPa拉应力条件下λp-p和L vA达到最低点。本工作研制的超薄取向硅钢涂层和磁性能关键指标满足特高压工程应用要求,研究结果可支撑饱和电抗器铁心结构设计与加工工艺优化,推动高品质超薄取向硅钢带材国产化。

Saturated reactor is the key equipment which can protect the thyristor in ultra-high voltage direct current(UHVDC)converter valve,and ultra-thin grain-oriented(UTGO)silicon steel is the core material for the manufacture of saturable reactor core.In this paper,an inorganic insulating coating on the surface of UTGO steel was prepared by using aluminium phosphate,nano-aluminium silicate and chromic anhydride as the main raw materials.The morphology and composition of the coating were characterized by scanning electron microscopy(SEM)and X-ray energy dispersive analysis(EDS),and the relationship between coating thickness and reduction rate of core loss was quantitatively studied.The magnetic properties,magnetostriction and noise characteristics of UTGO steel at different frequencies,tensile stress,harmonic number/content/phase difference were studied.Results show that,under the optimum sintering and solidification process at 700℃/20 s,the adhesion of the coating is grade A and the insulation resistance coefficient reaches 22.5Ω·cm 2.The mathematical equation between reduction rate of core lossΔP and coating thicknessδis established,and the effective range of independent variableδis determined to be 0.3—1.5 mm.The variation rules of core loss of thin strip at frequencies of 50 Hz—10 kHz,5 times,7 times,9 times,11 times harmonics and phase difference of 0°,90°and 180°were obtained.When the applied tensile stress increases from 0 MPa to 20 MPa,the magnetostrictive coefficient and noise decrease first and then rise,theλp-p and L vA reach the lowest point under 4—5 MPa tensile stress.The key parameters of coating and magnetic properties meet the requirements of UHVDC engineering application.The results can support the structural design and processing optimization of saturated reactor core,and promote the localization of high quality UTGO steel strip.