铁磁元件直流退磁方法研究

Study of DC Demagnetization Method of Ferromagnetic Components

铁磁元件铁心剩磁通(剩磁)的存在会给电力变压器带来较大的励磁涌流并影响互感器测量精度。为了便捷的消除铁磁元件铁心剩磁,提出了一种采用极性反转直流源的直流退磁方法。该方法考虑绕组直流电阻的影响,通过微控制器计算并严格控制施加正负直流电源的脉宽,使铁心能分别达到负、正饱和点和磁通零点,达到退磁的目的。同时,根据各个阶段磁通的变化还可以计算剩磁和剩磁系数。并在电流互感器上展开试验,测得退磁后的剩磁系数绝对值<3%,与工频开路退磁法相当,而且所需退磁电源的功率仅不到6W,和工频开路退磁法相比大大减小了退磁电源的容量。验证了本文所述方法的准确性和可行性。

Residual flux of ferromagnetic core will bring inrush currents to power transformers and affect the accuracy of measurement current transformers(CTs).In order to eliminate the residual flux,an demagnetization method based on alternating polarity DC voltage is proposed in this paper.In this method,the duration of the applied DC voltage was calculated and controlled by micro-controller considering the winding resistance Rdc so that the magnetic core can reach the negative and positive saturation points,and zero flux point,respectively.In this way,the process of demagnetizing was accomplished.Meanwhile,residual flux and magnetic remanence coefficient can be obtained through the flux variation of each step during the whole process.In addition,laboratory experiments were conducted on CT.The measured absolute magnetic remanence coefficient is below 3%,which is close to open-circuit demagnetization method using rated-frequency diminishing alternating current.Meanwhile,the required power of power supply is below 6 W,which is much less than open-circuit demagnetization method.The experimental results validate the accuracy and effectiveness of the proposed method.