A New Method to Measure the Residual Flux by Magnetic Sensors and a Finite-Element Model

When the power transformer is connected to the power grid, a surge of inrush current may occur as a result of residual flux. In order to mitigate this effect, measurement of residual flux is necessary. In this paper, a method for measuring the residual flux of ferromagnets was proposed, utilizing magnetic sensors and a finite element model. Residual flux originated from residual magnetization, which could be obtained from a matrix of spatial magnetic flux density measured by sensors and the conversion matrix calculated from the finite element model. By combining the residual magnetization with the background magnetic field, the residual flux could be determined. Experimental results confirmed the accuracy of the proposed method, which was particularly suited for measuring non-uniform residual flux, and also enabled determination of residual flux direction. In comparison to existing methods, this approach offered significant advantages.