Numerical Analysis of DC-Biased Eddy Current Sensor Considering Hysteresis Effects

An advanced eddy current (EC) sensor incorporating with direct current (dc) magnetizing unit is presented, and its sensor signals are evaluated numerically considering hysteresis behavior. In this article, we propose an efficient method to calculate sensor signals while considering both a moving magnetizer and a high-frequency alternating current (ac) excitation. The calculation process is divided into two sequential analyses. The first step is a time-domain simulation to calculate a gradual change of dc magnetic field from the moving magnetizer. Then, its solution of the magnetic flux density is stored and used to make a subsequent magnetization curve based on the fitting equation-based hysteresis model. The obtained sub-magnetization curve is used for a time-harmonic simulation, and the sensor signal can be finally obtained. We applied the calculation method to a prototype sensor, and it enables to evaluate sensor signals quantitatively at the different magnetizing field and defect size.