Design and Experiment of a Two-Coil Magnetic Core Inductor Used for the Stepped Eddy Current Thermography Technique

A two-coil magnetic core inductor that works under a low-frequency alternating current is proposed to increase the detection area of SECT (Stepped Eddy Current Thermography). As the amplitude of the alternating current is small, the heating problem of the coil is ignored. And the cooling equipment is reduced that decreases the cost of the detection system. Additionally, the split structure inductor is studied, which confirms this structure is suitable for SECT and provides a reference for the design of an adjustable exciting inductor. The detection system for detecting subsurface defects is established in numerical models and experiments. The results indicate this detection system is suitable for detecting large-sized subsurface defects in a large area. Conclusions of the amplitude contrast in the heating process and the phase contrast in the cooling process suitable for defect depth analysis are obtained through the post-processing of thermal data.