Inner-Eddy-Current Transducer with Rotating Magnetic Field: Theoretical Model, Forward Problem

ABSTRACT This article presents a novel send-receive type of inner-eddy-current transducer. A rotating magnetic field created by three rectangular coils, fed by a triphased alternating-current system, was used for emission. The reception part is made from a circumferential array of coils, consecutively interrogated by measurement equipment. The source that creates the rotating magnetic field is described. The field created by this in free space is presented, and the forward problem using the volume integral method and dyadic Green's function for cylindrical layered media is solved. The experimental measurements are in good agreement with the predictions of the model.