Generalization of the Ideal Crack Model for an Arrayed Eddy Current Sensor

The ideal crack model is generalized to an arrayed eddy current sensor with the assumption that its coils are connected in series and fed by a current source. We associate the superposition theorem to the reciprocity theorem to reduce the 3-D electromagnetic problem to a 2-D axisymmetrical one, combined with the evaluation of an integral equation. We derive the formula that permits the evaluation of the impedance variation of each coil, taking account of the interaction between the coils.