Novel Array Eddy Current Sensor With Three-Phase Excitation

Abstract

Array eddy current testing (AECT) sensor is capable of inspecting a large area in a single probe pass resulting in a C-scan image, which is beneficial for customizing the profile of the part being inspected. This paper presents a novel AECT sensor with three-phase excitation. The sensor has two rows of excitation coils and a row of pickup coils. The excitation coils are driven by three-phase currents that are 120° apart in phase. The induced eddy current in the conductive sample shifts electrically along the phase variation direction of the excitation currents. As a result, the sensor does not need multiplexer resulting in advantages of lower cost, less noise and faster inspection speed. The background signal measured by the sensor is small if there is no defect in the sample. Therefore, the sensor has high relative sensitivity to the presence of defect. A 3D finite element method (FEM) model is utilized to study the operating principle of the sensor. A prototype sensor has been developed and tested, with which aluminum sample and carbon fiber reinforced polymer (CFRP) sample with machined defects are inspected. The experiment results demonstrate the feasibility of the sensor for fast imaging of conductive materials.