DEVELOPMENT OF THE EDDY-CURRENT FLAW DETECTOR FROM U-TYPE MAGNETIC CIRCUIT WITH THE PURPOSE OF COMPENSATION OF EXTERNAL INTERFERENCES

Abstract

The features of the interaction of the eddy-current transducer with the ferromagnetic conducting medium during the flaw detection of ferromagnetic components and pieces of equipment with the revealed influences of external factors such as temperature, electromagnetic interference, etc. are considered. Existing approaches do not provide a clear answer to the question of how to improve not only the accuracy of measurements, but also the ability to determine the nature of the defects of the controlled sample. The research goal is to increase the accuracy of the eddy-current control by compensating of external interferences. The improvement of the construction of the measuring system of the resonance eddy-current flaw detector with a transformer connection with two connected measuring oscillatory circuits and a differential sensor having two measuring coil blocks is proposed. These design changes practically do not affect the ability of the eddy-current flaw detector to detect defects of different types and do not reduce its sensitivity to the anisotropy of the properties of the controlled sample or the gap between the transducer sensor and the controlled product. This takes on special significance for the eddy-current flaw detectors, the basis of which is the resonance method of tracking from the effect of the gap, when the resonance frequency and the quality factor of the measuring oscillatory circuit are monitored. According to the results of the research, the dependence of the eddy-currents flux on the magnetic flux of the primary coil and the properties of the controlled sample was established. It is shown that the transformer transducer is more resistant to external factors, since the measuring coils are back-to-back connected and EMF, caused by external factors, are mutually compensating.

Key words: measuring transducer, U-type magnetic circuit, controlled ferromagnetic sample, external interference