Diagnosis of damages of wings of rotor by electromagnetic field measurement

Abstract

This paper proposes the method to detect and diagnose the defects of the rotating wings of turbines, pumps and motors by the measuring the change of the eddy currents comparing with those of no defects. The eddy current is induced in the conductor wings rotating in the static magnetic field and the magnetic field by the eddy current is measured by a pick-up coil. The magnetic field are obviously different between the wings with/without the defects. This method has the possibility of contribution to the earlier findings of the defects of the abnormality of the turbines, pumps and motors. Moreover, the time-series of the horizontal displacement of the rotating axis was measured by the laser displacement meter. To the axis, the external magnetic force was applied by a ring magnet to make the unstable state. The SSA (Singular Spectrum Analysis) [2] was applied to analyze the time-series of the displacement in the unstable state and it was shown that some of the SSA components are sensitive enough for the earlier detection of the transition to the unstable state.