Magnetic field monitoring in submersible motor under eccentricity fault considering slotting effect

Large submersible motors make a huge contribution to national security prevention and control of water. But the eccentricity fault has a strong impact on the operational reliability. Therefore, this paper uses new diagnostic signals of air-gap magnetic field to detect eccentricity fault in submersible motor. Compared with the previous papers, this paper combines the effects of eccentricity and slotting. Firstly, a new air-gap permeance model is established considering slotting effect aimed at eccentric motor. Then the time harmonics of air-gap magnetic field are obtained based on MMF and permeance wave approach. Compared with healthy motor, the characteristic frequencies are chosen as diagnostic signals. The air-gap magnetic field is measured by search coil placed around stator tooth. The way is applied to detecting dynamic eccentricity and mixed eccentricity. Finally, for validating the theoretical results, the induced voltages of search coil are gained under different conditions in high voltage submersible motor by finite element method. The simulation is consistent with the theory in the process of data analysis.