Influence of harmonic on rotor dynamic performance of large submersible motors in state of sub-critical speed

In rotor-bearing system of large submersible motor, many factors contribute to the generation of harmonics. This paper theoretically analyzes some factors and makes certain hypothesis. Rotor dynamics calculation model of large horizontal submersible motors is built. The phenomenon of harmonic resonance around the sub-critical speed is verified using finite element method, and the stress and displacement of bearing and rotor iron core are obtained. Finally, the resonance phenomenon which occurs at rated speed, due to the influence of harmonic and the change of sub-critical speed, can result in motor fault. The investigation in this paper supports references in the fault diagnosis and bearing selection in large horizontal submersible motors.