Research On Rotor Sub-critical Vibration In Large Submersible Motors

With the development of heavy industries and the progress of urban planning, large submersible pumps become more important. At the same time, the influence of motors linked pumps on national economy is more and more prominent. In order to increase the reliability of large rotating machinery operation and reduce the damage of motors vibration, the problem of vibration and noise for motor rotors is highly valued by scholars of this field. As the key research field in the large rotating machinery, the motor rotor vibration problem also has always been one of the issues investigated by experts and scholars at home and abroad. This paper investigated the rotor vibration in large submersible motors, and put forward motor rotor sub-critical speed vibration. Then the conditions and effect parameters ere analyzed in detail. Finally, the motor rotor sub-critical speed vibration under the eccentricity was given. The achievements of this paper mainly include the following:1. By investigating the application characteristics of large submersible motors, the problem, which is how to apply the rotor dynamics into large motors at low speed, was analyzed. In addition, considering the special working environment of motors, the influence of diving depth on motor rotor subcritical speed is studied as well.2. Using the finite element method, the electromagnetic stiffness, which is an important factor in magnetism and solid coupling system, was calculated and the features of rotor sub-critical speed was analyzed. At the same time, a comparison with the condition of healthy motor is made.3. The sub-critical characteristics of nonaxisymmetric stiffness rotor was analyzed using the analytic method. Then combining with the geometrical symmetry principle, a keyway distribution method, which can improve the nonaxisymmetric stiffness, was put forward as well as its implementation is proposed.This paper systematically studied the issue of rotor sub-critical speed in rotating electrical machines. Some essential features of rotor sub-critical speed and improving methods were obtained. The work established the theoretical foundation and provided some relevant reference value for the further research of rotor dynamics and a series of motor rotor sub-critical speed research.