Unbalance in ac motors with variable speed

Abstract

The study aims to analyze the imbalance in alternating current motors with variable speed, specifically in asynchronous motors, to identify and control resonance and instability phenomena that arise during operation at different speeds. These phenomena can cause excessive vibrations, damage to mechanical components, and reduced motor lifespan. To achieve this, a dynamic analysis of a three-phase rotor was conducted using a mathematical model that considers the stiffness and damping coefficients of the bearings, as well as excitation forces and lubrication conditions. The rotor was divided into three sections, and its behavior under unbalanced conditions was simulated using dynamic analysis software (Rotor Dynamics Analysis). Additionally, practical vibration measurements were taken using a CSI 2130 analyzer to validate the simulation results. The results revealed the presence of two critical speeds, one at 800 rpm and the other at 1600 rpm, where maximum vibration amplitudes and resonance conditions were observed. These critical speeds pose a significant risk to motor operation, as they can lead to instabilities and damage to mechanical components. The study concludes that it is essential to avoid operating the motor at these critical speeds to prevent failures and ensure safe and efficient operation. Furthermore, it highlights the importance of conducting modal analysis and regular preventive maintenance to identify and mitigate potential issues before they become critical. The findings provide valuable insights for optimizing the operation of asynchronous motors in industrial applications, particularly in processes requiring variable speed, thereby contributing to improved energy efficiency and reduced maintenance costs.