Caracterização das vibrações mecânicas em sistemas com motores de indução acionados por inversores

Abstract

The most recent electrical driver systems are based on electrical induction motors I driven by an inverter. Induction motors with speed control through inverters appeared as an alternative to continuous current motors, since the latter are heavier and demand more expensive maintenance costs. Despite these advantages, the inverters supply the motor with a non-sinusoidal waveform, which induces pulsations in the electrical torque. Such pulsation can excite torsional or bending vibrations in the rotor shaft, reducing the drive quality, besides producing fatigue in it’s mechanical components. The purpose of this work is to analyze the dynamical behavior of a vibratory system by computational and experimental models, composed by an inverter that feeds an inductiorr motor, which is elastically coupled to a mechanical load. The experimental dynamic characteristics of the system under torsional and bending vibrations are determined by the analysis of system frequency response functions. In the laboratory tests, the rotation speed, current and electrical torque of the motor are monitored. The signals are acquired by an analog-digital interface. The data are analyzed in a microcomputer by dedicated software. The evaluations are made on steady state and during transients caused by an abrupt variation of the load.