Magnetic vibration of three-phase induction motors supplied by inverters

Electromagnetically produced stress of induction motors under steady state operation, has been minimized using well established design techniques. However, due to the nonsinusoidal voltages supplied by static inverters, the mechanical vibration level is increased and the possibility of failure should be carefully considered. To analyze these problems, the measured three phase current waveform is used for calculating the forces causing the main dynamic disturbances. Airgap eccentricity and saturation levels are both included in a computer based diagnostic analysis system. The vibration spectrum is obtained and related with the harmonic currents; also, a classification of electromagnetic forces using the stress space distribution is carried out. The study reports that the harmonic current from static inverters can produce high stator frame vibration and the degree of severity of this phenomena is related with motor airgap eccentricity, the saturation level and the electrical rotor unbalance