Evaluation of motor structural dynamic response by forced vibration analysis

The manufacturer assessment during the design stage inception for potential resonances near any predicted operating force as well as the overall system amplitude response is essential to ensure the proper field operation. Using a model that takes into account the magnetic and mechanical loads it is possible to optimize the design and improve reliability, minimize resonances and reduce vibration amplitudes of the structure, shaft and bearing housing This paper discusses the forced vibration methodology to assess the system amplitude response when subject to forces coming from the motor itself - such as mechanical unbalances and magnetic unbalance pull. A brief design tutorial associated to the analysis is presented, such as the structural stiffness sensitivities, modeling of the fluid film bearing characteristics, mass lumping techniques and damping coefficient that allow the forced vibration analysis. To corroborate with the proposed model two studies case are discussed and used as validation for the proposed model.