Impact of equivalent concentrated force and moment on electromagnetic vibration analysis accuracy in electrical machines

Abstract

Equivalent concentrated (EC) excitations, comprising EC forces and moments, are widely used to simplify the spatial distribution of electromagnetic (EM) forces in the vibration analysis of electrical machines. Although EC forces and moments have inspired the well-known force modulation effect theory, the underlying impact on the accuracy of EM vibration remains unexplored. This article proposes a harmonic-based force model to characterize the retransformation from EC forces and moments to the new distributed forces—the actual forces participating in the modal superposition of vibration analysis. Using the original forces as the baseline model, a force distribution factor is further refined to provide a discrimination criterion for estimating the accuracy of EC forces and moments. The effectiveness of the proposed model is verified on 12-slot/10-pole and 12-slot/8-pole machines. Acceleration tests are conducted to validate the accuracy of the baseline model, with the maximum errors of only 3.3 dB and 1.8 dB for the two studied machines.