This paper presents a method for large-scale structural-acoustic analysis in which a cavity is divided into several acoustic fields, and a transfer-function method is used to solve the acoustics efficiently. By solving simultaneous equations using the Gaussian elimination method sequentially for each pair of neighboring acoustic sub-fields, the calculation time and memory requirements are reduced. Calculation accuracy is the same as when calculating the entire acoustic field without first dividing it. We created two kinds of closed acoustic models (cavity models) and carried out numerical simulations. The results showed that the proposed method is effective for large-scale structural-acoustic analysis.
Vibration and noise need to be calculated with a high degree of accuracy to estimate the radiated noise and vibration induced by the electromagnetic force from a motor. In the case of inverter motors, changes in rotation speed and load lead to changes in exciting frequencies and amplitudes of electromagnetic force harmonics. We developed a way to analyze frequency responses of electromagnetically induced vibration using the electromagnetic force in a representative revolution speed in the above conditions. We measured and calculated a sample motor's vibration induced by electromagnetic force of time order harmonics, which has a dominant effect on the overall vibration, and we compared levels of vibration velocity. We calculated both rotation speeds and vibration velocity levels, which had three observable peaks with a high degree of accuracy.
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