Numerical simulation of electromagnetic vibration of small induction motors

Motors with low noise characteristics are increasingly in demand due to env ironmental considerations. The primary source of noise of these motors, in particular of the most widely produced 4- and 6-pole induction motors, is e lectromagnetic vibration. To gain a better understanding of this specific k ind of vibration, the relationship between magnetic flux and mode of vibrat ion is examined from a study of electromagnetic forces and the motor's mech anical response. The flux distribution of the motor is calculated by a fini te element method (FEM), and from the results of this study, flux density o ver the motor's radial direction is analysed in the space and time domains. Similarly, the electromagnetic force waves are calculated by the Maxwell s tress method and FEM analysis in the space and time domains. Using Fourier analysis, harmonics of these forces are obtained, and are subsequently used as applied forces in the study of mechanical vibration. The vibration beha viour of the motor caused by electromagnetic forces is simulated using FEM for structure analysis. The modes and amplitudes of vibration provided by t hese calculations are then compared with experimental results and the stron g influence of the frequencies close to natural frequency on the modes of v ibration is confirmed.