Small induction motor noise calculation

There has been an increasing demand for a quiet induction motor. Electromagnetic noise is jarring to the ear. Most offensive electromagnetic noise is generated when the natural frequencies of the stator coincide with or are close to the frequencies of the magnetomotive forces. In this paper, electromagnetic noise is calculated by boundary element method (BEM) program using the electromagnetic forces of Maxwell stress. The natural frequency and behavior of the stator are calculated by mechanical finite element method (FEM), considering the contact between stator core and frame. Spring elements are introduced between the stator frame and the stacked core. Vibration is calculated by mechanical FEM. Calculated and experimental noise level were within 3 dB(A) at 1200 and 4080 Hz.