The electromagnetic force in a motor vibrates as an electromagnetic excitation force which creates noise. The vibration and noise are generated when the electromagnetic excitation force resonates with the motor’s eigenmodes. In order to evaluate this phenomenon more accurately, it is necessary to understand the distribution of electromagnetic force that moves the stator core which is the basis for the radiated sound. The distribution of electromagnetic force or the eigen modes in a model that depends on the geometry of a stator core is required for running an analysis such as for the finite element analysis.
This Application Note shows an example of an evaluation of a reactor’s sound pressure, when acquiring electromagnetic force generated by a stator core for a SPM motor and linking the eigen modes of a motor.
Fig. 1 shows the distribution of the electromagnetic force distribution. A strong output of electromagnetic force can be seen at the tips of the teeth. From these results, it can be expected that the stator core is generating a strong force in a radial direction.
The results of a resolution in a frequency component for an electromagnetic force in a radial direction on the tips of the teeth is shown in fig. 2. From these results, the frequency component in 400 Hz is the most common. From these results, the frequency component in 600 Hz is the most common and the frequency component in 5000 Hz is very small.