It is mainly caused by the radial component of the air gap magnetic field acting on the stator core. It propagates outward through the yoke, causing the stator core to vibrate and deform.
The second is the tangential component of the air gap magnetic field, which is opposite to the electromagnetic torque and causes the core teeth to deform and vibrate locally. When the radial electromagnetic force wave is close to the natural frequency of the stator, it will cause resonance, greatly increase the vibration and noise, and even endanger the safety of the motor.
