Sound quality improvement technique for inverter-driven motors

Motor-driven products are becoming increasingly popular along with the trend toward carbon neutrality. Motor units driven by PMW inverters are one of the key components of motor-driven products, but since they are also one of the dominant sound sources, there are high demands for quietness, including sound quality improvement, in terms of comfort. During the DC-AC conversion process, the PWM inverter generates harmonic current distortions and, moreover, the electromagnetic excitation forces generated in the air gap between the rotor and stator induce harmonic vibrations in the motor. Therefore, this presentation describes the mechanism of motor noise generation from the excitation source to propagation and radiation, and activities to improve sound quality for the motor unit driven by inverters.