A novel prediction method of acoustic magnetic noise based on induction motor's NHCC function

When an induction motor is driven by a pulsewidth modulation (PWM) inverter, acoustic magnetic noise caused by harmonics of the induction motor input is a serious environmental problem. In this paper, a novel prediction method of acoustic magnetic noise is proposed. Acoustic magnetic noise emitted from an induction motor is considered as the function of harmonic components of induction motor current. The acoustic magnetic noise versus harmonic current characteristic (NHCC) function is defined. This NHCC function describes the response of acoustic magnetic noise to a single-frequency harmonic current. Based on the NHCC function, acoustic magnetic noise can be predicted very easily and accurately, simply by the calculation of harmonic components of the induction motor current. By making use of this method, the difficulties of the conventional prediction method, such as the complex calculations of magnetic force, mechanical resonant frequencies, and sound radiation efficiency can be avoided. This novel method can be used as a tool for environmental noise management and evaluation of low-acoustic magnetic noise characteristics of different inverter PWM control methods.