Carrier Frequency Modulation PWM Method and its Evaluation of Low Magnetic Noise Effect

Abstract

To solve the acoustic magentic noise problem, the carrier frequency sinusoidal modulation PWM method has been proposed. But, there are some unresolved problems, such as how to determine the amplitude and frequency of the sinusoidal function which is used to modulate the carrier frequency, and within a certain carrier frequency range, how to select the PWM method to get the lowest acoustic magnetic noise.
In this paper, first, the harmonics analysis for the carrier frequency sinusoidal modulation PWM is presented. Next, the relation among the harmonics spread effect, the amplitude and frequency of the sinusoidal function is discussed. The optimum values (amplitude and frequency) are determined based on the calculation of the author defined HSF (harmonics spread factor). And then, based on the author proposed induction motor acoustic magnetic noise vs. harmonic current characteristic function (NHCC function), the applicable carrier frequency ranges of the two kinds of low acoustic magnetic noise PWM methods are clarified. Finally, the experimental results are shown to verify the effectiveness of the proposed PWM method for reducing the peak values of harmonics. The low acoustic magnetic noise effect obtained by the proposed PWM method is also evaluated by the actual measurement and psychological test.