Influence of power converter on induction motor acoustic noise: interaction between control strategy and mechanical structure

A general method for reducing noise due to the coupling of an electric machine and a power converter is presented. Ths problem is generally broken down into three parts: machine design, switch control and mechanical structure response. This may involve the use of numerical methods, whch require much computation, and is not well suited to the analysis of the complete drive. The method presented is semianalytical and based on rotating field theory, while the fast Fourier transform permits a global approach to the problem. This method may be used at the design stage of the electric machine (slot number, slot aperture, stator yoke thickness) or for the choice of PWM strategy and parameters for the power converter. The theory is illustrated by experimental results based on a 700 W induction motor associated with a natural sampling power converter. Acoustic measurements, made in a semianechoic room, show that minor modifications of the PWM control strategy greatly improve acoustic performance.