What is PWM (Pulse-Width Modulation)?

Definition

PWM (Pulse-Width Modulation) is a technique initially developped to control electrical machines at variable speed. It is based on the generation of voltage pulses of variable width: when smoothed by the inductance of the machine, they create quasi-sinusoidal current waveforms of variable frequency in the stator windings.

The most common PWM technique is called Symmetrical Pulse Width Modulation: the switching times generating the voltage waveforms are defined by the intersection of a symmetrical triangular carrier with a purely sinusoidal waveform called modulation signal. The frequency of the carrier f_swi is called carrier frequency, chopping frequency or switching frequency.

Application to e-NVH

The PWM control of the electrical machine creates additional voltage and current harmonics in the windings. These specific harmonics create specific acoustic noise harmonics around mutiples of the switching frequency, these are detailed in the article on PWM force harmonics.

Application to MANATEE

MANATEE software can include the vibroacoustic effect of PWM based on analytical calculation of PWM waveforms, import of voltage/current waveforms or coupling with Simulink model.

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