What is PWM (Pulse-Width Modulation)?


PWM (Pulse-Width Modulation) is a technique initially developed 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 fswi 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 multiples of the switching frequency, these are detailed in the article on PWM force harmonics.

Application to Manatee

Manatee software can simulate switching noise, including sound quality metrics.