Random PWM inverter drive systems: theory and practice

A three-phase PWM inverter system for AC motor control using a random switching strategy (RPWM) to reduce the perceived acoustic noise from the drive is described. It allows the use of low-resolution timers with simple microcontrollers and power switching devices, by incorporating a vector-integral feedback strategy within the actual PWM waveform generator thereby ensuring that errors cannot accumulate. A theoretical analysis of. The RPWM waveforms is shown to be in close agreement with experimental observations so that power spectra can be tailored for specific applications to produce a quiet general purpose drive with essentially no price premium over a conventional one