Reduction of audible switching noise in induction motor drives using random position space vector PWM

Random pulse width modulation (RPWM) is a switching technique used to spread voltage and current harmonics over a wide frequency range. By using a randomly changing inverter switching frequency, the power spectrum of the electromagnetic acoustic noise can be spread to the wideband area. Wideband noise is much more comfortable and less annoying than narrowband noise. Thus, RPWM has been attracting interest as an excellent method for the reduction of acoustic noise in inverter drive systems. A new RPPWM (random position space vector PWM) is proposed and implemented. Each of three phase pulses is located randomly in each switching interval. Along with randomisation of the PWM pulses, space vector modulation is also executed in a C167 microcontroller. Simulation and experimental results show that the voltage and current harmonics are spread to the wideband area and that the audible switching noise is reduced by using the proposed RPPWM method.