A new random PWM (SRP-PWM) technique for decreasing acoustic noise radiated from v/f controlled motor drives

As an effective means to reduce the acoustic noise radiated from v/f controlled inverter fed AC drives, a new three phase PWM (pulse width modulation) technique with separately randomized pulse position (SRP-PWM) is presented and implemented. Each of three phase pulses is located randomly in each switching interval. Along with the randomization of PWM pulses, the space vector modulation is also executed with the SAB C167 microcontroller. The new method is compared with a classic random modulation with a fixed switching frequency modulation. Results of the investigation of an experimental drive system are presented, proving the feasibility of the proposed solution.