Reduction of the acoustic noise in PMSM drives by the periodic frequency modulation

In the PMSM (Permanent-Magnet Synchronism Motor) driven by fixed switching frequency inverter, the acoustic noise spectrum has highly concentrated harmonic energy near switching frequency and its multiples. In this paper, triangular and sawtooth periodic switching frequency modulation patterns are proposed to transfer these discrete power spectrum to more wider frequency ranges, so as to limit the acoustic noise at low cost. Both simulated and experimental results showed that periodic frequency modulation can reduce the acoustic noise effectively with more continuous spectrum compared with fixed switching frequency.