Discussion of "A Variable Switching Frequency PWM Technique for Induction Motor Drive to Spread Acoustic Noise Spectrum With Reduced Current Ripple"

Variable frequency modulations for motor drives that include deterministic, probabilistic (random or randomized), and chaotic pulse width modulation (PWM) are aimed at acoustic noise frequency spectrum spreading [1]-[4]. The discussed paper [1] suggests a deterministic variable frequency PWM method for induction motor drives that is about a deterministic variation of a switching period (subcycle) of a conventional PWM.