Patent ID: 7400518

Claim:
A method for reducing common mode noise in a three phase pulse width modulated (PWM) system that includes a three phase waveform generator that generates first, second and third initial modulating waveforms, a carrier signal generator that generates a carrier signal and a PWM generator that compares modulating waveforms and the carrier signal to generate duty cycle signals which are in turn used to generate switch control signals for controlling at least one of converter and inverter switches, the method comprising the steps of: receiving the first, second and third initial modulating waveforms; identifying a first of the modulating waveforms that is instantaneously the maximum of the modulating waveforms; identifying a second of the modulating waveforms that is instantaneously the minimum of the modulating waveforms; for a first phase associated with at least one of the first and second identified waveforms, substituting a first substitute waveform for the one of the first and second waveforms; for the first phase, modifying at least one of the first substituted waveform and duty cycle signals generated by comparing the first substituted waveform with the carrier signal as a function of a first rule set to substantially minimize the effects of turn on delays; and for at least one of the second and third phases, modifying at least one of the associated modulating waveform and duty cycle signals generated by comparing the modulating waveform with the carrier signal as a function of a second rule set to substantially eliminate the effects of turn on delays where the second rule set is different than the first rule set.