| Abstract |
Two-phase pulse-width modulation is widely used for the constant V/f type three-phase motor drives. Here, the intervals between 60 to 120 degrees and 240 to 300 degrees, in each phase, are not modulated and the remaining two phases are modulated. In this manner, the switching in one cycle is decreased and a higher maximum voltage is obtained. However, the dominant harmonic components are the sidebands around the carrier frequency which cause current ripple and audible noise. A new PWM method is proposed in this paper. A rectangular wave which has the frequency of three times the fundamental frequency is superimposed to the line voltages. The optimal magnitude of this signal is chosen so that the sideband components around the carrier frequency are minimized. |
