| 摘要 |
In order to feed a three-phase asynchronous motor (2) it is used a square- wave voltage (A,B,C), whose harmonic content is modified so as to reduce the negative effects of the harmonics of lower order at the low speeds.This is obtained by pulse modulation (MI0,MF0) of the initial part and the final part of every half period of the square wave. The central part of the square wave, together with the modulation pulses, is in its turn submitted to chopper action (CHOP) so as to fix the effective value of the supply voltage to a level corresponding to the prefixed frequency for said square wave. <IMAGE> |
