| Abstract |
Thyristor rectifiers, working with natural commutation, present two drawbacks : they create harmonic currents, they absorb reactive power. In order to reduce these drawbacks, we have studied and tested a rectifier including a current commutating diode bridge directly connected to a series chopper. The chopper control allows each A.C. current half cycle to be in phase with the corresponding one of the feeding voltage, so that no reactive power is then absorbed. Using suitable current pulses in each half cycle, the lower order harmonics can be cancelled. The P.W.M. is interesting only when it is associated with the filtering of the input current and of the output voltage. It allows an interesting reduction of the weight of the input filter. The output filter must eliminate the order of harmonic corresponding to the rectifier pulse number. Theoretical and experimental results show the quality of the obtained characteristics and the particular care which must be taken in determining the filter elements. |
