On the usability of RC filters for the limitation of distorting regimes induced by controlled rectifiers

The paper deals with the behavior of some RC cells used for the compensation of power distortions. Theoretical aspects related to the behavior of a RC circuit supplied from a non-sinusoidal voltage source are approached. Experimental data concerning the recordings and numerical processings for a three-phase load supplied from a rectifier fully controlled with thyristors are also included. The three-phase load induces a distorting regime in the corresponding supplying network. Therefore tests were made to see if the unpleasant effects can be limited in stable state by means of RC filters. Experiments with the studied load and RC cells added on every phase proved that the distorting effects were not reduced and therefore one can conclude that such filtering cells do not represent a reliable solution. Moreover, an exacerbation of the non-sinusoidal effect was noticed, with negative influences over the supplying network. The authors concluded that, even if the load has an inductive character, a reliable solution for the reduction of the power distorting effects consists in the use of RLC passive filtering cells or of some active (or even hybrid) filters. Considering the load´s specific features related to the absorption of high currents, the use of passive or hybrid filtering cells seems to be the best solution.