El 24/08/17 a les 11:33, Edward Bartolo ha escrit: > Quote by Karl Hammar: "There are several drawback useing the old > transformer + rectifier design. Of main consern is the current spikes > seen on the power grid when the diodes starts to conduct. Your power > supplier don't like them and that is why we have PFC to make the unit > behave more like a resistor to the power grid." > > If PFC stands for Power Factor Correction, using a switching power > supply doesn't free one from using rectification of the mains to power > the switching transistors. The rectifier diodes will also have current > spikes and we are essentially back to square one. With 3 phase power > rectification the current spikes can be greatly reduced as the > rectified voltage output from the rectifier without a smoothing > capacitor never goes below ~85% of peak. > > If voltage rectification was such a problem, all devices/appliances > that have to use a DC voltage source would be at blame, which is > clearly not the case. Power Factor Correction enters the equation when > loads having a substantial inductive component exist. This is the case > when certain types of motors are used. Three phase motors do not > produce a significant inductive load if they are well designed. This > is also true of transformers given their primaries are well designed > to keep the magnetising currents at a minimum. > > For voltage rectification Power Factor Correction (PFC) is not an > issue. If this is a new issue that older text books about > electricity/electronics did not discuss, please direct me to your > sources of information. > _______________________________________________ > Dng mailing list > Dng@lists.dyne.org > https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng >
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