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 4th July 2013, 03:22 PM #1 Vrystaat   diyAudio Member   Join Date: Jan 2012 Location: Bloemfontein Need some help understanding Hallo all, Plse help me understand this. I have a toroidal 500 VA with dual secondary outputs, 0-48, 0-48 VAC. When I connect them to a rectifier bridge, the voltage after the bridge is +- 45VDC on each winding. When I add 10000 uf EL caps after the bridge, I get 66VDC. So 48 x 1.414= 68.8VDC - 0.7Vd due to the bridge which is correct. My question is, why do I only get 67VDC after the caps are added ? I am using a Fluke true RMS meter. __________________ Regards Jan
 4th July 2013, 03:45 PM #2 Kermit100   diyAudio Member   Join Date: Sep 2012 Location: Bendigo what are the tolerances of the capacitors you are using??
 4th July 2013, 03:53 PM #3 Frank Berry   diyAudio Member     Join Date: Sep 2003 Location: Midland, Michigan Two diodes on each side of the bridge for a total of 1.4 volts drop. __________________ Frank
 4th July 2013, 04:03 PM #4 pfigueiredo   diyAudio Member   Join Date: May 2013 Vrystaat, not sure I understood your question: are you asking why don't you get 67VDC without the CAPS ? If that is the case, it is because the average of a full-rectified is 2*Vpeak/pi=2*(48*1.414-2*0.7)/pi = 42V (assuming vdrop in each diode of 0.7V ). When you introduce the CAP you'll get an almost DC output, whose average is near the rectified sinewave's peak value (~66V)
 4th July 2013, 04:30 PM #5 Vrystaat   diyAudio Member   Join Date: Jan 2012 Location: Bloemfontein Thanks to all, the lights suddenly came on !! It makes sense now. __________________ Regards Jan

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