Quote:
Originally Posted by kalee20
OK - In the absence of anything better, it would be difficult to disagree with those figures - on the contrary, you could hardly do any better!
The ripple is a bit big. Upping the capacitance will reduce it, and hopefully demonstrate that the secondary current hardly changes.
The 65.5VA... is this calculated from the RMS value of the peaky current waveform and the nominal 15V secondary voltage? If so, it's certainly showing that the transformer throughput is a lot more than the rated 40VA that the OP has at his disposal, with the 3A DC load.
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Apologies for the delay in replying, been doing the hospital run most of the day, then cook tea etc.
The 65.5 VA I calculated was calculated from the PSUD2 results using the transformers RMS secondary voltage under load and the transformers RMS secondary current which is the diode(s) RMS current multiplied by the square root of two.
I also calculated the VA using Schades (just for the heck of it) for the transformers secondary current and using the results of PSUD2 for the unloaded and loaded secondary voltages and DC output voltage, I calculated the figure to be approx. 63 VA so not far out when compared to PSUD2.
The product of 2Pi*f*C*RL is quite low but the series resistance/load resistance percentage is quite high which means that the Shades curve is reasonably flat at those values.
Lawrence.