Question about filter capacitor

[kae]

I am building a DC supply with a toroidal transformer with a 45 volt secondary winding. After being rectified, I anticipate a theoretical 63 volt output (45 x 1.4). Will the filter capacitor (I will be using a 21,000 uF cap) change the rectified output voltage? If so, is it up or down? Is there a theoretical formula for this? Thanks.

[Al_The_Man]

The peak DC voltage after rectification is AC x 1.414, without capacitor, the ripple will be 100% at 120hz for full wave rectification.
The effect of the capacitor is to maintain this peak at the 1.414 level, therefore attempting to maintain minimum ripple.
With no load, the capacitor should maintain the ripple at 0%, at load the percentage of ripple will depend on the degree of load and the size of capacitor.
Al.

[kae]

Thanks for the reply Al.

I take it from your post that there is no measured change of the rectified output voltage on the downstream side of the filter capacitor.

[Al_The_Man]

If you are measuring peak, no, there will be no difference between smoothed and unsmoothed, but with no capacitor, you would measure a mean DC voltage due to the ripple with a normal VOM.
Al.

[kae]

Thanks, Al.