describing the voltage out of a rectifier

Windadct

I would say that ideally pure DC V avg = V rms - and the Ripple is an undesirable component. The DC Bus is defined by Vdc + Ripple, calculating the true average or the true RMS of the bus with significant ripple is not trivial. You then filter to reduce the ripple as much as $ and the spec allows. As for the Current waveform, it can get ugly, particularly for the line.
BTW - to calculate the losses in the rectifier - you need to know both RMS and Average of the current because there are resistive losses depending on RMS and Vf x I losses of the diode depending on the average. Then to calculate the current in the DC Bus caps - practically takes an frequency domain ( fft ) calculation.

sophiecentaur

But the ripple may not matter at all, in some cases.

vk6kro

That's right.

Power supplies are seldom just a transformer, a rectifier and a capacitor these days. Usually they are followed by a voltage regulator and the only concern then is that the input to the regulator is always above the minimum input requirement for the regulator.

Linear regulators will do a very nice job of giving a pure DC output at the regulated voltage as long as the bottom of the ripple waveform does not dip below the minimum input voltage of the regulator.

Switching regulators tend to be lighter and cheaper and more efficient than linear regulators but they often have output which is DC with a lot of noisy AC superimposed on it. Maybe there are good ones out there at a price, but the only ones I have seen were just noise boxes.

Averagesupernova

Switch mode power supplies can be made to produce very clean outputs. However, alot of the things that are simply ignored in linear regulator power supplies become significant in switchers. Switchers generate alot of noise as VK6KRO mentioned. This noise can be managed but if not they will just be noise boxes.