Superimposed Dc:

At times a wave can have components of both ac and dc. The easiest illustration of an ac/dc combination is demonstrated by the connection of a dc source, like a battery, in series with an ac source, like the utility main.

Any ac wave can have a dc component along with it. When the dc component surpasses the peak value of the ac wave, then fluctuating or pulsating dc will outcome. This would take place, for illustration, when a 200-V dc source was connected in series with the utility output. Pulsating dc would emerge, with an average value of 200 V though with instantaneous values much higher and lower. The wave shape in this situation is demonstrated in figure shown below.

Figure: Composite ac/dc wave resulting from 117-V rms ac in series with 200-V dc.