Ripple, average voltage

Where n is the ripple number, in the above case n = 3 and Vdo is the average ripple voltage at no-load. 

The six-pulse rectifier bridges can be connected in such a manner as to produce a 12-pulse DC output voltage. The average value of DC ripple voltage is thereby reduced. From the AC power system point of view the magnitude of the harmonic components is reduced and some harmonics are eliminated. Figure 15.6 shows a typical circuit of a 12-pulse bridge. 

Because of the phase shifting and consequent overlap of the three waves, the six-pulse output is much smoother than the output of a single-phase system. In the latter, the maximum amplitude of the voltage, and hence also the current if the load is purely resistive, is 57% greater than the average. With six pulses, this difference, or current ripple, is reduced to about 4.7%. It will be obvious that further increase in the number of pulses will further reduce the current ripple. 

C1 is chosen to provide a maximum ripple voltage at the output node at the maximum load current. This ripple voltage is calculated from the average current per cycle that enters and leaves the capacitor. From... 

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