A closer approximation can be made
by using the transformer Schade curves. In any case,
ripple voltage increases as the load current increases.
Care must be exercised when selecting
filter capacitors. Power supplies generally use large electrolytic
as filters. It is very important to never exceed the voltage
rating or to reverse the polarity of electrolytic capacitors.
Although the voltage across the capacitor
is relatively constant, the current through it is not. The ripple
currents are typically 2 3 times the DC load current.
The capacitor supplies the load current when the rectifier circuit
current falls. It also accepts the excess rectifier current
when it exceeds the load current demands. The current in the
filter capacitor is therefore an alternating current (AC) since
it reverses direction.