A triac along with a variable resistor and a capacitor can be used to construct an adjustable full-wave rectifier. The resistance R of the variable resistor sets the time at which the triac will trigger on. Increasing R causes the triac to trigger at a later time and therefore results in a larger amount of clipping (seegraph).
The size of C also determines the amount of clipping that will take place.(The capacitor acts to store charge until the voltage across its terminals reaches the triac’s triggering voltage.At that time,the capacitor will dump it's charge.)
The reason why the capacitor can introduce additional clipping results from the fact that the capacitor may cause the voltage at the gate to lag the MT2-to MT1 voltage. Overall, more clipping results in less power supplied to the load. Using this circuit over a simple series variable resistor connected to a load saves power. A simple series variable resistor gobbles up energy.This circuit, however, supplies energy-efficient pulses of current.
