In this applet the role that the non-sinusoidal current drawn by power electronic circuits has on the voltage at the AC side of the rectifier is examined. A bridge rectifier circuit with a capacitor and resistive load on the DC side is used. Compared to the previous bridge rectifier with capacitor circuit, there is now an additional inductor (placed on the AC side of the rectifier). As with the previous circuits, the inductor helps to smooth the current drawn by the rectifier, therefore creating less distortion. Since the inductor is placed between the rectifier and the AC source, the voltage at the input to the rectifier is now not going to be sinusoidal. In fact when the diodes are conducting the voltage at the input of the rectifier is going to be the same as the capacitor voltage, since the diodes can be considered as short-circuits when they are conducting. This effect can be seen in the top graph. 

If the inductor size is increased then the current waveform shape is smoother and has less distortion. However this is not reflected in the true power factor measurement, which in fact decreases. This is because the larger inductor is causing the fundamental current to lag behind the voltage. We now have more reactive current, thus causing a lower true power factor.

• The size of the AC side inductor can be adjusted by the red bar. Notice how the inductor value affects the shape of the current waveform. Why doesn't a better waveform give an improved true power factor?
• The load resistance can be varied by the red bar. Notice how the harmonic composition of the current changes with the load resistance level.