In this rectifier example the output capacitor and load resistor have been divided into two equal parts and are connected in series. The mid point of the series capacitor connection is connected to an open switch. The other side of this switch is connected to the neutral point of the mains voltage supply. 

By considering the case when the switch is open, then the operation of the rectifier is exactly the same as the previous cases. The current flows through an upper diode and back through a lower diode. The selection of diodes, in which the current flows, depends on the line-to-line voltage. By changing the AC inductor value the amount of distortion in the current waveform is varied. By looking at the voltage across the switch in the bottom graph it can be seen that the voltage is not zero. From the harmonic spectrum this voltage is composed of the triplen harmonics, with the largest value coming from the 3rd harmonic. For low values of supply inductance the harmonic level of u0 are smaller than for larger inductor values. 

Since there is a voltage across the switch, if the switch is closed a current should flow between the capacitor mid-point and the supply neutral. Use the mouse to close the switch. A significant 3rd harmonic current should be flowing between the mid-point and the neutral. The current that flows from the mains also contains a large amount of 3rd harmonic and that the peak current is now much larger than before. This is not desirable for the rectifier therefore do not connect the neutral to the mid-point of the DC output.

• Click on the red switch to connect or disconnect the mid point of the DC output to the neutral of the supply. When the switch is in the open position the harmonic spectrum shows the voltage across the switch. What will this voltage do to the circuit when the switch is closed? The voltage will cause a current to flow in the switch; what level do you expect these currents to be? 
• Adjust the value of the 3 AC inductors by dragging the red bar. What do you expect the increasing of the L value to do to the supply currents?
• By adjusting the time line you can see the path the current flows around in the rectifier.