Statischer Schalter mit drei Schaltzuständen

The three state switch has two thyristors (TR1,TR2) which are placed in parallel across the mains circuit (A1,A2) with a series load. The two thyristors are placed in opposite current flow directions. There is a voltage operated switch (20) which applies positive or negative voltages to the anode of one thyristor and the cathode of the second thyristor. The switch has a third open circuit position. Switching the thyristors allows positive or negative current flow or zero flow through the mains circuit.