Open Delta Voltage Regulator

Thread Starter


Joined Jan 4, 2009
Can someone explain how the third phase in an open delta voltage regulator scheme is also regulated?

I don't understand how regulating the the red and blue phase using two 'cans' results in the third phase also being regulated?



Joined Nov 27, 2006
Remember: "phase" means a coil or capacitor between two lines or between a line and a neutral. As long as all three "LINES" are connected, the phase between line 2 and line 1 is "seen" by the two lines. Similarly, the next phase is between line 1 and line 3. Lastly, the "open" phase lies between line 3 and line 2 and although there is no single coil or capacitor between them, they still "see" a phase because between line 3 and line 2 there are two coils, but they are not in phase with each other, so yellow "sees" a resultant "phase". I hope you can follow what i am trying to say. See the attached sketch, which is an example only of an anti-clock rotation of phases.IMG-20151027-00187.jpg