The phase shifter I ensures that the current on a line remains lower than a predefined threshold called valueMax. When the current monitored goes above IMax, the phase-shifter will act to modify its tap to bring back the current in an acceptable range.
The time interval before the first time change is specified with a first timer and a second timer indicates the time interval between further changes. The automaton can be locked by an external controller: in this case, it stops acting.
The detailed phase-shifter I behavior is explained in the following state diagram:
.Dynawo.Electrical.Controls.Transformers.PhaseShifterI