a yield increase during the previous variation phase is now chosen as the initial direction for variation variation of the operational setting begins at time t 1 reaches its maximum at time t 2 and returns to its initial value at time t 3 due to the fact that no increase in power yield occurred in the assumed example the variation is now carried out inversely i e in the opposite direction a maximum power yield is reached at time t 4 and after a brief overshoot this maximum is maintained at time t 5 following a predefined interval the operational setting is varied once again u2014 u201c by rotation u201d so to speak u2014 and the initial direction is the same as the direction that led during the previous variation phase to an increase in power yield which was the negative half wave at time t 6 a maximum yield is once again reached and so this setting is maintained hence the loss of yield that would have occurred with the positive half wave has been fully eliminated after yet another time interval variation of the operational setting commences once again at time t 7 this time variation begins with the negative half wave because this led to an increase in power yield during the previous variation phase in is assumed in this case that the latter does not re occur so the.