The purpose of this controllable transformer is to compensate for the fluctuations in voltage output from power transformers which arise from changes in load. It achieves this by modifying the transformation ratio on the side where the voltage is in excess. The component can be used as a step-up or step-down transformer. Control is handled via the inputs for increasing or decrease the voltage, e.g. with the help of the power quality meter (CO5127-1S).