CONTROLLER FOR CONTROLLING A FREQUENCY INVERTER AND CONTROL METHOD

摘要

The invention relates to a controller for controlling a frequency inverter (4) of a positive displacement pump motor (3) of a positive displacement pump (2), said controller comprising a control unit (6) which is designed to produce a control variable (Ys) for a frequency inverter (4) of a positive displacement pump motor (3) depending on a reference variable (W) and a first actual operating parameter (X). According to the invention, the control unit (6) is associated with logical means (7) having a first threshold value defining means (12) that are designed to determine at least one first threshold value (YGrenzmax, YGrenzmin) depending on the first actual operating parameter (X) and/or at least one further actual operating parameter (XH, YH, YHH) that could lead to a failure state of the positive displacement pump (2) when exceeded or fallen short of.