Abstract: An exemplary frequency converter and method are directed to estimating an operation point of a pump when the QH characteristic curve of the pump is known. The frequency converter controls the pump, and a process curve is estimated when a first operation point of the pump is in the nominal range. The process curve defines a head as a function of volumetric flow. A rotational speed of the pump is determined and a QH characteristic curve of the pump is converted to a current rotational speed of the pump based on affinity laws. A second operation point of the pump is estimated by determining an intersection point of the converted QH characteristic curve and the estimated process curve.

Abstract: A method and a system are disclosed in accordance with a pump controlled with a frequency converter. An exemplary method includes controlling the pump with a frequency converter, the frequency converter feeding a motor connected to drive the pump, providing a torque estimate (Test) and/or a rotational speed estimate (nest) of the motor from the frequency converter, forming one or more features (Feature1, Feature2, Feature3, Feature4) indicating cavitation or likelihood of cavitation of the pump and/or reverse flow of the pump using the provided estimates (Test, nest) and detecting cavitation or likelihood of the cavitation of the pump and/or reverse flow of the pump from one or more of the formed features (Feature1, Feature2, Feature3, Feature4).