Sensorless pump operation estimation

Pumps are widely used in industrial applications, and they account for nearly a quarter of the electric energy consumption in the European industry. Pumps are often overdimensioned or they may be driven inefficiently, which causes unnecessary energy costs. If the pump drive is not equipped with appropriate measurements, inefficient pump operation may remain undetected for years and lead to a premature pump failure that also has an increasing effect on the pump drive´s life cycle costs. Hence, pump operation monitoring may give a possibility for notable cost savings even if the pump is driven with a frequency converter. Since modern frequency converters provide estimates on the motor operation, they are a natural choice to monitor also the pump operation. In this paper, model-based estimation methods for the pump operating point are presented. Estimation methods are based on the internal measurements of the frequency converter, and therefore, external measurements are not necessary. Hence, the methods are a simple and cost-effective alternative to analyze pump operation: they can be applied in the control, optimization, and auditing purposes of a variable-speed-driven pump. Theoretical background is given for the methods, and they are evaluated with laboratory tests. According to the test measurements, estimation methods are applicable in auditing purposes.