Detection of Mass Increase in a Fan Impeller With a Frequency Converter

Fan systems are often responsible for the ventilation of contaminated air, such as exhaust gases. Contaminants can build up on the fan impeller eventually causing a mechanical imbalance, which may lead to the fan breakdown and shutdown of production processes. Usually, the contamination buildup can be detected by visual inspection or from increased vibrations caused by the imbalance on the fan impeller. If the contamination buildup could be detected before the imbalance occurs, the unscheduled maintenance or even the failure of the fan system could be avoided. In this paper, a novel method is presented that can be used to detect the contamination buildup on the fan impeller. The method uses the capability of the frequency converter controlling the fan motor to estimate the rotational speed of the motor and the capability to control the motor torque. The presented method is validated by laboratory measurements.