Calibration and Application of a Performance Model of Motor-Driven Fan Systems Powered by Variable Frequency Drives

Abstract

Variable frequency drives (VFDs) are widely applied to motor-driven fan systems for energy savings and result in more complicated system performance models. A performance model of VFD-motor-fan systems is essential to detect operation faults and optimize control strategies. The purpose of this paper is to calibrate a performance model of VFD-motor-fan systems using experimental data and demonstrate its applications in belt fault detection and virtual airflow meters for optimal control. Firstly, a calibration approach is developed using conventionally available fan speed, head, and system power input as well as temporally measured airflow rate. Then the performance model, which is defined by fan head-airflow rate, fan shaft power-airflow rate, and drive efficiency-fan speed curves, is calibrated for a fan with a design airflow rate of 1,200L/s using the developed calibration approach. Finally, the calibrated model is applied to detect the slipped belt faults and calculate the fan airflow rate with the measurements of fan speed, head, and system power input. The experiment results reveal that the developed approach can readily obtain the performance model of VFD-motor-fan systems and be applied to effectively detect slipped belt faults and accurately calculate the fan airflow rate with the root mean squared error of 42L/s.

Keywords: Fans, Motors, Variable frequency drives, Models, Fault detection, Virtual flow meters