Optimizing performance of variable-speed fans

Three design iterations were performed on a 41-cm diameter, direct-drive, agricultural ventilation fan to optimize its performance for fixed- and variable-speed operation. Computer simulations and laboratory tests aided the design of a new fan motor and the selection of a different impeller. The importance of motor/impeller matching, motor capacitor size, and other factors on fan ventilating efficiency ratio and controllability, and motor power factor and current balance was demonstrated.