PREDICTING VARIABLE-SPEED FAN PERFORMANCE FROM MOTOR AND IMPELLER CHARACTERISTICS .1. USING COMPLETE MOTOR DATA

Procedures were developed to economically and reliably select and matc h motors and impellers for agricultural ventilation fans and to predic t variable-speed performance based on complete motor performance data and single-point impeller tests. Complete motor performance was obtain ed from dynamometer tests and included electric power, torque, efficie ncy, and current at speeds ranging from zero-load to locked-rotor at e ach of five control voltages. Performance parameters included ventilat ing efficiency ratio, current balance ratio, motor efficiency, speed, and free delivery airflow rare. A computer model was developed to perf orm the calculations and to rank potential combinations of motors and impellers. The predicted performance of four fan systems agreed well w ith laboratory tests. The model can be used to evaluate effects of var ious design parameters such as motor size, capacitor size, impeller hu b diameter, blade pitch angle, and number of blades on variable-speed performance.