Variable-frequency drives for electric irrigation pumping plants save energy

The constant rpm (revolutions per minute) of electric motors prevents adjusting pump performance to match variable operating conditions, and therefore the pump output is usually reduced or throttled. Variable-frequency drives of electric motors have the potential to adjust pump performance to match operating conditions by reducing motor and pump rpm. Field tests at five sites showed that pump performance at the reduced rpm could reasonably match that under the throttled conditions, but at a much lower horsepower demand. However, for economic reasons, pumping plants using a variable-frequency drive should be operated at least 1,000 hours per year.