Performance of Electric Irrigation Pumping Plants Using Variable Frequency Drives

The constant revolutions per minute (RPM) of electric motors prevents adjusting the pump performance to match variable operating conditions, and thus the pump output is usually reduced or throttled with a valve in the discharge pipe. Variable frequency drives for electric motors have the potential to adjust the pump performance to match operating conditions by reducing motor and pump RPM. Field tests at five sites showed that the pump performance at the reduced RPM could reasonably match the throttled conditions at a reduced horsepower demand. However, pumping plants using a variable frequency drive should be operated at least 500–1,000 h per year to recoup costs.