Sungur, CemilCalisir, SedatKaya, Ender2020-03-262020-03-2620160733-94371943-4774https://dx.doi.org/10.1061/(ASCE)IR.1943-4774.0001046https://hdl.handle.net/20.500.12395/33438In the present study, the changes in system efficiency were investigated at constant pressure and at different flow rates between 100 and 50% of the nominal flow rate in an irrigation pumping plant. For this purpose, programable logic controller (PLC) and human machine interface (HMI) panel software was developed to automatically control motor speed by means of frequency, and valve opening by means of servomotor in an irrigation pumping system. In this automation system, pump flow rate was measured using an electromagnetic flowmeter and pump discharge pressure was measured using a pressure sensor. According to the results of the study, optimum system efficiency was observed at the point corresponding to 70% of the nominal flow rate. This system efficiency value was found to be 6.9% higher than the nominal system efficiency. However, the system efficiency at points corresponding to 50% or lower ratios of the nominal flow rate was found to be lower than the nominal system efficiency. (C) 2016 American Society of Civil Engineers.en10.1061/(ASCE)IR.1943-4774.0001046info:eu-repo/semantics/closedAccessVariable frequency drivesPump performanceSystem efficiencyProgramable logic controller (PLC) softwareArticle14211Q2WOS:000386357700002Q2