The correct method of calculating energy savings to justifyadjustable frequency drives on pumps

摘要

It is easy to make a bad business decision when using electricalnenergy savings as a justification to install adjustable frequency drivesn(AFDs) on pumps. The simple hydraulic formulae andn“rules-of-thumb” are easily misapplied and the errors willngenerally always economically favor the AFD installation. To use energynsavings as a justification for an AFD installation, it is necessary tonaccurately determine these savings over the life of the equipment. Thesensavings are not dependent upon the AFD or motor characteristics butndepend upon the characteristics of the process system. This paper isntutorial in nature and shows why AFDs save electricity, gives examplesnof the common errors that are made in performing the savingsncalculations, shows how to do these calculations correctly, shows how tonmathematically model the process to assist in performing the analysisnand shows how to perform the economic calculations to arrive at anrate-of-return on the AFD investment