Calculating The Energy Saving For Fluid Flow Machines - Siemens SINAMICS G120 Operating Instructions Manual

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6.7.2

Calculating the energy saving for fluid flow machines

Background
Fluid flow machines, which mechnically control the flow rate using valves or throttle flaps,
operate with a constant speed corresponding to the line frequency. The lower the flow rate,
the poorer the system efficiency. The machine has the poorest efficiency when the valve or
throttle flaps are completely closed. Further, undesirable effects can occur, for example the
formation of vapor bubbles in liquids (cavitation) or the temperature of the medium being
pumped can increase.
The converter controls the flow rate by appropriately varying the speed of the fluid flow
machine. As a consequence, the fluid flow machine has the optimum efficiency for each flow
rate, and draws less electric power in the partial load range than for closed-loop control
concepts based on valves and throttle flaps.
Function
Converter with the CU240B-2 and CU240E-2 Control Units
Operating Instructions, 01/2016, FW V4.7 SP6, A5E34259001B AC
Advanced commissioning
6.7 Application-specific functions
The converter calculates the energy
saving from the flow characteristic
associated with a mechanical flow
control and the measured electric
power that is drawn.
The calculation is suitable for centrif-
ugal pumps, fans, radial and axial
compressors, for instance.
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