Siemens SINAMICS S120 Function Manual page 367

Solution to optimize the system
When using a speed controller, the process-specific flow rate of the continuous-flow machine
is controlled by varying the speed. The flow rate changes proportionally with the speed of the
continuous-flow machine. Any throttles or valves remain completely open. The entire
plant/system characteristic is shifted by the speed controller to achieve the required flow
rate. As a consequence, the complete system operates close to the optimum efficiency - and
especially in the partial load range, uses significantly less energy than when using a throttle
or valve to control the flow rate.
Figure 7-8
Drive functions
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
Energy-saving potential
Basic functions
7.18 Energy-saving display
367