Siemens SINAMICS S120 Function Manual page 329

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.
Upper characteristic:
H[%]: Delivery height, P[%]: Delivery pressure, Q[%]: Delivery rate, V[%]: Flow rate
Lower characteristic:
P[%]: Power drawn by the conveyor machine, n[%]: Speed of the conveyor machine
Interpolation points p3320 ... p3329 for the system characteristic with n = 100%:
P1 ... P5: Power drawn, n1 ... n5: Speed corresponding to a closed-loop speed control machine
Figure 7-8
Drive functions
Function Manual, (FH1), 04/2014, 6SL3097-4AB00-0BP4
Energy-saving potential
Basic functions
7.17 Energy-saving display
329