Energy-Saving Display - Siemens SINAMICS S120 Function Manual

6.17

Energy-saving display

Through the tailored, speed-controlled operation, a drive can consume significantly less
energy than with a conventional closed-loop process control. This is especially true for
continuous-flow machines with parabolic load characteristics, such as centrifugal pumps and
fans. Using the SINAMICS S120 system enables control of the flow rate or the pressure by
changing the speed of the continuous-flow machine. As a consequence, the plant or system
is controlled close to its maximum efficiency over the complete operating range.
Energy savings display
The energy saved is displayed in r0041.
Machines with a lower energy-saving potential
When compared to continuous-flow machines with parabolic load characteristic, machines
with a linear or constant load characteristic, such as conveyor drives or reciprocating pumps,
have a lower energy-saving potential.
This function is optimized for fluid-flow machines.
Situation
In a conventionally controlled plant or system, the flow rate of the medium is controlled using
valves or throttles. In this case, the drive motor operates at a constant rated speed defined
by the particular operation. The system efficiency decreases significantly if the flow rate is
reduced by means of valves or throttles. The pressure in the system increases. The motor
also consumes energy when the valves/throttles are completely closed, i.e. with a flow rate
of Q = 0. In addition, undesirable process-related situations can occur; for example,
cavitation in the continuous-flow machine or increased heating of the continuous-flow
machine and the medium.
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.
Drive functions
Function Manual, (FH1), 01/2013, 6SL3097-4AB00-0BP3
Basic functions
6.17 Energy-saving display
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