Siemens SINAMICS S150 NEMA, Operating Instructions Manual

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Functions, monitoring and protective functions
9.3 Drive functions
Enclosed Drives
560
Operating Instructions, 12/2018, A5E36652151A
9.3.20 Energy saving indicator for pumps, fans, and compressors
Function of the energy savings indicator
This function determines the amount of energy used by pumps, fans, and compressors and
compares it with the interpolated energy requirement for similar equipment controlled using
conventional throttle controls.
The energy saved is calculated over the last 100 operating hours, and is displayed in kWh.
For an operating time of less than 100 hours, the potential energy-saving is interpolated up
to 100 operating hours.
The flow characteristic with conventional throttle control is specified over 5 adjustable
interpolation points.
Background
In a conventionally controlled pump, fan or compressor, the flow rate of the medium is
controlled using valves or throttles. In so doing, the machine runs constantly at the rated
speed. 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 or 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 fluid flow
machine or increased temperature rise of the fluid flow machine and the medium.
As a result of variable speed operation, a drive operating under partial load conditions
consumes considerably less energy than with conventional process control using valves or
throttles. This applies in particular for pumps, fans, and compressors with parabolic load
characteristics. With SINAMICS, a closed-loop control of the flow rate or pressure is
achieved by employing closed-loop speed control of the pump, fan or compressor. As a
consequence, the plant or system is controlled close to its maximum efficiency over the
complete operating range.
In comparison to pumps, fans, and compressors, machines with linear or constant load
characteristic (e.g. conveyor drives or positive displacement pumps) have lower potential
savings.
Energy saving by using a variable speed drive
When a variable speed drive is used, the flow rate of the pump, fan, or compressor is
controlled as a function of speed. The flow rate changes proportionally with the speed of the
continuous-flow machine. Any existing valve or throttle remains open. Therefore, the
equipment works close to optimum efficiency and consumes considerably less energy,
particularly in the partial load range, than equipment controlled by means of valves or
throttles.