Efficient, Demand Oriented Compressed Air Production

Under present economic conditions, the need for industry to save energy is becoming increasingly important. Compressed air technology can help by providing significant savings, but in many cases this potential is not being fully exploited. There are many ways to efficiently produce compressed air, one of which is to electronically control the speed of a rotary screw compressor. This is the method Kaeser uses for its highly efficient “Sigma Frequency Control” (SFC) compressor systems. The frequency-converter based controller works as follows: As soon as the preset minimum pressure is reached within the air system, the controller starts the compressor, precisely matching motor and compressor speed to meet compressed air demand. If the system pressure continues to increase despite reduced compressor speed, the system will automatically start to idle and then switch itself off, provided that the minimum preset pressure is not reached.
 
The energy efficiency of a compressor system is determined by the specific power requirement or, to put it another way, the ratio between the air delivery and the amount of (electrical) power required to produce that air. The energy saving effect of speed regulated rotary screw compressors is particularly noticeable when combined with other important system design characteristics, as featured in every Kaeser SFC unit for example: More efficient than small high speed airends, large airends provide excellent performance throughout the entire control range and ensure minimal component wear and maintenance. 

Direct connection of the drive and compression units via a maintenance-free 1:1 coupling means that the airend and motor operate at the same low speed, consequently eliminating the transmission losses associated with gear driven units. One-to-one drive reduces the number of components needed in comparison with gear drive, increasing reliability and service life. 
The free air delivery of SFC units is precisely matched to actual air demand via infinitely adjustable speed regulation within the control range. Furthermore, depending on the buffer capacity of the air distribution network, pressure can be maintained to within + 0.1 bar, consequently enabling the maximum system pressure to be reduced. This can lead to significant savings, as each 1 bar pressure decrease results in a six percent reduction in energy consumption. 
As the motor is soft-started by the SFC unit, the motor switching frequency is theoretically unlimited, but in practice is once per minute or 60 times an hour. The SFC therefore allows the compressor to completely switch off after a minimal idling period once the maximum preset pressure is reached and to start-up again as required. This feature prevents the high starting currents associated with other motor start-up methods and protects system components from potential damage. Dynamic load on moving components is also reduced by infinitely variable braking and acceleration. A generously sized frequency converter and effective control cabinet cooling guarantee trouble-free operation even in high ambient temperatures. The Kaeser range of SFC equipped rotary screw compressors currently comprises 13 models ranging from 18.5 to 250 kW. This wide choice, combined with specially programmed internal and master control systems, enables selection of a perfectly tailored compressed air system that will keep idling to an absolute minimum. With carefully considered planning, energy savings of 30% or more are possible.

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