AIR COMPRESSOR CONTROL SYSTEMS

Compressed air system controls match the compressed air supply with system demand and are one of the most important determinants of overall system energy efficiency. The objective of any control strategy is also to shut off unneeded compressors or delay bringing on additional compressors until needed. All units that are operating should be run at full-load, except one unit for trimming.

Over the years, compressor manufacturers have developed a number of different types of control strategies. Controls such as start/stop and load/unload respond to reductions in air demand, increasing compressor discharge pressure by turning the compressor off or unloading it so that it does not deliver air for periods of time. Modulating inlet and multi-step controls allow the compressor to operate at part-load and deliver a reduced amount of air during periods of reduced demand. Variable speed is accepted as an efficient means of rotary compressor capacity control, using integrated variable frequency ac or switched reluctance dc drives. Compressor discharge pressure can be held to within +/- 1 psi over a wide range of capacity, allowing additional system energy savings.