Method for controlling a compressed air installation comprising several compressors, control box applied thereby and compressed air installation applying this method

Method for adjusting a compressed air installation with several compressors, said installation comprising two or more electrically driven compressors of the kind known as any of the designations:

• ‘loaded/unloaded’ compressor;
• turbo compressor;
• and variable rotational speed compressor, said compressors being connected to a single compressed air network via respective outlets thereof, and wherein each compressor is provided with at least one control unit, and further wherein a control box to which is connected a pressure sensor comprising part of said compressed air network is used, the method comprising:
• using said control box to adjust the pressure in said compressed air network relative to a settable target pressure and within a pressure range which is limited by a minimum pressure to be set and a maximum pressure to be set, and wherein the adjustment takes place by controlling the flow of one or more of the two or more compressors in order to increase the overall flow supplied by the compressors when the pressure drops below a first desired level, and in order to lower the overall supplied flow when the pressure exceeds a second desired level;
• and
• storing an evaluation table in a memory of the control box beforehand for every compressor or for every type of compressor of the compressed air installation, such that for every working condition of the respective compressor, the influence of a control order is assessed, and such that for every control order of the compressor concerned, a score is given which is positive when the influence of said order is favourable to the output of the compressed air installation, and which is negative when the influence is unfavourable, and whose absolute value increases as the favourable or unfavourable influence increases.