1592001830 XC645D GB r3.4 04.09.2017.docx XC645D 32/50
18.1.5 Limitation of digital compressor capacity by parameters PM and
PMA
The capacity of the DGS compressor can be limited by the PM and PMA parameters, as shown
in the following diagram.
The capacity of the DGS compressor is limited by the PM and PMA parameters, where
PM: in percentage, it sets the minimum capacity of the DGS activation during a period tdS. For
instance with tdS = 20s and PM = 20, the minimum activation of the DGS is 4s.
NOTE
For digital scroll (dGty = SCrL) the minimum allowed value of PM is 10
For digital stream (dGty = StrM) the minimum allowed value of PM is 0
NOTE: for a proper functioning of the DGS, it’s recommend a minimum activation time of 2s.
PMA: it limits the percentage of the DGS activation during a tdS period according to the
formula: ((Pbd * PMA) / 100) * tdS.
18.2 Proportional Band regulation - only for fans
The fan regulation band Pb is divided by the number of fans:
The numbers of fans switched ON is proportional to the value of the input signal: when this
distances itself from the target set point and enters the various bands, the compressors are
switched ON, to be then turned OFF when the signal brings near the set point.
In this way if the pressure is greater than regulation band, all the fans are on, if the pressure
(temperature) is lower than the regulation band all the fans are off.
Naturally also for this regulations all the delays (Fon and FoF) are valid.
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