EVCO c-pro mega RACK - Manual (Page 71)

C-PRO MEGA RACK & C-PRO GIGA RACK APPLICATION MANUAL
Page 71
6.3 Compressor regulation
Control of compressor suction pressure envisages the management of the latter in order to reach and
maintain a defined working pressure value: depending on the type of control (side band or neutral
zone) and the use, or otherwise, of inverters for fine adjustment, four types of regulation are
envisaged.
6.3.1 Side band regulation
Side band control exploits the characteristics of PI (proportional and integral) or P (proportional)
regulators to establish when to insert or disengage the compressors used, so as to regularise, within
the differential band, the switching on and off of the various devices. The purpose of PI regulation
is to have no error in full operation.
The parameters defining this regulation are as follows:
⋅
Integral time (IT)
⋅
Proportional band (PB)
⋅
Side band suction SetPoint (SP)
The above figure shows the behaviour of band regulation (SP, SP + PB). Depending on the suction
pressure value, regulation adds or removes the number of steps to request from the compressors.
Under such regulation, the band is displaced above the setpoint.
It is possible to select whether control will refer to PI or just P regulation, by either setting the
parameter for integral action, namely the integration time (TI), or otherwise. In the specific case
where this parameter is set to the value zero, regulation is proportional only, otherwise, it is also
integral. Ti corresponds to the time necessary for integral action, assuming constant error, to
equalise the proportional action: the speed of this action is proportional to the integration time
value. The default parameter is greater than zero, hence, by default, regulation exploits the
proportional-integral characteristic.
SP SP + BP
Steps
Max Steps
Suction pressure