GEA Omni, Инструкция по эксплуатации

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•
Illegally Started
This state will occur if the compressor interlock is energized or motor current is received while the compres-
sor should be stopped.
• Shutdown
This state will occur if a shutdown annunciation associated with the compressor in question is triggered. For
more information of specific shutdown annunciations, refer to Section 4.1.1, Page 207.
• Warning
This state will occur if a warning annunciation associated with the compressor in question is triggered. For
more information of specific warning annunciations, refer to Section 4.2, Page 214.
3.11 Screw Compressor Capacity Control
Movement of the compressor slide valve and the resulting change in capacity is done via a time-proportioning
scheme.
The
Control Signal Parameter determines which variable the compressor uses to control capacity. The capacity
control parameters also allow the operator to select between multiple set points and set values for the associ-
ated dead bands, and proportional bands.
The capacity control algorithms determine the proper load or unload pulse width. The sum of the dead band and
proportional band defines a range above and below the set point outside of which load and unload pulses will be
continuous. If the control signal falls within this range but remains outside the range above and below the set
point defined by the dead band, then the duration of the capacity control pulses will begin to decrease. As long
as the control signal remains within the range defined by the dead band, all capacity control pulses will stop.
3.11.1 Forward and Reverse
Capacity Control may be either forward or reverse acting, as described below. Which type of control is used is
dependent on the application of the compressor. Typically, if the compressor is controlled on discharge pressure
or slide valve position, the logic will be reversed. In all other applications, the logic will be forward acting.
The graphs below display a visual representation of both types of capacity control.
Forward
Forward acting capacity control manages the compressor control pulses via a time-proportioning scheme, as
illustrated below.
Instruction Manual | GEA Omni™
Control panel Control
Screw Compressor Capacity Control
GEA Refrigeration North America, Inc. | E_806550_2 | Generated 12.01.2016 199