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Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 1.8.5153
Section 6 • Compressor Control
Overview
The compressor control screen is where an operator can
set the majority of the compressor settings. These set-
ting defi ne how the compressor will operate and respond
to changing loads. The compressor control screen con-
sists of several screens but in order not to overwhelm the
operator with options, many of the screens may not be
visible. How the compressor is confi gured in the confi gu-
ration screen will determine what screens are displayed.
It is important to note that there isn’t one correct way to
set these parameters. Every application is different and
requires the operator to tune these settings to achieve
the best operation, see Figure 6-1. Compressor Control
Screen.
Pulse Proportional Control
The Vission 20/20 uses a pulse proportional control
method to control the compressor capacity slide valve
in order to maintain the control setpoint. The control
setpoint can either be process temperature control set-
point or suction pressure control setpoint depending on
what the operator has selected as the control mode.
The proportion control uses the Interval Time Setpoint
to defi ne the time the algorithm waits to read the cur-
rent setpoint and calculates the error from the process
control setpoint. Based on the error from setpoint, the
algorithm calculates a pulse time in which the capacity
slide is moved in the direction of the error. The further
away the process variable is from the control setpoint,
the larger the corrective pulse will be. The duration of
the pulse is limited by the Pulse Time Setpoint. By de-
fault the maximum pulse time is the same as the interval
time. This means that the pulse time can be 100% of the
interval time given a near continuous movement of the
capacity slide. Adjusting these setpoints can be useful
in slowing down the reaction time of the compressor if
large thermal time contents are present in the refrigera-
tion cycle.
Figure 6-1. Compressor Control Screen