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Section 6
•
Compressor Control
Vission 20/20 • Operation and Service Manual • Emerson • 35391SC 2.7
Figure 6-20. Compressor Control Screen - Step VI (Twin Screw)
Step VI
• If this method is selected then the VI Digital Outputs
will be controlled according to the current volume
ratio.
Step 1
•
This setpoint defines the minimum step value for
Step VI control. The default value for Step 1 is 2.2.
This value is used for the calculation of Step 1 & Step 2
Digital Outputs. When Volume Ratio is less than aver-
age of Step 1 & Step 2, Low VI Output will be ON and
High VI Digital Output will be OFF.
Step 2
•
This setpoint defines the intermediate step value for
Step VI control. The default value for Step 2 is 3.5.
This value is used for calculation of Step 2 & Step 3
Digital Outputs. When Volume Ratio is greater than
average of Step 1 & Step 2 and also less than average
of Step 2 & Step 3, Low VI Digital Output will be OFF
and High VI Digital Output will be ON.
Step 3
•
This setpoint defines the maximum step value for
Step VI control. The default value for Step 3 is 5.0.
This value is used for calculation of Step 2 & Step 3
Digital Outputs. When Volume Ratio is greater than
average of Step 2 & Step 3, both Low VI and High VI
Digital Outputs will be OFF.
Time Interval
•
This setpoint specifies the time interval after which
the volume ratio is calculated to determine the cur-
rent step in Step VI Control.
Volume Ratio
LOW VI DIGITAL OUTPUT HIGH IV DIGITAL OUTPUT
< Average (Step1 & Step2)
ON
OFF
> Average (Step1 & Step2) and <
Average (Step2 & Step3)
OFF
ON
> Average (Step2 & Step3)
OFF
OFF
Table 6-2. Step VI Digital Outputs depending on Volume Ratio
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