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Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 1.8.5153
The auto-cycle function will operate only in local “Auto”
mode and Direct I/O “Remote Auto” mode. If the au-
to-cycle feature is enabled while running in any other
remote mode, the function will simply be ignored.
However, the Minimum slide position will continue to
be respected in Remote “Auto” mode. If the compres-
sor changes from a remote mode back to Local “Auto”
mode, the auto-cycle feature will operate normally.
NOTE
When the Pump-down Feature is enabled, the Auto-
cycle setpoints are automatically disabled. Pump-
down mode will cause the compressor to cycle off
via the Pump-down Stop Pressure setpoint, and will
not allow the compressor to start again.
Enable:
• Enables the Auto-cycle control. Uncheck the box to
disable the Auto-cycle set-points.
Start Pressure:
• When the suction pressure meets or exceeds this set-
point, the compressor will start.
Start Delay:
• Delays the compressor from starting when the suc-
tion pressure meets or exceeds this setpoint.
Stop Pressure:
• When the suction pressure meets or falls below this
setpoint, the compressor will stop.
Stop Delay:
• Delays the compressor from stopping when the suc-
tion pressure meets or exceeds this setpoint.
Minimum Slide Position:
• The minimum capacity slide position that the com-
pressor is allowed to run at.
Variable Frequency Drive (VFD)
The VFD page is where the operator can tune the mo-
tor VFD for desired operation. A Vilter compressor uses
the variable speed of a VFD controlled motor to vary
the amount of work or capacity of the compressor. The
basic one step VFD control will use the capacity slide to
control the fi rst half of the total available capacity and
the motor speed to control the second half of the total
available capacity, see Figure 6-3. VFD One-Step Control
Method. For example, if the compressor needs to load
to 100% of its capacity. The control algorithm will fi rst
move the capacity slide to its maximum position, then
the motor speed will ramp up to its maximum speed.
In the unloading direction, the motor speed will ramp
down to its minimum speed, then the capacity slide will
move to its minimum position.
The two-step control method works much like the one-
step method but divides the control into four sections,
see Figure 6-4. VFD Two-Step Control Method. While
loading; the compressor will fi rst move the capacity
slide to the maximum set for step one then speed up the
motor to its maximum speed for the same step. Once
step one has completed, the control algorithm will again
move the capacity slide to the maximum position and
the maximum speed of step two. At this point the com-
pressor would be fully loaded. Unloading occurs in the
reverse direction. The two-step control method is not
typical for most installations and is normally used when
a Vilter engineer recommends it.
Section 6 • Compressor Control
Figure 6-3. VFD One-Step Control Method
Figure 6-4. VFD Two-Step Control Method