Emerson Vilter Vission 20/20, Operation And Service Manual

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6 – 5
Section 6 • Compressor Control
Vission 20/20 • Operation and Service Manual • Emerson • 35391SC 2.7
Figure 6-6. Compressor Control Screen - VFD Settings Control
Variable Frequency Drive (VFD) Settings
Control
The VFD page is where the operator can tune the motor
VFD for desired operation, see Figure 6-6. Compressor
Control Screen - VFD Settings Control. A Vilter
TM
com-
pressor uses the variable speed of a VFD controlled motor
to vary the amount of work or capacity of the compres-
sor. The basic one step VFD control will use the capacity
slide to control the first half of the total available capac -
ity and the motor speed to control the second half of the
total available capacity, see Figure 6-7, VFD One-Step
Control Method. For example, if the compressor needs
to load to 100% of its capacity, the control algorithm will
first move the capacity slide to its maximum position,
and 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, and 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 6-8. While loading the compressor will first
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 motor speed
of step two. At this point the compressor would be fully
loaded. Unloading occurs in the reverse direction. The
two-step control method is not typical for most installa-
tions and is normally used when a Vilter
TM
engineer rec-
ommends it.
NOTE
VFD installation is not covered in this manual. A VFD
that is not properly installed and configured has the
potential of causing intermittent and dangerous
problems. Please consult your VFD manual.
1 Step VFD Control:
•
Enables the first step in the VFD control algorithm.
This check box cannot be unselected by the operator.