Compressor Variable Frequency Drive(Vfd) Control - Emerson VILTER MicroVission Operation And Service Manual

Section 5 • Compressor Control
Compressor Variable Frequency Drive(VFD)
Control
The VFD page is where the operator can tune the
motor´s VFD for the desired operation, see Figure 5-12.
Compressor Control Screen - VFD Settings Control.
A reciprocating compressor uses the variable speed of
a VFD-controlled motor to vary the amount of work or
capacity of the compressor.
When VFD Control is enabled, the first half of the total
available capacity is controlled using load steps, and the
motor speed is used to control the second half of the to-
tal available capacity.
If the compressor needs to load to 100% of its capac-
ity, the control algorithm will first load all the cylinders,
and then the motor speed will ramp up to its maximum
speed. In the unloading direction, the motor speed will
first ramp down to its minimum speed, and then the cyl-
inders will be unloaded.
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.
Figure 5-12. Compressor Control Screen - VFD Settings Control
MicroVission Controller • Operation and Service Manual • Emerson • 35391MV 1.3
NOTE
VFD Speed:
• Defines the minimum and maximum speed for the
motor.
P = Proportional (gain) setpoint:
• Used to adjust the motor speed action in direct
proportion to the difference between the control
setpoint and the process variable (SP - PV error).
• This is a unit-less quantity and is used for coarse
adjustment, and this setpoint should be set to the
lowest value that gives adequate control system
response.
• Increasing the Proportional setting increases the
control system's sensitivity to small process fluc-
tuations and the tendency to hunt.
I = Integral (reset) setpoint:
• Used to adjust the load control action, integrating
the error over time, to account for a small error that
has persisted for a long time.
First half controlled with
loading/unloading steps
Total Capacity
Second half controlled by
VFD
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