Emerson Vilter MicroVission - Compressor Variable Frequency Drive(VFD) Control

5 – 13
Section 5 • Compressor Control
MicroVission Controller • Operation and Service Manual • Emerson • 35391MV 1.3
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 rst 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 rst load all the cylinders,
and then the motor speed will ramp up to its maximum
speed. In the unloading direction, the motor speed will
rst ramp down to its minimum speed, and then the cyl-
inders will be unloaded.
NOTE
VFD installation is not covered in this manual. A VFD that
is not properly installed and congured has the potential
of causing intermittent and dangerous problems. Please
consult your VFD manual.
VFD Speed:
• Denes 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 uc-
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.
Figure 5-12. Compressor Control Screen - VFD Settings Control
Total Capacity
First half controlled with
loading/unloading steps
Second half controlled by
VFD