Danfoss VLT FC 100, Operating Instructions Manual, Page: 128 / 193

20-81 PID Normal/ Inverse Control
Option: Function:
[0] * Normal Normal [0] causes the frequency converter’s output frequency to decrease when the feedback is
greater than the setpoint reference. This is common for pressure-controlled supply fan and pump
applications.
[1] Inverse
Inverse
[1] causes the frequency converter’s output frequency to increase when the feedback is
greater than the setpoint reference. This is common for temperature-controlled cooling applica-
tions, such as cooling towers.
20-93 PID Proportional Gain
Range: Function:
0.50 * [0.00 - 10.00 ] The proportional gain indicates the number of times the error between the set point and the
feedback signal is to be applied.
If (Error x Gain) jumps with a value equal to what is set in
par. 20-14
Maximum Reference/Feedb. the PID controller will try to
change the output speed equal to what is set in par. 4-13 Motor Speed
High Limit [RPM] /par. 4-14 Motor Speed High Limit [Hz] but in practice
of course limited by this setting.
The proportional band (error causing output to change from 0-100%)
can be calculated by means of the formula:
(
1
Proportional Gain
)
× ( Max Reference
)
Always set the desired for par. 20-14 Maximum Ref-
erence/Feedb. before setting the values for the PID
controller in meter group 20-9*.
20-94 PID Integral Time
Range: Function:
20.00 s* [0.01 - 10000.00 s] Over time, the integrator accumulates a contribution to the output from the PID controller as long
as there is a deviation between the Reference/Setpoint and feedback signals. The contribution is
proportional to the size of the deviation. This ensures that the deviation (error) approaches zero.
Quick response on any deviation is obtained when the integral time is set to a low value. Setting
it too low, however, may cause the control to become unstable.
The value set, is the time needed for the integrator to add the same contribution as the propor-
tional for a certain deviation.
If the value is set to 10,000, the controller will act as a pure proportional controller with a P-band
based on the value set in par. 20-93
PID Proportional Gain . When no deviation is present, the
output from the proportional controller will be 0.
22-21 Low Power Detection
Option: Function:
[0] * Disabled
[1] Enabled If selecting Enabled, the Low Power Detection commissioning must be carried out in order to set
the parameters in parameter group 22-3* for proper operation!
22-22 Low Speed Detection
Option: Function:
[0] * Disabled
[1] Enabled Select Enabled for detecting when the motor operates with a speed as set in par. 4-11
Motor
Speed Low Limit [RPM]
or par. 4-12
Motor Speed Low Limit [Hz]
.
VLT HVAC Drive High Power Operating In-
structions 6 How to Programme
MG.11.F3.02 - VLT ® is a registered Danfoss trademark
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