Danfoss VLT FC 100 Operating Instructions Manual page 128

VLT HVAC Drive High Power Operating In-
structions
20-81 PID Normal/ Inverse Control
Option:
[0] * Normal
[1] Inverse
20-93 PID Proportional Gain
Range:
0.50 * [0.00 - 10.00 ]
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
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:
20-94 PID Integral Time
Range:
20.00 s* [0.01 - 10000.00 s]
22-21 Low Power Detection
Option:
[0] * Disabled
[1] Enabled
22-22 Low Speed Detection
Option:
[0] * Disabled
[1] Enabled
Function:
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.
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.
Function:
The proportional gain indicates the number of times the error between the set point and the
feedback signal is to be applied.
(
Proportional Gain
Motor Speed
Function:
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
output from the proportional controller will be 0.
Function:
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!
Function:
Select Enabled for detecting when the motor operates with a speed as set in par. 4-11
Speed Low Limit [RPM] or par. 4-12 Motor Speed Low Limit [Hz] .
MG.11.F3.02 - VLT ® is a registered Danfoss trademark
)
1
× ( Max Reference )
Always set the desired for par. 20-14
erence/Feedb. before setting the values for the PID
controller in meter group 20-9*.
PID Proportional Gain . When no deviation is present, the
6 How to Programme
6
Maximum Ref-
Motor
127