Pid Normal/ Inverse Control; Pid Start Speed; Pid Proportional Gain; Pid Integral Time - Danfoss VLT HVACDrive Instruction Manual

VLT ® HVAC Drive Instruction Manual

20-81 PID Normal/ Inverse Control

Option:
[0] * Normal
[1] Inverse
20-82 PID Start Speed [RPM]
Range:
Application [Application dependant]
dependent*
20-83 PID Start Speed [Hz]
Range:
Application [Application dependant]
dependent*

20-93 PID Proportional Gain

Range:
0.50 N/A* [0.00 - 10.00 N/A]
If (Error x Gain) jumps with a value equal to what is set in par. 20-14
Motor Speed High Limit [RPM]
equal to what is set in par. 4-13
The proportional band (error causing output to change from 0–100%) can be calculated by means of the formula:
( )
1
× ( Max Reference
Proportional Gain
NOTE!
Always set the desired for par. 20-14

20-94 PID Integral Time

Range:
20.00 s* [0.01 - 10000.00 s]
Function:
Normal [0] causes the adjustable frequency drive'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 adjustable frequency drive'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:
Function:
Function:
Maximum Reference/Feedb.
Motor Speed High Limit [Hz]
/par. 4-14
)
Maximum Reference/Feedb. before setting the values for the PID controller in par. group 20-9*.
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 proportional
part 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
from the proportional controller will be 0.
MG.11.AB.22 - VLT ® is a registered Danfoss trademark
7 How to Program the Adjustable Frequency
, the PID controller will try to change the output speed
but in practice of course limited by this setting.
PID Proportional Gain
. When no deviation is present, the output
Drive
7
7-41