20-21 Setpoint 1
Range: Function:
0.000 Proc-
essCtrlU-
nit*
[-999999.999 - 999999.999 Proc-
essCtrlUnit]
Setpoint 1 is used in closed-loop mode to enter a setpoint reference that is used by the adjustable
frequency drive’s PID controller. See the description of par.20-20
Feedback Function
.
NOTE!
Setpoint reference entered here is added to any other references that are enabled
(see par. group 3-1*).
20-22 Setpoint 2
Range: Function:
0.000 Proc-
essCtrlU-
nit*
[-999999.999 - 999999.999 Proc-
essCtrlUnit]
Setpoint 2 is used in closed-loop mode to enter a setpoint reference that may be used by the ad-
justable frequency drive’s PID controller. See the description of
Feedback Function
, par.
20-20
Feedback Function
.
NOTE!
The setpoint reference entered here is added to any
other references that are enabled (see par. group
3-1*).
20-81 PID Normal/ Inverse Control
Option: Function:
[0] * Normal
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.
[1] Inverse
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.
20-93 PID Proportional Gain
Range: Function:
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
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
)
NOTE!
Always set the desired for par. 20-14
Maximum Reference/Feedb.
before setting the values for the PID controller in par. group 20-9*.
6 How to program the adjustable frequency
drive
VLT
®
HVAC Drive Instruction Manual
6-48
MG.11.A9.22 - VLT
®
is a registered Danfoss trademark
6
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