Danfoss VLT HVAC Drive FC 102 Operating Instructions Manual page 99

How to Programme
20-81 PID Normal/ Inverse Control
Option: Function:
[0] Normal The frequency converter's output frequency
*
decreases when the feedback is greater than the
setpoint reference. This behaviour is common for
pressure-controlled supply fan and pump
applications.
[1] Inverse The frequency converter's output frequency
increases when the feedback is greater than the
setpoint reference. This behaviour is common for
temperature-controlled cooling applications, such
as cooling towers.
20-93 PID Proportional Gain
Range: Function:
NOTICE
0.50 [0 - 10 ]
*
Always set the desired value for
20-14 Maximum Reference/Feedb. before
setting the values for the PID controller
in parameter group 20-9* PID Controller.
The proportional gain indicates the number of
times the error between the setpoint and the
feedback signal is to be applied.
If (Error x Gain) jumps with a value equal to what is set in
20-14 Maximum Reference/Feedb., the PID controller tries to
change the output speed equal to what is set in
parameter 4-13 Motor Speed High Limit [RPM]/
parameter 4-14 Motor Speed High Limit [Hz]. However, the
output speed is limited by this setting.
The proportional band (error causing output to change
from 0-100%) can be calculated with the formula:
1
Max Reference
×
Proportional Gain
20-94 PID Integral Time
Range: Function:
20 [0.01 - The integrator accumulates a contribution to
s 10000 s] 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 for a certain deviation.
If the value is set to 10000, the controller acts
as a pure proportional controller with a P-band
based on the value set in parameter 20-93 PID
MG11F502
Operating Instructions
20-94 PID Integral Time
Range:
22-21 Low Power Detection
Option:
[0] Disabled
*
[1] Enabled Carry out the low-power detection commis-
22-22 Low Speed Detection
Option:
[0] Disabled
*
[1] Enabled Detects when the motor operates with a speed
22-23 No-Flow Function
Common actions for low-power detection and low-speed
detection (individual selections not possible).
Option:
[0] Off
*
[1] Sleep Mode The frequency converter enters sleep mode
[2] Warning
[3] Alarm
NOTICE
Do not set 14-20 Reset Mode, to [13] Infinite auto reset,
when parameter 22-23 No-Flow Function is set to [3]
Alarm. Doing so causes the frequency converter to
continuously cycle between running and stopping when
a no-flow condition is detected.
Danfoss A/S © 08/2014 All rights reserved.
Function:
Proportional Gain. When no deviation is present,
the output from the proportional controller is 0.
Function:
sioning to set the parameters in parameter group
22-3* No-Flow Power Tuning for proper operation.
Function:
as set in parameter 4-11 Motor Speed Low Limit
[RPM] or parameter 4-12 Motor Speed Low Limit
[Hz].
Function:
and stops when a no-flow condition is
detected. See parameter group 22-4* Sleep
Mode for programming options for sleep
mode.
The frequency converter continues to run, but
activates a no-flow warning [W92]. A digital
output or a serial communication bus can
communicate a warning to other equipment.
The frequency converter stops running and
activates a no-flow alarm [A 92]. A frequency
converter digital output or a serial communi-
cation bus can communicate an alarm to
other equipment.
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