20-84 On Reference Bandwidth
Range:
Function:
5 %
*
[0 -
200 %]
When the difference between the feedback and the
setpoint reference is less than the value of this
parameter, the frequency converter’s display will
show “Run on Reference”. This status can be
communicated externally by programming the
function of a digital output for
Run on Reference/No
Warning
[8]. In addition, for serial communications,
the On Reference status bit of the frequency
converter’s Status Word will be high (1).
The
On Reference Bandwidth
is calculated as a
percentage of the setpoint reference.
3.18.7 20-9* PID Controller
This group provides the ability to manually adjust this PID
Controller. By adjusting the PID Controller parameters the
control performance may be improved. See section PID in
the VLT HVAC Drive Design Guide,
MG.11.Bx.yy
for guidelines
on adjusting the PID Controller parameters.
20-91 PID Anti Windup
Option: Function:
[0]
Off
Off
[0] The integrator will continue to change value also
after output has reached one of the extremes. This can
afterwards cause a delay of change of the output of the
controller.
[1]
*
On
On
[1] The integrator will be locked if the output of the
built in PID controller has reached one of the extremes
(min or max value) and therefore not able to add further
change to the value of the process parameter controlled.
This allows the controller to respond more quickly when
it again can control the system.
20-93 PID Proportional Gain
Range:
Function:
0.50
*
[0.00 - 10.00 ]
If (Error x Gain) jumps with a value equal to what is set in
20-14 Maximum Reference/Feedb.
the PID controller will try to
change the output speed equal to what is set in
/
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
20-14 Maximum Reference/Feedb.
before setting the values for the PID controller in parameter
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 propor-
tional 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
. When no deviation is
present, the output from the proportional
controller will be 0.
Parameter Description
VLT
®
HVAC Drive Programming Guide
MG.11.CB.02 - VLT
®
is a registered Danfoss trademark
131
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