Danfoss VLT HVAC Series, Руководство по программированию, Страница: 204 / 338

20-83 PID Start Speed [Hz]
Range: Function:
0 Hz* [0.0 - par. 4-14 Hz] When the adjustable frequency drive is first started, it initially ramps up to this output frequency in
open-loop mode, following the active ramp-up time. When the output frequency programmed here
is reached, the adjustable frequency drive will automatically switch to closed-loop mode and the
PID controller will begin to function. This is useful in applications in which the driven load must first
quickly accelerate to a minimum speed when it is started.
NOTE!
This parameter will only be visible if par.0-02 Motor Speed Unit is set to [1], Hz.
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 adjustable frequency drive’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 adjustable
frequency drive’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 ex-
tremes. 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 N/A* [0.00 - 10.00 N/A] 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 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*.
3 Parameter Description VLT ® HVAC Drive Programming Guide
3-180
MG.11.C6.22 - VLT ® is a registered Danfoss trademark
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