20-81 PID Normal/Inverse Control
Option:
Function:
[0] *
Normal
[1]
Inverse
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.
20-82 PID Start Speed [RPM]
Range:
Function:
0 RPM*
[0 - par. 4-13 RPM]
When the adjustable frequency drive is first started, it initially ramps up to this output speed in
open-loop mode, following the active ramp-up time. When the output speed 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 [0], RPM.
20-93 PID Proportional Gain
Range:
Function:
0.50 N/A* [0.00 - 10.00 N/A]
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.
20-94 PID Integral Time
Range:
Function:
20.00 s*
[0.01 - 10000.00 s]
Over time, the integrator adds (integrates) the error between the feedback and the setpoint refer-
ence. This is required to ensure that the error approaches zero. Quick adjustable frequency drive
speed adjustment is obtained when this value is small. However, if a value that is too small is used,
the adjustable frequency drive’s output frequency may become unstable.
VLT
®
AQUA Drive
Instruction Manual
8 How to program the adjustable frequency
drive
MG.20.M5.22 - VLT
®
is a registered Danfoss trademark
8-35
8