Parameter
Description of function
7-33 Process PID Proportional Gain
The higher the value - the quicker the control. However, too large value may lead to
oscillations.
7-34 Process PID Integral Time
Eliminates steady state speed error. Lower value means quick reaction. However, too small
value may lead to oscillations.
7-35 Process PID Differentiation Time
Provides a gain proportional to the rate of change of the feedback. A setting of zero
disables the differentiator.
7-36 Process PID Diff. Gain Limit
If there are quick changes in reference or feedback in a given application - which means
that the error changes swiftly - the differentiator may soon become too dominant. This is
because it reacts to changes in the error. The quicker the error changes, the stronger the
differentiator gain is. The differentiator gain can thus be limited to allow setting of the
reasonable differentiation time for slow changes.
7-38 Process PID Feed Forward Factor
In application where there is a good (and approximately linear) correlation between the
process reference and the motor speed necessary for obtaining that reference, the Feed
Forward Factor can be used to achieve better dynamic performance of the Process PID
Control.
5-54 Pulse Filter Time Constant #29 (Pulse
term. 29),
5-59 Pulse Filter Time Constant #33 (Pulse
term. 33),
6-16 Terminal 53 Filter Time Constant (Analog
term 53),
6-26 Terminal 54 Filter Time Constant (Analog
term. 54)
6-36 Term. X30/11 Filter Time Constant
6-46 Term. X30/12 Filter Time Constant
35-46 Term. X48/2 Filter Time Constant
If there are oscillations of the current/voltage feedback signal, these can be dampened by
means of a low-pass filter. This time constant represents the speed limit of the ripples
occurring on the feedback signal.
Example: If the low-pass filter has been set to 0.1s, the limit speed is 10 RAD/s (the
reciprocal of 0.1 s), corresponding to (10/(2 x π)) = 1.6 Hz. This means that all currents/
voltages that vary by more than 1.6 oscillations per second is damped by the filter. The
control is only carried out on a feedback signal that varies by a frequency (speed) of less
than 1.6 Hz.
The low-pass filter improves steady state performance, but selecting a too large filter time
deteriorates the dynamic performance of the Process PID Control.
Table 3.5 Relevant Parameters for Process Control
3.6.6.4 Advanced PID Control
Consult the
VLT
®
AutomationDrive FC 301/FC 302
Programming Guide
for advanced PID control parameters
3.6.7 Internal Current Control in VVC
+
Mode
When the motor current/torque exceed the torque limits
set in
4-16 Torque Limit Motor Mode
,
4-17 Torque Limit
Generator Mode
and
4-18 Current Limit
, the integral current
limit control is activated.
When the frequency converter is at the current limit during
motor operation or regenerative operation, it tries to get
below the preset torque limits as quickly as possible
without losing control of the motor.
3.6.8 Local (Hand On) and Remote (Auto
On) Control
The frequency converter can be operated manually via the
local control panel (LCP) or remotely via analog and digital
inputs and serial bus. If allowed in
0-40 [Hand on] Key on
LCP
,
0-41 [Off] Key on LCP
,
0-42 [Auto on] Key on LCP
, and
0-43 [Reset] Key on LCP
, it is possible to start and stop the
frequency converter via the LCP pressing [Hand On] and
[Off]. Alarms can be reset via [Reset]. After pressing [Hand
On], the frequency converter goes into Hand mode and
follows (as default) the local reference that can be set
using the navigation keys on the LCP.
After pressing [Auto On], the frequency converter enters
Auto mode and follows (as default) the remote reference.
In this mode, it is possible to control the frequency
converter via the digital inputs and various serial interfaces
(RS-485, USB, or an optional fieldbus). See more about
starting, stopping, changing ramps and parameter set-ups
etc. in parameter group
5-1* Digital Inputs
or parameter
group
8-5* Serial communication
.
130BP046.10
Hand
on
Off
Auto
on
Reset
Illustration 3.10 Operation Keys
Basic Operating Principles
VLT
®
AutomationDrive FC 301/FC 302 Design Guide, 0.25-75 kW
MG33BF02 - Rev. 2013-12-20
27
3
3