Danfoss VLT 6000 HVAC Series User Manual

423 PID proportional gain
(PID PROP. GAIN)
Value:
0.00 - 10.00
0.01
Function:
The proportional gain indicates the number of times
the deviation between the reference/setpoint and the
feedback signal is to be applied.
Used in Closed loop [1] (parameter 100).
Description of choice:
Quick regulation is obtained by a high gain, but if the
gain is too high, the process may become unstable.
424 PID integration time
(PID INTEGR.TIME)
Value:
0.01 - 9999.00 sec. (OFF)
OFF
Function:
The integrator provides a constant change of the out-
put frequency during constant error between the ref-
erence/setpoint and the feedback signal.
The greater the error, the quicker the integrator fre-
quency contribution will increase. The integration time
is the time needed by the integrator to reach the same
gain as the proportional gain for a given deviation.
Used in Closed loop [1] (parameter 100).
Description of choice:
Fast regulation is obtained in connection with a short
integration time. However, this time
may be too short, which means that the process may
be destabilised as a result of overswings.
If the integral time is long, major deviations from the
required set point may occur, since the process regu-
lator will take a long time to regulate in relation to a
given error.
NB!
Some value other than OFF must be set
or the PID will not function correctly.
425 PID differentiation time
(PID DIFF. TIME)
Value:
0.00 (OFF) - 10.00 sec.
OFF
Function:
The differentiator does not react to a constant error. It
only contributes when the error changes. The quicker
the error changes, the stronger the contribution from
the differentiator will be. This influence is proportional
to the speed by which the deviation changes.
Used in Closed loop [1] (parameter 100).
Description of choice:
Fast regulation can be obtained by means of a long
differentiation time. However, this time may be too
long, which means that the process may be destabi-
lised as a result of overswings.
426 PID differentiator gain limit
(PID DIFF. GAIN)
Value:
5.0 - 50.0
5.0
Function:
It is possible to set a limit for the differentiator gain. The
differentiator gain will increase if there are fast
changes, which is why it can be beneficial to limit this
gain, thereby obtaining a pure differentiator gain at
slow changes and a constant differentiator gain where
quick changes to the deviation are made.
Used in Closed loop [1] (parameter 100).
Description of choice:
Select a limit to differentiator gain as required.
427 PID lowpass filter time
(PID FILTER TIME)
Value:
0.01 - 10.00
0.01
Function:
Oscillations on the feedback signal are dampened by
the lowpass filter in order to reduce their impact on the
process regulation. This can be an advantage if there
is a lot of noise on the signal.
Used in Closed loop [1] (parameter 100).
Description of choice:
Select the desired time constant (τ). If a time constant
(τ) of 0.1 s is programmed, the break frequency for the
lowpass filter will be 1/0.1 = 10 RAD/sec., correspond-
ing to (10/(2 x π )) = 1.6 Hz.
VLT
®
6000 HVAC Series
= factory setting, () = display text, [] = value for use in communication via serial communication port
152 MG.61.B5.02 - VLT
®
is a registered Danfoss trademark

Danfoss VLT 6000 HVAC Series Specifications

General

Brand	Danfoss
Model	VLT 6000 HVAC Series
Category	DC Drives
Language	English