Danfoss VLT Brook Crompton Motor FCM 300, Design Manual

Page: 61 / 102

Function:
The proportional gain indicates the number of times the
error between the set point and the feedback signal is to
be applied.
Used together with
Process, closed loop mode (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.
441 Process PID integral time
Value:
0.01-9999 s (OFF) [1-999900]
9999 s [999900]
Function:
The integrator provides an increasing gain at a constant
error between the set point and the feedback signal. The
greater the error, the quicker the gain will increase. The
integral time is the time needed by the integrator to reach
the same gain as the proportional gain.
Used together with
Process, closed loop mode (parameter
100).
Description of choice:
Quick regulation is obtained at a short integral time.
However, this time may become too short, which can
make the process unstable.
If the integral time is long, major deviations from the
required set point may occur, since the process regulator
will take a long time to regulate in relation to a given
error.
442 Process PID differentiation time
Value:
0.00 (Off)-10.00 s [0-1000]
0.00 s [0]
Function:
The differentiator does not react to a constant error. It only
provides a gain when the error changes. The quicker the
error changes, the stronger the gain from the differen-
tiator.
The gain is proportional to the speed at which the error
changes.
Used together with
Process, closed loop mode (parameter
100).
Description of choice:
Fast regulation is obtained with a long differentiation time.
However, this time may become too long, which can make
the process unstable.
443 Process PID diff. gain limit
Value:
5.0-50.0 [50-500]
5.0 [50]
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 error occur.
Used together with
Process, closed loop mode (parameter
100).
Description of choice:
Select a limit to differentiator gain as required.
444 Process PID lowpass filter time
Value:
0.02-10.00 s [2-1000]
0.02 s [2]
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 e.g. if there is
a lot of noise on the signal.
Used together with
Process, closed loop mode (parameter
100).
Description of choice:
Select the desired time constant (τ). If a time constant (τ)
of 100 ms is programmed, the break frequency for the
lowpass filter will be 1/0.1 = 10 RAD/s., corresponding to
(10/2 x π) = 1.6 Hz.
The process regulator will thus only regulate a feedback
signal that varies by a frequency lower than 1.6 Hz. If the
feedback signal varies by a higher frequency than 1.6 Hz,
the Process regulator will not react.
445 Flying start
Value:
Disable (DISABLE) [0]
OK - same direction (OK-SAME DIRECTION) [1]
OK - both directions (OK-BOTH DIRECTIONS) [2]
DC-brake before start
(DC-BRAKE BEF. START)
[3]
Function:
This function makes it possible to ‘catch‘ a motor, which is
spinning freely because of a mains dropout.
Description of choice:
Select [0] Disable if this function is not required.
[1} OK - same direction : Chosen if the motor can only rotate
in same direction on cut-in.
[2] OK - both directions : Chosen if the motor can rotate in
both directions on cut-in.
[3] DC-brake - before start : Selected if the motor is to be
stopped using DC brake before the motor is ramped up to
the desired speed. The DC brake time must be set in
parameter 126.
Limitations:
Programming
VLT
®
DriveMotor FCM Series
MG03BA02 - VLT
®
is a registered Danfoss trademark 59
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