FCM 300 Series
MG.03.B6.2G - VLT is a registered Danfoss trademark
Parameter Group 4: Special functions
Description of choice:
Select a limit to differentiator gain as required.
444 Process PID lowpass filter time
(PROC. FILTER TIME)
Settings:
0.01 - 10.00 sec [1 - 1000]
✭ 0.01 sec [1]
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/sec., 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.
✭ = General factory setting - also applying to spare part unit,
HH
HH
H = HVAC setting,
II
II
I = Industrial setting, ( ) = parameter
window text. [ ] = value for use in communication via serial communication port
445 Flying start
(FLYING START)
Settings:
H OK - both directions (OK-BOTH DIRECTIONS) [2]
★ Disable (DISABLE) [0]
OK - same direction (OK-SAME DIRECTION) [1]
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 an AC Line
drop-out.
Description of choice:
Select Disable if this function is not required.
OK - same direction: Chosen if the motor can only
rotate in same direction on cut-in.
OK - both directions: Chosen if the motor can rotate
in both directions on cut-in.
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:
1. Too low inertia will cause acceleration of the
load, which may be dangerous or prevent
succesful Flying start. Use DC brake instead.
2. If load is driven eg. by "windmilling", the unit
might trip due to overvoltage.
3. Below 250 rpm the Flying start will not function.
446 Switching pattern
(SWITCH PATTERN)
Settings:
H 60° AVM (60° AVM) [0]
★ SFAVM (SFAVM) [1]
Description of choice:
Normally it is not necessary for the customer to set
this parameter.
12-6
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).
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