Danfoss VLT AutomationDrive FC 301 Programming Manual page 73

Parameter Descriptions
1-83 Precise Stop Function
Option: Function:
NOTICE
This parameter cannot be
adjusted while the motor is
running.
Valid for FC 302 only.
[0] Precise ramp Only optimal when the operational
*
stop speed, for example the operational
speed of a conveyor belt, is
constant. This is an open-loop
control. Achieves high repetitive
precision at the stop point.
[1] Cnt stop with Counts the number of pulses,
reset typically from an encoder, and
generates a stop signal after a pre-
programmed number of pulses,
defined in parameter 1-84 Precise
Stop Counter Value, has been
received at terminal 29 or terminal
33.
This is direct feedback with one-
way closed-loop control.
The counter function is activated
(starts timing) at the edge of the
start signal (when it changes from
stop to start). After each precise
stop, the number of pulses counted
during ramp-down to 0 RPM are
reset.
[2] Cnt stop w/o Same as [2] Cnt stop with reset but
reset the number of pulses counted
during ramp-down to 0 RPM are
deducted from the counter value
entered in parameter 1-84 Precise
Stop Counter Value.
This reset function can be used to
compensate for the extra distance
done during ramping down and to
reduce the impacts of gradual wear
of mechanical parts.
[3] Speed comp Stops at precisely the same point,
stop regardless of the present speed.
The stop signal is delayed internally
when the present speed is lower
than the maximum speed (set in
parameter 4-19 Max Output
Frequency).
The delay is calculated on the basis
of the reference speed of the
frequency converter and not on the
basis of the actual speed. Make
sure that the frequency converter
M0013101
Programming Guide
1-83 Precise Stop Function
Option:
[4]
[5]
The precise stop functions are advantageous in
applications where high precision is required.
If using a standard stop command, the accuracy is
determined by the internal task time. That is not the case
when using the precise stop function. It eliminates the task
time dependence and increases the accuracy substantially.
The frequency converter tolerance is normally given by its
task time. However, by using its special precise stop
function, the tolerance is independent of the task time
because the stop signal immediately interrupts the
execution of the frequency converter program. The precise
stop function gives a highly reproducible delay from the
stop signal is given until the ramping down starts. Run a
test to find this delay as it is a sum of sensor, PLC,
frequency converter, and mechanical parts.
To ensure optimum accuracy, there should be at least 10
cycles during ramping down, see:
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The precise stop function is set up here and enabled from
DI at terminal 29 or terminal 33.
1-84 Precise Stop Counter Value
Range:
100000
*
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Function:
has ramped up before activating
the speed–compensated stop.
Com cnt stop Same as Speed comp stop but after
w/rst each precise stop, the number of
pulses counted during ramp-down
to 0 RPM are reset.
Comp cnt stop Same as Speed comp stop but the
w/o r number of pulses counted during
ramp-down to 0 RPM is deducted
from the counter value entered in
parameter 1-84 Precise Stop Counter
Value.
This reset function can be used to
compensate for the extra distance
done during ramping down and to
reduce the impacts of gradual wear
of mechanical parts.
Parameter 3-42 Ramp 1 Ramp Down Time.
Parameter 3-52 Ramp 2 Ramp Down Time.
Parameter 3-62 Ramp 3 Ramp down Time.
Parameter 3-72 Ramp 4 Ramp Down Time.
Function:
[0 - Enter the counter value to be used
999999999 ] in the integrated precise stop
function, parameter 1-83 Precise Stop
Function.
The maximum permissible
frequency at terminal 29 or 33 is
110 kHz.
3 3
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