Danfoss VLT AutomationDrive FC 302 Programming Manual page 53

Parameter Descriptions
1-80 Function at Stop
Option: Function:
[4] DC Voltage When the motor is stopped, the
U0 parameter 1-55 U/f Characteristic - U [0]
parameter defines the voltage at 0 Hz.
[5] Coast at low When the reference is below 1-81 Min Speed
reference for Function at Stop [RPM], the motor is
disconnected from the frequency converter.
[6] Motor check,
alarm
1-81 Min Speed for Function at Stop [RPM]
Range: Function:
Size related [0 - 600 RPM] Set the speed at which to activate
*
1-80 Function at Stop.
1-82 Min Speed for Function at Stop [Hz]
Range: Function:
Size related [ 0 - 20.0 Hz] Set the output frequency at which
*
to activate 1-80 Function at Stop.
1-83 Precise Stop Function
Option: Function:
NOTICE
This parameter cannot be adjusted while
the motor is running.
FC 302 only.
[0] Precise Only optimal when the operational speed - of e.g.
ramp the conveyor belt - is constant. This is an open
*
stop loop control. Achieves high repetitive precision at
the stopping point.
[1] Cnt stop Counts the number of pulses, typically from an
with encoder and generates a stop signal after a pre-
reset programmed number of pulses -
parameter 1-84 Precise Stop Counter Value - has
been received at T29 or T33 [30].
This is a 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 is reset.
[2] Cnt stop Same as [1] but the number of pulses counted
w/o during ramp down to 0 RPM is deducted from the
reset counter value entered in parameter 1-84 Precise
Stop Counter Value.
This reset function can for example be used to
compensate for the extra distance done during
ramping down and to reduce the impacts of
gradual wear of mechanical parts.
®
VLT AutomationDrive FC 301/302 Programming Guide
1-83 Precise Stop Function
Option:
[3] Speed
comp
stop
[4] Com cnt
stop
w/rst
[5] Comp
cnt stop
w/o r
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. A test
must be done 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 parameter 3-42 Ramp 1
Ramp Down Time, parameter 3-52 Ramp 2 Ramp Down Time,
parameter 3-62 Ramp 3 Ramp down Time and
parameter 3-72 Ramp 4 Ramp Down Time.
The Precise Stop Function is set up here and enabled from
DI T29 or T33.
1-84 Precise Stop Counter Value
Range:
100000
*
MG33MI02 - Rev. 2013-11-20
Function:
Stops at precisely the same point, 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 has ramped up
before activating the speed compensated stop.
Same as [3] but after each precise stop the
number of pulses counted during ramp down to
0 RPM is reset.
Same as [3] but the 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 for example be used to
compensate for the extra distance done during
ramping down and to reduce the impacts of
gradual wear of mechanical parts.
Function:
[0 - Enter the counter value to be used in
999999999 ] the integrated precise stop function,
parameter 1-83 Precise Stop Function.
The maximum permissible frequency at
terminal 29 or 33 is 110 kHz.
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