Precise Stop Function - Danfoss VLT AutomationDrive Programming Manual

Parameter Descriptions
1-80 Function at Stop
Option: Function:
1.35 hp [1 kW] = 0.2 seconds
13.5 hp [10 kW] = 0.5 seconds
135 hp [100 kW] = 1.7 seconds
1,350 hp [1,000 kW] = 2.5 seconds
[4] DC Voltage When the motor is stopped, the P1-55 [0]
U0 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 Adjustable frequency
drive.
1-81 Min Speed for Function at Stop [RPM]
Range:
Size related [0 - 600 RPM] Set the speed at which to activate
*
1-82 Min Speed for Function at Stop [Hz]
Range:
Size related [ 0.0 - 20.0 Hz]
*

1-83 Precise Stop Function

Option: Function:
[0] Precise Only optimal when the operational speed of, for
ramp example, the conveyor belt is constant. This is
*
stop an open-loop control. Achieves high repetitive
precision at the stopping point.
[1] Cnt stop Counts the number of pulses, typically from an
with reset encoder and generates a stop signal after a pre-
programmed number of pulses - 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 reset during ramp-down to 0 rpm is deducted from
the counter value entered in 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 impact of
gradual wear on mechanical parts.
[3] Speed Stops at precisely the same point, regardless of
comp the present speed, the stop signal is delayed
stop internally when the present speed is lower than
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FC 300 Programming Guide
Function:
1-80 Function at Stop.
Function:
®
MG33MD22 - VLT is a registered Danfoss trademark
1-83 Precise Stop Function
Option: Function:
the maximum speed (set in 4-19 Max Output
Frequency).
The delay is calculated on the basis of the
reference speed of the Adjustable frequency
drive and not on the basis of the actual speed.
Please therefore make sure that the Adjustable
frequency drive has ramped up before you
activate the speed compensated stop.
[4] Com cnt Same as [3] but after each precise stop, the
stop w/rst number of pulses counted during ramp-down to
0 rpm is reset.
[5] Comp cnt Same as [3] but the number of pulses counted
stop w/o during ramp-down to 0 rpm is deducted from
r the counter value entered in 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 impact of
gradual wear on mechanical parts.
The precise stop functions are advantageous in
applications where high precision is required.
If you use a standard stop command the accuracy is
determined by the internal task time. That is not the case
when you use the precise stop function; it eliminates the
task time dependence and increases the accuracy substan-
tially.
The Adjustable frequency drive 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 Adjustable frequency drive 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, Adjustable frequency drive and mechanical
parts.
To ensure optimum accuracy, there should be at least 10
cycles during ramping down, see 3-42 Ramp 1 Ramp Down
Time, 3-52 Ramp 2 Ramp down Time, 3-62 Ramp 3 Ramp
down Time and 3-72 Ramp 4 Ramp Down Time .
The precise stop function is set up here and enabled from
DI T29 or T33.
NOTE!
This parameter cannot be adjusted while the motor is
running.
3 3
3-23