Danfoss VLT AutomationDrive FC 301 Programming Manual page 49

Parameter Descriptions
1-80 Function at Stop
Option: Function:
[0] Coast Leaves motor in free mode. The motor is
disconnected from the frequency converter.
*
[1] DC hold Energises motor with a DC holding current
(see 2-00 DC Hold Current).
[2] Motor check Checks if a motor has been connected.
[3] Pre- Builds up a magnetic field while the motor
magnetizing is stopped. This allows the motor to
produce torque quickly at subsequent start
commands (asynchronous motors only). This
pre-magnetising function does not help the
very first start command. 2 different
solutions are available to pre-magnetise the
machine for the first start command:
1. Start the frequency converter
with a 0 RPM reference and wait 2
to 4 rotor time constants (see
below) before increasing the speed
reference.
2a. Set 1-71 Start Delay to the
desired pre-mag time (2 to 4 rotor
time constants - see below).
2b. Set 1-72 Start Function to either
[0] DC-hold or [1] DC-Brake.
Set the DC-hold or DC-brake
current magnitude (2-00 DC Hold
Current or 2-01 DC Brake Current) to
be equal to I_pre-mag = Unom/
(1.73 x Xh)
Sample rotor time constants =
(Xh+X2)/(6.3*Freq_nom*Rr)
1 kW = 0.2 s
10 kW = 0.5 s
100 kW = 1.7 s
1000 kW = 2.5 s
[4] DC Voltage When the motor is stopped, the 1-55 U/f
U0 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 Set the speed at which to activate
*
RPM] 1-80 Function at Stop.
®
VLT AutomationDrive FC 301/302 Programming Guide
1-82 Min Speed for Function at Stop [Hz]
Range:
Size related
1-83 Precise Stop Function
Option:
[0] Precise
ramp
*
stop
[1] Cnt stop
with
reset
[2] Cnt stop
w/o reset
[3] Speed
comp
stop
[4] Com cnt
stop
w/rst
[5] Comp
cnt stop
w/o r
MG33MH02 - Rev. 2013-09-30
Function:
[ 0 - 20.0 Set the output frequency at which
*
Hz] to activate 1-80 Function at Stop.
Function:
NOTICE
This parameter cannot be adjusted
while the motor is running.
FC 302 only.
Only optimal when the operational speed - of
e.g. the conveyor belt - is constant. This is an
open loop control. Achieves high repetitive
precision at the stopping point.
Counts the number of pulses, typically from an
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.
Same as [1] but the number of pulses counted
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 impacts of
gradual wear of mechanical parts.
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 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 1-84 Precise Stop
Counter Value.
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