Danfoss VLT AutomationDrive FC 300 Series Programming Manual page 46

Parameter Descriptions
1-80 Function at Stop
Option: Function:
[1] DC hold Energizes 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-magnetizing function does not help the
very first start command. Two different
solutions are available to pre-magnetize 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 seconds
10 kW = 0.5 seconds
100 kW = 1.7 seconds
1000 kW = 2.5 seconds
[4] DC Voltage When the motor is stopped, the P1-55 [0]
U0 parameter defines the voltage at 0Hz.
[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:
Size related [0.0 - 20.0 Hz] Set the output frequency at which
*
to activate 1-80 Function at Stop.
®
VLT AutomationDrive Programmming Guide
Function:
®
MG33ME02 - VLT is a registered Danfoss trademark
1-83 Precise Stop Function
FC 302 only.
Option: Function:
[0] Precise Only optimal when the operational speed - of
ramp stop e.g. the conveyor belt - is constant. This is 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 impacts of
gradual wear of 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
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. Please
therefore make sure that the frequency
converter 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 impacts of
gradual wear of 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
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