GE Industrial Solutions AF-650 GP General Purpose Drive Programming Guide - Manual (Page 70)

H-80 Function at Stop
Option: Function:
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 F-24 Holding Time to the
desired pre-mag time (2 to 4 rotor
time constants - see below).
2b. Set F-25 Start Function to either
[0] DC-hold or [1] DC-Brake.
Set the DC-hold or DC-brake
current magnitude (B-00 DC Hold
Current or B-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
U0
When the motor is stopped, the H-55 U/f
Characteristic - U [0] parameter defines the
voltage at 0 Hz.
[5] Coast at low
reference
When the reference is below H-81 Min Speed
for Function at Stop [RPM], the motor is
disconnected from the frequency converter.
[6] Motor check,
alarm
H-81 Min Speed for Function at Stop [RPM]
Range: Function:
3 RPM * [0 - 600 RPM] Set the speed at which to activate
H-80 Function at Stop.
H-82 Min Speed for Function at Stop [Hz]
Range: Function:
0.1 Hz * [0 - 20.0 Hz] Set the output frequency at which to
activate H-80 Function at Stop.
H-83 Precise Stop Function
Option: Function:
NOTE
This parameter cannot be adjusted while
the motor is running.
[0]
*
Precise
ramp
stop
Only optimal when the operational speed - of
e.g. the conveyor belt - is constant. This is an
H-83 Precise Stop Function
Option: Function:
open loop control. Achieves high repetitive
precision at the stopping point.
[1] Cnt stop
with reset
Counts the number of pulses, typically from an
encoder and generates a stop signal after a pre-
programmed number of pulses - H-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 decel to 0
RPM is reset.
[2] Cnt stop
w/o reset
Same as [1] but the number of pulses counted
during decel to 0 rpm is deducted from the
counter value entered in H-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
comp
stop
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 F-03 Max Output
Frequency 1).
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
stop w/rst
Same as [3] but after each precise stop the
number of pulses counted during decel to 0
rpm is reset.
[5] Comp cnt
stop w/o
r
Same as [3] but the number of pulses counted
during decel to 0 rpm is deducted from the
counter value entered in H-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
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
Parameter Descriptions AF-650 GP Programming Guide
DET-618C 69
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