Siemens sinumerik 840D sl Function Manual page 366

Detailed description
2.7 Extended stop and retract (ESR)
When the value falls below the intermediate circuit voltage lower limit, the axis/spindle
concerned switches from position or speed-controlled operation to generator operation. By
braking the drive (default speed setpoint = 0), regenerative feedback to the DC link takes
place. The drive measures the intermediate circuit voltage cyclically (in the position control
cycle). If the voltage rises above the value specified in the following axis machine data, the
dual controller is switched off, i.e. the current rotational speed actual value is set as setpoint
for rotational speed:
MD1631 $MD_LINK_VOLTAGE_GEN_ON
and
MD1632 $MD_LINK_VOLTAGE_GEN_HYST
During active generator operation, bit 3 "DC link generator active" is output in system
variable $AA_ESR_STAT.
The two-step behavior of the generator is machine and user-specific.
If the voltage rises above the value specified in the following machine data, generator
operation is discarded and control reverts to rotational speed control:
MD1633 $MD_LINK_VOLTAGE_GEN_OFF
This is not the case if the axis/spindle was previously in position-controlled mode. In this
case, it is necessary to reset the drive (POWER ON).
Monitoring the generator speed minimum limit
In addition to generator operation to back up the intermediate circuit, the actual speed value
of the axis/spindle in generator operation is monitored for any speeds lower than the
parameterizable minimum speed set in the following axis machine data:
MD1635 $MD_GEN_AXIS_MIN_SPEED
When values below this speed limit are detected, bit 4 "Generator speed < MD1635" is
output in system variable $AA_ESR_STAT.
In addition this signal can also be defined as error source for the ESR, similar to recognition
of a voltage drop in the intermediate circuit (MD1634 $MD_LINK_VOLTAGE_RETRACT).
2.7.11 Drive-independent stopping
The drives of a previously coupled grouping can be stopped by means of time-controlled
cutout delay with minimum deviations from each other, if this cannot be performed by the
control.
Drive independent shutdown is configured via the following machine data, released with
system variable $AA_ESR_ENABLE and started after the delay time T1 (see below) with
system variable $AN_ESR_TRIGGER:
MD37500 $MA_ESR_REACTION=12
T1 is specified in the following axis machine data:
MD1637 $MD_GEN_STOP_DELAY
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Special functions: Axis Couplings and ESR (M3)
Function Manual, 11/2006, 6FC5397-2BP10-2BA0