Siemens sinumerik 840D sl Function Manual page 371

Energy balance
When configuring emergency retraction, it is always necessary to establish an energy
balance to find out whether an additional capacitor module or a generator axis/spindle (with
correspondingly dimensioned centrifugal mass) is required.
Stopping as energy supply
Changes to rotational speed setpoints of the projected shutdown or retraction axes/spindles
follow after about the third interpolation act. After this time the braking phase starts (if no
drive independent shutdown is projected for this axis).
As soon as the braking process is initiated, the energy released in this manner is available
for retraction motion. An energy balance must be used to ensure that the kinetic energy of
the braking axes is sufficient for retraction.
The energy balance shows the maximum setting for the interpolator cycle time, which will
allow a safe emergency retraction to be executed.
Example:
With a 16 kW unit under maximum load and minimum intermediate circuit capacity it should
be possible to execute an emergency retraction without generator operation. Interpolation
cycle time may theoretically not be more than 4,86 ms, i.e. in this case a maximum of 4 ms
could be set.
If necessary, a more powerful NC-CPU must be chosen, in order to achieve optimal
conditions.
Drive independent stop/retract
Drive independent stop and retract triggered by the NC is used when a very fast reaction is
required. In this case, the drive reacts within one interpolator cycle and outputs a setpoint
value for the configured axes/spindles.
Note
A POWER ON must be performed following drive independent stop and retract.
When the drive bus is interrupted between NC and drive (sign-of-life failure) a stop and
retract can only be initiated by the drive. This case normally does not occur simultaneously
with a power failure.
Special functions: Axis Couplings and ESR (M3)
Function Manual, 11/2006, 6FC5397-2BP10-2BA0
Detailed description
2.7 Extended stop and retract (ESR)
151