Siemens SINUMERIK 840D sl Function Manual page 471

Table 9-1 SINAMICS infeeds (ALMs): Nominal and minimum buffer times
ALM Max. capacitance
C
P [kW]
max
max
16 20000
36 20000
55 20000
80 20000
120 20000
Energy balance
When configuring retraction motion, it is always necessary to consider the energy flow
(balance) to find out whether an additional capacitor module or a generator axis (with
correspondingly dimensioned flywheel effect) is required - or not.
Stopping as energy supply
From approx. the third interpolator clock cycle, the speed setpoints of the configured stopping
or retraction axes change. 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 clock 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. Interpolator clock
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 NCU must be chosen in order to achieve optimal conditions.
Generator operation
For cases in which the DC link energy is not sufficient for safe and reliable retraction (minimum
3 IPO cycles), generator operation can be configured for a drive using the SINAMICS "Vdc
control" function. In this case, the mechanical energy of an axis is fed back into the DC link.
The energy stored in an axis can be calculated as follows:
This energy is fed back into the DC link with an efficiency of approx. 90%:
Special functions
Function Manual, 01/2015, 6FC5397-2BP40-5BA2
Energy content
[μF] E for C
max max
1800
1800
1800
1800
1800
E = 1/2 * J * ω
2
tot
J Total moment of inertia [kg*m
tot
ω Angular velocity at the time of switchover to generator operation [s
Energy content E
min
[Ws] for C [Ws]
min
1440
1440
1440
1440
1440
]
2
R3: Extended stop and retract
9.2 Control-managed ESR - 840D sl only
Backup time t Buffer time t
Pmax
for P [ms]
max
101,25
45,00
29,46
20,25
13,50
for
Pmin
P [ms]
max
81,00
36,00
23,56
16,20
10,80
]
-1
471