Dc Link Buffering - Siemens Simodrive 611 Configuration Manual

8 Important Circuit Information
8.13 Operation when the power fails
8.13.3

DC link buffering

Energy balance
8-310
The following control and secondary conditions/limitations must be care-
fully taken into consideration when engineering and configuring power
failure concepts:
S
The braking energy must be converted into heat using one or more pulsed
resistor module(s) – or for unregulated infeed units, using the internal pulsed
resistor (it may be necessary to use, in addition, an external resistor). When
the drives brake, the DC link voltage may not fall below or exceed the max.
set monitoring thresholds.
S
The safety–relevant hardware control must, when the power fails, e.g. briefly
maintain the enable signals via terminals 48, 63, 64, NS1, NS2 and 663.
Further, the internal axis–specific enable signals of the NC/PLC interface via
the digital drive bus must also be maintained until the drives come to a
standstill.
S
For controlled retraction motion, holding brakes must remain energized, if
required, until the operation has been completed and clamping operations
must be released.
S
The external +24 V power supply for the control voltage must be buffered
using power supply units, e.g. SITOP power with capacitor or battery
back–up. This maintains the drive enable signals, the PLC functions, and
the control and machine functions on the user side.
S
During the braking and retraction phase, it is not permissible that the NC and
PLC controls generate fault signals that inhibit the drives.
S
The power supply of the SINUMERIK 840 D with the integrated PLC–CPU is
supplied through the DC link of the NE module when the power fails.
The energy stored in the DC link of the drive units can be used when the power
fails. Capacitor modules are used to increase the DC link capacitance. This
means that on one hand, a brief power failure can be buffered and on the other
hand, it is also possible to store the braking energy.
Note
Examples to calculate and select a capacitor module, refer to Chapter 6.7.1.
When configuring the emergency retraction, it is always necessary to consider
the energy flow (balance) to find out whether you can do without an additional
capacitor module or a generator axis/spindle (with correspondingly dimensioned
flywheel effect).
SIMODRIVE 611 Configuration Manual (PJU) – 02/2012 Edition
© Siemens AG 2012 All Rights Reserved
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