Siemens 6SN1123-1AA00-0DA2 Configuration Manual page 309

8 Important Circuit Information
8.13 Operation when the power fails
8-308
The ready signal via terminals 72–74 in the NE module also responds when a
line supply fault occurs and inhibits the pulses in the NE module. The response
time is, among other things, dependant on the line supply impedances and
other quantities and can therefore not be precisely calculated in advance. Gen-
erally, the power failure detection time is >30 ms and is alone not sufficient to
initiate functions for operation when the power fails (line supply failure).
Operation when the power fails with the SIMODRIVE 611 universal HRS
Example:
The DC link voltage is monitored using the limit value stage of a 611 universal
HRS control board in the SIMODRIVE 611 universal HRS. When a selectable
limit value is undershot, e.g. a DC link voltage of 550 V, the limit value stage
responds and switches a positive output signal from +24 V to 0 V via a digital
output stage. For example, terminal 64 – drive enable – can be inhibited in an
"AND" logic operation with the relay contact of the ready signal of terminals
72–73.1 of the NE module. The drives are braked and stopped as quickly as
possible at the current limit.
In addition, for example, via a second digital output of the 611 universal module,
the setpoint polarity of a drive can be changed–over and retraction motion initi-
ated for a drive before the other remaining drives are braked, delayed via termi-
nal 64.
The safety–relevant circuit examples in Section 8.7 for the drive control must be
appropriately adapted by the user for operation when the power fails (line sup-
ply fault).
Additional possibilities for braking when the power fails:
Braking using armature short–circuit braking for permanent–magnet servomo-
tors, refer to circuit example =8 in Section 8.7.
Note
The power failure monitoring device must directly interrupt the coil circuit of the
armature short–circuit contactor as a buffered +24 V power supply will either
respond too late or not even respond at all.
Braking by quickly applying the holding brake, bypassing the PLC cycle time,
refer to circuit example =8 in Section 8.7.
Note
The holding brake is not an operating brake and can only be conditionally used
for such braking operations.
SIMODRIVE 611 Configuration Manual (PJU) – 02/2012 Edition
© Siemens AG 2012 All Rights Reserved
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