Siemens SIMODRIVE 611 Planning Manual page 294

9 Important Circuit Information
9.12 Operation at power failure
9
9-294
The ready signal via terminals 72–74 in the NE module also responds when a
line supply fault develops and inhibits the pulses in the NE module. The re-
sponse time is, among other things, dependent on the line impedances and
other quantities and therefore cannot be precisely calculated. Generally, the line
supply failure detection time is >30ms and is therefore not sufficient to initiate
functions for operation when the power fails.
Operation at power failure with the SIMODRIVE 611 universal drive
Example:
The DC link voltage is monitored in the SIMODRIVE 611 universal group via
the limit value stage of a 611 universal control module. When a selectable limit
value is fallen below, e.g. 550 V DC link voltage, 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 along
the current limit.
In addition, e.g. via a second digital output of the 611 universal module, the set-
point polarity of a drive can be changed over and the drive retracted before the
other drives are then braked, delayed using terminal 64.
The safety–related circuit examples in Section 9.7 for the open–loop drive con-
trol must be appropriately adapted on the user–side for operation at power fai-
lure.
Additional possibilities of braking when the power fails:
Braking via the armature short–circuit braking for permanent–magnet servo mo-
tors, refer to the circuit example =9 in Section 9.7.
Note
The power failure monitoring device must directly disconnect the coil circuit of
the armature short–circuit contactor, as a buffered +24 V power supply either
responds too late or not at all.
Braking by quickly applying the holding brake, bypassing the PLC cycle time,
refer to circuit example =9 in Section 9.7.
Note
The holding brake is not an operating brake and can therefore only be used for
such braking operations to a limit extend.
 Siemens AG 2001 All rights reserved
SIMODRIVE 611 Planning Guide (PJU) – 05.01 Edition
05.01