Siemens SINUMERIK 840C - Manual (Page 991)

12 Functional Descriptions 10.94
12.20.4 Mains buffering and mains failure detection 611A/D
12.20.4 Mains failure detection and mains buffering
12.20.4.1 Mains failure detection
Mains failures can be detected by means of the infeed/regenerative feedback (I/RF) module
when the 611 A/D drive system is used. By using terminal 73 on the I/RF module, it is possible
to utilize the mains monitoring function of the connected actuator as an external source (e.g.
by connecting terminal 73 to the mixed I/O or the CSB).
Under worst-case conditions, mains failure detection takes approximately 120 ms and, in the
best case, only 15 ms.
12.20.4.2 DC link overvoltage limitation (611D)
The DC link is monitored for the following voltage states (see diagram).
Voltage level for DC link in 611D
DC link voltage
600V 625 V
Pulse suppression, DC link
Pulse suppression, drives
710V
695V
648V
618V
743V
723V
676V
644V
Pulsed resistor module
operating range
The diagram shows that the pulses of the drives and the DC link are suppressed when the
voltage reaches certain levels. Pulse suppression automatically causes the drives to coast to a
standstill.
If this pulse suppression reaction is not desired, then the user can destroy any excess energy
by using a resistor module. This module operates in the shaded range shown in the diagram
and thus below the critical voltage level.
It must however be ensured that the pulse output of the resistor module is greater than the
I/R output.
12.20.4.3 Mains buffering (611D only)
It is possible to compensate brief dips in the DC link voltage through configuration of drive
machine data and appropriate programming by means of G commands. The possible buffering
period depends on the level of energy stored by the generator used to back up the DC link
and on the amount of energy required to maintain the motions currently being executed
(DC link buffering and monitoring of generator minimum speed limit).
12–216 © Siemens AG 1992 All Rights Reserved 6FC5197- AA50
SINUMERIK 840C (IA)