Siemens Simatic S7-1500 CPU 1512C-1 PN User Manual page 100

Wiring
4.3 Terminal and block diagrams
The figure below shows the current flow when the ground connections of the loads and the
ground connection of terminal 30 are routed with a common cable to the central terminal
block.
①
Ground connections of other plant parts that can also carry large currents.
Figure 4-20 Faulty wiring using the digital on-board I/O X11 as an example: Common cable
If a break occurs in the common cable, the current of the outputs flows via terminal 30 to the
module and via terminal 40 to the central terminal block. The current flows via the module.
Current flow with faulty wiring
If a break occurs in the common cable, the current can be very high, depending on the
plant, and lead to the destruction of the module.
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WARNING
CPU 1512C-1 PN (6ES7512-1CK01-0AB0)
Manual, 12/2017, A5E40898741-AA