3VL molded-case circuit breaker
4.2 COM20 connection
3WL/3VL circuit breakers with communication capability - PROFIBUS
System Manual, 03/2011, A5E01051353-02
97
Figure 4-4
Addressing plug (3UF7910-0AA00-0)
4.2.3
COM20 pin assignment
The COM20 must be supplied with 24 V DC for operations and this must be applied to the
terminals A2 (ground) and A1 (+). This voltage is looped-through via the communication
cable to the ETU (trip unit) of the 3VL switch such that this is also operated when the main
contacts are open. Without this supply the ETU would not be able to communicate
diagnostics information, such as the reason for the last tripping operation if there is no
internal supply.
The auxiliary and alarm switches are not wired to COM20, but direct to the ETU, and the
communication status is forwarded to COM20.
The figure below shows the principle of the connection between the COM20 and a
SENTRON VL including the LEDs and the PROFIBUS write protection DPWriteEnable.