What it is and where it lands
The Siemens 3VA9987-0TA10 is a SENTRON COM800 breaker data server — an accessory that sits in the fixed switchboard (IP20 per IEC 60529) and pulls data from up to eight 3VA circuit breakers over the internal communication bus, then serves it upstream via PROFIBUS DP, PROFINET IO, or Modbus RTU. It's the bridge between the breaker compartment and the plant network, sized at 90 mm wide, 90 mm high, and 33.5 mm deep — five modular width units on the DIN rail. Mounting position is any. The RJ45 Fast Ethernet interface runs at 100 Mbit/s with auto-MDI(X) and a serial gateway for legacy fieldbus drops.
What the ratings mean for fit
It directly connects eight 3VA breakers — that's the practical limit per COM800. If your switchboard has more than eight breakers to monitor, you add a second server on the same 20 m communication bus. The bus termination connectors (two included) must be fitted at the physical ends of the daisy chain. Power consumption is 5 W, drawing 1.1 A max. The supply is screw-terminal, removable/pluggable. Operating temperature spans -40 °C to 80 °C. Overvoltage category I and pollution degree 2 mean it's designed for clean, protected environments inside the enclosure — not for direct line-side exposure. Protection class III per IEC 61558 confirms it runs on SELV/PELV.