What this direct starter does on the line
The Siemens 3RK1300-1CS01-0AA0 is a direct starter — a self-contained motor-starting and overload-protection package for three-phase induction motors up to 0.9 kW at 400 V AC-3 duty. The AC-3 rating of 2.5 A tells you it's sized for switching motors under full load, not resistive heaters; the bimetal overload release is field-adjustable from 1.8 to 2.5 A, so you set the trip point to match the motor nameplate FLA. The 3-pole main circuit connects via tab terminals, and the control supply is 24 V DC (20.4 to 28.8 V range).
Integration into a PROFIBUS DP cell
This starter communicates over PROFIBUS DP via the backplane bus — no AS-Interface or PROFINET onboard. The bus connection and supply voltage both route through the backplane, so the unit snaps onto a mounting rail and the bus coupler handles addressing. The IP65 enclosure means it can sit directly on the machine frame in a washdown zone, not just inside a sealed cabinet. Dimensions are 134 mm deep, 140 mm wide, 270 mm tall — factor that into your gland-plate layout if you're routing the ISO23570 socket for main energy infeed and load-side outgoing feeder.
Short-circuit protection coordination
The starter includes short-circuit protection via circuit-breakers (not fuses). This matters for selectivity studies: the upstream protective device must coordinate with the 2.5 A AC-3 rating to avoid nuisance tripping on motor start.