What it is and where it fits
The Siemens 3RK1300-0KS01-0AA0 is a direct starter in the SIRIUS family, built as a compact motor-starting block that handles switching and overload protection in one enclosure. It's rated for 0.37 kW at AC-3 duty (1.3 A at 400 V), so it's sized for small three-phase motors — pumps, fans, conveyors — where you don't need a separate contactor and overload relay. The IP65 housing means it can live out on the machine frame or in a washdown zone without a secondary cabinet, as long as the gland plate is properly sealed. Communication runs over PROFIBUS DP via the backplane bus, so it drops into a distributed I/O or motor-starter island without point-to-point control wiring. The control supply is 24 V DC (20.4...28.8 V range), and the main circuit is three-pole, rated 400...500 V. Short-circuit protection is built in via circuit-breakers, not fuses — that saves a fuse holder and makes resetting a fault a button-push instead of a parts run.
Mounting and integration
The unit measures 270 mm high, 140 mm wide, and 134 mm deep — that's a tall, narrow footprint, typical for a motor-starter block with integrated bus coupler. It mounts on a DIN rail or directly to a backplane bus rail for power and communication. The supply voltage comes through the backplane bus, so you don't have to ring separate 24 V DC wires to each starter — just daisy-chain the bus rail. For the main energy infeed and load-side outgoing feeder, it uses sockets per ISO 23570, which is a standardized industrial connector pattern; you'll need the matching plug set.