What it is and what it does
The Siemens 3RK1300-0KS01-1AA1 is an electromechanical reversing starter from the SIRIUS series, designed for motor control in distributed automation environments. It integrates a reversing contactor, motor protection via a bimetal overload relay, and a PROFIBUS DP communication interface into a single IP65-rated enclosure — meaning it can be mounted directly on the machine or in a field junction box without a separate control cabinet. The 0.37 kW rating at AC-3 duty (400 V) covers small three-phase motors typical of conveyor drives, valve actuators, or pump stations. The setting range of 0.9 to 1.25 A on the bimetal relay matches the full-load current of a 0.37 kW motor at 400 V, so the overload protection is factory-scaled to the motor size.
Key ratings and what they mean for fit
The AC-3 rating of 0.37 kW at 400 V is the motor-switching capability under starting and stopping conditions (inrush up to 8× FLC). The 50 A short-circuit breaking capacity (Icu) at 400 V means the integrated circuit-breaker coordination can clear a fault up to that level without upstream devices needing to trip — critical for selectivity in a distributed panel where a single feeder supplies multiple starters. The operating voltage range of 400 to 500 V AC covers standard European 400 V three-phase networks and 480 V North American systems. The IP65 rating protects against dust ingress and low-pressure water jets, so the unit can be deployed in washdown areas or outdoors without an additional enclosure.
Communication and brake control
PROFIBUS DP onboard allows the starter to be addressed directly from a PLC or DCS, eliminating the need for a separate remote I/O module for start/stop and direction commands. The integrated motor brake output supplies DC 24 V / 3 A for an externally supplied brake — common on vertical-axis drives or holding-brake motors. This means the brake is controlled synchronously with the motor contactor, so the brake releases before the motor starts and engages after it stops, without a separate timing relay.