The Siemens 3RW4036-2BB05 is a SIRIUS soft starter rated 45 A at 40 °C, which means it handles a standard 22 kW motor on 400 V three-phase without derating. That 45 A figure is the full-load current it can ramp up; the integrated bypass contact system takes over at speed, so the thyristors only handle the start transient — no continuous heat dissipation in the power stack during run. The 24 V AC/DC control voltage is the standard PLC-level signal, so it drops straight into a 24 VDC control cabinet without an interposing relay. Derating is straightforward: 42 A at 50 °C, 39 A at 60 °C. The minimum load of 20 % means it won't regulate properly below about 9 A — fine for a 22 kW motor, but not for a fractional-horsepower pump.
Mounts via screw and snap-on to a DIN rail — Size S2 means it takes a 55 mm wide footprint, 160 mm tall, 170 mm deep. That depth includes the thyristor heat sink, so check your enclosure depth before laying out the backplane. Required clearances: 60 mm upward, 40 mm downward, 30 mm at the sides for airflow and wiring access. With an additional fan, the mounting surface can be vertical and rotated ±90° or tilted ±22.5°; without a fan, rotation and tilt are limited to ±10°. Main circuit terminals are screw-type, accepting 2x (1.5... 25 mm²) stranded or 2x (0.25... 2.5 mm²) solid. Auxiliary contact terminals accept 2x (24... 14) AWG. The front clamping point takes 18... 2 AWG, the back clamping point 16... 2 AWG. Using both clamping points on the same conductor accepts 16... 2 AWG. Maximum motor cable length is 300 m — beyond that, capacitive charging current may cause nuisance tripping on the overload protection. The adjustable current limitation lets you set the start current between roughly 2x and 5x FLA, depending on the load. An external reset input allows remote fault clearing. The red fault signal display gives a local visual indication.