The Siemens SIRIUS 3RW4427-1BC44 is a soft starter — thyristor-switched, with an integrated bypass contact system that takes the thyristors out of the circuit once the motor is at full speed, reducing heat dissipation in the panel. Rated 161 A at 40 °C, it handles motor starts up to that current in standard industrial environments; derate to 142 A at 50 °C and 125 A at 60 °C if your enclosure runs hot.
The 8 % minimum load spec means it won't regulate smoothly below that threshold; if your motor draws less than about 13 A, this starter will struggle to control the ramp. Mounting flexibility: vertical surface, rotatable ±90°, tiltable ±22.5° front-to-back. That covers most panel layouts, but the screw-fixing method means you're drilling or using a mounting plate — no DIN-rail snap-on here.
The thyristor stack and bypass contactor are one assembly, so swap time is the same as any similarly sized soft starter — expect to land it against an RFQ.
Integration notes
Dimensions: 170 mm wide, 192 mm high, 270 mm deep. Clearance: 100 mm above, 75 mm below, 5 mm at the sides — that 5 mm side gap is tight; plan for at least 10 mm if you're running larger cables. Main circuit terminals are box terminals accepting 2x (4... 50 mm²) stranded or 2x (10... 1/0) AWG using both clamping points. Auxiliary and control circuit terminals are screw-type, 2x (0.5... 2.5 mm²) solid. Wire length max 500 m — fine for most motor runs, but check if your motor is more than 500 m from the starter. Motor overload protection and intrinsic device protection are built in. Adjustable current limitation is standard, and the external reset input means you can wire a remote reset button into the control circuit.