What it is and where it fits
The Siemens 3RT1017-2BB42 is a SIRIUS power contactor in the compact S00 frame size, designed for switching motor loads in control panels. It's built for screw and snap-on mounting onto a 35 mm DIN rail per EN 50022, so it integrates cleanly into a standard panel layout. The 24 VDC coil draws 3.3 W during both closing and holding, which is a steady-state load you can budget for in your 24 VDC supply — no inrush spike to size around. Spring-loaded terminals on both the main and auxiliary/control circuits accept 2x (0.25 to 2.5 mm²) solid or stranded wire, or 2x (24 to 14 AWG). That means no screw torque checks during commissioning — strip, insert, and the cage holds.
What the ratings mean for your motor load
Rated 5.5 kW at 400 V in AC-2 duty (slip-ring motor starting), this contactor handles the moderate inrush and longer acceleration of wound-rotor motors. The same 5.5 kW rating holds at 500 V and 690 V, so it's consistent across common industrial voltages. In AC-4 duty (plugging, inching, reversing), the rated operational current is 8.5 A at 400 V. That's the figure to use for frequent jogging or reversing applications — the AC-3 or AC-1 numbers aren't the limiting factor here. For type of coordination 2 (short-circuit protection with minimal damage to the contactor), Siemens specifies a gL/gG fuse of 20 A. For type 1 coordination (contactor replacement after fault), a 35 A fuse is allowed. This guides your upstream protective device selection.
Environmental and compliance notes
Rated for ambient operation from -25 to +60 °C, with a pollution degree of 3 (conductive pollution or dry non-conductive pollution that becomes conductive due to condensation). That suits most industrial control cabinets without derating for typical factory floor conditions. IP20 on the front and at the terminals — finger-safe but not washdown-rated. Mount inside an enclosure if the environment sees dust or moisture. The reference code per IEC 81346-2 is Q (power switching device), which aligns with standard panel documentation practices.