Integrator's note on the 3RT1026-1BD44
The Siemens 3RT1026-1BD44 is a SIRIUS power contactor in the S0 frame, sized for motor switching up to 11 kW at 400 V in AC-2 duty (slip-ring motors, wound-rotor applications) and rated 15.5 A in AC-4 duty for reversing or inching service. The DC coil draws 5.4 W for both pick-up and hold, so there is no inrush spike to size the control transformer around. Mounts via screw and snap-on onto 35 mm DIN rail per EN 50022; the 45 mm width leaves room for adjacent devices in a crowded panel, and side-by-side mounting is permitted without derating gaps.
Coordination and protection
For type 2 coordination (no damage to the contactor under short circuit), the required upstream fuse is gL/gG 35 A. For type 1 coordination (contactor may need replacement after fault), a 100 A gL/gG fuse is permitted. The contactor carries a pollution degree 3 rating, meaning it is suited for industrial environments with conductive pollution or dry non-conductive pollution that becomes conductive due to condensation. Ambient operating range is -25 to +60 °C, with the altitude limit at 2 000 m — no derating needed for most plant-floor conditions.
Termination and wiring
Main current circuit terminals are screw-type, accepting 2x (1 to 2.5 mm²) stranded or 2x (2.5 to 6 mm²) solid, with a maximum of 2x 10 mm² per clamp. Auxiliary contact terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²), max 2x (0.75 to 4 mm²). AWG equivalents are 2x (16 to 12) and 2x (14 to 10) for main contacts. The front face is IP20 (finger-safe), while the terminal area is IP00 — maintain clearance around live parts per local wiring regulations.