What this part is and where it fits
The Siemens SIRIUS 3RT1026-1BB40-ZW95 is a size S0 power contactor with a 24 V DC coil, screw-type main terminals, and a 45 mm wide body that snaps onto a 35 mm DIN rail per EN 50022. It's rated for motor switching up to 11 kW in AC-3 duty at both 500 V and 690 V, and handles 15.5 A in AC-4 (reversing or inching) at 400 V. For resistive loads (AC-12), it carries 10 A continuously. The front face is IP20 protected; the terminals themselves are IP00, so keep the panel enclosure sealed against debris.
What the ratings mean for your panel
The AC-3 rating of 11 kW at 690 V tells you this contactor handles standard squirrel-cage motors up to that power — starting and stopping under load, no inching. The AC-4 rating of 15.5 A at 400 V is the one to watch if your application does plugging or jogging; that's the harder duty cycle. Pollution degree 3 means it's rated for industrial environments where conductive dust or condensation can occur — typical for an unsealed control cabinet. The 24 V DC coil draws 5.4 W closing and 5.4 W holding, so it's a continuous-duty solenoid; no power savings on hold. For type 2 coordination (no damage to the contactor on a short circuit), Siemens specifies a 35 A gL/gG fuse upstream; for type 1 (allow replacement after fault), a 100 A fuse is acceptable.
Mounting and wiring notes
Mounts via screw or snap-on onto 35 mm DIN rail per EN 50022. The main circuit screw terminals accept 2x (0.5 to 1.5 mm²) solid, 2x (0.75 to 2.5 mm²) solid, or max 2x (0.75 to 4 mm²) — that's the fine-wire range. For stranded, they take 2x (1 to 2.5 mm²) or max 2x 10 mm². AWG equivalents: 2x (16 to 12) solid, 2x (14 to 10) stranded, or 1x 8. Side-by-side mounting is allowed with 6 mm spacing to adjacent devices — no derating required for heat buildup in a standard cabinet. Ambient operating range is -25 °C to +60 °C, which covers most indoor industrial panels.