SIRIUS S2 power contactor — 24 VDC coil, screw terminals
The Siemens 3RT1035-3BB40-ZN88 is a SIRIUS-brand power contactor in the S2 frame size, designed for switching motor loads in industrial control panels. It carries a 24 VDC coil and uses screw-type terminals for the main current circuit. Rated at 22 kW at 500 V in AC-3 duty (the standard motor-switching category per IEC 60947-4-1), it handles the locked-rotor inrush of a 3-phase induction motor up to that power. At 690 V the AC-3 rating drops to 11.4 kW, reflecting the higher voltage stress on the arc chutes. For heavier-duty switching, the AC-4 rating at 400 V is 35 A — that's the category for plugging and inching, where the contactor makes and breaks stalled-rotor current repeatedly. The 24 VDC coil draws a holding current that keeps the magnet sealed down to about 18 V; dropout happens below that threshold. Pickup and dropout delay runs 20 to 25 ms, with an arcing time of 10 to 15 ms — fast enough for most sequence interlocks.
Mounting and panel integration
Mounts on 35 mm DIN rail per EN 50022, using either the snap-on latch or screws. The 55 mm width and 112 mm height fit standard S2 contactor spacing; side-by-side mounting is permitted without derating, which keeps the row tight in a multi-contactor bank. Depth is 130 mm — enough clearance for the arc chamber and the screw-terminal wiring. The front face carries IP20 protection (finger-safe), while the terminal area is IP00 (open for wiring). Pollution degree 3 means it's rated for industrial environments with conductive dust or condensation.
Terminal capacity and wiring
Main power terminals accept stranded wire from 0.75 mm² up to 25 mm² (two conductors per clamp), or solid wire from 0.25 mm² up to 2.5 mm². At 40 °C ambient, the minimum permissible cross-section is 16 mm² — that's the thermal sizing floor for full rated current.
Environmental range and compliance
Operates from -25 °C to +60 °C, stores from -55 °C to +80 °C. The storage range exceeds the operating range because it governs shipping and idle storage, not running conditions.