The Siemens 3RT1036-3BB40-ZN88 is a SIRIUS power contactor in size S2, built for switching motor loads in control panels. Its 24 VDC coil pulls in reliably; the rated operating current at AC-3 duty reaches 30 kW at 500 V, which covers a standard 37 kW 4-pole induction motor on a 400 V line. The contactor mounts on a 35 mm DIN rail per EN 50022, using either the integrated snap-on clips or screws for a fixed install.
Ratings and what they mean for fit
The AC-3 rating of 30 kW at 500 V is the headline figure for motor switching — it tells you the contactor can handle the inrush and breaking current of a three-phase squirrel-cage motor up to that power. At 690 V the same duty drops to 11.4 kW, so if your line runs 690 V you need to check the motor nameplate against that lower ceiling. For resistive loads (AC-1) the mechanical life of 10 million operations is the limiting factor, not the electrical endurance. The 24 VDC coil draws 10 A at rated voltage; the dropout threshold sits below 18 V. If your control transformer is marginal on regulation, factor in the 20 to 25 ms closing time and 10 to 15 ms arcing time when coordinating with upstream fuses or a motor-protective breaker. Pollution degree 3 means the contactor is rated for industrial environments where conductive pollution occurs — the standard for most factory-floor panels. The IP20 front keeps fingers out; the terminal area is IP00, so panel builders need to respect the clearance to live parts inside the enclosure.
Mounting and wiring
The contactor accepts screw-type terminals on the main circuit. Solid wire from 0.25 to 2.5 mm² and stranded from 0.75 to 25 mm² — that covers most motor feeder cables up to 6 mm² for a 30 kW load. Side-by-side mounting is allowed, which saves rail space in a multi-contactor group, but remember the thermal derating if you pack them tight at the upper end of the operating range (-25 to +60 °C,).