What it is and where it fits
The Siemens 3RT2327-2BM40 is a SIRIUS contactor in size S0, designed for DC coil operation with spring-type terminals. It snaps onto a 35 mm DIN rail per DIN EN 60715, making it a direct fit for standard industrial control panels. The DC coil means this contactor is suited for applications where the control voltage is DC, common in battery-backed systems or PLC-driven outputs. The spring-type terminals on the magnet coil reduce wiring time and eliminate the risk of screw-terminal loosening under vibration.
Key ratings and what they mean for your circuit
The main contact current ratings are given per voltage for DC switching: 10 A at 24 V, 6 A at 60 V, 3 A at 400 V, and 1 A at 690 V. These are the DC-1 or DC-3 type loads; the 10 A at 24 V rating is the one that governs most control-circuit applications, while the 3 A at 400 V matters for small DC motor or brake loads in a 400 VDC bus. The contactor carries an auxiliary switch, which is critical for feedback to a PLC or for interlocking in a reversing starter. The arcing time is 10 to 10 ms, giving a predictable break interval for coordination with upstream fuses or breakers.
Mounting and clearances
The contactor measures 60 mm wide, 102 mm high, and 107 mm deep. For thermal management and arc clearance, maintain 10 mm clearance upwards, forwards, and downwards, and 6 mm at the sides. The mounting position allows +/-180° rotation on a vertical surface and +/-22.5° tilt — useful when fitting into a tight or angled sub-panel.
Wiring and terminal capacity
The spring-type terminals accept solid conductors from 2x (0.5 to 2.5 mm²) and stranded conductors from 1 to 10 mm². This range covers most control wiring up to 10 mm² for power circuits, and the dual solid termination allows daisy-chaining of control wires without a separate terminal block.