What this part is and where it fits
The Siemens 3RH1140-1BG40 is a SIRIUS auxiliary contactor in the size S00 frame — the compact footprint that mates directly with S00 power contactors on a DIN rail. It carries 4 instantaneous normally-open contacts, rated for a 125 V DC coil. The 45 mm width and 72 mm depth match the standard S00 contactor envelope, so it clips onto the same rail alongside the main contactor without extra panel space. This is the auxiliary block you add when the main contactor runs out of N.O. aux contacts — or when you need a separate control-circuit isolation path. The coil draws 3.2 W DC both on pick-up and hold, so the control transformer sizing is straightforward: no inrush spike to budget for.
Contact ratings and what they mean for the load
The contacts are rated for switching at several common control voltages: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, 2 A at 500 V, and 1 A at 690 V. These are thermal current ratings for the auxiliary contacts — they govern the continuous current the contacts can carry, not the motor load. For a typical 24 V DC PLC output driving a solenoid or indicator, 10 A is generous headroom. At 230 V AC control circuits, 6 A covers most pilot-duty loads. Surge voltage resistance is rated at 6 kV, which means the contactor can withstand transient overvoltages common in industrial panels without flashover. Pollution degree 3 (conductive pollution or dry non-conductive pollution that becomes conductive due to condensation) is the standard for control cabinets not sealed from the factory floor.
Mechanical endurance and mounting flexibility
Typical mechanical life is 30 million switching operations. Contact reliability is specified as one incorrect switching operation per 100 million at 17 V and 1 mA — that low-level switching capability matters when the auxiliary contacts are used to read dry-contact status inputs from sensors or limit switches. Mounting position is flexible: the contactor can be rotated ±180° on a vertical surface and tilted forward or backward by ±22.5°. This helps when the panel layout forces an unconventional orientation — the contacts still operate reliably. Shock resistance is 10g for 5 ms and 5g for 10 ms, covering most industrial vibration environments short of direct hammer strikes.
Wiring and termination
Terminals accept solid conductors: 2x 0.5–1.5 mm², 2x 0.75–2.5 mm², or 2x 4 mm². That covers standard control wiring from 18 AWG to 12 AWG. The screw-clamp terminals are the same type used on S00 contactors, so the same screwdriver and torque setting apply across the panel.
Environmental and compliance
Operating temperature range is -25 to +60 °C; storage and transport range is -55 to +80 °C. IP20 protection on the front means the terminals are finger-safe but the contactor is intended for installation inside a locked or tool-accessible enclosure. RoHS compliance date is 2006-07-01, covering the EU RoHS directive.