What This Part Is — and What It Does in a Panel
The Siemens 3RH1122-1BM40-0AA6 is a SIRIUS auxiliary contactor in the Size S00 frame — a compact, 45 mm wide switching block meant to mirror or extend the auxiliary contact set of a main contactor or starter. It carries 2 normally-open and 2 normally-closed instantaneous contacts, rated for 10 A in AC-12 duty, which is the resistive / low-inductive load curve typical of PLC inputs, signal lamps, and small relay coils. The screw and snap-on mounting means it clips directly onto a DIN rail alongside the main power contactor without additional hardware. The contactor's thermal and surge ratings are worth noting for the commissioning engineer: it's rated for surge voltage resistance of 6 kV, pollution degree 3 (conductive pollution typical of control panels), and an IP20 front — so it's protected against finger contact but not washdown. The operating temperature range of -25 to +60 °C covers most indoor panel environments, with storage and transport tolerance down to -55 °C and up to +80 °C.
Mechanical Endurance and Shock — The Reliability Angle
Mechanical endurance is listed at 30 million operating cycles — typical for a contactor of this class, meaning it outlasts the main contactor it's paired with in most cyclic applications like conveyor or pump control. Shock resistance of 10g / 5 ms and 5g / 10 ms means it holds contact closure under moderate vibration environments; it's not a mil-spec part, but it's adequate for industrial machinery bolted to a concrete floor. The mounting position allows +/-180° rotation on a vertical surface and +/-22.5° tilt forward/backward, giving the panel builder some flexibility in tight enclosures.
Terminal Capacity and Wiring Reality
The screw terminals accept 2x (0.5... 1.5 mm²), 2x (0.75... 2.5 mm²), or 2x 4 mm² solid conductor — so you can land two smaller wires per terminal for daisy-chaining or parallel feeds. That's a practical detail for the wireman: it avoids needing a separate terminal block for distributing the control supply to multiple auxiliary contactors. The closing and holding power of the magnet coil at DC is 3.2 W — a low enough draw that a 24 VDC power supply can drive several of these without derating the supply's output.