What it is and what it does
The Siemens SIRIUS 3RP1540-2AJ31 is a single-function time relay with an adjustable ON-delay from 0.05 to 600 s, meant to delay the closing of its output contacts after the control supply is applied. It's a straightforward part for timing a start, sequencing a motor, or staggering loads in a panel — no star-delta, no pulse-shaping, just a reliable delayed closure. The control supply is rated for 100–127 V AC at 50/60 Hz and the same range for DC, so it works on common 110–120 V control transformers or DC supplies without separate coils. The relay output switches resistive loads up to 5 A thermal, with specific contact ratings: 1 A at 24 V, 0.2 A at 125 V, and 0.1 A at 250 V — fine for signaling a PLC input or a contactor coil, not for direct motor switching.
Mounting and integration
It snaps onto a 35 mm DIN rail (screw and snap-on mounting) and occupies 22.5 mm of width — one standard module. The 91 mm depth and 84 mm height are typical for this SIRIUS form factor; it fits alongside other 22.5 mm-wide control components in a panel. Mounting position is any, so no orientation constraints inside the enclosure.