The Siemens 3UG4621-1AA30 is a SIRIUS current monitoring relay with digital setting and an LCD display, designed to monitor AC or DC current in a 0.003 to 0.5 A range (measurable up to 0.6 A). It snaps onto a standard DIN rail (22.5 mm width) and operates on a 24 V AC/DC control supply (20.4–26.4 V at 50/60 Hz). The relay provides one changeover contact rated 3 A at 250 V or 400 V AC, and lower ratings for DC loads (1 A at 24 V, 0.2 A at 125 V, 0.1 A at 250 V).
The 0.003–0.5 A sensing range covers small motor loads, heater circuits, or pump monitoring where you need to detect undercurrent (belt slip, dry running) or overcurrent (jammed rotor). The adjustable start-up delay (0.1–20 s) lets you ride through inrush without nuisance tripping — set it longer for high-inertia loads. Auto-reset and external reset options give flexibility for unattended restart or manual lockout after a fault. IP20 protection means it's for dry indoor panels only — no washdown, no dust.
Accepts two conductors per terminal — solid or stranded 20–14 AWG (0.5–2.5 mm²). The 22.5 mm width means it takes one standard module slot; plan for 91 mm depth behind the panel. Terminal screws are captive, and the LCD gives local readout of actual current and trip settings.