The Siemens 3UG4513-1BR20 is a SIRIUS network monitoring relay with analog setting, purpose-built for phase monitoring on AC supplies. It watches for phase loss, phase sequence, and asymmetry across a 160-690 V AC range at 50 or 60 Hz, and throws its output contacts when the line goes sour. Rated contact current is 3 A at both 250 V and 400 V (50/60 Hz), which covers most control-signal switching inside a panel — think contactor coils, PLC inputs, or alarm annunciators. The auxiliary contacts are rated for 24 V at 1 A, 125 V at 0.2 A, and 250 V at 0.1 A, so match your load to the right voltage tap. Asymmetry detection is built in, and the relay offers a delayed switching function with a configurable initial value and full-scale value — useful for riding through momentary sags without nuisance tripping. Auto-reset is available, so the relay can re-close once the line clears.
Snap-on mounting to a 35 mm DIN rail — 22.5 mm wide, 92 mm tall, 91 mm deep. Pollution degree 3, meaning it handles conductive dust and occasional condensation in industrial cabinets. That makes it easy to pack into a crowded DIN rail without worrying about heat buildup from adjacent devices.