The Siemens SIRIUS 3RT2926-3AF31 is a mechanical latch designed to hold S0-size contactors (3RT202, 3RT232, 3RT252) in the closed position after the control signal drops — a common requirement for latching circuits in conveyor interlocks or emergency-off reset sequences. It accepts a 110 V AC/DC control supply, so one part covers both line and DC control buses without a separate coil change. The screw-type terminals take 2x 0.5…2.5 mm² solid or 1x 4 mm², matching standard panel wiring practice.
Clip-on fastening snaps directly onto the contactor's front — no tools needed for initial fit, but verify the latch engages fully before energizing. The 22 mm width and 48.4 mm height keep it inside the S0 envelope; the 84.3 mm depth adds about 10 mm beyond the contactor body, so check gland-plate clearance if the panel is tightly packed.
Electrical characteristics
Coil power loss runs 4 W typical at DC and 4 VA typical at AC. The 4 kV surge voltage rating means the latch can handle switching transients on a 300 V insulation system without flashover.