The 3RT1924-5AB01 is a SIRIUS magnet coil for Size S0 contactors, rated 24V AC at 50Hz with screw terminals. It's the replaceable coil assembly that pulls in and holds the contactor's main and auxiliary contacts — the part that fails when a coil burns out or the control voltage changes. This coil is specific to the Size S0 frame, which covers the 3RT2 contactor family. The screw-terminal version means it terminates the control wiring directly under screw clamps — no spring-cage or ring-tongue adapters needed.
The preferred successor is the 3RT2924-5AB01. If you're filling a BOM line or a panel spare, that's the direct drop-in replacement from Siemens — same Size S0 frame, same 24V AC 50Hz coil voltage, same screw-terminal pattern. No rewiring or mounting mods needed. If you're building a new panel, spec the 3RT2924-5AB01 and avoid a future obsolescence headache.
The at 50 Hz value of 0.8... 1.1 is the power factor range of the coil — the ratio of real power to apparent power drawn during pickup and hold. At pickup the coil pulls harder (lower power factor, more VA), then settles to a higher power factor for holding. This matters for control transformer sizing: a 24V AC control circuit feeding several of these coils needs to handle the inrush VA, not just the steady-state VA. The 24V AC control supply voltage is line-frequency, not DC or 60Hz. If your panel runs 24V DC or 60Hz control power, this coil won't pull in reliably — you'd need the DC-rated or 60Hz variant in the same Size S0 frame.