What the 0.8 ... 1.1 at 50 Hz rating means for fit
The 3RT5945-5AB01: The at 50 Hz value of 0.8... 1.1 represents the operating voltage range as a factor of the rated control supply voltage — in this case 24 V AC. That means the coil reliably picks up and holds across 19.2 V to 26.4 V AC at 50 Hz. Below 0.8 pu (19.2 V) the armature may chatter or fail to seal; above 1.1 pu (26.4 V) you risk overheating the winding. For a panel builder verifying control transformer sizing, this range tells you the coil tolerates a sagging bus during inrush from other loads, but it's not a wide-margin part — keep the control voltage within 24 V ±10% for reliable operation.
The coil terminates via screw terminals — no push-in or spring-cage option on this variant. Strip length for the stranded or solid control wire should follow the contactor's terminal specification (typically 8–10 mm for the screw clamp). The coil draws its rated inrush and holding VA from the control transformer; verify the transformer can supply the peak inrush without dropping below the 0.8 pu threshold. Mounted on the contactor, the coil adds no additional DIN-rail space — it's the same footprint as the base contactor.