The LX9FF550 is a specific replacement coil for TeSys F contactors, rated for 550 V AC control circuits at 40-400 Hz. It's a low-consumption design — inrush power sits at 690-855 VA, dropping to 6.6-8.1 VA holding — which means the control transformer and wiring only need to handle the brief surge, not a continuous high draw. The coil draws 331.4 Ω inrush and 12447 Ω holding at 68 °F (20 °C).
Opening time is 130 ms and closing time is 35 ms — the asymmetry matters in sequencing: the contactor opens slower than it closes, so if you're interlocking with another device, the break-before-make window is driven by the opening delay. The coil has no built-in suppressor module, so you'll need to add an external RC snubber or varistor across the coil terminals to protect the control circuit from the inductive kick during dropout. Control voltage limits are 0.85-1.1 Uc for operation and 0.35-0.55 Uc for dropout at 131 °F (55 °C). That dropout range is wide — the coil releases at roughly 193-303 V on a 550 V nominal supply — so it won't drop out on a moderate sag, but a hard brownout below 193 V will release the contactor. Heat dissipation is 5.9-7.2 W, which adds to the panel thermal load; in a sealed enclosure, factor that into the cooling budget. That's about 40 cycles per minute continuous — fine for most motor starting and switching duty, but if you're cycling faster than that (e.g., in a rapid-indexing application), you'll exceed the mechanical rating.
Deployment Context
This coil mounts directly onto the TeSys F contactor frame — it's a specific replacement, not a universal fit. Because it's a low-consumption coil, it pairs well with PLC-sourced control signals through an interposing relay, keeping the PLC output contact loading low.