The LX4FH055 is a replacement contactor coil from the TeSys range, designed for 55 V DC control circuits. It's the part that pulls the contactor in and holds it closed — without it, the main power contacts don't move. Rated for DC wide-range control, the coil operates between 0.85 and 1.1 times Uc (about 47 to 60.5 V DC) at 55 °C, and drops out between 0.15 and 0.2 Uc (roughly 8.25 to 11 V DC). That dropout margin means the contactor releases reliably on a sagging DC bus — important for undervoltage protection schemes. Closing time is 40 to 50 ms; opening takes 40 to 65 ms. Those are the mechanical travel times — the arc extinction on the main poles adds its own window, but this is the coil's contribution to the overall switching sequence.
Coil resistance and suppressor note
At 68 °F (20 °C), the inrush resistance is 4.37 Ω and the holding resistance is 994.1 Ω. The big jump between inrush and holding is normal for a DC coil — the initial surge pulls the armature in, then the holding current drops to a fraction of that. If you're sizing a DC supply, the inrush current (about 12.6 A at 55 V) is the peak load, not the steady-state draw. This coil ships without a built-in suppressor module. On a DC circuit, that means you need an external flyback diode or a varistor across the coil terminals — otherwise the inductive kick when the coil de-energises can damage the PLC output or relay driving it. Standard practice: a 1N4007 diode (or equivalent) cathode to positive, anode to negative, placed as close to the coil as wiring allows.
The LX4FH055 is a service-part coil for TeSys contactors that accept the FH-series coil assembly. It's not a standalone component — it mounts onto the contactor's magnet system, replacing the original coil if it fails or if the control voltage needs changing.