The ABB ZA185-84 is a replacement coil for the A-Line series of across-the-line contactors, specifically the A145 through A185 and A145N4 frames. It's rated for 110-120V at 60Hz — a standard control voltage for North American panel builds. The coil itself is the part that fails when a contactor chatters or drops out under load; swapping it is often the fix before replacing the whole contactor.
The coil mounts directly onto the contactor's magnet stack — no panel rework needed if you're swapping into an existing A145/A185 installation. Verify the coil voltage matches your control transformer tap before energizing; a 120V coil pulled down to 110V still holds, but below 100V it'll drop out and buzz. The 60Hz rating means it's for line-frequency control, not DC or variable-frequency coil drives.