Transwarp coil

From Memory Alpha, the free Star Trek reference

A transwarp coil was a propulsion device which allowed Borg vessels to generate a transwarp conduit. (VOY: "Dark Frontier")

To generate a transwarp conduit the coil required a minimum input of 30 teradynes (300 meganewtons) of force from the ship's systems. On Borg vessels, the coils were protected by a protocol that damaged the coil beyond repair by fusing the field regulator when the vessel became critically damaged. (VOY: "Dark Frontier")

In 2153, two scientists discovered a transwarp coil from the wreck of a Borg sphere that crashed in Earth's Arctic Circle. (ENT: "Regeneration")

In mid-2375, after surviving a battle with a Borg probe, the crew of the USS Voyager managed to recover several Borg data nodes containing, among other information, long-range sensor telemetry and vessel movements for a radius of thirty light years. Utilizing this information, Voyager was able to locate a damaged Borg sphere and steal a working transwarp coil from the ship's transwarp chamber. The coil was fitted to both the Delta Flyer and Voyager itself, providing 20,000 light years of travel before giving out, shaving approximately fifteen years off Voyager's journey home. (VOY: "Dark Frontier")

It is unknown whether the transwarp coil burned out because it was connected to Voyager's ship systems or whether this was a regular occurrence. It is also unknown why Borg vessels carried several coils. When the Borg sphere turned on all of them on at once to generate a conduit, it suggests that they are intended to be used in parallel rather than individually to share the load.

Transwarp
aperture • chamber • coil • computer • conduit • corridor • drive • factor • hub • network • probe • signal • signature • space • threshold