Plasma coil
From Memory Alpha, the free Star Trek reference
A plasma coil is a component of a starship's engines.
The D-12 class Klingon Bird-of-Prey was retired from service as its plasma coils were defective. (Star Trek Generations)
While visiting Deep Space 9 in 2369, Geordi La Forge was interested in purchasing a 21st century Ktarian plasma coil that he found in a shop on the Promenade in near perfect condition. (TNG: "Birthright, Part I")
Loose plasma coils create large amounts of radiation. A Bajoran transport docking at Deep Space 9 in 2372 had a loose plasma coil, preventing the station from beaming off wounded passengers. (DS9: "Life Support")
Plasma coils are also highly deadly, as an overload often causes computer consoles on the bridge to explode in a shower of sparks, sometimes killing crewmembers.Fluctuations in the plasma coils can cause a power surge in the warp core. When this occurs, the ship is typically required to take the core offline. (DS9: "Our Man Bashir")
