A flux generator was a piece of technology used on some space stations and starships.
In 2370, Gideon Seyetik worked on Deep Space 9's flux generator. He managed to increase the generator's output by at least five percent. (DS9 episode: "Second Sight")
Later that year, following a battle with rogue Klingon Birds-of-Prey, the USS Regal's flux generators were damaged. (DS9 novel: Antimatter)