Graviton field generator

A graviton field generator, or simply graviton generator, was a piece of equipment utilized in such technologies as tractor beams, shields, and warp drives.

In 2368, the USS Enterprise (NCC-1701-D) arrived at a unique nebula which had formed around a neutron star in order to investigate the phenomenon. Upon entering the nebula, the Enterprise came under attack by a series of energy-based lifeforms which began to drain energy from the Enterprise's graviton field generators, gradually reducing the power of the ship's shields. Captain Picard was able to make contact with one of the aliens, who had taken the form of a little girl, and convince her of the crew's peaceful intentions. Before departing, Captain Picard ordered Commander La Forge to drive the warp engines to full power and direct a flow of energy into the nebula, supplying the aliens with sustenance. 

The same year, a Romulan science vessel suffered a forced chamber explosion in their resonator coil, causing their graviton field generator to depolarize. This threatened a warp core breach, but the crew of the Enterprise, which had answered a distress call from the Romulan vessel, was able to assist the Romulan crew in ejecting the core moments before the explosion. 

A year later, a team of Klaestron law enforcement agents attempted to abduct Jadzia Dax from Deep Space 9, in accordance with a warrant for her arrest. In an attempt to anticipate any actions which could be taken by the crew to stop their escape, they disabled the station's tractor beam, resulting in a residual charge in the graviton generator. As the agents attempted to forcibly remove Dax from the station, Captain Sisko worked to speed up the bleed-off process in the generator in an attempt to bring the tractor beam online. His efforts proved successful, and, upon increasing the flow to the EPS waveguides, the excess charge was neutralized, allowing them to use the tractor beam to prevent the Klaestron vessel from escaping.