Sunday, November 16, 2008

Brush Electric Generator

The Brush Generator is an electric generator which converts rotational shaft horsepower into electrical energy. Rated output is 50 MW under ideal conditions, when driven by an LM6000 gas turbine producing approximately 55,000 shp. The generator is installed in an isolated pressurized enclosure to prevent explosive gas leakage from the engine into the generator compartment, where possible ignition could occur. It also provides enclosed filtered air cooling.

The unit is bolted to the gas turbine-generator package skid, such that the rotor is axially aligned with the engine drive shaft. The stator core is built into a fabricated steel frame and consists of a low-loss silicon, steel-segmented stampings insulated by a layer of varnish on both sides. The stampings are divided into short sections radial ventilating ducts extending from the center through to the outer ends. The stator windings are arranged in patterns to minimize circulating currents.

The rotor is machined from a single alloy-steel forging of tested metallurgical properties. Longitudinal slots are machined radially in the body in which the rotor windings are installed. The windings are secured against centrifugal force by steel wedges fitted into the dovetail opening machined in the rotor slots. The coils are insulated from the slot walls by molded slot liners. Molded ring insulation is provided at the coil ends to separate and support the coils under thermal and rotational stresses. A centering ring held into place shrink fit restricts axial movement.

The exciter assembly consists of a permanent magnet alternator (PMA), an exciter stator and rotor, and a rotating diode rectifier. These components are installed at the non-drive end of the generator shaft.

The permanent magnet stator consists of a single-phase winding in a laminated core. Twelve permanent magnets rotate on the rotor inside the stator to produce aproximately 125 VAC at 50 Hz. The PMA output voltage is rectified and regulated by the modular automatic voltage regulator.