page_title: West Burton power stations
section_title: Generator
hierarchical_section_title: West Burton power stations / Description / Generator
caption_attribution_description: English: EDF welcome, West Burton Power Station
context_page_description: The West Burton power stations are a pair of power stations on the River Trent near Gainsborough, Lincolnshire, England. One is a coal-fired power station, which was commissioned in 1967, and the second is a combined cycle gas turbine power station, commissioned in 2013. Both stations are owned and operated by EDF Energy. The station has been accredited as an Investor in People since 1995 and ISO accredited for its environmental management system since 1996. The power station won a RoSPA President's Award in 2006, 2007 and 2008. The site is the furthest north of what was a series of power stations in the Trent valley, being 3.5 miles downstream of the now-closed Cottam power stations. The power station is one of three coal-fired generators left in England.
context_section_description: Each of the four generators is designed for an output of 500 MW at 0.85 power factor with a terminal voltage of 22 kV. Hydrogen at a pressure of 60 psig, is employed for cooling the stator core and rotor conductors, the gas being in direct contact with the rotor conductors, and water is used for cooling the stator conductors. Hydrogen coolers are arranged longitudinally in the upper part of the stator frame and the hydrogen is circulated by an axial flow blower mounted on the turbine end of the rotor shaft. The stator is of two-part construction, the core and windings being assembled in a skeleton inner
  frame threaded into the outer stator frame at site. The weight of the heaviest part, the inner stator, is 194 tons.
  The generator stator winding is water cooled at 2.155 m³/min (474 gal/min) and the stator core and rotor winding are cooled by hydrogen at 60 psig circulated by a blower on the shaft. To reduce the transport weight, each stator consists of an outer gas tight enclosure, which carries the hydrogen coolers and the end brackets which support the rotor bearings, and an inner stator comprising the magnetic core and windings.
  The stator core is built with laminations of cold rolled grain-oriented sheet steel 0.013 in (0.033 cm) thick, insulated from each other with insuline. The number of segments per circle is arranged so that the maximum practical percentage of core flux is in the direction of the oriented grain. The rings of lamination's are built into a skeleton frame which is flexibly supported inside the main stator frame to prevent double-frequency vibrations being transmitted to the foundations. Axial gas passages are provided within the core by holes punched in the lamination's, which line up throughout its length. The ends of the core are divided axially by spacers into a number of radial ducts. These ducts form the gas inlet and outlet passages for the axial gas passages. Separate radial ducts feed the extreme ends of the core with cold gas to cater for the increased heating experienced at the core ends during leading power factor operation. Each coil side of the stator winding consists of rectangular copper tubes, each tube being insulated with resin-impregnated glass braid, and the tubes are transposed within the coil length by the Roebel method to minimise stray copper losses. Inlet and outlet manifolds are arranged at opposite ends of the windings and all coil sides are fed in parallel from these. The water connections between the manifolds and coil sides are made with flexible hoses of insulating material. The electrical connections between coil sides consist of flexible copper straps, bolted and sweated to contact blocks which are brazed to the conductor tubes near to the end of each coil side. The rings used to connect up the phase groups to the terminals are also water cooled, the flow through these being in parallel with the flow through the coil sides.
  Direct hydrogen cooling is employed in the stator terminals. The rotor forging is of nickel chromium molybdenum vanadium steel having a minimum yield point of 33.2 ton/in.2. The shaft end which connects to the turbine is deferentially tempered to give additional strength to withstand the severe forces which could be applied under fault conditions on the generator. The first three critical speeds are arranged to be below the running speed. The hydrogen-cooled rotor conductors are formed from silver-bearing hard drawn copper tube. Two tubes in parallel form one conductor and there are six conductors per slot except for the slots adjacent to the pole centres, which contain five. The generator is ventilated by cold gas fed to a number of radial ducts at the slipring end of the core, which communicate with the axial vent holes in the core and stator teeth. After passing through the axial holes the gas is discharged into the ‘air’ gap through further radial ducts at the turbine end of the core. The gas discharged from the core passes along the ‘air’ gap, together with the hot gas discharged from the outlet holes in the rotor body, to the region between
caption: EDF branding in 2009
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