Mitsubishi Electric verifies VP-X high-efficiency turbine generator; first 900-MVA-class generator with indirect H2 cooling; 99% efficiency

8 December 2014

Mitsubishi Electric Corporation has successfully completed verification tests on its VP-X turbine generator for thermal power plants—the first generator in the 900-MVA class to use indirect hydrogen cooling for stator conductors. (Hydrogen is used extensively in power generation to cool turbine generators because of its low density and good thermal characteristics.)

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Cooling is achieved with hydrogen gas introduced from outside of the main insulation. Due to this and other proprietary technologies, the VP-X achieves an extra-high efficiency rating of 99%, placing it in the world’s highest class of turbine generators that offer highly sustainable operation. A series of VP-X generators will be launched commercially in April 2015.

Lineup of two-pole turbine generators. Source: Mitsubishi Electric. Click to enlarge.

Mitsubishi Electric enhanced cooling performance in the VP-X by improving main insulation and cooling gas ventilation without incorporating a water-cooling system for the stator winding. Until now, all large-capacity turbine generators in the 900 MVA class have relied on water-cooling.

Mitsubishi Electric’s VP-X features a simplified design that will help improve the appearance of power plants, as well as lower the requirements for maintaining and operating turbine generators. The overall size is 20% smaller than conventional indirectly hydrogen-cooled generators. In addition, both the footprint and frame diameter are smaller, making transportation easier.

Elimination of a water-cooling system for the stator winding helps to simplify maintenance. Also, needs for manual inspection have been reduced through a partial discharge monitoring system that incorporates a microstrip antenna for continuous monitoring of the main insulation and an inspection robot.

In addition, a new parallel-manufacturing method for the stator core and stator frame shortens delivery time.

The VP-X turbine generator received a 2014 Good Design Award from the Japan Institute of Design Promotion, making this the first large electrical machine for power systems to be so honored.

Mitsubishi Electric has shipped more than 2,000 turbine generators worldwide since 1908.