A new 400 MVA air cooled turbogenerator from Ansaldo Energia

摘要

The continuous and constant trend to increase the gas turbine output above 300 MW, forces the turbogenerator designers and manufacturers to enlarge the applicable range of the air cooled turbogenerators as a valid and competitive alternative to the hydrogen cooled types. The air cooling range extension, rather than the use of hydrogen cooled ones, gives some significant savings considering the whole life cycle of the machines. These savings are mainly the results of: 1. safety requirements not conditioned by hydrogen presence; 2. absence of hydrogen, carbon dioxide and seal oil plants; 3. simplified interfaces, operation, control and maintenance needs; 4. reduced in erection, pre-operation and start-up duration time. The new 400 MVA air cooled turbogenerator size cover both gas and steam turbine applications at 3000 r.p.m. and 50 Hz; the design has been based on large experience of 360 MVA size air cooled generator: in the last decade about thirty units of this type have been manufactured and installed in Italy and abroad. The upgrade mainly depends on increased dimensions in order to maintain the same ratio power output / volume of the active parts, but also by optimization of ventilation and heat exchange efficiency; the cooling is indirect type for stator winding and direct type for core, stator winding connections terminal side, and rotor winding. The class F stator winding insulation system is resin rich single bar type, a proven solution used by Ansaldo for both air and hydrogen cooled generators even for higher voltage levels and electro-dynamic forces. The rotor-dynamic design assures suitable tuning possibility to adapt the generator for different prime movers. Increase of dimensions and masses involves also check for transportation limitations, particular attention has been dedicated to this aspect. For this aim a specific and detailed design has been developed in all direction especially in the mechanical and structural discipline with the aid of the most recent and sophisticate calculation facilities and codes.