Fig.1 Design improvement of conventional stator coil insulation (thermal barrier) and increase of generator power density

Design improvement of conventional stator coil insulation (thermal barrier) and increase of generator power density

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In recent years, the customer prefers an increase in capacity of indirect—cooled generators due to the advantages of simple structure, short production lead-time, high reliability and low maintenance cost.

While coil insulation is required to provide appropriate dielectric characteristics that are maintained throughout the life of generators, the conventional stator coil insulation acts as a thermal barrier due to extremely low thermal conductivity as shown in Fig.1 (a).

In meeting the market needs mentioned above, 10 to 20% increase in power density of indirect hydrogen-cooled turbo generator by the application of increased thermal conducting stator coil insulation (twice of conventional one) and optimized ventilation system was fixed as a design target, refer to Fig.1 (b).

Several evaluation tests to find the most suitable type of inorganic filler and development of high thermal conducting mica tape that is applicable to existing stator coil production processes and facilities were completed to realize the design target. And the world’s first high thermal conducting stator coil insulation system was successfully established while maintaining almost the same dielectric stress and temperature rise to those of conventional design with the same frame size. (1), (2), (3)

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