Optimizing the refurbishment process of old 44 MVA hydro generator: a study on alternating winding type and vibrational behavior

Date

2024-12-30

Author

Yakut, Muhammet Samet

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Refurbishing hydro generators extends their lifespan and improves their efficiency. Aging machines often experience reduced reliability, lower efficiency, and frequent breakdowns, leading to significant economic challenges. The primary goals of refurbishment are to enhance cooling systems, upgrade materials, and improve performance. Modifying the winding configuration, although rare, can offer substantial benefits but often requires changes to the slot number, adding complexity to the redesign. Adjusting the slot number affects the slots per pole per phase ratio, which can significantly alter the machine’s vibration characteristics. This study focuses on the refurbishment of a 68–year–old hydro generator, originally built by Westinghouse Electric Corporation in 1956 and equipped with lap windings. The proposed refurbishment replaces the lap windings with Roebel bars, necessitating a change in the slot number. Three alternative designs–270, 300, and 324 slots—-are evaluated, with one derived through multi-objective optimization, others through analytical design approach. While all designs achieve similar efficiencies of 98.1–98.3%, their vibration characteristics differ due to low–order spatial force harmonics caused by fractional slot windings. The 270 slot design exhibits dangerous vibration levels due to a 6th spatial harmonic close to the power frequency (100 Hz), raising mechanical stability concerns. The 300–slot design, however, offers the best balance between electromagnetic performance and vibration stability, making it the most viable option. This study provides valuable guideline for hydro generator designers by demonstrating the importance of addressing both electromagnetic and vibrational performance in refurbishment projects.

Subject Keywords

Hydro generator, Refurbishment, Rewinding, Vibration

URI

https://hdl.handle.net/11511/113050

Collections

Graduate School of Natural and Applied Sciences, Thesis