Large 60 Hz turbogenerators: Mechanical design and improvements

Abstract

In order to follow the market demands for the power generation industry, turbogenerator designs for today's applications must be cost effective, highly reliable and highly efficient. To meet these challenges, Alstom introduced the first GIGATOP 2-pole and 4-pole turbogenerators 40 years ago, for fossil-fueled plants and nuclear power plants, applications in 50 Hz and 60 Hz markets. Since then, these turbogenerators have been continuously developed by Alstom. The GIGATOP turbogenerator has specific design features such as direct water-cooled stator bars with stainless-steel cooling tubes, to achieve high reliability and efficiency. In this paper, technology improvements of GIGATOP turbogenerators are presented, with the focus on mechanical design. Best industrial practice, in terms of tools and methodologies, are applied to ensure a smooth development process and improvements of the GIGATOP design towards further increases in performances, while maintaining and enhancing the outstanding levels of quality and reliability.

Improvement of the transient negative-sequence rating formula for large generators based on the negative-sequence current component

“…Taking the phase fault condition as an example, the time result equals to 22.5 s based on the traditional formula. However, the time result is in the range of 13.46-22.5 s according to the improved formula, Formulas (6) and (7). The result calculated using the improved transient negative-sequence calculation formula is in stark contrast to the result of the traditional formula.…”

“…Considering the design parameters, the result is t = 22.5 s using the traditional Formula (1). The calculations are repeated when the initial phase angle is 0°, 30°and 60°, and the time results equal 13.46, 15.72 and 20.24 s, respectively, using the improved Formula (7). The relationships between A and time are shown in Figure 8.…”

“…Reference [6] presents the dynamic analysis of eddy currents and losses of a synchronous generator and a new calculation method based on a lumped circuitry. The test results of eddy current distribution, loss distribution and resulting temperature distribution are calculated and compared in [7][8][9][10][11][12]. At present, the finite element method is often used to calculate the negative-sequence losses and rotor heating.…”

Direct liquid cooling for an outer‐rotor direct‐drive permanent‐magnet synchronous generator for wind farm applications

“…The reliability of the primary and the secondary cooling loops depends on auxiliary component reliabilities, which are connected in series and parallel for water filters (15). Table 6 summarises the literature values of the failure rates and MDT for the auxiliary equipment and the cooling system tubes [40,42,43,[46][47][48][49][50].…”

Negative-sequence Component Analysis of an AP1000 Nuclear Turbo-generator in an Internal Short-circuit Condition

“…Negative-sequence current will be produced by asymmetric operation in the generator short-circuit fault, causing the eddy current loss of the rotor surface to increase due to the skin effect. Rotor negative-sequence heating in the development of the large-capacity turbo-generator is a critical issue that must be further investigated and resolved [4][5][6][7][8][9][10][11][12][13]. Hence, the analysis of a negative-sequence component for an AP1000 nuclear large-capacity turbo-generator is of great importance to generator operation, motor design, and manufacturing processes.…”