Yasuo Kabata

Circulating Currents in Stator Coils of Large Turbine Generators and Loss Reduction

Stator coils transposed by 540deg are widely used as one of the solutions to reduce the circulating current loss in the coil strands of turbine generators. However, the difference of the leakage fluxes in the two coil end parts, which is possibly caused by the coil end length deviation, the winding pitch, and the presence of the connection rings, may induce unbalanced voltage in the stator coil strands, which increase circulating current loss even in the transposition coils. This paper describes the mechanism and the analysis results of the circulating current increase in the coil strands due to the coil end flux difference. Then, some new schemes to reduce the circulating current loss are proposed and discussed.

Air-cooled large turbine generator with multiple-pitched ventilation ducts

On the air-cooled turbine generators, windage loss is the substantial factor of generator losses. One solution for the windage loss reduction is to minimize the amount of coolant air with the multiple-pitched ventilation ducts in the stator core. However, non-uniform duct distribution leads to the circulating currents in the stator bar strands which increase coil losses and cause significant distribution of strand loss. This paper presents circulating currents due to multiple-pitched ventilation ducts and some schemes to reduce the circulating current loss, such as new transposition systems of coil strand

Development of world's largest hydrogen-cooled turbine generator

Simple generator systems are preferred for thermal power generation because of their better operability and maintainability, and their lower cost. Hydrogen-cooled generators of up to 600 MVA have been developed to meet these customer requirements. Development of this generator was achieved mainly by optimization of the cooling gas flow distribution and high thermal conducting insulation of the stator winding. A 500 MVA turbine generator applying these key technologies has been designed and manufactured, and has shown satisfactory results in a shop test.

Development of blade for floating type current turbine system

The KUROSHIO is one of the ocean currents flowing stably near the coast of Japan throughout the year, and power generation technology using this ocean current energy is now attracting attention in Japan due to its potential as a clean and stable energy source. Slow current velocity and deep water depth are technical challenges of the current turbine system in the KUROSHIO Current. The authors have been engaged in the research and development of a floating type current turbine system moored on the seabed and floating on the sea. This system consists of large twin-turbines and simple mooring for deep-sea deployment as shown in Fig. 1, and it is expected to operate with a high capacity factor. This paper discussed about the turbine output characteristics by turbine blades which were confirmed through CFD (Computational Fluid Dynamics) analysis, towing tank test and the impact of turbine blade deformation which was measured by towing tank test, obliquely inflow and cross-beam.

Development of the world's largest hydrogen indirectly cooled turbine generator

Water-cooled stator-winding generators are widely used for large capacity turbine generators of thermal power plant. However, simpler stator cooling system is preferred considering easy operation and maintenance and lower cost. Hydrogen indirectly cooled generator is one of the solution with expansion its capacity. TOSHIBA has developed, manufactured and tested 670MVA hydrogen indirectly cooled generator.