Toru Otaka

Eddy current analysis in the stator end structures of large capacity turbine generators

In the stator core end region of the large capacity turbine generators, the leakage magnetic flux induces eddy current loss in the metal structures. In this paper, the results of three-dimensional electromagnetic field analyses of the stator end structures are described. It is demonstrated that the eddy current loss dependency on the power factor can be explained with the phasor diagrams on the magnetic flux. Then the relationship between the end structure and the current source is discussed.

A Study on Rotor Surface Losses in Small-to-Medium Cylindrical Synchronous Machine

This paper presents a new method for estimation of rotor surface losses in small-to-medium capacity synchronous machines. In this study, the authors have proposed a method for estimating the slot ripple losses induced on the rotor surface. Also, we compared the damper systems using the finite-element method and verified the results by the measured data.

Comparison of Brush Dynamic Operation Characterisitics for Turbine Generator Steel Collector Ring

In large turbine generators for thermal or nuclear power plants, such as 1000 MVA power plants, brush & collector ring sliding contact operation characteristics, where more than 5000 A field exciting current flows, are one of the most important problem for its reliability. In case of turbine generator collector ring, ring material is usually made of steel, as a view point of mechanical strength for high speed operation, such as 60 m/s, where brush contact characteristics for the steel ring have not been well known or have not been enough disclosed. Besides collector ring profile distortion which may cause brush seating operation difficulties, has to be allowed to some extent, due to mechanical structure of the turbine generator rotor & machining process feature. These mean that the suitable carbon brush grades for this purpose are limited, even though hundreds of carbon brush grades are supplied all over the world by brush manufacturers. In this paper, results of the carbon brush grades comparison test for evaluating dynamic operation characteristics by applying very high sliding speed condition & very high brush current density condition, are presented. As results of the test, it is clarified that in case of lower apparent density brushes and lower flexural strength brushes among the natural graphite grades, better dynamic operation characteristics are given.

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.

Technologies for high efficiency large capacity turbine generator

For large capacity turbine generators of thermal power plants, water-cooling system has widely been applied to stator windings. TOSHIBA has developed generators using hydrogen indirectly cooled windings, which are more suitable for high efficiency and easy to maintain, with capacity of 670MVA and efficiency of 99.1%. As the bars of stator windings are cooled with hydrogen gas through the insulation surrounding the bars, it is important to suppress the temperature rise. In this paper, some technologies to realize high efficiency turbine generators, such as multiple parallel circuit winding to reduce current per single bar and ventilation system optimization are described.

Comparison of Brush Contact Drop Characteristics with Copper Ring and Steel Ring, Considering Spark and Collector Ring Hazard

Brush and collector ring system is applied to rotating machines, such as large synchronous generator for thermal and hydraulic power plant and large AC synchronous and wound rotor induction motors for industrial applications. Recently as results of power electronics technology & microcomputer control technology, inverter fed AC adjustable speed large synchronous motor for steel rolling mill and variable speed water turbine generator with AC excitation wound rotor have been developed, realizing excellent performance. In these rotating machines, not only large current capacity but also high performance reliability is required to brush/collector system From these back ground, authors try to introduce new theory to brush/collector system, based upon more than one hundred years of brush/collector ring application histories and based upon some experiments by testing machine, which are introduced by field experiences of those machines.

Effect of reactance saturation on transient and stability for cylindrical synchronous machine

This paper presents the influence of reactance saturation in transient and stability phenomena for cylindrical synchronous machine. For this purpose the authors have examined various equivalent circuit models using electromagnetic transients program (EMTP-ATP).

A study on quadrature equivalent circuit model in large synchronous machine

This paper describes a study on equivalent circuit model in a large synchronous machine. In this study, the authors studied the quadrature axis transient reactance xpsilaq, not only the influence of the operational impedance , but also the difference of transient and dynamic characteristics using finite element method (FEM) and EMTP.

Brush Sliding Contact Voltage Deviation Analysis Based on the Evaluation of Displacement Excited Vibration caused by Collector Ring Profile Distortion -for Turbine Generators & Traction Motors-

When commutator profile distortion in DC motors or collector ring profile distortion in AC generators or motors are caused, stabilities and reliabilities of sliding contact phenomena will be lost, causing mechanical contact instabilities and contact voltage instabilities. In this paper, how to estimate the mechanical vibration out of the ring profile distortion and how to estimate contact voltage deviation out of the mechanical vibration, are introduced.

The world's largest class 8,880MVA short circuit generator

The worlds largest class 8,880 MVA and 1,603 MVA short circuit generators have been manufactured, commissioned and are working successfully. The 8,880 MVA generator, the largest capacity in the world, is for TOSHIBA High Power Laboratory, and the 1,603 MVA generator is for the High Power Testing Laboratory of LG Industrial Systems Co., Ltd of Korea. These generators are power sources for testing of circuit breakers, and can be operated at both 50 and 60 Hz. This paper describes the specification, design concept, key technologies and field test results of these short circuit generators.