Chikara Kaido

In-plane eddy current analysis for end and interior stator core packets of turbine generators

This paper describes analyses of in-plane eddy currents, which are generated by the perpendicular flux at both of end and interior stator core packets of turbine generators. The 3-D finite element method considering lamination of the electrical steel sheets is applied to the calculation. The validity of the analysis is examined by a simple apparatus that simulates the stator core of the turbine generator. It is clarified that the in-plane eddy currents are generated not only at the end stator packets, but also at the interior packet due to the duct space. It is also clarified that the in-plane eddy current loss decreases as nearly half by the slits of the stator teeth.

Spiral core made of grain-oriented electrical steel sheet

Spiral cores made of grain-oriented electrical steel sheets (GO) were developed to be used as a high performance motor core. All teeth directions are coincident with the GO rolling directions (easy magnetization axis) in the spiral cores. The GO spiral cores have excellent properties because the GO has very low iron loss and very high permeability in the rolling direction. In the GO spiral cores, the iron losses decrease to a quarter and the inductions are 0.2 T higher at 800 A/m as compared with conventional spiral cores made usually of SPCC. Because the thickness of conventional spiral cores generally varies, applications are limited to automobile alternator cores. The thickness of GO spiral cores changes little during a spiral deformation because the core sheets are deformed transversely to the rolling direction of GO, that is, {011}; the {011} deformation of Fe does not create sheet thickness. As the stiffness and packing factor of a GO spiral core are high in the order of no thickness change, GO spiral cores have high performance for motor cores.

In‐plane eddy current analysis for end and interior stator core packets of turbine generators

Purpose – The purpose of this paper is to investigate the distribution of in‐plane eddy currents in stator core packets of turbine generators, and to reveal the loss reduction effect by the slits in the stator teeth.Design/methodology/approach – The in‐plane eddy currents are calculated by a 3D finite element method that considers lamination of electrical steel sheets. First, this method is applied to a simple model that simulates the stator core of the turbine generators. The calculated losses are compared with the measured losses in order to confirm the validity. Next, the same method is applied to a 250 MVA class turbine generator.Findings – The validity of the calculation method is confirmed by the measurement of the simple model. By applying this method to the turbine generator, it is clarified that the considerable in‐plane eddy currents are generated not only at the end stator packets, but also at the top of the teeth of the interior packets due to the duct space. It is also clarified that the in‐p...

Fundamental Study of Motor with Transformer Function

In a motor with transformer function (MTF), where a magnetic core is used jointly as a motor core and a transformer core, the interactions between motor action and transformer one are investigeted in noload conditions. If flux densities are not saturated and magnetic circuits are balanced in the magnetic core, the characteristics of motor actions and those of transformer actions are almost independent each other. In motor actions, torques and iron losses are almost constant at frequencies different from transformer frequency, although they fluctuate at the same frequency. In transformer actions, exciting currents and iron losses increase although the increases are small at frequencies different from motor frequency. Thus a MTF drives almost individuals as a motor and a transformer in the same time.

The Properties of Laminated and Plane-Welded Electrical Steel

A laminated and plane-welded electrical steel (LPW) is made in the way that laminated electrical steel sheets plated with Cu and/or Sn are heated in order to fuse the plated Cu andSn, weld the sheets at the surfaces and then combined them together. The LPW has a higher permeability than usual electrical steel plates and a higher electric conductivity than laminated electrical steel sheets. The mechanical strength of LPW is as high as those of electrical steel plates. The 2-dimensionally free shape of LPW is made by punching before welding the sheets at the surfaces. If LPW is used in a voice coil motor (VCM). the size of VCM is small, and the characteristcs of VCM are more improved if the LPW is made of grain-oriented electrcal steels and the easy axises are arranged along the magnetic path of VCM.