Winding Method to Reduce Vibration and Loss Caused by Fractional Slot of Synchronous Machine

Fractional‐slot windings are widely used in rotating machines in order to improve the output voltage waveform, increase the design flexibility, and gain many other advantages. However, fractional‐slot windings are known to produce different harmonic components such as an even order and/or fractional number of space flux harmonics compared to integral‐slot windings. These harmonics may increase stray losses and cause stator core vibration. This paper describes an analysis of space flux harmonics and proposes new winding methods such as “novel interspersed windings” to reduce these harmonic components. The proposed winding methods were verified by numerical analysis and model tests.     

Bearing failure in plain woven C_C composites

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Isolated Ac/Dc Converter Using Soft Switching Technique

This paper presents a high‐frequency isolated ac/dc converter using the soft switching technique. The ac/dc converter consists of a matrix converter for transforming three‐phase ac voltage to high‐frequency ac voltage, a high‐frequency transformer, and an ac/dc rectifier. In order to reduce the switching loss, soft switching at every commutation of the matrix converter and ac/dc converter is achieved. The effectiveness of the proposed converter and the control scheme was verified by experiments.     

Design Method for Improving Motor Efficiency of Switched Reluctance Motor

The motor efficiencies of switched reluctance motors (SRMs) are inferior to those of permanent magnet synchronous motors. This paper describes a design procedure for an SRM to obtain a higher motor efficiency. The first step in the design procedure makes clear the principle for improving the motor efficiency. The cross‐sectional and axial shapes of the rotor and stator cores are designed by magnetic field analysis with the two‐dimensional (2D) and 3D finite element method. A high‐efficiency SRM with 12 stator poles and eight rotor poles is designed. The designed SRM was produced experimentally, and was tested to verify its performance. The motor efficiency was improved in comparison to the standard SRM with six stator poles and four rotor poles.     

A new 200 kV Ω-filter electron microscope

A new 200 kV Ω-filter electron microscope was developed under a project supported by a Grant-in-Aid for Specially Promoted Research of the Ministry of Education, Science, Sports and Culture of Japan. The performance of the microscope is described.     

Optimal control of system with continuous and discrete state variables

An optimization problem for a system composed of continuous and discrete subsystems is considered. The discrete subsystem is introduced to express a combinatorial constraint in conventional control problems. The objective, the state equation and the constraint are assumed linear. The problem is formulated as a mixed-integer linear program with a staircase structure. A feasible decomposition method is developed for obtaining a suboptimal solution to the problem. In applications to an optimal energy control and planning problem for a large-scale production plant, our method uses less computing time than the non-decomposition method.     

Circuit Analysis and Characterization of Contactless Power Transfer System with Variable Impedance

A contactless power transfer system using a repeater coil (repeater Coil topology) has been proposed as a method of suppressing overcurrent without power control during misalignment or no‐load. By installing a repeater coil between the primary and secondary coils, it is possible to increase the input impedance in the case of misalignment of the secondary coil or no‐load condition. In addition, another contactless power transfer system using primary parallel and secondary series resonance capacitors (PS capacitor topology) has been proposed. In the PS capacitor topology, the input impedance can be increased during misalignment of the secondary coil or no‐load condition similar to the repeater coil topology. In this paper, we evaluated the characteristics of both these topologies. First, we conducted a circuit analysis of the repeater coil topology and proposed a design method. In addition, we theoretically clarified the characteristic difference of the two topologies and experimentally evaluated the characteristics.     

Transient Study of Synchronous Machine Field Characteristic

The type of excitation systems mainly used for synchronous generators are the static excitation system and the blushless excitation system. In both cases, it is important to estimate the field characteristic. The authors derived about new knowledge of three‐phase sudden short circuit and mismatched synchronizing using the electromagnetic transients program (ATP‐EMTP). This paper studied these phenomena.