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.     

High‐Response Torque Control of IPMSM Based on a New Coordinate System Suitable for Voltage Amplitude and Phase Control

This paper proposes a torque control method for interior permanent magnetic synchronous motors (IPMSMs). The proposed method controls the voltage amplitude and phase based on a new n–t coordinate system. The t‐axis is a tangent line of a constant voltage ellipse, and the n‐axis is a normal line of the ellipse. On the n–t coordinate system, the n‐axis current is not affected by the voltage phase. The n‐axis current is utilized to reduce the mutual coupling between the voltage amplitude controller and phase controller. The proposed method realizes a high torque response for the linear range and overmodulation range of the inverter, including six‐step mode. The effectiveness of the proposed method was verified by simulation and experimental results.     

Study on Acceleration Factor at 5000 h Multiple Stress Test and Aging Evaluation of EVA Insulator

The authors carried out an outdoor exposure test and the 5000 h multiple stress test to ethylene vinyl acetate (EVA) polymer composite insulator used for 22 kV distribution line and an attempt was made to estimate the acceleration factor of the 5000‐h multiple stress test corresponding to the climate condition of the Kyushu area. By comparing dry band arc cumulative charge of leakage current at 5000‐h multiple stress test with that in the outdoor exposure test, the authors estimated the acceleration factor of the 5000‐h multiple stress test to be about 20 times. The acceleration factor was found to almost agree with the evaluation result of the absorption of hydroxyl group by FT‐IR analysis and the surface roughness of the insulator, respectively. Finally, for the electrical property, the expected life of EVA insulator that the authors developed was confirmed to be more than 40 years.     

Sintering of ZnS with a Small Amount of Ba2ZnS3

The effects of alkali and alkali-earth chloride additives on the sintering of ZnS powder compacts in H₂S have been examined. BaCl₂ was found to promote the sintering of ZnS. BaCl₂ reacts with ZnS to form Ba₂ZnS₃, which acts as a flux for sintering.     

PALATAL PRESSURE PATTERNS OF GELATIN GELS IN THE MOUTH

Palatal pressures of gelatin gel at various concentrations were detected by pressure transducers set at three locations in the palate. The following parameters were derived from the palatal pressure patterns: P, mean of palatal pressure from the beginning of eating to the end of swallowing; S, the last pulse of swallowing; T, retaining time of the sample in the mouth and W, energy consumed in the course of time until swallowing. P and W increased as the gelatin concentration increased from 1.0–4.0% and then they decreased as the gelatin concentrations exceeded 4.0%. T increased linearly over the whole range of gelatin concentrations. Changes in gelatin concentration had little effect on S. It was concluded that oral action changed primarily from crushing by the tongue against the palate to biting by the teeth as the toughness of the gelatin gel increased.