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SUMMARYClawtooth motors have the feature that they can be made thin in the axial direction. This makes them suitable for appliances, automobile accessories, and small-sized industrial motors. On the other hand, there is a need for thinner HEV and elevator motors and large-sized industrial motors. In this study, we examined ways of increasing the output of clawtooth motors. We arrived at the following conclusions.(1) The optimal stator structure was determined and the prospects of attaining the target specification of 123 N-m were determined. (2) Three important manufacturing tasks, assurance of core assembly accuracy, thin coil manufacture, and rotator insertion, were identified.

The results of an experimental study on transient phenomena in a closed cycle disk MHD generator are described in this paper. The transient phenomena were caused by a steplike change of load resistance during testing of the shock‐tube driven disk MHD generator. The load resistance was varied by using an IGBT (insulated gate bipolar transistor) installed in the load circuit. When the load resistance was changed from 0.096 Ω to 2.5 Ω, overshoot of the Hall output voltage and of the Hall electric field was observed, and a large fluctuation of static pressure was also observed. At the same time, a spikelike increase of the cesium recombination continuum and line spectrum appeared just after the load change. The results of quasi‐one‐ dimensional numerical simulation indicate that the observed overshoot was caused by the following phenomena: (1) a steep reduction of the Hall current and a steep increase in both the Faraday current and the electrical conductivity and (2) a slow reduction of the gas velocity due to the enhanced retarding force. Furthermore, the measured spikelike increase of the radiation intensity was ascribed to an increase of electron temperature and electron number density due to a steep increase of Joule heating. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(4): 34–42, 2011; Published online in Wiley Online Library (http://wileyonlinelibrary.com). DOI 10.1002/eej.21004

SUMMARYThe results of an experimental study on transient phenomena in a closed cycle disk MHD generator are described in this paper. The transient phenomena were caused by a steplike change of load resistance during testing of the shock-tube driven disk MHD generator. The load resistance was varied by using an IGBT (insulated gate bipolar transistor) installed in the load circuit. When the load resistance was changed from 0.096 Ω to 2.5 Ω, overshoot of the Hall output voltage and of the Hall electric field was observed, and a large fluctuation of static pressure was also observed. At the same time, a spikelike increase of the cesium recombination continuum and line spectrum appeared just after the load change. The results of quasi-onedimensional numerical simulation indicate that the observed overshoot was caused by the following phenomena: (1) a steep reduction of the Hall current and a steep increase in both the Faraday current and the electrical conductivity and (2) a slow reduction of the gas velocity due to the enhanced retarding force. Furthermore, the measured spikelike increase of the radiation intensity was ascribed to an increase of electron temperature and electron number density due to a steep increase of Joule heating. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(4): 34-42, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com).