Design issues of an IPM motor for EPS

In electric power steering (EPS), permanent magnet (PM) brushless ac (BLAC) motors offer distinct advantages over other electric motor types in terms torque smoothness, reliability and efficiency. The design procedure of an interior permanent magnet (IPM) motor used in EPS is presented in this paper. The requirements of the steering system are first introduced, and the machine's specifications are then derived. Critical issues which have considerable impacts on the machine's performance, such as operation mode, rotor structure and slot/ pole combination, are analyzed. Subsequently, a 12-slot/10-pole sinusoidally excited IPM machine with concentrated windings is proposed and optimized based on finite element analysis (FEA) modelling. The losses and efficiency are then computed. Performance predictions from the FEA results confirm all the requirements are met or exceeded. A prototype motor has been built for validation

Simulation of heat and water transfer in a surface irrigated, cropped sandy soil

Field experiments were conducted to validate a one-dimensional numerical Simple Soil Plant Atmospheric Transfer (SiSPAT) model that simulates heat and water transfer through the root zone of a surface irrigated, cropped sandy soil. The model accounts for the dominant processes involved in water and heat transfer in a cropped soil. Model validation used field experimental data from 2004 and suggested that the SiSPAT model could be successfully applied to predict soil water and temperature dynamics of a cropped soil in experimental conditions. Validation resulted in high values of model efficiency (ME), and low values of root mean square deviation (RMSD) and mean bias error (MBE) between the simulated and measured values. Model predictions were obtained using field experimental data from 2005 and showed that the SiSPAT model reproduced reasonably well the experimental distributions of soil moisture and temperature. Minor discrepancies between the predicted and measured data during the prediction period can probably be attributed to the uncertainties in soil water content and soil temperature probe measurements. In addition, the influence of irrigation water temperature on water and heat transfer was ignored in the model. This could have contributed to deviations between the simulated and measured values during the experiment. Prediction results indicated that the variability of the water and heat transfer fluxes following a surface irrigation in different stages of the crop (wheat) growth season resulted from the difference in net radiation reaching the cropped soil due to the varying shielding factor as controlled by leaf area index (LAI), root water uptake, meteorological conditions and soil water regime. Furthermore, an interaction between water and heat transfer through the root zone in the cropped soil could be observed during the prediction period.Soil temperature Moisture dynamics Wheat Sandy soil Small level-basin irrigation