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To address the issues of the insufficient output torque associated with the application of intensifying-flux permanent magnet (PM) machines in electric vehicles, this paper aims to propose an intensifying-flux hybrid excitation PM machine. It is possible to adjust the air gap magnetic field by adjusting the field current in the excitation winding, thereby increasing the torque output capability and speed range of the machine.

First, a novel intensifying-flux hybrid excited permanent magnet synchronous machine (IF-HEPMSM) is proposed on the basis of intensifying-flux permanent magnet synchronous machine (IF-PMSM) and an equivalent magnetic circuit model is established. Second, the tooth width and yoke thickness of the machine stator are optimized to ensure the overload capacity of the machine while effectively improving the wide flux regulation range. Furthermore, the electromagnetic characteristics of the IF-HEPMSM are investigated and compared with the IF-PMSM and conventional permanent magnet synchronous machine (PMSM) by using finite element simulations.

The i_d of IF-HEPMSM and IF-PMSM is greater than zero low-speed magnetizing current. And the flux-weakening current of the IF-HEPMSM is 18% and 3% smaller than of the conventional PMSM and IF-PMSM.

Aiming at the problems of IF-PMSM applied to electric vehicles, this paper proposes an IF-HEPMSM. The air gap magnetic field is adjusted by controlling the current of the excitation winding to improve the reliability of the machine. Therefore, the IF-HEPMSM combines the advantages of high-power density and high efficiency of the PMSM and the controllable magnetic field of the electro-excitation machine, which is of great engineering value when applied in the field of electric vehicles.

The proposed IF-HEPMSM offers better flux regulation capability with electromagnetic characteristics analysis and maps of dq-axis current as compared to IF-PMSM and conventional PMSM. Moreover, the improvement of the torque can make up for the shortcomings of the insufficient torque output capability of the IF-PMSM.

The rail transport sector in China represents one of the largest consumers of energy today, and the primary purpose of this paper is to examine the causes of changes in energy consumption of Chinese national rail transport (ECCNRT).

For this study, reasonable indicators as factors that affected conversion volume (CV) and unit energy consumption (UEC) based on statistical data from 1990 to 2010 were selected. CV and UEC models were established by regression analysis and tested using real data of 2011-2014. The CV model indicates it has an exponential relationship with GDP. Besides, there is a quantitative relationship between UEC and the quantity of locomotives. The ECCNRT calculation model was proposed and ECCNRT model data were compared with the real data. Impacts of different factors on ECCNRT were analyzed with economic principles.

The analysis conducted shows that the calculation model can reflect variation of ECCNRT precisely, and ECCNRT has a quantitative relation with GDP and quantities of locomotives. GDP accounts for changes of ECCNRT 20.02 per cent, while those for quantity of diesel locomotives and electric locomotives are 26.87 and 53.11 per cent, respectively. The number of electric locomotives is the main factor that influences variation of ECCNRT.

Through regression analysis, this study discovered the inner quantitative relationship between the conversion volume (important index of Chinese national rail transport production) and GDP. In addition, this study establishes the ECCNRT model according to the Chinese national rail transport data, which can be used to calculate the amount of ECCNRT and conduct quantitative analysis for different impacts of various factors on ECCNRT’s changes.