The turn-to-turn faults (TTF) are also inevitable in split-winding transformers. The distorted leakage field generated by the TTF current results in large axial forces and end thrusts in the fault windings as well as affecting other branch windings normal operation, so it is of significance to study TTF of split-winding transformers. In this paper, the characteristics analysis of the split-winding transformer under the TTFs of the low voltage winding at different positions are presented. A 3600 KVA four split-windings transformer is taken as an example. Then, a simplified three-dimensional simplified model is established, taking into account the forces of the per-turn coil. The nonlinear-transient field-circuit coupled finite element method is used for the model. The leakage field distribution under the TTFs of the low voltage winding at different positions is studied. The resultant force of the short-circuit winding and the force of the per-turn coil are obtained. Subsequently, the force and current relationship between the branch windings are analyzed. The results show that the TTF at the specific location has a great influence on the axial windings on the same core, and the distorted leakage magnetic field will cause excessive axial force and end thrust of the normal and short-circuit windings. These results can provide a basis for the short-circuit design of split-winding transformer.

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High-speed surface-mounted permanent magnet synchronous machine is often used in micro gas turbine generation system due to its high rotor strength and high efficiency. The electrical machine in this kind of generation system needs to integrate two functions of starter and generator. Therefore, its comprehensive performance, including starting performance and generating performance, has become a comprehensive standard to measure machine performance. In this paper, a 40 kW, 20,000 r/min high-speed machine is taken as an example, the influence of magnets magnetization direction on the machine comprehensive performance is studied. The machine models with different magnets magnetization directions are established by using finite element method and the correctness of the models is verified by comparing the experimental data with the finite element calculation data. On this basis, the influence of different magnetization directions on the performance of the machine, such as generation loss, torque ripple, output voltage, start-up time and maximum starting ability, is analyzed. Furthermore, based on the Fourier decomposition of air gap flux density and the decoupling analysis of starting torque, the influence mechanism of magnetization direction on the performance of the machine is revealed. The presented results provide a reference for the selection of a suitable magnetization direction for high-speed surface-mounted permanent magnet machines.

The progressive trend towards intelligent, eco-friendly, low-carbon, and sustainable development in contemporary industrial logistics parks has catalyzed a substantial influx of new energy power systems. This integration poses unique challenges, including intermittent and fluctuating load characteristics, due to the operation of high-powered machinery such as belt conveyors. Consequently, traditional distribution transformers often face premature failure, attributed primarily to inadequate overload capacity, thereby compromising grid safety. Evaporative cooling technology, as a countermeasure to these thermal constraints, holds the potential to enhance the heat dissipation capacity, thus mitigating overload issues. This study employs a novel methodological blend of thermal circuit parameter analysis and empirical experimentation to comprehensively investigate the performance attributes of evaporative cooling distribution transformers. This study's innovative approach involves the development of a dynamic piecewise thermal circuit model that encapsulates both the natural convection and nucleate boiling heat transfer stages. This model builds on the intrinsic attributes of the pool boiling curve of a lowboiling-point coolant. Critical aspects under scrutiny include thermal circuit parameters, boiling heat transfer correlations, constraints on critical heat flux density, and characteristics of the evaporative coolant. Following the Rohsenow correlation and model experimentation, a suitable boiling heat transfer correlation for the selected evaporative coolant was formulated. The thermal circuit model was then employed to discern the influence of the load coefficient, ambient temperature, and coolant boiling point on the operational behavior of the evaporative cooling transformer. The analysis revealed that evaporative cooling transformers exhibit a commendable aptitude for handling impact, intermittent, and fluctuating loads, demonstrating substantial overload resistance. Hence, they are favorably poised for extensive application in heavy-load industrial logistics parks, especially those harnessing new energy. These findings provide instrumental insights, potentially propelling advancements in the modern industrial logistics landscape.

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