Multi three-phase machines are frequently recommended for high current and high power applications due to their ability to minimize phase current while maintaining rated power and phase voltage. Furthermore, multi three-phase machines are also proposed because of their fault-tolerant capability to operate in partial working conditions due to their redundant structure. A partial working condition may occur when one or more three-phase winding sets go into faulty condition. This article focuses on evaluating the thermal behavior and efficiency of a multi three-phase machine comprising different modular winding topologies to investigate its normal, partial, and partially overloaded operation. The machine prototype used in the analysis is an interior permanent magnet synchronous machine (IPMSM) having six three-phase winding sets configured in modular three-phase winding arrangements. Firstly, the prototype machine's losses, efficiency, and output torque performances are evaluated through electromagnetic finite element analysis (FEA) for the different modular three-phase winding topologies applying similar operating conditions. Then the machine's thermal behavior is evaluated for the modular (concentrated, distributed, and combined concentrated and distributed) three-phase winding topologies through a coupled magnetic field and thermal analyses under the machine's healthy, partial, and partially overload operations. Finally, a comparative thermal analysis is presented for the machine prototype along with experimental validations for the analyzed modular three-phase windings topologies. This research study suggests the best modular threephase winding topology for a multi three-phase machine considering efficiency performance and mutual heat exchange phenomenon between different three-phase independent winding sets, particularly for the machine's partial and partially over-load working conditions.INDEX TERMS Winding topologies, thermal analysis, cooling, fault-tolerance, lumped parameter thermal network, sensitivity analysis.
Ferritic steels are important cladding and structural material for current and advanced reactors containing Fe as a primary compositional matrix element. Three proposed models containing voids, impurity P, and nano oxides embedded in Fe were simulated using molecular dynamics code LAMMPS. The interaction mechanism of dislocation for each model was observed and compared by analyzing its strengthening effect through the stress-strain curve. In considering the interaction of dislocation with voids, it was observed that for all void sizes, dislocation bypass voids following orowan unpinning mechanism without any loop irrespective of any radii, while for P clusters, dislocation is trapped at the interface and leaves it after making a screw dipole shape following orowan mechanism. Moreover, the oxide dislocation interaction in oxide dispersed in iron follow the orowan unpinning mechanism accompanied by loops around oxide. The values of critical unpinning stress for all models were analyzed and compared. Atomic insights on the interaction mechanism indicate that the interaction mechanism is essentially the same for void and a P cluster in Fe i.e. orowan unpinning mechanism. The presence of oxide in Fe matrix during its interaction follows the orowan unpinning mechanism along with a dislocation loop around the oxide and its area is proportional to the size of the oxide. The critical unpinning stress was compared and analyzed for each model.
This work will provide a unique and valuable insight into the strengthening mechanism due to dispersed oxides by providing new parameters for the multi-scale simulation. Our results demonstrate that oxide impedes dislocations and offers hindrance for edge dislocations to saturate further. Furthermore, our simulation results provide atomic insight into the onset of plasticity in iron alloys.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.