This paper focuses on the numerical investigation of low-voltage arc plasma behaviour with the contact opening process included. A flexible experimental setup with a rotating contact is designed to support this study. Based on the magnetohydrodynamic arc model, the elongation and the commutation behaviour of the arc plasma during the contact rotation progress are simulated. Under the given conditions of the external magnetic field and the contact rotating velocity, the arc motion is described in detail by the temperature distribution. The stagnation together with the following rapid jump of two arc roots is observed by both calculation and experiment. The rapid rise in the arc voltage is mainly caused by the increasing difference between the two arc roots displacement in the moving direction, and the jump instant of the arc root on the moving contact is according to the moment of the maximal voltage value.

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To eliminate or reduce torque interruption and driveline jerk for traditional automated manual transmission (AMT), AMT with a gearshift assistant mechanism (GAM) is originally proposed in this paper. The GAM consists of a torque complementary motor and an epicyclic mechanism with a synchronizing clutch. During gear upshift, the electrical motor provides complementary torque to primary (output) shaft after synchronizer discharges, then the synchronizing clutch will work to synchronize primary shaft with anticipated gear. The lockup of the synchronizing clutch will ensure the synchronization of primary shaft and anticipated gear. After finishing synchronizing, synchronizer will lock up the anticipated gear and engine recovers torque supply to finish gearshift. Based on the mathematical model of the proposed transmission, its detailed structure, kinematic character and dynamic behavior are discussed. Controllers are designed to achieve presumed gearshift performance, and simulation results show its effectiveness. Problems may be encountered in engineering application and possible application on electrical vehicle (EV) of the proposed transmission are also discussed. Finally, this paper summarized the merits and further research targets of the proposed transmission, which is a promising structure to achieve swift and smooth gearshift.

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The influence of copper vapor on the low-voltage circuit breaker arcs is studied. A three-dimensional (3-D) magnetohydrodynamics(MHD) model of arc motion under the effect of external magnetic field is built up. By adopting the commercial computational fluid dynamics (CFD) package FLUENT based on control-volume method, the above MHD model is solved. For the mediums of air-1% Cu and air-10% Cu, the distributions of stationary temperature, pressure, electrical potential and the arc motion processes are compared with those of a pure air arc. The copper vapor diffusion process in the arc chamber and the distribution of copper vapor mass concentration are also simulated. The results shows that the copper vapor has a cooling effect on the arc plasma and can decrease the stationary voltage as well. Moreover, the presence of copper vapor can decelerate the arc motion in the quenching chambers. The maximal copper vapor concentration locates behind the arc root because of the existence of a "double vortex" near the electrodes.

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