Abstract Stator core is one of the parts in the magnetic circuit, which playing an important role in the performance of the electric machine. Commonly the non-oriented electrical steel laminations are assembled into a stator stack by welding to meet the demand of strength at high-speed rotation. However, the effects of residual stress, microstructure change and inter-conduction among laminations introduced during welding process result in a great deterioration in magnetic properties of stator core. The pulsed laser welding of ultra-thin electrical steel laminations is adopted to decrease the iron loss while ensuring sufficient strength simultaneously. As two important indicators of the stator core, peak load after welding determines the maximum load torque and iron loss affects the energy conversion efficiency. There is currently no model that can accurately predict peak load and iron loss of the stator core after pulsed laser welding, and the influence of peak power and duty cycle on peak load and iron loss also needs to be further studied. In this paper, the peak load of stator core is studied based on the tensile test of a novel rectangular specimen which has the same stress state with the ring ones subjected to torsional load. An empirical model of peak load is proposed by the two-step fitting method considering the effect of peak power and duty cycle. Then an analytical model of iron loss of welded laminations is developed considering eddy current circuit in weld seam caused by damage of insulation coating. All peak load and iron loss models with small relative errors can obtain accurate prediction results. Finally, the weld lobe for pulsed laser welding is drawn, whose left and right boundaries are determined by peak load and iron loss, respectively. By selecting the appropriate process parameters, iron loss of the stator core using pulsed laser welding decreases, compared with traditional continuous laser welding.

中文翻译：

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层压电工钢的脉冲激光焊接

摘要 定子铁芯是磁路中的重要部件之一，对电机的性能起着重要的作用。通常将无取向电工钢叠片通过焊接组装成定子叠片，以满足高速旋转时的强度要求。然而，焊接过程中引入的残余应力、微观结构变化和叠片间的相互传导的影响导致定子铁芯磁性能的极大劣化。采用脉冲激光焊接超薄电工钢叠片，在保证足够强度的同时，降低铁损。作为定子铁芯的两个重要指标，焊后峰值负载决定了最大负载转矩，铁损影响能量转换效率。目前还没有模型可以准确预测脉冲激光焊接后定子铁芯的峰值负载和铁损，峰值功率和占空比对峰值负载和铁损的影响还需要进一步研究。在本文中，基于一种新型矩形试件的拉伸试验，研究了定子铁芯的峰值载荷，该试件与受扭转载荷的环形试件具有相同的应力状态。考虑峰值功率和占空比的影响，通过两步拟合方法提出了峰值负载的经验模型。然后建立了考虑绝缘涂层损坏引起的焊缝涡流回路的焊接叠片铁损分析模型。所有相对误差较小的峰值负荷和铁损模型都可以获得准确的预测结果。最后，绘制脉冲激光焊接的焊瓣，其左右边界分别由峰值载荷和铁损决定。通过选择合适的工艺参数，与传统的连续激光焊接相比，使用脉冲激光焊接的定子铁芯铁损有所降低。