Bubbles and Blisters Impact on Diecasting Cage to the Designs and Operations of Line-Start Synchronous Reluctance Motors

This study investigates the starting capability of a high-efficiency synchronous reluctance motor for direct online industrial applications. Because of structural limitations, line-start synchronous reluctance motors (LS-SynRMs) are commonly diecasted by reducing pressure to ensure safe manufacturing. Hence, the shape of the squirrel-cage bars, including bubbles and blisters in the rotors of LS-SynRM, needs to be analyzed. In this paper, three different models are proposed to model the random bubble and blister phenomena by using 2-D finite-element analysis (FEA); their impacts on the flux paths and the change in exciting current of the squirrel-cage bars due to the unbalanced bubbles are thoroughly evaluated. Finally, consider that the bubbles' impacts are confirmed by manufacturing the prototype motor and performing the experiment. The results of FEA and the experiment clearly indicate that the impacts of additional bubbles and blisters need to be considered in the design of LS-SynRMs.