Bubbles and blisters impact on die-casting cage to the designs and operations of line-start synchronous reluctance motors

This paper includes an investigation of the starting capability of a high efficiency synchronous reluctance motor for direct on-line industrial applications. The approach is to design and optimal of multi-barriers inside rotor to achieve the starting properties of an line start synchronous reluctance motor (LS-SynRM) and the steady-state performance. Using an equivalent circuit on the basis of symmetric field theory, conditions are found for balanced operation at rated conditions and for state/rotor copper loss minimization in the rotor. The optimal model of LS-SynRM is compared and evaluated against a same size induction motor (IM). In addition, the shape of cage bar in LS-SynRM rotor will be analyzed, along with the generated motor torque and loss assessment. As the related die-casting processes on the end-ring and of cage bar achieve desired low rotor resistance, their impacts to the synchronization of LS-SynRM due to bubble/blister during die-casting will also be thoroughly evaluated. Assisted by finite-element analysis (FEM), the results clearly indicated that the rotor slots optimal with die-casting process on the rotor must be introduced for LS-SynRM designs with better steady-state performance and higher efficiency requirements.