This paper investigates the transient synchronization performance of a line-start permanent magnet synchronous machine (LS PMSM) taking into account the effect of the rotor cage slot design, active permanent magnet volume and load inertia. First the transient performances of a rotor cage with different slot profiles and the same cross sectional area are evaluated. The design optimization of LS PMSM with a selected rotor slot shape is then conducted by employing an adapted multi-step Taguchi method. The aim of the optimization is to improve transient performance. In addition, the optimized rotor design is subjected to further sensitivity analysis by exposing the design to various noise factors such as the system's moment of inertia and permanent magnet volume. This is to check the robustness of the design. Finally, results are discussed and relevant conclusions are drawn.