Geometry of Line Start Synchronous Motors Suitable for Various Pole Combinations

Line start synchronous motors (LSSM) have been recently introduced in the motor market to meet new efficiency class requirements. They exhibit high efficiency and power factor compared with induction motors. On the other hand, the difficult design, manufacture, and high cost due to the presence of permanent magnets limit their widespread use in the market. Another key factor that limits the LSSM diffusion is the need of having a wide variety of different laminations of different sizes, increasing the number of pieces to be stored, the number of mold geometries, etc. This paper investigates the opportunity to use a proper geometry of LSSM that allows the same stator and rotor laminations to be used for a different number of poles. From the manufacturing point of view, the adoption of a unique rotor lamination is extremely advantageous. It is shown that satisfactory performance can be achieved rearranging the stator winding according to the number of poles. Experimental measurements are carried out on an LSSM prototype in which the same lamination is used for 2-pole and 4-pole machines.