Line-Start Synchronous Reluctance Motors: Optimized Design for Both Starting Behaviour and Steady State Performances

Line-start synchronous reluctance motors are hybrid motors that simultaneously have the advantages of synchronous reluctance motors (high performance, simple construction, low cost of materials, constant speed at variable load) and induction motors (IM) (mainly the ability to start if supplied directly from the mains). Scientific literature (Gamba et al., International Electric Machines & Drives Conference, Chicago, 648–655, 2013) has widely affirmed that these types of motors, although requiring less quantities of active material (magnetic lamination, copper wire, die-cast aluminium) to obtain the same efficiency class (for example IE3 or IE4) of induction motors, have reduced performance in the start-up phase, and especially in the critical synchronization phase. In particular, with the same load torque, the synchronization capability decreases with the increase in the load inertia. This new design is therefore focused on minimizing this weak point, thus obtaining a series of motors that can be usefully put on the market for most of the applications to replace induction motors. The presentation of the experimental test results on prototypes confirmed the very great potentials of the calculations, and they were strategic in the decision to place these motors in the market and start-up their series production.