Optimisation of Slot Wedges for 27 kW 100 krpm Axially Laminated Synchronous Reluctance Machine

This paper presents the optimization of semimagnetic wedges in the open slots of an axially laminated synchronous reluctance machine for a micro gas turbine application. The study analyses a high-speed machine (100 krpm) and considers different permeabilities and geometries of the magnetic wedges. In addition, the effects of protrusion of the magnetic wedge inside the air gap are also studied. The use of this approach makes it possible to lower the rotor losses, improve the output power, and raise the machine efficiency. Without semimagnetic wedges, the air gap magnetic field becomes deformed because of the wide open slots, leading to considerable amplitudes of high order spatial harmonics. It is shown that if open slots are equipped with semi-magnetic wedges they can reduce the air gap magnetic field deformation to the same level as with semi-closed slots. Considering that the cooling of high-speed machines, especially, the rotor side in gas turbine applications is challenging, it is essential to investigate creative approaches to reduce losses in these machines.