Design optimisation of an axially laminated synchronous reluctance motor

The rotor saliency of the axially laminated synchronous reluctance motor (SynRM) produces a square airgap flux density distribution. If a square current distribution interacts with this flux the SynRM generates its optimal torque. This paper extends previous work on the magnetic modelling of the SynRM. A design model is proposed which incorporates all rotor and stator dimensions. Saturation effects have also been included in the model. The key dimensions affecting SynRM performance are identified as rotor radius, rotor pole pitch, rotor steel:steel+fibre ratio, airgap, stator current density and stator slot opening. An iterative algorithm is determined for the design optimisation process. This algorithm is simple enough to be implemented in a spreadsheet environment. The model is used to design a 5 kW motor with an optimal torque/unit mass ratio. The designed motor has a nine phase concentrated winding to approximate the ideal square current excitation. Finite element analysis and a static load test on the constructed machine confirm the model´s predictions. In addition, optimal values for the key motor dimensions, over a range of motor sizes, are determined and discussed