Design and field-weakening performance of a synchronous reluctance motor with axially laminated rotor

Axially laminated reluctance motors can be designed to have high saliency and so offer very good performance in terms of torque capacity, power factor and efficiency. This paper presents the design and performance of a 7.5 kW four-pole machine, using thin rotor laminations, which achieved an unsaturated saliency ratio of 12.5. Finite-element analysis is used to predict machine parameters, paying special attention to modeling of the thin rotor elements and to saturation effect on the d axis. Computed parameters are compared with test measurements, showing good agreement. Load tests with 50Hz supply confirm the expected performance characteristics, but also show the occurrence of additional losses associated with the axially laminated rotor construction. A design modification to reduce the extra losses is demonstrated. A detailed investigation of field-weakening performance is reported, showing constant-power characteristics and good agreement between predicted and measured performance over a speed range of 2.25:1 above base speed.