Slotless axial flux hysteresis motor, modelling and performance calculation

Abstract

Hysteresis motors are exciterless and brushless machines with outstanding characteristics such as constant torque and speed, robust structure, low and constant starting current and smooth operation. On the contrary, hysteresis machines have some usage limitations such as low power factor, efficiency and torque density. Comparatively, the low efficiency of common hysteresis motors is mostly related to the parasitic losses generated by the slots. In general, closed or semi-closed slots are employed in the hysteresis machines to reduce the slotting effects and parasitic losses. A new slotless hysteresis motor is introduced. This structure with singular performance is named ‘slotless dual-rotor discs hysteresis motor’ (SDDHM). The capability of being fabricated as a cascade or multi-stack structure, plus the easy manufacturing process and high torque density and efficiency are some advantages of the proposed machine. A field analysis yielding to an equivalent circuit for the steady-state operating condition is presented. All elements of the equivalent circuit are formulated based on design parameters. The simulation of a prototype machine is given and its excellent performance is illustrated. Simulation results are compared with those of the experiment and this validates the proposed model.