[Objective] To enhance the torque density of permanent magnet adjustable speed drive (PMASD)

this paper proposes a composite flux PMASD with squirrel-cage structure

and conducts its electromagnetic design and electromagnetic characteristic analysis. [Methods] Firstly

a brief introduction to the structure and principle of the proposed PMASD was provided

and the theoretical model of PMASD was established based on the equivalent magnetic circuit method. Secondly

the PMASD simulation model was established based on the finite element method. The influence of key structural parameters such as the pole-arc coefficient

thickness and the pole-pairs of permanent magnets on the air-gap magnetic field

torque and torque ripple of the PMASD were studied. And the influence of the cross-sectional area of L-shaped conductor on the loss and torque characteristics of the PMASD were also analyzed. Finally

the torque characteristic and speed regulation characteristic at different shifting distances of the squirrel-cage rotor were analyzed. [Results] When the pole-arc coefficient was 0.8

the air gap flux density waveform of the PMASD was closer to a sine wave

and the torque ripple was relatively small. As the thickness of the permanent magnet increases

the amplitude of the fundamental wave of the air gap flux density was increased

with the growth rate gradually decreasing. A reasonable combination of permanent magnet thickness and pole-arc coefficient could improve the fundamental wave proportion. As the number of pole-pairs increased

within the low slip speed range

the PMASD torque output capacity was first enhanced and then decreased. Meanwhile

the slip speed corresponding to the maximum torque showed a trend of first increasing and then decreasing. As the cross-sectional area of the conductor bar increased

the resistance of the conductor bar was reduced

and the copper loss of the squirrel-cage rotor was decreased. With the increased of shifting distances

the torque and copper loss were generally reduced

but the reduction rate was gradually decreased. [Conclusion] The proposed composite flux squirrel-cage structure enhances the torque output capability and torque density of the PMASD

offering excellent speed regulation characteristics and thermal conductivity.