Advantages and Characteristic Analysis of Slotless Rotary PM Machines in Comparison With Conventional Laminated Design Using Statistical Technique

Slotless permanent magnet (PM) machines have been the considerable research subject for electric vehicles application due to their obvious merits. As opposed to conventional laminated PM machines, such machines can offer zero cogging torque, sinusoidal torque curve angle yielding a machine with very smooth rotation, no laminated core loss, and negligible eddy current losses in rotor magnets. This paper presents the mathematical model and the characteristics analysis of slotless rotary PM machines compared to a conventional laminated design. An explicit analytical expression of slotless rotary machines is developed to calculate the electromagnetic torque on both the q- and d-axis current injections. The validity of an analytical calculation is confirmed by the finite element analysis. Subsequently, the performance comparisons of slotless and laminated designs are carried out using a statistical technique. The key results derived from the comparative study are expected to be a useful reference resource for decision makers who should make a comparative judgment.