A systematic review on current research and developments on coreless axial‐flux permanent‐magnet machines

Abstract

In recent years, coreless axial-flux permanent-magnet (AFPM) machines have been gaining attention. Being coreless, these machines do not experience eddy current (hence hysteresis losses) and has lower cogging torque leading to higher efficiency. However, limitations such as high leakage flux and weak mechanical structure impede its wide application. The results of a systematic review on coreless AFPM machine research is presented, wherein a total of 123 studies have been selected through the Preferred Reported Items for Systematic Reviews and Meta-Analysis (PRISMA) protocol. About 55% of the articles have been published between 2017 and 2021, indicating recent attention of the researchers on coreless AFPM machines. More than 70% (87 out of 123) of the records have been published by IEEE, which proves the quality and acceptance of the studies. In two-thirds (77 out of 123) of the studies, single-stator double-rotor has been adopted as the machine topology, and in 71.8% (84 out of 123) cases, trapezoidal shape magnets have been used in conventional array. The key research areas on coreless AFPM identified through this review are to produce an efficient design for multiphase and multistage topology and develop lightweight rotor and stator structures.

State-of-the-Art Lightweight Implementation Methods in Electrical Machines

“…Regarding structural lightweight design in the motor active part, some novel motor topologies such as slotless machines [51], ironless or coreless machines [52] have been developed to effectively minimize motor weight while maintaining functionality. Slotless machines are currently being intensively explored due to their reduced weight and enhanced power density, as well as other merits, i.e., zero cogging torque, very smooth rotation, no laminated core loss, and negligible eddy current losses in rotor magnets [53].…”

Trends and Challenges in Electric Vehicle Motor Drivelines - A Review

“…Even though SPMM may be constructed with focused windings to increase CPSR, their use in automobiles is restricted due to the trend toward high torque, high PD machines with decreased magnet content. Interior per-manent magnet (IPM) stators for traction machines can either have focused winding or scattered winding [23]. Concentrated windings feature fewer end turns, which reduces Joule loss and copper loss.…”

A Review of Axial-Flux Permanent-Magnet Motors: Topological Structures, Design, Optimization and Control Techniques

“…Based on the abovementioned information and the literature survey, AFPM motors are important and widely used, and certain progress has been made in key technologies. However, to date, only a few reviews on AFPM motors have been published [7,19,20]. In light of this, we review the research progresses of AFPM motors in this paper.…”