Design of Multilayer Concentric Ferrite-Magnet Machines for a Traction Application

This article proposes two different interior permanent magnet (IPM) motor-generator designs for a hybrid electric vehicle application. The article shows the tradeoffs, merits, and demerits of two feasible designs of ferrite-magnet machines for such an application. Both designs use multilayer concentric ferrite magnets. They use different winding topologies: 48-slot 8-pole (48/8) integral-slot and 60/8 fractional-slot topologies. The width, length, and location of the embedded rotor magnets, in addition to the shape of the flux barriers, are optimized to achieve the required performance within the given constraints. The torque ripple of both designs is kept below 5% at the base-speed operating point without applying skewing. The electromagnetic performance characteristics of both designs at the base- and maximum-speed operating points are presented. The efficiency maps of both designs throughout the entire speed range are also investigated. Moreover, this article presents an irreversible demagnetization analysis of the utilized ferrite magnets at different operating conditions. Spin analysis is performed to study the structural integrity of the proposed designs. Experimental results of both machines are provided for validation.