Outer and Inner Rotor Line-Start Permanent-Magnet Synchronous Motors: An Electromagnetic and Thermal Comparison Study

This paper presents an electromagnetic and thermal comparison study between an outer and inner radialflux line-start permanent-magnet synchronous motor (ORFLSPMSM and IRF-LSPMSM). The LSPMSM proposed design is extracted from existing sizing equations for induction motors (IMs) and permanent magnet motors (PMMs). A 4-kW commercial induction motor is adapted as the benchmark in this study with the aim of improving the machine efficiency by replacing the IM rotor with a hybrid rotor of the same frame size. Finite-element analysis is used to compare electromagnetic performance such as start-up capability and steady-state performance of the motors. In addition, an analytical thermal model is proposed based on a lumped-parameter thermal network to analyze thermal behavior of the two motors. This is validated using 3D FEM-based thermal analysis. Electromagnetic and thermal simulation results show that the 4-kW IRF-LSPMSM has approximately 4% higher efficiency than the ORF-LSPMSM and 5% than baseline IM and its steady state operational temperature rise is approximately half of that the ORF-LSPMSM and benchmark IM.