Synthesis of a Series-Hybrid Permanent-Magnet Variable Flux Motor

This work focuses on synthesizing a series hybrid variable flux permanent magnet motor (SHVFPMM) from a single permanent magnet variable flux motor (VFM) and a rare-earth permanent magnet motor (PMM). Initially, the permanent magnet (PM) sizing process for the standard VFM is presented in terms of loading demagnetization, reversible demagnetization range, demagnetization/re-magnetization currents, average torque and torque ripple. Then, the PMM is investigated mainly in terms of average torque and torque ripple. The outcome of this analysis is then used as the starting point for designing the SHVFPMM. The PM proportions for the SHVFPMM is then analyzed. It is noted that there exists a limited range of PM proportions below which the variable flux PM is demagnetized under load condition and beyond which the torque density does not warrant the excessive increase in the de/remagnetization currents. For validating the proposed synthesis criteria, a 5 hp SHVFPMM is tested experimentally which lies within the derived PM design map.