Considerations on Iron Nitride Enabled Rare Earth Free Hybrid Variable Flux Machines

A potential analysis for the application of iron nitride magnets in (hybrid) variable flux machines ((H)VFM) is presented, investigating the possibility to design rare earth free machines using ferrite and iron nitride magnets. A review on variable flux machine research is given to contextualize the presented work. Delta topology machines with different magnet combinations are simulated using design of experiments. The magnetization characteristics of the machines are investigated by directly deriving the magnetic fields in the machines’ permanent magnets from the vector potential in the single mesh elements. Series HVFM machines using magnet alloys with strongly different remnant magnetization are discussed. The performance of different (H)VFM is compared with regard to their ability to demagnetize, the demagnetization characteristics in the torque-speed plane and the overall performance. Series HVFM with iron nitride and ferrite magnets are challenging due to demagnetization of the iron nitride magnets.