Design of Iron-Nitride-Based Permanent Magnet Variable Flux Motors

This work investigates the application of an Iron-Nitride (FeN) Permanent Magnet (PM) material to variable flux motors (VFMs). Two existing VFMs are used as references, a rareearth-free inverted saliency VFM and a series hybrid VFM. Initially, the inverted saliency VFM performance is evaluated for equal usage of PM material. Then, the PMs are resized for achieving similar electromagnetic performance to the reference VFM. It is noted that although the new PM has 25% higher residual flux density than AlNiCo9 PM, it requires high current for remagnetization. However, adopting the FeN magnet to the inverted saliency machine can allow reducing the PM usage by 42% and hence reduced rotor weight would be expected. By replacing the rare-earth magnet of the series hybrid VFM with FeN, comparable constant torque performance is attained with the advantage of avoiding rare-earth magnet demagnetization risks. This shows that for the investigated torque density levels, the FeN magnet has a high potential for designing existing/upcoming regular and hybrid magnet VFMs.