Theoretical performance boundaries for permanent magnet machines as a function of magnet type

The achievable performance of permanent magnet machines as a function of permanent magnet material is an important topic as commonly used rare earth magnets are becoming less available. Machine design is a challenging problem since there are many (~20) degrees of freedom. To compare permanent magnet classes, all of these should be adjusted for a given magnet type. Further, point designs are inadequate to make a comparison, since for any machine there are multiple objectives of interest. This paper presents the theoretically obtainable performance of machines based on four classes of permanent magnet material by formal multi-objective optimization over the full design space to predict the tradeoff between machine mass and loss for each magnet class.