Flux Loss in Permanent Magnets and its Prediction

Abstract

　Permanent magnets are used for generating magnetic flux without consumption of energy in electrical machines. The flux from a magnet decreases by exposure(s) to elevated temperatures and/or magnetic fields. It also decreases over time. This phenomenon is called “flux loss”. In this contribution, the mechanism of flux loss is explained, and the relationship between flux loss and basic magnetic properties of a magnet is clarified. Subsequently, the prediction method of flux loss is discussed from the viewpoint of basic magnetic properties. Finally, examples of prediction of flux loss using the finite element method are shown for multi-pole ring magnets placed in free space and in a motor.