Linear Recoil Curve Demagnetization Models for Rare-Earth Magnets in Electrical Machines

A bstract-Rare-earth-permanent-magnet excitation can provide considerable improvement in the energy efficiency of electrical machines. Tolerating motor terminal short circuit and avoiding magnet irreversible demagnetization must be studied during the design and prototyping stage of a permanent-magnet motor. Electrical machinery design increasingly relies on the finite element analysis (FEA), where the various interpretations of the linear recoil curve concept are the prevalent tools to assess magnet's demagnetization. This study uses vibrating sample magnetometer to observe the hysteresis behavior of two distinct commercially available NdFeB magnet grades. The measured data are used to study the forecasting ability of the linear-recoil-curve-concept-based models: linear sloped, exponential, hyperbolic tangent function, and two spline models with fixed and changing permeability. The results indicate that none of the considered approaches is universal. Nevertheless, the appropriately chosen interpretation of the linear recoil curve concept may offer a relatively accurate tool for the simulation of a rare-earth permanent magnet in an electrical machine.