In this paper, hard magnetic materials for future use in electrical machines are discussed. Commercialized permanent magnets used today are presented and new magnets are reviewed shortly. Specifically, the magnetic MnAl compound is investigated as a potential material for future generator designs. Experimental results of synthesized MnAl, carbon-doped MnAl and calculated values for MnAl are compared regarding their energy products. The results show that the experimental energy products are far from the theoretically calculated values with ideal conditions due to microstructure-related reasons. The performance of MnAl in a future permanent magnet (PM) generator is investigated with COMSOL, assuming ideal conditions. Simplifications, such as using an ideal hysteresis loop based on measured and calculated saturation magnetization values were done for the COMSOL simulation. The results are compared to those for a ferrite magnet and an NdFeB magnet. For an ideal MnAl hysteresis loop, it would be possible to replace ferrite with MnAl, with a reduced weight compared to ferrite. In conclusion, future work for simulations with assumptions and results closer to reality is suggested.

In this paper a method of dynamic modelling of nonlinear permanent magnets (PMs) with recoil lines in 2D finite element analysis (FEA) software was presented. COMSOL Multiphysics® 6.0 FEA software was used in this study. The method is implemented through the variable utilities. Simulation results of a spoke-type synchronous generator for a wind turbine with anisotropic Alnico 5, 8B and 9 grades were used to exemplify the model and compared. The proposed methodology can be used for the simulation of nonlinear permanent magnets with recoil lines and includes reversible and irreversible losses of magnetization of nonlinear permanent magnets. The effect of the magnetic field from the stator winding on nonlinear permanent magnets during normal operation and short circuit was studied. Modelling results were compared to the model without any demagnetization and to a previous study with recoil lines and averaged minimum magnetic flux points. The no-load voltages were compared before and after a demagnetization. The dynamic model showed considerable demagnetization of Alnico magnets during normal operational and three-phase short circuit. Alnico 5 and 9 showed higher sensitivity to short circuit currents and the short circuit currents caused remagnetization of the upper part of the magnet in the opposite direction. The anisotropy of the permanent magnet implemented in the model improved the magnetic field simulation inside the magnet and partially protected the magnet from demagnetization by inclined fields. Lastly, the method was experimentally verified by tests on an iron core.