General Analytical Modeling for Magnet Demagnetization in Surface Mounted Permanent Magnet Machines

Abstract

This paper proposes an analytical model for the prediction of airgap magnetic field distribution (MFD) for axial flux permanent magnet (AFPM) machine with partial magnet demagnetization. The AFPM machine geometry is first converted to a polar representation. Consequently, the sub-domain model based on current sheet technique is developed. Then current sheet representation of PM is derived to consider the partial demagnetization using superposition principle. The back electro-magnetic forces and cogging torque are obtained accordingly based on Maxwell's equations. The results show that the results of proposed approach agrees with that of finite element (FE) method. The model is further validated by experiments under both healthy and demagnetized conditions, which can validate the proposed approach. Main contribution of the work is to consider the partial irreversible demagnetization Moreover, the proposed method is applicable for both AFPM and radial flux permanent magnet (RFPM) machine. Index Terms-Axial Flux Permanent Magnet Machine, Demagnetization, Current Sheet Model, Magnetic Field.

The Demagnetization Harmonics Generation Mechanism in Permanent Magnet Machines With Concentrated Windings

“…Modeling techniques [36], [37] have also been proposed for demagnetization and other faults which make it capable of estimating the demagnetization severity locally on the magnet [38] or for various magnet topologies in both radial-axial flux machines [39].…”

Analytical Modeling of Misalignment in Axial Flux Permanent Magnet Machine

“…As expected, it can be seen in that the error comes. In [14], the ratio between the magnet radial thickness and the mean airgap radius is selected as the parameter.…”

“…More detailed information and the curvature can be found in [14], hence, not repeated here. Although the difference is only 4% for AFPM machine in this paper, the correction factor is still need to be applied to the final flux density results in order to achieve higher accuracy, as shown in Fig.…”

Study of a Combined Demagnetization and Eccentricity Fault in an AFPM Synchronous Generator

“…During recent years, the demagnetization and the eccentricity fault have also been studied in the AFPM synchronous machine. More specifically [2,[8][9][10][11][12][13][14][15][16][17][18][19][20][21]] study the eccentricity fault, while [21][22][23][24][25][26][27][28][29][30] investigate the demagnetization fault in AFPM synchronous machines. In [31] a combined eccentricity and demagnetization fault in a double-sided AFPM synchronous machine using a time analytical model is presented.…”